JP2016058214A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

A non-aqueous electrolyte secondary battery having both excellent input / output characteristics and high reliability is provided. A non-aqueous electrolyte secondary battery has a half-value width of a diffraction peak on the Miller index (003) plane obtained by powder X-ray diffraction of a positive electrode active material using CuKα rays is 0.06. ~ 0.1 deg. And the negative electrode active material using krypton gas as the adsorption gas has a BET specific surface area of 3.3 to 4.7 m 2 / g, and the total weight WP (mg) of the positive electrode active material contained in the positive electrode, The nonaqueous electrolyte secondary battery in which the ratio (WP / WN) of the total weight WN (mg) of the negative electrode active material contained in the battery is 1.2 to 1.6. [Selection] Figure 1

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (also called lithium secondary batteries) are lighter and have higher energy density than existing batteries. It is used. Particularly, lithium ion secondary batteries that are lightweight and obtain high energy density are preferably used as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). Yes.

JP 2000-195514 A JP 2014-011064 A

By the way, the non-aqueous electrolyte secondary battery (particularly a battery for a high output power source for driving a vehicle or the like) is required to satisfy both excellent input / output characteristics and high battery reliability. For example, a battery having a battery resistance of 6 mΩ or less and a battery temperature of about 110 ° C. or less during overcharging is preferable as the high-output power source for driving the vehicle.
Conventionally, for the purpose of improving input / output characteristics, for example, measures for reducing battery resistance by using positive and negative electrode active materials having a large specific surface area have been taken. However, since an active material having a large specific surface area has a large area in contact with the non-aqueous electrolyte, an exothermic reaction (decomposition reaction of the non-aqueous electrolyte) between the active material and the non-aqueous electrolyte during overcharge tends to proceed rapidly. There was a trade-off. Therefore, there is a demand for a technology that can realize both excellent input / output characteristics and high battery reliability at a high level. As technologies related to these, Patent Document 1 discloses that excellent output characteristics can be improved by using a positive electrode active material having a predetermined crystal structure, and Patent Document 2 inputs by using a negative electrode active material having a large specific surface area. It is described that the characteristics and thermal stability can be improved. However, depending on the use conditions of the battery (especially a battery for a high output power source for driving a vehicle, etc.), the improvement effect of the input / output characteristics and the battery reliability by these measures may not be sufficient.

  The present invention has been made in view of the above points, and its main object is a non-aqueous electrolyte secondary battery having excellent input / output characteristics and high reliability, more specifically, battery resistance. The object is to provide a non-aqueous electrolyte secondary battery having a battery temperature of 6 mΩ or less and an overcharged battery temperature of 110 ° C. or less.

The present inventors have made various studies to achieve the above object,
(1) Half width of diffraction peak on Miller index (003) plane obtained by powder X-ray diffraction of positive electrode active material using CuKα ray (hereinafter simply referred to as “(003) plane half of positive electrode active material) Price range)),
(2) BET specific surface area of the negative electrode active material when krypton gas is used as the adsorption gas (hereinafter, also simply referred to as “KrBET specific surface area of negative electrode active material”), and
(3) Ratio (W _P / W _N ) of the total weight W _P (mg) of the positive electrode active material contained in the positive electrode and the total weight W _N (mg) of the negative electrode active material contained in the negative electrode,
The present inventors have found that by reducing the battery resistance and suppressing the increase in battery temperature by combining a total of three parameters consisting of the above within a predetermined range, the present invention has been completed.

That is, according to the present invention, a nonaqueous electrolyte secondary battery comprising an electrode body having a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material, the nonaqueous electrolyte solution having all of the following features: A secondary battery is provided. That is, the non-aqueous electrolyte secondary battery provided by the present invention is
i) The half width of the diffraction peak on the Miller index (003) plane obtained by powder X-ray diffraction of the positive electrode active material using CuKα rays is 0.06 to 0.1 deg. Be
ii) the negative electrode active material using krypton gas as an adsorption gas has a BET specific surface area (KrBET specific surface area) of 3.3 m ² / g or more and 4.7 m ² / g or less; and iii) included in the positive electrode The ratio (W _P / W _N ) of the total weight W _P (mg) of the positive electrode active material to the total weight W _N (mg) of the negative electrode active material included in the negative electrode is 1.2 or more and 1.6 or less. ;
Is a non-aqueous electrolyte secondary battery.

