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

Abstract

The present disclosure relates to a positive electrode plate for a non-aqueous electrolyte secondary battery comprising a positive electrode composite material layer and a positive electrode core material. The positive electrode core material contains aluminum, the positive electrode composite material layer contains a positive electrode active material and at least one of heterocyclic compounds represented by formula (1) or formula (2), and the positive electrode active material is a lithium transition metal composite oxide containing lithium and nickel. The content of nickel in the lithium transition metal composite oxide is 70 mol% or more with respect to the total number of moles of metal elements other than lithium, the BET specific surface area of the positive electrode active material is 0.2-1.1 m2 / g, and the content of the heterocyclic compound in the positive electrode mixture layer is 0.01-0.5 mass% with respect to the mass of the positive electrode mixture layer.

Description

Technical Field

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

[0002] Japanese Patent Application Publication No. 2011-113825 discloses a positive electrode material for lithium-ion secondary batteries containing a positive electrode active material with a high nickel content. Summary of the Invention

[0003] When using positive electrode plates containing positive electrode active materials with high nickel content in lithium-ion secondary batteries, high capacity becomes possible, but there is a tendency for increased output resistance.

[0004] The purpose of this disclosure is to provide a positive plate capable of suppressing the rise in output resistance and suppressing the decrease in charging capacity, a method for manufacturing the same, and a non-aqueous electrolyte secondary battery comprising the positive plate.

[0005] [1] A positive electrode plate for a non-aqueous electrolyte secondary battery, comprising a positive electrode composite material layer and a positive electrode core material,

[0006] The aforementioned positive electrode core material contains aluminum.

[0007] The aforementioned positive electrode composite material layer comprises a positive electrode active material and at least one heterocyclic compound represented by formula (1) or formula (2) below.

[0008]

[0009] In equation (1),

[0010] R a ~R c Each group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0011] X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents.

[0012]

[0013] In equation (2),

[0014] R a and R bEach group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0015] R a and R b They can bond with each other to form rings with 4 to 12 carbon atoms that can have substituents.

[0016] Z is N or C-R d ,

[0017] R d It can be a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0018] X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents.

[0019] The aforementioned positive electrode active material is a lithium transition metal composite oxide containing lithium and nickel.

[0020] The nickel content in the aforementioned lithium transition metal composite oxide is more than 70 mol% relative to the total molar percentage of metals other than lithium.

[0021] The BET specific surface area of ​​the above-mentioned positive electrode active material is 0.2–1.1 m². 2 / g,

[0022] The content of the heterocyclic compound in the above-mentioned positive electrode composite material layer is 0.01 to 0.5% of the mass of the above-mentioned positive electrode composite material layer.

[0023] [2] According to the positive electrode plate for a non-aqueous electrolyte secondary battery described in [1], wherein the positive electrode active material comprises a first active material with an average particle size D50 of 2 to 6 μm.

[0024] [3] According to the positive electrode plate for non-aqueous electrolyte secondary battery described in [2], the first active material is a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles.

[0025] [4] The positive electrode plate for a non-aqueous electrolyte secondary battery according to [2] or [3], wherein the BET specific surface area of ​​the first active material is 0.2 to 1.5 m². 2 / g.

[0026] [5] A positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of [1] to [4], wherein the positive electrode active material comprises a second active material with an average particle size D50 of 10 to 20 μm.

[0027] [6] According to the positive electrode plate for a non-aqueous electrolyte secondary battery described in [5], the second active material is a secondary particle formed by the aggregation of more than 50 primary particles.

[0028] [7] The positive electrode plate for a non-aqueous electrolyte secondary battery according to [5] or [6], wherein the BET specific surface area of ​​the second active material is 0.2 to 1.0 m². 2 / g.

[0029] [8] A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery, which is the method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery as described in any one of [1] to [7].

[0030] The process includes a slurry preparation step, in which the above-mentioned positive electrode active material and the above-mentioned heterocyclic compound are mixed to obtain a positive electrode composite material slurry.

[0031] [9] According to the manufacturing method of the positive electrode plate for a non-aqueous electrolyte secondary battery described in [8], the above-mentioned slurry preparation step includes:

[0032] The first step involves mixing the aforementioned positive electrode active material, binder, and dispersion medium to obtain a first mixture; and

[0033] In the second step, the first mixture and the heterocyclic compound are mixed to obtain a second mixture.

[0034]

[10] According to the manufacturing method of the positive electrode plate for a non-aqueous electrolyte secondary battery described in [8], 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 composite slurry.

[0035]

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

[0036] The above-mentioned contents and other objects, features, aspects and advantages of the present invention may be appreciated from the following detailed description of the invention, which is understood in conjunction with the accompanying drawings. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating an example of the layered structure of a positive electrode plate.

[0038] Figure 2This is a simplified flowchart of the manufacturing method of the positive electrode plate in this embodiment.

[0039] Figure 3 This is a schematic diagram illustrating an example of the battery configuration in this embodiment.

