JP2007134218A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery using proton-containing nickel acid lithium, with high discharge capacity, and showing excellent cycle performance. <P>SOLUTION: In the nonaqueous electrolyte secondary battery provided with a cathode containing a cathode active material, an anode containing an anode active material, and nonaqueous electrolyte, the cathode active material is proton-containing nickel acid lithium expressed in a chemical formula: H<SB>x</SB>Li<SB>y</SB>Ni<SB>1-a</SB>M<SB>a</SB>O<SB>2</SB>(where, 0<x≤1, 0<y≤1, 1≤x+y≤2, 0<a≤0.5, and M is at least a kind selected from C0, Ti, V, Cr, Mn, Fe, Al, Cu, and Zn), and the anode active material is a non-graphite carbon material, with an active material ratio of mass of the anode active material to that of the cathode active material larger than 0.38. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery including a proton-containing lithium nickelate positive electrode active material and a non-graphitic carbon negative electrode active material.

Conventional technology

In recent years, small and lightweight lithium ion secondary batteries have been widely used as power sources for electronic devices such as mobile phones, PDAs, and digital cameras. Such electronic devices are remarkably multifunctional and have high energy density to replace LiCoO ₂ / C, LiNiO ₂ / C, and LiMn ₂ O ₄ / C based lithium ion secondary batteries currently used. Batteries are expected.

  Among various compounds, since the discharge capacity per unit mass is large, the use of nickel oxyhydroxide as a positive electrode active material of a nonaqueous electrolyte secondary battery has been studied. However, batteries using nickel oxyhydroxide have the disadvantage that the cycle performance is not good. This improvement in cycle performance has become a major issue for practical use, and a solution is awaited.

  Further, nickel oxyhydroxide does not contain lithium that contributes to the redox reaction. For this reason, it is conceivable to use metallic lithium or a lithium alloy as a negative electrode active material containing lithium combined with this, but the reversibility of these negative electrode active materials was not good.

  In addition, when a carbon material that is currently in practical use is used for the negative electrode active material, it was necessary to previously contain lithium in the carbon material in order to obtain a chargeable / dischargeable battery.

As a positive electrode active material of a non-aqueous electrolyte secondary battery, Patent Document 1 discloses a general formula A _x B _y MO _z (where 0 ≦ x ≦ 2, 0 ≦ y ≦ 2, 1.5 ≦ z ≦ 3, M = Mn Fe, Ni, Co, V, Cr or Sc, A and B are active materials represented by H, Li, Na, K, Cs, Ca, Mg and Rb, and mixtures thereof, and patent literature 2 proposes a compound represented by the general formula H _x A _1-x MO ₂ (where x = 0 to 0.99, A is an alkali metal of group 1a, M = Co, Ni). LiNiOOH is disclosed.

Further, Patent Document 4 discloses a method for producing a positive electrode active material in which an aqueous solution of lithium hydroxide is passed through nickel oxyhydroxide containing 10 mol% of cobalt and an ion exchange reaction between hydrogen ions and lithium ions is performed. In Patent Document 5, the chemical formula H _x Li _y Ni _1-a M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is Co , Ti, V, Cr, Mn, Fe, Al, Cu, and Zn) and the cycle performance of a cell using a proton-containing lithium nickelate positive electrode active material and a scaly graphite active material represented by ing.

  Regarding the negative electrode active material of the non-aqueous electrolyte secondary battery, Patent Document 6 discloses a technique of combining a non-graphite carbon material and lithium manganate as a positive electrode active material, and Patent Document 7 discloses non-graphitizable carbon. A technique for combining a material and a lithium nickel composite oxide as a positive electrode active material is disclosed.

  In the nonaqueous electrolyte secondary battery, the ratio of the weight of the positive electrode active material to the weight of the negative electrode active material is disclosed in Patent Document 8 in which a lithium transition metal oxide is used for the positive electrode active material and a carbon material is used for the negative electrode active material. In the case of 1.8 to 2.4 in the case, and Patent Document 9 discloses a technique of 1.3 to 2.2 when the lithium composite oxide is used for the positive electrode active material and the carbon material is used for the negative electrode active material. It is disclosed.

