Lithium ion battery negative electrode and lithium ion battery
By optimizing the compaction density, coating weight, and thickness of the lithium-ion battery anode material, and combining it with conductive agents and binders, the problem of self-discharge current in lithium-ion batteries was solved, resulting in higher capacity retention and lower self-discharge current.
Patent Information
- Application Number
- CN202410543903.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-30
- Publication Date
- 2025-10-31
AI Technical Summary
There is still room for improvement in the self-discharge current of existing lithium-ion batteries, which affects battery performance.
By optimizing the material composition and structural parameters of the lithium-ion battery anode, including the compaction density, coating weight, and thickness of the anode material, and combining the use of conductive agents and binders, a negative electrode material is formed, reducing diffusion resistance and increasing capacitance.
It significantly improves the self-discharge current of lithium-ion batteries, enhances the battery's capacity retention rate under high-temperature storage conditions, and reduces the self-discharge current.
Smart Images
Figure CN120878720A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of batteries, and more particularly to a lithium-ion battery negative electrode and a lithium-ion battery. Background Technology
[0002] Batteries experience self-discharge when left unattended in an open-circuit environment, resulting in a loss of battery capacity. Based on whether the lost capacity can be recovered, self-discharge is generally classified into physical self-discharge (recoverable capacity loss) and chemical self-discharge (irrecoverable capacity loss). Both types of self-discharge can coexist within the battery.
[0003] Self-discharge is an important indicator of battery performance. Self-discharge can be measured by self-discharge current. For example, the charging current when the battery is kept at the desired open circuit voltage (OCV) can be measured, and the measured charging current can be considered as the battery self-discharge current.
[0004] The self-discharge current is affected by various components inside the battery, such as the positive electrode material, negative electrode material, and electrolyte. Furthermore, the self-discharge current is also influenced by environmental factors, the number of battery cycles, and the battery's state of charge (SOC).
[0005] While lithium-ion batteries generally have a higher self-discharge current than lead-acid and nickel-metal hydride batteries, they still exhibit a certain degree of self-discharge. Although some lithium batteries in the current technology have made improvements in these aspects, there is still room for further improvement in their self-discharge current. Summary of the Invention
[0006] The purpose of this invention is to provide a lithium-ion battery negative electrode and a lithium-ion battery and its uses, so as to improve the self-discharge current of lithium-ion batteries.
[0007] In one aspect, the present invention provides a negative electrode for a lithium-ion battery, comprising a negative electrode current collector and a negative electrode material coated on the negative electrode current collector, wherein the compaction density of the negative electrode material is 1.3-1.7 g / cm³. 3 For example, the compaction density of the negative electrode material can be 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, or 1.7 g / cm³. 3 Or a subrange consisting of any values within these ranges. Preferably, the compaction density of the negative electrode material is 1.3-1.6 g / cm³. 3 Most preferably, the compaction density of the negative electrode material is 1.4-1.5 g / cm³. 3 .
[0008] In one embodiment, the single-sided coating weight of the negative electrode material on the negative electrode current collector is 3.5-6.5 mg / cm³. 2 For example, the single-sided coating weight of the negative electrode material on the negative electrode current collector can be 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, or 6.5 mg / cm³. 2 Or a subrange consisting of any values within these ranges. Preferably, the single-sided coating weight of the negative electrode material on the negative electrode current collector is 4-6.5 mg / cm³. 2 Most preferably, the weight of the negative electrode material coated on one side of the negative electrode current collector is 4.5-5.1 mg / cm³. 2 .
[0009] In one embodiment, the thickness of the negative electrode material on one side is 20-50 μm. For example, the thickness of the negative electrode on one side can be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 μm, or a subrange consisting of any values within these ranges. Preferably, the thickness of the negative electrode material on one side is 25-45 μm. Most preferably, the thickness of the negative electrode material on one side is 32-38 μm.
[0010] In one embodiment, the diffusion resistance of the negative electrode is 2.5-4 Ω*cm. 2 For example, the diffusion resistance of the negative electrode can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4.0 Ω*cm. 2 Or a subrange consisting of any values within these ranges. Preferably, the diffusion resistance of the negative electrode is 2.8-3.8 Ω*cm. 2 Most preferably, the diffusion resistance of the negative electrode is 3.0-3.1 Ω*cm. 2 .
