Positive electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Abstract

To achieve an improvement in safety of a nonaqueous electrolyte secondary battery, an improvement in input / output characteristics thereof and an increase in volume energy density thereof.SOLUTION: In a positive electrode for a nonaqueous electrolyte secondary battery, a positive electrode mixture layer includes: a first positive electrode active material that is secondary particles of a layered compound represented by general formula (1), the average particle size of the secondary particles being 0.1 μm or more and less than 8 μm; a second positive electrode active material that is secondary particles of a layered compound represented by the general formula (1), the average particle size of the secondary particles being 8 μm or more and 40 μm or less; and a third positive electrode active material represented by general formula (2). Weights Wa, Wb, Wc of the first to third positive electrode active materials satisfy the following expressions (3), (4). LiaNixCoyM11-x-yO2 (0.9≤a≤1.2, 0.5≤x≤0.9, 0<y<0.5, 0<x+y<1) (1) LiMnzM2bFe1-z-bPO4 (0.5≤z≤0.9, 0≤b≤0.1, 0<z+b<1) (2) 0.8<Wa / Wb<5 (3) 2<(Wa+Wb) / Wc<5 (4)SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] In non-aqueous electrolyte secondary batteries, ions in the electrolyte are responsible for electrical conduction. Lithium secondary batteries, one type of non-aqueous electrolyte secondary battery, are used as power sources for compact electronic devices such as digital cameras and laptop computers, as well as vehicles. Non-aqueous electrolyte secondary batteries consist of a positive electrode and a negative electrode. The positive electrode comprises a positive electrode current collector and a positive electrode composite layer coated on the surface of the positive electrode current collector, which contains a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is the heart of energy storage, and various research and development efforts are underway. In particular, research is being conducted on positive electrodes that combine two different active materials to exploit the characteristics of each active material, thereby achieving superior performance compared to when each active material is used alone.

[0003] For example, in Patent Document 1, in order to improve charge / discharge characteristics, a large particle size positive electrode active material and a small particle size positive electrode active material are mixed at a certain particle size and weight ratio to increase the packing density of the positive electrode active material in the positive electrode composite layer. Furthermore, Patent Document 2 studies a positive electrode in which solid and hollow lithium nickel composite oxides having a hexagonal layer structure are mixed together and have different particle sizes. Furthermore, Patent Document 3 studies a positive electrode in which a high-capacity lithium metal oxide composed of two or more of nickel, manganese, and cobalt is mixed with a lithium metal phosphate having high thermal stability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5213305 [Patent Document 2] Japanese Patent Publication No. 2021-120937 [Patent Document 3] Patent No. 6813487 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable for non-aqueous electrolyte secondary batteries to achieve three goals: improved safety, improved input / output characteristics, and a high volumetric energy density. However, Patent Documents 1 and 2 do not consider the case where the battery is mixed with lithium metal phosphate, which is effective in improving safety. Furthermore, even when an electrode mixed with lithium metal phosphate is used as in Patent Document 3, there is still room for further study on achieving both improved input / output characteristics and a high volumetric energy density.

[0006] 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 nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery that can achieve improved safety, improved input / output characteristics, and a high volumetric energy density. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a positive electrode for a non-aqueous electrolyte secondary battery according to the present invention is a positive electrode for a non-aqueous electrolyte secondary battery including a positive electrode current collector and a positive electrode composite layer formed on a surface of the positive electrode current collector, wherein the positive electrode composite layer includes: a first positive electrode active material, which are secondary particles of a layered compound represented by the general formula shown in the following formula (1), and which have a particle diameter of 0.1 μm or more and less than 8 μm; a second positive electrode active material, which are secondary particles of the layered compound represented by the general formula shown in the following formula (1), and which have a particle diameter of 8 μm or more and 40 μm or less; and a third positive electrode active material, which is represented by the general formula shown in the following formula (2) and has an olivine structure; and wherein, when the weight of the first positive electrode active material is Wa, the weight of the second positive electrode active material is Wb, and the weight of the third positive electrode active material is Wc, the following formulas (3) and (4) are satisfied: Li a Ni x Co yM1 1-x-y O2 (However, 0 <a≦1.2、0<x≦0.9、0<y<0.5、0<x+y<1)···(1) LiMn z M2 b Fe 1-z-b PO4 (however, 0<≦0.9, 0≦b≦0.1, 0 <z+b<1)···(2) 0.8 <Wa / Wb<5 ···(3) 2<(Wa+Wb) / Wc<5 (4) In the above formula (1), M1 is at least one selected from Ti, Zr, Nb, W, P, Al, Mg, V, Mn, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, Cu, Ag, Ce, Pr, Ge, Bi, Ba, Er, La, Sm, Yb, Sb, Bi, S, and Zn; In the above formula (2), M2 is at least one selected from Ni, Co, Ti, Cu, Zn, Mg, Zr, Ca, Y, Mo, Ba, Pb, Bi, La, Ce, Nd, Gd, Al, Ga, and Sr.

[0008] Furthermore, in the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention, in the above invention, the positive electrode mixture layer is formed by coating on the positive electrode current collector, and has a coating density greater than 2.7 g / cc and less than 3.3 g / cc.

[0009] Further, in the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention, in the above invention, the positive electrode mixture layer has a basis weight of 100 g / m on one surface of the positive electrode current collector. 2 Larger, 400g / m 2 It is characterized by being smaller.

[0010] In addition, the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention is characterized in that, in the above invention, the coating density is 2.85 g / cc or more and less than 3.1 g / cc.

[0011] In addition, in the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention, in the above invention, the positive electrode mixture layer has a basis weight of 200 g / m on one side of the positive electrode current collector. 2Larger, 300g / m 2 It is characterized by being smaller. In this specification, the basis weight may also be referred to as the coating weight.