According to the study by the present inventors, the battery resistance tends to decrease as the (003) plane half-value width of the positive electrode active material increases and the KrBET specific surface area of the negative electrode active material increases. ) Half width at half maximum is 0.06 deg. As described above, it was confirmed that a particularly excellent battery resistance reduction effect was exhibited when the negative electrode active material had a KrBET specific surface area of 3.3 m ² / g or more. A graph showing the effect of the combination of the (003) plane half-value width of the positive electrode active material and the KrBET specific surface area of the negative electrode active material on the battery resistance is shown in FIG.
In addition, as the (003) plane half-value width of the positive electrode active material is smaller and the KrBET specific surface area of the negative electrode active material is smaller, the increase in battery temperature during overcharge tends to be suppressed. 003) Plane half width is 0.1 deg. It has been confirmed by the present inventors that the battery temperature increase suppression effect is particularly excellent when the negative electrode active material has a KrBET specific surface area of 4.7 m ² / g or less. . FIG. 2 shows a graph showing the influence of the combination of the (003) plane half-value width of the positive electrode active material and the KrBET specific surface area of the negative electrode active material on the battery temperature during overcharge.
Furthermore, it was confirmed that by making the above W _P / W _N 1.2 or more and 1.6 or less, it is possible to exhibit a more excellent battery resistance reduction effect and a battery temperature increase suppression effect during overcharge.
Specifically, the (003) plane half width of the positive electrode active material, the KrBET specific surface area of the negative electrode active material, and the weight ratio (W _P / W _N ) of the positive and negative electrode active materials contained in the positive and negative electrodes are within the above ranges. Thus, it is possible to achieve both a battery resistance (typically 6 mΩ or less) suitable for use in a high power application and a battery temperature during overcharge (typically 110 ° C. or less). That is, according to the present invention, there is provided a non-aqueous electrolyte secondary battery that achieves both excellent input / output characteristics (particularly, reduction in battery resistance) and high reliability (particularly, suppression of increase in battery temperature during overcharge). Can do.

It is a graph which shows the relationship between the combination of (003) plane half value width (deg.) Of a positive electrode active material and the KrBET specific surface area (m < ² > / g) of a negative electrode active material, and battery resistance (m (omega | ohm)). It is a graph which shows the relationship between the battery temperature (degreeC) at the time of the overcharge and the combination of the (003) plane half value width (deg.) Of a positive electrode active material and the KrBET specific surface area (m < ² > / g) of a negative electrode active material. It is a table | surface which shows the result of having measured battery resistance (m (ohm)) about each battery from which the (003) plane half value width (deg.) Of a positive electrode active material and the KrBET specific surface area (m < ² > / g) of a negative electrode active material differ. The result of having measured the battery temperature (degreeC) at the time of overcharge about each battery from which the (003) plane half value width (deg.) Of a positive electrode active material and the KrBET specific surface area (m < ² > / g) of a negative electrode active material differ is shown. It is a table. The (003) plane half-value width (deg.) Of the positive electrode active material, the KrBET specific surface area (m ² / g) of the negative electrode active material, and the weight ratio (W _P / W _N ) of the positive and negative electrode active materials contained in the positive and negative electrodes It is a table | surface which shows the result of having measured battery resistance (mohm) and the battery temperature at the time of overcharge (degreeC) about each different battery. About each battery in which the (003) plane half-value width (deg.) Of the positive electrode active material, the KrBET specific surface area (m ² / g) of the negative electrode active material, and the tungsten concentration (W concentration (mass%)) in the positive electrode active material are different It is a table | surface which shows the result of having measured battery resistance (mohm) and the battery temperature (degreeC) at the time of overcharge. Battery resistance (mΩ) for each battery in which the (003) plane half-value width (deg.) Of the positive electrode active material and the content (mass%) of lithium difluorophosphate (LiPO ₂ F ₂ ) in the non-aqueous electrolyte are different It is a table | surface which shows the result of having measured. Measure the battery temperature (° C) during overcharge for each battery with different (003) half-width (deg.) Of the positive electrode active material and the content (mass%) of LiPO ₂ F ₂ in the non-aqueous electrolyte. It is a table | surface which shows the result. The (003) half-width (deg.) Of the positive electrode active material, the content (% by mass) of LiPO ₂ F ₂ in the non-aqueous electrolyte, and the weight W _P (mg) of the positive electrode active material contained in the positive electrode and the battery Results of measurement of battery resistance (mΩ) and battery temperature (° C.) during overcharge for each battery having a different ratio (W _L / W _P ) of the weight W _L (mg) of the non-aqueous electrolyte used in the construction It is a table | surface which shows. The (003) plane half-value width (deg.) Of the positive electrode active material, the content (mass%) of LiPO ₂ F ₂ in the non-aqueous electrolyte, and the tungsten concentration (W concentration (mass%)) in the positive electrode active material It is a table | surface which shows the result of having measured battery resistance (mohm) and the battery temperature at the time of overcharge (degreeC) about each different battery.