[0040] Figure 4 This is a schematic diagram illustrating an example of the configuration of the electrode body in this embodiment. Detailed Implementation

[0041] Positive electrode plates for non-aqueous electrolyte secondary batteries

[0042] The positive electrode plate (hereinafter also referred to as the positive electrode plate) for a non-aqueous electrolyte secondary battery disclosed herein comprises a positive electrode composite material layer and a positive electrode core material. The positive electrode core material comprises aluminum (Al). The positive electrode composite material layer comprises a positive electrode active material and at least one of a heterocyclic compound (hereinafter also referred to as a heterocyclic compound) represented by formula (1) or formula (2). The positive electrode active material is a lithium transition metal composite oxide comprising lithium (Li) and nickel (Ni). The Ni content (hereinafter also referred to as Ni content) in the lithium transition metal composite oxide is 70 mol% or more relative to the total molar percentage of metal elements other than Li. The BET specific surface area of ​​the positive electrode active material is 0.2 to 1.1 m². 2 / g, the content of heterocyclic compounds in the cathode composite material layer is 0.01 to 0.5% of the mass of the cathode composite material layer.

[0043] According to this disclosure, it is possible to suppress the increase in output resistance of non-aqueous electrolyte secondary batteries (hereinafter also referred to as batteries) and suppress the decrease in charging capacity. The inventors have discovered that the increase in output resistance when using a positive electrode plate containing a positive electrode active material with a high Ni content is due to Al corrosion at the interface between the positive electrode active material and the Al-containing positive electrode core material. This is because positive electrode active materials with a high Ni content have a high alkali content and tend to release alkali components easily from the positive electrode active material. When the positive electrode active material comes into contact with the Al-containing positive electrode core material, the alkali components released at this interface corrode the Al-containing positive electrode core material. Furthermore, it has been found that when the BET specific surface area of ​​the positive electrode active material is high, the contact area between the positive electrode active material and the positive electrode core material increases, resulting in easier corrosion of the positive electrode core material. In the positive electrode plate of this disclosure, by using a positive electrode active material with a high Ni content, the decrease in charging capacity can be suppressed. Furthermore, since heterocyclic compounds are 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 can be suppressed. In addition, by making the BET specific surface area of ​​the positive electrode active material within the aforementioned range, even when using a positive electrode active material with a high Ni content, corrosion of the positive electrode core material can be suppressed, and the increase in output resistance can be suppressed.

[0044] Reference Figure 1 The positive electrode plate (hereinafter also referred to as the positive electrode plate) for a non-aqueous electrolyte secondary battery disclosed herein will be described. The positive electrode plate 10 includes a positive electrode composite material layer 12 and a positive electrode core material 11. The positive electrode composite material layer 12 may be disposed on the surface of the positive electrode core material 11. For example... Figure 1 As shown, the positive electrode composite material layer 12 can be disposed on only one side of the positive electrode core material 11. The positive electrode composite material layer 12 can also be disposed on both the front and back sides of the positive electrode core material 11.

[0045] The positive electrode core material 11 is a conductive sheet. The positive electrode core material 11 contains Al. The positive electrode core material 11 can be pure Al foil or Al alloy foil. The positive electrode core material 11 can, for example, have a thickness of 10–30 μm. The thickness of the positive electrode plate 10 can, for example, be 20–290 μm, 50–250 μm, or 100–200 μm. The dimension of the long side of the positive electrode plate 10 can, for example, be 0.5–5 m or 1–3 m. The positive electrode core material 11 may be exposed at one end of the positive electrode plate 10 parallel to the long side. The exposed portion of the positive electrode core material 11 can be joined with the positive electrode current collector, described later.

[0046] 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, for example, contains at least one selected from 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 within parentheses is 1. That is, it satisfies "C Ni +C Co +C Mn The relationship is "=1". For example, "C" Ni "" indicates the composition ratio of Ni. As long as the sum of the composition ratios is 1, the composition ratio of each component is arbitrary. The positive electrode composite material 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 above-mentioned lithium transition metal composite oxide.

[0047] The Ni content in the lithium transition metal composite oxide is 70 mol% or more relative to the total moles of metal elements other than Li, and from the viewpoint of fill capacity, it is preferably 80 mol% or more, and more preferably 90 mol% or more. With the Ni content in the lithium transition metal composite oxide within the above range, there is a tendency to easily increase the battery's charge capacity.

[0048] The lithium transition metal composite oxide may, for example, contain one or more first layered metal oxides represented by formula (i) below.

[0049] Li 1-a1 Ni x1 Me 1 1-x1 O2 (i)

[0050] [In formula (i),]

[0051] “a1” satisfies the relationship -0.3≤a1≤0.3.

[0052] “x1” satisfies the relationship 0.70≤x1≤1.0.

[0053] “Me 1 "Indicates at least one selected from 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).

