Lithium-ion battery

Abstract

To provide a lithium-ion battery with improved chemical short circuit resistance while suppressing an increase in the battery's internal resistance. [Solution] A lithium-ion battery having an electrode group in which a positive electrode plate and a negative electrode plate are stacked with a separator in between, wherein the positive electrode plate comprises, in this order, a positive electrode current collector foil, a first positive electrode composite layer that does not contain dielectric particles, and a second positive electrode composite layer that contains dielectric particles.

Description

[Technical Field]

[0001] This disclosure relates to lithium-ion batteries. [Background technology]

[0002] In recent years, lithium-ion batteries have been widely used in electric vehicles, hybrid vehicles, small electronic devices (smartphones, laptop computers), and energy equipment.

[0003] These lithium-ion batteries may contain metallic impurities originating from the manufacturing process or from the raw materials of the positive electrode active material. These metallic impurities move within the battery during charging and discharging, and can accumulate near the battery's separator, forming dendritic metal deposits (dendrites). These dendrites can lead to chemical short circuits.

[0004] In lithium-ion batteries, increasing the curvature and thickness of the battery separator is effective in improving resistance to chemical short circuits caused by metallic foreign matter.

[0005] Patent Document 1 discloses a secondary battery comprising an electrode body in which a positive electrode sheet, a negative electrode sheet, and a separator insulating the positive electrode sheet and the negative electrode sheet are laminated, wherein a part of the separator is formed of a plurality of porous layers with different curvature ratios, the curvature ratio in the part of the separator is greater than the curvature or curvature ratio of the other part of the separator, and the curvature ratio is the ratio of the curvature of the first porous layer of the separator, which is arranged adjacent to the negative electrode sheet, to the curvature of the second porous layer of the separator, which is arranged adjacent to the positive electrode sheet. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-40737 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the method described in Patent Document 1 had the problem that the film resistance of the separator increased, which in turn increased the internal resistance of the battery.

[0008] One embodiment of this disclosure aims to solve the problem of providing a lithium-ion battery with improved chemical short circuit resistance while suppressing an increase in the battery's internal resistance. [Means for solving the problem]

[0009] The means for solving the above problems include the following embodiments. <1> A lithium-ion battery having an electrode group in which a positive electrode plate and a negative electrode plate are stacked with a separator in between, wherein the positive electrode plate comprises, in this order, a positive electrode current collector foil, a first positive electrode composite layer that does not contain dielectric particles, and a second positive electrode composite layer that contains dielectric particles. <2> The relative permittivity of the dielectric particles is 1,000 to 1,500 at 25°C. <1> Lithium-ion batteries as described above. <3> The dielectric particles are particles of a compound selected from the group consisting of barium titanate, lead zirconate titanate (PZT), calcium barium titanate, and lead titanate. <1> or <2> Lithium-ion batteries as described above. <4> The content of the dielectric particles is 0.1% by mass to 5.0% by mass relative to the total mass of the second cathode composite layer. <1> ~ <3> A lithium-ion battery as described in one of the following documents. <5> The thickness of the second cathode composite layer is 10 μm to 30 μm. <1> ~ <4> A lithium-ion battery as described in one of the following documents. <6> The sum of the thickness of the first cathode composite layer and the thickness of the second cathode composite layer is 20 μm to 50 μm. <1> ~ <5> A lithium-ion battery as described in one of the following documents. [Effects of the Invention]

[0010] According to an embodiment of the present disclosure, a lithium-ion battery with improved chemical short-circuit resistance while suppressing an increase in the internal resistance of the battery is provided.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the structure of the lithium-ion battery of the present disclosure.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described.

[0013] In this specification, a numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In this specification, each component may include a plurality of corresponding substances. When referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition. Note that "mass%" and "weight%" in this specification are synonymous, and the latter may be denoted as "wt%".

[0014] <Lithium-Ion Battery> The lithium-ion battery of the present disclosure is a lithium-ion battery having an electrode group in which a positive electrode plate and a negative electrode plate are laminated via a separator, and the positive electrode plate includes a positive electrode current collector foil, a first positive electrode composite layer not containing dielectric particles, and a second positive electrode composite layer containing dielectric particles, in this order. With the above configuration, while suppressing an increase in the internal resistance of the battery, the chemical short-circuit resistance is improved. "Chemical short circuit" refers to a type of short circuit that differs from a physical short circuit caused by the inclusion of foreign matter. It occurs when metals or other materials contained within a conductor repeatedly dissolve or precipitate, causing the conductor to penetrate internally.