  Hereinafter, a preferred embodiment of the present invention will be described using a lithium ion secondary battery as an example. Note that matters other than matters specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the contents disclosed in the present specification and common general technical knowledge in the field. Further, the lithium ion secondary battery is an example, and the technical idea of the present invention is also applied to other non-aqueous electrolyte secondary batteries (for example, sodium ion secondary batteries) provided with other charge carriers (for example, sodium ions). Is done.

  In general, the lithium ion secondary battery disclosed herein includes an electrode body having a positive electrode and a negative electrode and a non-aqueous electrolyte contained in a battery case. In such a battery case, positive and negative terminals for external connection, a safety valve set to release the internal pressure when the internal pressure of the battery case rises above a predetermined level, and a non-aqueous electrolyte are injected. An inlet is provided. In addition, a current interruption device (Current Interrupt Device, CID) that operates when the internal pressure of the battery case increases may be provided inside the battery case. As a material of such a battery case, for example, a light metal material having good thermal conductivity such as aluminum, stainless steel, and nickel-plated steel is suitable.

  In the positive electrode, a positive electrode active material layer containing a positive electrode active material is formed along the longitudinal direction on one side or both sides (here, both sides) of a long positive electrode current collector. As the positive electrode current collector, for example, an aluminum foil or the like can be used.

  The positive electrode active material may be a material made of a lithium transition metal oxide having a layered structure (typically a layered rock salt structure belonging to a hexagonal system) capable of reversibly occluding and releasing lithium. Such a positive electrode active material has a half-value width of a diffraction peak obtained by a diffraction surface with a Miller index (003) of 0.06 to 0.1 deg. In a powder X-ray diffraction pattern using CuKα rays. (Preferably 0.07 to 0.09 deg.).

Here, powder X-ray diffraction (XRD) measurement using CuKα rays may be performed by making X-rays (CuKα rays) irradiated from an X-ray generation source incident on the sample surface of the sample. . The sample surface may be a surface made of a positive electrode active material (typically powder), and a surface on which the positive electrode is actually formed by binding the positive electrode active material with a binder (surface of the positive electrode active material layer) It may be. Then, the angle difference (diffraction angle 2θ) between the diffraction direction and the incident direction of the X-ray and the diffraction X-ray intensity are measured, and from the obtained diffraction pattern, the half width of the diffraction peak derived from the (003) plane. Can be calculated. Such X-ray diffraction measurement and calculation of the (003) plane half width can be performed using X-ray diffraction measurement devices commercially available from various measurement device manufacturers and attached analysis software. For example, an X-ray diffraction measuring device MultiFlex manufactured by Rigaku Corporation and the attached analysis software JADE can be used.

