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WO2023122855A1 - 一种电化学装置和电子装置 - Google Patents

一种电化学装置和电子装置 Download PDF

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Publication number
WO2023122855A1
WO2023122855A1 PCT/CN2021/141475 CN2021141475W WO2023122855A1 WO 2023122855 A1 WO2023122855 A1 WO 2023122855A1 CN 2021141475 W CN2021141475 W CN 2021141475W WO 2023122855 A1 WO2023122855 A1 WO 2023122855A1
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Prior art keywords
silicon
negative electrode
lithium
present application
electrochemical device
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PCT/CN2021/141475
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English (en)
French (fr)
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廖群超
华传山
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宁德新能源科技有限公司
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Priority to EP21969243.1A priority Critical patent/EP4456179A1/en
Priority to PCT/CN2021/141475 priority patent/WO2023122855A1/zh
Priority to CN202180030502.7A priority patent/CN115516682A/zh
Publication of WO2023122855A1 publication Critical patent/WO2023122855A1/zh
Priority to US18/754,596 priority patent/US20240347712A1/en

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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents
    • 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 field of electrochemical technology, in particular to an electrochemical device and an electronic device.
  • Lithium-ion batteries have many advantages such as large volume and mass energy density, long cycle life, high nominal voltage, low self-discharge rate, small size, and light weight, and have a wide range of applications in the field of consumer electronics. With the rapid development of electric vehicles and mobile electronic devices in recent years, people have higher and higher requirements for the energy density, safety, and cycle performance of batteries. They are looking forward to the emergence of new lithium-ion batteries with comprehensive performance improvements.
  • Silicon material has a high specific capacity, and as an anode material for lithium-ion batteries, it can significantly increase the energy density of lithium-ion batteries.
  • SEI solid electrolyte interfacial film
  • the purpose of this application is to provide an electrochemical device and an electronic device to improve the cycle performance and expansion performance of lithium ion batteries.
  • the specific technical scheme is as follows:
  • the first aspect of the present application provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer includes a silicon-based composite material, the silicon-based composite material includes silicon-based particles, the strength of the negative electrode current collector is A MPa, and the difference between the maximum value and the minimum value of the relative percentage content of silicon atoms in the silicon-based particles is B%, The mass content of silicon element in the negative electrode material layer is C%, which satisfies:
  • B satisfies: 10 ⁇ B ⁇ 16.
  • C satisfies: 1 ⁇ C ⁇ 20.
  • A satisfies: 370 ⁇ A ⁇ 800.
  • the thickness of one side of the negative electrode material layer is H
  • the maximum particle size of the silicon-based particles is Dmax, which satisfies: H ⁇ 3 ⁇ Dmax.
  • the Dmax of the silicon-based particles satisfies: 10 ⁇ m ⁇ Dmax ⁇ 25 ⁇ m.
  • the thickness H of one side of the negative electrode material layer satisfies: 30 ⁇ m ⁇ H ⁇ 90 ⁇ m.
  • the porosity of the negative electrode sheet is P%, and the P and the C satisfy: P>15 ⁇ C 1/4 .
  • P satisfies: 18 ⁇ P ⁇ 40.
  • the electrolyte includes fluoroethylene carbonate, based on the quality of the electrolyte, the mass percentage of the fluoroethylene carbonate is Q%, and the Q and the The above C satisfies: 0.3 ⁇ C/Q ⁇ 3.
  • Q satisfies: 1 ⁇ Q ⁇ 20.
  • the silicon-based particles include silicon and carbon elements, and the atomic ratio of silicon and carbon in the silicon-based particles is 1:1 to 2.5.
  • the negative pole sheet of the present application includes silicon-based particles having the above-mentioned atomic ratio of elements, and a lithium-ion battery with good expansion performance and cycle performance can be obtained.
  • a second aspect of the present application provides an electronic device, which includes the electrochemical device described in the first aspect above.
  • the application provides an electrochemical device and an electronic device, including a positive electrode sheet, a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer, the negative electrode material layer includes a silicon-based composite material, and the silicon-based composite material includes Silicon-based particles, the strength of the negative electrode current collector is A MPa, the difference between the maximum and minimum relative percentages of silicon atoms in the silicon-based particles is B%, and the mass content of silicon in the negative electrode material layer is C%. satisfy:
  • the obtained lithium-ion battery has good cycle performance and expansion performance.
  • any embodiment of the present application does not necessarily need to achieve all the advantages described above at the same time.
  • Figure 1a is a scanning electron microscope (SEM) image of a section of a silicon-based particle
  • Figure 1b is the fluctuation curve of the relative percentage content of silicon atoms in the X-ray energy spectrometer (EDS) line scan.
  • a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to the lithium-ion battery.
  • the prior art in order to improve the problem of lithium intercalation expansion of the silicon negative electrode, it is mainly achieved by nanosiliconization and compounding of silicon. For example, by reducing the particle size of the silicon material to the nanometer level, the stress generated during lithium intercalation can be relieved, and the cracking of the material can be reduced; or by compounding other carbonaceous materials, the contact with the electrolyte can be reduced, and the solid electrolyte interface (SEI) can be reduced. produce.
  • SEI solid electrolyte interface
  • the nano-silicon method has the problems of complex preparation process and high energy consumption, and the high specific surface area of the nano-silicon material makes it extremely easy to agglomerate, which affects the electrical performance of the lithium-ion battery;
  • the existing composite method is only simple Focusing on the improvement of carbonaceous composite materials, while ignoring the influence of other factors on the expansion of lithium-ion batteries as a whole, it has limitations in improving the expansion performance and cycle performance of lithium-ion batteries.
  • volume expansion caused by lithium intercalation is an intrinsic property of silicon-based materials.
  • the present application provides an electrochemical device and an electronic device to improve the cycle performance and expansion performance of a lithium-ion battery.
  • the first aspect of the present application provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer includes a silicon-based Composite material, the silicon-based composite material includes silicon-based particles, the strength of the negative electrode current collector is A MPa, and the difference between the maximum value and the minimum value of the relative percentage content of silicon atoms in the silicon-based particles is B% , the mass content of silicon in the negative electrode material layer is C%, satisfying:
  • the difference B% between the maximum and minimum relative percentages of silicon atoms in silicon-based particles is a fluctuation value, which can represent the uniformity of silicon element distribution in silicon-based particles.
  • Volume expansion will occur during the lithium intercalation process of silicon, and the expansion will occur from multiple directions (such as along the length direction, width direction and height direction of the lithium-ion battery), so the negative electrode current collector needs to have a certain strength to resist the expansion. stress, thereby inhibiting the deformation of lithium-ion batteries.
  • the inventors of the present application have also found that the more uniform the silicon element distribution inside the silicon-based particles, the smaller the stress generated by the expansion; the more the silicon element content in the negative electrode material layer, the greater the expansion tendency of the lithium-ion battery during the cycle; With the fluctuation of silicon element distribution in silicon-based particles and the increase in the mass content of silicon element in the negative electrode material layer, the demand for the strength of the negative electrode current collector is higher, but when the negative electrode current collector exceeds a certain strength, the degree of improvement in cycle and expansion performance will drop significantly. Based on the above findings, the present application can obtain a lithium-ion battery with good cycle performance and expansion performance by synergistically adjusting A, B, and C to meet the above conditions.
  • B satisfies: 10 ⁇ B ⁇ 16.
  • C satisfies: 1 ⁇ C ⁇ 20.
  • A satisfies: 370 ⁇ A ⁇ 800.
  • the thickness of one side of the negative electrode material layer is H
  • the maximum particle size of the silicon-based particles is Dmax, which satisfies: H ⁇ 3 ⁇ Dmax.
  • the negative electrode material layer can be provided on one side of the negative electrode collector, that is, single-sided coating, or can be provided on both sides of the negative electrode current collector, that is, double-sided coating.
  • H the overall thickness of the negative electrode sheet
  • h the thickness of the negative electrode current collector
  • H the thickness of the negative electrode current collector
  • the Dmax of the silicon-based particles satisfies: 10 ⁇ m ⁇ Dmax ⁇ 25 ⁇ m.
