WO2024050813A1 - 一种负极极片、包含该负极极片的电化学装置及电子装置 - Google Patents

一种负极极片、包含该负极极片的电化学装置及电子装置 Download PDF

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WO2024050813A1
WO2024050813A1 PCT/CN2022/118094 CN2022118094W WO2024050813A1 WO 2024050813 A1 WO2024050813 A1 WO 2024050813A1 CN 2022118094 W CN2022118094 W CN 2022118094W WO 2024050813 A1 WO2024050813 A1 WO 2024050813A1
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lithium
carbon
negative electrode
doped silicon
composite material
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PCT/CN2022/118094
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English (en)
French (fr)
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李鑫
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宁德新能源科技有限公司
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Priority to PCT/CN2022/118094 priority Critical patent/WO2024050813A1/zh
Priority to CN202280010959.6A priority patent/CN116806375A/zh
Publication of WO2024050813A1 publication Critical patent/WO2024050813A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/26—Aluminium-containing silicates, i.e. silico-aluminates
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 electrochemistry, and specifically to a negative electrode plate, an electrochemical device and an electronic device including the negative electrode plate.
  • Lithium-ion batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as electrical energy storage, mobile electronic equipment, electric vehicles, and aerospace equipment. As mobile electronic devices and electric vehicles enter a stage of rapid development, the market has put forward increasingly higher requirements for the energy density, safety, cycle performance and service life of lithium-ion batteries.
  • silicon material Since the theoretical gram capacity of silicon material is as high as 4200mAh/g, it is the anode material with the highest theoretical gram capacity currently known. At the same time, silicon materials are abundant in reserves and low in price. Therefore, silicon materials have broad application prospects in lithium-ion batteries. However, the silicon material will undergo a volume expansion of 120% to 300% during the process of deintercalating lithium, causing the silicon material to crack, shatter or even separate from the current collector, resulting in poor conductivity of the negative electrode and reducing the cycle performance of the lithium-ion battery.
  • the silicon material will form a solid electrolyte interface (SEI) film and a large amount of irreversible silicates during the first lithium insertion process, which consumes a large amount of lithium ions from the positive electrode sheet and the electrolyte, resulting in a low first Coulombic efficiency of the lithium-ion battery.
  • SEI solid electrolyte interface
  • the purpose of this application is to provide a negative electrode plate, an electrochemical device and an electronic device including the negative electrode plate, so as to improve the cycle performance and first Coulombic efficiency of the electrochemical device.
  • a first aspect of the application provides a negative electrode sheet, which includes a negative active material layer, the negative active material layer includes a negative active material, and the negative active material includes prelithiated carbon-doped silicon-oxygen composite material and graphite. ;
  • the X-ray diffraction pattern of the prelithiated carbon-doped silicon-oxygen composite material includes a diffraction peak corresponding to at least one of Li 2 SiO 3 , Li 2 Si 2 O 5 or Li 4 SiO 4 .
  • the prelithiated carbon-doped silicon-oxygen composite material includes carbon, silicon, oxygen, and lithium elements; based on the total mass of the pre-lithiated carbon-doped silicon-oxygen composite material, the lithium element
  • the mass percentage content of the silicon element is 2.5% to 12%
  • the mass percentage content of the silicon element is 45% to 65%
  • the mass percentage content of the carbon element is 1% to 10%.
  • the prelithiated carbon-doped silicon-oxygen composite material has a particle size distribution ranging from 0.3 ⁇ m to 33 ⁇ m, a Dv50 of 5.5 ⁇ m to 10 ⁇ m, and a Dv99 of 20 ⁇ m to 31 ⁇ m.
  • the prelithiated carbon-doped silicon-oxygen composite material has a powder conductivity of 2 S/cm to 30 S/cm.
  • the graphite includes at least one of natural graphite, artificial graphite, mesophase carbon microspheres, and the like. By selecting the above-mentioned graphite, it is beneficial to improve the cycle performance of the electrochemical device.
  • the mass ratio of the prelithiated carbon-doped silicon-oxygen composite material to the graphite is (3 to 7): (93 to 97).
  • a second aspect of the present application provides an electrochemical device, which includes a positive electrode piece, an electrolyte, and the negative electrode piece in any of the aforementioned embodiments.
  • the electrolyte includes an organic solvent
  • the organic solvent includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, propylene carbonate or At least one of ethyl propionate.
  • the electrolyte further includes a lithium salt
  • the lithium salt includes lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bistrifluoromethanesulfonyl imide, bis(fluorosulfonyl ) at least one of lithium imide, lithium bisoxaloborate or lithium difluoroxaloborate.