[0012] Furthermore, a nonaqueous electrolyte secondary battery according to the present invention is characterized by comprising the positive electrode for a nonaqueous electrolyte secondary battery according to the above invention, a negative electrode, a separator, and a nonaqueous electrolyte solution containing a lithium salt and a nonaqueous solvent. [Effects of the Invention]

[0013] According to the present invention, it is possible to realize improved safety, improved input / output characteristics, and a high volumetric energy density in a nonaqueous electrolyte secondary battery. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view illustrating the configuration of a nonaqueous electrolyte secondary battery including a positive electrode for a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. [Figure 2] FIG. 2 is an exploded perspective view illustrating the configuration of a nonaqueous electrolyte secondary battery including a positive electrode for a nonaqueous electrolyte secondary battery according to Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following description. Furthermore, various modifications and improvements can be made to the present embodiments, and such modifications and improvements can also be included in the present invention.

[0016] Although details will be described later, FIG. 1 is a cross-sectional view of a laminate-type nonaqueous electrolyte secondary battery, and FIG. 2 is an exploded perspective view for explaining the configuration of a coin-type nonaqueous electrolyte secondary battery. 1 and 2 show configuration examples of a laminate-type nonaqueous electrolyte secondary battery and a coin-type nonaqueous electrolyte secondary battery as examples of embodiments, but the shape of the nonaqueous electrolyte secondary battery in the present invention is not particularly limited and may be flat, cylindrical, prismatic, coin-type, etc. Furthermore, the exterior body of the nonaqueous electrolyte secondary battery is not particularly limited either and known materials such as laminate film, aluminum, aluminum alloy, and stainless steel can be used.

[0017] (Embodiment 1) Fig. 1 is a cross-sectional view illustrating the configuration of a nonaqueous electrolyte secondary battery including a positive electrode for a nonaqueous electrolyte secondary battery according to embodiment 1 of the present invention. The nonaqueous electrolyte secondary battery 1 shown in Fig. 1 is a stacked-type nonaqueous electrolyte secondary battery formed by stacking a plurality of pairs of a positive electrode 4, a negative electrode 5, and a separator 6.

[0018] The non-aqueous electrolyte secondary battery 1 includes a bag-shaped exterior body 2 made of laminate film. An electrode group 3 having a laminated structure is housed within the exterior body 2. The laminate film has a structure in which, for example, multiple (e.g., two) plastic films are stacked together with a metal foil such as aluminum foil sandwiched between adjacent plastic films. One of the two plastic films is a heat-sealable resin film. The exterior body 2 is made by stacking two laminate films with the heat-sealable resin films facing each other, and housing the electrode group 3 and non-aqueous electrolyte between these laminate films. The two laminate film portions around the electrode group 3 are heat-sealed to each other to seal, thereby hermetically housing the electrode group 3 and non-aqueous electrolyte.

[0019] 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. The separator 6 is interposed between the positive electrode 4 and the negative electrode 5. The electrode group 3 has a multi-layer structure in which the negative electrode 5 is located as the outermost layer and the separator 6 is located between the negative electrode 5 and the inner surface of the exterior body 2.

[0020] 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 .

[0021] The positive electrode current collector 41 is made of aluminum, nickel, stainless steel, titanium, other alloys, etc. Among these, it is preferable to use aluminum from the viewpoint of electronic conductivity and battery operating potential.

[0022] Positive electrode mixture layer 42 contains a first positive electrode active material, a second positive electrode active material, a third positive electrode active material, a conductive agent, and a binder, and is in the form of a film formed, for example, by applying it to positive electrode current collector 41 and drying it. The density of positive electrode mixture layer 42 is adjusted, for example, by pressing. The first to third positive electrode active materials are each capable of absorbing and desorbing lithium.

[0023] The first positive electrode active material is a secondary particle of a layered compound represented by the general formula (1) below, with a particle diameter of 0.1 μm or more and less than 8 μm. The layered compound is a lithium (Li), cobalt (Co), and nickel (Ni)-containing composite metal oxide composed of layers of sheet-like particles. The secondary particle is an agglomerate formed by the aggregation of multiple single particles (primary particles). Li a Ni x Co y M1 1-x-y O2···(1) However, in the general formula (1), M1 is at least one selected from 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), samarium (Sm), ytterbium (Yb), antimony (Sb), bismuth (Bi), sulfur (S), and zinc (Zn), and 0.9 ≦ a ≦ 1.2, 0 ≦ x ≦ 0.9, 0 < y < 0.5, and 0 < x + y < 1 are satisfied.

[0024] The second positive electrode active material is secondary particles of a layered compound represented by the general formula shown in the above formula (1), and is secondary particles having a particle diameter of 8 μm or more and 40 μm or less. Similar to the first positive electrode active material, the second positive electrode active material is an aggregate (secondary particle) formed by aggregation of a plurality of single particles (primary particles).

[0025] The molar ratio of the metal elements of each of the first positive electrode active material and the second positive electrode active material and the elements contained as M1 may be the same or different as long as they satisfy the above ranges.

[0026] When the weight of the first positive electrode active material is Wa and the weight of the second positive electrode active material is Wb, the first positive electrode active material and the second positive electrode active material satisfy the following formula (3) with respect to the ratio of the weight Wa of the first positive electrode active material to the weight Wb of the second positive electrode active material. 0.8 < Wa / Wb < 5 ···(3) Here, when the weight ratio Wa / Wb is 0.8 or less, the abundance ratio of the second positive electrode active material increases, and it becomes difficult to obtain the effect of achieving both input / output characteristics and high volumetric energy density. Further, when the weight ratio Wa / Wb is 5 or more, the abundance ratio of the first positive electrode active material increases. For example, the density after pressing tends to be low, the coating film density becomes insufficient, and it becomes difficult to obtain the effect of high volumetric energy density. Toward high volumetric energy density, it is desirable that the ratio of Wa to Wb is preferably 0.8 < Wa / Wb < 1.

