WO2024011702A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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WO2024011702A1
WO2024011702A1 PCT/CN2022/112111 CN2022112111W WO2024011702A1 WO 2024011702 A1 WO2024011702 A1 WO 2024011702A1 CN 2022112111 W CN2022112111 W CN 2022112111W WO 2024011702 A1 WO2024011702 A1 WO 2024011702A1
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negative electrode
positive electrode
film
lithium
ion battery
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PCT/CN2022/112111
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English (en)
French (fr)
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田孟羽
黄学杰
闫勇
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松山湖材料实验室
中国科学院物理研究所
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Publication of WO2024011702A1 publication Critical patent/WO2024011702A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of battery manufacturing, specifically to a lithium-ion battery.
  • lithium-ion secondary batteries Compared with other rechargeable battery systems, lithium-ion secondary batteries have the advantages of high operating voltage, light weight, small size, no memory effect, low self-discharge rate, long cycle life and high energy density. They have been widely used in Mobile terminal products such as mobile phones, laptops or tablets, as well as electric vehicles and other fields.
  • the electrolyte is reduced on the surface of the negative electrode to form a negative SEI film.
  • the SEI film has the characteristics of ion conduction and electronic insulation, and is crucial to the normal operation of the lithium-ion battery.
  • the composition, integrity, stability, density, thickness, conductivity and other indicators of the SEI film on the surface of the negative electrode of a lithium-ion battery directly affect the transmission of lithium ions at the interface between the electrolyte and the negative electrode, thereby affecting the cycle performance of the lithium-ion battery.
  • Lithium iron phosphate or lithium manganate has the advantages of high capacity, low cost and good safety, and is the preferred material for the cathode active material in lithium-ion batteries.
  • lithium-ion batteries that use lithium iron phosphate or lithium manganate as the cathode active material it is common that the SEI film with a stable structure cannot be formed on the surface of the negative electrode, resulting in lithium-ion batteries that use lithium iron phosphate or lithium manganate as the cathode active material. There is a bottleneck in improving cycle performance.
  • the purpose of this application is to provide a lithium-ion battery that aims to improve the technical problem of bottlenecks in improving the cycle performance of existing lithium-ion batteries that use lithium iron phosphate or lithium manganate as the positive electrode active material.
  • This application provides a lithium-ion battery, including: a separator, a positive electrode piece, a negative electrode piece and an electrolyte.
  • the coating of the positive electrode piece includes positive electrode material; the positive electrode material includes positive electrode active material, conductive agent and binder, and the positive electrode active material includes at least one of lithium iron phosphate and lithium manganate.
  • the coating of the positive electrode piece further includes a negative electrode film-forming additive; and/or the electrolyte includes a negative electrode film-forming additive; and the negative electrode film-forming additive includes at least one of elemental sulfur and metal sulfide.
  • the electrolyte includes a film-forming solvent, and the structural formula of the film-forming solvent is as follows:
  • R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, a halogen atom, an alkyl group or a hydrocarbon group.
  • R 5 and R 6 are each independently a hydrogen atom, a halogen atom, an alkyl group or a hydrocarbon group.
  • the present application adds at least one of elemental sulfur and metal sulfide to the coating of the positive electrode sheet and/or the electrolyte.
  • the negative electrode film-forming additive can migrate to the negative electrode surface during the first week of charging of the lithium ion battery (that is, during the electrochemical reaction process inside the lithium ion battery) and participate in the formation of the SEI film on the negative electrode surface, which is beneficial to the SEI film on the negative electrode surface. It contains both high-valent sulfur components with a valence of +4 and/or +6 and low-valent sulfur components with a valence of -2 to -1/4.
  • the high-valence sulfur component can quickly transfer lithium ions and promote the transport of lithium ions at the interface.
  • the negative electrode film-forming additive is reduced to polysulfide at the negative electrode, and the polysulfide reacts with the film-forming solvent to generate a low-valent sulfur component with a PEO structure.
  • the PEO structure has good toughness and can effectively alleviate the volume deformation of the anode material during the charge and discharge process.
  • the presence of high-valence sulfur components and low-valence sulfur components is conducive to forming a stable SEI film on the surface of the negative electrode, reducing charge transfer resistance and polarization, improving battery cycle stability, and thereby improving the rate performance of lithium-ion batteries.
  • the metal sulfide may include lithium sulfide, iron sulfide, iron disulfide, titanium disulfide, titanium trisulfide, zinc sulfide, tin disulfide, molybdenum disulfide, tungsten disulfide, cobalt disulfide and at least one of nickel sulfide.
  • the alkyl group or the hydrocarbyl group may be a substituted alkyl group or a substituted hydrocarbyl group.
  • the alkyl group can be methyl, ethyl or butyl; the hydrocarbyl group can be vinyl, propenyl or butenyl.
  • the mass ratio of the negative electrode film-forming additive to the positive electrode active material may be (0.1-10):100.
  • the amount of negative electrode film-forming additive meets the above conditions, it will help further reduce the charge transfer resistance and increase the cycle capacity, thereby improving the cycle performance of the battery.
  • the mass ratio of the negative electrode film-forming additive to the positive electrode active material may be (0.1-3):100.
  • the mass concentration of the negative electrode film-forming additive in the electrolyte may be 0.01-10 g/L.
  • the amount of the negative electrode film-forming additive meets the above conditions, it will help further reduce the charge transfer resistance and increase the cycle capacity, thereby improving the cycle performance of the battery.
  • the mass concentration of the negative electrode film-forming additive in the electrolyte solution may be 0.05-1g/L.
  • the preparation method of the positive electrode sheet may include: combining the negative electrode film-forming additive, the positive electrode active material, the conductive agent and the binder. After the mixed slurry is coated on the positive electrode foil, it is heat treated at 80-160°C for 4-12 hours.
  • the above heat treatment conditions are conducive to improving the uniformity of the mixed slurry on the surface of the positive electrode foil, which is conducive to further improving the cycle performance of the battery.
  • the preparation method of the positive electrode sheet may include: using a gas phase method or a liquid phase method to disperse the negative electrode film forming additive in a liquid or gas , and then evenly deposited on the surface of the positive electrode piece.
  • the preparation method of the positive electrode sheet may include: dissolving sublimated sulfur powder in carbon disulfide, and coating the carbon disulfide containing elemental sulfur on the The surface of the positive electrode piece is then dried.
  • the coating of the negative electrode sheet may include a negative active material
  • the negative active material may include at least one of carbon-based materials, silicon-based materials, alloys, and lithium.
  • the selection of the above-mentioned substances as the negative electrode active material is conducive to the formation of a stable SEI film on the surface of the negative electrode.
  • the negative active material may include graphite, silicon carbon 450, or silicon.
  • the film-forming solvent may include at least one of ethylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate, and butylene carbonate.
  • the film-forming solvent includes the above substances, which can react with the polysulfide formed by the reduction of the negative electrode film-forming additive at the negative electrode to generate a low-valent sulfur component with a PEO structure, further improving the stability of the battery cycle and thereby improving the lithium-ion battery. rate performance.
  • the film-forming solvent may account for 1-100% of the total solvent mass in the electrolyte.
  • the film-forming solvent accounts for 1-100% of the total solvent mass in the electrolyte, which can effectively improve the stability of battery cycles.
  • the film-forming solvent may account for 5-40% of the total solvent mass in the electrolyte.
  • the particle size D 50 of the negative electrode film-forming additive may be 0.01-20 ⁇ m.
  • the particle size D 50 of the negative electrode film-forming additive is within the above range, which is beneficial to further improving the stability of the battery cycle.