  • the following situations can be avoided: too large Dmax of silicon-based particles can easily lead to uneven expansion of the pole piece, and bump problems are likely to occur during processing, which affects the interface and expansion performance of the lithium-ion battery; If the Dmax of the silicon-based particles is too small, the specific surface area will be too large, and more SEI films will accumulate on the surface of the negative electrode, increasing the expansion tendency, and more binders are required to achieve the bonding effect during processing, reducing lithium Energy density of ion batteries. Therefore, in the present application, by adjusting Dmax within the above range, it is beneficial to balance the processing performance, expansion performance and energy density of the lithium-ion battery.
  • the thickness H of one side of the negative electrode material layer satisfies: 30 ⁇ m ⁇ H ⁇ 90 ⁇ m.
  • the porosity of the negative electrode sheet is P%, and the P and the C satisfy: P>15 ⁇ C 1/4 .
  • P and C satisfy: P>15 ⁇ C 1/4 .
  • P satisfies: 18 ⁇ P ⁇ 40.
  • the electrolyte includes fluoroethylene carbonate (FEC), based on the quality of the electrolyte, the mass percentage of fluoroethylene carbonate is Q%, and the Q and the The above C satisfies: 0.3 ⁇ C/Q ⁇ 3.
  • FEC fluoroethylene carbonate
  • the mass percentage of fluoroethylene carbonate is Q%
  • the Q and the The above C satisfies: 0.3 ⁇ C/Q ⁇ 3.
  • Q satisfies: 1 ⁇ Q ⁇ 20.
  • Fluoroethylene carbonate (FEC) is an important film-forming additive in the electrolyte.
  • the SEI film produced by its decomposition during the lithium-ion battery cycle insulates the further contact between the material and the electrolyte, reducing the consumption of lithium ions.
  • the silicon-based particles include silicon and carbon elements, and the atomic ratio of silicon and carbon in the silicon-based particles is 1:1 to 2.5.
  • the negative pole sheet of the present application includes silicon-based particles having the above-mentioned atomic ratio of elements, and a lithium-ion battery with good expansion performance and cycle performance can be obtained.
  • the present application has no limitation on the preparation method of the silicon-based composite material, as long as the purpose of the present application can be achieved.
  • organic matter is carbonized to obtain a porous carbon matrix, and then the porous carbon matrix is placed in a silicon-containing gas atmosphere, and then heat-treated to obtain a silicon-based composite material.
  • the following preparation method can be used:
  • the porous carbon matrix is placed in a rotary furnace, and the furnace tube is purged with nitrogen gas for 20 to 40 minutes at room temperature, and then the temperature of the porous carbon matrix sample is increased to 450°C to 500°C.
  • the nitrogen flow rate was adjusted so that the gas residence time in the rotary kiln was at least 90 seconds and maintained at this flow rate for about 30 minutes. Then the gas supply is switched from nitrogen to a mixed gas of silicon-containing gas and nitrogen (the volume fraction of silicon-containing gas in the mixed gas is 5% to 30%).
  • the type of the porous carbon matrix is not particularly limited, as long as the purpose of the application can be achieved, for example, the porous carbon matrix can be selected from at least one of hard carbon, soft carbon, and graphite.
  • the aforementioned hard carbon may include resinous carbon, carbon black, organic polymer pyrolytic carbon, and combinations thereof.
  • the aforementioned soft carbon may include carbon fibers, carbon microspheres, and combinations thereof.
  • the particle size of the porous carbon matrix is not limited, as long as the purpose of the present application can be achieved.
  • the particle size range of the porous carbon matrix is 3 ⁇ m ⁇ Dv50 ⁇ 15 ⁇ m, and 15 ⁇ m ⁇ Dv99 ⁇ 30 ⁇ m.
  • the difference B% between the maximum and minimum values of the relative percentage of silicon atoms in silicon-based particles is related to the uniformity and size of the pore distribution inside the carbon matrix, for example, the more uniform the pore distribution inside the carbon matrix, the smaller the B% . Based on this, B% can be adjusted by adjusting the pore distribution and pore size.
  • the mass content C% of silicon in the negative electrode material layer is related to the amount of silicon-based composite material added, wherein the silicon content deposited inside the silicon-based composite material can be adjusted by adjusting the deposition temperature, deposition time and the concentration of silicon-containing gas For example, C% generally increases with the increase of deposition temperature, C% generally increases with the increase of deposition time, and C% generally increases with the concentration of silicon-containing gas. Based on this, the mass content C% of the silicon element in the negative electrode material layer can be adjusted.
  • the maximum particle size Dmax of silicon-based particles is positively correlated with the particle size of the porous carbon matrix. Based on this, the maximum particle size Dmax of silicon-based particles can be adjusted by sieving the porous carbon matrix.
  • the porosity of the negative electrode sheet usually decreases with the increase of the compaction density of the negative electrode sheet. Based on this, the compaction density of the negative electrode sheet can be adjusted by adjusting the cold pressing pressure of the negative electrode sheet, thereby adjusting the porosity of the negative electrode sheet Rate.
  • the atomic ratio of silicon element and carbon element in silicon-based particles can be adjusted by adjusting the ratio of silicon-containing gas and nitrogen gas in the mixed gas. Usually, as the proportion of silicon-containing gas in the mixed gas increases, more silicon will be deposited in the porous carbon matrix, which will increase the atomic ratio of silicon to carbon in the silicon-based particles.
  • the negative electrode sheet includes a negative electrode current collector, and the negative electrode material layer may be disposed on one or both surfaces along the thickness direction of the negative electrode current collector.
  • the "surface" here may be the entire area of the negative electrode collector, or a partial area of the negative electrode collector.
  • This application is not particularly limited, as long as the purpose of this application can be achieved.
  • the present application has no special restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, it may include but not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite collector fluid etc.
  • the thickness of the current collector of the negative electrode there is no particular limitation on the thickness of the current collector of the negative electrode, as long as the purpose of the present application can be achieved, for example, the thickness is 4 ⁇ m to 12 ⁇ m.
  • the thickness of the negative electrode material layer of the present application may be 70 ⁇ m to 120 ⁇ m.
  • the negative electrode material layer may include other negative electrode active materials known in the art in addition to the above-mentioned silicon-based composite materials, for example, may include but not limited to natural graphite, artificial graphite, mesophase micro carbon spheres, hard Carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 or Li with spinel structure - at least one of Al alloys.
  • the negative electrode material layer may also include a negative electrode conductive agent.
  • This application has no special restrictions on the negative electrode conductive agent, as long as the purpose of this application can be achieved, for example, it may include but not limited to carbon-based materials, metal-based materials or at least one of conductive polymers.
  • the above-mentioned carbon-based material is at least one selected from natural graphite, artificial graphite, conductive carbon black, acetylene black, Ketjen black or carbon fiber.
  • the above-mentioned metal-based material may include but not limited to metal powder and/or metal fiber, specifically, the metal may include but not limited to at least one of copper, nickel, aluminum or silver.
  • the conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole.
  • the negative electrode material layer may also include a negative electrode binder.
  • the present application has no special restrictions on the negative electrode binder, as long as the purpose of the application can be achieved, for example, it may include but not limited to polyvinyl alcohol, carboxymethyl Cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, At least one of polyvinylidene fluoride, polyethylene, polypropylene, polyacrylic acid, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon.
  • the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer.
  • the present application has no particular limitation on the composition of the conductive layer, which may be a commonly used conductive layer in the field, and the conductive layer may include but not limited to the above-mentioned negative electrode conductive agent and the above-mentioned negative electrode binder.
  • the electrolyte of the present application may also include lithium salts and other non-aqueous solvents.
  • the present application has no special restrictions on lithium salts, as long as the purpose of the present application can be achieved, for example, it may include but not limited to LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or lithium difluoroborate at least one of .
  • the lithium salt comprises LiPF 6 .
