JP2023039363A - Positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a positive electrode for a nonaqueous electrolyte secondary battery, capable of suppressing heat generation in a case where a short circuit occurs.SOLUTION: A positive electrode mixture layer includes a first positive electrode active material, which is a layered compound represented by a general formula (1), a second positive electrode active material which is represented by a general formula (2) and in which a film of a carbon material is formed on a surface of a phosphoric acid compound that has an olivine structure, and a conductive material, and satisfies a following formula (3). (1) LiaNixCoyM11-x-yO2 (0<a≤1.2, 0<x≤0.9, 0<y≤0.5, 0<x+y<1) (2) LiMnzM2bFe1-z-bPO4 (0<z≤0.9, 0≤b≤0.1, 0<z+b<1) (3 ) 0.760≤(W1×R1+W2×R2)/D≤0.960 [W1 (W2): tap density of the first (second) positive electrode active material, R1 (R2): weight ratio of the first (second) positive electrode active material when the total weight of the two positive electrode active materials is 1, D: density of the positive electrode mixture layer calculated on the basis of, a thickness of a positive electrode when a charging rate of a secondary battery after initial activation treatment is 0%]SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to positive electrodes for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries.

In a non-aqueous electrolyte secondary battery, ions in the electrolyte are responsible for electrical conduction. Lithium secondary batteries, which are one type of non-aqueous electrolyte secondary batteries, are installed as power sources in small electronic devices such as digital cameras and laptop computers, and in vehicles. A lithium secondary battery is composed of a positive electrode, a negative electrode, and a separator. Among these, the positive electrode includes a positive electrode current collector and a positive electrode mixture layer coated on the surface of the positive electrode current collector and containing a positive electrode active material, a conductive material, and a binder.

Positive electrode active materials for non-aqueous electrolyte secondary batteries include LiFePO ₄ , olivine compounds partially substituted with Mn, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiCoNiO ₂ , LiCoMO ₂ , LiNiMO ₂ , and these positive electrode active materials. A ternary layered compound containing Co, Ni or Mn, or a layered compound containing Co, Ni or Mn is used. In particular, since layered compounds have high capacity and high voltage, they are suitable for applications where energy density is important. However, since layered compounds have poor thermal stability in a charged state, it is difficult to suppress heat generation when a short circuit occurs in a non-aqueous electrolyte secondary battery. Therefore, in order to ensure the safety of non-aqueous electrolyte secondary batteries, a technique has been developed in which a layered compound is mixed with LiFePO ₄ or an olivine compound partially substituted with Mn. Among them, olivine compounds in which a portion of _LiFePO4 is replaced with Mn have the same working potential as layered compounds, so it is known that safety can be easily ensured without significantly lowering the energy density when mixed. ing.

For example, in Patent Document 1, LiNi _5/10 Co _2/10 Mn _3/10 O ₂ and an olivine compound are used as positive electrode active materials, and the conditions for suppressing the rise in the surface temperature of the battery during short circuit are set to the tap density of the positive electrode active material. , the volume, the porosity of the positive electrode active material layer, and the positive electrode active material occupation ratio of the positive electrode active material layer calculated from these values. According to the content disclosed in Patent Document 1, the lower the positive electrode active material occupancy rate, that is, the higher the porosity of the positive electrode active material layer, the more the surface temperature rise of the battery is suppressed during a short circuit. is said to be easy.

Japanese Patent No. 6202191

However, in Patent Document 1, although LiNi _5/10 Co _2/10 Mn _3/10 O ₂ and LiFePO ₄ are used as positive electrode active materials, a layered compound and an olivine compound in which a part of LiFePO ₄ is replaced with Mn are used. was insufficient. The layered compound and the olivine compound in which a portion of LiFePO ₄ is replaced with Mn have reaction potentials close to each other, and the reactivity with the electrolytic solution is different from that in Patent Document 1. For this reason, the inventors of the present application conducted extensive studies, and found that the positive electrode active material occupation ratio specified in Patent Document 1 does not exhibit the effect of suppressing the temperature rise during a short circuit. In other words, simply using the technique disclosed in Patent Document 1 may not be able to suppress heat generation during a short circuit.

The present invention has been made in view of the above, and an object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery that suppress heat generation during a short circuit.

In the case of using a layered compound and an olivine compound in which a part of LiFePO ₄ is substituted with Mn as a positive electrode active material, the inventors of the present application have found that the substantial voids in the positive electrode mixture layer calculated from a predetermined relational expression It was found that heat generation during a short circuit can be suppressed if the degree is rather small.

In order to solve the above-described problems and achieve the object, a positive electrode for a non-aqueous electrolyte secondary battery according to the present invention comprises a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector. wherein the positive electrode mixture layer comprises a first positive electrode active material, which is a layered compound represented by the general formula shown in the following formula (1), and the following formula (2 ) and includes a second positive electrode active material in which a film made of a carbon material is formed on the surface of a phosphoric acid compound having an olivine structure, and a conductive material, and the first positive electrode active material W1 is the tap density (g/cc) of the substance, W2 is the tap density (g/cc) of the second positive electrode active material, and 1 is the total weight of the first and second positive electrode active materials. R1 is the weight ratio of the first positive electrode active material; R2 is the weight ratio of the second positive electrode active material when the total weight of the first and second positive electrode active materials is 1; Let D be the density (g/cc) of the positive electrode mixture layer calculated based on the thickness of the positive electrode for the nonaqueous electrolyte secondary battery when the charge rate of the subsequent nonaqueous electrolyte secondary battery is 0%. Then, the following formula (3) is satisfied.
Li _a Ni _x Co _y M1 _1-xy O ₂ (1)
_{LiMnzM2bFe1 - z- bPO4} (2)
0.760≦(W1×R1+W2×R2)/D≦0.960 (3)
However, in the above formula (1), M1 is Ti, Zr, Nb, W, P, Al, Mg, V, Mn, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, at least one selected from Sn, Cu, Ag, Ce, Pr, Ge, Bi, Ba, Er, La, Sm, Yb, Sb, Bi, S and Zn, 0<a≤1.2, 0< satisfying x ≤ 0.9, 0 < y ≤ 0.5, 0 < x + y < 1,
In the above formula (2), M2 is from Ni, Co, Ti, Cu, Zn, Mg, Zr, Ca, Y, Mo, Ba, Pb, Bi, La, Ce, Nd, Gd, Al, Ga and Sr It is at least one selected and satisfies 0<z≦0.9, 0≦b≦0.1, and 0<z+b<1.