[0015] Figure 1 is a schematic cross-sectional view showing an example of the structure of a lithium-ion battery of the present disclosure. As shown in Figure 1, the lithium-ion battery 100 of the present disclosure has an electrode group in which a positive electrode plate 10 and a negative electrode plate 20 are stacked with a separator 30 in between, and the positive electrode plate 10 comprises, in this order, a positive electrode current collector foil 11, a first positive electrode composite layer 12 that does not contain dielectric particles, and a second positive electrode composite layer 13 that contains dielectric particles.

[0016] The positive electrode plate 10 is composed of two positive electrode composite layers: a first positive electrode composite layer 12 that does not contain dielectric particles, and a second positive electrode composite layer 13 that contains dielectric particles. In the second positive electrode composite layer 13 that contains dielectric particles, metal ions from metallic foreign matter are attracted to or repelled by polarized dielectric particles, and diffuse in the in-plane or out-of-plane direction. As a result, the curvature of the metal ions on the separator side increases, making it difficult for dendrites to form. Therefore, chemical short circuit resistance is improved. The lithium-ion battery of this disclosure does not increase the curvature or thickness of the separator, and therefore does not increase the internal resistance of the battery due to the film resistance of the separator. Accordingly, it is possible to improve chemical short circuit resistance while suppressing the increase in the internal resistance of the battery. The lithium-ion battery of this disclosure has a first positive electrode composite layer 12 that does not contain dielectric particles on the positive electrode current collector foil 10 side, and a second positive electrode composite layer 13 that contains dielectric particles on the separator 30 side, so that the dielectric particles do not hinder electron movement between the positive electrode current collector foil and the positive electrode composite layer.

[0017] (Positive plate) As described above, the positive electrode plate comprises, in this order, a positive electrode current collector foil, a first positive electrode composite layer that does not contain dielectric particles, and a second positive electrode composite layer that contains dielectric particles.

[0018] -Positive current collector foil- The positive electrode current collector foil may be made of aluminum, an aluminum alloy, stainless steel, or the like. The thickness of the positive electrode current collector foil may be, for example, 5 μm to 30 μm.

[0019] - First positive electrode composite material layer不含 dielectric particles - The first positive electrode composite material layer不含 dielectric particles is the positive electrode composite material layer disposed on the positive electrode current collector foil side. The first positive electrode composite material layer不含 dielectric particles may include a positive electrode active material, a conductive assistant, and a binder.

[0020] Examples of the positive electrode active material include lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4), lithium nickel cobalt manganese oxide (NCM) (LiNi x Mn y Co z O2, x + y + z = 1, 0 < x < 1, 0 < y < 1, 0 < z < 1), lithium nickel cobalt aluminum oxide (NCA) (LiNi x Co y Al z O2, x + y + z = 1, 0 < x < 1, 0 < y < 1, 0 < z < 1), lithium iron phosphate (LiFePO4), and other lithium transition metal composite oxides.

[0021] The shape of the positive electrode active material is not particularly limited and may be, for example, spherical (e.g., true spherical, ellipsoidal, etc.). From the perspective of improving the diffusivity of lithium ions inside the positive electrode active material, the shape of secondary particles in which primary particles are aggregated in a hollow shape is preferable.

[0022] The volume average particle diameter D 50 of the positive electrode active material may be 0.1 μm to 30 μm, preferably 1 μm to 10 μm. The volume average particle diameter D 50 of the positive electrode active material is the particle diameter value at which the cumulative distribution is drawn from the small particle size side with respect to volume after obtaining the particle size distribution using a laser wave form particle size distribution measuring device (e.g., LS 13 320 manufactured by Beckman Coulter) and the cumulative 50% for all particles.

[0023] The content of the positive electrode active material may be 97% to 99% by mass relative to the total mass of the first positive electrode composite layer.

[0024] Examples of conductive additives that can be used include acetylene black, Ketjenblack, vapor-processed carbon fiber (VGCF®), and carbon nanotubes (CNTs). The content of the conductive additive may be 0.5% to 1.0% by mass relative to the total mass of the first cathode composite layer.