[0011] In one embodiment, the diffusion resistivity of the negative electrode is 500-1500 Ω*cm. For example, the diffusion resistivity of the negative electrode can be 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1150, 1200, 1250, 1300, 1350, 1400, 1450, or 1500 Ω*cm, or a subrange of any value within these ranges. Preferably, the diffusion resistivity of the negative electrode is 700-1300 Ω*cm. Most preferably, the diffusion resistivity of the negative electrode is 750-1000 Ω*cm.
[0012] In one embodiment, the capacitance of the negative electrode is 7-12 mF. For example, the capacitance of the negative electrode can be 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, or 12 mF, or a subrange of any value within these ranges. Preferably, the capacitance of the negative electrode is 8.5-11 mF. Most preferably, the capacitance of the negative electrode is 9.5-10.5 mF.
[0013] In one embodiment, the negative electrode includes at least a negative electrode active material, such as artificial graphite and / or silicon carbide material.
[0014] In one embodiment, the mass ratio of artificial graphite to silicon carbide can be 1.5-10, for example, it can be 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5 or 10.0, or a subrange consisting of any values in these ranges.
[0015] In one embodiment, the negative electrode may also include a conductive agent, such as superconducting carbon black (SP) and / or single-walled carbon nanotubes (SWCNTs).
[0016] In one embodiment, the mass ratio of superconducting carbon black to single-walled carbon nanotubes can be 3-30, for example, it can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30, or a subrange consisting of any values in these ranges.
[0017] In one embodiment, the negative electrode may also include a binder, such as carboxymethyl cellulose (CMC) and / or styrene-butadiene rubber (SBR).
[0018] In a preferred embodiment, the negative electrode includes a negative electrode active material, a conductive agent, and a binder.
[0019] Furthermore, the inventors unexpectedly discovered that the negative electrode of a lithium-ion battery having a combination of features from the above embodiments can improve the self-discharge current of the lithium-ion battery better than the negative electrode of the lithium-ion battery in the above embodiments.
[0020] In a preferred embodiment, the compaction density of the negative electrode material is 1.3-1.7 g / cm³. 3 (For example, the compaction density of the negative electrode material can be 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65 or 1.7 g / cm³) 3 (or a subrange consisting of any values within these ranges), the single-sided coating weight of the negative electrode material on the negative electrode current collector is 3.5-6.5 mg / cm³. 2 (The single-sided coating weight of the negative electrode material on the negative electrode current collector can be 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, or 6.5 mg / cm³) 2 The thickness of the negative electrode material on one side is 20-50 μm (e.g., the thickness of the negative electrode on one side can be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 μm, or a subrange of any value within these ranges). More preferably, the compaction density of the negative electrode material is 1.3-1.6 g / cm³. 3 The single-sided coating weight of the negative electrode material on the negative electrode current collector is 4-6.5 mg / cm³. 2 Furthermore, the thickness of the negative electrode material on one side is 25-45 μm. Most preferably, the compaction density of the negative electrode material is 1.4-1.5 g / cm³. 3 The single-sided coating weight of the negative electrode material on the negative electrode current collector is 4.5-5.1 mg / cm³. 2 Furthermore, the thickness of the negative electrode material on one side is 32-38 μm. Compared to embodiments that only limit one of the compaction density of the negative electrode material, the weight of the negative electrode material coated on one side of the negative electrode current collector, or the thickness of the negative electrode material on one side, this embodiment can better improve the self-discharge current of the lithium-ion battery.
[0021] In another aspect, the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a casing, wherein the negative electrode is the negative electrode of the lithium-ion battery as described above.
[0022] In one embodiment, the lithium-ion battery retains a capacity of 83.2%-86% after a 30-day storage test at 60°C. For example, it can be 83.2%, 83.3%, 83.4%, 83.5%, 83.6%, 83.7%, 83.8%, 83.9%, 84.0%, 84.1%, 84.2%, 84.3%, 84.4%, 84.5%, 84.6%, 84.7%, 84.8%, 84.9%, 85.0%, 85.1%, 85.2%, 85.3%, 85.4%, 85.5%, 85.6%, 85.7%, 85.8%, 85.9%, or 86.0%, or a sub-range consisting of any values within these ranges. Preferably, the lithium-ion battery retains a capacity of 84%-85% after a 30-day storage test at 60°C.