[0054] The lithium transition metal composite oxide is preferably a lithium-nickel-cobalt-manganese composite oxide. The lithium transition metal composite oxide may contain, for example, LiNi. 0.82 Co 0.13 Mn 0.05 O2 and LiNi 0.92 Co 0.04 Mn 0.04 At least one of O2. Lithium transition metal composite oxides can be substantially composed of, for example, LiNi. 0.82 Co 0.13 Mn 0.05 O2 and LiNi 0.92 Co 0.04 Mn 0.04 At least one of the components of O2.

[0055] Lithium-nickel-cobalt-manganese composite oxides can be obtained, for example, by mixing a lithium source such as lithium hydroxide with a nickel-cobalt-manganese composite hydroxide and calcining it, followed by wet grinding and drying using a ball mill or similar method. Nickel-cobalt-manganese composite hydroxides can be obtained, for example, through co-precipitation methods. Nickel-cobalt-manganese composite hydroxides can, for example, have the general formula: Ni x Co y Mn z The compound represented by (OH)2 (where x + y + z = 1).

[0056] The BET specific surface area of ​​the positive electrode active material is 0.2–1.1 m². 2 / g. If the BET specific surface area of ​​the positive electrode active material is less than 0.2m². 2If the BET specific surface area of ​​the positive electrode active material exceeds 1.1 m² / g, then the charging capacity tends to be difficult to improve. 2 If the surface area of ​​the positive electrode active material is increased by a certain percentage (g), the contact area between the positive electrode active material and the positive electrode core material becomes larger, which tends to easily cause corrosion of the positive electrode core material and make it difficult to suppress the increase in output resistance. When the positive electrode active material contains two or more positive electrode active materials, the overall BET specific surface area of ​​the positive electrode active material is within the range mentioned above. The BET specific surface area represents the specific surface area calculated by the BET multi-point method in the adsorption isotherm determined by the gas adsorption method. The BET specific surface area can be measured using a specific surface area measuring device. The BET specific surface area can be controlled, for example, by adjusting the ratio of raw materials used to manufacture the positive electrode active material and firing parameters (such as firing temperature, firing time, firing atmosphere, etc.).

[0057] The positive electrode active material may comprise a first active material with an average particle size D50 of 2–6 μm or a second active material with an average particle size D50 of 10–20 μm. The positive electrode active material may be either the first or the second active material. The first active material may have a smaller average particle size D50 than the second active material. In this specification, the average particle size D50 represents the particle size in a volume-based particle size distribution where the cumulative particle volume from the smallest particle size side is 50% of the total particle volume. The average particle size can be determined by laser diffraction and scattering.

[0058] The first active substance can be a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles. When the first active substance is a secondary particle, the number of primary particles can be 2 to 8 or 2 to 5.

[0059] 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 size R1 of the single particle and the primary particles can 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 can be 1.7 to 6 μm, 2 to 5 μm, or 2.5 to 4.5 μm. The average particle size R1 is a value obtained from the SEM observation image of the surface of the first active material. It is obtained by analyzing the SEM images of the surfaces of multiple first active materials to determine the longest diameter of each single particle or primary particle and averaging it over multiple single particles or primary particles.

[0060] The BET specific surface area of ​​the first active substance can be, for example, 0.2–1.5 m². 2 / g.

[0061] The average particle size D50 of the second active substance can be, for example, 10-20 μm, preferably 12-20 μm, more preferably 13-19 μm, and even more preferably 14-18 μm.

[0062] The second active substance can be a secondary particle (hereinafter also referred to as agglomerated particle) formed by the aggregation of more than 50 primary particles. In the second active substance, the number of aggregated primary particles can be more than 100, more than 1000, or more than 10000, typically 5 × 10⁻⁶. 6 For numbers less than 1, it can be 5×10 5 The number is below 1.

[0063] When the second active material is agglomerated particles, the average particle size R2 of the primary particles constituting the agglomerated particles is less than 2.0 μm, for example, it can be greater than 0.1 μm, 0.5–1.7 μm, or 0.7–1.5 μm. The average particle size R2 is a value obtained by scanning electron microscopy (SEM) observation of the surface of the second active material. It is obtained by analyzing the SEM images of the surfaces of multiple second active materials to determine the longest diameter of each primary particle and averaging it over multiple second active materials.

[0064] The BET specific surface area of ​​the second active substance can be, for example, 0.2–1.0 m². 2 / g.

[0065] From a filler perspective, the positive electrode active material preferably includes a first active material and a second active material. When the positive electrode active material includes a first active material and a second active material, and the total mass of the positive electrode active material is set to 100% by mass, the content of the second active material can be, for example, 10-90% by mass, or 25-85% by mass. From the viewpoint of the filler density of the positive electrode composite layer, it is preferably 40-80% by mass.

