Positive electrode plate for non-aqueous electrolyte secondary battery, manufacturing method, and non-aqueous electrolyte secondary battery

Abstract

To provide a positive electrode plate that can suppress an increase in output resistance and a decrease in charging capacity, a method for manufacturing the same, and a non-aqueous electrolyte secondary battery including the positive electrode plate. [Solution] A positive electrode plate for a non-aqueous electrolyte secondary battery comprising a positive electrode composite layer and a positive electrode core material, wherein the positive electrode core material contains aluminum, the positive electrode composite layer comprises a positive electrode active material and at least one heterocyclic compound represented by formula (1) or formula (2), the positive electrode active material is a lithium transition metal composite oxide containing lithium and nickel, the nickel content in the lithium transition metal composite oxide is 70 mol% or more relative to the total number of moles of metal elements other than lithium, the pH of the filtrate obtained by adding 25 g of the positive electrode active material to 50 g of pure water, stirring for 5 minutes, and filtering is 11.8 to 12.5, and the content of the heterocyclic compound in the positive electrode composite layer is 0.01 to 0.5 mass% relative to the mass of the positive electrode composite layer.

Description

Technical Field

[0001] The present disclosure relates to a positive electrode plate for a non-aqueous electrolyte secondary battery, and further relates to a method for manufacturing the same and a non-aqueous electrolyte secondary battery including the same.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2011-113825 (Patent Document 1) proposes a positive electrode material for a lithium ion secondary battery including a positive electrode active material having a high nickel content.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a positive electrode plate including a positive electrode active material having a high nickel content is used in a lithium ion secondary battery, while high capacity can be achieved, the output resistance tends to increase.

[0005] An object of the present disclosure is to provide a positive electrode plate capable of suppressing an increase in output resistance and suppressing a decrease in charge capacity, a method for manufacturing the same, and a non-aqueous electrolyte secondary battery including the positive electrode plate.

Means for Solving the Problems

[0006] [1] A positive electrode plate for a non-aqueous electrolyte secondary battery including a positive electrode composite layer and a positive electrode core material, wherein the positive electrode core material contains aluminum, the positive electrode composite layer includes a positive electrode active material and the following formula (1):

Chemical Formula

Chemical formula

[10] A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery according to [8], wherein the positive electrode active material and the heterocyclic compound are mixed such that the content of the heterocyclic compound is 0.01 to 0.5% by mass relative to the solid content in the positive electrode mixture slurry.

[11] A non-aqueous electrolyte secondary battery comprising a positive electrode plate for a non-aqueous electrolyte secondary battery as described in any of [1] to [7]. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a positive electrode plate that can suppress an increase in output resistance and suppress a decrease in charging capacity, a method for manufacturing the same, and a non-aqueous electrolyte secondary battery including the positive electrode plate. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of the layer configuration of a positive electrode plate. [Figure 2] Figure 2 is a schematic flowchart of the manufacturing method of the positive electrode plate in this embodiment. [Figure 3] Figure 3 is a schematic diagram showing an example of the battery configuration in this embodiment. [Figure 4] Figure 4 is a schematic diagram showing an example of the configuration of the electrode body in this embodiment. [Modes for carrying out the invention]

[0009] <Positive plate for non-aqueous electrolyte secondary batteries> The positive electrode plate for a non-aqueous electrolyte secondary battery (hereinafter also referred to as the positive electrode plate) of this disclosure comprises a positive electrode composite layer and a positive electrode core material. The positive electrode core material contains aluminum (Al), and the positive electrode composite layer comprises a positive electrode active material and at least one heterocyclic compound represented by formula (1) or formula (2) (hereinafter also referred to as the heterocyclic compound). The positive electrode active material is a lithium transition metal composite oxide containing lithium (Li) and nickel (Ni), and the Ni content in the lithium transition metal composite oxide (hereinafter also referred to as the Ni content) is 70 mol% or more relative to the total number of moles of metal elements other than Li. The pH of the filtrate obtained by adding 25 g of the positive electrode active material to 50 g of pure water, stirring for 5 minutes, and filtering (hereinafter also referred to as the first pH) is 11.8 or more and 12.5 or less. The content of the heterocyclic compound in the positive electrode composite layer is 0.01 to 0.5 mass% relative to the mass of the positive electrode composite layer.

[0010] According to this disclosure, it is possible to suppress the increase in output resistance and the decrease in charging capacity of a non-aqueous electrolyte secondary battery (hereinafter also referred to as "battery"). The inventors have found that the increase in output resistance that occurs when a positive electrode plate containing a positive electrode active material with a high Ni content is due to the corrosion of Al at the interface between the positive electrode active material and the positive electrode core material containing Al. This is because positive electrode active materials with a high Ni content have a high alkali content, and alkaline components tend to be easily released from the positive electrode active material. When the positive electrode active material comes into contact with the positive electrode core material containing Al, the alkaline components released at the interface corrode the positive electrode core material containing Al. In the positive electrode plate of this disclosure, by using a positive electrode active material with a high Ni content, a decrease in charging capacity is suppressed. Furthermore, since the heterocyclic compound is adsorbed on the surfaces of both the positive electrode active material and the positive electrode core material containing Al, direct contact between the positive electrode active material and the positive electrode core material containing Al is suppressed. In addition, by setting the first pH of the positive electrode active material within the above range, a decrease in charging capacity is suppressed, corrosion of the positive electrode core material due to alkaline components is suppressed, and an increase in output resistance can be suppressed.