  • the particle size D 50 of the negative electrode film-forming additive may be 0.05-5 ⁇ m.
  • the surface electrolyte interface film of the negative electrode sheet contains high-valence sulfur components and low-valence sulfur components; in the surface electrolyte interface film of the negative electrode sheet, the high-valence sulfur component The valence state of sulfur is +4 and/or +6, and the S2p spectrum peak is 168-172eV; in the surface electrolyte interface film of the negative electrode piece, the valence state of the low-valence sulfur component is -2 to -1/4. , S2p spectrum peak is 160-166eV.
  • the ratio of the S2p spectrum peak area of the high-valence sulfur component to the S2p spectrum peak area of the low-valence sulfur component can be (1-4):1;
  • the surface electrolyte interface film of the positive electrode piece can contain a high-valence sulfur component; in the surface electrolyte interface film of the positive electrode piece, the valence state of the high-valence sulfur component can be +4 and / Or +6 valence, the S2p spectrum peak can be 168-172eV.
  • Figure 1 shows the X-ray photoelectron spectrum test S2p spectrum of the negative electrode of the lithium-ion battery prepared in Example 1.
  • Figure 2 shows the X-ray photoelectron spectroscopy test S2p spectrum of the positive electrode of the lithium-ion battery prepared in Example 1.
  • Figure 3 shows the first-week charging test curve of the lithium-ion batteries prepared in Example 1 and Comparative Example 1.
  • Figure 4 shows the 100-cycle cycle performance diagram of the lithium-ion batteries prepared in Example 1 and Comparative Example 1.
  • Figure 5 shows the battery rate diagram of the lithium ion batteries produced in Example 1 and Comparative Example 1.
  • Figure 6 shows the battery impedance diagram of the lithium ion batteries produced in Example 1 and Comparative Example 1.
  • lithium-ion batteries that use lithium iron phosphate or lithium manganate as the cathode active material it is common that a stable SEI film cannot be formed on the surface of the negative electrode, resulting in a cycle of lithium-ion batteries that use lithium iron phosphate or lithium manganate as the cathode active material. There is a bottleneck in improving performance.
  • this application provides a lithium-ion battery, including: a separator, a positive electrode piece, a negative electrode piece, and an electrolyte.
  • the coating of the positive electrode piece includes positive electrode material; the positive electrode material includes positive electrode active material, conductive agent and binder, and the positive electrode active material includes at least one of lithium iron phosphate and lithium manganate.
  • the coating of the positive electrode piece further includes a negative electrode film-forming additive; and/or the electrolyte includes a negative electrode film-forming additive; and the negative electrode film-forming additive includes at least one of elemental sulfur and metal sulfide.
  • the electrolyte includes a film-forming solvent, and the structural formula of the film-forming solvent is as follows:
  • R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, a halogen atom, an alkyl group or a hydrocarbon group.
  • R 5 and R 6 are each independently a hydrogen atom, a halogen atom, an alkyl group or a hydrocarbon group.
  • the positive active material may include both lithium iron phosphate and lithium manganate, or may only include lithium iron phosphate, or only lithium manganate.
  • the negative electrode film-forming additive can use both elemental sulfur and metal sulfide, or only elemental sulfur, or only metal sulfide.
  • the coating of the positive electrode piece and the electrolyte may contain the negative electrode film-forming additive defined in this application at the same time, or only the coating of the positive electrode piece may contain the negative electrode film-forming additive defined in this application, or only the electrolyte may contain it. Contains negative electrode film-forming additives defined in this application.
  • the film-forming additive includes at least one of elemental sulfur and metal sulfide.
  • the function of the film-forming additive is to effectively improve the stability of the negative electrode SEI film.
  • the present application adds elements including elemental sulfur and metal sulfide to the coating of the positive electrode sheet and/or the electrolyte.
  • At least one negative electrode film-forming additive can migrate to the negative electrode surface during the first week of charging of the lithium-ion battery (i.e., during the electrochemical reaction process inside the lithium-ion battery) and participate in the formation of the SEI film on the negative electrode surface, which is beneficial to making the negative electrode
  • the surface SEI film contains both high-valence sulfur components with a valence of +4 and/or +6 and low-valence sulfur components with a valence of -2 to -1/4.
  • the high-valence sulfur component can quickly transfer lithium ions and promote the transport of lithium ions at the interface.
  • the negative electrode film-forming additive is reduced to polysulfide at the negative electrode, and the polysulfide reacts with the film-forming solvent defined in this application to generate a low-valent sulfur component with a PEO structure.
  • the PEO structure has good toughness and can effectively alleviate the volume deformation of the anode material during the charge and discharge process; the first-week charging curve of the lithium-ion battery can observe reaction platforms at 1-1.3V and 1.6-2V.
  • the metal sulfide when a metal sulfide is selected as the negative electrode film-forming additive, the metal sulfide can be selected from lithium sulfide, iron sulfide, iron disulfide, titanium disulfide, titanium trisulfide, zinc sulfide, tin disulfide, and molybdenum disulfide. , at least one of tungsten disulfide, cobalt disulfide and nickel sulfide.
  • metal sulfide does not need to be limited to the above-mentioned substances.
  • the negative electrode film-forming additive when the negative electrode film-forming additive is selected from elemental sulfur, compared with the negative electrode film-forming additive being selected from metal sulfides, it is beneficial to further improve the cycle performance of the battery.
  • the particle size D 50 of the negative electrode film-forming additive is 0.01-20 ⁇ m.
  • the particle size D 50 of the negative electrode film-forming additive is within the above range, which is beneficial to further improving the stability of the battery cycle.
  • the particle size D 50 of the negative electrode film-forming additive may be 0.01 ⁇ m, 0.05 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m or 20 ⁇ m, etc.
  • the particle size D 50 of the negative electrode film-forming additive can be 0.05-5 ⁇ m.
  • the particle size D 50 of the negative electrode film-forming additive is within the above particle size range, which is better for improving battery cycle stability.
  • the mass ratio of the negative electrode film-forming additive to the positive electrode active material is (0.1-10):100.
  • the amount of the negative electrode film-forming additive meets the above conditions, it will help further reduce the charge transfer resistance and increase the cycle capacity, thereby improving the cycle performance of the battery.
  • the mass ratio of the negative electrode film-forming additive to the positive electrode active material may be 0.1:100, 1:100, 2:100, 5:100, or 10: 100 and so on.
  • the coating of the positive electrode plate includes a negative electrode film-forming additive
  • the mass ratio of the negative electrode film-forming additive to the positive electrode active material is (0.1-3):100; under the above ratio conditions, it is beneficial to further improve the performance of the battery. Cycle performance.
  • the preparation method of the positive electrode piece includes: applying a mixed slurry containing the negative electrode film-forming additive, the positive electrode active material, the conductive agent and the binder to After removing the positive electrode foil, heat treat it at 80-160°C for 4-12 hours.
  • the above heat treatment conditions are conducive to improving the uniformity of the mixed slurry on the surface of the positive electrode foil, which is conducive to further improving the cycle performance of the battery.
  • the temperature of the heat treatment can be 80°C, 100°C, 120°C, 140°C or 160°C, etc.
  • the time of the heat treatment can be 4h, 5h, 8h, 10h or 12h, etc.
  • this application does not limit the order of adding the negative electrode film-forming additive, positive electrode active material, conductive agent and binder in the mixed slurry.