  • the present application has no special restrictions on other non-aqueous solvents, as long as the purpose of the present application can be achieved, for example, it may include but not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • the above-mentioned carbonate compound may include but not limited to at least one of chain carbonate compound, cyclic carbonate compound or fluorocarbonate compound.
  • Above-mentioned chain carbonate compound can include but not limited to dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC) or at least one of methyl ethyl carbonate (MEC).
  • the aforementioned cyclic carbonate may include, but is not limited to, at least one of butylene carbonate (BC) or vinylethylene carbonate (VEC).
  • Fluorocarbonate compounds may include, but are not limited to, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1, 2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate At least one of ester, 1,1,2-trifluoro-2-methylethylene carbonate or trifluoromethylethylene carbonate.
  • carboxylate compounds may include but are not limited to methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyl At least one of lactone, decanolactone, valerolactone or caprolactone.
  • the aforementioned ether compounds may include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1- At least one of ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • the above-mentioned other organic solvents may include but not limited to dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2- At least one of pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.
  • the content of other non-aqueous solvents is not particularly limited, as long as the purpose of the application can be achieved, for example, the mass percentage of other non-aqueous solvents mentioned above is 67% to 87%, such as 67%, 67.5%, 70% %, 75%, 80%, 83%, 85%, 86.5%, 87%, or any range therebetween.
  • the electrochemical device of the present application may also include a positive pole piece.
  • the present application has no special limitation on the positive pole piece, as long as the purpose of the application can be achieved.
  • the positive pole piece usually includes a positive electrode current collector and a positive electrode material layer.
  • the positive electrode material layer may be provided on one surface in the thickness direction of the positive electrode current collector, or on both surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface” here may refer to the entire area of the positive electrode collector or a partial area of the positive electrode collector. This application is not particularly limited, as long as the purpose of this application can be achieved.
  • the positive electrode current collector is not particularly limited, as long as the purpose of the present application can be achieved, for example, it may include but not limited to aluminum foil, aluminum alloy foil, or a composite current collector.
  • the thickness of the positive electrode collector there is no particular limitation on the thickness of the positive electrode collector, as long as the purpose of the present application can be achieved, for example, the thickness is 8 ⁇ m to 12 ⁇ m.
  • the positive electrode material layer includes the positive electrode active material, and the present application has no special limitation on the positive electrode active material, as long as the purpose of the application can be achieved, for example, at least one of the composite oxides of lithium or transition metal elements can be included .
  • the present application has no particular limitation on the above transition metal elements, as long as the purpose of the present application can be achieved, for example, at least one of nickel, manganese, cobalt or iron may be included.
  • the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganate, lithium manganese iron phosphate, or lithium titanate. kind.
  • the positive electrode material layer may also include a positive electrode conductive agent, and the present application has no special restrictions on the positive electrode conductive agent, as long as the purpose of the application can be achieved, for example, it may include but not limited to conductive carbon black (Super P), carbon At least one of nanotubes (CNTs), carbon fibers, acetylene black, flake graphite, Ketjen black, graphene, metal materials or conductive polymers.
  • the positive electrode conductive agent includes conductive carbon black and carbon nanotubes.
  • the aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the aforementioned carbon fibers may include, but are not limited to, vapor grown carbon fibers (VGCF) and/or carbon nanofibers.
  • the above metal material may include but not limited to metal powder and/or metal fiber, specifically, the metal may include but not limited to at least one of copper, nickel, aluminum or silver.
  • the aforementioned conductive polymer may include but not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.
  • the positive electrode material layer may also include a positive electrode binder. This application has no special restrictions on the positive electrode binder, as long as the purpose of this application can be achieved. For example, it may include but not limited to fluorine-containing resin, polypropylene resin, At least one of fiber type adhesive, rubber type adhesive or polyimide type adhesive.
  • the positive electrode sheet may further include a conductive layer located between the positive electrode current collector and the positive electrode material layer.
  • the present application has no particular limitation on the composition of the conductive layer, which may be a commonly used conductive layer in the field, for example, may include but not limited to the above-mentioned positive electrode conductive agent and the above-mentioned positive electrode binder.
  • the electrochemical device of the present application may also include a separator, and the present application has no particular limitation on the separator, as long as the purpose of the present application can be achieved.
  • the above-mentioned isolation film may include a base material layer and a surface treatment layer.
  • the present application has no special limitation on the base material layer, for example, it may include but not limited to polyethylene, polypropylene, polytetrafluoroethylene-based polyolefin isolation film, polyester Film (e.g.
  • the separator of the present application may have a porous structure, and the pore size is not particularly limited as long as the purpose of the present application can be achieved, for example, the pore size may be 0.01 ⁇ m to 1 ⁇ m.
  • the thickness of the isolation film is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness may be 5 ⁇ m to 500 ⁇ m.
  • At least one surface of the substrate layer is provided with a surface treatment layer.
  • the application has no special limitation on the surface treatment layer. It can be a polymer layer or an inorganic layer, or a layer made of a mixed polymer and an inorganic material. formed layer.
  • the inorganic material layer may include but not limited to inorganic particles and inorganic material layer binder, and the present application has no special limitation on inorganic particles, for example, may include but not limited to aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, At least one of tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.
  • the present application has no particular limitation on the inorganic layer binder, for example, it may include but not limited to polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, At least one of polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • polyvinylidene fluoride copolymer of vinylidene fluoride-hexafluoropropylene
  • polyamide polyacrylonitrile
  • polyacrylate polyacrylic acid
  • Polymers are contained in the polymer layer, and the present application has no special limitation on polymers, and the materials of polymers may include but not limited to polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidine At least one of ketone, polyvinyl ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).
  • electrochemical device of the present application is not particularly limited, and it may include any device that undergoes an electrochemical reaction.
  • electrochemical devices may include, but are not limited to, lithium-ion batteries.
  • the preparation process of electrochemical devices is well known to those skilled in the art, and the present application is not particularly limited.
  • it may include but not limited to the following steps: stack the positive electrode sheet, separator and negative electrode sheet in sequence, and as required Winding, folding and other operations to obtain the electrode assembly with a winding structure, put the electrode assembly into the packaging bag, inject the electrolyte into the packaging bag and seal it, and obtain an electrochemical device; or, put the positive electrode sheet, separator and negative electrode
  • the pole pieces are stacked in order, and then the four corners of the entire laminated structure are fixed with adhesive tape to obtain the electrode assembly of the laminated structure.
  • the electrode assembly is placed in the packaging bag, and the electrolyte is injected into the packaging bag and sealed to obtain an electrochemical device.
  • overcurrent prevention elements, guide plates, etc. can also be placed in the packaging bag as needed, so as to prevent pressure rise and overcharge and discharge inside the electrochemical device.
  • a second aspect of the present application provides an electronic device, which includes the electrochemical device in any one of the foregoing embodiments.
  • the electrochemical device provided by the application has good expansion performance and cycle performance, so that the electronic device provided by the application has a long service life.
  • the electronic device of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the current collector is punched out into a test sample with a width of 15 mm and a length of 70 mm with a punching machine. Fix the sample to the test fixture of the high-speed rail tensile machine to test the tensile strength of the sample, the tensile speed is 5mm/min, and the standard distance between the two fixtures of the tensile machine is 50mm. Record the tensile strength and displacement curves, and the sudden drop point of the tensile strength is the strength against external force damage.
  • the starting point and end point of the line scan data in Figure 1b correspond to the starting point and end point of the black arrow line in Figure 1a
  • the line scan data in Figure 1b is the The middle black arrow line passes through the data corresponding to the position.
  • the fluctuation value of silicon element is the difference between the highest value and the lowest value of the relative percentage content of silicon atoms in the whole line scan.
  • the lithium-ion battery After the lithium-ion battery is discharged to 0% state of charge (SOC), it is centrifuged, and the liquid obtained after centrifugation is tested by (gas chromatography mass spectrometry) GC-MS, and the mass content percentage of the FEC component in the electrolyte is detected.