Furthermore, in the non-aqueous electrolyte secondary battery, the coating weight of the positive electrode mixture is disclosed in Patent Document 10 as LiCoO ₂ (content 89 wt% in the mixture) as the positive electrode active material and non-graphitizable carbon material as the negative electrode active material. In the technology of 0.6 to 1.1 g / 100 cm ² (positive electrode active material 5.34 to 9.79 mg / cm ² ) per side, and Patent Document 11, the spinel manganese compound is used as the positive electrode active material. When the non-graphitizable carbon material is used for the negative electrode active material, the positive electrode active material is set to 5.34 to 14.33 g / cm ² per side (2.67 to 7.12 mg / cm ² per side). Is disclosed.
Japanese Patent Laid-Open No. 06-349494 Japanese Patent No. 3263882 JP 2000-323174 A JP 2000-123836 A Japanese Patent Application No. 2005-132069 JP 2001-176499 A Japanese Patent Laid-Open No. 2000-200264 JP 2003-242966 A JP 2004-342500 A JP 2002-151157 A JP 2005-243448 A

There is no description about the cycle performance of the nonaqueous electrolyte secondary batteries described in Patent Documents 1, 2, and 3, and it has been unclear whether the cycle performance is improved when these compounds are used as the positive electrode active material. .

  Moreover, in patent document 4, although the cycle performance of a positive electrode active material is examined, the effect at the time of combining with negative electrode active materials other than metallic lithium was unknown. Further, in Patent Document 5, the type of the carbon material of the negative electrode active material combined with the positive electrode active material has not been examined in detail, and the influence of the ratio of the positive and negative electrode active materials on the cycle performance has not been known.

  Furthermore, Patent Document 6 uses a non-graphitic carbon material as a negative electrode active material, and Patent Document 7 uses a non-graphitizable carbon material as a negative electrode active material. It is not considered to combine with.

  Further, in Patent Document 8 and Patent Document 9, the ratio of the weight of the positive electrode active material to the weight of the negative electrode active material is examined, but proton-containing lithium nickelate is used as the positive electrode active material and non-graphite type is used as the negative electrode active material. The use of carbon materials has not been studied.

  Furthermore, Patent Document 10 and Patent Document 11 describe the coating weight of the positive electrode active material, but none of them uses proton-containing lithium nickelate as the positive electrode active material.

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery using a proton-containing lithium nickelate as a positive electrode active material and having a large discharge capacity and excellent cycle performance.

The invention of claim 1 is a nonaqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a nonaqueous electrolyte, wherein the positive electrode active material has the chemical formula H _x Li _y Ni _{1. -A} M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is Co, Ti, V, Cr, Mn, Fe, Al, Cu And at least one selected from Zn), the negative electrode active material is a non-graphitic carbon material, and the active material ratio of the mass of the negative electrode active material to the mass of the positive electrode active material Is greater than 0.38.

According to a second aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the first aspect, the coating mass of the positive electrode active material on one side of the current collector is in the range of 5.3 to 7.3 mg / cm ^2. Features.

  In the present invention, by using proton-containing lithium nickelate as the positive electrode active material, a non-aqueous electrolyte secondary battery having a large discharge capacity per unit mass can be obtained. Moreover, a nonaqueous electrolyte secondary battery having excellent cycle performance can be obtained by combining this positive electrode active material and a non-graphite carbon material as a negative electrode active material.

  Furthermore, by making the active material ratio of the mass of the negative electrode active material to the mass of the positive electrode active material larger than 0.38, the negative electrode can have a sufficient lithium reserve capacity, and the discharge capacity with excellent cycle performance can be obtained. A large non-aqueous electrolyte secondary battery can be obtained.

In addition, the non-aqueous electrolyte having a large discharge capacity per weight and excellent cycle performance can be obtained by setting the mass of the positive electrode active material applied to one side of the current collector in the range of 5.3 to 7.3 mg / cm ^2. A secondary battery can be obtained.

The positive electrode active material used in the present invention has the chemical formula H _x Li _y Ni _1-a M _a O ₂ (0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M Is a proton-containing lithium nickelate represented by at least one selected from Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn), and the method for producing the nickel oxyhydroxide contains lithium ions An electrochemical method in which an anode is energized in an electrolyte or another known method may be used. As a production method of the present invention, a method of bringing nickel hydroxide into contact with a solution containing lithium ions is more preferable.
The reason is that when x is larger than 1, a stable crystal structure cannot be maintained, and when y is larger than 1, the discharge behavior is considered to be two or more stages, and the cycle performance is considered to deteriorate. Further, if x + y is smaller than 1, a substantial discharge capacity cannot be obtained, and if it is larger than 2, it is considered that a stable crystal structure cannot be maintained. Further, if a is larger than 0.5, a solid solution cannot be formed with nickel, and it is considered that impurities such as hydroxide are generated. Furthermore, M is at least one selected from Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn, because nickel forms a solid solution with these elements and maintains a stable crystal structure. It is.