  • the preparation method of the positive electrode piece can also use a gas phase method or a liquid phase method to disperse the negative electrode film-forming additive in a liquid or gas, and then Evenly deposited on the surface of the positive electrode piece.
  • the preparation method of the positive electrode sheet can also be as follows: dissolving sublimated sulfur powder in carbon disulfide, coating the carbon disulfide containing elemental sulfur on the surface of the positive electrode sheet and then drying.
  • the mass concentration of the negative electrode film-forming additive in the electrolyte is 0.01-10g/L.
  • the amount of the negative electrode film-forming additive meets the above conditions, it will help further reduce the charge transfer resistance and increase the cycle capacity, thereby improving the cycle performance of the battery.
  • the mass concentration of the negative electrode film-forming additive in the electrolyte can be 0.01g/L, 0.05g/L, 0.5g/L, 1.0g/L, 2.0g /L, 5.0g/L or 10g/L, etc.
  • the mass concentration of the negative electrode film-forming additive in the electrolyte solution may be 0.05-1g/L.
  • the structure of the film-forming solvent contains cyclic carbonate
  • R 1 , R 2 , R 3 and R 4 in the structural formula of the film-forming solvent are each independently a hydrogen atom, a halogen atom, an alkyl group or a hydrocarbon group.
  • the alkyl group or hydrocarbon group can be a substituted alkyl group or a substituted hydrocarbon group, for example, a haloalkyl group or a halohydrocarbyl group; the alkyl group can also be methyl, ethyl or butyl, etc.; the hydrocarbon group can be vinyl, propenyl or butene. Key et al.
  • the film-forming solvent may be selected from ethylene carbonate (EC), fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), vinylene carbonate (VC), and butylene carbonate ( BC) at least one.
  • the film-forming solvent includes the above substances, which can react with the polysulfide formed by the reduction of the negative electrode film-forming additive at the negative electrode to generate a low-valent sulfur component with a PEO structure, further improving the stability of the battery cycle and thereby improving the lithium-ion battery. rate performance.
  • film-forming solvent is not limited to the above-mentioned substances, as long as it can satisfy the structural formula of the solvent defined in this application.
  • the film-forming solvent accounts for 1-100% of the total solvent mass in the electrolyte, which can effectively improve the stability of the battery cycle.
  • the mass fraction of the film-forming solvent in the total solvent in the electrolyte can be 1%, 5%, 10%, 30%, 50% or 100%, etc.
  • the film-forming solvent can account for 5-40% of the total solvent in the electrolyte, which is beneficial to further improving the stability of the battery cycle.
  • the positive electrode active material is selected from lithium iron phosphate
  • the coating of the negative electrode piece includes a negative active material
  • the negative active material includes at least one of carbon-based materials, silicon-based materials, alloys, and lithium.
  • the negative active material may include graphite, silicon carbon 450, silicon, or the like.
  • the negative active material is selected from graphite, it is beneficial to further improve the cycle performance of the battery.
  • the surface electrolyte interface film (SEI film) of the negative electrode sheet contains high-valence sulfur components and low-valence sulfur components; in the surface electrolyte interface film (SEI film) of the negative electrode sheet, The valence state of the high-valence sulfur component is +4 and/or +6, and the S2p spectrum peak is 168-172eV; in the surface electrolyte interface film (SEI film) of the negative electrode plate, the valence state of the low-valence sulfur component is - From 2 valence to -1/4 valence, the S2p spectrum peak is 160-166eV.
  • the ratio of the S2p spectrum peak area of the high-valence sulfur component to the S2p spectrum peak area of the low-valence sulfur component can be (1-4):1, with It is beneficial to further improve the cycle performance of the battery.
  • the surface electrolyte interface film (CEI film) of the positive electrode sheet contains a high-valence sulfur component; in the surface electrolyte interface film (CEI film) of the positive electrode sheet, the high-valence sulfur component
  • the state is +4 valence and/or +6 valence, and the S2p spectrum peak is 168-172eV.
  • This embodiment provides a lithium-ion battery, which is produced by the following method:
  • Negative electrode mixed slurry (2) Stir 9.4g graphite, 0.3g conductive carbon black (SP), 0.15g sodium carboxymethylcellulose (CMC), 0.15g styrene-butadiene rubber (SBR) and 25mL deionized water to obtain Negative electrode mixed slurry.
  • the negative electrode mixed slurry is evenly coated on the Cu foil, and the negative electrode sheet is obtained after drying and rolling.
  • step (3) Place the separator between the positive electrode piece obtained in step (1) and the negative electrode piece obtained in step (2), inject 120uL electrolyte, place the gasket and spring piece, and place it in a press to seal to form a lithium-ion battery .
  • This embodiment provides a lithium-ion battery, which is produced by the following method:
  • Negative electrode mixed slurry (2) Stir 9.4g graphite, 0.3g conductive carbon black (SP), 0.15g sodium carboxymethylcellulose (CMC), 0.15g styrene-butadiene rubber (SBR) and 25mL deionized water to obtain Negative electrode mixed slurry.
  • the negative electrode mixed slurry is evenly coated on the Cu foil, and the negative electrode sheet is obtained after drying and rolling.
  • step (3) Place the separator between the positive electrode piece obtained in step (1) and the negative electrode piece obtained in step (2), inject 120uL of the final electrolyte, place the gasket and shrapnel, and place it in a press to seal it to form lithium ions Battery.
  • This embodiment provides a lithium-ion battery.
  • the difference between this embodiment and Embodiment 1 is that the mass of elemental sulfur in step (1) is different.
  • the mass of elemental sulfur is 0.01g.
  • This embodiment provides a lithium-ion battery.
  • the difference between this embodiment and Embodiment 1 is that the mass of elemental sulfur in step (1) is different.
  • the mass of elemental sulfur is 0.5g.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that the graphite in step (2) is replaced by silicon carbon 450.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that the graphite in step (2) is replaced with silicon.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that LiFePO 4 in step (1) is replaced by LiMnO 2 .
  • This embodiment provides a lithium-ion battery.
  • the difference between this embodiment and Embodiment 1 is that the elemental sulfur powder in step (1) is replaced by lithium sulfide.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that the elemental sulfur powder in step (1) is replaced with titanium disulfide.
  • This embodiment provides a lithium-ion battery.
  • the difference between this embodiment and Embodiment 1 is that the elemental sulfur powder in step (1) is replaced with molybdenum disulfide.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that the ethylene carbonate (EC) in step (3) is replaced by bisfluoroethylene carbonate (DFEC).
  • EC ethylene carbonate
  • DFEC bisfluoroethylene carbonate
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 is that the ethylene carbonate (EC) in step (3) is replaced by vinylene carbonate (VC).
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 lies in the difference in the electrolyte in step (3).
  • the electrolyte is 1.0MLiPF 6 inEC.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 1 lies in the difference in the electrolyte in step (3).
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 2 lies in the concentration of elemental sulfur in the electrolyte in step (3).
  • the concentration of elemental sulfur in the electrolyte is 0.01 mg/ mL.
  • This embodiment provides a lithium ion battery.
  • the difference between this embodiment and Embodiment 2 lies in the concentration of elemental sulfur in the electrolyte in step (3).
  • the concentration of elemental sulfur in the electrolyte is 2.0 mg/ mL.
  • This comparative example provides a lithium ion battery.
  • the difference between this comparative example and Example 1 lies in step (1).
  • Step (1) of this comparative example is as follows:
  • This comparative example provides a lithium ion battery.
  • the difference between this comparative example and Example 1 lies in the difference in the electrolyte in step (3).
