JP7135840B2 - Positive electrode and lithium ion secondary battery - Google Patents

Description

The present invention relates to positive electrodes and lithium ion secondary batteries.

In recent years, with the rapid progress of portable and cordless home appliances, non-aqueous electrolyte secondary batteries have been put to practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. This non-aqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. As a positive electrode active material used for the positive electrode, lithium cobaltate (LiCoO ₂ ) has been actively researched and developed. , many proposals have been made.

For example, in a lithium secondary battery comprising a positive electrode using a lithium-transition metal composite oxide as an active material, BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O ₃ , CeO ₂ , As A lithium secondary battery has been proposed in which a coating film made of ₂ O ₃ or a mixture of two or more thereof is formed (see, for example, Patent Document 1).

Further, in a battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt and capable of being reversibly charged and discharged multiple times, Ti, Al, Sn, Bi, Cu, Si, Ga, W, A positive electrode characterized by using a metal containing at least one selected from Zr, B, and Mo and/or an intermetallic compound obtained by combining a plurality of these, and/or a positive electrode coated with an oxide. A battery using such a material has been proposed (see, for example, Patent Document 2).

On the other hand, non-aqueous electrolyte secondary batteries using lithium cobaltate as the positive electrode active material have a limit in terms of capacity (currently, the limit is 140 mAh / g or less), and cobalt, which is a constituent element, is a rare metal. And because it is expensive, it has big problems in terms of stable supply and cost.

As an alternative positive electrode active material, a non-aqueous electrolyte secondary battery using lithium nickel oxide obtained by substituting nickel for cobalt in lithium cobalt oxide has attracted attention (see Patent Document 3). By using this lithium nickel oxide, it is possible to increase the capacity to about 190 mAh/g, and since it is rich in nickel, which is a constituent element, and is economically superior, there are high expectations for its practical use.

Regarding the low thermal stability, which was conventionally regarded as a problem of lithium nickel oxide, recent research and development has shown a dramatic improvement by adding trace elements such as aluminum (see Patent Document 4). ).

On the other hand, a lithium-ion secondary battery using a phosphoric acid-based compound as a positive electrode active material with excellent thermal stability is attracting attention, and is reported to exhibit high battery characteristics. A typical example is lithium iron phosphate (LiFePO ₄ ), and lithium manganese phosphate (LiMnPO ₄ ) that operates at a high voltage is also being actively developed. (For example, see Patent Documents 5 and 6)

JP-A-8-236114 JP-A-11-16566 JP-A-9-219199 JP-A-11-135123 Canadian Patent No. 2270771 Japanese translation of PCT publication No. 2004-509058

However, the methods of the prior art still do not satisfy the various characteristics required for lithium ion secondary batteries, and in particular, further improvements in charge rate characteristics and load discharge characteristics are required.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a positive electrode capable of improving charge rate characteristics and load discharge characteristics, and a lithium ion secondary battery using the same. do.

As a result of intensive studies, the present inventors found that in a positive electrode comprising a positive electrode active material layer having a positive electrode active material, a conductive aid, and a binder on a positive electrode current collector, the wavelength on the surface of the positive electrode active material layer It has been found that by setting the reflectance Rc at 550 nm within a predetermined range, high charge rate characteristics and high load discharge characteristics can be obtained.
That is, in order to solve the above problems, the following means are provided.

The positive electrode according to the first aspect includes a positive electrode active material layer having a positive electrode active material, a conductive aid, and a binder on a positive electrode current collector, and a positive electrode active material layer having a wavelength of 550 nm on the surface of the positive electrode active material layer Reflectance Rc is 2.0≦Rc≦12.0%.

By setting the reflectance Rc on the surface of the positive electrode active material layer within a predetermined range, charge rate characteristics and load discharge characteristics are improved. Although its function is not clear, it is believed that the reflectance Rc of the surface of the positive electrode active material layer reflects the smoothness of the surface of the positive electrode active material layer and the state of surface compression of the positive electrode active material on the surface of the positive electrode active material layer. be done.

That is, it is presumed that controlling the smoothness of the surface of the positive electrode active material layer increases the reaction field with the electrolytic solution on the surface of the positive electrode active material layer, thereby obtaining high charge rate characteristics.

In addition, in addition to suppressing excessive impregnation of the electrolyte solution on the surface of the positive electrode active material by compressing the surface of the positive electrode active material layer, it is possible to achieve both high reactivity and suppression of side reactions. It is assumed that load discharge characteristics can be obtained.

As a method of controlling the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer to a specific range, for example, it is possible to change the rolling pressure during electrode rolling, the number of rolling times, the heating conditions during rolling, and the like. .

Furthermore, regardless of the surface compression state of the positive electrode active material layer, controlling the reflectance Rc on the surface of the positive electrode active material layer within a predetermined range is also considered to improve charge rate characteristics and load discharge characteristics.

This is because the reflectance Rc on the surface of the positive electrode active material layer suppresses the side reaction on the surface of the positive electrode active material layer, and in addition, the permeability of the electrolytic solution from the surface of the positive electrode active material layer into the inside of the positive electrode active material layer. It is presumed that by achieving both improvements, charge rate characteristics and load discharge characteristics will be improved.

As a different method for controlling the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer within a specific range, for example, the surface of the electrode obtained after rolling may be polished or controlled by applying a topcoat. It is possible.

In the positive electrode according to the first aspect, the positive electrode active material contains a compound represented by the following general formula (1) as a main component, and the surface of the positive electrode active material layer has a reflectance Rc1 of 8.0 at a wavelength of 550 nm. 0≦Rc1≦12.0% may be satisfied.
_{LixNiyM1 - yOz} ( ₁ )
(0<x≦1.1, 0≦y<0.5, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg)

By setting the reflectance Rc1 of the positive electrode containing the compound represented by the general formula (1) as a main component as the positive electrode active material within the above range, it is possible to further improve the charge rate characteristics.

In the positive electrode according to the above aspect, the density dc1 of the positive electrode active material layer may be 3.1≦dc1≦4.1 g/cm ³ .

In the positive electrode according to the above aspect, the amount Lc1 supported per unit area in the positive electrode active material layer may be 13.0≦Lc1≦25.0 mg/cm ² .

In the positive electrode according to the first aspect, the positive electrode active material contains a compound represented by the following formula (2) as a main component, and the surface of the positive electrode active material layer has a reflectance Rc2 of 3.5 at a wavelength of 550 nm. ≦Rc2≦7.8% may be satisfied.
_{LixNiyM1 - yOz} ( ₂ )
(0<x≦1.1, 0.5≦y≦1, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg)

By setting the reflectance Rc2 of the positive electrode containing the compound represented by the general formula (2) as a main component as the positive electrode active material within the above range, it is possible to further improve the load discharge characteristics.

In the positive electrode according to the above aspect, the density dc2 of the positive electrode active material layer may be 3.0≦dc2≦3.8 g/cm ³ .

In the positive electrode according to the above aspect, the amount Lc2 supported per unit area in the positive electrode active material layer may be 12.0≦Lc2≦24.0 mg/cm ² .

In the positive electrode according to the first aspect, the positive electrode active material contains a compound represented by the following formula (3) as a main component, and the surface of the positive electrode active material layer has a reflectance Rc3 of 2.0 at a wavelength of 550 nm. ≤Rc3≤5.8%.
_{LixMyOzPO4 ( 3 )}
(0 < x ≤ 1.1, 0 < y ≤ 1.1, 0 ≤ z ≤ 1.0, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, V have)

By setting the reflectance Rc3 of the positive electrode containing the compound represented by the general formula (3) as a main component as the positive electrode active material within the above range, it is possible to further improve the charge rate characteristics.

In the positive electrode according to the above aspect, the density dc3 of the positive electrode active material layer may be 1.8≦dc3≦2.5 g/cm ³ .

In the positive electrode according to the above aspect, the amount Lc3 supported per unit area in the positive electrode active material layer may be 8.0≦Lc3≦15.0 mg/cm ² .

A lithium ion secondary battery according to a second aspect includes any of the positive electrodes according to the first aspect, a negative electrode having a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, a non- and an aqueous electrolyte, and the surface of the negative electrode active material layer has a reflectance Ra of 7.5≦Ra≦16.0% at a wavelength of 550 nm.

By combining a negative electrode in which the reflectance Ra on the surface of the negative electrode active material layer is adjusted to a predetermined range, the charge rate characteristics and the load discharge characteristics are further improved.

The reflectance Ra on the surface of the negative electrode active material layer also reflects the smoothness of the surface of the negative electrode active material layer and the surface compression state of the negative electrode active material on the surface of the negative electrode active material layer, similarly to the reflectance Rc on the surface of the positive electrode active material layer. it seems to do.

Therefore, by combining negative electrodes whose reflectance Ra on the surface of the negative electrode active material layer is in the range of 7.5 ≤ Ra ≤ 16.0%, the charge rate characteristics and load discharge of the lithium ion secondary battery using this can be improved. It is estimated that the characteristics will improve.

In the lithium ion secondary battery according to the second aspect, the ratio Rc1/Ra between the reflectance Rc1 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 1.00<Rc1/Ra ≤ 1.53.

In the lithium ion secondary battery according to the second aspect, the ratio Rc2/Ra between the reflectance Rc2 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 0.29≦Rc2/Ra It may be <1.00.

In the lithium ion secondary battery according to the second aspect, the ratio Rc3/Ra between the reflectance Rc3 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 0.13≦Rc3/Ra ≤ 0.75.

According to such a configuration, the lithium ion secondary battery using this has good charge rate characteristics. It is presumed that the impregnation of the electrolytic solution on the surface of the positive electrode active material layer and the negative electrode active material layer and the suppression of side reactions are compatible, and that lithium ions are favorably transferred.

Further, it can be seen that the preferable range of the ratio of the reflectance Rc of the positive electrode active material layer and the reflectance Ra of the surface of the negative electrode active material layer varies depending on the positive electrode active material used and the reflectance of the surface of the positive electrode active material layer.

It is presumed that this is because the positive electrode surface using each positive electrode active material has a different reaction state with the electrolyte solution, and that the favorable state of the positive electrode surface with respect to the impregnation of the electrolyte solution into the positive electrode is different. ing.

In the lithium ion secondary battery according to the second aspect, the negative electrode active material may contain a carbon material having a graphite structure.

When the negative electrode having the above reflectance contains a carbon material having a graphite structure as the negative electrode active material, it has particularly good charge rate characteristics.

It is presumed that this is because both impregnability of the electrolyte and suppression of side reactions can be achieved without excessively reducing lithium ion desorption sites of the carbon material having a graphite structure on the surface of the negative electrode active material layer.

In the lithium ion secondary battery according to the second aspect, the non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte, the non-aqueous solvent contains ethylene carbonate, and the content of ethylene carbonate is 10 to 30 vol. %.

Such a configuration has good charge rate characteristics. It is presumed that this is because a good coating can be formed while suppressing excessive decomposition of ethylene carbonate, which is partly decomposed on the electrode surface and becomes a coating component.

INDUSTRIAL APPLICABILITY The present invention makes it possible to provide a positive electrode for a lithium ion secondary battery capable of improving charge rate characteristics and load discharge characteristics, and a lithium ion secondary battery using the same.