The lithium transition metal oxide is a compound containing at least one of nickel (Ni), cobalt (Co), and manganese (Mn) (for example, LiNiO ₂ , LiCoO ₂ , LiMnO ₂ , LiNi _1-x Co _x O ₂ (where 0 <x <1), LiNi _1-x Mn _x O ₂ (where 0 <x <1), LiNi _1-xy Co _x Mn _y O ₂ (where x> 0, y>) 0, x + y <1), etc.). The total content of these Ni, Co, and Mn is, for example, 0.85 or more (preferably 0.8 or more) when the total amount based on the atomic weight of all metal elements other than lithium contained in the positive electrode active material is 1. 95 or more). Among these, lithium transition metal oxides containing at least Ni as a constituent element are preferable.
As a preferred embodiment, a lithium transition metal oxide containing all of Ni, Co, and Mn as constituent elements (for example, LiNi _1-xy Co _x Mn _y O ₂ (where x> 0, y> 0, x + y <1 )). Of these transition metal elements, the main component is Ni, or a lithium transition metal oxide containing Ni, Co, and Mn at approximately the same ratio is particularly preferable. For example, when the total amount of these transition metal elements (Ni, Co, Mn) on an atomic weight basis is 1, the amounts of Ni, Co, and Mn all exceed 0.1 and are 0.6 or less (preferably 0 .3 and 0.5 or less) lithium transition metal oxide. Such a ternary lithium ion transition metal oxide is suitable for the practice of the present invention because it has excellent thermal stability and high energy density.

  In addition to these transition metal elements, the positive electrode active material in the technology disclosed herein further includes one or more other metal elements as additional constituent elements (additive elements). May be. Examples of such additional metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), chromium (Cr), Molybdenum (Mo), tungsten (W), iron (Fe), rhodium (Rh), palladium (Pb), platinum (Pt), copper (Cu), zinc (Zn), boron (B), aluminum (Al), Examples include gallium (Ga), indium (In), tin (Sn), lanthanum (La), and cerium (Ce). In particular, a positive electrode active material containing W as the additive element and having a content of 0.5% by mass to 1.0% by mass (for example, approximately 0.75% by mass) with respect to 100% by mass of the positive electrode active material is suitable. Can be used. The positive electrode active material containing W can easily control the (003) plane half-value width in the production process, and can easily set the (003) plane half-value width of the positive electrode active material within a preferable range.

  Note that the positive electrode active material layer may include components other than the active material, such as a conductive material and a binder. As the conductive material, carbon black such as acetylene black (AB) or other (such as graphite) carbon materials can be suitably used. PVDF or the like can be used as the binder.

  Such a positive electrode can be produced as follows, for example. First, a positive electrode active material and a material used as necessary are dispersed in a suitable solvent (for example, N-methyl-2-pyrrolidone) to prepare a paste-like (slurry) positive electrode active material forming composition, Next, it can be formed by applying an appropriate amount of the composition to the surface of the positive electrode current collector and then removing the solvent by drying. Moreover, the properties (for example, average thickness, active material density, porosity, etc.) of the positive electrode active material layer can be adjusted by performing an appropriate press treatment as necessary.

  In the negative electrode, a negative electrode active material layer containing a negative electrode active material is formed along the longitudinal direction on one side or both sides (here, both sides) of a long negative electrode current collector. As the negative electrode current collector, for example, a copper foil or the like can be used.

The negative electrode active material may be a layered carbon material capable of reversibly occluding and releasing lithium. Such a negative electrode active material has a BET specific surface area of 3.3 m ² / g or more (preferably 3.5 m ² / g or more, more preferably 3.8 m ² / g or more) using krypton (Kr) as an adsorption gas. .7m ² / g or less (preferably 4.5 m ² / g or less, more preferably 4.2 m ² / g or less) is characterized by satisfying the. The “KrBET specific surface area (m ² / g)” is a gas adsorption amount measured by a gas adsorption method (fixed capacity adsorption method) using Kr gas as an adsorption gas by a BET method (for example, a BET one-point method). It can be obtained by analysis.