[0023] In another aspect, the present invention provides the use of the negative electrode of the lithium-ion battery as described above for reducing the self-discharge current of the lithium-ion battery. Attached Figure Description
[0024] Figure 1 The specific capacity retention rates of Examples 1-3 are depicted. In the figures, the value after PD refers to the compaction density of the negative electrode material. For example, PD 1.40 means that the compaction density of the negative electrode material is 1.40 g / cm³. 3 The number after # is the corresponding repeating number.
[0025] Figure 2 The self-discharge current of Examples 1-3 is depicted. In the figures, the value after PD refers to the compaction density of the negative electrode material. For example, PD 1.40 means that the compaction density of the negative electrode material is 1.40 g / cm³. 3 The number after # is the corresponding repeating number.
[0026] Figure 3 This reflects the relationship between the compaction density of the negative electrode material, the negative electrode capacitance, and the self-discharge current in Examples 1-3. Detailed Implementation
[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.
[0028] In this invention, each value can be an approximate value after rounding.
[0029] In this invention, the defined range of intervals all include endpoint values.
[0030] In this invention, unless otherwise stated, all tests are performed at room temperature. All parameters are measured at room temperature. The room temperature can be 10-35°C, preferably 20-30°C, and most preferably 25°C.
[0031] In this invention, the electrochemical parameters of the negative electrode (e.g., diffusion resistance, diffusion resistivity, capacitance) can be obtained, for example, through a corresponding symmetric cell.
[0032] In this invention, the current collector is a chemically inactive, electronically highly conductive material used to continuously carry current through an electrode (positive or negative electrode) during discharge or charging. The current collector can take the shape of foil, plate, mesh, etc., and there is no particular limitation as long as the shape corresponds to the purpose. Preferably, the current collector is in the shape of a foil. Examples of current collectors include aluminum foil, aluminum mesh, perforated aluminum sheet, aluminum extended sheet, stainless steel foil, stainless steel mesh, perforated stainless steel sheet, stainless steel extended sheet, extended nickel, nickel nonwoven fabric, copper foil, copper mesh, perforated copper sheet, copper extended sheet, titanium foil, titanium mesh, carbon nonwoven fabric, carbon fabric, etc.
[0033] In one embodiment, the negative electrode of the lithium-ion battery of the present invention may be, for example, sheet-like, comprising a negative electrode current collector and a negative electrode material.
[0034] In one embodiment, the negative electrode current collector may have a thickness of, for example, 5 μm to 50 μm.
[0035] In one embodiment, the negative electrode current collector is a copper foil.
[0036] In this invention, the negative electrode material is formed on the surface of the negative electrode current collector. In one embodiment, the negative electrode material may be formed only on one side of the negative electrode current collector. In another embodiment, the negative electrode material may be formed on both sides of the negative electrode current collector. In one embodiment, the negative electrode material may have a thickness of, for example, 10 μm to 200 μm.
[0037] In this invention, the negative electrode material contains a negative electrode active material. In one embodiment, the negative electrode material may consist essentially only of the negative electrode active material, or it may contain optional components. In a specific embodiment, the negative electrode active material may, for example, contain materials selected from graphite (e.g., artificial graphite), soft carbon, hard carbon, silicon-carbon materials (e.g., silicon-carbon composites), elemental silicon, and SiO. xOne or more of the following, preferably graphite (e.g., artificial graphite) and silicon-carbon materials (e.g., silicon-carbon composites). The mass ratio of graphite (e.g., artificial graphite) to silicon-carbon materials (e.g., silicon-carbon composites) can be 1.5-10, for example, it can be 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5 or 10.0, or a subrange consisting of any values in these ranges.
[0038] In one embodiment, the negative electrode material may further comprise a binder that bonds the solids together. In one embodiment, the binder may comprise optional components. Examples of the binder are carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl methylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile-butadiene-styrene copolymer, phenolic resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyamide-imide, polyether-imide, polyethyl sulfone, polyacetal, polyphenylene ether, polybutylene terephthalate, ethylene-propylene-diene terephthalate (EPDM), sulfonated EPDM, fluorocarbon rubber, and various copolymers, preferably one or more of CMC, SBR, PVP, PAA, and PVDF. As a preferred, non-limiting example, the binder is CMC and SBR. In the negative electrode material, the amount of the binder can be, for example, from 0.1 wt% to 10 wt%.