It is a cross-sectional schematic diagram of the lithium ion secondary battery concerning this embodiment.

Hereinafter, this embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the gist of the invention.

(lithium ion secondary battery)
FIG. 1 is a schematic cross-sectional view of a lithium-ion secondary battery according to this embodiment. A lithium ion secondary battery 100 shown in FIG. 1 mainly includes a laminate 40 , a case 50 that accommodates the laminate 40 in a sealed state, and a pair of leads 60 and 62 connected to the laminate 40 . Although not shown, a non-aqueous electrolyte is accommodated in case 50 together with laminate 40 .

In the laminate 40, the positive electrode 20 and the negative electrode 30 are arranged facing each other with the separator 10 interposed therebetween. The positive electrode 20 has a positive electrode active material layer 24 provided on a plate-like (film-like) positive electrode current collector 22 . The negative electrode 30 has a negative electrode active material layer 34 provided on a plate-like (film-like) negative electrode current collector 32 .

The positive electrode active material layer 24 and the negative electrode active material layer 34 are in contact with both sides of the separator 10 respectively. Leads 62 and 60 are connected to ends of the positive electrode current collector 22 and the negative electrode current collector 32 , respectively, and the ends of the leads 60 and 62 extend to the outside of the case 50 . In FIG. 1, the case 50 has one layered body 40, but a plurality of layers may be stacked.

(positive electrode)
The positive electrode 20 has a positive electrode current collector 22 and a positive electrode active material layer 24 provided on the positive electrode current collector 22 .

The positive electrode according to this embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0≦Rc≦12.0. %.

(First embodiment)
The positive electrode according to the first embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains a compound represented by the following general formula (1) as a main component as the positive electrode active material. and the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 8.0≦Rc1≦12.0%.
_{LixNiyM1 - yOz} ( ₁ )
(0<x≦1.1, 0≦y<0.5, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg)

In the positive electrode according to the first embodiment, it is particularly preferable that the surface of the positive electrode active material layer has a reflectance Rc1 of 9.5≦Rc1≦10.5% at a wavelength of 550 nm.

By setting the reflectance Rc1 on the surface of the positive electrode active material layer within the above range, particularly good charge rate characteristics can be obtained.

It is speculated that when the reflectance Rc1 is within the above range, the effect of suppressing excessive impregnation of the electrolyte solution on the surface of the positive electrode active material layer and achieving both high reactivity and suppression of side reactions is maximized. ing.

In the positive electrode according to the first embodiment, the density dc1 in the positive electrode active material layer is preferably 3.1≦dc1≦4.1 g/cm ³ . Further, the density dc1 in the positive electrode active material layer is more preferably 3.3≦dc1≦3.9 g/cm ³ and more preferably 3.5≦dc1≦3.7 g/cm ³ .

In the positive electrode according to the first embodiment, the amount Lc1 supported per unit area in the positive electrode active material layer is preferably 13.0≦Lc1≦25.0 mg/cm ² .

In the positive electrode according to the present embodiment, the porosity Pc1 in the positive electrode active material layer is preferably 21.0≦Pc1≦25.0%, more preferably 23.0≦Pc1≦24.0%. .

More preferably, the positive electrode according to the first embodiment simultaneously satisfies the density dc1 of the positive electrode active material layer and the porosity Pc1 of the positive electrode active material layer.

By satisfying dc1 and Pc and 1 in the positive electrode active material layer at the same time, it is possible not only to suppress excessive impregnation of the electrolytic solution, to achieve high reactivity and to suppress side reactions, but also to It is surmised that high charging rate characteristics can be obtained by increasing the diffusion effect of

(Positive electrode active material)
Examples of positive electrode active materials that are compounds represented by the above general formula (1) include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.2 Co _0.8 O ₂ Those containing Ni, Mn, and Co as main components, and lithium-containing transition metal oxides represented by LiCoO ₂ can be used.

Among these, lithium-containing transition metal oxides represented by LiCoO ₂ and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ are preferably used.

These lithium-containing transition metal oxides are preferable because they have high structural stability, are easy to synthesize, and can provide sufficient charge rate characteristics.

The positive electrode active material represented by the general formula (1) does not need to have an oxygen content of the stoichiometric composition represented by this composition formula, and may include a wide range of oxygen-deficient materials. That is, those identified as the same composition system by X-ray diffraction or the like are targeted.

Therefore, in addition to the positive electrode active material represented by the general formula (1), a part of Ni or M may be substituted with a different element, and the concentration gradient of the element in the positive electrode active material and the surface of the positive electrode active material At least a portion may be coated with oxide, carbon, or the like.

In addition, the positive electrode active material layer according to the present embodiment may contain positive electrode active materials having different compositions, with the positive electrode active material represented by the general formula (1) as a main component.

Examples of positive electrode active materials having different compositions include lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and general formula: LiNi _x Co _y M _z O ₂ (x+y+z). = 1, 0.5 ≤ x < 1, 0 ≤ y < 1, 0 ≤ z < 1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr). composite metal oxides, lithium vanadium compounds _{( LiVOPO4, Li3V2(PO4)3 , LiV2O5 , Li2VP2O7 ) ,} olivine _- type _{LiMPO4 (} where M is Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, V), composite metal oxides such as lithium titanate (Li ₄ Ti ₅ O ₁₂ ), polyacetylene, polyaniline, polypyrrole , polythiophene, polyacene, and other existing positive electrode active materials capable of intercalating and deintercalating lithium ions.

In the positive electrode active material according to the first embodiment, containing as a main component means that the content of the positive electrode active material, which is the compound represented by the general formula (1), is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

When the positive electrode active material having a different composition is contained, the positive electrode active material represented by the general formula (1) is added to the total of the positive electrode active material represented by the general formula (1) and the positive electrode active material having a different composition. The content of the substance is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

(Second embodiment)
The positive electrode according to the second embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains a compound represented by the following formula (2) as the positive electrode active material as a main component, A reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer satisfies 3.5≦Rc2≦7.8%.
_{LixNiyM1 - yOz} ( ₂ )
(0<x≦1.1, 0.5≦y≦1, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg)

In the positive electrode according to the second embodiment, it is particularly preferable that the surface of the positive electrode active material layer has a reflectance Rc2 of 4.3≦Rc2≦6.3% at a wavelength of 550 nm.

By setting the reflectance Rc2 on the surface of the positive electrode active material layer within the above range, particularly good load discharge characteristics can be obtained.

It is speculated that when the reflectance Rc2 is within the above range, the effect of suppressing excessive impregnation of the electrolyte solution on the surface of the positive electrode active material layer and achieving both high reactivity and suppression of side reactions is maximized. ing.

In the positive electrode according to the second embodiment, the density dc2 in the positive electrode active material layer is preferably 3.0≦dc2≦3.8 g/cm ³ and 3.2≦dc2≦3.6 g/cm ³ is more preferable.

In the positive electrode according to the second embodiment, the amount Lc2 supported per unit area in the positive electrode active material layer is preferably 12.0≦Lc2≦15.0 mg/cm ² .

In the positive electrode according to the second embodiment, the porosity Pc2 in the positive electrode active material layer is preferably 21.0≦Pc2≦25.0%, and preferably 23.0≦Pc2≦24.5%. more preferred.

More preferably, the positive electrode according to the second embodiment simultaneously satisfies the density dc2 of the positive electrode active material layer and the porosity Pc2 of the positive electrode active material layer.

By satisfying dc2 and Pc2 in the positive electrode active material layer at the same time, it is possible not only to suppress excessive impregnation of the electrolyte, but also to achieve high reactivity and suppression of side reactions. It is speculated that high load discharge characteristics can be obtained by increasing the diffusion effect.

(Positive electrode active material)
Examples of positive electrode active materials that are compounds represented by the above general formula (2) include LiNi _0.8 Co _0.2 O ₂ and LiNi _0.85 Co _0.10 Al _0.05 O ₂ Those containing Ni and Co as main components, and Ni, Co, and Mn represented by LiNi _0.8 Mn _0.1 Co _0.1 O ₂ and LiNi _0.6 Mn _0.2 Co _0.2 O ₂ can be used.

Among these, LiNi _0.85 Co _0.10 Al _0.05 O ₂ in which part of Ni or Co is replaced with Al, and LiNi _0.8 Mn _0.1 Co 0.85 Co 0.10 Al 0.05 O 2 _{. 1} O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ Lithium-containing transition metal oxides with a high Ni content are preferable because high discharge capacity can be obtained.

Note that the positive electrode active material represented by the general formula (2) does not need to have an oxygen content of the stoichiometric composition represented by this composition formula, and may include a wide range of oxygen-deficient materials. That is, those identified as the same composition system by X-ray diffraction or the like are targeted.

Therefore, in addition to the positive electrode active material represented by the general formula (2), a part of Ni or M may be substituted with a different element, and the concentration gradient of the element in the positive electrode active material and the surface of the positive electrode active material At least a portion may be coated with oxide, carbon, or the like.

Moreover, the positive electrode active material layer according to the second embodiment may contain a positive electrode active material having a different composition from the positive electrode active material represented by the general formula (2) as a main component.

Positive electrode active materials having different compositions include lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and general formula: LiNi _x Co _y M _z O ₂ (x+y+z). = 1, 0 ≤ x < 0.5, 0.5 ≤ y < 1, 0 ≤ z < 1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr) The represented composite metal oxides, lithium vanadium compounds _{( LiVOPO4, Li3V2(PO4)3 , LiV2O5 , Li2VP2O7 ) ,} olivine _- type _{LiMPO4 (} wherein M is Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, V), composite metal oxides such as lithium titanate (Li ₄ Ti ₅ O ₁₂ ), polyacetylene, polyaniline , polypyrrole, polythiophene, and polyacene.

In the positive electrode active material according to the second embodiment, containing as a main component means that the content of the positive electrode active material, which is the compound represented by the general formula (2), is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

When the positive electrode active material having a different composition is contained, the positive electrode active material represented by the general formula (2) is added to the total of the positive electrode active material represented by the general formula (2) and the positive electrode active material having a different composition. The substance content is preferably 60.0% by mass or more, more preferably 80.0% by mass or more, and particularly preferably 95.0% by mass or more.

(Third embodiment)
A positive electrode according to a third embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains as a main component a compound represented by the following formula (3) as the positive electrode active material, A reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer satisfies 2.0≦Rc3≦5.8%.
_{LixMyOzPO4 ( 3 )}
(0 < x ≤ 1.1, 0 < y ≤ 1.1, 0 ≤ z ≤ 1.0, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, V have)

In the positive electrode according to the third embodiment, it is particularly preferable that the surface of the positive electrode active material layer has a reflectance Rc2 of 3.2≦Rc3≦4.9% at a wavelength of 550 nm.

By setting the reflectance Rc3 on the surface of the positive electrode active material layer within the above range, particularly good load discharge characteristics can be obtained.

It is speculated that when the reflectance Rc3 is within the above range, the effect of suppressing excessive impregnation of the electrolyte solution on the surface of the positive electrode active material layer and achieving both high reactivity and suppression of side reactions is maximized. ing.

In the positive electrode according to the third embodiment, the density dc3 in the positive electrode active material layer is preferably 1.8≦dc3≦2.5/cm ³ and 1.9≦dc3≦2.3 g/cm ³ is more preferable.