Since the negative electrode active material having a KrBET specific surface area of 3.3 m ² / g or more has an area suitable as a physical lithium ion adsorption area, the negative electrode active material has a high load (for example, when charged with a large current). However, lithium ions can be occluded suitably, and lithium precipitation and accompanying reduction in battery capacity can be suppressed. Therefore, the non-aqueous electrolyte secondary battery (lithium ion secondary battery) provided with the negative electrode active material can exhibit excellent input characteristics. Furthermore, by setting the KrBET specific surface area to 4.7 m ² / g or less, the decomposition of the non-aqueous electrolyte can be suppressed, and the capacity reduction can be achieved by controlling the amount of lithium compound produced on the active material surface. Since it can suppress, high durability can be maintained. Such adjustment of the KrBET specific surface area can be performed by, for example, selecting a carbon material type constituting the negative electrode active material, or coating the surface of the carbon material with amorphous carbon. More specifically, for example, the KrBET specific surface area can be adjusted by changing the firing temperature when amorphous carbon is coated on the surface of the graphite particles. Or it can adjust also by performing a grinding | pulverization process and sieving suitably. Such adjustment methods may be performed alone or in appropriate combination.

Here, Kr used as the adsorbed gas has an adsorption cross-sectional area that is substantially the same as the effective cross-sectional area of lithium ions (the cross-sectional area of lithium ions in a solvated state), and therefore, the adsorption of solvated lithium ions. Suitable for evaluating the amount. Furthermore, since Kr has a lower saturated vapor pressure than nitrogen or argon used in general adsorption measurement, even when the adsorption amount is small (for example, when the Kr adsorption amount is 5 m ² / g or less). High-precision measurement is possible.

  As the carbon material constituting the negative electrode active material, for example, graphite, hard carbon, soft carbon and the like can be suitably used. Moreover, the carbon particle of the form by which the graphite particle as a core was coat | covered with the amorphous (amorphous) carbon raw material may be sufficient. A non-aqueous electrolyte secondary battery (lithium ion secondary battery) having such amorphous-coated graphite is suitable because irreversible capacity and resistance are suppressed and high durability can be exhibited.

  Note that the negative electrode active material layer can contain components other than the active material, such as a binder and a thickener. As the binder, styrene butadiene rubber (SBR) or the like can be used. As the thickener, for example, carbomethylcellulose (CMC) can be used.

  Such a negative electrode can be produced, for example, in the same manner as the above-described positive electrode. That is, a negative electrode active material and a material used as necessary are dispersed in a suitable solvent (for example, ion-exchanged water) to prepare a paste-like (slurry) negative electrode active material layer forming composition, It can be formed by applying an appropriate amount of the composition to the surface of the negative electrode current collector and then removing the solvent by drying. Moreover, the properties (for example, average thickness, active material density, porosity, etc.) of the negative electrode active material layer can be adjusted by performing an appropriate press treatment as necessary.

The positive electrode and the negative electrode disclosed herein are the ratio of the total weight W _P (mg) of the positive electrode active material contained in the positive electrode to the total weight W _N (mg) of the negative electrode active material contained in the negative electrode (W _P / W _N ). Is 1.2 or more and 1.6 or less. The weight ratio (W _P / W _N ) of the positive and negative electrode active materials is, for example, the mass (weight per unit area) of the active material layer (dried state) provided per unit area of the positive and negative electrode current collector or the positive and negative electrode active materials. It can adjust by adjusting the active material density | concentration etc. in the composition for layer formation suitably.

  The positive electrode and the negative electrode can typically face each other via a separator. Examples of the separator include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer).