[0066] Generally, when the positive electrode active material contains a first active material, it tends to cause corrosion of the positive electrode core material more easily compared to when the positive electrode active material contains a second active material. This can be attributed to the following reasons: for a positive electrode active material such as the first active material, which has a high Ni content and a small average particle size D50, (1) the structure is relatively unstable, resulting in more alkali dissolution; (2) the small average particle size D50 increases the contact area with the positive electrode core material containing Al; and (3) the low density of the first active material necessitates higher compression during the manufacturing process of the positive electrode plate in order to achieve the same density as the positive electrode composite layer containing the 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 easily suppressed, and the increase in output resistance can be prevented.

[0067] Heterocyclic compounds used in this disclosure are represented by either formula (1) or formula (2).

[0068]

[0069] In equation (1),

[0070] R a ~R c Each group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0071] X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents.

[0072]

[0073] In equation (2),

[0074] R a and R b Each group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0075] R a and R b They can bond with each other to form rings with 4 to 12 carbon atoms that can have substituents.

[0076] Z is N or C-R d ,

[0077] R d It can be a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents.

[0078] X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents.

[0079] The heterocyclic compound represented by formula (1) can be a structural isomer. Specifically, as a structural isomer of the heterocyclic compound represented by formula (1), examples include the heterocyclic compounds represented by the following formulas (1-A) to (1-G).

[0080]

[0081] [In the formula, R] a ~R c Xa Same as above.

[0082] In X a In the case of hydrogen atoms, tautomers are preferred among the above structural isomers. It should be noted that in X... a In the case of hydrogen atoms, this tautomer is also called a proton tautomer.

[0083] As R a ~R c The alkyl group having 1 to 6 carbon atoms in the phrase "alkyl group having 1 to 6 carbon atoms" can be any of the following: straight-chain, branched, or cyclic. Specific examples include straight-chain or branched alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl; and cyclic alkyl groups having 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0084] As R a ~R c Examples of alkenyl groups with 2 to 6 carbon atoms in the phrase "alkenyl groups that may have substituents" include vinyl, n-1-propenyl, n-2-propenyl, 1-methylvinyl, n-1-butenyl, n-2-butenyl, n-3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylvinyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, and n-1-pentenyl.

[0085] As R a ~R c Examples of aryl groups with 6 to 12 carbon atoms in the phrase "aryl groups that may have substituents" include phenyl, tolyl, 1-naphthyl, and 2-naphthyl.

[0086] R a ~R c It may have substituents. Examples of substituents include carboxyl, hydroxyl, aldehyde, ester, ketone, amino, phenyl, halogen atom, alkoxysilyl, epoxy, carboxyl chloride, and thiol groups. Examples of alkoxysilyl groups include trimethoxysilyl, dimethoxymethylsilyl, methoxydimethylsilyl, triethoxysilyl, diethoxymethylsilyl, and ethoxydimethylsilyl. In this disclosure, a carboxyl group is preferred. In R a ~R c When substituents are present, the number is preferably 1 to 6, more preferably 1 to 3.

[0087] As R a ~R cPreferably, it contains hydrogen atoms, carboxyl groups, alkyl groups having 1 to 6 carbon atoms that may have substituents, or aryl groups having 6 to 12 carbon atoms that may have substituents, and preferably R of the above formula (2). a and R b Rings formed by mutual bonding, which can have substituents and contain 4 to 12 carbon atoms.

[0088] Additionally, as R a ~R c More preferably, 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, and more preferably, R of the above formula (2). a and R b Rings formed by mutual bonding, which can have substituents and contain 4 to 12 carbon atoms.

[0089] Furthermore, as R a ~R c Further preferred are hydrogen atoms, carboxyl groups, alkyl groups with 1 to 3 carbon atoms or aryl groups with 6 to 10 carbon atoms, and further preferred are R of the above formula (2). a and R b Rings formed by mutual bonding, which can have 6 to 10 carbon atoms and may contain substituents.

[0090] Furthermore, as R a ~R c Further preferred are hydrogen atoms, carboxyl groups, methyl or phenyl groups, and further preferred are R of the above formula (2). a and R b Benzene rings that can have substituents are formed by mutual bonding.

[0091] Z is N or C-R d R d It can be a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have a substituent, an alkenyl group with 2 to 6 carbon atoms that may have a substituent, or an aryl group with 6 to 12 carbon atoms that may have a substituent.

[0092] As for Z, N is preferred.

[0093] As X a The alkyl group having 1 to 6 carbon atoms in the phrase "alkyl group having 1 to 6 carbon atoms" can be any of the following: straight-chain, branched, or cyclic. Specific examples include straight-chain or branched alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl; and cyclic alkyl groups having 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0094] As X aExamples of aryl groups with 6 to 12 carbon atoms in the phrase "aryl groups that may have substituents" include phenyl, tolyl, 1-naphthyl, and 2-naphthyl.