In the positive electrode according to the third embodiment, the amount Lc3 supported per unit area in the positive electrode active material layer is preferably 12.0≦Lc3≦15.0 mg/cm ² .

In the positive electrode according to the third embodiment, the porosity Pc3 in the positive electrode active material layer is preferably 21.0≦Pc3≦25.0%, and preferably 23.0≦Pc3≦24.5%. more preferred.

More preferably, the positive electrode according to the third embodiment simultaneously satisfies the density dc3 of the positive electrode active material layer and the porosity Pc3 of the positive electrode active material layer.

By satisfying dc3 and Pc3 in the positive electrode active material layer at the same time, it is possible not only to suppress excessive impregnation of the electrolytic solution, to achieve high reactivity and to suppress side reactions, but also to suppress the flow of the electrolytic solution inside the positive electrode active material layer. It is speculated that high load discharge characteristics can be obtained by increasing the diffusion effect.

(Positive electrode active material)
Examples of the positive electrode active material, which is a compound represented by the general formula (3), include those having an olivine structure represented by LiFePO ₄ and LiMnPO ₄ , and LiFe _x Mn _1-x PO ₄ (0<x< A solid solution as represented by 1) and a phosphoric acid compound represented by LiVOPO ₄ can be used.

The positive electrode active material represented by the general formula (3) does not need to have an oxygen content of the stoichiometric composition represented by this composition formula, and may include a wide range of oxygen-deficient materials. That is, those identified as the same composition system by X-ray diffraction or the like are targeted.

Therefore, in addition to the positive electrode active material represented by the general formula (3), a part of M or P may be substituted with a different element, and the concentration gradient of the element in the positive electrode active material and the surface of the positive electrode active material At least a portion may be coated with oxide, carbon, or the like.

Moreover, the positive electrode active material layer according to the third embodiment may contain positive electrode active materials having different compositions, with the positive electrode active material represented by the general formula (3) being the main component.

Positive electrode active materials having different compositions include lithium cobalt oxide (LiCoO ₂ ), lithium manganese oxide (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and general formula: LiNi _x Co _y M _z O ₂ (x+y+z). = 1, 0 ≤ x ≤ 1.0, 0 ≤ y < 1, 0 ≤ z < 1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr). composite metal oxides, lithium vanadium compounds (LiV ₂ O ₅ , Li ₂ VP ₂ O ₇ ), Nasicon-type Li ₃ M ₂ (PO ₄ ) ₃ (where M is one or more selected from V, Fe, and Mo element), a phosphoric acid compound represented by Li ₂ MP ₂ O ₇ (where M is one or more selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, V ), composite metal oxides such as lithium titanate (Li ₄ Ti ₅ O ₁₂ ), polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, and other existing positive electrode active materials capable of intercalating and deintercalating lithium ions. .

In the positive electrode active material according to the third embodiment, containing as a main component means that the content of the positive electrode active material, which is the compound represented by the general formula (3), is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

When the positive electrode active material having a different composition is contained, the positive electrode active material represented by the general formula (3) is added to the total of the positive electrode active material represented by the general formula (3) and the positive electrode active material having a different composition. The content of the substance is preferably 60.0% by mass or more, more preferably 70.0% by mass or more, and particularly preferably 80.0% by mass or more.

The content of each positive electrode active material in the positive electrode active material layer according to the present embodiment is calculated by determining the content of each element using elemental analysis after identifying the compound species contained by X-ray diffraction measurement. can be done.

Further, the positive electrode active material layer according to this embodiment may contain members such as a conductive aid and a binder in addition to the positive electrode active material.

(Conductivity aid)
Examples of conductive aids include carbon powders such as carbon blacks, carbon nanotubes, carbon materials, metal fine powders such as copper, nickel, stainless steel and iron, mixtures of carbon materials and metal fine powders, and conductive oxides such as ITO. mentioned.

(Binder)
The binder binds the active materials together and also binds the active materials and the current collector 22 . The binder may be any one capable of bonding as described above, and examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene Ethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF) and other fluororesins.

In addition to the above, binders such as vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFPTFE-based fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluororubber (VDF-PFP-TFE fluororubber), vinylidene fluoride Vinylidene fluoride-based fluorine such as Ride-perfluoromethyl vinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber) Rubber may be used.

Alternatively, an electronically conductive polymer or an ionically conductive polymer may be used as the binder. Examples of the electron-conducting conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material. Examples of the ion-conducting conductive polymer include those obtained by combining a polymer compound such as polyethylene oxide or polypropylene oxide with a lithium salt or an alkali metal salt mainly containing lithium.

The contents of the positive electrode active material, conductive material, and binder in the positive electrode active material layer 24 are not particularly limited. The composition ratio of the positive electrode active material in the positive electrode active material layer 24 is preferably 90.0% or more and 98.0% or less in mass ratio. The composition ratio of the conductive material in the positive electrode active material layer 24 is preferably 1.0% or more and 3.0% or less in mass ratio, and the composition ratio of the binder in the positive electrode active material layer 24 is 2.0% in mass ratio. It is preferably 0% or more and 5.0% or less.

By setting the contents of the positive electrode active material and the binder within the above ranges, it is possible to prevent the situation where the amount of the binder is too small and a strong positive electrode active material layer cannot be formed. In addition, it is possible to suppress the tendency that the amount of the binder that does not contribute to the electric capacity increases, making it difficult to obtain a sufficient volumetric energy density.

Moreover, by setting the contents of the positive electrode active material and the conductive material within the above ranges, sufficient electronic conductivity can be obtained in the positive electrode active material layer, and high volumetric energy density and output characteristics can be obtained.

(Positive electrode current collector)
The positive electrode current collector 22 may be a conductive plate material, and for example, a metal thin plate such as aluminum, copper, or nickel foil, or an alloy thin plate thereof can be used. Among these, it is preferable to use a thin metal plate of aluminum, which is light in weight.

(negative electrode)
The negative electrode 30 has a negative electrode current collector 32 and a negative electrode active material layer 34 provided on the negative electrode current collector 32 .

In the negative electrode according to the present embodiment, the surface of the negative electrode active material layer preferably has a reflectance Ra of 7.5≦Ra≦16.0% at a wavelength of 550 nm.

High charge rate characteristics can be obtained by using the negative electrode according to the present embodiment. It is thought that this reflects the smoothness of the surface of the negative electrode active material layer and the state of surface compression of the negative electrode active material on the surface of the negative electrode active material layer. It is presumed that the charge rate characteristic is improved by combining the negative electrode in the range of 0.0%.

(Negative electrode active material)
As a material for the negative electrode active material, various materials that are used as negative electrode active materials for known lithium secondary batteries can be used. Examples of materials for the negative electrode active material include carbon materials such as graphite, hard carbon, soft carbon, and MCMB, silicon, silicon-containing compounds such as silicon oxides represented by SiO _x (0<x<2), Lithium metal, metals or semimetals that form alloys with lithium, alloys thereof, amorphous compounds mainly composed of oxides such as tin dioxide, and lithium titanate (Li ₄ Ti ₅ O ₁₂ ). . Examples of metals that form alloys with metallic lithium include aluminum, silicon, tin, and germanium.

A carbon material having a graphite structure is preferably used as the negative electrode active material according to the present embodiment, and it is particularly preferable to use at least one of artificial graphite and natural graphite.

Further, the negative electrode active material layer according to the present embodiment may contain negative electrode active materials having different compositions mainly composed of a carbon material having a graphite structure. Among them, it is preferable to mix and use a carbon material having a graphite structure because metals or semimetals that form alloys with lithium, represented by silicon, and alloys thereof exhibit high charge-discharge capacity.

When negative electrode active materials having different compositions are contained, the content of the carbon material having a graphite structure is 70.0% by mass or more with respect to the total of the carbon material having a graphite structure and the negative electrode active material having a different composition. is preferred, 90.0 mass % or more is more preferred, and 95.0 mass % or more is particularly preferred.

In addition to the negative electrode active material, the negative electrode active material layer according to the present embodiment may contain members such as a conductive aid and a binder.

(Negative electrode conductive material)
Examples of conductive materials include carbon powders such as carbon blacks, carbon nanotubes, carbon materials, metal fine powders such as copper, nickel, stainless steel and iron, mixtures of carbon materials and metal fine powders, and conductive oxides such as ITO. be done. Among these, carbon powders such as acetylene black and ethylene black are particularly preferred. If the negative electrode active material alone can ensure sufficient conductivity, the lithium ion secondary battery 100 does not need to contain a conductive aid.

(Binder)
As the binder, the same one as that used for the positive electrode can be used. In addition, as the binder, for example, cellulose, styrene/butadiene rubber, ethylene/propylene rubber, polyimide resin, polyamideimide resin, acrylic resin, or the like may be used.

The contents of the negative electrode active material, conductive material, and binder in the negative electrode active material layer 34 are not particularly limited. The composition ratio of the negative electrode active material in the negative electrode active material layer 34 is preferably 90.0% or more and 98.0% or less in mass ratio. The composition ratio of the conductive material in the negative electrode active material layer 34 is preferably 0% or more and 3.0% or less by mass, and the composition ratio of the binder in the negative electrode active material layer 34 is 2.0% by mass. It is preferable that it is more than or equal to 5.0% or less.

By setting the contents of the negative electrode active material and the binder within the above ranges, it is possible to prevent a situation in which the amount of the binder is too small to form a strong negative electrode active material layer. In addition, it is possible to suppress the tendency that the amount of the binder that does not contribute to the electric capacity increases, making it difficult to obtain a sufficient volumetric energy density.

Moreover, by setting the contents of the negative electrode active material and the conductive material within the above ranges, sufficient electronic conductivity can be obtained in the negative electrode active material layer, and high volumetric energy density and output characteristics can be obtained.

(Negative electrode current collector)
The negative electrode current collector 32 may be a conductive plate material, and for example, a metal thin plate such as aluminum, copper, or nickel foil, or an alloy thin plate thereof can be used. Among these, it is preferable to use a thin metal plate of copper.

Instead of providing the negative electrode active material layer 34, a configuration may be adopted in which lithium ions are deposited as metallic lithium on the surface of the negative electrode current collector 32 during charging, and the deposited metallic lithium is dissolved as lithium ions during discharging. In this case, since the negative electrode active material layer 34 is not required, the volumetric energy density of the battery can be improved. In that case, a copper foil can be used as the negative electrode current collector 32 .

By using the positive electrode 20 and the negative electrode 30 in the lithium ion secondary battery according to this embodiment, high charging rate characteristics can be obtained.

In particular, the ratio Rc1/Ra between the reflectance Rc1 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 1.00<Rc1/Ra≦1.53, and is 1.22. It is more preferable that <Rc1/Ra≦1.38.

Further, the ratio Rc2/Ra between the reflectance Rc2 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 0.29≦Rc2/Ra<1.00, and is 0.44. More preferably, ≦Rc2/Ra≦0.63.

Further, the ratio Rc3/Ra between the reflectance Rc3 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 0.13≦Rc3/Ra≦0.75, and is 0.39. More preferably, ≦Rc3/Ra≦0.60.