  • a third aspect of the present application provides a sub-device, which includes the electrochemical device in any of the preceding embodiments.
  • the negative active material layer of the negative electrode sheet includes prelithiated carbon-doped silicon-oxygen composite material and graphite, wherein the X-ray diffraction pattern of the pre-lithiated carbon-doped silicon-oxygen composite material includes Li 2 SiO 3 , Li 2 Si The diffraction peak corresponding to at least one of 2 O 5 or Li 4 SiO 4 .
  • the prelithiated carbon-doped silicon-oxygen composite material in the negative electrode sheet of the present application has Si-C bonds, which can inhibit the disproportionation of silicon and is beneficial to improving the cycle performance of the electrochemical device; at the same time, the silicon formed in advance due to prelithiation Lithium oxide can reduce the irreversible consumption of lithium ions and help improve the first Coulombic efficiency of electrochemical devices.
  • Figure 1 is an X-ray diffraction (XRD) pattern of the prelithiated carbon-doped silicon-oxygen composite material in Example 1-1;
  • Figure 2 is an X-ray energy spectrometer (EDS) spectrum of the prelithiated carbon-doped silicon-oxygen composite material in Example 1-1.
  • EDS X-ray energy spectrometer
  • a first aspect of the present application provides a negative electrode sheet, which includes a negative active material layer, the negative active material layer includes a negative active material, and the negative active material includes prelithiated carbon-doped silicon-oxygen composite material and graphite; wherein, the pre-lithiated carbon-doped silicon-oxygen composite material and graphite are provided;
  • the X-ray diffraction pattern of the lithiated carbon-doped silicon-oxygen composite material includes diffraction peaks corresponding to at least one of Li 2 SiO 3 , Li 2 Si 2 O 5 or Li 4 SiO 4 .
  • the negative electrode sheet provided by this application includes a negative active material layer.
  • the negative active material layer includes prelithiated carbon-doped silicon-oxygen composite material and graphite, wherein the X-ray diffraction pattern of the pre-lithiated carbon-doped silicon-oxygen composite material includes Li
  • the diffraction peak corresponding to at least one of 2 SiO 3 , Li 2 Si 2 O 5 or Li 4 SiO 4 can enable the negative active material layer to maintain a high gram capacity, and the prelithiated carbon-doped silicon-oxygen composite material
  • Carbon can improve the conductivity of the negative electrode piece, and a stable Si-C bond can be formed between carbon and silicon, which is beneficial to inhibit the disproportionation of silicon and alleviate the volume expansion of silicon, thereby improving the cycle performance of the electrochemical device; and due to the pre-heating
  • the silicate formed in advance by lithiation specifically at least one of Li 2 SiO 3 , Li 2 Si 2 O 5 or Li 4 SiO 4 lithium silicate,
  • the additional silicate formed reduces the irreversible consumption of lithium ions from the positive electrode sheet and the electrolyte, thereby helping to improve the first Coulombic efficiency of the electrochemical device.
  • the negative electrode piece provided by this application has good electrical conductivity. Applying the negative electrode piece provided by this application to an electrochemical device is beneficial to improving the cycle performance and first Coulombic efficiency of the electrochemical device.
  • the prelithiated carbon-doped silicon-oxygen composite material includes carbon, silicon, oxygen, and lithium elements; based on the total mass of the pre-lithiated carbon-doped silicon-oxygen composite material, the mass percentage of lithium element The content is 2.5% to 12%, the mass percentage of silicon is 45% to 65%, and the mass percentage of carbon is 1% to 10%; preferably, the mass percentage of lithium is 6% to 65%. 11%, the mass percentage of silicon is 55% to 65%, and the mass percentage of carbon is 1.5% to 5%.
  • the mass percentage of lithium element can be 2.5%, 5%, 7.5%, 10%, 12% or any two of the above numerical ranges; the mass percentage of silicon element can be 45%, 50%, 55%, 60%, 65% or any two of the above values; the mass percentage of carbon element can be 1%, 2%, 4%, 6%, 8%, 10% or any two of the above values range of composition.
  • the negative active material layer can maintain a high gram capacity.
  • Prelithiated carbon doped with carbon in the silicon-oxygen composite material can improve the performance of the negative electrode sheet.
  • Conductivity, and stable Si-C bonds can be formed between carbon and silicon, which is beneficial to inhibit the disproportionation of silicon to alleviate the volume expansion of silicon, thereby improving the cycle performance of the electrochemical device; and the above-mentioned silicon formed in advance due to pre-lithiation Lithium acid oxide can effectively reduce the additional silicate formed on the surface of the negative active material during the first discharge process, reduce the irreversible consumption of lithium ions from the positive electrode sheet and the electrolyte, thereby helping to improve the first Coulombic efficiency of the electrochemical device .