[0027] The first positive electrode active material and the second positive electrode active material may be mixed with secondary particles of a layered compound represented by the general formula shown in the above formula (1) having a particle size distribution with one peak to satisfy the above formula (3), or secondary particles of a layered compound represented by the general formula shown in the above formula (1) having a particle size distribution with two or more peaks may be used to satisfy the above formula (3), or secondary particles of a layered compound represented by the general formula shown in the above formula (1) having a particle size distribution with one peak and secondary particles of a layered compound represented by the general formula shown in the above formula (1) having a particle size distribution with two or more peaks may be mixed to satisfy the above formula (3).

[0028] The third positive electrode active material is represented by the general formula shown in the following formula (2) and is a phosphate compound (olivine compound) having an olivine structure. This phosphate compound is a compound composed of manganese, iron (Fe), and lithium. LiMn z M2 b Fe 1-z-b PO4···(2) However, in the general formula (2), M2 is at least one selected from 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, 0 < z + b < 1.

[0029] The olivine-based compounds used in the third positive electrode active material are generally inexpensive and have excellent thermal stability, so their use as a positive electrode active material or addition to the positive electrode mixture layer can improve the safety of batteries.

[0030] The average particle size of the third positive electrode active material is preferably smaller than 4.0 μm. If the average particle size is larger than 4.0 μm, the particle size will be the same as or larger than that of the first positive electrode active material, preventing uniform distribution of the first positive electrode active material, the second positive electrode active material, and the conductive agent. The third positive electrode active material has low electronic conductivity, which inhibits electronic conductivity in the composite layer, resulting in a decrease in input / output characteristics. The third positive electrode active material may be coated with a coating made of a carbon material. The carbon material is a conductive carbon material. The coating made of the carbon material is present on at least a portion of the surface of the primary particles of the second positive electrode active material. The purity of the carbon and the thickness of the carbon coating can be selected arbitrarily, but it is preferable to control the weight ratio of the carbon material to the total weight of the second positive electrode active material so that it is 0.1% or more and 5% or less.

[0031] Furthermore, when the weight of the third positive electrode active material is Wc, the ratio of the sum of the weights of the first and second positive electrode active materials (Wa+Wb) to the weight Wc of the third positive electrode active material satisfies the following formula (4): 2<(Wa+Wb) / Wc<5 (4) Here, when the ratio (Wa + Wb) / Wc is 2 or less, the abundance ratio of the third positive electrode active material becomes large, and electronic conductivity decreases, resulting in poor input / output characteristics. In addition, the coating density after pressing is low, and the volumetric energy density decreases. When the ratio (Wa + Wb) / Wc is greater than 3 but less than 5, the abundance ratio of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material becomes more appropriate, allowing the coating density after pressing to be high while maintaining high input / output characteristics. Furthermore, when the ratio (Wa + Wb) / Wc is 5 or more, the abundance ratio of the first and second positive electrode active materials becomes large, and even if the input / output characteristics and volumetric energy density are improved, it becomes difficult to obtain the thermal stability effect of the third positive electrode active material.

[0032] Here, the larger the particle size of the secondary particles of the active material, the larger the weight of the active material per unit volume and the higher the volumetric energy density.Furthermore, the larger the particle size of the secondary particles of the active material, the lower the electronic conductivity, resulting in insufficient contact with the conductive agent and making it difficult to form a conductive path.

[0033] Typically, electrochemical reactions in the positive electrode mixture layer proceed through the transfer of electrons via a conductive agent present near large-diameter secondary particles (hereinafter referred to as first secondary particles). However, small-diameter secondary particles (hereinafter referred to as second secondary particles) are believed to have higher electronic conductivity than the first secondary particles due to their different particle sizes. Therefore, when the second secondary particles are present in the positive electrode mixture layer 42, electrons are not only transferred via the conductive agent, but also function as a conductive path to transfer electrons. As a result, when the positive electrode mixture layer 42 contains the second secondary particles, the electrode resistance is reduced and input / output characteristics are improved. Furthermore, although some secondary particles have irregular shapes, they are generally roughly spherical, which is thought to result in the formation of voids between the secondary particles. The well-balanced presence of small-diameter secondary particles and conductive agent in weight ratios allows the second secondary particles and conductive agent to fill the voids, improving electronic conductivity and, by forming a denser structure, improving coating density and volumetric energy density.

[0034] Furthermore, the coating density of the positive electrode composite layer 42 on the positive electrode current collector 41 is preferably greater than 2.7 g / cc and less than 3.3 g / cc. If the coating density is 2.7 g / cc or less, the conductive agent and the active materials will not be in sufficient contact with each other, resulting in poor input / output characteristics. If the coating density is 3.3 g / cc or more, the conductive agent and the active materials will have an excessively dense structure, making thermal runaway more likely to occur during a short circuit, for example. For better input / output characteristics, the coating density is preferably greater than 2.85 g / cc and less than 3.0 g / cc.