It is presumed that the impregnation of the electrolytic solution on the surface of the positive electrode active material layer and the negative electrode active material layer and the suppression of side reactions are compatible, and that lithium ions are favorably transferred.

(separator)
The separator 18 may be formed of an electrically insulating porous structure. Examples include fibrous nonwoven fabrics made of at least one constituent material selected from the group consisting of polypropylene.

(Non-aqueous electrolyte solution)
The non-aqueous electrolyte solution has an electrolyte dissolved in a non-aqueous solvent, and may contain a cyclic carbonate and a chain carbonate as the non-aqueous solvent.

The cyclic carbonate is not particularly limited as long as it can solvate the electrolyte, and known cyclic carbonates can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC) and the like can be used.

The chain carbonate is not particularly limited as long as it can reduce the viscosity of the cyclic carbonate, and known chain carbonates can be used. Examples include diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc. may be mixed and used.

The non-aqueous solvent according to this embodiment contains ethylene carbonate, and the content of the ethylene carbonate is 10 to 30 vol. %.

It is presumed that this is because a good coating can be formed while suppressing excessive decomposition of ethylene carbonate, which is partly decomposed on the electrode surface and becomes a coating component.

Moreover, the non-aqueous electrolytic solution according to the present embodiment may be used in combination with a gel electrolyte or a solid electrolyte.

Examples of electrolytes include _LiPF6 , LiClO4, _LiBF4 , _LiCF3SO3 , _LiCF3 , _CF2SO3 , _LiC ( _CF3SO2 ) _{3 ,} LiN _{( CF3SO2} ) _{2 ,} LiN _{( CF3} Lithium salts such as _CF2SO2 ) _{2 ,} LiN _{( CF3SO2} ) _{( C4F9SO2} ), LiN _{( CF3CF2CO} ) ₂ , _LiBOB can be used. In addition, these lithium salts may be used individually by 1 type, and may use 2 or more types together. In particular, from the viewpoint of conductivity, it is preferable to contain LiPF ₆ .

When dissolving LiPF ₆ in a non-aqueous solvent, it is preferable to adjust the concentration of the electrolyte in the non-aqueous electrolyte to 0.5 to 2.0 mol/L. When the concentration of the electrolyte is 0.5 mol/L or more, the conductivity of the non-aqueous electrolyte can be sufficiently ensured, and a sufficient capacity can be easily obtained during charging and discharging. In addition, by suppressing the concentration of the electrolyte to within 2.0 mol/L, the increase in the viscosity of the non-aqueous electrolyte can be suppressed, the mobility of lithium ions can be sufficiently secured, and sufficient capacity can be obtained during charging and discharging. easier.

When LiPF ₆ is mixed with other electrolytes, it is preferable to adjust the lithium ion concentration in the non-aqueous electrolyte to 0.5 to 2.0 mol/L, and the lithium ion concentration from LiPF ₆ is 50 mol% of that. It is more preferable to include the above.

(Measurement of reflectance)
The reflectances Rc and Ra according to this embodiment can be measured using a commercially available spectrophotometer or the like.

The reflectance Rc on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer according to the present embodiment are controlled by the post-treatment after molding the positive electrode active material layer and the negative electrode active material layer and the molding conditions. can do.

As a method of controlling the reflectance, it is possible to change the rolling pressure during electrode rolling, the number of times of rolling, the heating conditions during rolling, and the like. It can also be controlled by the material and surface shape of the rolling plate and rolling rolls used during rolling.

Further, the surface of the electrode obtained after rolling may be polished or topcoated. When applying a topcoat, it is preferable to use a topcoat liquid having conductivity in order to suppress deterioration of battery characteristics.

(Manufacturing method of positive electrode 20 and negative electrode 30)
Next, a method for manufacturing the positive electrode 20 and the negative electrode 30 according to this embodiment will be described.

A binder and a solvent are mixed with the positive electrode active material or the negative electrode active material. A conductive aid may be added as necessary. Examples of solvents that can be used include water, N-methyl-2-pyrrolidone, and the like. The mixing method of the components constituting the coating material is not particularly limited, and the mixing order is also not particularly limited. The paint is applied to the current collectors 22 and 32 . The coating method is not particularly limited, and any method that is commonly employed in the production of electrodes can be used. Examples thereof include slit die coating and doctor blade methods.

Subsequently, the solvent in the paint applied on the current collectors 22 and 32 is removed. The removal method is not particularly limited, and the current collectors 22 and 32 coated with paint may be dried in an atmosphere of 80° C. to 150° C., for example.

Then, the electrode on which the positive electrode active material layer 24 and the negative electrode active material layer 34 are formed in this way is pressed by a roll press device or the like, if necessary. By adjusting the pressing pressure, the number of times of pressing, and the shape of the pressing material of the pressing device, the reflectance on the surface of the positive electrode active material layer 24 and the negative electrode active material layer 34 can be controlled.

Through the steps described above, an electrode in which the electrode active material layers 24 and 34 are formed on the current collectors 22 and 32 is obtained.

(Manufacturing method of lithium ion secondary battery)
Next, a method for manufacturing a lithium ion secondary battery according to this embodiment will be described. A method for manufacturing a lithium ion secondary battery according to the present embodiment includes a positive electrode 20 containing the above-described active material, a negative electrode 30, a separator 10 interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution containing a lithium salt. and are enclosed in the exterior body 50 .

For example, the positive electrode 20 containing the above-described active material, the negative electrode 30, and the separator 10 are laminated, and the positive electrode 20 and the negative electrode 30 are heated and pressurized with a press from a direction perpendicular to the lamination direction, and the positive electrode is 20, the separator 10, and the negative electrode 30 are brought into close contact with each other. Then, for example, a lithium ion secondary battery can be produced by putting the laminate 40 in a bag-shaped outer package 50 that has been prepared in advance, and injecting the non-aqueous electrolyte solution containing the lithium salt. Instead of injecting the non-aqueous electrolyte solution containing the lithium salt into the exterior body, the laminated body 40 may be previously impregnated with the non-aqueous electrolyte solution containing the lithium salt.

It should be noted that the present invention is not limited to the above embodiments. The above embodiment is an example, and any device having substantially the same configuration as the technical idea described in the scope of the claims of the present invention and achieving the same effect is the present invention. included in the technical scope of

Although the embodiments according to the present invention have been described in detail above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiment, a laminated film type lithium ion secondary battery was described, but the same can be applied to a lithium ion secondary battery having a structure in which a positive electrode, a negative electrode and a separator are wound or folded. can. Furthermore, as a battery shape, it can be suitably applied to a lithium ion secondary battery having a cylindrical shape, a square shape, a coin shape, or the like.

Hereinafter, the present invention will be described in further detail using examples and comparative examples based on the above embodiments.

(Example 1)
(Preparation of positive electrode)
Weighed 97 parts by weight of LiCoO ₂ as a positive electrode active material, 1.5 parts by weight of PVDF (HSV-800) as a binder, and 1.5 parts by weight of carbon black (Super-P) as a conductive aid. and dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm and dried at a temperature of 120° C. for 30 minutes to remove the solvent. After that, press treatment was performed at a linear pressure of 2000 kgf/cm using a roll press apparatus in which rolling rolls were heated to 81°C. One cycle was air cooling after press treatment. After performing three cycles of press treatment, a positive electrode was produced by punching into an electrode size of 18 mm×22 mm using a mold.

A reflectance Rc1 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrophotometer (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The Rc1 of the obtained positive electrode was 8.0% using the average of three measurements.

The resulting positive electrode was cut into a square of 10 cm ² , and the density dc1 of the positive electrode active material layer ^, the amount Lc1 supported per unit area, and the porosity Pc1 were calculated. 1 mg/cm ² , Pc1=23.0%.

(Preparation of negative electrode)
96 parts by weight of graphite powder as a negative electrode active material, 2.5 parts by weight of styrene-butadiene rubber as a binder, and 1.5 parts by weight of carboxymethyl cellulose as a thickener were weighed and dispersed in water to prepare a slurry. The resulting slurry was applied onto a copper foil having a thickness of 15 μm and dried at 120° C. for 30 minutes to remove the solvent. After that, press treatment was performed at a linear pressure of 500 kgf/cm using a roll press apparatus in which rolling rolls were heated to 82°C. After the press treatment, air cooling was defined as one cycle, and three cycles of press treatment were performed.

A metal mold was used to punch an electrode size of 19 mm×23 mm to produce a negative electrode.

A reflectance Ra at a wavelength of 550 nm on the surface of the obtained negative electrode active material layer was measured using a spectrophotometer (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The average of three measurements was used, and the Ra of the positive and negative electrodes obtained was 7.8%, and the ratio of Rc1 to Ra was Rc1/Ra1.03.

(Non-aqueous electrolyte solution)
In a non-aqueous solvent obtained by mixing ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) as a non-aqueous electrolyte solution, LiPF ₆ was dissolved as an electrolyte so as to have a concentration of 1.3 mol/L. I used something else. The volume ratio of EC, PC and EMC in the non-aqueous solvent was EC:PC:EMC=10:10:80.

(separator)
A polyethylene microporous membrane (porosity: 40%, shutdown temperature: 134°C) having a thickness of 20 µm was prepared.

(Production of battery cells)
The positive electrode for a lithium ion secondary battery and the negative electrode for a lithium ion secondary battery were laminated via a polyethylene separator to prepare an electrode laminate. Using this as one layer of the electrode body, an electrode laminate composed of four layers was produced by the same production method. Since the positive electrode and the negative electrode are provided with respective mixture layers on both sides, they are composed of three negative electrodes, two positive electrodes, and four separators. Furthermore, in the negative electrode of the electrode laminate, a nickel negative electrode lead is attached to the protruding end of the copper foil not provided with the negative electrode mixture layer, while in the positive electrode of the electrode laminate, the positive electrode mixture layer is provided. An aluminum positive electrode lead was attached to the protruding end of the aluminum foil that was not exposed by an ultrasonic fusion machine. Then, this electrode laminate was fused to an aluminum laminate film for the exterior body, and the laminate film was folded to insert the electrode body into the exterior body. A closed portion was formed by heat-sealing except for one side around the exterior, and a non-aqueous electrolyte was injected through this opening. Then, the opening of the outer package was heat-sealed while the pressure was reduced by a vacuum sealer, and a laminate-type battery cell in Example 1 was produced. In addition, preparation of the battery cell was performed in a dry room.

(Example 2)
A battery cell of Example 2 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was heated to 88° C. in the production of the positive electrode.

(Example 3)
A battery cell of Example 3 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was heated to 91° C. in producing the positive electrode.

(Example 4)
A battery cell of Example 4 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was heated to 97° C. in producing the positive electrode.

(Example 5)
A battery cell of Example 5 was produced in the same manner as in Example 1, except that the temperature of the roll for rolling during press treatment was set to 105° C. in the production of the positive electrode.

(Example 6)
A battery cell of Example 6 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was set to 70° C. in producing the positive electrode.

(Example 7)
A battery cell of Example 7 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was set to 54° C. in producing the positive electrode.

(Example 8)
A battery cell of Example 8 was produced in the same manner as in Example 3, except that the linear pressure during press treatment was 1050 kgf/cm in producing the positive electrode.