  • SOC state of charge
  • GC-MS gas chromatography mass spectrometry
  • Lithium-ion battery room temperature cycle performance test
  • the test temperature is 25°C
  • the lithium-ion battery is charged at a constant current of 0.7 times (C) to 4.45V, then charged at a constant voltage to 0.025C, and then discharged to 3.0V at 0.5C after standing for 5 minutes.
  • the capacity obtained in this step is taken as the initial discharge capacity, and the cycle test of 0.7C charge/0.5C discharge is carried out for 400 cycles, and the discharge capacity of the 400th cycle is recorded.
  • Cycle capacity retention (discharge capacity at the 400th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • Lithium-ion battery low temperature cycle performance test
  • Lithium-ion battery -10°C discharge capacity retention (%) discharge capacity at -10°C/discharge capacity at 25°C ⁇ 100%.
  • the porous carbon substrate with a Dmax of 25 ⁇ m was placed in a rotary furnace, and the furnace tube was purged with nitrogen for 30 minutes at room temperature, and then the heating temperature of the porous carbon sample was increased to 450 °C.
  • the nitrogen flow rate was adjusted so that the gas residence time in the rotary kiln was at least 90 seconds and maintained at this flow rate for 30 minutes. Then the gas supply is switched from nitrogen to a mixed gas of silicon-containing gas (such as silane) and nitrogen, wherein the volume ratio of silicon-containing gas and nitrogen in the mixed gas is 5:95.
  • the silicon-based composite material prepared above, graphite particles and nano conductive carbon black are mixed according to the mass ratio of 3:94:3 to obtain the first mixture; the first mixture and the binder polyacrylic acid (PAA) are mixed according to the mass ratio of 95: 5 Adding deionized water to prepare a slurry with a solid content of 70wt%, and stirring evenly to obtain the first mixed slurry;
  • PAA binder polyacrylic acid
  • the first mixed slurry is uniformly coated on one surface of the negative electrode current collector copper foil with a thickness of 8 ⁇ m, and dried in vacuum at 85°C for 12 hours to obtain a negative electrode sheet coated with negative active material on one side Then, repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet coated with negative active materials on both sides; then cold press, slit, and cut the negative electrode sheet obtained above to obtain specifications It is a 76mm ⁇ 867mm negative pole piece.
  • the thickness of the negative electrode sheet is 90mm, and the porosity is 33%.
  • the positive electrode active material lithium cobaltate, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 95:2.5:2.5, NMP was added as a solvent, and a slurry with a solid content of 75wt% was prepared and stirred evenly.
  • the slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 ⁇ m, and dried at 90° C. to obtain a positive electrode sheet with a coating thickness of 110 ⁇ m.
  • the single-side coating of the positive electrode sheet is completed.
  • the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with positive active materials on both sides.
  • a positive electrode sheet with a specification of 74mm ⁇ 851mm was obtained.
  • ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of 1:1:1 as a base solvent, Add LiPF 6 and stir evenly to obtain an electrolyte solution, wherein the mass percentage of LiPF 6 is 12.5 wt%.
  • PE polyethylene
  • the above prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode and the negative electrode to play the role of isolation, and the electrode assembly is obtained by winding.
  • Put the electrode assembly in an aluminum-plastic film packaging bag inject electrolyte after drying, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, chemical formation, degassing, and edge trimming.
  • Example 1-1 In addition to adjusting the strength A of the negative electrode current collector as shown in Table 1, the difference B% between the maximum value and the minimum value of the relative percentage content of silicon atoms in the silicon-based particles, and the mass content C% of silicon in the negative electrode material layer, The rest are the same as in Example 1-1.
  • Example 1-1 Except that ⁇ preparation of electrolytic solution> is different from Example 1-1, the rest is the same as Example 1-1.
  • ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of 1:1:1 as a base solvent, Add LiPF 6 and fluoroethylene carbonate, and stir evenly to obtain an electrolyte, wherein the mass percentage of LiPF 6 is 12.5 wt%, and the mass percentage of fluoroethylene carbonate is shown in Table 4.
  • Example 1-1 In addition to adjusting the strength A of the negative electrode current collector as shown in Table 1, the difference B% between the maximum value and the minimum value of the relative percentage content of silicon atoms in the silicon-based particles, and the mass content C% of silicon in the negative electrode material layer, The rest are the same as in Example 1-1.
  • the cycle performance and expansion performance of the lithium-ion battery are improved.
  • the thickness H of one side of the negative electrode material layer and the maximum particle size Dmax of the silicon-based particles will also affect the performance of the lithium-ion battery. It can be seen from Examples 1-6, 2-1 to 2-9 that when H and Dmax satisfy H ⁇ 3 ⁇ Dmax, the lithium-ion battery has good cycle performance and expansion performance.
  • the performance of the lithium-ion battery will also be affected by the synergistic effect of the porosity P% of the negative electrode sheet and the mass content C% of silicon in the negative electrode material layer. From Example 2-3, Example 3-1 to Example 3-9, it can be seen that when P and C satisfy: P>15 ⁇ C 1/4 , the lithium-ion battery has good room temperature cycle performance and expansion performance and low-temperature cycle performance.
  • Example 4-1 to Example 4-4 it can be seen that when Q and C satisfy: 0.3 ⁇ C/Q ⁇ 3, the lithium-ion battery has good room temperature cycle performance, expansion performance and Low temperature cycle performance.

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Abstract

本申请提供了一种电化学装置和电子装置，包括正极极片、负极极片和电解液，负极极片包括负极集流体和负极材料层，负极材料层包括硅基复合材料，硅基复合材料包括硅基颗粒，负极集流体的强度为A MPa，硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值为B％，负极材料层中硅元素的质量含量为C％，满足：aa 本申请通过协同调整A、B、C满足上述条件，得到的锂离子电池具有良好循环性能和膨胀性能。

Description

一种电化学装置和电子装置 技术领域
本申请涉及电化学技术领域，具体涉及一种电化学装置和电子装置。
背景技术
锂离子电池具有体积和质量能量密度大、循环寿命长、标称电压高、自放电率低、体积小、重量轻等许多优点，在消费电子领域具有广泛的应用。随着近年来电动汽车和可移动电子设备的高速发展，人们对电池的能量密度、安全性、循环性能等相关需求越来越高，期待着综合性能全面提升的新型锂离子电池的出现。
硅材料具有高的比容量，作为锂离子电池的负极材料能够显著提升锂离子电池的能量密度。但是其在脱嵌锂过程中存在较大的体积膨胀和收缩，使其在循环中固体电解质界面膜(SEI)反复破坏和生成，消耗可逆锂，影响锂离子电池的循环性能和膨胀性能。
发明内容
本申请的目的在于提供一种电化学装置和电子装置，以提高锂离子电池的循环性能和膨胀性能。具体技术方案如下：
本申请的第一方面提供了一种电化学装置，包括正极极片、负极极片和电解液，所述负极极片包括负极集流体和负极材料层，其中所述负极材料层包括硅基复合材料，所述硅基复合材料包括硅基颗粒，所述负极集流体的强度为A MPa，所述硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值为B％，所述负极材料层中硅元素的质量含量为C％，满足：
Figure PCTCN2021141475-appb-000001
本申请通过协同调整A、B、C满足上述条件，能够得到具有良好循环性能和膨胀性能的锂离子电池。
在本申请的一种实施方案中，B满足：10≤B≤16。通过调整B在上述范围内，能够得到硅元素分布均一程度好的硅基颗粒，有利于降低锂离子电池膨胀产生的应力，从而得到具有良好循环性能和膨胀性能的锂离子电池。
在本申请的一种实施方案中，C满足：1≤C≤20。通过调整C在上述范围内，能够平衡锂离子电池的膨胀性能和能量密度。
在本申请的一种实施方案中，A满足：370≤A≤800。通过调整A在上述范围内，有利 于平衡锂离子电池的膨胀性能和生产成本。
在本申请的一种实施方案中，负极材料层的单面厚度为H，所述硅基颗粒的粒径最大值为Dmax，满足：H≥3×Dmax。通过调整H和Dmax之间满足上述关系，能够改善锂离子电池的循环性能和膨胀性能。
在本申请的一种实施方案中，硅基颗粒的Dmax满足：10μm≤Dmax≤25μm。通过调整Dmax在上述范围内，有利于平衡锂离子电池的加工性能、膨胀性能以及能量密度。
在本申请的一种实施方案中，负极材料层的单面厚度H满足：30μm≤H≤90μm。通过调整负极材料层的单面厚度H在上述范围，能够平衡负极材料层的强度和韧性，从而提高锂离子电池的性能。
在本申请的一种实施方案中，负极极片的孔隙率为P％，所述P与所述C满足：P>15×C 1/4。通过调整P与C满足上述关系，锂离子电池的膨胀性能和动力学性能得到提高。
在本申请的一种实施方案中，本申请的一种实施方案中，P满足：18≤P≤40。通过调整P在上述范围内，能够使负极极片能够在电解液中得到有效浸润，负极极片具有良好的强度，从而锂离子电池的膨胀性能和动力学性能得到提高。
在本申请的一种实施方案中，所述电解液包括氟代碳酸乙烯酯，基于所述电解液的质量，所述氟代碳酸乙烯酯的质量百分含量为Q％，所述Q与所述C满足：0.3≤C/Q≤3。通过调整Q与C满足上述关系，能够得到具有良好膨胀性能和动力学性能的锂离子电池。
在本申请的一种实施方案中，本申请的一种实施方案中，Q满足：1≤Q≤20。通过调整Q在上述范围内，有利于锂离子电池循环性能的提升。
本申请的一种实施方案中，硅基颗粒中包括硅元素和碳元素，所述硅基颗粒中硅、碳的原子比为1︰1至2.5。本申请的负极极片中包括具有上述元素原子比的硅基颗粒，能够得到具有良好膨胀性能和循环性能的锂离子电池。
本申请的第二方面提供了一种电子装置，其包括上述第一方面所述的电化学装置。
本申请提供一种电化学装置和电子装置，包括正极极片、负极极片和电解液，负极极片包括负极集流体和负极材料层，负极材料层包括硅基复合材料，硅基复合材料包括硅基颗粒，负极集流体的强度为A MPa，硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值为B％，负极材料层中硅元素的质量含量为C％，满足：
Figure PCTCN2021141475-appb-000002
通过协同调整A、B、C满足上述条件，得到的锂离子电池具有良好循环性能和膨胀 性能。当然，实施本申请的任一实施方案并不一定需要同时达到以上所述的所有优点。
附图说明
为了更清楚地说明本申请和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1a为硅基颗粒断面扫描电子显微镜(SEM)图；
图1b为X射线能谱仪(EDS)线扫中硅原子相对百分比含量的波动曲线。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他技术方案，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
现有技术中，为了改善硅负极的嵌锂膨胀问题，主要通过硅纳米化以及复合化实现。例如，通过降低硅材料的粒径至纳米级别，缓解其嵌锂时产生的应力，减少材料的破裂；或者通过其他碳质材料复合，减少其与电解质的接触，减少固体电解质界面(SEI)的产生。但是，硅纳米化方法存在制备工艺复杂、能耗高的问题，且纳米硅材料过高的比表面使其极其容易产生团聚，影响锂离子电池的电性能发挥；现有复合化方法由于仅单纯地针对碳质复合材料改进，而忽略了其他因素整体对锂离子电池膨胀的影响，因而对锂离子电池膨胀性能和循环性能的改善具有局限性。另外，嵌锂产生体积膨胀是硅基材料的本征属性，仅仅依靠这些方案虽然在一定程度上可以改善硅负极膨胀，但却不足以使其满足工业化产品应用。