In the positive electrode for a nonaqueous electrolyte secondary battery according to the present invention, in the above invention, the median diameter of the first positive electrode active material is preferably larger than D90 of the second positive electrode active material.

In the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention, in the above invention, the second positive electrode active material has a tap density W2 of 0.7 g/cc or more and 1.00 g/cc or less. good.

In the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention, the weight ratio R2 of the second positive electrode active material is preferably 0.1 or more and 0.3 or less.

A non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode for a non-aqueous electrolyte secondary battery according to the above-described invention, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt and a non-aqueous solvent. Prepare.

ADVANTAGE OF THE INVENTION According to this invention, the positive electrode for nonaqueous electrolyte secondary batteries and nonaqueous electrolyte secondary battery which suppress heat_generation|fever at the time of a short circuit can be obtained.

FIG. 1 is a cross-sectional view for explaining the configuration of a non-aqueous electrolyte secondary battery including a positive electrode for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention. FIG. 2 is an exploded perspective view for explaining the configuration of a non-aqueous electrolyte secondary battery having a positive electrode for a non-aqueous electrolyte secondary battery according to Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, but the present invention is not limited to the following description. In addition, various modifications or improvements can be added to the present embodiment, and forms to which such modifications or improvements are added can also be included in the present invention.

Although details will be described later, FIG. 1 is a cross-sectional view of a laminate type non-aqueous electrolyte secondary battery, and FIG. 2 is an exploded perspective view for explaining the configuration of a coin-type non-aqueous electrolyte secondary battery.
1 and 2 show configuration examples in the case of a laminate type non-aqueous electrolyte secondary battery and a coin type non-aqueous electrolyte secondary battery as examples of embodiments, but the non-aqueous electrolyte secondary in the present invention The shape of the battery is not particularly limited, and may be flat, cylindrical, rectangular, coin-shaped, or the like. Also, the exterior body of the non-aqueous electrolyte secondary battery is not particularly limited, and known materials such as laminate film, aluminum, aluminum alloy, and stainless steel can be used.

(Embodiment 1)
FIG. 1 is a cross-sectional view for explaining the configuration of a non-aqueous electrolyte secondary battery including a positive electrode for a non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention. The non-aqueous electrolyte secondary battery 1 shown in FIG. 1 is a laminated non-aqueous electrolyte secondary battery formed by laminating a plurality of sets each including a positive electrode, a negative electrode, and a separator.

A non-aqueous electrolyte secondary battery 1 includes a bag-shaped exterior body 2 made of a laminate film. An electrode group 3 having a laminated structure is accommodated in the exterior body 2 . A laminate film has a structure in which, for example, a plurality of (for example, two) plastic films are laminated and a metal foil such as an aluminum foil is sandwiched between the adjacent plastic films. A heat-sealable resin film is used for one of the two plastic films. The exterior body 2 includes two laminate films stacked so that the heat-sealable resin films face each other, and the electrode group 3 and the non-aqueous electrolyte are accommodated between the laminate films. The electrode group 3 and the non-aqueous electrolytic solution are airtightly accommodated by heat-sealing the two laminate film portions to each other.

The electrode group 3 has a positive electrode 4 , a negative electrode 5 , a separator 6 , a positive electrode lead 7 , a positive electrode tab 8 , a negative electrode lead 9 and a negative electrode tab 10 . A separator 6 is interposed between the positive electrode 4 and the negative electrode 5 . The electrode group 3 has a structure in which a plurality of electrodes are laminated such that the negative electrode 5 is positioned as the outermost layer and the separator 6 is positioned between the negative electrode 5 and the inner surface of the outer package 2 .

The positive electrode 4 is composed of a positive electrode current collector 41 and a positive electrode mixture layer 42 formed on one or both surfaces of the positive electrode current collector 41 .

The positive electrode current collector 41 is made of aluminum, nickel, stainless steel, titanium, other alloys, or the like. Among them, it is preferable to use aluminum from the viewpoint of electronic conductivity and battery operating potential.

The positive electrode mixture layer 42 includes a first positive electrode active material, a second positive electrode active material, a conductive material, and a binder. The density of the positive electrode mixture layer 42 is adjusted, for example, by pressing.
The first and second positive electrode active materials are capable of intercalating and deintercalating lithium, respectively.

The first positive electrode active material is a layered compound represented by the general formula shown in formula (1) below. The layered compound is a lithium (Li)-nickel (Ni)-cobalt (Co)-containing composite metal oxide composed of layers of sheet-like particles.
Li _a Ni _x Co _y M1 _1-xy O ₂ (1)
However, in general formula (1), M1 is titanium (Ti), zirconium (Zr), niobium (Nb), tungsten (W), phosphorus (P), aluminum (Al), magnesium (Mg), vanadium (V ), manganese (Mn), calcium (Ca), strontium (Sr), chromium (Cr), iron (Fe), boron (B), gallium (Ga), indium (In), silicon (Si), molybdenum (Mo ), yttrium (Y), tin (Sn), copper (Cu), silver (Ag), cerium (Ce), praseodymium (Pr), germanium (Ge), bismuth (Bi), barium (Ba), erbium (Er ), lanthanum (La), samanium (Sm), ytterbium (Yb), antimony (Sb), bismuth (Bi), sulfur (S) and zinc (Zn), and 0 < a ≤ 1 .2, 0<x≦0.9, 0<y≦0.5, 0<x+y<1.