[0039] In addition to the negative electrode active material, a suitable amount of conductive agent may be added to the negative electrode material to reduce the battery's internal resistance. In one embodiment, the conductive agent may contain optional components. In a specific embodiment, the conductive agent may be selected from one or more of superconducting carbon black (SP), carbon nanotubes (CNTs), conductive carbon black, carbon fibers, and graphite-based conductive agents. Preferably, the conductive agent in the negative electrode material includes SP and CNTs. As a further preferred embodiment, the CNT is a single-walled carbon nanotube (SWCNT).
[0040] In one embodiment, the conductive agent content in the negative electrode material is 1 wt% to 4 wt%. The SP content in the negative electrode material is 1 wt% to 4 wt%. The CNT content in the negative electrode material is 0.01 wt% to 0.12 wt%. The mass ratio of SP to CNT in the negative electrode material is 3 to 1500. Preferably, the mass ratio of superconducting carbon black to single-walled carbon nanotubes can be 3-30, for example, it can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30, or a subrange consisting of any values within these ranges.
[0041] In a preferred embodiment, the negative electrode includes a negative electrode active material, a conductive agent, and a binder.
[0042] In one embodiment, the negative electrode material can be formed by coating with a slurry containing a solvent. Examples of the solvent are N-methylpyrrolidone (NMP), cyclohexanone, water, toluene, and xylene, but this disclosure is not limited thereto. Preferably, the solvent used for the negative electrode material is water (e.g., deionized water).
[0043] In one embodiment, the negative electrode of the lithium-ion battery includes a negative electrode current collector and a negative electrode material coated on the negative electrode current collector, wherein the compaction density of the negative electrode material is 1.3-1.7 g / cm³. 3 For example, the compaction density of the negative electrode material can be 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, or 1.7 g / cm³. 3 , or a subrange consisting of any values within these ranges.
[0044] In one embodiment, the single-sided coating weight of the negative electrode material on the negative electrode current collector is 3.5-6.5 mg / cm³. 2 For example, the single-sided coating weight of the negative electrode material on the negative electrode current collector can be 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, or 6.5 mg / cm³. 2 , or a subrange consisting of any values within these ranges.
[0045] In one embodiment, the thickness of the single-sided negative electrode material is 20-50 μm. For example, the thickness of the single-sided electrode of the negative electrode can be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 μm, or a subrange consisting of any values within these ranges.
[0046] In one embodiment, the diffusion resistance of the negative electrode is 2.5-4 Ω*cm. 2 For example, the diffusion resistance of the negative electrode can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4.0 Ω*cm. 2 , or a subrange consisting of any values within these ranges.
[0047] In one embodiment, the diffusion resistivity of the negative electrode is 500-1500 Ω*cm. For example, the diffusion resistivity of the negative electrode can be 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1150, 1200, 1250, 1300, 1350, 1400, 1450 or 1500 Ω*cm, or a subrange consisting of any values within these ranges.
[0048] In one embodiment, the capacitance of the negative electrode is 7-12 mF. For example, the capacitance of the negative electrode can be 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5 or 12 mF, or a subrange consisting of any values within these ranges.
[0049] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a casing, wherein the negative electrode is the negative electrode of the lithium-ion battery as described above.
[0050] The positive electrode is, for example, sheet-like and includes a positive current collector and a positive electrode material.
[0051] In one embodiment, the positive current collector may have a thickness of, for example, 5 μm to 50 μm.
[0052] In one embodiment, the positive current collector is an aluminum foil.
[0053] In this invention, the positive electrode material is formed on the surface of the positive electrode current collector. In one embodiment, the positive electrode material may be formed only on one side of the positive electrode current collector. In another embodiment, the positive electrode material may be formed on both sides of the positive electrode current collector. In one embodiment, the positive electrode material may have a thickness of, for example, 10 μm to 200 μm.
[0054] In this invention, the cathode material contains a cathode active material. In one embodiment, the cathode material may consist essentially only of the cathode active material, or it may contain optional components. In a specific embodiment, the cathode active material may, for example, contain one or more selected from lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, and lithium iron phosphate, preferably lithium nickel cobalt manganese oxide (including single crystal and polycrystalline).
[0055] In one embodiment, the positive electrode material may further comprise a binder that bonds the solids together. In one embodiment, the binder may comprise optional components. Examples of the binder are carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl methylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile-butadiene-styrene copolymer, phenolic resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyamide-imide, polyether-imide, polyethyl sulfone, polyacetal, polyphenylene ether, polybutylene terephthalate, ethylene-propylene-diene terephthalate (EPDM), sulfonated EPDM, fluorocarbon rubber, and various copolymers, preferably one or more of CMC, SBR, PVP, and PVDF. As a preferred, non-limiting example, the binder is PVDF. In the cathode material, the amount of the binder can be, for example, from 0.1 wt% to 10 wt%.