[0011] The positive electrode plate for a non-aqueous electrolyte secondary battery (hereinafter also referred to as the positive electrode plate) of this disclosure will be described with reference to Figure 1. The positive electrode plate 10 includes a positive electrode composite layer 12 and a positive electrode core material 11. The positive electrode composite layer 12 may be disposed on the surface of the positive electrode core material 11. As shown in Figure 1, the positive electrode composite layer 12 may be disposed on only one side of the positive electrode core material 11. The positive electrode composite layer 12 may be disposed on both the front and back surfaces of the positive electrode core material 11.

[0012] The positive electrode core material 11 is a conductive sheet. The positive electrode core material 11 contains Al. The positive electrode core material 11 may be pure Al foil or Al alloy foil. The positive electrode core material 11 may have a thickness of, for example, 10 to 30 μm. The thickness of the positive electrode plate 10 may be, for example, 20 to 290 μm, 50 to 250 μm, or 100 to 200 μm. The longitudinal dimension of the positive electrode plate 10 may be, for example, 0.5 to 5 m or 1 to 3 m. The positive electrode core material 11 may be exposed at one end of the positive electrode plate 10 parallel to the longitudinal direction. A positive electrode current collector, described later, can be joined to the portion where the positive electrode core material 11 is exposed.

[0013] The positive electrode composite layer 12 contains a positive electrode active material. The positive electrode active material is a lithium transition metal composite oxide containing Li and Ni. The lithium transition metal composite oxide includes at least one selected from the group consisting of, for example, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, in the composition formula "Li(NiCoMn)O2", the sum of the composition ratios in parentheses is 1. That is, "C Ni +C Co +C Mn The relationship "=1" is satisfied. For example, "C Ni The notation indicates the composition ratio of Ni. The composition ratio of each component is arbitrary as long as the sum of the composition ratios is 1. The positive electrode composite layer 12 may contain positive electrode active material particles. The positive electrode active material particles may contain any components. The positive electrode active material particles may contain the lithium transition metal composite oxide described above.

[0014] The Ni content in the lithium transition metal composite oxide is 70 mol% or more relative to the total number of moles of metal elements other than Li, and is preferably 80 mol% or more, more preferably 90 mol% or more, from the viewpoint of filling capacity. Having a Ni content within the above range in the lithium transition metal composite oxide tends to improve the battery's charging capacity.

[0015] Lithium transition metal composite oxides are, for example, given by the following formula (i): Li 1-a1 Ni x1 Me 1 1-x1 O2(i) [In formula (i), "a1" satisfies the relationship -0.3 ≤ a1 ≤ 0.3. "x1" satisfies the relationship 0.70 ≤ x1 ≤ 1.0. Me 1 " indicates at least one element selected from the group consisting of cobalt (Co), manganese (Mn), Al, titanium (Ti), zirconium (Zr), boron (B), magnesium (Mg), iron (Fe), copper (Cu), zinc (Zn), tin (Sn), sodium (Na), potassium (K), barium (Ba), strontium (Sr), calcium (Ca), tungsten (W), molybdenum (Mo), niobium (Nb), silicon (Si), vanadium (V), chromium (Cr), and germanium (Ge). The first layered metal oxide represented by may contain one or more types.

[0016] The lithium transition metal composite oxide is preferably a lithium nickel cobalt manganese composite oxide. For example, the lithium transition metal composite oxide is LiNi 0.82 Co 0.13 Mn 0.05 O2 and LiNi 0.92 Co 0.04 Mn 0.04 It may contain at least one selected from the group consisting of O2. The lithium transition metal composite oxide is substantially, for example, LiNi 0.82 Co 0.13 Mn 0.05 O2 and LiNi0.92 Co 0.04 Mn 0.04 It may consist of at least one selected from the group consisting of O2.

[0017] Lithium nickel cobalt manganese composite oxide can be produced, for example, by the following procedure. First, a lithium source such as lithium hydroxide and the nickel cobalt manganese composite hydroxide are mixed and calcined, then wet-milled using a ball mill or the like, and dried. Next, it can be obtained by washing with pure water and drying. Nickel cobalt manganese composite hydroxide may be obtained by, for example, a coprecipitation method. Nickel cobalt manganese composite hydroxide has a general formula, for example: Ni x Co y Mn z The compound may be represented by (OH)2 (where x+y+z=1). Washing with pure water can be performed, for example, by placing the lithium nickel cobalt manganese composite oxide and pure water in a container and stirring. The mass ratio (solid-liquid ratio) of lithium nickel cobalt manganese composite oxide to pure water may be, for example, 30 to 50% by mass relative to the total mass of lithium nickel cobalt manganese composite oxide and pure water. The washing time may be, for example, 1 minute to 60 minutes.