[0035] One surface of the positive electrode mixture layer 42 is coated on the positive electrode current collector 41 in an amount of 100 g / m 2Larger, 400g / m 2 This means that when both sides are coated, the basis weight of one of the two sides is 100 g / m 2 Larger, 400g / m 2 When coated on one side, the weight of each side is 100g / m 2 Larger, 400g / m 2 It means that the weight is smaller than 100g / m 2 In the following cases, the amount of active material is insufficient, so it is necessary to increase the number of electrode layers or the amount of winding in order to improve the energy density. However, the total amount of current collectors that are not directly involved in lithium insertion / extraction increases, which reduces the weight and volume energy density. In addition, it is not possible to obtain sufficient coating density during coating (pressing), which reduces the volume energy density. When the coating weight is 400 g / m 2 If the coating weight exceeds 200 g / m, the positive electrode mixture layer 42 becomes thicker, the distance from the positive electrode current collector 41 to the non-aqueous electrolyte interface becomes longer, the electrode resistance increases, and the input / output characteristics deteriorate. In addition, cracks are likely to occur after the coated positive electrode mixture layer 42 dries, and the handling of the electrode deteriorates. For better input / output characteristics, the coating weight is 200 g / m. 2 Larger, 300g / m 2 Smaller is better.

[0036] In this specification, the particle size refers to the particle size of each particle determined using a laser diffraction particle size analyzer, and the average particle size refers to the particle size (D50) at which the relative particle amount is 50% as measured by the laser diffraction / scattering method described in JIS standard Z8825:2013.

[0037] Furthermore, whether the particle size, mixing ratio, coating density, and basis weight of the first positive electrode active material, second positive electrode active material, and third positive electrode active material in the prepared positive electrode composite layer satisfy the requirements of the present invention can be confirmed by the method described below. The nonaqueous electrolyte secondary battery is disassembled in a glove box filled with an inert gas such as argon, and the positive electrode 4 is removed. The positive electrode 4 is washed with an appropriate nonaqueous organic solvent (e.g., dimethyl carbonate) and then dried to remove the solvent. The positive electrode 4 is then immersed in a solvent such as N-methyl-2-pyrrolidone and ultrasonically separated to remove the positive electrode composite layer 42 from the positive electrode current collector 41. The solvent in which the separated positive electrode composite layer 42 is dispersed can be centrifuged to separate the individual substances in the positive electrode composite layer 42. The particle size distribution of each of the removed substances can be measured on a volume basis using a laser diffraction particle size distribution analyzer, thereby measuring the particle size and mixing ratio of each active material contained in the positive electrode composite layer 42. The laser diffraction particle size distribution analyzer may be an SALD-2300 (Shimadzu Corporation). The coating density can be measured using a cleaned positive electrode 4. The positive electrode 4 is punched using a punching tool capable of punching out a desired area, the weight of the punched positive electrode 4 is measured using an electronic balance, and the thickness of the punched positive electrode 4 is measured using a micrometer or film thickness gauge. The coating weight can be determined from the weight and area of ​​the positive electrode 4 punched out during coating density measurement. The nonaqueous electrolyte secondary battery used above may be subjected to initial activation or charge / discharge cycling in any step. It is preferable to fully discharge the positive electrode 4 to the minimum voltage assumed by the manufacturer before removing it. Furthermore, there is no significant difference in density between a positive electrode before assembly into a nonaqueous electrolyte secondary battery and a positive electrode fully discharged to the minimum voltage of a nonaqueous electrolyte secondary battery.

[0038] The conductive agent assists electron conduction in the positive electrode. The conductive agent is not particularly limited, and known conductive agents can be used. Examples of conductive agents include conductive carbon powders such as carbon blacks such as acetylene black and ketjen black, carbon nanotubes, carbon nanofibers, graphene, activated carbon, and graphite. The conductive agent may be made of a single material or multiple materials (e.g., a first conductive agent and a second conductive agent).

[0039] The binder binds the positive electrode current collector, the positive electrode active material, and the conductive agent. There are no particular limitations on the binder, and known or commercially available binders can be used. Examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and styrene-butadiene rubber (Styrene-Butadiene Examples of such rubbers include SBR, butadiene rubber, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), butyl rubber, poly(meth)acrylate (PMMA), polyethylene oxide (PEO), polypropylene oxide (PO), polyepichlorohydrin, polyphosphazene, and polyacrylonitrile.

[0040] Negative electrode 5 is composed of a negative electrode current collector 51 and a negative electrode mixture layer 52 containing a negative electrode active material formed on one or both surfaces of negative electrode current collector 51 or metallic lithium (not shown).

[0041] Although there is no particular limitation on the negative electrode current collector 51, it is preferable to use a metal. Suitable metals include aluminum foil and copper, and depending on the application, a porous aluminum current collector may also be used. Among these, copper is preferable from the viewpoint of electronic conductivity and battery operating potential.

[0042] The negative electrode mixture layer 52 contains, as an active material, at least one selected from, for example, a lithium alloy, a titanium-niobium alloy, graphite, amorphous carbon, a transition metal composite oxide (e.g., Li4Ti5O12 or TiNb2O7), an alloy capable of absorbing and desorbing lithium, and silicon. Among these, graphite is preferred because it has an operating potential very close to that of metallic lithium, allows charging and discharging at a high operating voltage, and has excellent cycle characteristics. Graphite may also be used in combination with other negative electrode active materials. The negative electrode mixture layer 52 also contains a binder. The negative electrode mixture layer may also contain a conductive agent. The binder and conductive agent may be the same materials as those used in the positive electrode 4.

[0043] The separator 6 is disposed between the positive electrode and the negative electrode and has a porosity that allows the components of the non-aqueous electrolyte to pass through. The separator 6 is formed, for example, using a porous sheet separator made of polymer or fiber, a nonwoven fabric separator, or the like. The separator 6 may be made of a material such as polyethylene, polypropylene, aramid, or polyimide, or may have multiple layers of different materials including these. However, from the viewpoint of providing a shutdown function in the event of heat generation, it is preferable that the separator 6 has a layer containing polyethylene. The pore size of the separator 6 is preferably 0.01 to 10 μm, and the thickness is preferably 5 to 30 μm. The separator 6 may also be formed by laminating a ceramic layer as a heat-resistant insulating layer on a porous substrate. When a solid electrolyte is used as the non-aqueous electrolyte, the separator 6 may not be present.