  In the present invention, proton-containing lithium nickelate is used as the positive electrode active material, and a non-graphitic carbon material is used as the negative electrode active material. And the active material ratio of the mass of the negative electrode active material with respect to the mass of a positive electrode active material is made larger than 0.38. This is because non-graphitic carbon materials do not have a clear stage, and are considered to have more sites where lithium is occluded than graphite materials. Therefore, the negative electrode has a large theoretical capacity. Furthermore, as described later, in order to obtain a battery having excellent cycle performance, the proton-containing lithium nickelate positive electrode needs to have a sufficient lithium reserve capacity in the negative electrode.

Furthermore, it is preferable that the single-sided coating mass of the positive electrode active material used for this invention is 5.3-7.3 mg / cm < ² >. When it is less than 5.3 mg / cm ² , the mass energy density of the battery is remarkably reduced, which is not practical. On the other hand, when the amount is more than 7.3 mg / cm ^2, the diffusion of lithium ions in the positive electrode is delayed, and the polarization gradually increases with the increase in the number of cycles, so that sufficient cycle performance cannot be obtained. .

  The negative electrode active material used in the present invention is a non-graphite carbon material and can be obtained by a method of firing petroleum pitch, polyacene, polyparaphenylene, polyfurfuryl alcohol, polysiloxane, and the like. Furthermore, among non-graphitic carbon materials, non-graphitizable carbon is preferable. The reason for this is that the graphite material occludes lithium in the stage between the carbon nets, whereas the non-graphitizable carbon does not have a clear stage, so the site where lithium is occluded compared to the graphite material. Since it is considered to have many, non-graphitizable carbon can constitute a negative electrode having a larger theoretical capacity than graphite carbon.

  Non-graphitizable carbon is a non-graphitic carbon material that cannot be converted to graphite even when heated to an ultra-high temperature of around 3300K under normal pressure or reduced pressure (Carbon Glossary, Carbon Materials Association, Carbon Glossary) Editorial Committee). In particular, among non-graphitizable carbons, it is preferable to use non-graphitizable carbons having a surface spacing d002 value in the C-axis direction obtained by an X-ray diffraction method of 0.36 nm or more and 0.40 nm or less. The reason for this is that when the interplanar spacing d002 value is less than 0.36 nm, the charge acceptability is significantly reduced, and when the interplanar spacing d002 value exceeds 0.40 nm, the true density of the carbon material becomes too small. Since the energy density of a battery becomes small, it is not preferable.

  Binders used when producing positive and negative electrodes include ethylene-propylene-diene terpolymer, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, and polyvinylidene fluoride. , Polyethylene, polypropylene, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, styrene-butadiene rubber (SBR) or carboxymethylcellulose (CMC). Can be used.

  As the solvent used when mixing the binder, either a non-aqueous solvent or an aqueous solution can be used. As the non-aqueous solvent, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be used. On the other hand, a dispersing agent, a thickener, etc. can be added and used for aqueous solution.

  Iron, copper, stainless steel, nickel, and aluminum can be used as the current collector of the electrode. Moreover, a sheet | seat, a foam, a mesh, a porous body, an expanded lattice, etc. can be used as the shape. Further, the current collector can be used with a hole formed in an arbitrary shape.

  As an organic solvent used in the electrolytic solution, ethylene carbonate, propylene carbonate, butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran , 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methylpropyl carbonate, etc., alone or in combination Can be used. Also, carbonate compounds such as vinylene carbonate and butylene carbonate, benzene compounds such as biphenyl and cyclohexylbenzene, and sulfur compounds such as propane sultone can be used alone or in the electrolyte.

Furthermore, it can use combining electrolyte solution and a solid electrolyte. As the solid electrolyte, a crystalline or amorphous inorganic solid electrolyte can be used. The former includes LiI, Li ₃ N, Li _{1 + x} M _x Ti _2-x (PO ₄ ) ₃ (M = Al, Sc, Y, La), Li _0.5-3x R _{0.5 + x} TiO ₃ (R = La, Pr, Nd, Sm), or thio LISICON represented by Li _4-x Ge _1-x P _x S ₄ can be used, the latter being LiI-Li ₂ O—B ₂ O ₅ system, Li _{A 2} O—SiO ₂ system, a LiI—Li ₂ S—B ₂ S ₃ system, a LiI—Li ₂ S—SiS ₂ system, a Li ₂ S—SiS ₂ —Li ₂ PO ₄ system, or the like can be used.