  • the X-ray photoelectron spectrum S2p spectrum of the negative electrode after the formation of the lithium ion battery prepared in Example 1 has a characteristic peak corresponding to the high-valence sulfur component at 168-172 eV, and a characteristic peak corresponding to the high-valence sulfur component at 160-166 eV.
  • Characteristic peaks of low-valent sulfur components indicating that after the lithium-ion battery prepared in Example 1 is formed, elemental sulfur (negative electrode film-forming additive) reacts to simultaneously generate +4-valent and/or +6-valent high valence in the SEI film on the negative electrode surface.
  • sulfur components and low-valent sulfur components ranging from -2 to -1/4.
  • High-valence sulfur is due to the oxidation reaction of sulfur at the positive electrode, forming a component similar to R-OSO2OLi and diffusing to the negative electrode, which can quickly transport Li ions and reduce the interface impedance; the existence of low-valence sulfur components is speculated to be because Elemental sulfur (negative electrode film-forming additive) is reduced to polysulfide at the negative electrode, and the polysulfide reacts with ethylene carbonate (EC) to form an SEI film with a PEO structure.
  • Elemental sulfur negative electrode film-forming additive
  • EC ethylene carbonate
  • the X-ray photoelectron spectrum S2p spectrum of the cathode after the formation of the lithium ion battery prepared in Example 1 has a characteristic peak corresponding to the high valence sulfur component at 168-172 eV; indicating that the lithium ion battery prepared in Example 1 After the lithium-ion battery is formed, elemental sulfur (negative electrode film-forming additive) reacts to generate +4-valent and/or +6-valent high-valence sulfur components in the CEI film on the surface of the positive electrode.
  • Example 1 The lithium-ion batteries prepared in Example 1 and Comparative Example 1 were respectively subjected to a battery first-week charging test, a 100-cycle cycle performance test, a battery rate test and a battery impedance test.
  • the comparative experimental results are shown in Figures 3, 4, 5 and 5, respectively. As shown in Figure 6.
  • Part a in Figure 3 is the cycle performance diagram with the abscissa battery capacity (Capacity) in the range of 0-180mAh ⁇ g -1
  • part b in Figure 3 is the abscissa battery capacity (Capacity) in the range of 0-1.5mAh ⁇ g -1 Cycling performance plot within intervals.
  • the lithium-ion batteries provided in Examples 1-17 and Comparative Examples 1-2 were respectively subjected to impedance tests after 10 cycles and battery capacity tests after 100 cycles. The experimental results are shown in Table 1.
  • the impedance of the lithium-ion battery provided in Examples 1-16 after 10 cycles is significantly lower than the impedance of the lithium-ion battery provided in Comparative Examples 1-2 after 10 cycles.
  • the battery capacity of the lithium-ion battery after 100 cycles is significantly higher than the impedance after 10 cycles of the lithium-ion battery provided in Comparative Examples 1-2, indicating that the negative electrode film-forming additive defined in this application is added to the coating or electrolyte of the positive electrode piece. And adding the film-forming solvent defined in this application to the electrolyte can effectively improve the cycle performance of lithium-ion batteries.
  • Example 1 From the comparison between Examples 3-14 and Example 1, it can be seen that when the coating of the positive electrode piece includes a negative electrode film-forming additive, the mass ratio of the negative electrode film-forming additive to the positive electrode active material, the selection of the negative electrode active material, and the The selection, selection of negative electrode film-forming additives, selection of film-forming solvent, and mass fraction of the film-forming solvent in the electrolyte can further affect the cycle performance of lithium-ion batteries.