The second positive electrode active material is represented by the general formula shown in the following formula (2), and is a compound in which a film made of a carbon material is formed on the surface of a phosphoric acid compound (olivine-based compound) having an olivine structure.
LiMn _z M2 _b Fe _1-zb PO ₄ (2)
However, in general formula (2), M2 is nickel (Ni), cobalt (Co), titanium (Ti), copper (Cu), zinc (Zn), magnesium (Mg), zirconium (Zr), calcium (Ca) , yttrium (Y), molybdenum (Mo), barium (Ba), lead (Pb), bismuth (Bi), lanthanum (La), cerium (Ce), neodymium (Nd), gadolinium (Gd), aluminum (Al) , gallium (Ga) and strontium (Sr), and satisfies 0<z≦0.9, 0≦b≦0.1, and 0<z+b<1. By including the second positive electrode active material in the positive electrode mixture layer 42, the structure is such that the first positive electrode active material with low thermal stability is covered with the second positive electrode active material with high thermal stability. Therefore, it is possible to reduce an exothermic reaction due to direct contact between the first positive electrode active material and the non-aqueous electrolyte when a short circuit occurs.

The carbon material is a conductive carbon material. In the second positive electrode active material, at least a part of the surfaces of at least some of the primary particles is coated with a carbon material by a coating of the carbon material present on the surface of the second positive electrode active material. The purity of carbon and the thickness of the carbon film can be selected arbitrarily, but the ratio of the weight of the carbon material to the weight of the entire second positive electrode active material is controlled to be 0.1% or more and 5% or less. is preferred.

Further, the tap density (g/cc) of the first positive electrode active material is W1, the tap density (g/cc) of the second positive electrode active material is W2, and the total weight of the first and second positive electrode active materials is 1 R1 is the weight ratio of the first positive electrode active material when , R2 is the weight ratio of the second positive electrode active material when the total weight of the first and second positive electrode active materials is 1, and R2 is the weight ratio of the positive electrode active material When the density (g/cc) of the agent layer 42 is D, the following formula (3) is satisfied.
0.760≦(W1×R1+W2×R2)/D≦0.960 (3)
Note that the density D of the positive electrode mixture layer 42 referred to here means that the state of charge (SOC) of the non-aqueous electrolyte secondary battery after the initial activation treatment by at least one cycle of charging and discharging is 0%. It refers to a value calculated based on the thickness of the positive electrode at the time of .

In the above formula (3), the value of (W1 × R1 + W2 × R2) / D is the ratio of the density of the positive electrode mixture layer to the weight average of the tap density of the positive electrode active material, and the substantial voids in the positive electrode mixture layer. represents the degree of If the value of the above formula is less than 0.760, the inside of the positive electrode mixture layer becomes too dense, so that the electrode may be distorted in the pressing process during electrode production, resulting in a decrease in production efficiency during battery production. . If the value of the above formula is greater than 0.960, the substantial degree of voids in the positive electrode mixture layer is large. and the non-aqueous electrolyte are in direct contact with each other. Therefore, when the non-aqueous electrolyte secondary battery is short-circuited, the first positive electrode active material with low thermal stability and the non-aqueous electrolyte are likely to cause an exothermic reaction, so heat generation of the non-aqueous electrolyte secondary battery should be suppressed. can't That is, by setting the value of the above formula to 0.760 or more and 0.960 or less, it is possible to substantially reduce the degree of voids in the positive electrode mixture layer while maintaining the production efficiency in the pressing process for electrode production. , the exothermic reaction between the first positive electrode active material and the non-aqueous electrolyte at the time of short circuit can be reduced as much as possible, and the heat generation of the non-aqueous electrolyte secondary battery can be suppressed.

Further, the weight ratio R2 of the second positive electrode active material is preferably 0.1 or more and 0.3 or less. When the weight ratio of the second positive electrode active material exceeds 0.3 (30%), the charge/discharge curve of the non-aqueous electrolyte secondary battery 1 tends to have multiple stages (the inflection point increases). It becomes difficult to estimate the depth of charge and the state of deterioration from the voltage value and the current value at the time of discharge, and the practicality decreases. If the weight ratio of the second positive electrode active material is less than 0.1 (10%), the coating of the first positive electrode active material with the second positive electrode active material may be insufficient. If the coating of the first positive electrode active material with the second positive electrode active material is insufficient, decomposition of the electrolyte occurs on the surface of the first positive electrode active material, and thermal runaway is likely to occur during a short circuit.

Further, the tap density of the second positive electrode active material is preferably 0.7 g/cc or more and 1.00 g/cc or less, more preferably 0.8 g/cc or more. When the tap density is 1.00 g / cc or less, the primary particles of the second positive electrode active material do not form high-density granules or secondary particles and have a bulky shape. The positive electrode active material can be surrounded more closely, and heat generation due to thermal runaway at the time of short circuit can be suppressed. Therefore, not only is the temperature of the non-aqueous electrolyte secondary battery less likely to rise during a short circuit, but swelling, cracking, and rupture due to decomposition of the electrolyte on the surface of the first positive electrode active material due to a temperature increase are also less likely to occur. On the other hand, when the tap density is more than 1.00 g/cc, the second positive electrode active material is in a state of being granulated at high density, so that it becomes difficult to surround the first positive electrode active material without gaps, resulting in a short circuit. It is not possible to prevent the temperature rise of the non-aqueous electrolyte secondary battery, and swelling, cracking and bursting are likely to occur. Further, when the tap density is less than 0.70 g/cc, the dispersibility of the second positive electrode active material is lowered when preparing the slurry of the positive electrode mixture layer 42, and the second positive electrode active material tends to be aggregated, causing streaks when preparing the positive electrode. , making it difficult to produce a positive electrode of uniform quality. Moreover, when the tap density is 0.80 g/cc or more, the dispersibility of the second positive electrode active material during preparation of the slurry becomes better.