(Example 9)
A battery cell of Example 9 was produced in the same manner as in Example 3, except that the linear pressure during press treatment was 1120 kgf/cm in the production of the positive electrode.

(Example 10)
A battery cell of Example 10 was produced in the same manner as in Example 3, except that in the production of the positive electrode, the linear pressure during pressing was set to 1500 kgf/cm.

(Example 11)
A battery cell of Example 11 was produced in the same manner as in Example 3, except that in the production of the positive electrode, the linear pressure during pressing was set to 1850 kgf/cm.

(Example 12)
A battery cell of Example 12 was produced in the same manner as in Example 3, except that in the production of the positive electrode, the linear pressure during pressing was set to 2600 kgf/cm.

(Example 13)
A battery cell of Example 13 was produced in the same manner as in Example 3, except that the linear pressure during press treatment was 3000 kgf/cm in producing the positive electrode.

(Example 14)
A battery cell of Example 14 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the amount Lc1 supported per unit area was 12.0 mg/cm ² . made. The load Lc1 per unit area of the produced positive electrode was measured and found to be 12.1 mg/cm ² .

(Implementation 15)
A battery cell of Example 15 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc1 per unit area was 13.0 mg/cm ² . made. The loading amount Lc1 per unit area of the produced positive electrode was measured and found to be 12.8 mg/cm ² .

(Example 16)
A battery cell of Example 16 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc1 per unit area was 15.5 mg/cm ² . made. The load Lc1 per unit area of the produced positive electrode was measured and found to be 15.4 mg/cm ² .

(Example 17)
A battery cell of Example 17 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the loading amount Lc1 per unit area was 16.0 mg/cm ² . made. The load Lc1 per unit area of the produced positive electrode was measured and found to be 16.1 mg/cm ² .

(Example 18)
A battery cell of Example 18 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc1 per unit area was 20.0 mg/cm ² . made. The loading amount Lc1 per unit area of the produced positive electrode was measured and found to be 20.1 mg/cm ² .

(Example 19)
A battery cell of Example 19 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc1 per unit area was 25.0 mg/cm ² . made. The loading amount Lc1 per unit area of the produced positive electrode was measured and found to be 25.0 mg/cm ² .

(Example 20)
A battery cell of Example 20 was prepared in the same manner as in Example 3, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc1 per unit area was 25.5 mg/cm ² . made. The loading amount Lc1 per unit area of the produced positive electrode was measured and found to be 25.5 mg/cm ² .

(Example 21)
A battery cell of Example 21 was produced in the same manner as in Example 3, except that the roll for rolling during press treatment was heated to 75° C. in producing the negative electrode.

(Example 22)
A battery cell of Example 22 was produced in the same manner as in Example 3, except that the roll for rolling during press treatment was heated to 79° C. in the production of the negative electrode.

(Example 23)
A battery cell of Example 23 was produced in the same manner as in Example 3, except that the roll for rolling during press treatment was heated to 89° C. in the production of the negative electrode.

(Example 24)
A battery cell of Example 24 was produced in the same manner as in Example 3, except that the roll for rolling during press treatment was heated to 96° C. in the production of the negative electrode.

(Example 25)
A battery cell of Example 25 was produced in the same manner as in Example 3, except that the roll for rolling during press treatment was heated to 98° C. in producing the negative electrode.

(Example 26)
A battery cell of Example 26 was fabricated in the same manner as in Example 3, except that in fabricating the negative electrode, the roll for rolling during pressing was heated to 108° C. and the number of presses was 5 cycles.

(Example 27)
A battery cell of Example 27 was fabricated in the same manner as in Example 3, except that in fabricating the negative electrode, the roll for rolling during press treatment was heated to 115° C. and the number of press cycles was 5.

(Example 28)
A battery cell of Example 28 was produced in the same manner as in Example 1, except that the roll for rolling during press treatment was heated to 89° C. in the production of the negative electrode.

(Example 29)
A battery cell of Example 29 was produced in the same manner as in Example 1, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 30)
A battery cell of Example 30 was produced in the same manner as in Example 2, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 31)
A battery cell of Example 31 was produced in the same manner as in Example 3, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 32)
A battery cell of Example 32 was produced in the same manner as in Example 4, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 33)
A battery cell of Example 33 was produced in the same manner as in Example 5, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 34)
A battery cell of Example 34 was produced in the same manner as in Example 3, except that silicon oxide was used as the negative electrode active material.

(Example 35)
A battery cell of Example 35 was produced in the same manner as in Example 3, except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 36)
A battery cell of Example 36 was produced in the same manner as in Example 3, except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 37)
Conducted in the same manner as in Example 3, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=20:10:70 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 37 was fabricated.

(Example 38)
Conducted in the same manner as in Example 3, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=30:10:60 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 38 was fabricated.

(Example 39)
Conducted in the same manner as in Example 3, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=20:20:60 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 39 was fabricated.

(Example 40)
The battery cell of Example 40 was prepared in the same manner as in Example 3, except that the non-aqueous solvent of the non-aqueous electrolyte solution had a volume ratio of EC:EMC=30:70. made.

(Example 41)
The battery cell of Example 41 was prepared in the same manner as in Example 3, except that the volume ratio of EC:EMC=20:80 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 42)
The battery cell of Example 42 was prepared in the same manner as in Example 3, except that the volume ratio of EC:EMC=10:90 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 43)
Conducted in the same manner as in Example 3, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=40:10:50 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 43 was fabricated.

(Example 44)
Performed in the same manner as in Example 3, except that the volume ratio of FEC, PC, and EMC was set to FEC:PC:EMC=10:10:80 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 44 was fabricated.

(Comparative example 1)
A battery cell of Comparative Example 1 was produced in the same manner as in Example 1, except that the roll for rolling during press processing was heated to 43° C. in the production of the positive electrode.

(Comparative example 2)
A battery cell of Comparative Example 2 was produced in the same manner as in Example 1, except that in the production of the positive electrode, the rolling rolls during pressing were heated to 110° C. and the number of pressing was 3 cycles.

(Comparative Example 3)
A battery cell of Comparative Example 3 was produced in the same manner as in Comparative Example 1, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

A battery cell of Comparative Example 4 was produced in the same manner as in Comparative Example 2, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

Regarding the positive electrodes and negative electrodes used in Examples 2 to 36 and Comparative Examples 1 to 4, the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured in the same manner as in Example 1. The ratio Ra was measured and its ratio, Rc1/Ra, was calculated. Further, the density dc1 of the positive electrode active material layer, the amount Lc1 supported per unit area, and the porosity Pc1 were also measured in the same manner as in Example 1. The results are shown in Table 1 together with the results in Example 1.

(Example 45)
(Preparation of positive electrode)
95 parts by weight of LiNi _0.85 Co _0.10 Al _0.05 O ₂ as a positive electrode active material, 3.0 parts by weight of PVDF (HSV-800) as a binder, and carbon black (Super- 2.0 parts by weight of P) was weighed and dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm and dried at a temperature of 120° C. for 30 minutes to remove the solvent. After that, press treatment was performed at a linear pressure of 1500 kgf/cm using a roll press apparatus in which rolling rolls were heated to 81°C. One cycle was air cooling after press treatment. After performing three cycles of press treatment, a positive electrode was produced by punching into an electrode size of 18 mm×22 mm using a die.

The reflectance Rc2 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrophotometer (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The Rc2 of the obtained positive electrode was 3.5% using the average of three measurements.

The obtained positive electrode was cut into a square of 10 cm ^{2 ,} and the density dc2 of the positive electrode active material layer, the amount of support per unit area Lc2, and the porosity Pc2 were calculated. 0 mg/cm ² , Pc2=23.0%.

A battery cell of Example 45 was produced in the same manner as in Example 1, except that the positive electrode described above was used. The ratio of reflectance Ra to Rc2 at a wavelength of 550 nm on the surface of the negative electrode active material layer was Rc2/Ra0.44.

(Example 46)
A battery cell of Example 46 was produced in the same manner as in Example 45, except that the roll for rolling during press treatment was heated to 88° C. in the production of the positive electrode.

(Example 47)
A battery cell of Example 47 was produced in the same manner as in Example 45, except that the roll for rolling during press treatment was heated to 91° C. in the production of the positive electrode.

(Example 48)
A battery cell of Example 48 was produced in the same manner as in Example 45, except that the roll for rolling during press treatment was heated to 97° C. in the production of the positive electrode.

(Example 49)
A battery cell of Example 49 was produced in the same manner as in Example 45, except that the rolling roll used in the press treatment was set to 105° C. in producing the positive electrode.

(Example 50)
A battery cell of Example 50 was produced in the same manner as in Example 45, except that in the production of the positive electrode, the rolling roll was set at 105° C. and the number of press cycles was 3.

(Example 51)
A battery cell of Example 51 was produced in the same manner as in Example 45, except that the roll for rolling during press treatment was set to 72° C. in the production of the positive electrode.

(Example 52)
A battery cell of Example 52 was produced in the same manner as in Example 45, except that the roll for rolling during the press treatment was set to 118° C. and the number of press cycles was set to 5 in the production of the positive electrode.

(Example 53)
A battery cell of Example 53 was produced in the same manner as in Example 47, except that in the production of the positive electrode, the linear pressure during press treatment was set to 1000 kgf/cm.

(Example 54)
A battery cell of Example 54 was produced in the same manner as in Example 47, except that in the production of the positive electrode, the linear pressure during pressing was set to 1200 kgf/cm.

(Example 55)
A battery cell of Example 55 was produced in the same manner as in Example 47, except that in the production of the positive electrode, the linear pressure during pressing was set to 1400 kgf/cm.

(Example 56)
A battery cell of Example 56 was produced in the same manner as in Example 47, except that in the production of the positive electrode, the linear pressure during pressing was 1800 kgf/cm.

(Example 57)
A battery cell of Example 57 was produced in the same manner as in Example 47, except that the linear pressure during press treatment was set to 2000 kgf/cm in the production of the positive electrode.

(Example 58)
A battery cell of Example 58 was produced in the same manner as in Example 47, except that in the production of the positive electrode, the linear pressure during press treatment was set to 2500 kgf/cm.

(Example 59)
A battery cell of Example 59 was prepared in the same manner as in Example 47, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc2 per unit area was 11.0 mg/cm ² . made. The load Lc2 per unit area of the produced positive electrode was measured and found to be 11.0 mg/cm ² .

(Example 60)
A battery cell of Example 60 was prepared in the same manner as in Example 47, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc2 per unit area was 12.0 mg/cm ² . made. The loading amount Lc2 per unit area of the produced positive electrode was measured and found to be 12.2 mg/cm ² .

(Example 61)
A battery cell of Example 61 was prepared in the same manner as in Example 47, except that in the production of the positive electrode, the coating amount of the slurry was adjusted so that the supported amount Lc2 per unit area was 15.0 mg/cm ² . made. The loading amount Lc2 per unit area of the produced positive electrode was measured and found to be 14.9 mg/cm ² .

(Example 62)
A battery cell of Example 62 was fabricated in the same manner as in Example 47, except that in the production of the positive electrode, the coating amount of the slurry was adjusted so that the supported amount Lc2 per unit area was 16.0 mg/cm ² . made. The loading amount Lc2 per unit area of the produced positive electrode was measured and found to be 16.0 mg/cm ² .