Examples of the salt dissolved in the organic solvent include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF (CF ₃ ) ₅ , LiPF ₂ (CF ₃ ) ₄ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₄ (CF ₃ ). ₂ , LiPF ₅ (CF ₃ ), LiPF ₃ (C ₂ F ₅ ) ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ , LiN (COCF ₂ CF ₃ ) ₂ , LiC ₄ BO ₈ or the like can be used alone or in combination. Among these, LiPF ₆ is preferable as the lithium salt because the cycle performance is good. Furthermore, the concentration of these lithium salts is preferably in the range of 0.5 to 2.0 mol / dm ³ .

  A microporous membrane such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, and polyolefin can be used as a separator for a nonaqueous electrolyte secondary battery.

  The shape of the nonaqueous electrolyte secondary battery is not particularly limited, and a rectangular shape, an elliptical shape, a coin shape, a button shape, a sheet shape, and the like can be used.

  Below, this invention is demonstrated in detail based on an Example. However, the present invention is not limited to the following examples.

[Examples 1 to 7 and Comparative Examples 1 and 2]
[Example 1]
Nickel hydroxide (Ni _0.76 Co _0.24 (OH) ₂ ) (5.0 g) in which 24 mol% of nickel was replaced with cobalt (123 ml) was added at 7.0 ° C. to 7.0 mol / dm ³ lithium hydroxide aqueous solution at 80 ° C. Then, 43 ml of 12% sodium hypochlorite was added, and the mixture was kept at 80 ° C. and stirred for 3 hours. After filtration, 21 ml of a 14.0 mol / dm ³ lithium hydroxide aqueous solution was added, and 0.5 ml was added. After stirring for a period of time, it was filtered and dried at 65 ° C. to obtain proton-containing lithium nickelate (Ni _0.76 Co _0.24 OOH _0.2 Li _0.8 ) powder.

89% by mass of this powder as a positive electrode active material, 4% by mass of acetylene black as a conductive auxiliary agent, and 7% by mass of polyvinylidene fluoride (PVDF) as a binder were mixed in N-methyl-2-pyrrolidone (NMP). A paste was prepared. This paste is applied onto an aluminum foil having a thickness of 20 μm, dried at 150 ° C. under reduced pressure, pressed with a roller and pressed to a porosity of 35%, and a slitter of 30 mmW × 40 mmL in size. Thus, a positive electrode A1 having a mass of 6.29 mg / cm ² applied to one surface of the current collector of the positive electrode active material was manufactured.

Next, 94% by mass of non-graphitizable carbon having an interplanar spacing d002 value of 0.3780 nm as a negative electrode active material and 6% by mass of PVDF as a binder were mixed in NMP to prepare a paste. This paste is applied to a 14 μm copper foil, dried under reduced pressure at 150 ° C., pressed to a porosity of 38%, and adjusted to a size of 30 mmW × 40 mmL with a slitter to collect the negative electrode active material. A negative electrode A2 having a coating mass of 3.29 mg / cm ^{2 on} one surface of the electric conductor was obtained.

  A positive electrode A1 and a negative electrode A2 having the same application area of the active material of the positive electrode and the negative electrode are stacked with a polyethylene separator which is a microporous film having a thickness of 20 μm and a porosity of 40% interposed therebetween, and is 70 mm high and 34 mm wide. The battery A of the non-aqueous electrolyte secondary battery of the present invention having a rated capacity of 8.0 mAh was obtained by inserting it into a 1 mm-thick container and injecting a non-aqueous electrolyte therein.

As the non-aqueous electrolyte of this battery, a solution obtained by dissolving 1 mol / dm ³ of LiPF ₆ in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 1 was used.

[Example 2]
The positive electrode B1 of the coating amount 7.30 mg / cm ² to the collector side of the positive electrode active material, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode B2 of 2.78mg / cm ² A battery B of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1 except for the above.

[Example 3]
The coating amount of the current collector side of the positive electrode active material is 6.91mg / cm ² of the positive electrode C1, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode C2 of 3.22mg / cm ² A battery C of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1 except for the above.

[Example 4]
The coating amount 6.49mg / cm ² of the positive electrode D1 to the collector side of the positive electrode active material, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode D2 of 3.32mg / cm ² A battery D of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1 except for the above.

[Example 5]
The positive electrode E1 of coating amount 5.30mg / cm ² to the collector side of the positive electrode active material, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode E2 of 4.23mg / cm ² A battery E of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1 except for the above.

[Example 6]
The coating amount of the current collector side of the positive electrode active material a positive electrode F1 of 5.22mg / cm ^2, the coating weight of the current collector one surface of the negative electrode active material to prepare a negative electrode F2 of 4.42mg / cm ² A battery F of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1 except for the above.