[0018] The positive electrode active material has a first pH of 11.8 to 12.5. The first pH is the pH of the filtrate obtained by adding 25g of positive electrode active material to 50g of pure water, stirring for 5 minutes, and filtering. If the first pH of the positive electrode active material is less than 11.8, the alkaline component content in the positive electrode active material decreases, and the charging capacity tends to be less likely to improve. If the first pH of the positive electrode active material exceeds 12.5, the alkaline component content in the positive electrode active material increases, corrosion of the positive electrode core material becomes more likely, and the increase in output resistance tends to be less likely to be suppressed. If the positive electrode active material contains two or more types of positive electrode active material, the first pH of the entire positive electrode active material will be within the above range. The first pH of the positive electrode active material can be controlled, for example, by adjusting the washing conditions of the positive electrode active material (e.g., solid-liquid ratio, washing time, etc.).

[0019] The positive electrode active material may include a first active material with an average particle diameter D50 of 2 to 6 μm or a second active material with an average particle diameter D50 of 10 to 20 μm. The positive electrode active material may be either the first or second active material. The first active material may have a smaller average particle diameter D50 than the second active material. In this specification, the average particle diameter D50 represents the particle diameter at which the cumulative particle volume from the small particle size side accounts for 50% of the total particle volume in a volume-based particle size distribution. The average particle diameter can be measured by laser diffraction / scattering.

[0020] The first active material may be a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles. If the first active material is a secondary particle, the number of aggregated primary particles may be 2 to 8 or 2 to 5.

[0021] When the first active material is a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles, the average particle diameter R1 of the single particle and primary particles may be, for example, 0.5 μm or more, 1.0 μm or more, 1.5 μm or more, or 1.7 μm or more, and may also be 1.7 to 6 μm, 2 to 5 μm, or 2.5 to 4.5 μm. The average particle diameter R1 is a value obtained from SEM observation images of the surface of the first active material, and is obtained by analyzing SEM images of the surfaces of multiple first active materials to determine the longest diameter of each single particle or primary particle, and then averaging this value over multiple single particles or primary particles.

[0022] The first pH of the first active material may be between 11.8 and 12.5.

[0023] The BET specific surface area of ​​the first active material is, for example, 0.2 to 1.5 m². 2 / g is acceptable.

[0024] The average particle size D50 of the second active material may be, for example, 10 to 20 μm, preferably 12 to 20 μm, more preferably 13 to 19 μm, and even more preferably 14 to 18 μm.

[0025] The second active material may be secondary particles (hereinafter also referred to as aggregated particles) formed by the aggregation of 50 or more primary particles. In the second active material, the number of aggregated primary particles may be 100 or more, 1000 or more, 10000 or more, and usually 5 × 10 6 There are fewer than 5 × 10 5 It may be one or fewer.

[0026] When the second active material is aggregated particles, the average particle diameter R2 of the primary particles constituting the aggregated particles is 2.0 μm or less, and may be, for example, 0.1 μm or more, 0.5 to 1.7 μm, or 0.7 to 1.5 μm. The average particle diameter R2 is a value obtained from scanning electron microscope (SEM) observation images of the surface of the second active material. It is obtained by analyzing SEM images of the surfaces of multiple second active materials to determine the longest diameter of each primary particle and averaging this value over multiple second active materials.

[0027] The first pH of the second active material may be between 11.8 and 12.5.

[0028] The BET specific surface area of ​​the second active material is, for example, 0.2 to 1.0 m². 2 / g is acceptable.

[0029] The positive electrode active material preferably comprises a first active material and a second active material from the viewpoint of packing properties. When the positive electrode active material comprises a first active material and a second active material, the content of the second active material may be, for example, 10 to 90% by mass or 25 to 85% by mass when the total mass of the positive electrode active material is 100% by mass, and preferably 40 to 80% by mass from the viewpoint of packing density of the positive electrode composite layer.

[0030] Generally, when the positive electrode active material contains a first active material, corrosion of the positive electrode core material tends to occur more easily than when the positive electrode active material contains a second active material. This is because positive electrode active materials with a high Ni content and a relatively small average particle size D50, such as the first active material, (1) have a relatively unstable structure and exhibit high alkali elution, (2) have a relatively small average particle size D50, resulting in a large contact area with the Al-containing positive electrode core material, and (3) have a low density, requiring higher compression during the manufacturing process of the positive electrode plate to achieve a density of the positive electrode composite layer comparable to that of a positive electrode composite layer containing a second active material. However, according to this disclosure, even when the positive electrode active material contains a first active material, corrosion of the positive electrode core material can be suppressed and the increase in output resistance can be easily controlled.

[0031] The heterocyclic compound used in this disclosure is defined by formula (1): [ka] [In formula (1), R a ~R c Each of these is independently a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. X a This is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents.

[0032] Or equation (2): [ka] [In formula (2), R a and R bEach of these is independently a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. R a and R b These may form a ring with 4 to 12 carbon atoms bonded to each other, which may have substituents. Z is N or CR d And, R d This is a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. X a This is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. It can be represented by one of the following.

[0033] The heterocyclic compound represented by formula (1) may also be a structural isomer. Specifically, structural isomers of the heterocyclic compound represented by formula (1) include, for example, the following formulas (1-A) to (1-G): [ka] [In the formula, R a ~R c , X a This is the same as above. Examples of heterocyclic compounds represented by the formulas are shown below.

[0034] X a However, in the case of a hydrogen atom, the tautomer is preferred among the above structural isomers. a When the atom is a hydrogen atom, its tautomer is also called a proton tautomer.