(Example 63)
A battery cell of Example 63 was prepared in the same manner as in Example 47, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc2 per unit area was 20.0 mg/cm ² . made. The loading amount Lc2 per unit area of the produced positive electrode was measured and found to be 19.8 mg/cm ² .

(Example 64)
A battery cell of Example 64 was prepared in the same manner as in Example 47, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc2 per unit area was 24.0 mg/cm ² . made. The load Lc2 per unit area of the produced positive electrode was measured and found to be 24.0 mg/cm ² .

(Example 65)
A battery cell of Example 65 was fabricated in the same manner as in Example 47, except that in the production of the positive electrode, the coating amount of the slurry was adjusted so that the supported amount Lc2 per unit area was 24.5 mg/cm ² . made. The loading amount Lc2 per unit area of the produced positive electrode was measured and found to be 24.4 mg/cm ² .

(Example 66)
A battery cell of Example 66 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 21 was used.

(Example 67)
A battery cell of Example 67 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 22 was used.

(Example 68)
A battery cell of Example 68 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 23 was used.

(Example 69)
A battery cell of Example 62 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 24 was used.

(Example 70)
A battery cell of Example 70 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 25 was used.

(Example 71)
A battery cell of Example 71 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 26 was used.

(Example 72)
A battery cell of Example 72 was produced in the same manner as in Example 47, except that the negative electrode produced in Example 27 was used.

(Example 73)
A battery cell of Example 73 was produced in the same manner as in Example 45, except that the negative electrode produced in Example 28 was used.

(Example 74)
A battery cell of Example 74 was produced in the same manner as in Example 45, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 75)
A battery cell of Example 75 was produced in the same manner as in Example 46, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 76)
A battery cell of Example 76 was produced in the same manner as in Example 47, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 77)
A battery cell of Example 77 was produced in the same manner as in Example 48, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 78)
A battery cell of Example 78 was produced in the same manner as in Example 49, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 79)
A battery cell of Example 79 was produced in the same manner as in Example 45, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 80)
A battery cell of Example 80 was produced in the same manner as in Example 46, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 81)
A battery cell of Example 81 was produced in the same manner as in Example 47, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 82)
A battery cell of Example 82 was produced in the same manner as in Example 48, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 83)
A battery cell of Example 83 was produced in the same manner as in Example 49, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 84)
A battery cell of Example 84 was produced in the same manner as in Example 47, except that silicon oxide was used as the negative electrode active material.

(Example 85)
A battery cell of Example 85 was produced in the same manner as in Example 47, except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 86)
A battery cell of Example 86 was produced in the same manner as in Example 47, except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 87)
Performed in the same manner as in Example 47, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=20:10:70 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 87 was fabricated.

(Example 88)
Performed in the same manner as in Example 47, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 30:10:60 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 88 was fabricated.

(Example 89)
Performed in the same manner as in Example 47, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 20:20:60 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 89 was fabricated.

(Example 90)
The battery cell of Example 90 was used in the same manner as in Example 47, except that the volume ratio of EC:EMC=30:70 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 91)
The battery cell of Example 91 was used in the same manner as in Example 47, except that the volume ratio of EC:EMC=20:80 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 92)
The battery cell of Example 92 was used in the same manner as in Example 47, except that the volume ratio of EC and EMC was EC:EMC=10:90 as the nonaqueous solvent of the nonaqueous electrolyte solution. made.

(Example 93)
Performed in the same manner as in Example 47, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 40:10:50 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 93 was fabricated.

(Example 94)
Performed in the same manner as in Example 47, except that the volume ratio of FEC, PC, and EMC was set to FEC:PC:EMC = 10:10:80 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 94 was fabricated.

(Comparative Example 5)
A battery cell of Comparative Example 5 was produced in the same manner as in Example 41, except that the roll for rolling during press processing was heated to 45° C. in producing the positive electrode.

(Comparative Example 6)
A battery cell of Comparative Example 6 was produced in the same manner as in Example 41, except that in the production of the positive electrode, the roll for rolling during the press treatment was heated to 110° C. and the number of press cycles was 5.

(Comparative Example 7)
A battery cell of Comparative Example 7 was produced in the same manner as in Comparative Example 5, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Comparative Example 8)
A battery cell of Comparative Example 8 was produced in the same manner as in Comparative Example 6, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Comparative Example 9)
A battery cell of Comparative Example 9 was produced in the same manner as in Comparative Example 5, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Comparative Example 10)
A battery cell of Comparative Example 10 was produced in the same manner as in Comparative Example 6, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

Regarding the positive electrodes and negative electrodes used in Examples 46 to 86 and Comparative Examples 5 to 10, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured in the same manner as in Example 44. The ratio Ra was measured and its ratio, Rc2/Ra, was calculated. Further, the density dc2 of the positive electrode active material layer, the supported amount per unit area Lc2, and the porosity Pc2 were also measured in the same manner as in Example 45. The results are shown in Table 2 together with the results in Example 45.

(Example 95)
(Preparation of positive electrode)
88 parts by weight of LiFePO ₄ as a positive electrode active material, 6.0 parts by weight of PVDF (HSV-800) as a binder, and 6.0 parts by weight of carbon black (Super-P) as a conductive aid were weighed. and dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm and dried at a temperature of 120° C. for 30 minutes to remove the solvent. After that, press treatment was performed at a linear pressure of 1200 kgf/cm using a roll press apparatus in which rolling rolls were heated to 71°C. One cycle was air cooling after press treatment. After performing three cycles of press treatment, a positive electrode was produced by punching into an electrode size of 18 mm×22 mm using a die.

A reflectance Rc3 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrophotometer (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The Rc3 of the obtained positive electrode was 2.0% using the average of three measurements.

The obtained positive electrode was cut into a square of 10 cm ² , and the density dc3 of the positive electrode active material layer, the amount of support per unit area ^Lc3 , and the porosity Pc3 were calculated. 8 mg/cm ² , Pc3=23.0%.

A battery cell of Example 95 was produced in the same manner as in Example 1, except that the positive electrode described above was used. The ratio of reflectance Ra to Rc3 at a wavelength of 550 nm on the surface of the negative electrode active material layer was Rc3/Ra0.25.

(Example 96)
A battery cell of Example 96 was produced in the same manner as in Example 95, except that the roll for rolling during press treatment was heated to 78° C. in the production of the positive electrode.

(Example 97)
A battery cell of Example 97 was produced in the same manner as in Example 95, except that the roll for rolling during press treatment was heated to 81° C. in the production of the positive electrode.

(Example 98)
A battery cell of Example 98 was produced in the same manner as in Example 95, except that the roll for rolling during press treatment was heated to 87° C. in the production of the positive electrode.

(Example 99)
A battery cell of Example 99 was produced in the same manner as in Example 95, except that the roll for rolling during press treatment was set to 95° C. in producing the positive electrode.

(Example 100)
A battery cell of Example 100 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was set to 95° C. and the number of press cycles was set to 5 in fabricating the positive electrode.

(Example 101)
A battery cell of Example 101 was produced in the same manner as in Example 95, except that in the production of the positive electrode, the rolling roll was set at 108° C. and the number of press cycles was 5.

(Example 102)
A battery cell of Example 102 was produced in the same manner as in Example 97, except that in the production of the positive electrode, the linear pressure during pressing was 900 kgf/cm.

(Example 103)
A battery cell of Example 103 was produced in the same manner as in Example 97, except that in the production of the positive electrode, the linear pressure during press treatment was set to 1000 kgf/cm.

(Example 104)
A battery cell of Example 104 was produced in the same manner as in Example 97, except that in the production of the positive electrode, the linear pressure during press treatment was set to 1500 kgf/cm.

(Example 105)
A battery cell of Example 105 was produced in the same manner as in Example 97, except that in the production of the positive electrode, the linear pressure during press treatment was set to 1800 kgf/cm.

(Example 106)
A battery cell of Example 106 was fabricated in the same manner as in Example 97, except that in the production of the positive electrode, the coating amount of the slurry was adjusted so that the supported amount Lc3 per unit area was 7.7 mg/cm ² . made. The loading amount Lc3 per unit area of the produced positive electrode was measured and found to be 7.8 mg/cm ² .

(Example 107)
A battery cell of Example 107 was fabricated in the same manner as in Example 97, except that in the production of the positive electrode, the coating amount of the slurry was adjusted so that the amount Lc3 supported per unit area was 8.0 mg/cm ² . made. The loading amount Lc3 per unit area of the produced positive electrode was measured and found to be 8.0 mg/cm ² .

(Example 108)
A battery cell of Example 108 was prepared in the same manner as in Example 97, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc3 per unit area was 12.0 mg/cm ² . made. When the amount Lc3 supported per unit area of the produced positive electrode was measured, it was 12.1 mg/cm ² .

(Example 109)
A battery cell of Example 109 was prepared in the same manner as in Example 97, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc3 per unit area was 14.8 mg/cm ² . made. The loading amount Lc3 per unit area of the produced positive electrode was measured and found to be 15.0 mg/cm ² .

(Example 110)
A battery cell of Example 110 was prepared in the same manner as in Example 97, except that in the production of the positive electrode, the slurry coating amount was adjusted so that the supported amount Lc3 per unit area was 15.5 mg/cm ² . made. The loading amount Lc3 per unit area of the produced positive electrode was measured and found to be 15.3 mg/cm ² .

(Example 111)
A battery cell of Example 111 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 21 was used.

(Example 112)
A battery cell of Example 112 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 22 was used.

(Example 113)
A battery cell of Example 113 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 23 was used.

(Example 114)
A battery cell of Example 114 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 24 was used.

(Example 115)
A battery cell of Example 115 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 25 was used.

(Example 116)
A battery cell of Example 116 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 26 was used.

(Example 117)
A battery cell of Example 117 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 27 was used.

(Example 118)
A battery cell of Example 118 was produced in the same manner as in Example 95, except that the negative electrode produced in Example 28 was used.

(Example 119)
A battery cell of Example 119 was produced in the same manner as in Example 95, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 120)
A battery cell of Example 120 was produced in the same manner as in Example 96, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 121)
A battery cell of Example 121 was produced in the same manner as in Example 97, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 122)
A battery cell of Example 122 was produced in the same manner as in Example 98, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 123)
A battery cell of Example 123 was produced in the same manner as in Example 99, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 124)
A battery cell of Example 124 was produced in the same manner as in Example 95, except that LiVOPO ₄ was used as the positive electrode active material.

(Example 125)
A battery cell of Example 125 was produced in the same manner as in Example 96, except that LiVOPO ₄ was used as the positive electrode active material.

(Example 126)
A battery cell of Example 126 was produced in the same manner as in Example 97, except that LiVOPO ₄ was used as the positive electrode active material.

(Example 127)
A battery cell of Example 127 was produced in the same manner as in Example 98, except that LiVOPO ₄ was used as the positive electrode active material.

(Example 128)
A battery cell of Example 128 was fabricated in the same manner as in Example 99, except that LiVOPO ₄ was used as the positive electrode active material.

(Example 129)
A battery cell of Example 129 was produced in the same manner as in Example 97, except that silicon oxide was used as the negative electrode active material.