[0095] X a It may have substituents. Examples of substituents include carboxyl, hydroxyl, aldehyde, ester, ketone, amino, phenyl, halogen atom, alkoxysilyl, epoxy, carboxyl chloride, thiol, etc. Examples of alkoxysilyl groups include trimethoxysilyl, dimethoxymethylsilyl, methoxydimethylsilyl, triethoxysilyl, diethoxymethylsilyl, ethoxydimethylsilyl, etc. In this invention, carboxyl and alkoxysilyl groups are preferred, and carboxyl and trimethoxysilyl groups are more preferred.

[0096] As X a Preferably, hydrogen atoms, alkyl groups having 1 to 6 carbon atoms that may have substituents, and aryl groups having 6 to 12 carbon atoms that may have substituents.

[0097] Additionally, as X a More preferably, hydrogen atoms, alkyl groups having 1 to 4 carbon atoms, and aryl groups having 6 to 10 carbon atoms.

[0098] Furthermore, as X a Further preferred are hydrogen atoms, alkyl groups with 1 to 3 carbon atoms, and aryl groups with 6 to 8 carbon atoms.

[0099] As specific examples of heterocyclic compounds represented by formula (1), the heterocyclic compounds represented by the following formulas (1-1) to (1-14) can be cited.

[0100]

[0101] As specific examples of heterocyclic compounds represented by formula (2), the heterocyclic compounds represented by the following formulas (2-1) to (2-13) can be cited.

[0102]

[0103] The structure of the heterocyclic compound represented by formula (2-6) is the structure of the compound listed in the catalog of Shin-Etsu Chemical Co., Ltd. as X-12-1214A.

[0104] The heterocyclic compounds represented by formula (1) or formula (2) may be commercially available products. Examples of commercially available heterocyclic compounds represented by formula (1) or formula (2) include SA-426H (manufactured by Nissan Chemical Co., Ltd.) and X-12-1214A (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0105] The content of heterocyclic compounds in the positive electrode composite material layer 12 is 0.01 to 0.5% by mass relative to the mass of the positive electrode composite material layer 12. If the content of heterocyclic compounds in the positive electrode composite material layer is within the above range, the positive electrode active material is uniformly covered by heterocyclic compounds, which easily suppresses alkali dissolution from the positive electrode active material and is less likely to cause a decrease in charging capacity. If the content of heterocyclic compounds in the positive electrode composite material layer is less than 0.01% by mass, there is a tendency to be unable to suppress the corrosion of the positive electrode core material and to have difficulty suppressing the increase in output resistance. If the content of heterocyclic compounds in the positive electrode composite material layer exceeds 0.5% by mass, there is a tendency to have difficulty improving the charging capacity. In addition, when using other additives besides the above-mentioned heterocyclic compounds, in order to obtain the effect of suppressing alkali dissolution and the corrosion of the positive electrode core material caused by it, more than the content of the above-mentioned heterocyclic compounds needs to be added. As a result, due to the increased amount added, it has an adverse effect on the output characteristics, and therefore the output suppression effect cannot be obtained. From the viewpoint of output resistance and charging capacity, the content of heterocyclic compounds in the positive electrode composite material layer 12 is preferably 0.0125 to 0.3% by mass relative to the mass of the positive electrode composite material layer 12, and more preferably 0.025 to 0.2% by mass.

[0106] In addition to the positive electrode active material and the heterocyclic compound, the positive electrode composite layer 12 may also include a binder material and a conductive material. Examples of binder materials include fluoropolymers such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), and cellulose-based resins such as carboxymethyl cellulose (CMC). Examples of conductive materials include carbon materials. Examples of carbon materials include one or more selected from fibrous carbon, carbon black, coke, and activated carbon. Examples of carbon black include acetylene black (AB).

[0107] The thickness of the positive electrode composite layer 12 refers to the total thickness of the positive electrode composite layers 12 included in the laminate 40. For example, if the positive electrode composite layer 12 is formed on both sides of the positive electrode plate 10, the thickness of the positive electrode composite layer 12 refers to the total thickness of the two positive electrode composite layers 12 on both sides. The positive electrode composite layer 12 may have a thickness of, for example, 10 to 260 μm, 20 to 60 μm, or 30 to 50 μm. It should be noted that the thickness of a single positive electrode composite layer 12 on one side may, for example, be 10 to 30 μm or 15 to 25 μm.

[0108] The density of the positive electrode composite layer 12 can be, for example, 3.0–4.0 g / cm³. 3 The preferred concentration is 3.2–3.6 g / cm³. 3 .

[0109] <Manufacturing Method of Positive Electrode Plate>

[0110] The positive electrode plate 10 can be manufactured, for example, by coating a positive electrode slurry onto the positive electrode core material 11 and then drying and compressing it to form a positive electrode composite material layer 12. Figure 2 As shown, the manufacturing method of 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 manufacturing method of the positive electrode plate may further include a coating step (S2), a drying step (S3), and a compression step (S4).