[0035] R a ~R c The C1-C6 alkyl group in "alkyl group having substituents which may have substituents" can be linear, branched, or cyclic. Specific examples include linear or branched C1-C6 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, and n-hexyl groups; and cyclic alkyl groups having C3-C6 such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0036] R a ~R c Examples of C2-C6 alkenyl groups in the "C2-C6 alkenyl group which may have substituents" include ethenyl group, n-1-propenyl group, n-2-propenyl group, 1-methylethenyl group, n-1-butenyl group, n-2-butenyl group, n-3-butenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, 1-methyl-1-propenyl group, 1-methyl-2-propenyl group, and n-1-pentenyl group.

[0037] R a ~R c Examples of aryl groups having 6 to 12 carbon atoms in the "aryl group having 6 to 12 carbon atoms that may have substituents" include phenyl group, tolyl group, 1-naphthyl group, 2-naphthyl group, etc.

[0038] R a ~R c It may have substituents. Examples of substituents include carboxyl groups, hydroxyl groups, aldehyde groups, ester groups, ketone groups, amino groups, phenyl groups, halogen atoms, alkoxysilyl groups, epoxy groups, carboxylic acid chloride groups, thiol groups, etc. Examples of alkoxysilyl groups include trimethoxysilyl groups, dimethoxymethylsilyl groups, methoxydimethylsilyl groups, triethoxysilyl groups, diethoxymethylsilyl groups, ethoxydimethylsilyl groups, etc. In this disclosure, carboxyl groups are preferred. a ~Rc If the molecule has substituents, the number is preferably 1 to 6, and more preferably 1 to 3.

[0039] R a ~R c Preferably, the R in formula (2) above is a hydrogen atom, a carboxyl group, an alkyl group having 1 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. a and R b Preferably, the rings, which may have substituents, are formed by bonding with each other and have 4 to 12 carbon atoms.

[0040] Also, R a ~R c More preferably, the R in formula (2) above is a hydrogen atom, a carboxyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. a and R b More preferably, the rings having 4 to 12 carbon atoms, which may have substituents, are formed by bonding with each other.

[0041] Furthermore, R a ~R c More preferably, R in formula (2) above is a hydrogen atom, a carboxyl group, an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 10 carbon atoms. a and R b A more preferable form is a ring having 6 to 10 carbon atoms, which may have substituents, formed by bonding with each other.

[0042] Furthermore, R a ~R c More preferably, R is a hydrogen atom, a carboxyl group, a methyl group, or a phenyl group, and also R of formula (2) above. a and R b More preferably, these are benzene rings, which may have substituents, that are bonded together to one another.

[0043] Z is N or CR d And R dThis is a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents.

[0044] For Z, N is preferable.

[0045] X a The C1-C6 alkyl group in "alkyl group having substituents which may have substituents" can be linear, branched, or cyclic. Specific examples include linear or branched C1-C6 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, and n-hexyl groups; and cyclic alkyl groups having C3-C6 such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0046] X a Examples of aryl groups having 6 to 12 carbon atoms in the "aryl group having 6 to 12 carbon atoms that may have substituents" include phenyl group, tolyl group, 1-naphthyl group, 2-naphthyl group, etc.

[0047] X a The group may have substituents. Examples of substituents include carboxyl groups, hydroxyl groups, aldehyde groups, ester groups, ketone groups, amino groups, phenyl groups, halogen atoms, alkoxysilyl groups, epoxy groups, carboxylic acid chloride groups, and thiol groups. Examples of the above alkoxysilyl groups include trimethoxysilyl groups, dimethoxymethylsilyl groups, methoxydimethylsilyl groups, triethoxysilyl groups, diethoxymethylsilyl groups, and ethoxydimethylsilyl groups. In the present invention, carboxyl groups and alkoxysilyl groups are preferred, and carboxyl groups and trimethoxysilyl groups are more preferred.

[0048] X aPreferred members include hydrogen atoms, C1-C6 alkyl groups which may have substituents, and C6-C12 aryl groups which may have substituents.

[0049] Also, X a More preferably, hydrogen atoms, C1-C4 alkyl groups, and C6-C10 aryl groups are used.

[0050] Furthermore, X a Hydrogen atoms, C1-C3 alkyl groups, and C6-C8 aryl groups are more preferred.

[0051] Specific examples of heterocyclic compounds represented by formula (1) include the heterocyclic compounds represented by the following formulas (1-1) to (1-14).

[0052] [ka]

[0053] Specific examples of heterocyclic compounds represented by formula (2) include the heterocyclic compounds represented by the following formulas (2-1) to (2-13). [ka] *The structure of the heterocyclic compound represented by formula (2-6) is the structure of the compound listed in Shin-Etsu Chemical Co., Ltd.'s catalog as X-12-1214A.