[0056] In addition to the positive electrode active material, a suitable amount of conductive agent can be added to the positive electrode material to reduce the battery's internal resistance. In one embodiment, the conductive agent may contain optional components. In a specific embodiment, the conductive agent may be selected from one or more of superconducting carbon black (SP), carbon nanotubes (CNTs), conductive carbon black, carbon fibers, and graphite-based conductive agents. Preferably, the conductive agent is SP.
[0057] In one embodiment, the content of the conductive agent in the positive electrode material is from 0.1 wt% to 3 wt%.
[0058] In one embodiment, the cathode material can be formed by coating with a slurry containing a solvent. Examples of the solvent are N-methylpyrrolidone (NMP), cyclohexanone, water, toluene, and xylene, but this disclosure is not limited thereto. Preferably, the solvent used for the cathode material is NMP.
[0059] In one embodiment, the electrolyte may be, for example, an organic electrolyte. The organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. The organic solvent may be any suitable material that can be used as an organic solvent. Examples of such organic solvents are ethylene carbonate, ethylene ethyl carbonate, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzyl nitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or combinations thereof. The lithium salt may be any lithium salt commonly used in the art. For example, the lithium salts mentioned are LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x +1SO2)(C y F 2y +1SO2 (where x and y are natural numbers), LiCl, LiI, or any mixture thereof.
[0060] In addition to the organic electrolytes mentioned above, other exemplary electrolytes further include non-aqueous electrolytes, organic solid electrolytes, and inorganic solid electrolytes. Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, PVDF, and polymers including ionic dissociative groups. Examples of inorganic solid electrolytes are nitride solid electrolytes, oxynitride solid electrolytes, and sulfide solid electrolytes. Examples of inorganic solid electrolytes are Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, and Li3PO4-Li2S-SiS2. Specific Implementation
[0062] The following examples describe several embodiments of the present invention, which are illustrative of the invention and not intended to limit the invention thereto.
[0063] Example 1
[0064] Lithium batteries are manufactured using the following method:
[0065] (1) Preparation of the positive electrode sheet: Single-crystal and polycrystalline lithium nickel cobalt manganese oxide, superconducting carbon black, and PVDF were added to NMP and mixed evenly to prepare a slurry. The positive electrode slurry was uniformly coated on one surface of a 15μm thick aluminum foil for the positive electrode current collector. The NMP was removed by drying at 100℃ to obtain a positive electrode sheet with a single-sided coating of positive electrode material. Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode material. After rolling and slitting, a positive electrode sheet with a specification of 59.5mm×1450mm was obtained. The single-sided coating weight of the positive electrode material was 16mg / cm³. 2 The compacted density is 3.4 g / cm³. 3 .
[0066] (2) Preparation of the negative electrode sheet: Graphite, silicon carbide, superconducting carbon black, single-walled carbon nanotubes, CMC, SBR, and deionized water were mixed evenly to prepare a negative electrode slurry. The negative electrode slurry was then coated onto one surface of an 8μm thick copper foil used as a negative electrode current collector. After drying at 70℃, the solvent was removed, resulting in a negative electrode sheet with a single-sided coating of the negative electrode material. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of the negative electrode material. After rolling and slitting, a positive electrode sheet with dimensions of 62.5mm × 1500mm was obtained. The single-sided coating weight of the negative electrode material was 5.07 mg / cm². 2 The compacted density is 1.40 g / cm³. 3 The thickness of the single-sided negative electrode material is 37.5 μm; the diffusion resistance of the negative electrode is 3 Ω*cm. 2 The diffusion resistivity of the negative electrode is 787.5 Ω*cm, and the capacitance of the negative electrode is 9.8 mF.
[0067] (3) The positive electrode, negative electrode and ceramic separator (PE+Al2O3) are assembled into a cylindrical core by winding, the busbar is welded, the steel shell is rolled into a groove, the moisture is removed by baking at 80°C for 24 hours, the electrolyte is injected, and the lithium battery is obtained by forming through a suitable formation process.