In the positive electrode mixture layer 42, the median diameter of the first positive electrode active material is larger than D90 of the second positive electrode active material. When the median diameter of the first positive electrode active material measured by a laser diffraction/scattering method or the like is smaller than D90 of the second positive electrode active material, the second positive electrode having a particle diameter larger than that of the first positive electrode active material The ratio of the active material is increased, and the second positive electrode active material cannot surround the first positive electrode active material without gaps. As a result, the contact area between the first positive electrode active material and the electrolytic solution is increased, so thermal runaway is likely to occur at the time of a short circuit, increasing the amount of heat generated in the cell. In addition, in this specification, the median diameter may be described as D50.

The above-described median diameter, D90, and tap density refer to the values in the positive electrode mixture layer 42 after manufacturing the non-aqueous electrolyte secondary battery. Since the values are approximately the same as the median diameter, D90, and tap density of the second positive electrode active material, the values of the median diameter, D90, and tap density of the first positive electrode active material and the second positive electrode active material before production are If the requirements of the present invention are satisfied, the manufactured positive electrode can also be considered to satisfy the requirements of the present invention.

Further, whether or not the median diameter, D90, and tap density values of the first positive electrode active material and the second positive electrode active material in the positive electrode mixture layer after fabrication satisfy the requirements of the present invention can be determined, for example, by the following method. can be verified by The non-aqueous electrolyte secondary battery is disassembled in a glove box filled with argon, and the positive electrode 4 is taken out. After washing the positive electrode 4 with an appropriate solvent (for example, dimethyl carbonate), vacuum drying is performed to remove the solvent. Next, by immersing the positive electrode in a solvent such as N-methyl-2-pyrrolidone and applying ultrasonic waves, the positive electrode mixture layer 42 can be separated from the positive electrode current collector 41 . By centrifuging the solvent in which the separated positive electrode mixture layer 42 is dispersed, each substance in the positive electrode mixture layer 42 can be separated. For the separated first positive electrode active material and second positive electrode active material, the median diameter and D90 can be measured, for example, by a laser diffraction/scattering method. The tapped density can be measured by measuring the weight divided by the packed volume. Note that the non-aqueous electrolyte secondary battery used above may be subjected to initial activation and charge/discharge cycles in any process, and when the positive electrode 4 is taken out, the charging rate of the non-aqueous electrolyte secondary battery is adjusted in advance. A state of 0% is preferred.

The conductive material assists electron conduction in the positive electrode. The conductive material is not particularly limited, and known materials can be used. Examples of the conductive material include conductive carbon powder such as carbon black carbon black such as acetylene black and ketjen black, carbon nanotube, carbon nanofiber, graphene, activated carbon, and graphite. The conductive material may consist of one type of material, or may consist of multiple types of materials (for example, a first conductive material and a second conductive material).

The binding material binds the positive electrode current collector, positive electrode active material, and conductive material. The binder is not particularly limited, and any known or commercially available binder can be used. Examples of binding agents include polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyethylene (PolyEthylene: PE), Polypropylene (PP), ethylene-propylene copolymer, styrene-butadiene rubber (SBR), butadiene rubber, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), butyl rubber, poly (meth ) Acrylate (PolyMethylMethAcrylate: PMMA), polyethylene oxide (PEO), polypropylene oxide (PolypropyleneOxide: PO), polyepichlorohydrin, polyphosphazene, polyacrylonitrile, hexafluoropropylene ( hexanuopropylene:HFP) and copolymers thereof, or a mixture of two or more thereof.

The negative electrode 5 includes a negative electrode current collector 51 and a negative electrode mixture layer 52 containing a negative electrode active material or metallic lithium (not shown) formed on one or both surfaces of the negative electrode current collector 51 .

Although the negative electrode current collector 51 is not particularly limited, it is preferable to use a metal. Suitable such metals are, for example, aluminum foil and copper, and depending on the application, porous aluminum current collectors and the like are also used. Among them, copper is preferable from the viewpoint of electronic conductivity and battery operating potential.

The negative electrode mixture layer 52 is made of, for example, lithium, a lithium alloy, a titanium-niobium alloy, graphite, amorphous carbon, a transition metal composite oxide (for example, Li ₄ Ti ₅ O ₁₂ , or TiNb ₂ O ₇ ), or absorbs and absorbs lithium. At least one selected from a releasable alloy or silicon is included as an active material. Among these, graphite is preferable because it has an operating potential very close to that of metallic lithium, can be charged and discharged at a high operating voltage, and has excellent cycle characteristics. Alternatively, graphite may be used in combination with another negative electrode active material. Further, the negative electrode mixture layer 52 contains a conductive material and a binder. Materials equivalent to those used in the positive electrode 4 can be used for the conductive material and the binder.

The separator 6 is provided between the positive electrode and the negative electrode, and has porosity through which components of the non-aqueous electrolyte can pass. The separator 6 is configured using, for example, a porous sheet separator made of polymer or fiber, a non-woven fabric separator, or the like. The separator 6 may be made of a material such as polyethylene, polypropylene, aramid, polyimide, etc., and may have a plurality of layers of different materials including these, from the viewpoint of providing a shutdown function during heat generation. It preferably has a layer containing polyethylene. The separator 6 preferably has a pore diameter of 0.01 to 10 μm and a thickness of 5 to 30 μm. Moreover, the separator 6 may be one in which a ceramic layer as a heat-resistant insulating layer is laminated on a porous substrate. If a solid electrolyte is used as the non-aqueous electrolyte, separator 6 may not be present.

The positive electrode leads 7 extend to the lower side of the positive electrode mixture layer 42 in FIG. 1, for example. Each positive electrode lead 7 is, for example, a portion of the positive electrode current collector 41 to which the positive electrode mixture layer 42 is not applied. Each positive electrode lead 7 is bundled at the end portion on the side opposite to the positive electrode mixture layer 42 side in the exterior body 2 and joined to each other.

One end of the positive electrode tab 8 is joined to the positive electrode lead 7 , and the other end extends outside through the sealing portion of the outer package 2 .