[0054] The heterocyclic compound represented by formula (1) or formula (2) can be a commercially available product, for example. Examples of commercially available heterocyclic compounds represented by formula (1) or formula (2) include SA-426H (manufactured by Nissan Chemical Corporation) and X-12-1214A (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0055] The content of the heterocyclic compound in the positive electrode composite layer 12 is 0.01 to 0.5% by mass relative to the mass of the positive electrode composite layer 12. When the content of the heterocyclic compound in the positive electrode composite layer is within the above range, the positive electrode active material is uniformly covered with the heterocyclic compound, making it easier to suppress alkali elution from the positive electrode active material and making it less likely for the charging capacity to decrease. If the content of the heterocyclic compound in the positive electrode composite layer is less than 0.01% by mass, corrosion of the positive electrode core material cannot be suppressed, and the increase in output resistance tends to be less suppressed. If the content of the heterocyclic compound in the positive electrode composite layer is greater than 0.5% by mass, the charging capacity tends to be less likely to improve. Furthermore, when using additives other than the above heterocyclic compound, it is necessary to add a larger amount than the content of the above heterocyclic compound in order to obtain the effect of suppressing alkali elution and the resulting corrosion of the positive electrode core material. As a result, the amount added increases, which negatively affects the output characteristics, and the output suppression effect is not obtained. The content of the heterocyclic compound in the positive electrode composite layer 12 is preferably 0.0125 to 0.3% by mass, and more preferably 0.025 to 0.2% by mass, relative to the mass of the positive electrode composite layer 12, from the viewpoint of output resistance and charging capacity.

[0056] The positive electrode composite layer 12 may contain, in addition to the positive electrode active material and heterocyclic compound, a binder and a conductive material. Examples of binders include known materials such as fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE); and cellulosic resins such as carboxymethylcellulose (CMC). Examples of conductive materials include carbon materials. Examples of carbon materials include one or more selected from the group consisting of fibrous carbon, carbon black, coke, and activated carbon. Examples of carbon black include acetylene black (AB).

[0057] The thickness of the positive electrode composite material layer 12 indicates the total thickness of the positive electrode composite material layers 12 included in the laminate 40. For example, when the positive electrode composite material layers 12 are formed on both sides of the positive electrode plate 10, the thickness of the positive electrode composite material layer 12 indicates the total thickness of the positive electrode composite material layers 12 on both sides (two sides). The positive electrode composite material layer 12 may have a thickness of, for example, 10 to 260 μm, or may have a thickness of 20 to 60 μm, or may have a thickness of 30 to 50 μm. Note that the thickness of the positive electrode composite material layer 12 on one side (one side) may be, for example, 10 to 30 μm, or may be 15 to 25 μm.

[0058] The density of the positive electrode composite material layer 12 may be, for example, 3.0 to 4.0 g / cm 3 and preferably is 3.2 to 3.6 g / cm 3 is.

[0059] <Method for manufacturing a positive electrode plate> The positive electrode plate 10 can be manufactured, for example, by applying a positive electrode active material slurry on the positive electrode core material 11, drying it, and compressing it to form the positive electrode composite material layer 12. As shown in FIG. 2, the method for manufacturing the positive electrode plate 10 includes a slurry preparation step (S1) of mixing a positive electrode active material and a heterocyclic compound to prepare a positive electrode composite material slurry. The method for manufacturing the positive electrode plate may further include a coating step (S2), a drying step (S3), and a compression step (S4).

[0060] In the slurry preparation step (S1), a cathode composite slurry containing a cathode active material and a heterocyclic compound is prepared. The cathode composite slurry is prepared by dispersing the cathode active material and the heterocyclic compound in a dispersion medium. The dispersion medium may be, for example, an organic solvent. The organic solvent may include at least one selected from the group consisting of, for example, N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), methyl ethyl ketone (MEK), and dimethyl sulfoxide (DMSO). The amount of organic solvent used is arbitrary. The cathode composite slurry may have any solid content concentration (mass fraction of solids). The cathode composite may have a solid content concentration of, for example, 40-80%. Mixing can be performed using any stirring device, mixing device, or dispersion device. In the slurry preparation step (S1), the positive electrode active material and the heterocyclic compound can be mixed such that the content of the heterocyclic compound relative to the solid content in the positive electrode mixture slurry is 0.01 to 0.5% by mass.

[0061] The slurry preparation step (S1) may include a first step of mixing a positive electrode active material, a binder, and a dispersion medium to obtain a first mixture, and a second step of mixing the first mixture with a heterocyclic compound to obtain a second mixture. When the slurry preparation step (S1) includes both the first and second steps, by adding the heterocyclic compound after allowing the dispersion medium to permeate the entire positive electrode active material, the heterocyclic compound can be adsorbed onto the positive electrode active material, making it less likely for the dispersion of the heterocyclic compound to be uneven.

[0062] In the first step, for example, the positive electrode active material, the binder, and the dispersion medium can be kneaded at a rotational speed of 10 to 20 rpm so that the solid content is 85 to 95%.

[0063] In the second step, the heterocyclic compound can be added together with the dispersion medium.

[0064] The second mixture obtained in the second step can be used as a positive electrode mixture slurry. Furthermore, if the positive electrode mixture layer contains a conductive material, the conductive material can be added to the first or second mixture to prepare a positive electrode mixture slurry. The slurry preparation step (S1) may further include a conductive material addition step in which the conductive material is added to the first or second mixture. The conductive material addition step may be performed after the first step and before the second step, i.e., the conductive material may be added to the first mixture after the first step and before the second step. Alternatively, the conductive material addition step may be performed simultaneously with the second step, i.e., the conductive material may be added together with the heterocyclic compound in the second step. Alternatively, the conductive material addition step may be performed after the second step, i.e., the conductive material may be added to the second mixture. The conductive material can be added together with the dispersion medium.