  • the lithium-ion battery provided by this application can effectively improve the cycle performance of the lithium-ion battery using lithium iron phosphate or lithium manganate as the cathode active material.
  • the present application provides a lithium-ion battery.
  • lithium iron phosphate and/or lithium manganate are used as the positive active material to prepare the lithium-ion battery
  • the present application adds elements including elements to the coating of the positive electrode plate and/or the electrolyte.
  • the negative electrode film-forming additive of at least one of sulfur and metal sulfide can migrate to the negative electrode surface during the first week of charging of the lithium ion battery (i.e., during the electrochemical reaction inside the lithium ion battery) and participate in the SEI film on the negative electrode surface.
  • the formation of is conducive to making the SEI film on the surface of the negative electrode contain both high-valence sulfur components with a valence of +4 and/or +6 and low-valence sulfur components with a valence of -2 to -1/4.
  • the high-valence sulfur component can quickly transfer lithium ions and promote the transport of lithium ions at the interface.
  • the negative electrode film-forming additive is reduced to polysulfide at the negative electrode, and the polysulfide reacts with the film-forming solvent to generate a low-valent sulfur component with a PEO structure.
  • the PEO structure has good toughness and can effectively alleviate the volume deformation of the anode material during the charge and discharge process.
  • the presence of high-valence sulfur components and low-valence sulfur components is conducive to forming a stable SEI film on the surface of the negative electrode, reducing charge transfer resistance and polarization, improving battery cycle stability, and thereby improving the rate performance of lithium-ion batteries.
  • the lithium-ion batteries of the present application are reproducible and can be used in a variety of industrial applications.
  • the lithium-ion battery of the present application can be used in the technical field of battery manufacturing.

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Abstract

本申请涉及电池制造技术领域，具体而言，涉及一种锂离子电池。锂离子电池包括：隔膜、正极极片、负极极片以及电解液。其中，正极极片的涂层包括正极材料；正极材料包括正极活性材料、导电剂以及粘结剂，正极活性材料包括磷酸铁锂以及锰酸锂中的至少一种。正极极片的涂层还包括负极成膜添加剂；和/或，电解液包括负极成膜添加剂；负极成膜添加剂包括单质硫以及金属硫化物中的至少一种。电解液包括成膜溶剂。本申请提供的锂离子电池可以有效提高采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池的循环性能。

Description

一种锂离子电池
相关申请的交叉引用
本申请要求于2022年07月14日提交中国国家知识产权局的申请号为202210832434.2、名称为“一种锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电池制造技术领域，具体而言，涉及一种锂离子电池。
背景技术
锂离子二次电池与其它的可充电的电池体系相比，具有工作电压高、重量轻、体积小、无记忆效应、自放电率低、循环寿命长以及能量密度高等优点，目前已广泛应用于手机、笔记本电脑或平板电脑等移动终端产品以及电动汽车等领域。
锂离子电池首周充电过程中，电解质在负极表面被还原生成负极SEI膜，SEI膜具有离子导通电子绝缘的特性，对锂离子电池的正常工作至关重要。锂离子电池负极表面SEI膜的成分、完整性、稳定性、致密度、厚度以及电导率等指标，直接影响着锂离子在电解液和负极界面处的传输，进而影响锂离子电池的循环性能。
磷酸铁锂或锰酸锂具有高容量、低成本和良好安全性的优势，是锂离子电池中正极活性材料的优选材料。但是，采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池，普遍存在负极表面无法形成稳定结构的SEI膜的情况，导致采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池的循环性能的提升存在瓶颈。
发明内容
本申请的目的在于提供一种锂离子电池，其旨在改善现有的采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池的循环性能的提升存在瓶颈的技术问题。
本申请提供一种锂离子电池，包括：隔膜、正极极片、负极极片以及电解液。
其中，正极极片的涂层包括正极材料；正极材料包括正极活性材料、导电剂以及粘结剂，正极活性材料包括磷酸铁锂以及锰酸锂中的至少一种。
正极极片的涂层还包括负极成膜添加剂；和/或，电解液包括负极成膜添加剂；负极成膜添加剂包括单质硫以及金属硫化物中的至少一种。
电解液包括成膜溶剂，成膜溶剂的结构式如下：
Figure PCTCN2022112111-appb-000001
R 1、R 2、R 3以及R 4各自独立地为氢原子、卤素原子、烷基或烃基。
或，成膜溶剂的结构式如下：
Figure PCTCN2022112111-appb-000002
R 5以及R 6各自独立地为氢原子、卤素原子、烷基或烃基。
当采用磷酸铁锂和/或锰酸锂作为正极活性材料制备锂离子电池时，本申请通过在正极极片的涂层和/或电解液中加入包括单质硫以及金属硫化物中的至少一种的负极成膜添加剂，可以在锂离子电池首周充电过程中(即锂离子电池内部的电化学反应过程中)迁移到负极表面，并参与负极表面SEI膜的形成，有利于使得负极表面SEI膜中同时含有+4价和/或+6价的高价态硫成分和-2价至-1/4价的低价态硫成分。
高价态硫成分能快速传递锂离子，促进锂离子在界面处的传输。负极成膜添加剂在负极被还原为多硫化物，多硫化物与本成膜溶剂发生反应，生成具有PEO结构的低价态硫成分。PEO结构具有良好的韧性，能够有效缓解负极材料在充放电过程中的体积形变。高价态硫成分和低价态硫成分的存在，有利于使得负极表面形成稳定结构的SEI膜，降低电荷转移阻抗和极化，提升电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
在本申请的一些实施例中，金属硫化物可以包括硫化锂、硫化铁、二硫化铁、二硫化钛、三硫化钛、硫化锌、二硫化锡、二硫化钼、二硫化钨、二硫化钴以及硫化镍中的至少一种。
在本申请的一些实施例中，烷基或所述烃基可以为取代烷基或取代烃基。
可选地，烷基可以为甲基、乙基或丁基；烃基可以为乙烯基、丙烯基或丁烯基。