The negative electrode leads 9 extend to the upper side of the negative electrode mixture layer 52 in FIG. 1, for example. It may extend in the same direction as the positive electrode lead 7 as long as it does not contact the positive electrode lead 7 . Each negative electrode lead 9 is, for example, a portion of the negative electrode current collector 51 to which the negative electrode mixture layer 52 is not applied. Each negative electrode lead 9 is bundled at the end portion on the side opposite to the negative electrode mixture layer 52 side in the exterior body 2 and joined to each other.

One end of the negative electrode tab 10 is joined to the negative electrode lead 9 , and the other end extends outside through the sealing portion of the outer package 2 .

A non-aqueous electrolyte or a solid electrolyte can be used as the non-aqueous electrolyte. In particular, the non-aqueous electrolyte will be described. A non-aqueous electrolyte is enclosed in the exterior body 2 . The non-aqueous electrolyte injection site of the outer package 2 is sealed after the non-aqueous electrolyte is injected. A non-aqueous electrolyte contains an electrolyte and a non-aqueous solvent.

The electrolyte is not particularly limited, and lithium salts commonly used in non-aqueous electrolyte secondary batteries can be used. For example, _LiPF6 , _LiAsF6 , _LiBF4 , LiCF3SO3, LiN( _{CmF2m + 1SO2} ) ( _{CnF2n + 1SO2 )} (m and n are integers of 1 or more) _, LiC( _{CpF2p +1} SO ₂ ) (C _q F _2q+1 SO ₂ ) (C _r F _2r+1 SO ₂ ) (p, q, r are integers of 1 or more), lithium difluoro(oxalato)borate, lithium bisoxalate borate, etc. can be done. These electrolytes may be used singly or in combination of two or more. In addition, the concentration of the electrolyte is 0.1 to 3 mol/L, preferably 0.5 to 1.5 mol/L, from the viewpoint of lithium ion conductivity, electrolyte viscosity, and temperature characteristics of conductivity. It is desirable to

The non-aqueous solvent contains cyclic carbonate and/or chain carbonate as a main component. The cyclic carbonate is preferably at least one selected from ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The chain carbonate is preferably at least one selected from DiMethylCarbonate (DMC), DiEthylCarbonate (DEC), EthylMethylCarbonate (EMC), and the like. The cyclic carbonate is related to the degree of dissociation of the electrolyte components, and the chain carbonate is related to the viscosity of the electrolyte solution.

Moreover, additives other than the lithium salt may be included for the purpose of forming a good film on the surface of the negative electrode active material by reductive decomposition during charging and discharging. Although the additive is not particularly limited, for example, vinylene carbonate, fluoroethylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide (MMDS), 1,5,2,4-dioxadithiane 2,2,4,4 -tetroxide, tris(trimethylsilyl)phosphite, 1-propene 1,3-sultone, Li ₂ PO ₂ F ₂ , and the like. These additives may be used alone or in combination of two or more. Moreover, you may mix and use with additives other than this. Furthermore, additives other than these may be used alone.

In Embodiment 1, in the positive electrode 4 of the non-aqueous electrolyte secondary battery 1, the positive electrode mixture layer 42 has the tap density W1 of the first positive electrode active material, the tap density W2 of the second positive electrode active material, and the tap density W2 of the second positive electrode active material. and the ratio R1 of the weight of the first positive electrode active material when the total weight of the second positive electrode active material is 1, and the second positive electrode when the total weight of the first and second positive electrode active materials is 1 When the weight ratio of the active material is R2 and the density of the positive electrode mixture layer 42 is D, (W1×R1+W2×R2)/D is set to satisfy 0.760 or more and 0.960 or less. Here, as described above, when LiNi _5/10 Co _2/10 Mn _3/10 O ₂ and LiMn _0.7 Fe _0.3 PO ₄ having reaction potentials close to each other are mixed, the reaction area is reduced to reduce the electrolysis. Reactivity with liquid can be increased. Therefore, in Embodiment 1, the density of the electrode 4 is increased with respect to the density of the entire active material obtained from the weight average of the tap densities of the active materials. In other words, by reducing the substantial voids in the electrode 4, the contact area with the electrolytic solution is reduced, and rapid heat generation due to thermal decomposition of the positive electrode 4 is suppressed. According to Embodiment 1, it is possible to obtain positive electrode 4 and non-aqueous electrolyte secondary battery 1 that suppress heat generation during a short circuit.

(Embodiment 2)
FIG. 2 is an exploded perspective view for explaining the configuration of a non-aqueous electrolyte secondary battery having a positive electrode for a non-aqueous electrolyte secondary battery according to Embodiment 2 of the present invention. Nonaqueous electrolyte secondary battery 1A includes case 110, leaf spring 111, positive electrode current collector 112, positive electrode mixture layer 113, separator 114, negative electrode 115, gasket 116, and cap 117. A positive electrode 118 is composed of the positive electrode current collector 112 and the positive electrode mixture layer 113 .

In the non-aqueous electrolyte secondary battery 1A, the case 110 and the cap 117 are fixed by caulking or the like, and the interior is filled with a non-aqueous electrolyte. In non-aqueous electrolyte secondary battery 1A, case 110, gasket 116 and cap 117 are liquid-tightly sealed. Also, the positive electrode current collector 112 , the positive electrode mixture layer 113 , the separator 114 and the negative electrode 115 are biased toward the cap 117 by the plate spring 111 . As a result, the members are kept in close contact with each other.

The positive electrode current collector 112 is configured using the same material as the positive electrode current collector 41 .
The positive electrode mixture layer 113 has the same configuration as the positive electrode mixture layer 42 .

The separator 114 is provided between the positive electrode and the negative electrode 115 and has a porous disk shape. Separator 114 has the same configuration as separator 6 .

The non-aqueous electrolyte of Embodiment 1 can be used as the non-aqueous electrolyte.

A negative electrode 115 has a structure similar to that of the negative electrode 5 .