[0065] In the conductive material addition process, for example, the first mixture or the second mixture and the conductive material can be kneaded at a rotational speed of 20 to 40 rpm so that the solid content is 70 to 83%.

[0066] In the coating process (S2), a coating film is formed by coating the surface of the substrate with a positive electrode mixture slurry. Any coating apparatus can be used for coating.

[0067] In the drying process (S3), the coating film is heated and dried, for example, using a hot air dryer, to form a dried coating film. The compression process (S4) may include compressing the dried coating film using any compression device to form the positive electrode composite layer 12. The dried coating film is compressed, the positive electrode composite layer 12 is formed, and the positive electrode plate 10 is completed. The positive electrode plate 10 can be cut to a predetermined planar size according to the specifications of the battery. The positive electrode plate 10 may be cut to have, for example, a strip-shaped planar shape. The positive electrode plate 10 may be cut to have, for example, a rectangular planar shape.

[0068] <Nonaqueous electrolyte secondary battery> The non-aqueous electrolyte secondary battery (hereinafter also referred to as "battery") of this disclosure may be a lithium-ion battery. Figure 3 is a schematic diagram showing an example of a battery in this embodiment. The battery 100 shown in Figure 3 may be a lithium-ion battery used, for example, as the main power source or power assist power source for an electric vehicle. Multiple batteries 100 may be connected to form a battery module or battery pack. The battery 100 may have a rated capacity of, for example, 1 to 200 Ah.

[0069] The battery 100 includes an outer casing 90. The outer casing 90 may include, for example, a sealing plate 91 and an outer can 92. The sealing plate 91 closes the opening of the outer can 92. The sealing plate 91 and the outer can 92 may be joined together, for example, by laser processing. The outer casing 90 can have any form. The outer casing 90 may be, for example, a pouch type. That is, the outer casing 90 may be a pouch made of Al laminate film.

[0070] The outer casing 90 houses the electrode body 50 and a non-aqueous electrolyte (not shown). The sealing plate 91 is provided with a positive electrode terminal 81 and a negative electrode terminal 82. The sealing plate 91 may also be provided with an inlet (not shown), a gas discharge valve (not shown), etc. The electrolyte can be injected into the interior of the outer casing 90 from the inlet. The inlet can be closed, for example, by a sealing plug.

[0071] The positive electrode current collector 71 connects the positive electrode terminal 81 to the electrode body 50. The positive electrode current collector 71 may be made of, for example, an aluminum plate. The negative electrode current collector 72 connects the negative electrode terminal 82 to the electrode body 50. The negative electrode current collector 72 may be made of, for example, a copper (Cu) plate.

[0072] Figure 4 is a schematic diagram showing an example of an electrode body in this embodiment. The electrode body 50 in Figure 2 is a wound-type electrode body having a winding axis R parallel to the W-axis direction. The electrode body 50 includes a positive electrode plate 10, a separator 30, and a negative electrode plate 20. That is, the battery 100 includes a positive electrode plate 10. The positive electrode plate 10 includes a positive electrode composite layer 12 and a positive electrode core material 11.

[0073] The negative electrode plate 20 typically comprises a negative electrode core material 21 and a negative electrode composite material layer 22 formed on one or both sides of the negative electrode core material 21. The negative electrode core material 21 is a metal foil made of copper material such as copper and copper alloys. The negative electrode composite material layer 22 contains a negative electrode active material and may further contain a conductive material and a binder.

[0074] Examples of negative electrode active materials include known materials such as carbon-based active material particles such as graphite, and metallic active material particles containing elements selected from the group consisting of Si, Sn, Sb, Bi, Ti, and Ge. Examples of conductive materials include those mentioned above. Examples of binders include cellulosic resins such as CMC, methylcellulose (MC), and hydroxypropylcellulose; polyacrylic acid; and styrene-butadiene rubber (SBR). CMC can also be used as a thickener.

[0075] The separator 30 has a single-layer or multi-layer substrate, and may have a functional layer on at least one side of the substrate. The substrate may be a porous sheet such as a film or nonwoven fabric made of polyethylene and polyolefins such as polypropylene, polyester, cellulose, or polyamide. Examples of the functional layer include an adhesive layer and / or a heat-resistant layer. The adhesive layer can be formed, for example, by an adhesive. The heat-resistant layer may include, for example, a filler and a binder.

[0076] The electrolyte is preferably an electrolyte contained in a non-aqueous solvent such as an organic solvent. Examples of electrolytes include one or more from LiPF6, LiBF4, LiClO4, LiFSO3, and LiB(C2O4)2. Examples of non-aqueous solvents include one or more from ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate (BC), and diethyl carbonate (DEC). The electrolyte may further contain additives such as vinylene carbonate (VC), vinylethylene carbonate (VEC), and fluoroethylene carbonate.