[0044] The positive electrode leads 7 extend downward from the positive electrode composite layer 42, for example, as shown in FIG. 1. As an example, each positive electrode lead 7 is a portion of the positive electrode current collector 41 that is not coated with the positive electrode composite layer 42. The positive electrode leads 7 are bundled and joined to each other at the end opposite to the positive electrode composite layer 42 side within the exterior body 2.

[0045] One end of the positive electrode tab 8 is joined to the positive electrode lead 7, and the other end passes through the sealing portion of the exterior body 2 and extends to the outside.

[0046] The negative electrode leads 9 each extend upward from the negative electrode composite material layer 52, for example, as shown in FIG. 1. They may extend in the same direction as the positive electrode lead 7, provided that they do not come into contact with the positive electrode lead 7. As an example, each negative electrode lead 9 is a portion of the negative electrode current collector 51 that is not coated with the negative electrode composite material layer 52. The negative electrode leads 9 are bundled and joined to each other at the end opposite to the negative electrode composite material layer 52 side within the exterior body 2.

[0047] One end of the negative electrode tab 10 is joined to the negative electrode lead 9, and the other end passes through the sealing portion of the exterior body 2 and extends to the outside.

[0048] The nonaqueous electrolyte may be a nonaqueous electrolytic solution or a solid electrolyte. The following describes the nonaqueous electrolytic solution in particular. The nonaqueous electrolytic solution is enclosed within the exterior body 2. The nonaqueous electrolytic solution injection portion of the exterior body 2 is sealed after the nonaqueous electrolytic solution is injected. The nonaqueous electrolytic solution contains an electrolyte and a nonaqueous solvent.

[0049] The electrolyte is not particularly limited, and any lithium salt commonly used in non-aqueous electrolyte secondary batteries can be used. For example, LiPF, LiAsF, LiBF, LiCF, SO, LiN(C m F 2m+1 SO2)(C n F 2n+1 SO2) (m and n are integers of 1 or more), LiC(C s F 2s+1 SO2)(C t F 2t+1 SO2)(C u F 2u+1Examples of electrolytes that can be used include lithium difluoro(oxalato)borate (SO2) (s, t, and u are integers of 1 or greater). These electrolytes may be used alone or in combination of two or more. From the viewpoints of lithium ion conductivity, viscosity of the electrolyte solution, temperature characteristics of conductivity, etc., it is desirable that the electrolyte has a concentration of 0.1 to 3 mol / L, preferably 0.5 to 1.5 mol / L.

[0050] The non-aqueous solvent contains a cyclic carbonate and / or a 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 dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). 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.

[0051] Furthermore, for the purpose of forming a high-quality coating on the surface of the negative electrode active material by reductive decomposition during charge and discharge, the nonaqueous electrolyte may contain additives other than the lithium salt. The additives are not particularly limited, but examples include vinylene carbonate, fluoroethylene carbonate, 1,3,2-dioxathiolane 2,2-dioxide (MMDS), 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide, tris(trimethylsilyl) phosphite, 1-propene 1,3-sultone, and Li2PO2F2. These additives may be used alone or in combination. They may also be used in combination with other additives. Furthermore, other additives may also be used alone.

[0052] In the present embodiment 1, the positive electrode 4 of the nonaqueous electrolyte secondary battery 1 includes a positive electrode composite layer 42 having a first positive electrode active material represented by general formula (1) and a particle diameter of 0.1 μm or more and less than 8 μm, a second positive electrode active material represented by general formula (1) and a particle diameter of 8 μm or more and 40 μm or less, the particle diameter of which is different from that of the first positive electrode active material, and a third positive electrode active material having an olivine structure represented by general formula (2), wherein the weight ratio of the first and second positive electrode active materials satisfies the above formula (3), and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material satisfies the above formula (4). According to the present embodiment 1, the abundance ratios of the first to third positive electrode active materials satisfy the above conditions, thereby enabling the nonaqueous electrolyte secondary battery 1 to achieve improved safety, improved input / output characteristics, and a high volumetric energy density.

[0053] (Embodiment 2) 2 is an exploded perspective view illustrating the configuration of a nonaqueous electrolyte secondary battery including a positive electrode for a nonaqueous 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 composite layer 113, separator 114, negative electrode 115, gasket 116, and cap 117. Positive electrode current collector 112 and positive electrode composite layer 113 form positive electrode 118.

[0054] In nonaqueous electrolyte secondary battery 1A, case 110 and cap 117 are fixed together by crimping or the like, and the battery is filled with a nonaqueous electrolyte. Nonaqueous electrolyte secondary battery 1A is liquid-tightly sealed by case 110, gasket 116, and cap 117. Furthermore, positive electrode current collector 112, positive electrode composite layer 113, separator 114, and negative electrode 115 are biased toward cap 117 by leaf spring 111. This keeps the components in close contact with each other.

[0055] The positive electrode current collector 112 is made of the same material as the positive electrode current collector 41 . Positive electrode mixture layer 113 has a configuration similar to that of positive electrode mixture layer 42.

[0056] Separator 114 is a porous disk-shaped material and is provided between positive electrode 115 and negative electrode 115. Separator 114 has the same structure as separator 6.

[0057] The nonaqueous electrolyte may be the same as that of the first embodiment.

[0058] The negative electrode 115 has the same configuration as the negative electrode 5 .