  • prelithiated carbon-doped silicon-oxygen composite materials usually contain some impurity elements with relatively low content (for example, the mass percentage is less than or equal to 0.1%).
  • This application is calculating the above-mentioned lithium element, silicon element, and carbon element.
  • the mass percentage of elements refers to the total mass obtained after excluding the above impurity elements, that is, in terms of lithium element, silicon element, carbon element, The total mass of oxygen element is used as the basis, and then the mass percentage content of lithium element, silicon element and carbon element is obtained.
  • the mass percentage content of oxygen element is 100% minus the mass percentage content of lithium element, silicon element and carbon element. Sum.
  • the prelithiated carbon-doped silicon-oxygen composite material has a particle size distribution ranging from 0.3 ⁇ m to 33 ⁇ m, a Dv50 of 5.5 ⁇ m to 10 ⁇ m, and a Dv99 of 20 ⁇ m to 31 ⁇ m.
  • the particle size distribution range can be any of 0.3 ⁇ m to 33 ⁇ m, 0.3 ⁇ m to 30 ⁇ m, 0.4 ⁇ m to 30 ⁇ m, 0.5 ⁇ m to 30 ⁇ m, 0.6 ⁇ m to 30 ⁇ m;
  • Dv50 can be 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m , 7.5 ⁇ m, 9 ⁇ m, 10 ⁇ m, or a range composed of any two of the above values;
  • Dv99 can be a range composed of any two of the above values, 20 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m, 31 ⁇ m.
  • the side reactions between the pre-lithiated carbon-doped silicon-oxygen composite material and the electrolyte can be reduced to alleviate
  • the volume change of the prelithiated carbon-doped silicon-oxygen composite material enhances the compressive strength of the pre-lithiated carbon-doped silicon-oxygen composite material, further increases the structural stability of the negative electrode plate, and thereby helps improve the cycle performance of the electrochemical device. .
  • Dv50 means that in the particle size distribution based on the volume of the material, measured from the smallest particle size, reaching 50% of the cumulative volume
  • Dv99 means that in the particle size distribution based on the volume of the material, measured from the small particle size, A particle size that reaches 99% of volume accumulation.
  • the prelithiated carbon-doped silicon-oxygen composite material has a powder conductivity of 2 S/cm to 30 S/cm.
  • the powder conductivity of the prelithiated carbon-doped silicon-oxygen composite material can be 2S/cm, 5S/cm, 10S/cm, 15S/cm, 20S/cm, 25S/cm, 30S/cm, or any two of the above A range of values.
  • the current density at the interface between the negative electrode sheet and the electrolyte can be effectively controlled, thereby mitigating the lithium evolution phenomenon of the negative electrode sheet, which is beneficial to Improve cycle performance of electrochemical devices.
  • the graphite includes at least one of natural graphite, artificial graphite, mesophase carbon microspheres, and the like. By selecting the above-mentioned graphite, it is beneficial to improve the cycle performance of the electrochemical device.
  • the mass ratio of the prelithiated carbon-doped silicon-oxygen composite material to graphite is (3 to 7): (93 to 97).
  • the mass ratio of the prelithiated carbon-doped silicon-oxygen composite material to the graphite can be 7:93, 6:94, 5:95, 4:96, 3:97, or any value between any two of the above numerical ranges.
  • One ratio By regulating the mass ratio of the prelithiated carbon-doped silicon-oxygen composite material to graphite within the above range, the negative active material layer can maintain a high gram capacity, while reducing the probability of direct contact between silicon and the electrolyte to reduce the risk of silicon and electrolyte contact.
  • the side reaction between the electrolyte and the formation of the SEI film alleviate the volume expansion of silicon, and graphite can increase the conductivity of the negative electrode sheet, which is beneficial to synergistically improving the cycle performance of the electrochemical device.
  • the negative active material layer may also include a conductive agent and a binder.
  • the conductive agent may include conductive carbon black (Super P), At least one of carbon nanotubes (CNTs), carbon fiber, flake graphite, Ketjen black or graphene.
  • This application has no special restrictions on the adhesive, as long as it can achieve the purpose of this application.
  • the adhesive may include polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, butyl fluoride, Styrene rubber (SBR), sodium alginate, polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyacrylonitrile, sodium carboxymethylcellulose (CMC-Na) or potassium carboxymethylcellulose (CMC- Ka) at least one.