(Example 130)
A battery cell of Example 130 was produced in the same manner as in Example 97, except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 131)
A battery cell of Example 131 was produced in the same manner as in Example 97, except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 132)
Performed in the same manner as in Example 97, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC=20:10:70 as the nonaqueous solvent of the nonaqueous electrolyte solution. A battery cell of Example 132 was fabricated.

(Example 133)
Performed in the same manner as in Example 97, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 30:10:60 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 133 was fabricated.

(Example 134)
Performed in the same manner as in Example 97, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 20:20:60 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 134 was fabricated.

(Example 135)
The battery cell of Example 135 was used in the same manner as in Example 97, except that the volume ratio of EC:EMC=30:70 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 136)
The battery cell of Example 136 was used in the same manner as in Example 97, except that the volume ratio of EC:EMC=20:80 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 137)
The battery cell of Example 137 was prepared in the same manner as in Example 97, except that the volume ratio of EC:EMC=10:90 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. made.

(Example 138)
Conducted in the same manner as in Example 97, except that the volume ratio of EC, PC, and EMC was set to EC:PC:EMC = 40:10:50 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 138 was fabricated.

(Example 139)
Performed in the same manner as in Example 97, except that the volume ratio of FEC, PC, and EMC was set to FEC:PC:EMC = 10:10:80 as the nonaqueous solvent for the nonaqueous electrolyte solution. A battery cell of Example 139 was fabricated.

(Comparative Example 11)
A battery cell of Comparative Example 11 was produced in the same manner as in Example 95, except that the roll for rolling during press treatment was heated to 35° C. in producing the positive electrode.

(Comparative Example 12)
A battery cell of Comparative Example 12 was produced in the same manner as in Example 95, except that in the production of the positive electrode, the rolls for rolling during the press treatment were heated to 100° C. and the number of pressing was set to 5 cycles.

(Comparative Example 13)
A battery cell of Comparative Example 13 was produced in the same manner as in Comparative Example 11, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Comparative Example 14)
A battery cell of Comparative Example 14 was produced in the same manner as in Comparative Example 12, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Comparative Example 15)
A battery cell of Comparative Example 15 was produced in the same manner as in Comparative Example 11, except that LiVOPO ₄ was used as the positive electrode active material.

(Comparative Example 16)
A battery cell of Comparative Example 16 was produced in the same manner as in Comparative Example 12, except that LiVOPO ₄ was used as the positive electrode active material.

Regarding the positive electrodes and negative electrodes used in Examples 96 to 131 and Comparative Examples 11 to 16, the reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured in the same manner as in Example 95. The ratio Ra was measured and its ratio Rc3/Ra was calculated. Further, the density dc3 of the positive electrode active material layer, the supported amount per unit area Lc3, and the porosity Pc3 were also measured in the same manner as in Example 95. The results are shown in Table 3 together with the results in Example 95.

(Measurement of charging rate characteristics)
Using the fabricated battery cells of Examples 1 to 131 and Comparative Examples 1 to 16, charge rate characteristics were measured under the following conditions.

First, constant current charging is performed at a current density of 0.1 C until the voltage reaches 4.3 V (vs. Li/Li ⁺ ), and further until the current density drops to 0.05 C, 4.3 V (vs. Li /Li ⁺ ) was charged at a constant voltage.

After the end of constant voltage charging, after resting for 5 minutes, constant current discharge is performed at a current density of 0.1 C until the voltage reaches 2.5 V (vs. Li/Li ⁺ ), and the initial charge and discharge is performed. rice field.

After the initial charge/discharge, constant current charge is performed at a current density of 0.2 C until the voltage reaches 4.3 V (vs. Li/Li ⁺ ), and further until the current density drops to 0.05 C, 4.3 V ( vs. Li/Li ⁺ ), and the charge capacity at 0.2C was measured.

After measuring the charge capacity at 0.2 C, after resting for 5 minutes, constant current discharge is performed at a current density of 0.1 C until the voltage reaches 2.5 V (vs. Li/Li ⁺ ), and the battery cell is discharged. and

The battery cell in the discharged state is charged at a constant current at a current density of 2.0 C until the voltage reaches 4.3 V (vs. Li/Li ⁺ ), and then the current density is 4.3 V until the current density drops to 0.05 C. Constant voltage charging was performed at (vs. Li/Li ⁺ ), and the charge capacity at 2.0C was measured.

The ratio of the charge capacity at 2.0 C to the charge capacity at 0.2 C was calculated as the charge rate characteristic using the formula (Equation 1), and the charge rate characteristic was evaluated.
(Number 1)
Charge rate characteristics (%) = (charge capacity at 2.0C/charge capacity at 0.2C) * 100 (1)

(Measurement of load discharge characteristics)
Using the fabricated battery cells of Examples 1 to 131 and Comparative Examples 1 to 16, load discharge characteristics were measured under the following conditions.

First, constant current charging is performed at a current density of 0.1 C until the voltage reaches 4.3 V (vs. Li/Li ⁺ ), and further until the current density drops to 0.05 C, 4.3 V (vs. Li /Li ⁺ ) was charged at a constant voltage.

After the end of constant voltage charging, after resting for 5 minutes, constant current discharge is performed at a current density of 0.1 C until the voltage reaches 2.5 V (vs. Li/Li ⁺ ), and the initial charge and discharge is performed. rice field.

After the initial charge/discharge, constant current charge is performed at a current density of 0.2 C until the voltage reaches 4.3 V (vs. Li/Li ⁺ ), and further until the current density drops to 0.05 C, 4.3 V ( vs. Li/Li ⁺ ), constant voltage charging was performed.

After charging and resting for 5 minutes, constant current discharge was performed at a current density of 0.2C until the voltage reached 2.5V (vs. Li/Li ⁺ ), and the discharge capacity at 0.2C was measured.

After measuring the discharge capacity and resting for 5 minutes, the battery cell in the discharged state was charged at a current density of 2.0 C until the voltage reached 4.3 V (vs. Li/Li ⁺ ). Constant voltage charging was performed at 4.3 V (vs. Li/Li ⁺ ) until the density decreased to 0.05C.

After charging and resting for one minute, constant current discharge was performed at a current density of 2.0 C until the voltage reached 2.5 V (vs. Li/Li ⁺ ), and the discharge capacity at 2.0 C was measured.

The ratio of the discharge capacity at 2.0 C to the discharge capacity at 0.2 C was calculated as the load discharge characteristic by the formula (Equation 2), and the load discharge characteristic was evaluated.
(Number 2)
Load discharge characteristics (%) = (discharge capacity at 2.0C/discharge capacity at 0.2C) * 100 (2)

Table 1 shows the results of the charge rate characteristics and load discharge characteristics of the battery cells of Examples 1 to 36 and Comparative Examples 1 to 4, and the charge rate characteristics and load discharge characteristics of the battery cells of Examples 45 to 86 and Comparative Examples 5 to 10. Table 2 shows the results of the characteristics, and Table 3 shows the results of the charge rate characteristics and the load discharge characteristics of the battery cells of Examples 95 to 131 and Comparative Examples 11 to 16, respectively.

As shown in Table 1 from the results of Examples 1 to 7 and Comparative Examples 1 and 2, the positive electrode having a reflectance Rc1 of 2.0 ≤ Rc1 ≤ 12.0% at a wavelength of 550 nm on the surface of the positive electrode active material layer. It was confirmed that the charge rate characteristics and the load discharge characteristics were greatly improved by using .

In particular, as shown by the results of Examples 1 to 5, the compound represented by the general formula (1) was used as the positive electrode active material, and the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer was 8.0 ≤ It was confirmed that a particularly high charge rate characteristic was exhibited by setting Rc1≦12.0%. Further, as shown by the results of Examples 29 to 33 and Comparative Examples 3 and 4, similar results were obtained even when different compounds represented by the general formula (1) were used as the positive electrode active material. did.

The results of Examples 8 to 20 show that the density dc1 of the positive electrode active material layer, the loading amount Lc1 of the positive electrode active material layer, and the porosity Pc1 of the positive electrode active material layer each contribute to the charge rate characteristics. It can be seen that the charge rate characteristics are particularly improved in each specific range.

Furthermore, from the results of Examples 21 to 28, Rc/Ra, which is the ratio of the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc on the surface of the positive electrode active material layer, is controlled within a specific range. It can be seen that a lithium ion secondary battery exhibiting high charge rate characteristics can be obtained by this. Also, from the results of Examples 34 to 36, it can be seen that high charging rate characteristics are exhibited by using a carbon material as the negative electrode active material.

In addition, the battery cells evaluated for charge rate characteristics and the battery cells of Examples 1 to 36 and Comparative Examples 1 to 4 evaluated for load discharge characteristics were each dismantled in a glove box in an argon atmosphere after evaluation. , the positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured.

In Table 2, as shown by the results of Examples 45 to 52 and Comparative Examples 5 and 6, the positive electrode having a reflectance Rc2 of 2.0 ≤ Rc2 ≤ 12.0% at a wavelength of 550 nm on the surface of the positive electrode active material layer It was confirmed that the charge rate characteristics and the load discharge characteristics were greatly improved by using .

In particular, as shown by the results of Examples 45 to 50, the compound represented by the general formula (2) was used as the positive electrode active material, and the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer was 3.5 ≤ It was confirmed that particularly high load discharge characteristics are exhibited by setting Rc2≦7.8%. Further, as shown by the results of Examples 74 to 83 and Comparative Examples 7 to 10, similar results were obtained even when different compounds represented by the general formula (2) were used as the positive electrode active material. did.

From the results of Examples 53 to 65, it is shown that the density dc2 of the positive electrode active material layer, the loading amount Lc2 of the positive electrode active material layer, and the porosity Pc2 of the positive electrode active material layer each contribute to the load discharge characteristics. It can be seen that the load discharge characteristics are particularly improved in each specific range.

Furthermore, from the results of Examples 66 to 73, Rc/Ra, which is the ratio of the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc on the surface of the positive electrode active material layer, is controlled within a specific range. It can be seen that a lithium ion secondary battery exhibiting high load discharge characteristics can be obtained by this. In addition, from the results of Examples 84 to 86, it can be seen that the use of a carbon material as the negative electrode active material exhibits high load discharge characteristics.

In addition, the battery cells evaluated for charge rate characteristics and the battery cells of Examples 45 to 86 and Comparative Examples 5 to 10 evaluated for load discharge characteristics were each dismantled in a glove box in an argon atmosphere after evaluation. , the positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured.

In Table 3, as shown by the results of Examples 95 to 101 and Comparative Examples 11 and 12, the positive electrode having a reflectance Rc3 of 2.0 ≤ Rc3 ≤ 12.0% at a wavelength of 550 nm on the surface of the positive electrode active material layer It was confirmed that the charge rate characteristics and the load discharge characteristics were greatly improved by using .

In particular, as shown by the results of Examples 95 to 98, the compound represented by the general formula (3) was used as the positive electrode active material, and the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer was 2.0≦2.0. It was confirmed that particularly high load discharge characteristics are exhibited by setting Rc3≦5.8%. Further, as shown by the results of Examples 119 to 128 and Comparative Examples 13 to 16, similar results were obtained even when different compounds represented by the general formula (3) were used as the positive electrode active material. did.