在本申请的一些实施例中，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比可以为(0.1-10)：100。
负极成膜添加剂的添加量满足上述情况下，有利于进一步降低电荷传输阻抗以及提高 循环容量，进而实现提升电池的循环性能。
可选地，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比可以为(0.1-3)：100。
在本申请的一些实施例中，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度可以为0.01-10g/L。
负极成膜添加剂的添加量满足上述情况下，有利于进一步降低电荷传输阻抗以及提高循环容量，进而实现提升电池的循环性能。
可选地，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度可以为0.05-1g/L。
在本申请的一些实施例中，当正极极片的涂层包括负极成膜添加剂时，正极极片的制备方法可以包括：将含有负极成膜添加剂、正极活性材料、导电剂以及粘结剂的混合浆料涂覆于正极箔材后，于80-160℃下热处理4-12h。
上述热处理条件，有利于提高混合浆料在正极箔材表面的均匀性，进而有利于进一步提升电池的循环性能。
在本申请的一些实施例中，当正极极片的涂层包括负极成膜添加剂时，正极极片的制备方法可以包括：采用气相法或液相法使负极成膜添加剂分散于液体或气体后，再均匀地沉积在正极极片的表面。
在本申请的一些实施例中，当正极极片的涂层包括负极成膜添加剂时，正极极片的制备方法可以包括：将升华硫粉溶于二硫化碳中，将含有硫单质的二硫化碳涂布于所述正极极片的表面后干燥。
在本申请的一些实施例中，负极极片的涂层可以包括负极活性材料，负极活性材料可以包括碳基材料、硅基材料、合金以及锂中的至少一种。
负极活性材料选用上述物质，有利于实现负极表面形成稳定的SEI膜。
在本申请的一些实施例中，负极活性材料可以包括石墨、硅碳450或硅。
在本申请的一些实施例中，成膜溶剂可以包括碳酸乙烯酯、氟代碳酸乙烯酯、双氟代碳酸乙烯酯、碳酸亚乙烯酯以及碳酸丁烯酯中的至少一种。
成膜溶剂包括上述物质，可以与负极成膜添加剂在负极被还原形成的多硫化物发生反应，生成具有PEO结构的低价态硫成分，进一步提高电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
在本申请的一些实施例中，成膜溶剂可以占电解液中总溶剂质量的1-100％。
成膜溶剂占电解液中总溶剂质量的1-100％，可以有效提高电池循环的稳定性。
可选地，成膜溶剂可以占电解液中总溶剂质量的5-40％。
在本申请的一些实施例中，负极成膜添加剂的粒径D 50可以为0.01-20μm。
负极成膜添加剂的粒径D 50在上述范围下，有利于进一步提高电池循环的稳定性。
可选地，负极成膜添加剂的粒径D 50可以为0.05-5μm。
在本申请的一些实施例中，锂离子电池化成后，负极极片的表面电解质界面膜中含有高价态硫成分和低价态硫成分；负极极片的表面电解质界面膜中，高价态硫成分的价态为+4价和/或+6价，S2p谱峰为168-172eV；负极极片的表面电解质界面膜中，低价态硫成分的价态为-2价至-1/4价，S2p谱峰为160-166eV。
可选地，负极极片的表面电解质界面膜中，高价态硫成分的S2p谱峰面积与低价态硫成分的S2p谱峰面积比可以为(1-4)：1；
可选地，锂离子电池化成后，正极极片的表面电解质界面膜中可以含有高价态硫成分；正极极片的表面电解质界面膜中，高价态硫成分的价态可以为+4价和/或+6价，S2p谱峰可以为168-172eV。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，应当理解，以下附图仅示出了本申请的某些实施例，因此不应被看作是对范围的限定，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他相关的附图。
图1示出了实施例1制得的锂离子电池化成后负极的X射线光电子能谱测试S2p谱图。
图2示出了实施例1制得的锂离子电池化成后正极的X射线光电子能谱测试S2p谱图。
图3示出了实施例1与对比例1制得的锂离子电池的首周充电测试曲线图。
图4示出了实施例1与对比例1制得的锂离子电池的100周循环性能图。
图5示出了实施例1与对比例1制得的锂离子电池的电池倍率图。
图6示出了实施例1与对比例1制得的锂离子电池的电池阻抗图。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将对本申请实施例中的技术方案进行清楚、完整地描述。实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市售购买获得的常规产品。
采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池，普遍存在负极表面无法形成稳定结构的SEI膜的情况，导致采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池的循环性能的提升存在瓶颈。
为此，本申请提供一种锂离子电池，包括：隔膜、正极极片、负极极片以及电解液。
其中，正极极片的涂层包括正极材料；正极材料包括正极活性材料、导电剂以及粘结剂，正极活性材料包括磷酸铁锂以及锰酸锂中的至少一种。
正极极片的涂层还包括负极成膜添加剂；和/或，电解液包括负极成膜添加剂；负极成膜添加剂包括单质硫以及金属硫化物中的至少一种。
电解液包括成膜溶剂，成膜溶剂的结构式如下：
Figure PCTCN2022112111-appb-000003
R 1、R 2、R 3以及R 4各自独立地为氢原子、卤素原子、烷基或烃基。
或，成膜溶剂的结构式如下：
Figure PCTCN2022112111-appb-000004
R 5以及R 6各自独立地为氢原子、卤素原子、烷基或烃基。
可以理解的是，在本申请中，正极活性材料可以同时包括磷酸铁锂以及锰酸锂，也可以仅包括磷酸铁锂，也可以仅包括锰酸锂。负极成膜添加剂可以同时选用单质硫和金属硫化物，也可以仅选用单质硫，也可以仅选用金属硫化物。正极极片的涂层和电解液中可以同时含有本申请限定的负极成膜添加剂，也可以仅是正极极片的涂层中含有本申请限定的负极成膜添加剂，也可以仅是电解液中含有本申请限定的负极成膜添加剂。
在本申请中，成膜添加剂包括单质硫以及金属硫化物中的至少一种，成膜添加剂的作用在于有效改善负极SEI膜的稳定性。具体的，当采用磷酸铁锂和/或锰酸锂作为正极活性材料制备锂离子电池时，本申请通过在正极极片的涂层和/或电解液中加入包括单质硫以及金属硫化物中的至少一种的负极成膜添加剂，可以在锂离子电池首周充电过程中(即锂离子电池内部的电化学反应过程中)迁移到负极表面，并参与负极表面SEI膜的形成，有利于使得负极表面SEI膜中同时含有+4价和/或+6价的高价态硫成分和-2价至-1/4价的低价态硫成分。
高价态硫成分能快速传递锂离子，促进锂离子在界面处的传输。负极成膜添加剂在负 极被还原为多硫化物，多硫化物与本申请限定的成膜溶剂发生反应，生成具有PEO结构的低价态硫成分。PEO结构具有良好的韧性，能够有效缓解负极材料在充放电过程中的体积形变；使得锂离子电池的首周充电曲线在1-1.3V和1.6-2V可以观测到反应平台。
高价态硫成分和低价态硫成分的存在，有利于使得负极表面形成稳定结构的SEI膜，降低电荷转移阻抗和极化，提升电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
作为示例性地，当负极成膜添加剂选用金属硫化物时，金属硫化物可以选自硫化锂、硫化铁、二硫化铁、二硫化钛、三硫化钛、硫化锌、二硫化锡、二硫化钼、二硫化钨、二硫化钴以及硫化镍中的至少一种。
需要说明的是，金属硫化物也可以不限于上述物质。
在本申请中，当负极成膜添加剂选自单质硫时，相比于负极成膜添加剂选自金属硫化物，有利于进一步提高电池的循环性能。
在本申请中，负极成膜添加剂的粒径D 50为0.01-20μm。负极成膜添加剂的粒径D 50在上述范围下，有利于进一步提高电池循环的稳定性。
作为示例性地，负极成膜添加剂的粒径D 50可以为0.01μm、0.05μm、2μm、5μm、10μm或者20μm等等。
可选地，负极成膜添加剂的粒径D 50可以为0.05-5μm，负极成膜添加剂的粒径D 50在上述粒径范围下，提高电池循环的稳定性较佳。
在本申请中，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比为(0.1-10)：100。负极成膜添加剂的添加量满足上述情况下，有利于进一步降低电荷传输阻抗以及提高循环容量，进而实现提升电池的循环性能。
作为示例性地，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比可以为0.1：100、1：100、2：100、5：100或者10：100等等。
可选地，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比为(0.1-3)：100；上述配比条件下，有利于进一步提升电池的循环性能。
可选地，当正极极片的涂层包括负极成膜添加剂时，正极极片的制备方法包括：将含有负极成膜添加剂、正极活性材料、导电剂以及粘结剂的混合浆料涂覆于正极箔材后，于80-160℃下热处理4-12h。
上述热处理条件，有利于提高混合浆料在正极箔材表面的均匀性，进而有利于进一步提升电池的循环性能。