  • SBR Styrene rubber
  • PVA polyvinyl alcohol
  • PTFE polytetrafluoroethylene
  • CMC-Na sodium carboxymethylcellulose
  • CMC- Ka potassium carboxymethylcellulose
  • the negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the above "negative active material layer disposed on at least one surface of the negative electrode current collector” means that the negative electrode active material layer can be provided on one surface of the negative electrode current collector along its own thickness direction, or can also be provided on the negative electrode current collector along its own thickness direction. direction on both surfaces.
  • the "surface” here can be the entire area of the negative electrode current collector, or it can be a partial area of the negative electrode current collector.
  • the negative electrode current collector can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector (such as Carbon-copper composite current collector, nickel-copper composite current collector, titanium-copper composite current collector, etc.).
  • This application has no special restrictions on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the application can be achieved.
  • the thickness of the negative electrode current collector is 6 ⁇ m to 12 ⁇ m, and the thickness of the negative electrode active material layer is 30 ⁇ m to 120 ⁇ m.
  • the application has no special restrictions on the thickness of the negative electrode piece, as long as the purpose of the application can be achieved.
  • the thickness of the negative electrode piece is 50 ⁇ m to 150 ⁇ m.
  • the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode active material layer.
  • a conductive layer located between the negative electrode current collector and the negative electrode active material layer.
  • This application has no particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in this field.
  • the conductive layer includes a conductive agent and a binder.
  • This application has no particular limitation on the conductive agent and the adhesive in the conductive layer.
  • it may be at least one of the above-mentioned conductive agent and the above-mentioned adhesive.
  • the prelithiated carbon-doped silicon-oxygen composite material is obtained by pre-lithiating the carbon-doped silicon-oxygen composite material.
  • the pre-lithiation treatment is to combine the carbon-doped silicon-oxygen composite material with lithium.
  • the source is subjected to heat treatment, wherein the temperature of the heat treatment is 400°C to 900°C, the temperature rise rate of the heat treatment is 1°C/min to 10°C/min, and the heat preservation time of the heat treatment is 1h to 6h.
  • the temperature of the heat treatment can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, or a range consisting of any two of the above values;
  • the heating rate of the heat treatment can be 1°C/min, 2°C/min, 4°C/min, 6°C/min, 8°C/min, 10°C/min or any two of the above values;
  • the heat treatment holding time can be 1h, 2h, 3h, 4h, 5h, 6h or any two of the above. A range of values.
  • the pre-lithiation treatment can be more sufficient and a sufficient amount of lithium silicate can be generated, which can effectively reduce the additional formation of lithium silicate on the surface of the negative active material during the first discharge process.
  • Silicates reduce the irreversible consumption of lithium ions from the positive electrode and the electrolyte, which is beneficial to improving the first Coulombic efficiency of the electrochemical device.
  • regulating the heat treatment temperature, heat treatment heating rate, and heat treatment holding time within the above range can effectively control the crystallization degree of silicon, reduce the expansion of silicon, and help improve the cycle performance of the electrochemical device.
  • the heat treatment temperature, heating rate and heat preservation time can be changed to control the lithium element content in the prelithiated carbon-doped silicon-oxygen composite material. For example, if the heat treatment temperature is increased, the lithium element content in the prelithiated carbon-doped silicon-oxygen composite material increases; if the heat treatment temperature is lowered, the lithium element content in the pre-lithiated carbon-doped silicon-oxygen composite material decreases. Increasing the heating rate, the lithium element content in the prelithiated carbon-doped silicon-oxygen composite material decreases; reducing the heating rate, the lithium element content in the pre-lithiated carbon-doped silicon-oxygen composite material increases.
  • the lithium element content will increase; if the heat treatment holding time is shortened, the lithium element content will decrease.
  • the contents of silicon, carbon, and oxygen elements in prelithiated carbon-doped silicon-oxygen composite materials mainly depend on the contents of silicon, carbon, and oxygen elements in carbon-doped silicon-oxygen composite materials. Changes in heat treatment conditions have different effects on silicon, carbon, and oxygen elements. Changes in oxygen content have a certain impact, but the impact is not significant.
  • Changing the heat treatment temperature, heating rate and heat preservation time can also regulate the particle size distribution range, Dv50 and Dv99 of the prelithiated carbon-doped silicon-oxygen composite material.