[0111] In the slurry preparation step (S1), a positive electrode composite material slurry comprising a positive electrode active material and a heterocyclic compound is prepared. The positive electrode composite material slurry is prepared by dispersing the positive electrode active material and the heterocyclic compound in a dispersion medium. The dispersion medium can be, for example, an organic solvent. The organic solvent can contain, for example, at least one selected from 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 positive electrode composite material slurry can have any solids concentration (mass fraction of solids). For example, the positive electrode composite material can have a solids concentration of 40% to 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 is 0.01% to 0.5% by mass relative to the solids content in the positive electrode composite material slurry.

[0112] 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 the dispersion medium is integrally mixed with the positive electrode active material, it is possible to prevent the heterocyclic compound from adsorbing onto the positive electrode active material and thus preventing uneven dispersion of the heterocyclic compound.

[0113] In the first step, for example, the positive electrode active material, binder and dispersion medium can be mixed at a rotation speed of 10 to 20 rpm with a solid content of 85 to 95%.

[0114] In the second step, heterocyclic compounds can be added together with the dispersion medium.

[0115] The second mixture obtained in the second step can be used as a positive electrode composite slurry. Alternatively, if the positive electrode composite layer contains a conductive material, the conductive material can be added to either the first or second mixture to prepare the positive electrode composite slurry. The slurry preparation step (S1) may further include a conductive material addition step of adding the conductive material to either the first or second mixture. The conductive material addition step can be performed after the first step and before the second step, i.e., the conductive material can be added to the first mixture after the first step and before the second step. Alternatively, the conductive material addition step can be performed simultaneously with the second step, i.e., the conductive material can be added together with the heterocyclic compound in the second step. Alternatively, the conductive material addition step can be performed after the second step, i.e., the conductive material can be added to the second mixture. The conductive material can be added together with the dispersion medium.

[0116] In the conductive material addition process, for example, the first mixture or the second mixture can be mixed with the conductive material at a rotation speed of 20 to 40 rpm with a solid content of 70 to 83%.

[0117] In the coating process (S2), a coating film is formed by applying a positive electrode composite material slurry to the surface of the substrate. Any coating apparatus can be used for coating.

[0118] 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 material layer 12. The dried coating film is compressed to form the positive electrode composite material layer 12, completing the positive electrode plate 10. The positive electrode plate 10 can be cut into a specified planar size according to the battery specifications. The positive electrode plate 10 can be cut into a planar shape with a strip shape, for example. The positive electrode plate 10 can also be cut into a planar shape with a rectangular shape, for example.

[0119] <Non-aqueous electrolyte secondary battery>

[0120] The non-aqueous electrolyte secondary battery (hereinafter also referred to as a battery) disclosed herein can be a lithium-ion battery. Figure 3 This is a schematic diagram illustrating an example of the battery in this embodiment. Figure 3 The battery 100 shown may be, for example, a lithium-ion battery used in the main power supply or auxiliary power supply of an electric vehicle. By connecting multiple batteries 100, a battery module or battery pack can be formed. The battery 100 may, for example, have a rated capacity of 1 to 200 Ah.

[0121] The battery 100 includes an outer casing 90. The outer casing 90 may include, for example, a sealing plate 91 and an outer container 92. The sealing plate 91 seals the opening of the outer container 92. For example, the sealing plate 91 and the outer container 92 can be joined by laser processing or the like. It should be noted that the outer casing 90 can have any shape. For example, the outer casing 90 can be a bag shape, etc. That is, the outer casing 90 can be a bag made of Al laminated film, etc.

[0122] The outer casing 90 houses the electrode body 50 and a non-aqueous electrolyte (not shown). A positive terminal 81 and a negative terminal 82 are provided on the sealing plate 91. The sealing plate 91 may further include an injection port (not shown), a gas vent valve (not shown), etc. Electrolyte can be injected into the interior of the outer casing 90 through the injection port. The injection port can be closed, for example, by a sealing plug.

[0123] The positive current collector 71 connects the positive terminal 81 to the electrode body 50. The positive current collector 71 can be, for example, an Al plate. The negative current collector 72 connects the negative terminal 82 to the electrode body 50. The negative current collector 72 can be, for example, a copper (Cu) plate.

[0124] Figure 4 This is a schematic diagram showing an example of an electrode body in this embodiment. Figure 2 The electrode body 50 is a wound electrode body with a winding shaft 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 material layer 12 and a positive electrode core material 11.

[0125] The negative electrode plate 20 typically has 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, for example, a metal foil made of copper materials such as copper and copper alloys. The negative electrode composite material layer 22 contains a negative electrode active material and may further contain conductive materials and adhesives.

[0126] As a negative electrode active material, known materials can be cited, such as carbon-based active material particles like graphite and metal-based active material particles containing elements selected from Si, Sn, Sb, Bi, Ti, and Ge. Conductive materials can be exemplified by the aforementioned conductive materials. Adhesives can be exemplified by cellulose resins such as CMC, methylcellulose (MC), and hydroxypropyl cellulose; polyacrylic acid; and styrene-butadiene rubber (SBR). CMC can also be used as a thickener.