作为示例性地，热处理的温度可以为80℃、100℃、120℃、140℃或者160℃等等；热处理的时间可以为4h、5h、8h、10h或者12h等等。
需要说明的是，本申请不对混合浆料中负极成膜添加剂、正极活性材料、导电剂以及 粘结剂的添加顺序进行限定。
在其他可行的实施例中，当正极极片的涂层包括负极成膜添加剂时，正极极片的制备方法也可以采用气相法或液相法使负极成膜添加剂分散于液体或气体后，再均匀地沉积在正极极片表面。作为示例性地，正极极片的制备方法也可以为：将升华硫粉溶于二硫化碳中，将含有硫单质的二硫化碳涂布于正极极片的表面后干燥。
在本申请中，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度为0.01-10g/L。负极成膜添加剂的添加量满足上述情况下，有利于进一步降低电荷传输阻抗以及提高循环容量，进而实现提升电池的循环性能。
作为示例性地，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度可以为0.01g/L、0.05g/L、0.5g/L、1.0g/L、2.0g/L、5.0g/L或者10g/L等等。
可选地，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度可以为0.05-1g/L。
承上所述，成膜溶剂结构中含环状碳酸酯，成膜溶剂的结构式中的R 1、R 2、R 3以及R 4各自独立地为氢原子、卤素原子、烷基或烃基。其中，烷基或烃基可以为取代烷基或取代烃基，例如，卤代烷基或卤代烃基；烷基也可以为甲基、乙基或丁基等；烃基可以为乙烯基、丙烯基或丁烯基等。
作为示例性地，成膜溶剂可以选自碳酸乙烯酯(EC)、氟代碳酸乙烯酯(FEC)、双氟代碳酸乙烯酯(DFEC)、碳酸亚乙烯酯(VC)以及碳酸丁烯酯(BC)中的至少一种。成膜溶剂包括上述物质，可以与负极成膜添加剂在负极被还原形成的多硫化物发生反应，生成具有PEO结构的低价态硫成分，进一步提高电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
需要说明的是，成膜溶剂也可以不限于上述物质，只要能够满足本申请限定的溶剂的结构式即可。
在本申请中，成膜溶剂占电解液中总溶剂质量的1-100％，可以有效提高电池循环的稳定性。
作为示例性地，成膜溶剂占电解液中总溶剂的质量分数可以为1％、5％、10％、30％、50％或者100％等等。
可选地，成膜溶剂可以占电解液中总溶剂的5-40％，有利于进一步提高电池循环的稳定性。
在本申请中，当正极活性材料选自磷酸铁锂时，相比于正极活性材料选自锰酸锂，有利于进一步提高电池的循环性能。
在本申请中，负极极片的涂层包括负极活性材料，负极活性材料包括碳基材料、硅基 材料、合金以及锂中的至少一种。负极活性材料选用上述物质，有利于实现负极表面形成稳定的SEI膜。
作为示例性地，负极活性材料可以包括石墨、硅碳450或硅等。
进一步地，当负极活性材料选自石墨时，有利于进一步提高电池的循环性能。
在本申请中，锂离子电池化成后，负极极片的表面电解质界面膜(SEI膜)中含有高价态硫成分和低价态硫成分；负极极片的表面电解质界面膜(SEI膜)中，高价态硫成分的价态为+4价和/或+6价，S2p谱峰为168-172eV；负极极片的表面电解质界面膜(SEI膜)中，低价态硫成分的价态为-2价至-1/4价，S2p谱峰为160-166eV。
可选地，负极极片的表面电解质界面膜(SEI膜)中，高价态硫成分的S2p谱峰面积与低价态硫成分的S2p谱峰面积比可以为(1-4)：1，有利于进一步提高电池的循环性能。
在本申请中，锂离子电池化成后，正极极片的表面电解质界面膜(CEI膜)中含有高价态硫成分；正极极片的表面电解质界面膜(CEI膜)中，高价态硫成分的价态为+4价和/或+6价，S2p谱峰为168-172eV。
以下结合实施例对本申请提供的锂离子电池的特征和性能作进一步的详细描述。
实施例1
本实施例提供一种锂离子电池，采用如下方法制得：
(1)将10g的LiFePO 4与0.1g的单质硫粉混合均匀，再加入0.56g的导电炭黑(SP)以及0.56g的聚偏氟乙烯(PVDF)，搅拌均匀得到正极混合浆料。将正极混合浆料均匀涂覆在Al箔上，经过干燥、辊压后得到正极极片。
(2)将9.4g的石墨、0.3g的导电炭黑(SP)、0.15g的羧甲基纤维素钠(CMC)、0.15g的丁苯橡胶(SBR)以及25mL的去离子水搅拌均匀得到负极混合浆料。将负极混合浆料均匀涂覆在Cu箔上，经过干燥、辊压后得到负极极片。
(3)将隔膜置于步骤(1)得到的正极极片与步骤(2)得到的负极极片之间，注入120uL电解液，放置垫片、弹片，置于压力机密封，形成锂离子电池。
其中，电解液为电解液为1.0MLiPF 6inEC/DMC/EMC＝1：1：1，v/v/v。
实施例2
本实施例提供一种锂离子电池，采用如下方法制得：
(1)将10g的LiFePO 4、0.56g的导电炭黑(SP)以及0.56g的聚偏氟乙烯(PVDF)搅拌均匀得到正极混合浆料。将正极混合浆料均匀涂覆在Al箔上，经过干燥、辊压后得到正极极片。
(2)将9.4g的石墨、0.3g的导电炭黑(SP)、0.15g的羧甲基纤维素钠(CMC)、0.15g的丁苯橡胶(SBR)以及25mL的去离子水搅拌均匀得到负极混合浆料。将负极混合浆料 均匀涂覆在Cu箔上，经过干燥、辊压后得到负极极片。
(3)将隔膜置于步骤(1)得到的正极极片与步骤(2)得到的负极极片之间，注入120uL最终电解液，放置垫片、弹片，置于压力机密封，形成锂离子电池。
其中，预先配得电解液为1.0MLiPF 6inEC/DMC/EMC＝1：1：1，v/v/v，向电解液中加入单质硫粉并搅拌至彻底溶解，将该电解液作为最终电解液；单质硫在最终电解液中的终浓度为0.5mg/mL。
实施例3
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于步骤(1)中单质硫的质量不同，本实施例中单质硫的质量为0.01g。
实施例4
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于步骤(1)中单质硫的质量不同，本实施例中单质硫的质量为0.5g。
实施例5
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(2)中的石墨替换为硅碳450。
实施例6
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(2)中的石墨替换为硅。
实施例7
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(1)中的LiFePO 4替换为LiMnO 2。
实施例8
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(1)中的单质硫粉替换为硫化锂。
实施例9
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(1)中的单质硫粉替换为二硫化钛。
实施例10
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(1)中的单质硫粉替换为二硫化钼。
实施例11
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(3)中的碳酸 乙烯酯(EC)替换为双氟代碳酸乙烯酯(DFEC)。
实施例12
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于将步骤(3)中的碳酸乙烯酯(EC)替换为碳酸亚乙烯酯(VC)。
实施例13
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于步骤(3)中的电解液的不同，本实施例中电解液为1.0MLiPF 6inEC。
实施例14
本实施例提供一种锂离子电池，本实施例与实施例1的区别在于步骤(3)中的电解液的不同，本实施例中电解液为1.0MLiPF 6inDMC/EMC＝1：1,v/v+5wt％EC。
实施例15
本实施例提供一种锂离子电池，本实施例与实施例2的区别在于步骤(3)中单质硫在电解液中的浓度不同，本实施例中单质硫在电解液中的浓度0.01mg/mL。
实施例16
本实施例提供一种锂离子电池，本实施例与实施例2的区别在于步骤(3)中单质硫在电解液中的浓度不同，本实施例中单质硫在电解液中的浓度2.0mg/mL。
对比例1
本对比例提供一种锂离子电池，本对比例与实施例1的区别在于步骤(1)的不同。本对比例的步骤(1)如下：
将10g的LiFePO 4、0.56g的导电炭黑(SP)以及0.56g的聚偏氟乙烯(PVDF)搅拌均匀得到正极混合浆料。将正极混合浆料均匀涂覆在Al箔上，经过干燥、辊压后得到正极极片。
对比例2
本对比例提供一种锂离子电池，本对比例与实施例1的区别在于步骤(3)中电解液的不同，本对比例中电解液为1.0MLiPF 6inDMC/EMC＝1：1,v/v。
实验例1
将实施例1制得的锂离子电池化成后，分别测试负极和正极的X射线光电子能谱S2p谱，实验结果如图1和图2所示。