[0025] Polyvinylidene fluoride (PVDF), modified polyvinylidene fluoride (modified PVDF), polytetrafluoroethylene (PTFE), etc., can be used as binders. Among these, polyvinylidene fluoride (PVDF) is preferred because it has excellent binding properties, chemical stability, and swelling properties, and suppresses the retention of metal ions. One type of binder may be used alone, or two or more types may be used in combination. The binder content may be 0.5% to 2.0% by mass relative to the total mass of the first cathode composite layer.

[0026] The thickness of the first positive electrode composite layer, which does not contain dielectric particles, is preferably 10 μm to 20 μm. A thickness of 10 μm to 20 μm in the first positive electrode composite layer suppresses the increase in the internal resistance of the battery while improving chemical short circuit resistance. If the thickness of the first positive electrode composite layer is less than 10 μm, coating film formation becomes difficult, and it may be difficult to form the first positive electrode composite layer. If the thickness of the first positive electrode composite layer exceeds 20 μm, the internal resistance of the battery increases, while chemical short circuit resistance tends to decrease.

[0027] -Second cathode composite layer containing dielectric particles- The second positive electrode composite layer, which contains dielectric particles, is the positive electrode composite layer located on the separator side. The second positive electrode composite layer contains dielectric particles.

[0028] Since the second positive electrode composite layer contains polarized dielectric particles, metal ions due to metal foreign matter are attracted to the dielectric particles or repelled by the dielectric particles and diffuse in the in-plane direction or the out-of-plane direction. As a result, the tortuosity of the metal ions on the separator side increases, making it difficult to form dendrites. Therefore, the chemical short-circuit resistance is improved.

[0029] From the perspective of increasing the polarizability and improving the attraction of metal ions or repulsion with metal ions, the relative permittivity of the dielectric particles is preferably 500 to 2,000 at 25 °C, more preferably 1,000 to 2,000 at 25 °C, and even more preferably 1,000 to 1,500 at 25 °C.

[0030] Specifically, as the dielectric particles, particles of compounds selected from the group consisting of barium titanate, lead zirconate titanate (PZT), calcium barium titanate, and lead titanate are preferred.

[0031] The volume average particle diameter D of the dielectric particles 50 is preferably 2 μm to 3 μm, more preferably 1 μm to 2 μm, and even more preferably 0.5 μm to 1.5 μm from the perspective of suppressing excessive coating of the positive electrode active material and increasing the internal resistance of the battery.

[0032] The volume average particle diameter D of the dielectric particles 50 is determined by the same method as described for the volume average particle diameter D of the positive electrode active material particles 50 .

[0033] The dielectric particle content is preferably 0.1% to 5.0% by mass, more preferably 0.5% to 4.0% by mass, and even more preferably 1.0% to 3.0% by mass, relative to the total mass of the second positive electrode composite layer. When the dielectric particle content is 0.1% to 5.0% by mass, relative to the total mass of the second positive electrode composite layer, it is easier to improve chemical short circuit resistance while suppressing an increase in the internal resistance of the battery. If the dielectric particle content is less than 0.1% by mass, relative to the total mass of the second positive electrode composite layer, the effects of this disclosure cannot be obtained. If the dielectric particle content exceeds 5.0% by mass, relative to the total mass of the second positive electrode composite layer, the positive electrode active material may be overcoated, which may increase the internal resistance of the battery.

[0034] The second positive electrode composite layer may contain dielectric particles, a positive electrode active material, a conductive additive, and a binder. Examples of positive electrode active material, conductive additive, and binder used in the second positive electrode composite layer are the same as those exemplified in the description of the first positive electrode composite layer. The mixing ratios of these materials may also be the same as those for the first positive electrode composite layer.

[0035] The thickness of the second positive electrode composite layer is preferably 10 μm to 30 μm, more preferably 10 μm to 20 μm, and even more preferably 10 μm to 15 μm. A thickness of 10 μm to 30 μm for the second positive electrode composite layer tends to improve chemical short circuit resistance while suppressing an increase in the internal resistance of the battery. If the thickness of the second positive electrode composite layer is less than 10 μm, it becomes difficult to form a coating film, and it may be difficult to form the second positive electrode composite layer. If the thickness of the second positive electrode composite layer exceeds 30 μm, the internal resistance of the battery tends to increase, while chemical short circuit resistance also tends to decrease.