有鉴于此，本申请提供了一种电化学装置和电子装置，以提高锂离子电池的循环性能和膨胀性能。
本申请的第一方面提供了一种电化学装置，包括正极极片、负极极片和电解液，所述负极极片包括负极集流体和负极材料层，其中，所述负极材料层包括硅基复合材料，所述硅基复合材料包括硅基颗粒，所述负极集流体的强度为A MPa，所述硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值为B％，所述负极材料层中硅元素的质量含量为C％，满足：
Figure PCTCN2021141475-appb-000003
本申请发明人研究发现，硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％为一个波动值，该波动值可以表示硅基颗粒内硅元素分布的均一程度，波动值越大，硅元素分布均一程度越差。硅的嵌锂过程中会产生体积膨胀，该膨胀会从多个方向发生(例如沿锂离子电池长度方向、宽度方向和高度方向)，因此需要负极集流体有一定的强度来抵抗膨胀所带来的应力，从而抑制锂离子电池的变形。本申请发明人还发现，硅基颗粒内部硅元素分布越均一，膨胀所产生的应力越小；负极材料层中硅元素的含量越多，锂离子电池循环过程中的膨胀趋势则越大；随着硅基颗粒内硅元素分布波动程度以及负极材料层中硅元素的质量含量增加，对负极集流体强度的需求越高，但是当负极集流体超过一定强度时，对循环和膨胀性能的改善程度将大幅下降。基于上述发现，本申请通过协同调整A、B、C满足上述条件，能够得到具有良好循环性能和膨胀性能的锂离子电池。
本申请的一种实施方案中，B满足：10≤B≤16。通过调整B在上述范围内，能够得到硅元素分布均一程度好的硅基颗粒，有利于降低锂离子电池膨胀产生的应力，从而得到具有良好循环性能和膨胀性能的锂离子电池。
本申请的一种实施方案中，C满足：1≤C≤20。通过调整C在上述范围内，从而能够避免以下情况：负极材料层中硅元素的含量过少，可能会影响锂离子电池的能量密度；负极材料层中硅元素的含量过多，可能会加剧锂离子电池的膨胀趋势。由此，通过调整C在上述范围内，有利于平衡锂离子电池的能量密度和膨胀性能。
本申请的一种实施方案中，A满足：370≤A≤800。通过调整A在上述范围内，从而能够避免以下情况：负极集流体的强度过低，影响锂离子电池的膨胀性能；负极集流体的强度过高，一方面对循环和膨胀性能没有改善，另一方面集流体的生产成本大增。由此，通过调整A在上述范围内，有利于平衡锂离子电池的膨胀性能和生产成本。
本申请的一种实施方案中，负极材料层的单面厚度为H，所述硅基颗粒的粒径最大值为Dmax，满足：H≥3×Dmax。通过调整H和Dmax之间满足上述关系，能够改善锂离子电池的循环性能和膨胀性能。推测这可能是由于硅材料嵌锂产生较大的膨胀，当负极极片厚度一定时，硅基颗粒的Dmax过大容易导致极片膨胀不均匀，造成负极极片局部膨胀过大。此外，由于负极材料浆料分散过程中并不是完全均匀分散的理想情况，因此负极极片中可能出现部分硅基颗粒分散不均一的情况，如果硅基颗粒的Dmax过大容易导致负极极片出现凸点，影响负极极片外观和性能，从而影响锂离子的循环性能和膨胀性能。由此， 通过调整H和Dmax之间满足上述关系，能够得到具有良好循环性能和膨胀性能的锂离子电池。
可以理解的是，负极材料层可以在负极集流体的单面设置，即单面涂布，也可以在负极集流体的双面设置，即双面涂布。在一种示例中，假设负极极片整体厚度为h，负极集流体厚度为h1，当为双面涂布时，则H为：H＝(h-h1)/2；当为单面涂布时，则H为：H＝h-h1。
本申请的一种实施方案中，硅基颗粒的Dmax满足：10μm≤Dmax≤25μm。通过调整Dmax在上述范围内，从而能够避免以下情况：硅基颗粒的Dmax过大容易导致极片膨胀不均匀，且在加工过程中容易产生凸点问题，影响锂离子电池的界面和膨胀性能；硅基颗粒的Dmax过小导致比表面积过大，产生更多的SEI膜在负极表面堆积，增大膨胀趋势，并且在加工过程中需要更多的粘结剂才能达到粘结的效果，降低锂离子电池的能量密度。由此，本申请通过调整Dmax在上述范围内，有利于平衡锂离子电池的加工性能、膨胀性能以及能量密度。
本申请的一种实施方案中，负极材料层的单面厚度H满足：30μm≤H≤90μm。通过调整负极材料层的单面厚度H在上述范围，能够平衡负极材料层的强度和韧性，从而提高锂离子电池的性能。
本申请的一种实施方案中，负极极片的孔隙率为P％，所述P与所述C满足：P>15×C 1/4。通过调整P与C满足上述关系，锂离子电池的膨胀性能和动力学性能得到提高。推测这可能是由于硅基材料嵌锂后体积膨胀非常大(约300％)，巨大的体积效应容易导致负极极片易出现脱模、掉粉等问题，具有一定孔隙率的负极极片可有效缓解硅基材料的体积膨胀。但是，当负极极片孔隙率过低时，电解液难以充分浸润负极极片，增加锂离子的传输距离，影响锂离子电池的动力学性能。由此，通过调整P与C满足上述关系，能够得到具有良好膨胀性能和动力学性能的锂离子电池。
本申请的一种实施方案中，P满足：18≤P≤40。通过调整P在上述范围内，能够使负极极片能够在电解液中得到有效浸润，负极极片具有良好的强度，从而锂离子电池的膨胀性能和动力学性能得到提高。
本申请的一种实施方案中，所述电解液包括氟代碳酸乙烯酯(FEC)，基于所述电解液的质量，氟代碳酸乙烯酯的质量百分含量为Q％，所述Q与所述C满足：0.3≤C/Q≤3。通过调整Q与C满足上述关系，能够避免以下情况：当C/Q过高时，锂离子电池循环过程中的膨胀趋势增大，当C/Q过低时，由于FEC的添加会降低电解液中锂离子的迁移率， 影响锂离子电池的倍率性能。由此，通过调整Q与C满足上述关系，能够得到具有良好膨胀性能和动力学性能的锂离子电池。
本申请的一种实施方案中，Q满足：1≤Q≤20。氟代碳酸乙烯酯(FEC)是电解液中重要的成膜添加剂，其在锂离子电池循环过程中分解产生的SEI膜隔绝材料和电解液进一步的接触，减少锂离子的消耗，通过调整Q在上述范围内，有利于锂离子电池循环性能的提升。
本申请的一种实施方案中，硅基颗粒中包括硅元素和碳元素，所述硅基颗粒中硅、碳的原子比为1︰1至2.5。本申请的负极极片中包括具有上述元素原子比的硅基颗粒，能够得到具有良好膨胀性能和循环性能的锂离子电池。
本申请对硅基复合材料的制备方法没有限制，只要能够实现本申请目的即可。例如，将有机物进行碳化，得到多孔碳基体，再使多孔碳基体处于含硅的气体氛围中，然后进行热处理，得到硅基复合材料。在一种示例中，可以采用如下制备方法：
将多孔碳基体置于回转炉中，在室温下用氮气将炉管吹扫20至40分钟，然后将多孔碳基体样品的温度提高到450℃至500℃。调节氮气流速以使气体在回转炉中的停留时间至少为90秒，并以该流速维持30分钟左右。然后将气体供应从氮气切换为含硅气体和氮气的混合气体(混合气体中含硅气体的体积分数为5％至30％)。在200sccm至400sccm的气体流速下沉积8小时至16小时后，向回转炉中持续通氮气从炉中吹出含硅气体，再在氮气条件下将回转炉吹扫30分钟，然后在5小时至10小时内将回转炉冷却到室温。然后通过将气流从氮气转换为来自压缩空气源的空气，在1小时至2小时内将回转炉内的氮气逐渐转换为空气，得到硅基复合材料。
在本申请中，多孔碳基体的种类没有特别限制，只要能实现本申请的目的即可，例如多孔碳基体可以选自硬碳、软碳、石墨中的至少一种。示例性地，上述硬碳可以包括树脂碳、碳黑、有机聚合物热解碳及其组合。上述软碳可以包括碳纤维、碳微球及其组合。多孔碳基体的粒径没有限制，只要能实现本申请目的即可。例如，多孔碳基体的粒径范围为3μm<Dv50<15μm，15μm<Dv99<30μm。
硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％与碳基体内部孔隙分布的均一性以及孔径大小相关，例如，碳基体内部孔隙分布越均一则B％越小。基于此，可以通过调节孔隙分布和孔径大小，从而调整B％。
负极材料层中硅元素的质量含量C％与硅基复合材料的添加量相关，其中，硅基复合 材料内部沉积的硅含量可通过调节沉积温度、沉积时间以及使用含硅气体的浓度来进行调整，例如，C％通常随沉积温度的升高而增大、C％通常随沉积时间的增加而增大、C％通常随含硅气体的浓度升高而增加。基于此，可进行负极材料层中硅元素的质量含量C％的调整。
硅基颗粒的粒径最大值Dmax与多孔碳基体的粒径成正相关性，基于此，可以通过对多孔碳基体进行粒径筛分，从而调整硅基颗粒的粒径最大值Dmax。
负极极片的孔隙率通常随负极极片的压实密度增大而降低，基于此，可以通过调整负极极片的冷压压力，调节负极极片的压实密度，从而调整负极极片的孔隙率。
硅基颗粒中硅元素与碳元素的原子比可以通过调整混合气体中含硅气体与氮气的比例来进行调整。通常随着混合气体中含硅气体比例的增加，多孔碳基体中会沉积更多的硅元素，使硅基颗粒中硅元素与碳元素的原子比增大。
本申请中，负极极片包括负极集流体，负极材料层可以设置在沿负极集流体厚度方向的一个表面或两个表面上。需要说明，这里的“表面”可以是负极集流体的全部区域，也可以是负极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。本申请对负极集流体没有特别限制，只要能够实现本申请目的即可，例如，可以包括但不限于铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体等。在本申请中，对负极的集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如厚度为4μm至12μm。本申请的负极材料层的厚度可以为70μm至120μm。
在本申请中，负极材料层除了包括上述硅基复合材料以外，还可以包括本领域已知的其它负极活性材料，例如，可以包括但不限于天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12或Li-Al合金中的至少一种。