[0068] Example 2
[0069] The lithium battery was fabricated using the method described in Example 1, but the following parameters were used to prepare the negative electrode sheet: the single-sided coating weight of the negative electrode material was 4.57 mg / cm². 2 The compacted density is 1.50 g / cm³. 3 The thickness of the single-sided negative electrode material is 31.5 μm; the diffusion resistance of the negative electrode is 3.1 Ω*cm. 2The diffusion resistivity of the negative electrode is 990.5 Ω*cm, and the capacitance of the negative electrode is 10.7 mF.
[0070] Example 3
[0071] The lithium battery was fabricated using the method described in Example 1, but the following parameters were used to prepare the negative electrode sheet: the single-sided coating weight of the negative electrode material was 4.20 mg / cm². 2 The compacted density is 1.60 g / cm³. 3 The thickness of the single-sided negative electrode material is 28.0 μm; the diffusion resistance of the negative electrode is 3.4 Ω*cm. 2 The diffusion resistivity of the negative electrode is 1198.6 Ω*cm, and the capacitance of the negative electrode is 10.2 mF.
[0072] The negative electrode parameter information for Examples 1-3 is shown in Table 1 below.
[0073] Table 1. Negative electrode parameters of Examples 1-3
[0074]
[0075]
[0076] Test Example 1: 30-day storage test at 60℃
[0077] The lithium batteries prepared in Examples 1-3 were subjected to a storage test at 60°C.
[0078] Each embodiment was tested 6 times, and the specific testing method is as follows:
[0079] 1. Perform a capacity calibration test on the battery before storage: Charge the battery to 4.2V using a constant current and constant voltage of 0.8A, with the constant voltage cutoff current being 100mA. After resting for 30 minutes, discharge the battery to 2.5V using a constant current of 0.8A. The discharge capacity at this point is the battery's standard capacity. The charging and discharging equipment used is the Xinwei CT-4032 battery charging and discharging testing equipment.
[0080] 2. Pre-charge process: Charge the storage battery to 4.2V using a constant current and constant voltage of 6A, with the constant voltage cutoff current condition being 100mA.
[0081] 3. Measure the battery's open-circuit voltage (OCV) and internal resistance: After pre-charging, let the battery rest for 6 hours to remove polarization, then measure and record the battery's open-circuit voltage and internal resistance.
[0082] 4. 60℃ Storage: Place the battery in a temperature chamber at 60℃. To ensure uniform temperature, the battery cells must not be in contact with the inner wall of the chamber or the support frame. The temperature chamber is a battery aging explosion-proof chamber GK-GW600-200 from Dongguan Guangbo Testing Equipment Co., Ltd., with a temperature uniformity of 60℃±1.
[0083] 5. Measure the battery voltage regularly for 30 consecutive days.
[0084] 6. After 30 days, record the battery's open-circuit voltage and internal resistance, and perform a capacity test on the stored battery: charge it to 4.2V using a constant current and constant voltage of 0.8A, with the constant voltage cutoff current condition being 100mA. After resting for 30 minutes, discharge it to 2.5V using a constant current of 0.8A. The discharge capacity at this point is the battery's retain capacity after storage. Self-discharge current = (standard capacity - retain capacity) / time (hours).
[0085] 7. Charge the battery with the measured retained capacity again to 4.2V using a constant current and constant voltage of 0.8A, with the constant voltage cutoff current condition being 100mA. After resting for 30 minutes, discharge it to 2.5V using a constant current of 0.8A. The discharge capacity at this point is the battery's recovery capacity after storage.
[0086] The test results are shown in Table 2-4 below.
[0087] Table 2 Data before testing in Examples 1-3
[0088]
[0089] *ACIR (Alternating Current Internal Resistance), also known as alternating current internal resistance, is the same below.
[0090] **DCIR (Direct Current Internal Resistance), also known as DC internal resistance, is the same below.
[0091] Table 3 Data after tests in Examples 1-3
[0092]
[0093]
[0094] Table 4. Final results of 60°C storage tests before and after Examples 1-3.
[0095]
[0096]
[0097] *Retained Capacity = Retained Capacity / Standard Capacity * 100%.
[0098] **Recovered Capacity = Recovered Capacity / Standard Capacity * 100%.
[0099] ***Capacity change (ΔC) = Standard capacity - Reserved capacity.
[0100] ****Self-discharge current = (standard capacity - reserved capacity) / time (hours), where the time is 720 hours, or 30 days.
[0101] Figure 1 The specific details of the retention capacity rates of Examples 1-3 are described. It can be seen that the retention capacity rate generally decreases sequentially from Example 1 to Example 3, that is, the retention capacity rate of Example 1 is better than that of Example 2, and the retention capacity rate of Example 2 is better than that of Example 3.