[0059] In the present second embodiment, in the positive electrode 118 of the nonaqueous electrolyte secondary battery 1A, the positive electrode composite layer 113 includes a first positive electrode active material represented by general formula (1) and having a particle diameter of 0.1 μm or more and less than 8 μm, a second positive electrode active material represented by general formula (1) and having a particle diameter of 8 μm or more and 40 μm or less, the particle diameter of which is different from that of the first positive electrode active material, and a third positive electrode active material having an olivine structure represented by general formula (2), wherein the weight ratio of the first and second positive electrode active materials satisfies the above formula (3), and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material satisfies the above formula (4). According to the present second embodiment, the abundance ratio of the first to third positive electrode active materials satisfies the above condition, thereby realizing improved safety, improved input / output characteristics, and a high volumetric energy density in the nonaqueous electrolyte secondary battery 1A. [Example]

[0060] The present invention will be described in more detail below by way of examples, but the present invention is not limited to the following examples in any way.

[0061] <How to make the positive electrode> Li with an average particle size of 5 μm 1.1 Co 0.2 Ni 0.5 Mn 0.3 O2 (hereinafter sometimes referred to as small particle size NCM), Li with an average particle size of 16 μm 1.1 Co 0.2 Ni 0.5 Mn 0.3 O2 (hereinafter sometimes referred to as large particle size NCM), LiMn with an average particle size of 0.89 μm 0.6 Fe 0.4A positive electrode active material slurry was prepared by mixing appropriate amounts of PO4 (hereinafter sometimes referred to as LMFP), acetylene black (AB) and conductive carbon as conductive agents, and N-methyl-2-pyrrolidone (NMP) as a binder and viscosity adjusting solvent. The weight ratio of the positive electrode active material slurry was 94:3:2:1 (the sum of the weight of the small particle size NCM, the weight of the large particle size NCM, and the weight of the LMFP):AB:conductive carbon:binder).

[0062] The obtained positive electrode active material slurry was applied to both sides of a positive electrode current collector and dried to form a positive electrode mixture layer, thereby producing a positive electrode.

[0063] <Method for producing the negative electrode> A negative electrode slurry was prepared by mixing 96.7 wt % graphite as the negative electrode active material, 0.3 wt % acetylene black as a conductive agent, 1.5 wt % styrene-butadiene rubber as a binder, 1.5 wt % carboxymethyl cellulose as a thickener, and an appropriate amount of ion-exchanged water as a viscosity adjusting solvent.

[0064] The prepared negative electrode active material slurry was applied to both sides of a negative electrode current collector and dried to form a negative electrode mixture layer, thereby producing a negative electrode.

[0065] <Preparation of non-aqueous electrolyte> A non-aqueous electrolyte solution was prepared by dissolving 1.3 mol / L of LiPF6 as a lithium salt and 3 wt% of vinylene carbonate as an additive in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a volume ratio of 2:5:3.

[0066] <Fabrication of Non-Aqueous Electrolyte Secondary Battery> The prepared electrode was pressed to a predetermined coating density using a bench-top roll press with the gap set to an arbitrary value. Two laminate films were prepared as exterior bodies, each 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. The heat-sealable resin layers of the two laminate films were arranged facing each other, and the laminate films were overlapped with their adhesive surfaces facing each other so that electrode groups could be accommodated in the two accommodating recesses. The electrode groups were arranged so that the portions where the heat-sealable resin parts of each terminal were formed passed between the edges of the two laminate films, leaving a portion of each terminal exposed to the outside. In this state, the heat-sealable resin layers of the laminate films were heat-sealed along the three edges, including the two edges from which the tabs of the laminate films extended. Next, the electrolyte solution prepared above was injected into the one edge of the exterior body that was not heat-sealed. Next, the remaining edge of the exterior body was heat-sealed under reduced pressure to produce a nonaqueous electrolyte secondary battery (cell).

[0067] <Particle size measurement> The average particle sizes of small-particle NCM, large-particle NCM, and LMFP were determined by the particle size (D50) at which the relative particle amount on a number basis reached 50%, as measured by the laser diffraction / scattering method described in JIS standard Z8825: 2013. A laser diffraction particle size distribution analyzer, SALD-2300 (Shimadzu Corporation), was used for the measurements.

[0068] <Measurement of coating density> The pressed electrode was punched out using a φ13.5 punch, and the thickness and area of ​​the punched electrode and the weight excluding the calculated weight of the current collector were determined, and the density of the coating was calculated by dividing the weight by the product of the thickness and the area.

[0069] <Measurement of basis weight> The electrode was punched out using a φ13.5 punch, and the area of ​​the punched electrode and the weight excluding the calculated weight of the current collector were determined, and the weight was calculated by dividing the weight by the area.

[0070] <Charge / discharge by rate> As shown in Table 1, the fabricated cells were placed in a thermostatic chamber at 25°C for 24 hours and then subjected to an initial charge-discharge cycle at 0.1C with an upper limit voltage of 4.3V, a lower limit voltage of 2.75V, and a charge-discharge cycle at 0.2C. Activation was then performed by repeating this cycle four times with an upper limit voltage of 4.3V, a lower limit voltage of 2.75V, and a charge-discharge cycle at 0.2C. After activation, rate-dependent charge-discharge tests were initiated. Rate-dependent charge-discharge tests were performed with a fixed charge rate and varying discharge rates. The charge rate was 0.5C, and the discharge rates were 0.2C, 0.5C, 1.0C, 2.0C, 3.0C, 4.0C, and 5.0C. For each rate (1.0C to 5.0C), the capacity ratio was calculated as the ratio of the capacity (Ah) at each rate to the initial capacity (Ah) at 0.2C, which was taken as 100%. [Table 1]

[0071] <Volumetric energy density measurement> The charge / discharge capacity and density of the negative electrode were kept constant, and the full cell capacity was calculated using the capacity and electrode density during the initial charge / discharge at 0.1C with an upper limit voltage of 4.3V, a lower limit voltage of 2.75V, and the average discharge voltage set to 3.7V. The volumetric energy density (Wh / L) was calculated when the cell was housed in an exterior body of the same volume.