As the nonaqueous electrolytic solution, typically, an organic solvent (nonaqueous solvent) containing a supporting salt can be used.
As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones and the like used in electrolytes of general lithium ion secondary batteries are used without particular limitation. Can do. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate.
As the supporting salt, for example, a lithium salt such as LiPF ₆ , LiBF ₄ , or LiClO ₄ can be suitably used. Particularly preferred support salt include LiPF _6. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less (for example, 1.1 mol / L).

  In addition, components other than the supporting salt and the non-aqueous solvent described above can be appropriately contained in the non-aqueous electrolyte. Such optional components include, for example, an increase in the amount of gas generated during overcharge, an improvement in battery output performance, an improvement in storage stability (such as suppression of capacity reduction during storage), an improvement in cycle characteristics, and an improvement in initial charge / discharge efficiency. It can be used for such purposes. Examples include gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB); film forming agents for lithium bisoxalate borate (LiBOB) and vinylene carbonate (VC); dispersants; thickeners; Is mentioned.

  The non-aqueous electrolyte secondary battery disclosed here can be used for various applications, but has both excellent input / output characteristics and high battery reliability (more specifically, the battery resistance is 6 mΩ or less). And the battery temperature during overcharge is 110 ° C. or lower). Therefore, taking advantage of this feature, for example, it can be suitably used as a driving power source mounted on a vehicle such as a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), or an electric vehicle (EV).

  Hereinafter, some examples relating to the present invention will be described. However, the present invention is not intended to be limited to the specific examples.

First, a (003) half-width positive electrode active material shown in FIGS. 3 and 4 (Tables 1 and 2) and a KrBET specific surface area negative electrode active material shown in FIGS. 3 and 4 (Tables 1 and 2) were prepared. A total of 36 types of nonaqueous electrolyte secondary batteries (lithium ion secondary batteries) were constructed using such positive and negative electrode active materials, and battery resistance and battery temperature during overcharge were measured. At this time, the ratio (W _P / W _N ) of the total weight W _P (mg) of the positive electrode active material contained in the positive electrode to the total weight W _N (mg) of the negative electrode active material contained in the negative electrode, that is, The weight ratio (W _P / W _N ) was set to 1.4.

Specifically, first, as the positive electrode active material, the (003) plane half-value width is a value indicated by “positive electrode active material (003) plane half-value width (deg.)” In FIGS. LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (LNCM) was prepared. This LNCM, AB as a conductive material, and PVDF as a binder are mixed with N-methylpyrrolidone (NMP) at a mass ratio of LNCM: AB: PVDF = 92: 5: 3 to form a positive electrode active material layer. A slurry was prepared. The slurry was applied to both sides of a long aluminum foil (positive electrode current collector) in a strip shape, dried, and pressed to prepare a positive electrode having a positive electrode active material layer on the positive electrode current collector.

Next, as the negative electrode active material, an amorphous coated graphite (C) whose KrBET specific surface area is the value shown in “Negative electrode active material KrBET (m ² / g)” in FIGS. Got ready. C, SBR as a binder, and CMC as a thickener are mixed with ion-exchanged water at a mass ratio of C: SBR: CMC = 98: 1: 1 to obtain a slurry for forming a negative electrode active material layer. Prepared. The slurry was applied in a strip shape on both sides of a long copper foil (negative electrode current collector), dried and pressed to prepare a negative electrode having a negative electrode active material layer on the negative electrode current collector.

  The positive electrode and the negative electrode produced by the above method were overlapped in the longitudinal direction via two separators having a three-layer structure in which a porous polypropylene layer was formed on both sides of the porous polyethylene layer, and wound in the longitudinal direction. Later, flattened wound electrode bodies were fabricated by crushing and ablating.

Next, the wound electrode body was accommodated in the battery case, and each battery was constructed by injecting a non-aqueous electrolyte from an opening (non-aqueous electrolyte injection port) of the battery case. Here, as the non-aqueous electrolyte, LiPF ₆ as a supporting salt was dissolved at a concentration of 1.1 mol / L in a mixed solvent containing EC, DMC, and EMC at a volume ratio of 3: 4: 3. A thing was used.