[0077] The present invention will be described in more detail below with reference to examples. [Examples]

[0078] [Cathode active material] Lithium transition metal composite oxides having the molar ratios of Ni, Co, and Mn (hereinafter also referred to as the NCM ratio), average particle size D50, BET specific surface area, and first pH shown in Table 1 were prepared. The lithium transition metal composite oxides and pure water were placed in a container at the solid-liquid ratio shown in Table 1, stirred and washed for 10 minutes, filtered, and dried at 120°C for 5 hours to obtain positive electrode active materials A to H. The solid-liquid ratio is the ratio (mass%) of the mass of the lithium transition metal composite oxide to the total mass of the lithium transition metal composite oxide and pure water. In positive electrode active materials A to H, the molar ratio of Li to other metal elements (Me) (Li:Me) was 1.05:1. Positive electrode active materials A to D, G, and H were single particles or secondary particles (first active material) formed by the aggregation of 2 to 5 primary particles. Positive electrode active materials E and F were secondary particles (second active material) formed by the aggregation of 50 or more primary particles. The BET specific surface area was measured using a specific surface area measuring device. The first pH was determined by adding 25g of the washed positive electrode active material to 50g of pure water, stirring for 5 minutes, and then filtering the resulting filtrate and measuring its pH.

[0079] [Table 1]

[0080] <Test Example 1> A positive electrode slurry was prepared by mixing positive electrode active material A, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of positive electrode active material A:AB:PVDF = 97.5:1.5:1.0, and adding an appropriate amount of N-methyl-2-pyrrolidone (NMP) to the resulting mixture. The positive electrode slurry was applied to both sides of an aluminum foil positive electrode core and dried to form a positive electrode slurry layer. After roll pressing the positive electrode slurry layer with a rolling mill, it was cut to the specified dimensions to produce the positive electrode plate of Test Example 1.

[0081] <Test Example 2> A cathode composite slurry was prepared by mixing cathode active material A, N-methyl-2-pyrrolidone (NMP), and polyvinylidene fluoride (PVDF) as a binder. Acetylene black (AB) as a conductive material and an additive containing a heterocyclic compound were added to this mixed solution in a mass ratio of cathode active material A:AB:PVDF:heterocyclic compound = 97.495:1.5:1.0:0.005. The additive containing the heterocyclic compound was an N-methylpyrrolidone solution ("SA-426H" manufactured by Nissan Chemical Corporation) containing 35% by mass of the heterocyclic compound represented by formula (1) or formula (2). The cathode composite slurry was applied to both sides of an aluminum foil cathode core and dried to form a cathode composite layer. After roll-pressing the cathode composite layer with a rolling mill, it was cut to the specified dimensions to produce the cathode plate of Test Example 2.

[0082] <Test Examples 3-10> The positive electrode plate was fabricated in the same manner as in Test Example 2, except that the amount of additives used was as shown in Table 2.

[0083] <Test Examples 11-18> The positive electrode plate was fabricated in the same manner as in Test Example 2, except that the type of positive electrode active material and the amount of additives were as shown in Table 2.

[0084] [Fabrication of lithium-ion secondary batteries for evaluation] A negative electrode slurry was prepared by mixing graphite (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethylcellulose (CMC) as a thickener in ion-exchanged water in a mass ratio of C:SBR:CMC = 98:1:1. This negative electrode slurry was applied to copper foil and dried to form a negative electrode layer. The negative electrode layer was roll-pressed with a rolling mill to a predetermined density, and then cut to predetermined dimensions to produce a negative electrode plate.

[0085] A porous polyolefin sheet was prepared as a separator. The positive electrode plate and negative electrode plate of each test example were stacked with the separator in between to create a laminated electrode body.

[0086] Electrode terminals were attached to a stacked electrode body, which was then inserted into a battery case made of aluminum laminate sheet, and a non-aqueous electrolyte was injected. The non-aqueous electrolyte used was a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of EC:EMC:DMC = 30:70, to which LiPF6 as a supporting salt was dissolved at a concentration of 1 mol / L, and vinylene carbonate was added to a concentration of 0.3 mass%. Subsequently, a lithium-ion secondary battery for evaluation was obtained by sealing the battery case.

[0087] [Charging capacity evaluation] The evaluation lithium-ion secondary battery measured a current density of 0.2 mA / cm² at a temperature of 25°C. 2 Then, constant current charging is performed until the potential reaches 4.3V vs. Li / Li+, and further, at a potential of 4.3V vs. Li / Li+, a current of 0.04mA / cm² is applied. 2 Constant voltage charging was performed until the current density reached a certain level, and the charging capacity per unit mass of the positive electrode active material [mAh / g] was measured. The results are shown in Table 2.

[0088] [Evaluation of output resistance] The output resistance of the evaluation lithium-ion secondary battery was measured at 25°C when the state of charge (SOC) reached 50% (charge capacity was 50% of the initial discharge capacity). The results are shown in Table 2. Output resistance was judged as follows: "×" for an output resistance of 0.090Ω or higher, "△" for an output resistance between 0.080Ω and less than 0.090Ω, and "○" for an output resistance of less than 0.080Ω.

[0089] [Table 2]

[0090] Test Examples 3-9, 14, 16, and 17, which contained a positive electrode active material with a predetermined amount of heterocyclic compound and a predetermined first pH, showed good output resistance and suppressed the decrease in charging capacity. In contrast, Test Example 1, which did not contain a heterocyclic compound, showed corrosion of the positive electrode core material (Al foil) and an increase in output resistance. Test Example 2 also showed an increase in output resistance due to a low content of the heterocyclic compound. On the other hand, Test Example 10 showed an increase in output resistance and a decrease in charging capacity due to a high content of the heterocyclic compound.