[0072] <Nail penetration test> The fabricated non-aqueous electrolyte secondary battery (cell) was previously subjected to constant current-constant voltage charging (cutoff current: 0.05C) with an upper limit voltage of 4.2V and a current value of 0.5C. A nail (stainless steel, 3mm diameter) was driven into the center of this cell at a nail penetration speed of 0.1mm / sec and a nail penetration depth of 1mm. The appearance of the cell was checked one hour after the nail penetration to confirm the presence or absence of cracking in areas other than the nail penetration area. This test was based on the international standard IEC TR 62660-4.

[0073] Example 1 A cell was fabricated using a positive electrode having the physical properties (coating amount and coating density) and weight ratio of small-particle-size NCM, large-particle-size NCM, and LMFP shown in Table 2 as the positive electrode composite layer. In Example 1, the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 64:16:20, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 4.55, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 1 are shown in Table 2. [Table 2]

[0074] Example 2 Example 2 was the same as Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 40:40:20, and the electrode density was 2.91 g / cc. In Example 2, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 1.78, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Example 2 are shown in Table 2.

[0075] Example 3 Example 3 was the same as Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 16:64:20, and the electrode density was 2.92 g / cc. In Example 3, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.85, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 3 are shown in Table 2.

[0076] Example 4 Example 4 was similar to Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 14:56:30, and the electrode density of the positive electrode was 2.85 g / cc. In Example 4, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.85, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 2.30. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 4 are shown in Table 2.

[0077] Example 5 Example 5 was the same as Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 61.4:18.6:20, and the electrode density was 2.90 g / cc. In Example 5, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 4.00, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 5 are shown in Table 2.

[0078] Example 6 Example 6 was the same as Example 5, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 15:60:25. In Example 6, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.86, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 3.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 6 are shown in Table 2.

[0079] Example 7 Example 7 was similar to Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 16:64:20, and the electrode density was 2.80 g / cc. In Example 7, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.85, and the ratio of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material ((Wa+Wb) / Wc) was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 7 are shown in Table 2.

[0080] Example 8 Example 8 was the same as Example 7, except that the electrode density of the positive electrode in the electrode was 3.10 g / cc. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5 C to the capacity ratio at 1 C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 8 are shown in Table 2.

[0081] Example 9 In Example 9, the coating amount of the positive electrode in the electrode was 100 g / m 2 The electrode density was 2.90 g / cc, which was the same as in Example 7. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5 C relative to the capacity ratio at 1 C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 9 are shown in Table 3. [Table 3]

[0082] Example 10 In Example 10, the coating amount of the positive electrode in the electrode was 200 g / m 2 The rest of the experiment was the same as in Example 9. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 10 are shown in Table 3.

[0083] Example 11 In Example 11, the coating amount of the positive electrode in the electrode was 300 g / m 2 The rest of the experiment was the same as in Example 9. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 11 are shown in Table 3.

[0084] Example 12 In Example 12, the coating amount of the positive electrode in the electrode was 400 g / m 2 The rest of the experiment was the same as in Example 9. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Example 12 are shown in Table 3.

[0085] (Comparative Example 1) Comparative Example 1 was the same as Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 80:0:20, and the electrode density was 2.80 g / cc. Comparative Example 1 was constructed with a positive electrode composite layer that did not contain a second positive electrode active material. In Comparative Example 1, the ratio ((Wa + Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 1 are shown in Table 2.

[0086] (Comparative Example 2) Comparative Example 2 was the same as Example 1, except that the ratio of the weight of the small-particle-size NCM to the weight of the large-particle-size NCM to the weight of the LMFP in the electrode was 0:80:20, and the electrode density was 2.90 g / cc. Comparative Example 2 was constructed with a positive electrode composite layer that did not contain a first positive electrode active material. In Comparative Example 2, the ratio ((Wa + Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 2 are shown in Table 2.

[0087] (Comparative Example 3) Comparative Example 3 was the same as Comparative Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 13.5:66.5:20. In Comparative Example 3, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.78, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 3 are shown in Table 2.

[0088] Comparative Example 4 Comparative Example 4 was the same as Comparative Example 1, except that the weight ratio of small particle size NCM to large particle size NCM to LMFP in the electrode was 66.7:13.3:20. In Comparative Example 4, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 5.23, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 4.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 4 are shown in Table 2.

[0089] (Comparative Example 5) Comparative Example 5 was the same as Comparative Example 1, except that the weight ratio of small particle size NCM to large particle size NCM to LMFP in the electrode was 13:52:35. In Comparative Example 5, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.85, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 1.86. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 5 are shown in Table 2.

[0090] (Comparative Example 6) Comparative Example 6 was similar to Comparative Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 16.7:66.7:16.6, and the electrode density was 2.96 g / cc. In Comparative Example 6, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.85, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 5.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Comparative Example 6 are shown in Table 2.

[0091] (Comparative Example 7) Comparative Example 7 was the same as Comparative Example 1, except that the weight ratio of small-particle-size NCM to large-particle-size NCM to LMFP in the electrode was 17.5:70:12.5. In Example 7, the weight ratio (Wa / Wb) of the first and second positive electrode active materials was 0.86, and the ratio ((Wa+Wb) / Wc) of the sum of the weights of the first and second positive electrode active materials to the weight of the third positive electrode active material was 7.00. After charge / discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C relative to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was conducted. The physical properties and test results for Comparative Example 7 are shown in Table 2.

[0092] (Comparative Example 8) In Comparative Example 8, the coating amount of the positive electrode in the electrode was 100 g / m 2 The electrode density was 2.90 g / cc, which was the same as Comparative Example 3. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5 C relative to the capacity ratio at 1 C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results for Comparative Example 8 are shown in Table 2.