[0127] 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 membrane made of polyolefins such as polyethylene and polypropylene, polyester, cellulose, polyamide, etc., or a non-woven fabric. Examples of functional layers include adhesive layers and / or heat-resistant layers. Adhesive layers may be formed using adhesives. Heat-resistant layers may include fillers and adhesives.

[0128] The electrolyte preferably contains an electrolyte in a non-aqueous solvent such as an organic solvent. Examples of electrolytes include one or more of LiPF6, LiBF4, LiClO4, LiFSO3, and LiB(C2O4)2. Examples of non-aqueous solvents include one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), butyl carbonate (BC), and diethyl carbonate (DEC). The electrolyte may further contain additives such as vinylene carbonate (VC), ethylene ethylene carbonate (VEC), and fluoroethylene carbonate.

[0129] The present invention will be further described in detail below through examples.

[0130] Example

[0131] [Positive electrode active material]

[0132] As positive electrode active materials, lithium transition metal composite oxides with the molar ratios of Ni to Co to Mn (hereinafter also referred to as NCM ratios), average particle size D50, and BET specific surface area shown in Table 1 were prepared as positive electrode active materials A to H. In positive electrode active materials A to H, the molar ratio of Li to other metal elements (Me) (Li:Me) is 1.05:1. Positive electrode active materials A to D, G, and H are secondary particles (first active materials) formed by the aggregation of single particles or 2 to 5 primary particles. Positive electrode active materials E and F are secondary particles (second active materials) formed by the aggregation of more than 50 primary particles. The BET specific surface area was measured using a specific surface area measuring device.

[0133] Table 1

[0134]

[0135] <Experimental Example 1>

[0136] A positive electrode active material A, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed at a mass ratio of A:AB:PVDF = 97.5:1.5:1.0. An appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to the resulting mixture to prepare a positive electrode composite slurry. The positive electrode composite slurry was coated on both sides of an Al foil-made positive electrode core and dried to form a positive electrode composite layer. The positive electrode composite layer was rolled using rolling mills and then cut to a specified size to produce the positive electrode plate of Example 1.

[0137] <Experimental Example 2>

[0138] A positive electrode active material A, N-methyl-2-pyrrolidone (NMP), and polyvinylidene fluoride (PVDF) as a binder were mixed. Acetylene black (AB) as a conductive material and an additive containing a heterocyclic compound were then added to this mixed solution in a mass ratio of positive electrode active material A:AB:PVDF:heterocyclic compound = 97.495:1.5:1.0:0.005, and mixed to prepare a positive electrode composite slurry. The additive containing the heterocyclic compound was an N-methylpyrrolidone solution (manufactured by Nissan Chemical Co., Ltd., "SA-426H") containing 35% by mass of the heterocyclic compound represented by formula (1) or (2). The positive electrode composite slurry was coated on both sides of an Al foil positive electrode core and dried to form a positive electrode composite layer. The positive electrode composite layer was rolled using rolling rollers and then cut to a specified size to produce the positive electrode plate of Test Example 2.

[0139] <Experimental Examples 3-10>

[0140] In Experiment 2, the dosage shown in Table 2 was used, and the positive electrode plate was fabricated in the same manner as in Experiment 2.

[0141] <Experimental Examples 11-20>

[0142] In Experiment 2, the types and dosages of the positive electrode active materials shown in Table 2 were used, and the positive electrode plate was fabricated in the same manner as in Experiment 2.

[0143] [Evaluation of the fabrication of lithium-ion secondary batteries]

[0144] A negative electrode composite slurry was prepared by mixing graphite (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener in ion-exchanged water at a mass ratio of C:SBR:CMC = 98:1:1. This negative electrode composite slurry was coated onto copper foil and dried to form a negative electrode composite layer. The negative electrode composite layer was then rolled to a specified density using rolling mills and cut to specified dimensions to produce the negative electrode plate.

[0145] Porous polyolefin sheets were prepared as separators. The positive and negative electrode plates of each test example were overlapped with separators in between to create a stacked electrode body.

[0146] Electrode terminals are mounted on a stacked electrode body, which is then inserted into a battery casing made of aluminum laminates, and a non-aqueous electrolyte is injected. It should be noted that the non-aqueous electrolyte is prepared by dissolving LiPF6, as a supporting salt, at a concentration of 1 mol / L in a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of EC:EMC:DMC = 30:70, and adding ethylene carbonate at a concentration of 0.3% by mass. The battery casing is then sealed to obtain an evaluation lithium-ion secondary battery.

[0147] [Evaluation of charging capacity]

[0148] The lithium-ion secondary battery will be evaluated at a temperature of 25°C and a current density of 0.2 mA / cm². 2 Constant current charging is performed until a potential of 4.3V vs. Li / Li+ is reached, followed by constant voltage charging at 4.3V vs. Li / Li+ until a potential of 0.04mA / cm is reached. 2 The current density was used to determine the charging capacity per unit mass of the positive electrode active material [mAh / g]. The results are shown in Table 2.