[0091] In Test Example 11, although the heterocyclic compound was present in the specified amount, the first pH of the positive electrode active material was too high, causing corrosion of the positive electrode core material (Al foil) and an increase in output resistance. In Test Example 12, the water washing conditions were excessive, resulting in a first pH that was too low. While this prevented corrosion of the positive electrode core material and suppressed the increase in output resistance, the low alkali content led to a decrease in charging capacity.

[0092] In Test Example 13, because it did not contain a heterocyclic compound, the positive electrode core material (Al foil) corroded, and the output resistance increased. In contrast, in Test Example 14, which contained the same positive electrode active material as in Test Example 13, the output resistance improved and the decrease in charging capacity was suppressed by including a heterocyclic compound in a predetermined amount.

[0093] In Test Example 15, although the first pH was within the specified range, the absence of a heterocyclic compound resulted in corrosion of the positive electrode core material (Al foil) and an increase in output resistance. Furthermore, in Test Example 16, which contained the same positive electrode active material as Test Example 15, the inclusion of a heterocyclic compound in a specified amount resulted in improved output resistance and suppressed a decrease in charging capacity.

[0094] In Test Example 17, due to the low Ni content, corrosion of the positive electrode core material (Al foil) was less likely to occur, and although the main resistance did not increase, the charging capacity decreased. In Test Example 18, although the heterocyclic compound was contained in the specified amount, the high first pH caused corrosion of the positive electrode core material (Al foil), resulting in an increase in output resistance. [Explanation of Symbols]

[0095] 10 Positive electrode plate, 11 Positive electrode core material, 12 Positive electrode composite layer, 20 Negative electrode plate, 21 Negative electrode core material, 22 Negative electrode composite layer, 30 Separator, 40 Laminate, 50 Electrode body, 71 Positive electrode current collector, 72 Negative electrode current collector, 81 Positive electrode terminal, 82 Negative electrode terminal, 90 Outer casing, 91 Sealing plate, 92 Outer casing, 100 Battery.

Claims

1. A positive electrode plate for a non-aqueous electrolyte secondary battery, comprising a positive electrode composite layer and a positive electrode core material, The positive electrode core material contains aluminum, The positive electrode composite layer comprises a positive electrode active material and the following formula (1): 【Chemistry 1】 [In formula (1), R ａ ~R ｃ Each of these is independently a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. X ａ This is a hydrogen atom, a C1-C6 alkyl group which may have substituents, or a C6-C12 aryl group which may have substituents. Or the following formula (2): 【Chemistry 2】 [In formula (2), R ａ and R ｂ Each of these is independently a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group having 1 to 6 carbon atoms which may have substituents, an alkenyl group having 2 to 6 carbon atoms which may have substituents, or an aryl group having 6 to 12 carbon atoms which may have substituents. R ａ and R ｂ These may form a ring with 4 to 12 carbon atoms bonded to each other, which may have substituents. Z is N or C-R ｄ And, R ｄ is a hydrogen atom, a halogen atom, a carboxy group, a hydroxy group, a thiol group, an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, or an optionally substituted aryl group having 6 to 12 carbon atoms, X ａ This is a hydrogen atom, a C1-C6 alkyl group which may have substituents, or a C6-C12 aryl group which may have substituents. It includes at least one heterocyclic compound represented by, The positive electrode active material is a lithium transition metal composite oxide containing lithium and nickel. The nickel content in the aforementioned lithium transition metal composite oxide is 70 mol% or more relative to the total number of moles of metal elements other than lithium. The positive electrode active material is obtained by adding 25 g of the positive electrode active material to 50 g of pure water, stirring for 5 minutes, and filtering, and the pH of the filtrate obtained is 11.8 or higher and 12.5 or lower. A positive electrode plate for a non-aqueous electrolyte secondary battery, wherein the content of the heterocyclic compound in the positive electrode composite layer is 0.01 to 0.5% by mass relative to the mass of the positive electrode composite layer.

2. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material comprises a first active material having an average particle diameter D50 of 2 to 6 μm.

3. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 2, wherein the first active material is a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles.

4. The BET specific surface area of ​​the first active material is 0.2 to 1.5 m². ２ A positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 2, wherein the value is / g.

5. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material includes a second active material having an average particle diameter D50 of 10 to 20 μm.

6. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 5, wherein the second active material is a secondary particle formed by the aggregation of 50 or more primary particles.

7. The BET specific surface area of ​​the second active material is 0.2 to 1.0 m². ２ A positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 5, wherein the value is / g.

8. A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery, comprising a slurry preparation step of mixing the positive electrode active material and the heterocyclic compound to obtain a positive electrode composite slurry.

9. The slurry preparation step is as follows: A first step involves mixing the positive electrode active material, a binder, and a dispersion medium to obtain a first mixture. A second step involves mixing the first mixture with the heterocyclic compound to obtain a second mixture. A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 8, including the method described in claim 8.

10. A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 8, comprising mixing the positive electrode active material and the heterocyclic compound such that the content of the heterocyclic compound relative to the solid content in the positive electrode mixture slurry is 0.01 to 0.5% by mass.

11. A non-aqueous electrolyte secondary battery comprising a positive electrode plate for a non-aqueous electrolyte secondary battery as described in claim 1.

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