[Measurement of battery resistance]
About each battery produced as mentioned above, after adjusting to a 30% SOC charge condition at 1C under a temperature condition of -30 ° C, a constant current discharge was performed at 10C for 2 seconds, and the current (I) -voltage ( The battery resistance (IV resistance) (mΩ) was determined from the slope of the first-order approximation line of the plot value of V). The results are shown in FIG. 3 (Table 1).
Here, “1C” in this specification means a current value that can charge the battery capacity (Ah) predicted from the theoretical capacity in one hour. For example, when the battery capacity is 24 Ah, 1C = 24A. is there.

[Overcharge test]
First, after attaching a thermocouple to the outer surface of each battery produced as described above, the battery was adjusted to a SOC of 30% at 1 C and cooled until the battery temperature reached −10 ° C. Next, the battery was forcibly charged with a constant current of 10 C under a normal temperature (25 ° C.) temperature condition, and the charge was stopped immediately after the current was interrupted by the overcharge (separator shutdown). Thereafter, the battery temperature of each battery was measured over time, and the maximum temperature was recorded as the battery temperature (° C.) during overcharge. The results are shown in FIG. 4 (Table 2).

As shown in FIGS. 3 and 4 (Tables 1 and 2), the (003) plane half width of the positive electrode active material is 0.06 to 0.1 deg. In addition, by setting the KrBET specific surface area of the negative electrode active material to 3.3 m ² / g or more and 4.7 m ² / g or less, battery resistance tends to be reduced and increase in battery temperature during overcharge tends to be suppressed. I confirmed that there was. However, only by setting the above two parameters within the above range, there were batteries having a battery resistance higher than 6 mΩ and batteries having an overcharged battery temperature higher than 110 ° C.

Therefore, the weight ratio (W _P / W _N ) of the positive electrode active material and the negative electrode active material in the positive and negative electrodes, the (003) plane half-value width of the positive electrode active material, and the KrBET specific surface area of the negative electrode active material are shown in FIG. The non-aqueous-electrolyte secondary battery concerning Examples 1-20 set to the value shown to was produced. In addition, the battery concerning each example was produced with the material and process similar to the battery shown to the said FIGS. 3 and 4 (Table 1, 2) except the conditions mentioned above especially. And about each battery, the battery resistance and the battery temperature at the time of an overcharge were measured by the method similar to the battery shown to the said FIGS. The results are shown in FIG. 5 (Table 3).

As shown in FIG. 5 (Table 3), the (003) plane half-value width of the positive electrode active material is 0.06 to 0.1 deg. Examples 1 to Examples in which the negative electrode active material has a KrBET specific surface area of 3.3 m ² / g or more and 4.7 m ² / g or less, and the W _P / W _N is 1.2 or more and 1.6 or less. In any of the batteries according to No. 12, the battery temperature during overcharging was 110 ° C. or lower, and the battery resistance was 6 mΩ or lower. From the above, according to the technology disclosed herein, it was confirmed that a non-aqueous electrolyte secondary battery having both excellent input / output characteristics and high battery reliability can be provided.

Instead of adjusting the weight ratio (W _P / W _N ) of the positive and negative electrode active materials, 0.5% by mass or more and 1.0% by mass or less of tungsten may be included in the positive electrode active material. It was confirmed that a non-aqueous electrolyte secondary battery having a battery resistance of 6 mΩ or less and a battery temperature at overcharge of 110 ° C. or less can be provided (see FIG. 6 (Table 4)). Note that the “W concentration (mass%)” in FIG. 6 (Table 4) means the tungsten concentration in the positive electrode active material.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

<Other forms of the present invention>
By the way, from the viewpoint different from the above-described embodiment of the present invention, both excellent input / output characteristics and high reliability are achieved. More specifically, the battery resistance is reduced to 6 mΩ or less and the battery temperature during overcharge is set to 110. Since it has been confirmed that the temperature can be suppressed to below ℃, it is described below.