[0036] In the lithium-ion battery of this disclosure, the sum of the thicknesses of the first cathode composite layer and the second cathode composite layer is preferably 20 μm to 50 μm, more preferably 20 μm to 45 μm, and even more preferably 30 μm to 40 μm. When the sum of the thicknesses of the first cathode composite layer and the second cathode composite layer is 20 μm to 50 μm, it is easier to improve chemical short circuit resistance while suppressing an increase in the internal resistance of the battery. If the sum of the thicknesses of the first cathode composite layer and the second cathode composite layer is less than 20 μm, it may be difficult to form the cathode layer. If the sum of the thicknesses of the first cathode composite layer and the second cathode composite layer exceeds 50 μm, the internal resistance of the battery tends to increase, and chemical short circuit resistance also tends to decrease.

[0037] -curvature rate- The chemical short-circuit tolerance of the lithium-ion battery of this disclosure can be evaluated using the curve ratio expressed by the following formula.

[0038]

number

[0039] In the formula, τ is the curve ratio, and κ is the ionic conductivity (S·m) of the non-aqueous electrolyte. -1 ), ε is the porosity (%) of the positive electrode composite layer, and S is the area (μm²) of the positive electrode composite layer. 2 ), L is the thickness of the positive electrode composite layer (μm), R ion The ionic resistance (Ω) in the positive electrode composite layer is -1 ·cm -2 ) and R ion This can be calculated using AC impedance analysis. The ionic conductivity κ of a non-aqueous electrolyte is a value determined by the AC impedance method. The porosity ε of the positive electrode composite layer is obtained by dividing the composite density by the true density of the composite (the density assuming the porosity of the electrode plate is 0%).

[0040] The curvature ratio of the first cathode composite layer of the lithium-ion battery disclosed herein is preferably 5 to 7, more preferably 6 to 8, and even more preferably 7 to 9. A curvature ratio of 7 to 9 in the first cathode composite layer tends to improve chemical short circuit resistance.

[0041] The curvature of the second cathode composite layer of the lithium-ion battery disclosed herein is preferably 5.5 to 10.5, more preferably 6.5 to 9.5, and even more preferably 7.4 to 8.5. A curvature of 5.5 to 10.5 in the second cathode composite layer tends to improve chemical short circuit resistance.

[0042] (Negative electrode plate) The negative electrode plate may comprise a negative electrode current collector foil and a negative electrode composite layer formed on the negative electrode current collector foil. Copper foil is preferred as the negative electrode current collector foil. The negative electrode composite layer may contain a negative electrode active material and a binder.

[0043] Examples of negative electrode active materials include carbon-based active materials such as graphite; lithium titanate (e.g., Li4Ti5O4). 12 Oxide-based active materials such as ) and Si-based active materials such as elemental Si, SiO, SiC, and Si alloys can be used. Volume average particle size D of the negative electrode active material 50 The volume-average particle size D of the negative electrode active material may be between 0.1 μm and 100 μm. 50 This is the volume-average particle size D of the positive electrode active material particles. 50 This value is determined by the same method as described above. The content of the negative electrode active material may be 97% to 98% by mass relative to the total mass of the negative electrode composite layer.

[0044] In addition to polyvinylidene fluoride (PVDF), other binders such as styrene-butadiene rubber (SBR), polyacrylic acid, and polyimide can be used. The binder content may be 1% to 2% by mass relative to the total mass of the negative electrode composite layer. The binder may also contain carboxymethylcellulose (CMC) as a thickening agent.

[0045] (Method of manufacturing lithium-ion batteries) The lithium-ion battery of this disclosure can be manufactured by stacking a positive electrode plate and a negative electrode plate with a separator in between.

[0046] The positive electrode plate can be manufactured as follows: First, a first positive electrode composite slurry, which does not contain dielectric particles, is applied to the positive electrode current collector foil, dried, and pressed to form the first positive electrode composite layer. Next, a second cathode composite slurry containing dielectric particles is applied to the first cathode composite layer, dried, and pressed to form a second cathode composite layer. As described above, a positive electrode plate can be manufactured.

[0047] A first positive electrode composite slurry that does not contain dielectric particles is obtained by adding a solvent to a mixture of positive electrode active material, a binder, and a conductive additive in a predetermined composition ratio, and kneading the mixture.