The results of Examples 102 to 110 show that the density dc3 of the positive electrode active material layer, the loading amount Lc3 of the positive electrode active material layer, and the porosity Pc3 of the positive electrode active material layer each contribute to the load discharge characteristics. It can be seen that the load discharge characteristics are particularly improved in each specific range.

Furthermore, from the results of Examples 111 to 118, Rc3/Ra, which is the ratio of the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc3 on the surface of the positive electrode active material layer, is controlled within a specific range. It can be seen that a lithium ion secondary battery exhibiting high load discharge characteristics can be obtained by this. Further, from the results of Examples 129 to 131, it can be seen that high load discharge characteristics are exhibited by using a carbon material as the negative electrode active material.

In addition, the battery cells evaluated for charge rate characteristics and the battery cells of Examples 95 to 131 and Comparative Examples 11 to 16 evaluated for load discharge characteristics were each dismantled in a glove box in an argon atmosphere after evaluation. , the positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured.

In Table 4, ethylene carbonate (EC) is contained as a non-aqueous solvent, and its content is 10 to 30 vol. %, it was confirmed that the charge rate characteristics and the load discharge characteristics were improved. In Examples 38 to 45 using LiCoO ₂ which is the compound of general formula (1), the charge rate characteristics are particularly improved, and LiNi _0.85 Co _0.10 Al ₀ which is the compound of general formula (2) It was found that the load discharge characteristics were particularly improved in Examples 87 to 94 and Examples 132 to 139 using _.05 O ₂ or LiFePO ₄ which is the compound of general formula (3).

(Example 140)
The battery of Example 140 was prepared in the same manner as in Example 7, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 141)
The battery of Example 141 was prepared in the same manner as in Example 6, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 142)
The battery of Example 142 was prepared in the same manner as in Example 1, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 143)
The battery of Example 143 was prepared in the same manner as in Example 2, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 144)
The battery of Example 144 was prepared in the same manner as in Example 3, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 145)
The battery of Example 145 was prepared in the same manner as in Example 4, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 146)
The battery of Example 146 was prepared in the same manner as in Example 5, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 147)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Example 147 was produced in the same manner as in Example 51.

(Example 148)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Example 148 was produced in the same manner as in Example 45.

(Example 149)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Example 149 was produced in the same manner as in Example 49.

(Example 150)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Example 150 was produced in the same manner as in Example 50.

(Example 151)
A battery cell of Example 151 was produced in the same manner as in Example 150, except that in the production of the positive electrode, the roll for rolling was set to 109° C. in the press treatment, and the number of press cycles was set to 3 cycles.

(Example 152)
A battery cell of Example 152 was produced in the same manner as in Example 150, except that the roll for rolling during the press treatment was set to 113° C. and the number of press cycles was set to 5 in the production of the positive electrode.

(Example 153)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Example 153 was produced in the same manner as in Example 52.

(Example 154)
The battery of Example 154 was prepared in the same manner as in Example 95, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 155)
The battery of Example 155 was prepared in the same manner as in Example 97, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 156)
The battery of Example 156 was prepared in the same manner as in Example 98, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 157)
The battery of Example 157 was prepared in the same manner as in Example 99, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 158)
The battery of Example 158 was prepared in the same manner as in Example 100, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Example 159)
A battery cell of Example 159 was produced in the same manner as in Example 154, except that in the production of the positive electrode, the rolling roll was set to 100° C. and the number of press cycles was 3.

(Example 160)
The battery of Example 160 was prepared in the same manner as in Example 101, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Comparative Example 17)
A battery of Comparative Example 17 was prepared in the same manner as in Comparative Example 1, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Comparative Example 18)
A battery of Comparative Example 18 was prepared in the same manner as in Comparative Example 2, except that a mixture of 80% by mass of LiCoO ₂ as the positive electrode active material 1 and 20% by mass of LiFePO ₄ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Comparative Example 19)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Comparative Example 19 was produced in the same manner as in Comparative Example 9.

(Comparative Example 20)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A battery cell of Comparative Example 20 was produced in the same manner as in Comparative Example 10.

(Comparative Example 21)
A battery of Comparative Example 21 was prepared in the same manner as in Comparative Example 11, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

(Comparative Example 22)
A battery of Comparative Example 22 was prepared in the same manner as in Comparative Example 12, except that a mixture of 80% by mass of LiFePO ₄ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material. A cell was produced.

Regarding the positive electrodes and negative electrodes used in Examples 140 to 160 and Comparative Examples 17 to 22, the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured in the same manner as in Example 1. The ratio Ra was measured and its ratio Rc/Ra was calculated. Further, the density dc of the positive electrode active material layer, the supported amount Lc per unit area, and the porosity Pc were also measured in the same manner as in Example 1. The results are shown in Table 5 together with the results in Example 95.

In Table 5, the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer, the density dc of the positive electrode active material layer, the amount Lc supported per unit area, and the porosity Pc of Examples 140 to 146 and Comparative Example 17 , 18 are Rc1, dc1, Lc1 and Pc1, respectively, because the compound represented by the general formula (1) is the main component. Examples 147 to 153 and Comparative Examples 19 and 20 are Rc2, dc2, Lc2 and Pc2, respectively, because the compound represented by the general formula (2) is the main component, and Examples 154 to 160 and Comparative Example 21 , 22 are represented by Rc3, dc3, Lc3 and Pc3, respectively, since the compound represented by the general formula (3) is the main component.

In Table 5, from the results of Examples 140 to 160 and Comparative Examples 17 to 22, even when compounds represented by different general formulas were mixed, the charge rate It was confirmed that the characteristics and load discharge characteristics are excellent. Further, from the results of Examples 140 to 147, when using the positive electrode containing the compound represented by the general formula (1) as a main component, 8.0 ≤ Rc1 ≤ 12.0% as in the results of Table 1 It was confirmed that high charge rate characteristics were exhibited in some cases. Similarly, when the positive electrode containing the compound represented by the general formula (2) as a component is used, high load discharge characteristics are obtained when 3.5 ≤ Rc2 ≤ 7.8%, similar to the results in Table 2. and when a positive electrode containing the compound represented by the general formula (3) as a component is used, high load discharge characteristics are exhibited when 2.0 ≤ Rc3 ≤ 5.8%, similar to the results in Table 3. was confirmed.

Moreover, by comparing Examples 140 to 146 and Examples 154 to 160, it was confirmed that either the charge rate characteristic or the load discharge characteristic was superior depending on the compound contained as the main component of the positive electrode active material. From this result, it can be seen that the reflectance at a wavelength of 550 nm on the surface of the positive electrode active material layer and the type of compound that is the main component of the positive electrode are related to the obtained characteristics.

ADVANTAGE OF THE INVENTION By this invention, it becomes possible to provide the positive electrode which can improve charge rate characteristics and load discharge characteristics, and a lithium ion secondary battery using the same. They are suitable for use as power sources for portable electronic devices, and are also used as electric vehicles and as storage batteries for domestic and industrial use.

10 Separator 20 Positive Electrode 22 Positive Electrode Current Collector 24 Positive Electrode Active Material Layer 30 Negative Electrode 32 Negative Electrode Current Collector 34 Negative Electrode Active Material Layer 40 Laminated Body 50 Case 52 Metal Foil 54 Polymer Film 60, 62 Lead 100 Lithium Ion Secondary Battery

Claims (13)

A positive electrode active material layer having a positive electrode active material, a conductive aid, and a binder on a positive electrode current collector,
Containing as a main component a compound represented by the following formula (1) as the positive electrode active material,
The reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer measured using a spectrophotometer is 8.0 ≤ Rc1 ≤ 12.0%,
The density dc1 of the positive electrode active material layer is 3.1 ≤ dc1 ≤ 4.1 g/ ^cm3 ,
The positive electrode, wherein the amount Lc1 supported per unit area in the positive electrode active material layer is 13.0≦Lc1≦25.0 mg/cm ² .
LixNiyM1 _{- yOz} ( ₁ ) _ _{_} _
(0<x≦1.1, 0≦y<0.5, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg) A positive electrode active material layer having a positive electrode active material, a conductive aid, and a binder on a positive electrode current collector,
containing as a main component a compound represented by the following formula (2) as the positive electrode active material,
The reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer measured using a spectrophotometer is 3.5 ≤ Rc2 ≤ 7.8% ,
The density dc2 of the positive electrode active material layer is 3.0≦dc2≦3.8 g/cm ³ ,
The positive electrode, wherein the amount Lc2 supported per unit area in the positive electrode active material layer is 12.0≦Lc2≦24.0 mg/cm ² .
_{LixNiyM1 - yOz} ( ₂ )
(0<x≦1.1, 0.5≦y≦1, 1.9≦z≦2.1, and M is at least one selected from Co, Mn, Al, Fe, and Mg) A positive electrode active material layer having a positive electrode active material, a conductive aid, and a binder on a positive electrode current collector,
Containing as a main component a compound represented by the following formula (3) as the positive electrode active material,
The reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer measured using a spectrophotometer is 2.0 ≤ Rc3 ≤ 5.8% ,
The density dc3 of the positive electrode active material layer is 1.8≦dc3≦2.5 g/cm ³ ,
The positive electrode, wherein the amount Lc3 supported per unit area in the positive electrode active material layer is 8.0≦Lc3≦15.0 mg/cm 2 ^.
_{LixMyOzPO4 ( 3} )
(0 < x ≤ 1.1, 0 < y ≤ 1.1, 0 ≤ z ≤ 1.0, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, V have) The positive electrode according to any one of claims 1 to 3, wherein the conductive aid is carbon black. The positive electrode according to any one of claims 1 to 4, wherein the binder is polyvinylidene fluoride (PVDF). A positive electrode according to claim 1, a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
A lithium ion secondary battery, wherein a reflectance Ra at a wavelength of 550 nm measured using a spectrophotometer on the surface of the negative electrode active material layer is 7.5≦Ra≦16.0%. 7. The lithium ion secondary battery according to claim 6 , wherein a ratio Rc1/Ra between said reflectance Rc1 and said reflectance Ra satisfies 1.00<Rc1/Ra≦1.53. A positive electrode according to claim 2 , a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
A lithium ion secondary battery, wherein a reflectance Ra at a wavelength of 550 nm measured using a spectrophotometer on the surface of the negative electrode active material layer is 7.5≦Ra≦16.0%. 9. The lithium ion secondary battery according to claim 8 , wherein a ratio Rc2/Ra between said reflectance Rc2 and said reflectance Ra satisfies 0.29≦Rc2/Ra<1.00. A positive electrode according to claim 3 , a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
A lithium ion secondary battery, wherein a reflectance Ra at a wavelength of 550 nm measured using a spectrophotometer on the surface of the negative electrode active material layer is 7.5≦Ra≦16.0%. 11. The lithium ion secondary battery according to claim 10 , wherein a ratio Rc3/Ra between said reflectance Rc3 and said reflectance Ra satisfies 0.13≤Rc3/Ra≤0.75. The lithium ion secondary battery according to any one of claims 6 to 11 , wherein said negative electrode active material contains a carbon material having a graphite structure. The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte, the non-aqueous solvent contains ethylene carbonate, and the content of the ethylene carbonate is 10 to 30 vol. %, the lithium ion secondary battery according to any one of claims 6 to 12 .

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