在本申请中，负极材料层中还可以包括负极导电剂，本申请对负极导电剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于基于碳的材料、基于金属的材料或导电聚合物中的至少一种。上述基于碳的材料选自天然石墨、人造石墨、导电碳黑、乙炔黑、科琴黑或碳纤维中的至少一种。上述基于金属的材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。
在本申请中，负极材料层中还可以包括负极粘结剂，本申请对负极粘结剂没有特别限 制，只要能够实现本申请目的即可，例如可以包括但不限于聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、聚丙烯酸、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙中的至少一种。
任选地，负极极片还可以包括导电层，导电层位于负极集流体和负极材料层之间。本申请对导电层的组成没有特别限制，可以是本领域常用的导电层，导电层可以包括但不限于上述负极导电剂和上述负极粘结剂。
本申请的电解液还可以包括锂盐和其它非水溶剂，本申请对锂盐没有特别限制，只要能实现本申请的目的即可，例如可以包括但不限于LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或者二氟硼酸锂中的至少一种。优选地，锂盐包括LiPF 6。
本申请对其它非水溶剂没有特别限制，只要能实现本申请的目的即可，例如可以包括但不限于碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述碳酸酯化合物可以包括但不限于链状碳酸酯化合物、环状碳酸酯化合物或氟代碳酸酯化合物中的至少一种。上述链状碳酸酯化合物可以包括但不限于碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)或碳酸甲乙酯(MEC)中的至少一种。上述环状碳酸酯可以包括但不限于碳酸亚丁酯(BC)或碳酸乙烯基亚乙酯(VEC)中的至少一种。氟代碳酸酯化合物可以包括但不限于碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯或碳酸三氟甲基亚乙酯中的至少一种。上述羧酸酯化合物可以包括但不限于甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯或己内酯中的至少一种。上述醚化合物可以包括但不限于二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、1-乙氧基-1-甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。上述其它有机溶剂可以包括但不限于二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯或磷酸三辛酯中的至少一种。所述其他非水溶剂的含量没有特别限制，只要能实现本申请的目的即可，例如，上述其它非水溶剂的质量百分含量为67％至87％，例如可以67％、67.5％、70％、75％、80％、83％、 85％、86.5％、87％或为其间的任意范围。
本申请的电化学装置还可以包括正极极片，本申请对正极极片没有特别限制，只要能实现本申请的目的即可，例如正极极片通常包括正极集流体和正极材料层。正极材料层可以设置于正极集流体厚度方向上的一个表面上，也可以设置于正极集流体厚度方向上的两个表面上。需要说明，这里的“表面”可以是正极集流体的全部区域，也可以是正极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。在本申请中，正极集流体没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于铝箔、铝合金箔或复合集流体等。在本申请中，对正极集流体的厚度没有特别限制，只要能够实现本申请目的即可，例如厚度为8μm至12μm。
在本申请中，正极材料层中包括正极活性材料，本申请对正极活性材料没有特别限制，只要能够实现本申请目的即可，例如可以包括锂或过渡金属元素的复合氧化物中的至少一种。本申请对上述过渡金属元素没有特别限制，只要能实现本申请的目的即可，例如可以包括镍、锰、钴或铁中的至少一种。具体的，正极活性材料可以包括镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
在本申请中，正极材料层中还可以包括正极导电剂，本申请对正极导电剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、乙炔黑、鳞片石墨、科琴黑、石墨烯、金属材料或导电聚合物中的至少一种，优选地，正极导电剂包括导电炭黑和碳纳米管。上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。上述碳纤维可以包括但不限于气相生长碳纤维(VGCF)和/或纳米碳纤维。上述金属材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。上述导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。在本申请中，正极材料层还可以包括正极粘结剂，本申请对正极粘结剂没有特别限制，只要能够实现本申请目的即可，例如可以包括但不限于含氟树脂、聚丙烯树脂、纤维型粘结剂、橡胶型粘结剂或聚酰亚胺型粘结剂中的至少一种。
任选地，正极极片还可以包括导电层，导电层位于正极集流体和正极材料层之间。本申请对导电层的组成没有特别限制，可以是本领域常用的导电层，例如可以包括但不限于上述正极导电剂和上述正极粘结剂。
本申请的电化学装置还可以包括隔离膜，本申请对隔离膜没有特别限制，只要能够实 现本申请目的即可。上述隔离膜可以包括基材层和表面处理层，本申请对基材层没有特别限制，例如可以包括但不限于聚乙烯、聚丙烯、聚四氟乙烯为主的聚烯烃类隔离膜、聚酯膜(例如聚对苯二甲酸二乙酯膜)、纤维素膜、聚酰亚胺膜、聚酰胺膜、氨纶、芳纶膜、织造膜、非织造膜(无纺布)、微孔膜、复合膜、隔膜纸、碾压膜或纺丝膜中的至少一种，优选为聚乙烯或聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电化学装置的稳定性。本申请的隔离膜可以具有多孔结构，孔径的尺寸没有特别限制，只要能实现本申请的目的即可，例如，孔径的尺寸可以为0.01μm至1μm。在本申请中，隔离膜的厚度没有特别限制，只要能实现本申请的目的即可，例如厚度可以为5μm至500μm。
在本申请中，上述基材层的至少一个表面上设置有表面处理层，本申请对表面处理层没有特别限制，可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。无机物层可以包括但不限于无机颗粒和无机物层粘结剂，本申请对无机颗粒没有特别限制，例如，可以包括但不限于氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。本申请对无机物层粘结剂没有特别限制，例如，可以包括但不限于聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。聚合物层中包含聚合物，本申请对聚合物没有特别限制，聚合物的材料可以包括但不限于聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请的电化学装置没有特别限制，其可以包括发生电化学反应的任何装置。在一些实施方案中，电化学装置可以包括但不限于锂离子电池。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制，例如，可以包括但不限于以下步骤：将正极极片、隔离膜和负极极片按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件，将电极组件放入包装袋内，将电解液注入包装袋并封口，得到电化学装置；或者，将正极极片、隔离膜和负极极片按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件，将电极组件置入包装袋内，将电解液注入包装袋并封口，得到电化学装置。此外，也可以根据需要将防过电流元件、导板等置于包装袋中，从而防止电化学装置内部的压力上升、过充放电。
本申请的第二方面提供了一种电子装置，其包括前述任一实施方案中的电化学装置。本申请提供的电化学装置具有良好的膨胀性能和循环性能，从而本申请提供的电子装置具 有较长的使用寿命。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
负极极片孔隙率测试：
采用气体置换法测试负极极片的孔隙率：采用同一模具冲切50片半径为d的负极极片，测量每片负极极片的厚度h，并将50片负极极片装入测试设备(AccuPycП1340)的样品杯中，在密闭的样品仓中采用氦气对负极极片进行填充，由此测得负极极片的真体积V，然后通过如下公式计算负极极片的孔隙率：P＝(1-V/πd 2×50×h)×100％。
集流体强度测试：
将集流体用冲切机冲切出宽15mm、长70mm的测试试样。将试样固定到高铁拉力机的测试夹具上测试试样的抗拉强度，拉伸速度5mm/min，拉力机两夹具中间标准距离为50mm。记录拉伸强度和位移曲线，拉伸强度突降点则为抵抗外力破坏的强度。
负极材料层中硅元素含量的测试：
将负极极片至于真空烘箱中100℃干燥24小时，用刀片刮下负极极片上的部分活性材料称量得质量M1，再将刮下的活性材料至于持续的空气气氛中800℃热处理，去除碳质材料，剩余的材料称量得质量M2，然后通过如下公式计算负极材料层中硅元素的含量：C＝0.467M2/M1×100％。
硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值测定：
将负极极片至于真空烘箱中100℃干燥24小时，在保护性气氛下(例如氮气)，采用聚焦离子束(FIB)将极片中的硅基颗粒加工成50nm至100nm的薄片，SEM图参考图1a，然后采用透射电子显微镜(TEM)设备中的X射线能谱仪(EDS)线扫测试硅基颗粒内硅原子相对百分比含量，测试结果参考图1b。线扫位置选取在硅基颗粒的内部的任意位置，例如，图1b的线扫数据的起点和终点对应的是图1a中黑色箭头线的起点和终点，则图1b的线扫数据是图1a中黑色箭头线经过位置所对应的数据。硅元素的波动值为整个线扫中硅原子相对百分比含量最高值和最低值的差值。