[0048] As solvents, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), etc., can be used.

[0049] Mixing can be carried out by appropriately selecting from among mixing methods such as planetary mixers, sand mills, ball mills, gyroscopic mills, roll mills, extruders, and dispersers.

[0050] The coating can be applied by die coating, doctor blade coating, gravure coating, etc. The coating amount may be determined as appropriate to achieve the desired electrode density and dry thickness.

[0051] Drying can be carried out by natural drying, reduced-pressure drying, or heat drying. For example, if the asphalt slurry contains NMP, heat drying at 80°C to 135°C may be used.

[0052] Pressing can be performed using a roll press, a flat plate press, etc. A roll press may be used with a linear pressure of 0.01 t / cm to 1.0 t / cm and a roll temperature of 80°C to 135°C.

[0053] The second cathode composite slurry containing dielectric particles can be prepared in the same manner as the first cathode composite slurry, and the second cathode composite layer can be formed in the same manner as the first cathode composite layer.

[0054] As described above, a positive electrode plate can be manufactured, and a negative electrode plate can also be manufactured using the same method as the positive electrode plate.

[0055] The lamination of the positive and negative electrode plates may be done manually or using a lamination device. As the separator, a porous resin sheet such as polyethylene or polypropylene can be used.

[0056] The lithium-ion battery of this disclosure may include a non-aqueous electrolyte, the non-aqueous electrolyte comprising an electrolyte and a non-aqueous solvent.

[0057] Examples of electrolytes include LiPF6, LiBF4, LiAsF6, LiSbF6, Li(CF3SO2)2N, Li(C2F5SO2)2N, LiTaF6, LiClO4, and LiCF3SO3. Electrolytes may be used individually or in combination of two or more.

[0058] Examples of non-aqueous solvents include cyclic carbonate solvents such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), and difluoroethylene carbonate (DFEC); linear carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC); ether solvents such as 1,2-dimethoxyethane, tetrahydrofuran, and dioxolane; γ-butyrolactone; acetonitrile; and others. Non-aqueous solvents may be used individually or in mixtures of two or more. When using both a cyclic carbonate solvent and a linear carbonate solvent, the mixing ratio of the cyclic carbonate solvent to the linear carbonate solvent may be, for example, 1:9 to 5:5 by volume.

[0059] The concentration of the solid electrolyte in the non-aqueous solvent may be between 1.0 mol / L and 1.2 mol / L.

[0060] The lithium-ion battery of this disclosure can take on various shapes, such as cylindrical, stacked, or coin-shaped. An electrode group in which a positive electrode plate and a negative electrode plate are stacked with a separator in between is completed as a lithium-ion battery by connecting the positive electrode current collector foil and the negative electrode current collector foil to the positive electrode terminal and the negative electrode terminal, respectively, via leads, and sealing it in an outer case together with a non-aqueous electrolyte. [Examples]

[0061] The embodiments of this disclosure will be described in more detail below with reference to examples. The embodiments of this disclosure are not limited to the following examples.

[0062] <Example 1> -Fabrication of the positive electrode plate- NCM111 was used as the positive electrode active material, carbon nanotubes (CNTs) as a conductive additive, and PVDF as a binder. NMP was added to this mixture and kneaded to prepare a first positive electrode composite slurry that did not contain dielectric particles and had a composition ratio (mass ratio) of positive electrode active material:CNT:PVDF = 98:1:1. Next, the slurry was applied onto aluminum foil (12 μm thick) using a doctor blade and dried, then pressed with a roll press to form the first cathode composite layer (15 μm thick). Next, NCM111 was used as the positive electrode active material, carbon nanotubes (CNTs) as a conductive additive, PVDF as a binder, and barium titanate as dielectric particles. NMP was added to this mixture and kneaded to prepare a second positive electrode composite slurry containing dielectric particles with a composition ratio (mass ratio) of positive electrode active material:CNTs:PVDF:barium titanate = 96:1:1:2. The amount of barium titanate was 2.0% by mass relative to the total mass of the second positive electrode composite layer. Next, the second cathode composite slurry was applied onto the first cathode composite layer using a doctor blade, dried, and then pressed with a roll press to form the second cathode composite layer (25 μm thick). In this manner, a positive electrode plate (thickness 40 μm) was obtained, comprising, in this order, a positive electrode current collector foil, a first positive electrode composite layer (composite layer 1) that does not contain dielectric particles, and a second positive electrode composite layer (composite layer 2) that contains dielectric particles.