In Embodiment 2, in the positive electrode 118 of the non-aqueous electrolyte secondary battery 1A, the positive electrode mixture layer 113 has the first positive electrode active material tap density W1, the second positive electrode active material tap density W2, and the first positive electrode active material tap density W2. and the ratio R1 of the weight of the first positive electrode active material when the total weight of the second positive electrode active material is 1, and the second positive electrode when the total weight of the first and second positive electrode active materials is 1 When the weight ratio of the active material is R2 and the density of the positive electrode mixture layer 42 is D, (W1×R1+W2×R2)/D is set to satisfy 0.760 or more and 0.960 or less. According to Embodiment 2, it is possible to obtain positive electrode 118 and non-aqueous electrolyte secondary battery 1A that suppress heat generation during a short circuit.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the following examples.

<Method for producing positive electrode>
75.2% by weight of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM) as the first positive electrode active material, and LiMn _0.7 Fe _0.3 PO ₄ (LMFP) as the second positive electrode active material. ) of 18.8% by weight, 2% by weight of graphite as a first conductive material, 3% by weight of acetylene black as a second conductive material, 1% by weight of polyvinylidene fluoride (PVDF) as a binder, and viscosity An appropriate amount of N-methyl-2-pyrrolidone (NMP) was mixed as an adjustment solvent to prepare a positive electrode active material slurry.

The obtained positive electrode active material slurry was applied to both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector and dried to form a positive electrode mixture layer. At this time, the coating amount per one side of the positive electrode mixture layer was 99 g/m ² . Subsequently, the positive electrode was press-worked. After that, it was cut so that the non-coated portion protruded in a rectangular shape as a positive electrode lead from one side of the rectangle where the positive electrode mixture layer was coated. The projecting portion functions as a positive electrode lead without forming a positive electrode material mixture layer.

<Method for preparing negative electrode>
96.7% by weight of graphite as a negative electrode active material, 0.3% by weight of acetylene black as a conductive material, 1.5% by weight of styrene-butadiene rubber as a binder, and 1.5% by weight of carboxymethyl cellulose as a thickener. , and an appropriate amount of ion-exchanged water as a viscosity adjusting solvent were mixed to prepare a negative electrode active material slurry.

The prepared negative electrode active material slurry was applied to both sides of a copper foil having a thickness of 10 μm, which was a negative electrode current collector, and dried to form a negative electrode mixture layer, thereby producing a negative electrode. At this time, the coating amount per side of the negative electrode mixture layer was 58 g/m ² . Subsequently, the negative electrode was press-worked to set the density of the negative electrode mixture layer to 1.2 g/cm ³ . After that, it was cut so that the uncoated portion protruded in a rectangular shape from one side of the rectangle where the negative electrode mixture layer was formed. The protruding portion does not form the negative electrode mixture layer and functions as a negative electrode lead.

<Preparation of non-aqueous electrolyte>
1.3 mol/L of LiPF ₆ as a lithium salt and 3% by weight of vinylene carbonate as an additive were added to a mixed solvent in which ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate were mixed in a volume ratio of 2:5:3. The dissolved material was used as a non-aqueous electrolyte.

<Production of electrode element>
Next, an electrode element was produced by alternately laminating a positive electrode having a positive electrode current collecting lead and a negative electrode having a negative electrode current collecting lead on a separator connected in a zigzag pattern. A separator (PE/PP/PE) in which surface layers made of polypropylene are arranged on both sides of a base layer made of polyethylene was used. The thickness of the separator is 20 μm. Subsequently, the positive electrode lead and the negative electrode lead were respectively bundled, the positive electrode terminal was connected to the bundled positive electrode lead by ultrasonic welding, and the negative electrode terminal was connected to the bundled negative electrode lead by ultrasonic welding. The produced electrode element had a thickness of 3.0 mm and a rated capacity of 4.8 Ah. In addition, the "rated capacity" referred to here is a constant current-constant voltage charge (cutoff current: 0.05C) with an upper limit voltage of 4.2V and a current value of 0.5C. It refers to the discharge capacity when constant current discharge is performed at 0.2C.

<Production of non-aqueous electrolyte secondary battery>
Two laminate films having a structure in which a heat-sealable resin layer made of polyolefin, a metal layer made of aluminum foil, and a protective layer made of nylon resin and polyester resin were laminated in this order were prepared as an outer package. The heat-sealable resin layers of the two laminate films were arranged to face each other, and the adhesive surfaces of the laminate films were overlapped so that the electrode group was housed in the two housing recesses. The electrode group was arranged such that the portion of each terminal where the heat-sealable resin portion was formed passed between the peripheral edges of the two laminate films, and a part of each terminal was exposed to the outside. In this state, the heat-sealing resin layers of the peripheral edges of the laminate films were heat-sealed on three sides including the two sides from which the respective tabs of the laminate films extended. Subsequently, the electrolytic solution prepared above was injected from one side of the exterior body that was not heat-sealed. Next, the remaining one side of the exterior body was heat-sealed under a reduced pressure environment to fabricate a non-aqueous electrolyte secondary battery (cell).

<Tap density>
As described in JIS Z2504:2020, powdered NCM and LMFP were each placed in a container. After that, each container was tapped 100 times, and the value obtained by dividing the weight by the volume in which the gaps between the particles were filled was measured, and this was used as the tap density of each. A shaking specific gravity meter was used for the measurement.

<Measurement of particle size>
As the median diameter of NCM, the value of the particle diameter (D50) at which the relative particle amount is 50% measured by the laser diffraction/scattering method described in JIS Z8825:2013 was used. Similarly, as the D90 of LMFP, the value of the particle diameter (D90) showing a relative particle amount of 90% was used. For the measurement, a laser diffraction particle size distribution analyzer SALD-2300 (manufactured by Shimadzu Corporation) was used.