[0149] [Evaluation of output resistance]

[0150] The output resistance of the evaluation lithium-ion secondary battery was measured at 25°C when the state of charge (SOC) was 50% (50% of the initial discharge capacity). The results are shown in Table 2. For the determination of output resistance, a value of 0.090Ω or higher was rated as "×", a value of less than 0.090Ω but greater than 0.080Ω was rated as "△", and a value of less than 0.080Ω was rated as "○".

[0151] Table 2

[0152]

[0153] Test Examples 3-9, 11, and 12, which contain a specified amount of heterocyclic compound and a positive electrode active material with a specified BET specific surface area, exhibit good output resistance and are able to suppress the decrease in charging capacity. In contrast, in Test Example 1, which does not contain a heterocyclic compound, the positive electrode core material (Al foil) corrodes, and the output resistance increases. Furthermore, in Test Example 2, due to the low content of the heterocyclic compound, the output resistance increases. On the other hand, in Test Example 10, due to the high content of the heterocyclic compound, the output resistance increases, and the charging capacity decreases.

[0154] Test Example 13 contained a specified amount of heterocyclic compound, but the BET specific surface area of ​​the positive electrode active material was too large, resulting in corrosion of the positive electrode core material (Al foil) and an increase in output resistance. Furthermore, Test Example 14 contained a higher amount of heterocyclic compound than Test Example 13, but the output resistance still increased.

[0155] Test Example 15 did not contain heterocyclic compounds, therefore the positive electrode core material (Al foil) corroded, and the output resistance increased. In contrast, Test Example 16, which contained the same positive electrode active material as Test Example 15, achieved good output resistance by containing a specified amount of heterocyclic compounds, thus suppressing the decrease in charging capacity.

[0156] Although the BET specific surface area of ​​the positive electrode active material in Experimental Example 17 is small, the Ni content is high and it does not contain heterocyclic compounds. Therefore, the positive electrode core material (Al foil) is corroded, and the output resistance increases.

[0157] Test Example 18 contains a positive electrode active material with a specified BET specific surface area but does not contain heterocyclic compounds, resulting in corrosion of the positive electrode core material (Al foil) and an increase in output resistance. In contrast, Test Example 19 contains a positive electrode active material with a specified BET specific surface area and contains a specified amount of heterocyclic compounds, thus exhibiting good output resistance and suppressing the reduction in charging capacity.

[0158] In Experiment 20, due to the low Ni content, no increase in output resistance was observed even though heterocyclic compounds were not included, but the charging capacity decreased.

[0159] Embodiments of the present invention have been described, but should be considered as illustrative in all respects and not restrictive. The scope of the invention is defined by the scope of the patent claims and is intended to include all variations within the meaning and scope equivalent to the scope of the patent claims.

Claims

1. A positive electrode plate for a non-aqueous electrolyte secondary battery, comprising a positive electrode composite material layer and a positive electrode core material. The positive electrode core material contains aluminum. The positive electrode composite material layer comprises a positive electrode active material and at least one heterocyclic compound represented by formula (1) or formula (2) below. In equation (1), R a ~R c Each group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents. X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents; In equation (2), R a and R b Each group can be independently composed of a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an amino group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents. R a and R b They can bond with each other to form rings with 4 to 12 carbon atoms that can have substituents. Z is N or C-R d , R d It can be a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a thiol group, an alkyl group with 1 to 6 carbon atoms that may have substituents, an alkenyl group with 2 to 6 carbon atoms that may have substituents, or an aryl group with 6 to 12 carbon atoms that may have substituents. X a It is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, or an aryl group having 6 to 12 carbon atoms that may have substituents; 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 more than 70 mol% relative to the total molar percentage of metal elements other than lithium. The BET specific surface area of ​​the positive electrode active material is 0.2–1.1 m². 2 / g, The content of the heterocyclic compound in the cathode composite material layer is 0.01 to 0.5% of the mass of the cathode composite material layer.

2. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein, The positive electrode active material includes a first active material with an average particle size 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 substance is a single particle or a secondary particle formed by the aggregation of 2 to 10 primary particles.

4. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 2, wherein, The BET specific surface area of ​​the first active substance is 0.2–1.5 m². 2 / 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 with an average particle size D50 of 10–20 μm.

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

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

8. A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery, which is the method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery as described in claim 1. The process includes a slurry preparation step, in which the positive electrode active material is mixed with the heterocyclic compound to obtain a positive electrode composite material slurry.

9. The method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 8, wherein, The slurry preparation process includes: The first step involves mixing the positive electrode active material, binder, and dispersion medium to obtain a first mixture; as well as In the second step, the first mixture is mixed with the heterocyclic compound to obtain a second mixture.

10. The method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 8, wherein, The positive electrode active material is mixed with the heterocyclic compound in such a way that the content of the heterocyclic compound is 0.01 to 0.5% by mass relative to the solid content in the positive electrode composite slurry.

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

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