[0063] - Preparation of test cells - An evaluation test cell was fabricated using a positive electrode plate. The positive electrode plate was punched out into a long shape of 45 mm × 60.5 mm / coated area 47 mm / uncoated area 13.5 mm, and laminated with a separately prepared negative electrode plate of 47 mm × 62.5 mm / coated area 49 mm / uncoated area 13.5 mm via a separator to form a laminate-type test cell. The electrolyte used was a non-aqueous electrolyte in which LiPF6 was dissolved at a concentration of 1.0 mol / L in a mixed solvent of EC and EMC (volume ratio 1:3).

[0064] -DCIR ratio (%)- The DCIR (Direct Current Internal Resistance) of the test cells was measured using a DCIR measuring instrument (Toyo Technica "Scribner") under the conditions of 25°C, SOC (State of Charge) 30%, and C / D ratios of 5C, 10C, and 20C. Next, the DCIR ratio (relative value) (%) of the test cell prepared using the positive electrode plate of Comparative Example 1 was set to 100. The results are shown in Table 1.

[0065] -curvature rate- The curve ratio for the positive electrode plate was calculated using the following formula. The results are shown in Table 1.

[0066]

number

[0067] -Chemical slight resistance- Chemical tolerance was evaluated according to the following criteria. The results are shown in Table 1. A... The curvature ratio of the second positive electrode composite layer is 8 or more. B... The curvature ratio of the second positive electrode composite layer is less than 8.

[0068] <Example 2> A positive electrode plate (thickness 40 μm) was obtained in the same manner as in Example 1, except that the amount of barium titanate in the second positive electrode composite layer (thickness 25 μm) was 3.0% by mass relative to the total mass of the second positive electrode composite layer. Furthermore, a test cell was prepared and evaluated in the same manner as in Example 1.

[0069] <Comparative Example 1> Except for not forming a second cathode composite layer, a cathode plate (thickness 40 μm) was obtained in the same manner as in Example 1, and the test cell was then prepared and evaluated in the same manner as in Example 1.

[0070] [Table 1]

[0071] The results in Table 1 show that the positive electrode composite layer containing dielectric particles exhibits increased curvature and improved chemical short circuit resistance compared to the positive electrode composite layer without dielectric particles (Examples 1 and 2). Increasing the amount of dielectric particles further increased the curvature and improved chemical short circuit resistance (Example 2). On the other hand, the lithium-ion batteries of Examples 1 and 2 did not show any increase in internal resistance compared to the lithium-ion battery of Comparative Example 1, indicating that the increase in internal resistance was suppressed. [Explanation of symbols]

[0072] 100 Lithium-ion batteries 10 Positive plate 11 Positive electrode current collector foil 12. First positive electrode composite layer 13. Second positive electrode composite layer 20 Negative electrode plates 21 Negative electrode current collector foil 22 Negative electrode composite layer 30 Separators p dielectric particles

Claims

1. A lithium-ion battery having an electrode group in which a positive electrode plate and a negative electrode plate are stacked with a separator in between, The positive electrode plate is Positive electrode current collector foil, A first positive electrode composite layer that does not contain dielectric particles, A second positive electrode composite layer containing dielectric particles, It has these in this order: Lithium-ion battery.

2. The lithium-ion battery according to claim 1, wherein the relative permittivity of the dielectric particles is 1,000 to 1,500 at 25°C.

3. The lithium-ion battery according to claim 1, wherein the dielectric particles are particles of a compound selected from the group consisting of barium titanate, lead zirconate titanate (PZT), barium calcium titanate, and lead titanate.

4. The lithium-ion battery according to claim 1, wherein the content of the dielectric particles is 0.1% by mass to 5.0% by mass with respect to the total mass of the second positive electrode composite layer.

5. The lithium-ion battery according to claim 1, wherein the thickness of the second positive electrode composite layer is 10 μm to 30 μm.

6. The lithium-ion battery according to claim 1, wherein the sum of the thickness of the first cathode composite layer and the thickness of the second cathode composite layer is 20 μm to 50 μm.

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