[0102] Figure 2 The self-discharge current of Examples 1-3 is described. It can be seen that the self-discharge current generally increases sequentially from Example 1 to Example 3, that is, the self-discharge current of Example 1 is lower than that of Example 2, and the self-discharge current of Example 2 is lower than that of Example 3.
[0103] Figure 3 This reflects the relationship between the compaction density of the negative electrode material, the negative electrode capacitance, and the self-discharge current in Examples 1-3, where the self-discharge current is taken as the average of 6 repeated sets. It can be seen that there is a positive correlation between the compaction density of the negative electrode material and both the negative electrode capacitance and the self-discharge current; that is, as the compaction density of the negative electrode material increases, both the negative electrode capacitance and the self-discharge current also increase, and the increase ratios of the negative electrode capacitance and the self-discharge current are similar.
[0104] The above description of various embodiments of the present invention is provided for illustrative purposes to a person skilled in the art. It is not intended to limit the invention to a single disclosed embodiment. As taught above, those skilled in the art will understand various alternatives and variations of the invention. Therefore, although some alternative embodiments have been specifically described, those skilled in the art will understand or relatively easily develop other embodiments. The present invention is intended to include all alternatives, modifications, and variations of the invention described herein, as well as other embodiments falling within the spirit and scope of the invention described above.
Claims
1. A negative electrode for a lithium-ion battery, comprising a negative electrode current collector and a negative electrode material coated on the negative electrode current collector, characterized in that, The compaction density of the negative electrode material is 1.3-1.7 g / cm³. 3 The single-sided coating weight of the negative electrode material on the negative electrode current collector is 3.5-6.5 mg / cm³. 2 Furthermore, the thickness of the single-sided negative electrode material is 20-50 μm.
2. The negative electrode according to claim 1, wherein, The compaction density of the negative electrode material is 1.3-1.6 g / cm³. 3 The single-sided coating weight of the negative electrode material on the negative electrode current collector is 4-6.5 mg / cm³. 2 Furthermore, the thickness of the single-sided negative electrode material is 25-45μm.
3. The negative electrode according to any one of the preceding claims, wherein, The compaction density of the negative electrode material is 1.4-1.5 g / cm³. 3 The single-sided coating weight of the negative electrode material on the negative electrode current collector is 4.5-5.1 mg / cm³. 2 Furthermore, the thickness of the single-sided negative electrode material is 32-38 μm.
4. The negative electrode according to any one of the preceding claims, wherein, The diffusion resistance of the negative electrode is 2.5-4 Ω*cm. 2 Preferably, the Ω*cm is 2.8-3.
8. 2 More preferably, it is 3.0-3.1Ω*cm. 2 .
5. The negative electrode according to any one of the preceding claims, wherein, The diffusion resistivity of the negative electrode is 500-1500 Ω*cm; preferably 700-1300 Ω*cm; more preferably 750-1000 Ω*cm.
6. The negative electrode according to any one of the preceding claims, wherein, The capacitance of the negative electrode is 7-12mF; preferably 8.5-11mF; more preferably 9.5-10.5mF.
7. The negative electrode according to any one of the preceding claims, wherein, The negative electrode includes a negative electrode active material, a conductive agent, and a binder.
8. The negative electrode according to claim 7, wherein, The conductive agent includes superconducting carbon black and single-walled carbon nanotubes.
9. The negative electrode according to claim 8, wherein, The mass ratio of the superconducting carbon black to the single-walled carbon nanotubes is between 3 and 30.
10. The negative electrode according to claim 7, wherein, The adhesive includes carboxymethyl cellulose and styrene-butadiene rubber.
11. The negative electrode according to claim 7, wherein, The active material includes artificial graphite and silicon carbide, with a mass ratio between 1.5 and 10.
12. A lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a casing, wherein the negative electrode is the negative electrode of the lithium-ion battery according to any one of claims 1-11.
13. The lithium-ion battery of claim 12, wherein the capacity retention rate is 83.2%-86% after a 30-day storage test at 60°C.
14. The lithium-ion battery of claim 13, wherein the capacity retention rate is 84%-85% after a 30-day storage test at 60°C.
15. The use of a negative electrode of a lithium-ion battery according to any one of claims 1-11 for reducing the self-discharge current of the lithium-ion battery.