硅基颗粒的粒径最大值Dmax测定：
将负极极片采用离子抛光机垂直切开，在电子显微镜下随机抽取极片中的硅基颗粒20个以上，测试硅基颗粒的粒径，取随机抽取的颗粒中粒径的最大值为Dmax。
电解液中氟代碳酸乙烯酯(FEC)含量测定：
将锂离子电池放电至0％荷电状态(SOC)后离心，离心后得到的液体进行(气相色谱质谱法)GC-MS测试，检测出电解液中FEC组分的质量含量百分比。
锂离子电池常温循环性能测试：
测试温度为25℃，将锂离子电池以0.7倍率(C)恒流充电到4.45V，再恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此步得到的容量为初始放电容量，进行0.7C充电/0.5C放电的循环测试400圈，记录第400次循环的放电容量。循环容量保持率＝(第400次循环的放电容量/首次循环的放电容量)×100％。
锂离子电池低温循环性能测试：
在25℃下，将化成后的锂离子电池以0.2倍率(C)恒流充电至4.45V，再恒压充电至电流小于等于0.05C，之后静置30分钟，再以0.2C倍率恒流放电至3.0V，测试得到锂离子电池25℃0.2C倍率放电容量；
在25℃下，将锂离子电池以0.2C倍率恒流充电至4.45V，再恒压充电至电流小于等于0.05C；之后将电芯放置在-10℃环境中，静置60分钟，再以0.2C倍率恒流放电至3.0V，测试得到锂离子电池-10℃0.2C倍率放电容量。
锂离子电池-10℃放电容量保持率(％)＝-10℃下的放电容量/25℃下的放电容量×100％。
锂离子电池膨胀率测试：
在测试温度为25℃下，用螺旋千分尺测试锂离子电池在50％SOC下的厚度，记为H0，然后按照循环性能测试中的步骤循环至400圈时，测试锂离子电池在100％SOC下的厚度，记为H1。25℃循环膨胀率＝(H1-H0)/H0×100％。
实施例1-1
<硅基复合材料的制备>
将Dmax为25μm的多孔碳基体置于回转炉中，在室温下用氮气将炉管吹扫30分钟，然后将多孔碳样品的加热温度提高到450℃。调节氮气流速以使气体在回转炉中的停留时间至少为90秒，并以该流速维持30分钟。然后将气体供应从氮气切换为含硅气体(例如硅烷)和氮气的混合气体，其中混合气体中含硅气体和氮气的体积比为5︰95。在200sccm的气体流速下沉积8小时后，向回转炉中持续通氮气从炉中吹出含硅气体，再在氮气条件下将回转炉吹扫30分钟，然后在数小时(例如8小时)内将回转炉冷却到室温。然后通过将气流从氮气转换为来自压缩空气源的空气，在2小时内将回转炉内的氮气逐渐转换为空气，得到硅基复合材料，即硅基颗粒。经测定，该硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％如表1所示。
<负极极片的制备>
将上述制备得到的硅基复合材料、石墨颗粒和纳米导电炭黑按照质量比3︰94︰3混合，得到第一混合物；将第一混合物与粘结剂聚丙烯酸(PAA)按照质量比95︰5加入去离子水中，调配成为固含量为70wt％的浆料，并搅拌均匀得到第一混合浆料；
将第一混合浆料均匀涂覆在厚度为8μm的负极集流体铜箔的一个表面上，在真空干燥、85℃条件下经过12小时烘干，得到单面涂布负极活性材料的负极极片；然后，在该负极极片的另一个表面上重复以上步骤，即得到双面涂布负极活性材料的负极极片；然后将上述得到的负极极片进行冷压、分条、裁切得到规格为76mm×867mm负极极片。负极极片的厚度为90mm，孔隙率为33％。
<正极极片的制备>
将正极活性材料钴酸锂、导电炭黑、聚偏二氟乙烯(PVDF)按质量比95︰2.5︰2.5混合，加入NMP作为溶剂，调配成为固含量为75wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，90℃条件下烘干，得到涂层厚度为 110μm的正极极片。以上步骤完成后，即完成正极极片的单面涂布。之后，在该正极极片的另一个表面上重复以上步骤，即得到双面涂布正极活性材料的正极极片。然后经过冷压、裁切后得到规格为74mm×851mm正极极片。
<电解液的制备>
在含水量小于10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按质量比1∶1∶1均匀混合，作为基础溶剂，加入LiPF 6，搅拌均匀，获得电解液，其中LiPF 6的质量百分含量为12.5wt％。
<隔离膜的制备>
采用厚度为15μm的聚乙烯(PE)薄膜(Celgard公司提供)。
<锂离子电池的制备>
将上述制备得到的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极和负极中间已起到隔离的作用，卷绕得到电极组件。将电极组件置于铝塑膜包装袋中，干燥后注入电解液，经过真空封装、静置、化成、脱气、切边等工序得到锂离子电池。
实施例1-2至实施例1-14
除了如表1所示调整负极集流体的强度A、硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％、负极材料层中硅元素的质量含量C％以外，其余与实施例1-1相同。
实施例2-1至实施例2-9
除了如表2所示调整负极材料层的单面厚度H、硅基颗粒的粒径最大值Dmax以外，其余与实施例1-6相同。
实施例3-1至实施例3-9
除了如表3所示调整负极极片的孔隙率P％，以及调整负极材料层中硅元素的质量含量C％以外，其余与实施例2-3相同。
实施例4-1
除了<电解液的制备>与实施例1-1不同以外，其余与实施例1-1相同。
<电解液的制备>
在含水量小于10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按质量比1∶1∶1均匀混合，作为基础溶剂，加入LiPF 6和氟代碳酸 乙烯酯，搅拌均匀，获得电解液，其中LiPF 6的质量百分含量为12.5wt％，氟代碳酸乙烯酯的质量百分含量如表4所示。
实施例4-2至实施例4-4
除了如表4所示调整氟代碳酸乙烯酯的质量百分含量Q％以外，其余与实施例4-1相同。
对比例1-1至对比例1-4
除了如表1所示调整负极集流体的强度A、硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％、负极材料层中硅元素的质量含量C％以外，其余与实施例1-1相同。
表1
Figure PCTCN2021141475-appb-000004
从实施例1-1至实施例1-14、对比例1-1至对比例1-4可以看出，当负极集流体的强度A、硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值B％、负极材料层中硅元素的质量含量C％满足：
Figure PCTCN2021141475-appb-000005
锂离子电池的循环性能和膨胀性能得到提高。
表2
Figure PCTCN2021141475-appb-000006
负极材料层的单面厚度H、硅基颗粒的粒径最大值Dmax下也会对锂离子电池的性能产生影响。从实施例1-6、实施例2-1至实施例2-9可以看出，当H和Dmax满足H≥3×Dmax时，锂离子电池具有良好的循环性能和膨胀性能。
表3
Figure PCTCN2021141475-appb-000007
负极极片的孔隙率P％、负极材料层中硅元素的质量含量C％协同作用下也会对锂离子电池的性能产生影响。从实施例2-3、实施例3-1至实施例3-9可以看出，当P和C满足： P>15×C 1/4时，锂离子电池具有良好的常温循环性能、膨胀性能和低温循环性能。
表4
Figure PCTCN2021141475-appb-000008
负极材料层中硅元素的质量含量C％、电解液中氟代碳酸乙烯酯含量Q％协同作用下也会对锂离子电池的性能产生影响。从实施例3-5、实施例4-1至实施例4-4可以看出，当Q和C满足：0.3≤C/Q≤3时，锂离子电池具有良好的常温循环性能、膨胀性能和低温循环性能。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (13)

  1. 一种电化学装置，包括正极极片、负极极片和电解液，所述负极极片包括负极集流体和负极材料层，
    其中，所述负极材料层包括硅基复合材料，所述硅基复合材料包括硅基颗粒，所述负极集流体的强度为A MPa，所述硅基颗粒内硅原子相对百分比含量的最大值与最小值之间的差值为B％，所述负极材料层中硅元素的质量含量为C％，满足：
    Figure PCTCN2021141475-appb-100001
  2. 根据权利要求1所述的电化学装置，其中，所述B满足：10≤B≤16。
  3. 根据权利要求1所述的电化学装置，其中，所述C满足：1≤C≤20。
  4. 根据权利要求1所述的电化学装置，其中，所述A满足：370≤A≤800。
  5. 根据权利要求1所述的电化学装置，其中，所述负极材料层的单面厚度为H，所述硅基颗粒的粒径最大值为Dmax，满足：H≥3×Dmax。
  6. 根据权利要求5所述的电化学装置，其中，所述Dmax满足：10μm≤Dmax≤25μm。
  7. 根据权利要求5所述的电化学装置，其中，所述H满足：30μm≤H≤90μm。
  8. 根据权利要求1所述的电化学装置，其中，所述负极极片的孔隙率为P％，所述P与所述C满足：P>15×C 1/4。
  9. 根据权利要求1所述的电化学装置，其中，所述P满足：18≤P≤40。
  10. 根据权利要求1所述的电化学装置，其中，所述电解液包括氟代碳酸乙烯酯，基于所述电解液的质量，所述氟代碳酸乙烯酯的质量百分含量为Q％，所述Q与所述C满足：0.3≤C/Q≤3。
  11. 根据权利要求10所述的电化学装置，其中，所述Q满足：1≤Q≤20。
  12. 根据权利要求1所述的电化学装置，其中，所述硅基颗粒中包括硅元素和碳元素，所述硅基颗粒中硅元素、碳元素的原子比为1︰1至2.5。
  13. 一种电子装置，其包括权利要求1至12中任意一项所述的电化学装置。
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