<Initial activation of the battery>
The fabricated cell was transferred to a constant temperature bath set at 25° C., and 5 cycles of initial activation steps were performed. The charging and discharging in the first cycle is constant current and constant voltage charging with a current of 0.1 C, an upper limit voltage of 4.2 V and a cutoff current of 0.05 C, and a constant current discharge with a current of 0.5 C and a lower limit voltage of 2.7 V. and In the charging and discharging of the 2nd to 5th cycles, the charging current is 0.2C, the voltage is 4.2V, and the cutoff current is 0.05C. A constant current discharge was used. A rest time of 15 minutes was set after charging and after discharging. After the 5th cycle, the battery was charged at 0.2C for 1 hour to adjust the SOC to 20%.

<Measurement of density after initial activation>
Separately from the cell used for the nail penetration test, which will be described later, a cell was prepared up to the initial activation under exactly the same conditions as above. After the cell was adjusted to have an SOC of 0% by constant current discharge at a current of 0.5 C and a lower limit voltage of 2.7 V, the cell was disassembled in a glove box filled with argon, and the positive electrode was taken out. The density D after the initial activation was calculated from the thickness of this positive electrode.

<Nail penetration test>
The prepared non-aqueous electrolyte secondary battery (cell) was previously subjected to constant current-constant voltage charging (cutoff current: 0.05 C) with an upper limit voltage of 4.2 V and a current value of 0.5 C. A nail (made of stainless steel, 3 mm in diameter) was inserted into the center of the cell at a nail penetration speed of 0.1 mm/sec and a nail penetration depth of 3.0 mm to just before penetration, and the surface of the cell after nail penetration. The maximum value of temperature (hereinafter referred to as "surface temperature") was measured. In addition, the appearance of the cell was checked 1 hour after the nail penetration, and the presence or absence of cleavage other than the nail penetration part was confirmed. While referring to the international standard IEC TR 62660-4, this test was conducted by increasing the penetration depth of the nail to make it easier to generate heat than in the international standard IEC TR 62660-4 so that more positive and negative electrodes are short-circuited at the same time. The conditions are set, and the test assumes a very severe short circuit condition.

(Example 1)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. The value of (W1*R1+W2*R2)/D was 0.900. The density of the positive electrode mixture layer immediately after pressing was 2.70 g/cm ³ . After the nail penetration test, the cell was not cleaved and the surface temperature was 78°C.

(Example 2)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W2 is 0.800 g/cc and the D90 of the LMFP is 12.4 μm. The value of (W1*R1+W2*R2)/D was 0.887. After the nail penetration test, the cell was cleaved and the surface temperature was 122°C.

(Example 3)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W2 is 1.05 g/cc and the D90 of the LMFP is 9.50 μm. The value of (W1*R1+W2*R2)/D was 0.907. After the nail penetration test, the cell was cleaved and the surface temperature was 136°C.

(Example 4)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W2 is 0.790 g/cc and the D90 of the LMFP is 9.70 μm. The value of (W1*R1+W2*R2)/D was 0.886. After the nail penetration test, the cell was not cleaved and the surface temperature was 94°C.

(Example 5)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W1 is 2.80 g/cc, the density D is 2.55 g/cc, and the NCM D50 is 14.0. The value of (W1*R1+W2*R2)/D was 0.954. After the nail penetration test, the cell was not cleaved and the surface temperature was 98°C.

(Example 6)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the density of the positive electrode mixture layer immediately after pressing is 2.60 g/cc and the density D after initial activation is 2.48 g/cc. The value of (W1*R1+W2*R2)/D was 0.932. After the nail penetration test, the cell was not cleaved and the surface temperature was 104°C.

(Example 7)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the density of the positive electrode mixture layer immediately after pressing is 3.00 g/cc and the density D after initial activation is 2.86 g/cc. The value of (W1*R1+W2*R2)/D was 0.808. After the nail penetration test, the cell was not cleaved and the surface temperature was 74°C.

(Example 8)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. Except that the ratio R1 was 0.700, the ratio R2 was 0.300, the density of the positive electrode mixture layer immediately after pressing was 2.5 g/cc, and the density D after initial activation was 2.40 g/cc. Same as 1. The value of (W1*R1+W2*R2)/D was 0.893. After the nail penetration test, the cell was not cleaved and the surface temperature was 72°C.

(Example 9)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. Except that the ratio R1 was 0.900, the ratio R2 was 0.100, the density of the positive electrode mixture layer immediately after pressing was 2.9 g/cc, and the density D after initial activation was 2.76 g/cc. Same as 1. The value of (W1*R1+W2*R2)/D was 0.899. After the nail penetration test, the cell was not cleaved and the surface temperature was 129°C.

(Example 10)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. Except that the tap density W1 is 2.51 g/cc, the density of the positive electrode mixture layer immediately after pressing is 3.00 g/cc, the density D after initial activation is 2.86 g/cc, and the NCM D50 is 9.80 μm. are the same as in Example 1. The value of (W1*R1+W2*R2)/D was 0.769. After the nail penetration test, the cell was not cleaved and the surface temperature was 88°C.

(Example 11)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. Except that the ratio R1 was 0.950, the ratio R2 was 0.0500, the density of the positive electrode mixture layer immediately after pressing was 2.90 g/cc, and the density D after initial activation was 2.76 g/cc. Same as 1. The value of (W1*R1+W2*R2)/D was 0.930. After the nail penetration test, the cell was cleaved and the surface temperature was 142°C.

(Example 12)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W2 is 1.06 g/cc and the D90 of the LMFP is 14.6 μm. The value of (W1*R1+W2*R2)/D was 0.907. After the nail penetration test, the cell was cleaved and the surface temperature was 143°C.

(Example 13)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W1 is 2.80 g/cc, the tap density W2 is 1.06 g/cc, the NCM D50 is 14.0 μm, and the LMFP D90 is 14.6 μm. The value of (W1*R1+W2*R2)/D was 0.954. After the nail penetration test, the cell was cleaved and the surface temperature was 149°C.