从图1可以看出，实施例1制得的锂离子电池化成后的负极X射线光电子能谱S2p谱的168-172eV处具有对应于高价态硫成分的特征峰，160-166eV处具有对应于低价态硫成分特征峰；表明实施例1制得的锂离子电池化成后，单质硫(负极成膜添加剂)发生反应在负极表面SEI膜中同时生成+4价和/或+6价的高价态硫成分和-2价至-1/4价的低价态硫 成分。高价态硫的生成，是由于硫在正极发生了氧化反应，生成了类似R-OSO2OLi的成分并扩散到负极，能够快速传输Li离子，减小界面阻抗；低价态硫成分的存在推测是因为单质硫(负极成膜添加剂)在负极被还原为多硫化物，多硫化物与碳酸乙烯酯(EC)发生反应，生成具有PEO结构SEI膜。
从图2可以看出，实施例1制得的锂离子电池化成后的正极X射线光电子能谱S2p谱的168-172eV处具有对应于高价态硫成分的特征峰；表明实施例1制得的锂离子电池化成后，单质硫(负极成膜添加剂)发生反应在正极表面CEI膜中生成+4价和/或+6价的高价态硫成分。
实验例2
将实施例1与对比例1制得的锂离子电池分别进行电池首周充电测试、100周循环性能测试、电池倍率测试以及电池阻抗测试，对比实验结果分别如图3、图4、图5和图6所示。
图3中a部分是横坐标电池容量(Capacity)在0-180mAh·g -1区间内的循环性能图，图3中b部分是横坐标电池容量(Capacity)在0-1.5mAh·g -1区间内的循环性能图。
从图3可以看出，实施例1制得的锂离子电池的首周充电曲线相比于对比例1制得的锂离子电池的首周充电曲线，在1-1.3V和1.6-2.0V可以观测到反应平台。
从图4可以看出，实施例1制得的锂离子电池的100周循环性能明显优于对比例1制得的锂离子电池的100周循环性能。
从图5可以看出，实施例1制得的锂离子电池的倍率性能明显优于对比例1制得的锂离子电池的倍率性能。
从图6可以看出，实施例1制得的锂离子电池的电荷转移阻抗明显低于对比例1制得的锂离子电池的电荷转移阻抗。
从图3至图6的分析结果可知，在锂离子电池的正极极片的涂层中加入单质硫(即本申请限定的负极成膜添加剂)，可以有效提高负极表面形成的SEI膜的稳定性，降低电荷转移阻抗和极化，提升电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
实验例3
将实施例1-17以及对比例1-2提供的锂离子电池分别进行循环10周后阻抗以及循环100周电池容量测试，实验结果如表1所示。
表1
Figure PCTCN2022112111-appb-000005
Figure PCTCN2022112111-appb-000006
从表1可以看出，实施例1-16提供的锂离子电池的循环10周后阻抗明显低于对比例1-2提供的锂离子电池的循环10周后阻抗，实施例1-16提供的锂离子电池的循环100周电池容量明显高于对比例1-2提供的锂离子电池的循环10周后阻抗，表明在正极极片的涂层或电解液中加入本申请限定的负极成膜添加剂以及在电解液中加入本申请限定的成膜溶剂，可以有效提高锂离子电池的循环性能。
从实施例3-14与实施例1的对比可知，当正极极片的涂层包括负极成膜添加剂时，负极成膜添加剂与正极活性材料的质量比、负极活性材料的选用、正极活性材料的选用、负极成膜添加剂的选用、成膜溶剂的选用以及成膜溶剂在电解液的质量分数均能够进一步影响锂离子电池的循环性能。
从实施例15-16与实施例2的对比可知，当电解液包括负极成膜添加剂时，负极成膜添加剂在电解液中的质量浓度能够进一步影响锂离子电池的循环性能。
综上，本申请提供的锂离子电池可以有效提高采用磷酸铁锂或锰酸锂作为正极活性材料的锂离子电池的循环性能。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。
工业实用性
本申请提供了一种锂离子电池，当采用磷酸铁锂和/或锰酸锂作为正极活性材料制备锂离子电池时，本申请通过在正极极片的涂层和/或电解液中加入包括单质硫以及金属硫化物中的至少一种的负极成膜添加剂，可以在锂离子电池首周充电过程中(即锂离子电池内部的电化学反应过程中)迁移到负极表面，并参与负极表面SEI膜的形成，有利于使得负极表面SEI膜中同时含有+4价和/或+6价的高价态硫成分和-2价至-1/4价的低价态硫成分。
高价态硫成分能快速传递锂离子，促进锂离子在界面处的传输。负极成膜添加剂在负极被还原为多硫化物，多硫化物与本成膜溶剂发生反应，生成具有PEO结构的低价态硫成分。PEO结构具有良好的韧性，能够有效缓解负极材料在充放电过程中的体积形变。高价态硫成分和低价态硫成分的存在，有利于使得负极表面形成稳定结构的SEI膜，降低电荷转移阻抗和极化，提升电池循环的稳定性，进而实现提升锂离子电池的倍率性能。
此外，可以理解的是，本申请的锂离子电池是可以重现的，并且可以用在多种工业应用中。例如，本申请的锂离子电池可以用于电池制造技术领域。

Claims (14)

  1. 一种锂离子电池，其特征在于，包括：隔膜、正极极片、负极极片以及电解液；
    其中，所述正极极片的涂层包括正极材料；所述正极材料包括正极活性材料、导电剂以及粘结剂，所述正极活性材料包括磷酸铁锂以及锰酸锂中的至少一种；
    所述正极极片的涂层还包括负极成膜添加剂；和/或，所述电解液包括负极成膜添加剂；所述负极成膜添加剂包括单质硫以及金属硫化物中的至少一种；
    所述电解液包括成膜溶剂，所述成膜溶剂的结构式如下：
    Figure PCTCN2022112111-appb-100001
    R 1、R 2、R 3以及R 4各自独立地为氢原子、卤素原子、烷基或烃基；
    或，所述成膜溶剂的结构式如下：
    Figure PCTCN2022112111-appb-100002
    R 5以及R 6各自独立地为氢原子、卤素原子、烷基或烃基。
  2. 根据权利要求1所述的锂离子电池，其特征在于，所述金属硫化物包括硫化锂、硫化铁、二硫化铁、二硫化钛、三硫化钛、硫化锌、二硫化锡、二硫化钼、二硫化钨、二硫化钴以及硫化镍中的至少一种。
  3. 根据权利要求1或2所述的锂离子电池，其特征在于，所述烷基或所述烃基为取代烷基或取代烃基；
    可选地，所述烷基为甲基、乙基或丁基；所述烃基为乙烯基、丙烯基或丁烯基。
  4. 根据权利要求1至3中任一项所述的锂离子电池，其特征在于，当所述正极极片的涂层包括所述负极成膜添加剂时，所述负极成膜添加剂与所述正极活性材料的质量比为(0.1-10)：100；
    可选地，当所述正极极片的涂层包括所述负极成膜添加剂时，所述负极成膜添加剂与 所述正极活性材料的质量比为(0.1-3)：100。
  5. 根据权利要求1至3中任一项所述的锂离子电池，其特征在于，当所述电解液包括所述负极成膜添加剂时，所述负极成膜添加剂在所述电解液中的质量浓度为0.01-10g/L；
    可选地，当所述电解液包括所述负极成膜添加剂时，所述负极成膜添加剂在所述电解液中的质量浓度为0.05-1g/L。
  6. 根据权利要求1至4中任一项所述的锂离子电池，其特征在于，当所述正极极片的涂层包括所述负极成膜添加剂时，所述正极极片的制备方法包括：将含有所述负极成膜添加剂、所述正极活性材料、所述导电剂以及所述粘结剂的混合浆料涂覆于正极箔材后，于80-160℃下热处理4-12h。
  7. 根据权利要求1至4中任一项所述的锂离子电池，其特征在于，当所述正极极片的涂层包括所述负极成膜添加剂时，所述正极极片的制备方法包括：采用气相法或液相法使所述负极成膜添加剂分散于液体或气体后，再均匀地沉积在所述正极极片的表面。
  8. 根据权利要求1至4中任一项所述的锂离子电池，其特征在于，当所述正极极片的涂层包括所述负极成膜添加剂时，所述正极极片的制备方法包括：将升华硫粉溶于二硫化碳中，将含有硫单质的二硫化碳涂布于所述正极极片的表面后干燥。
  9. 根据权利要求1至8中任一项所述的锂离子电池，其特征在于，所述负极极片的涂层包括负极活性材料，所述负极活性材料包括碳基材料、硅基材料、合金以及锂中的至少一种。
  10. 根据权利要求9所述的锂离子电池，其特征在于，所述负极活性材料包括石墨、硅碳450或硅。
  11. 根据权利要求1至10中任一项所述的锂离子电池，其特征在于，所述成膜溶剂包括碳酸乙烯酯、氟代碳酸乙烯酯、双氟代碳酸乙烯酯、碳酸亚乙烯酯以及碳酸丁烯酯中的至少一种。
  12. 根据权利要求1至11中任一项所述的锂离子电池，其特征在于，所述成膜溶剂占所述电解液中总溶剂质量的1-100％；
    可选地，所述成膜溶剂占所述电解液中总溶剂质量的5-40％。
  13. 根据权利要求1至12中任一项所述的锂离子电池，其特征在于，所述负极成膜添加剂的粒径D 50为0.01-20μm；
    可选地，所述负极成膜添加剂的粒径D 50为0.05-5μm。
  14. 根据权利要求1至13中任一项所述的锂离子电池，其特征在于，锂离子电池化成后，所述负极极片的表面电解质界面膜中含有高价态硫成分和低价态硫成分；
    所述负极极片的表面电解质界面膜中，高价态硫成分的价态为+4价和/或+6价，S2p 谱峰为168-172eV；
    所述负极极片的表面电解质界面膜中，低价态硫成分的价态为-2价至-1/4价，S2p谱峰为160-166eV；
    可选地，所述负极极片的表面电解质界面膜中，高价态硫成分的S2p谱峰面积与低价态硫成分的S2p谱峰面积比为(1-4)：1；
    可选地，所述锂离子电池化成后，所述正极极片的表面电解质界面膜中含有高价态硫成分；所述正极极片的表面电解质界面膜中，高价态硫成分的价态为+4价和/或+6价，S2p谱峰为168-172eV。
PCT/CN2022/112111 2022-07-14 2022-08-12 一种锂离子电池 WO2024011702A1 (zh)

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