[Example 7]
The coating amount of the current collector side of the positive electrode active material a positive electrode G1 of 7.41mg / cm ^2, the coating weight of the current collector one surface of the negative electrode active material to prepare a negative electrode G2 of 3.51mg / cm ² Except for the above, a battery G of the nonaqueous electrolyte secondary battery of the present invention was obtained in the same manner as Example 1.

[Comparative Example 1]
The positive electrode H1 of coating amount 5.29 mg / cm ² to the collector side of the positive electrode active material, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode H2 of 2.00 mg / cm ² A battery H of a nonaqueous electrolyte secondary battery was produced in the same manner as Example 1 except for the above.

[Comparative Example 2]
The positive electrode I1 of coating amount 7.35 mg / cm ² to the collector side of the positive electrode active material, the coating amount of the current collector one surface of the negative electrode active material to prepare a negative electrode I2 of 2.75 mg / cm ² A battery I of a nonaqueous electrolyte secondary battery was produced in the same manner as Example 1 except for the above.

  The nonaqueous electrolyte secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were subjected to a cycle test under the following conditions. The temperature was 25 ° C., and charging was performed at a constant current of 0.2 CmA up to 4.2 V, and further at a constant voltage of 4.2 V for a total of 8 hours, and then at a constant current of 0.2 CmA up to 1.5 V. Charging / discharging was performed 300 cycles.

  The ratio of the discharge capacity at the 300th cycle to the discharge capacity at the first cycle was defined as “discharge capacity retention ratio (%)” (calculated by Formula 1). The active material ratio of the mass of the negative electrode active material relative to the mass of the positive electrode active material was defined as “active material ratio” (calculated by Formula 2).

Discharge capacity maintenance rate (%) = 100 × 300th cycle discharge capacity (mAh) / 1st cycle discharge capacity (mAh) (Equation 1)
Active material ratio = mass of negative electrode active material (mg / cm ² ) / mass of positive electrode active material (mg / cm ² ) (Formula 2)
Table 1 summarizes the contents and cycle test results of the nonaqueous electrolyte secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 and 2.

  Furthermore, as an example of a charge / discharge curve, the charge / discharge curve of the first cycle and the discharge curve of the second cycle of the battery D of Example 4 are shown in FIG.

  From Table 1, it was found that the battery obtained in the present invention has excellent cycle performance. Further, as shown in FIG. 1, in the battery of the present invention, the discharge capacity at the second cycle was larger than that at the first cycle. The reason is not clear, but this phenomenon is unique to proton-containing lithium nickelate. Therefore, since it is necessary for the negative electrode to have a sufficient lithium reserve capacity, it is considered that the active material ratio needs to be larger than 0.38.

Furthermore, if the positive electrode active material is too small than 5.3 mg / cm ² , sufficient battery capacity cannot be obtained, and if the positive electrode active material is more than 7.3 mg / cm ² , the lithium in the electrode It was found that the cycle performance deteriorates slightly because the diffusion of ions slows and the polarization gradually increases as the number of cycles increases.

The proton-containing lithium nickelate (Ni _0.76 Co _0.24 OOH _0.2 Li _0.8 ) of Example 1 was changed from _x in the chemical formula (H _x Ni _y Ni _0.76 Co _0.24 O ₂ ) to 0. Even when y is changed to 0.1, 0.3, 0.5, 0.7, or 1 to 1, 0.3, 0.5, 0.7, or 1, the same as in the first embodiment The effect of was obtained.

  The same effect was obtained even when the amount of cobalt substituted for nickel was changed to 0.1, 1, 15, 30 or 50 mol%. Furthermore, even when the cobalt substituted for nickel was replaced with titanium, vanadium, chromium, manganese, iron, aluminum, copper, or zinc, the same effect as that obtained when the cobalt was replaced with cobalt in Example 1 was obtained.

The figure which shows the characteristic of the nonaqueous electrolyte secondary battery of Example 4 obtained by this invention.

Claims (2)

A positive electrode including a positive active material, a negative electrode including a negative active material, a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte, the positive electrode active material is the chemical formula _{H x Li y Ni 1-a} M a O 2 ( 0 <x ≦ 1, 0 <y ≦ 1, 1 ≦ x + y ≦ 2, 0 <a ≦ 0.5, M is at least one selected from Co, Ti, V, Cr, Mn, Fe, Al, Cu and Zn Wherein the negative electrode active material is a non-graphite carbon material, and the ratio of the active material mass to the positive electrode active material mass is greater than 0.38. A non-aqueous electrolyte secondary battery. ^2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the mass of the positive electrode active material applied to one side of the current collector is in the range of 5.3 to 7.3 mg / cm ² .

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