First, a (003) half-width positive electrode active material shown in FIGS. 7 and 8 (Tables 5 and 6) and lithium difluorophosphate (LiPO ₂ F ₂ ) having the concentrations shown in FIGS. 7 and 8 (Tables 5 and 6). A total of 30 non-aqueous electrolytes were prepared using non-aqueous electrolytes containing). Here, a negative electrode active material having a KrBET specific surface area of 5 m ² / g was used. Each non-aqueous electrolyte secondary battery was manufactured using the same materials and processes as the batteries shown in FIGS. 3 and 4 (Tables 1 and 2) except for the conditions described above. And about each battery, the battery resistance and the battery temperature at the time of an overcharge were measured by the method similar to the said Examples 1-20. The results are shown in FIGS. 7 and 8 (Tables 5 and 6).

As shown in FIGS. 7 and 8 (Tables 5 and 6), the (003) plane half width of the positive electrode active material is 0.06 to 0.1 deg. And by setting the LiPO ₂ F ₂ concentration in the non-aqueous electrolyte to 0.5 mass% or more and 1.5 mass% or less, the battery resistance is reduced and the battery temperature rise during overcharging is suppressed. It confirmed that there was a tendency. However, only by setting the above two parameters within the above range, there were batteries having a battery resistance higher than 6 mΩ and batteries having an overcharged battery temperature higher than 110 ° C.

Therefore, the ratio (W _L / W _P ) of the total weight W _P (mg) of the positive electrode active material contained in the positive electrode to the weight W _L (mg) of the non-aqueous electrolyte used for battery construction, 003) A total of 20 types of non-aqueous electrolyte secondary batteries (samples 100 to 119) in which the half-value width and the LiPO ₂ F ₂ content in the non-aqueous electrolyte were set to the values shown in FIG. 9 (Table 7). Created. In addition, each battery was produced with the material and process similar to the battery shown to the said FIG.7, 8 (Table 5, 6) except the conditions mentioned above especially. And about each battery, the battery resistance and the battery temperature at the time of an overcharge were measured by the method similar to the said Examples 1-20. The results are shown in FIG. 9 (Table 7).

As shown in FIG. 9 (Table 7), the (003) plane half width of the positive electrode active material is 0.06 to 0.1 deg. And then, the LiPO ₂ F ₂ concentration of the non-aqueous electrolytic solution was 1.5 wt% or less than 0.5 wt%, and by the _W L / _{W P} and 1.0 to 1.5, cell The resistance was reduced to 6 mΩ or less, and the battery temperature during overcharge could be suppressed to 110 ° C. or less.

Instead of adjusting the ratio of the non-aqueous electrolyte weight and the positive electrode active material weight (W _L / W _P ), 0.5% by mass or more and 1.0% by mass or less of tungsten is contained in the positive electrode active material. It was also confirmed that the non-aqueous electrolyte secondary battery having a battery resistance of 6 mΩ or less and a battery temperature of 110 ° C. or less during overcharge can be provided even when contained (see FIG. 10 (Table 8)). ). Note that “W concentration (mass%)” in FIG. 10 (Table 8) means the tungsten concentration in the positive electrode active material.

  As mentioned above, although the other form regarding this invention was demonstrated, these are only illustrations and are not intending limiting this invention and a claim to this other form.

Claims (1)

A non-aqueous electrolyte secondary battery comprising an electrode body having a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material, the following features:
The half-value width of the diffraction peak on the Miller index (003) plane obtained by subjecting the positive electrode active material to powder X-ray diffraction using CuKα rays is 0.06 to 0.1 deg. Be:
The negative electrode active material using krypton gas as an adsorption gas has a BET specific surface area of 3.3 m ² / g or more and 4.7 m ² / g or less; and the total weight W _{P of the} positive electrode active material contained in the positive electrode ( mg) and the total weight W _N (mg) of the negative electrode active material contained in the negative electrode (W _P / W _N ) is 1.2 or more and 1.6 or less;
A non-aqueous electrolyte secondary battery.

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