(Example 14)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W1 is 2.69 g/cc, the tap density W2 is 0.690 g/cc, and the D90 of the LMFP is 7.80 μm. The value of (W1*R1+W2*R2)/D was 0.891. After the nail penetration test, the cell was not cleaved and the surface temperature was 88°C. However, the positive electrode had many streaks, was unsuitable for continuous production, and was industrially undesirable.

(Comparative example 1)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the density of the positive electrode mixture layer immediately after pressing is 2.50 g/cc and the density D after initial activation is 2.40 g/cc. The value of (W1*R1+W2*R2)/D was 0.963. After the nail penetration test, the cell was cleaved and the surface temperature was 511°C.

(Comparative example 2)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W1 is 2.85 g/cc and the NCM D50 is 17.3 μm. The value of (W1*R1+W2*R2)/D was 0.962. After the nail penetration test, the cell was cleaved and the surface temperature was 485°C.

(Comparative Example 3)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the ratio R1 is 0.900 and the ratio R2 is 0.100. The value of (W1*R1+W2*R2)/D was 0.965. After the nail penetration test, the cell was cleaved and the surface temperature was 539°C.

(Comparative Example 4)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. The tap density W1 is 2.85 g/cc, the ratio R1 is 0.700, the ratio R2 is 0.300, the density of the positive electrode mixture layer immediately after pressing is 2.50 g/cc, and the density D after initial activation is 2.50 g/cc. Same as Example 1 except 36 g/cc, NCM D50 of 17.3 μm. The value of (W1*R1+W2*R2)/D was 0.967. After the nail penetration test, the cell was cleaved and the surface temperature was 601°C.

(Comparative Example 5)
A positive electrode having physical properties shown in Table 1 was used as a positive electrode mixture layer to prepare a non-aqueous electrolyte secondary battery. It is the same as Example 1 except that the tap density W1 is 2.80 g/cc, the tap density W2 is 1.21 g/cc, the density D is 2.57 g/cc, and the NCM D50 is 14.0 μm. The value of (W1*R1+W2*R2)/D was 0.966. After the nail penetration test, the cell was cleaved and the surface temperature was 574°C.

If the value of (W1×R1+W2×R2)/D is less than 0.760, the inside of the positive electrode material mixture layer becomes too dense, so that the electrode is distorted during the pressing process during electrode production, resulting in It was not carried out because it may reduce the production efficiency.

As shown in Table 1, in Examples 1 to 14, the surface temperature after nail penetration was 149° C. or less. On the other hand, in Comparative Examples 1 to 5, the cell was cleaved and the surface temperature was as high as 485° C. or higher. In Comparative Examples 1 to 5, meltdown of the separator occurred, short circuit occurred inside the cell, and heat was generated in a chain reaction. From these results, it can be said that Examples 1 to 14 suppress heat generation at the time of short circuit and have thermal stability. Among them, Examples 1 and 4 to 10 had no industrial problem and no cell cracking was observed, so it can be said that they have particularly excellent thermal stability.

1, 1A Non-aqueous electrolyte secondary battery 2 Package 3 Electrode group 4, 118 Positive electrode 5, 115 Negative electrode 6, 114 Separator 7 Positive electrode lead 8 Positive electrode tab 9 Negative electrode lead 10 Negative electrode tab 41, 112 Positive electrode current collector 42, 113 Positive electrode Mixture layer 51 Negative electrode current collector 52 Negative electrode mixture layer 110 Case 111 Plate spring 116 Gasket 117 Cap

Claims (5)

A positive electrode for a non-aqueous electrolyte secondary battery comprising a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector,
The positive electrode mixture layer is
a first positive electrode active material which is a layered compound represented by the general formula shown in the following formula (1);
Li _a Ni _x Co _y M1 _1-xy O ₂ (where 0<a≦1.2, 0<x≦0.9, 0<y≦0.5, 0<x+y<1)... (1)
a second positive electrode active material represented by the general formula shown in the following formula (2), in which a coating made of a carbon material is formed on the surface of a phosphoric acid compound having an olivine structure;
LiMn _z M2 _b Fe _1-z-b PO ₄ (where 0<z≦0.9, 0≦b≦0.1, 0<z+b<1) (2)
a conductive material;
including
The tap density (g/cc) of the first positive electrode active material is W1, the tap density (g/cc) of the second positive electrode active material is W2, and the total weight of the first and second positive electrode active materials is R1 is the weight ratio of the first positive electrode active material when 1, and R1 is the weight ratio of the second positive electrode active material when the total weight of the first and second positive electrode active materials is 1. R2, the density of the positive electrode mixture layer calculated based on the thickness of the positive electrode for the non-aqueous electrolyte secondary battery when the charging rate of the non-aqueous electrolyte secondary battery after the initial activation treatment is 0% (g / cc) is D, the following formula (3) is satisfied,
0.760≦(W1×R1+W2×R2)/D≦0.960 (3)
A positive electrode for a non-aqueous electrolyte secondary battery, characterized by:
However, in the above formula (1), M1 is Ti, Zr, Nb, W, P, Al, Mg, V, Mn, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, at least one selected from Sn, Cu, Ag, Ce, Pr, Ge, Bi, Ba, Er, La, Sm, Yb, Sb, Bi, S and Zn;
In the above formula (2), M2 is from Ni, Co, Ti, Cu, Zn, Mg, Zr, Ca, Y, Mo, Ba, Pb, Bi, La, Ce, Nd, Gd, Al, Ga and Sr At least one selected. The median diameter of the first positive electrode active material is larger than the D90 of the second positive electrode active material,
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, characterized in that: The second positive electrode active material has a tap density W2 of 0.7 g/cc or more and 1.00 g/cc or less.
The positive electrode for non-aqueous electrolyte secondary batteries according to claim 1 or 2, characterized in that: The weight ratio R2 is 0.1 or more and 0.3 or less.
The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, characterized in that: A positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4;
a negative electrode;
a separator;
a non-aqueous electrolyte containing a lithium salt and a non-aqueous solvent;
A non-aqueous electrolyte secondary battery comprising:

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