[0093] (Comparative Example 9) In Comparative Example 9, the coating amount of the positive electrode in the electrode was 200 g / m 2 The other conditions are the same as those of Comparative Example 8. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results of Comparative Example 9 are shown in Table 3.

[0094] (Comparative Example 10) In Comparative Example 10, the coating amount of the positive electrode in the electrode was 300 g / m 2 The other conditions are the same as those of Comparative Example 8. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results of Comparative Example 10 are shown in Table 3.

[0095] (Comparative Example 11) In Comparative Example 11, the coating amount of the positive electrode in the electrode was 400 g / m 2The other conditions are the same as those of Comparative Example 8. After the charge-discharge treatment, the capacity ratio at each rate, the capacity ratio at 5C to the capacity ratio at 1C, and the volumetric energy density were calculated. Finally, a nail penetration test was performed. The physical properties and test results of Comparative Example 11 are shown in Table 3.

[0096] In Comparative Example 1, the ratio of the capacity at 5C to the capacity at 1C was 0.47 compared to Examples 1 to 8, and the input / output characteristics were equivalent, but the volumetric energy density was lower at 440 Wh / L. Furthermore, in Comparative Example 2, the volumetric energy density was 449 Wh / L, equivalent to Example 1, but the ratio of the capacity at 5C to the capacity at 1C was lower at 0.29. Furthermore, in Comparative Example 3, the volumetric energy density was 445 Wh / L, equivalent to Example 7, but the ratio of the capacity at 5C to the capacity at 1C was lower at 0.39. Furthermore, in Comparative Example 4, the ratio of the capacity at 5C to the capacity at 1C was 0.46, which was similar to Examples 3 and 4, but the volumetric energy density was lower at 432 Wh / L. Furthermore, in Comparative Example 5, the ratio of the capacity at 5C to the capacity at 1C was lower at 0.39, and the volumetric energy density was also lower at 432 Wh / L. In Comparative Examples 6 and 7, cracking was observed in the nail penetration test, posing safety issues. In contrast, in Examples 1 to 8, the ratio of the capacity at 5C to the capacity at 1C was 0.40 or more, the volumetric energy density was greater than 440 Wh / L, and no splitting occurred in the nail penetration test. Compared to Comparative Examples 1 to 7, Examples 1 to 8 can be said to have achieved three things: safety, high volumetric energy density, and good input / output characteristics. Furthermore, Example 9 has a higher capacity ratio at 5C relative to the capacity ratio at 1C compared to Comparative Example 8. Example 10 has a higher capacity ratio at 5C relative to the capacity ratio at 1C compared to Comparative Example 9. Example 11 has a higher capacity ratio at 5C relative to the capacity ratio at 1C compared to Comparative Example 10. Example 12 has a higher capacity ratio at 5C relative to the capacity ratio at 1C compared to Comparative Example 11. The above shows that when the coating weights are the same, the capacity ratio at 5C is higher relative to the capacity ratio at 1C. It can be said that the present invention achieves three goals: safety, high volumetric energy density, and good input / output characteristics, even when the coating weight is changed. [Explanation of symbols]

[0097] 1, 1A non-aqueous electrolyte secondary battery 2. Exterior body 3 electrode groups 4, 118 positive electrode 5, 115 negative electrode 6, 114 Separator 7 Positive lead 8 Positive tab 9 Negative lead 10 Negative electrode tab 41, 112 Positive electrode current collector 42, 113 Positive electrode composite layer 51 Negative electrode current collector 52 Negative electrode composite layer 110 cases 111 Leaf spring 116 Gasket 117 Cap

Claims

1. A positive electrode for a non-aqueous electrolyte secondary battery, comprising: a positive electrode current collector; and a positive electrode mixture layer formed on a surface of the positive electrode current collector, The positive electrode mixture layer is a first positive electrode active material, which is secondary particles of a layered compound represented by the following general formula (1), and which has a particle diameter of 0.1 μm or more and less than 8 μm; Li ａ Ni ｘ Co ｙ M1 １－ｘ－ｙ O ２ (where 0.9≦a≦1.2, 0.5≦x≦0.9, 0<y<0.5, 0<x+y<1) ... (1) a second positive electrode active material, which is secondary particles of a layered compound represented by the general formula (1) above and has a particle diameter of 8 μm or more and 40 μm or less; a third positive electrode active material represented by the general formula (2) below and having an olivine structure; LiMn ｚ M2 ｂ Fe １－ｚ－ｂ P.O. ４ (where 0.5≦z≦0.9, 0≦b≦0.1, 0<z+b<1) ... (2) Including, the positive electrode mixture layer has a basis weight per surface of the positive electrode current collector that is greater than 100 g / m 2 and less than 400 g / m 2 ; When the weight of the first positive electrode active material is Wa, the weight of the second positive electrode active material is Wb, and the weight of the third positive electrode active material is Wc, the following formulas (3) and (4) are satisfied: 0.8<Wa / Wb<5...(3) 2<(Wa+Wb) / Wc<5...(4) A positive electrode for a non-aqueous electrolyte secondary battery. In the general formula (1), M1 is at least one selected from 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), and zinc (Zn); In general formula (2), M2 is at least one selected from 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), and strontium (Sr).

2. The positive electrode mixture layer is The coating is formed on the positive electrode current collector, The coating density is greater than 2.7 g / cc and less than 3.3 g / cc.

2. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1.

3. The coating density is 2.85 g / cc or more and less than 3.1 g / cc; 3. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 2.

4. The positive electrode mixture layer has a weight per unit area of ​​200 g / m ２ Larger, 300 g / m ２ smaller than, 2. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1.

5. The 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 solution containing a lithium salt and a non-aqueous solvent; A non-aqueous electrolyte secondary battery comprising:

Images