  • the particle size distribution range of the prelithiated carbon-doped silicon-oxygen composite material becomes wider, Dv50 increases, and Dv99 increases;
  • the heat treatment temperature is lowered, the particle size distribution range of the pre-lithiated carbon-doped silicon-oxygen composite material becomes wider. The range is narrowed, Dv50 is reduced, Dv99 is reduced.
  • the particle size distribution range of the prelithiated carbon-doped silicon-oxygen composite material becomes narrower, with Dv50 and Dv99 decreasing; decreasing the heating rate, the particle size distribution range of the pre-lithiated carbon-doped silicon-oxygen composite material becomes smaller. Width, Dv50 increases, Dv99 increases. Prolonging the heat treatment holding time, the particle size distribution range of the prelithiated carbon-doped silicon-oxygen composite material becomes wider, Dv50 increases, and Dv99 increases; shortening the heat treatment holding time, the particle size distribution range of the pre-lithiated carbon-doped silicon-oxygen composite material increases. The diameter distribution range becomes narrower, Dv50 decreases, and Dv99 decreases.
  • the preparation method of carbon-doped silicon-oxygen composite materials may include but is not limited to the following steps: combining silicon and The silica is mixed evenly and put into a vacuum deposition furnace. The temperature is controlled to 1300°C to 1350°C and the vacuum degree is 1Pa to 100Pa. An appropriate amount of carbon source gas (such as methane, acetylene, ethylene, etc.) is introduced to obtain carbon doping. Silicone composite materials.
  • the contents of carbon, silicon and oxygen elements in carbon-doped silicon-oxygen composites can be controlled by the mixing ratio of silicon and silicon dioxide and the content of the carbon source gas introduced, for example, the mixing ratio of silicon and silicon dioxide Increase, the content of silicon element increases, and the content of oxygen element decreases; the mixing ratio of silicon and silicon dioxide decreases, the content of silicon element decreases, and the content of oxygen element increases; the amount of carbon source gas introduced increases, and the content of carbon element increases ; The content of the introduced carbon source gas decreases, and the content of carbon element decreases.
  • the mass percentage of carbon element is 1% to 11.4%
  • the mass percentage of silicon element is 46.2% to 73.9%
  • the mass percentage of oxygen element is 1% to 11.4%.
  • the content is 14.7% to 52.8%.
  • carbon-doped silicon-oxygen composite materials usually contain some impurity elements with low content (for example, the mass percentage is less than or equal to 0.1%).
  • This application is calculating the mass of the above-mentioned carbon element, silicon element, and oxygen element.
  • percentage content “the total mass of the carbon-doped silicon-oxygen composite material” refers to the total mass obtained after excluding the above impurity elements, and then obtains the mass percentage content of carbon element, silicon element, and oxygen element.
  • the particle size distribution range of the carbon-doped silicon-oxygen composite material is 0.2 ⁇ m to 33 ⁇ m
  • Dv50 is 5 ⁇ m to 12 ⁇ m
  • Dv99 is 15 ⁇ m to 31 ⁇ m.
  • the particle size distribution range can be any of 0.2 ⁇ m to 33 ⁇ m, 0.3 ⁇ m to 33 ⁇ m, 0.3 ⁇ m to 30 ⁇ m, 0.4 ⁇ m to 30 ⁇ m, 0.5 ⁇ m to 30 ⁇ m, 0.6 ⁇ m to 30 ⁇ m
  • Dv50 can be 5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m or any two of the above values
  • Dv99 can be 15 ⁇ m, 17 ⁇ m, 20 ⁇ m, 22 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m, 31 ⁇ m or A range consisting of any two of the above values.
  • prelithiation is to "supplement lithium” to the negative electrode material in advance to offset the irreversible lithium loss caused by the formation of SEI film and silicate, thereby increasing the total capacity and first Coulombic efficiency of the battery.
  • this application does not specifically limit the lithium source used for "lithium supplementation” as long as it can achieve the purpose of this application.
  • it can include metallic lithium, lithium oxide, lithium hydride, lithium nitrate, lithium carbonate or silicon. At least one kind of lithium acid.
  • a second aspect of the present application provides an electrochemical device, which includes a positive electrode piece, an electrolyte, and the negative electrode piece in any of the aforementioned embodiments. Therefore, the electrochemical device provided by the present application has good cycle performance and first Coulombic efficiency.
  • the electrolyte includes an organic solvent
  • the organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dicarbonate At least one of methyl ester (DMC), propylene carbonate or ethyl propionate.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • DMC methyl ester
  • the mass percentage of the organic solvent is 5% to 80%, such as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or in between any range.
  • the electrolyte may also include other organic solvents.
  • This application has no special restrictions on other organic agents as long as they can achieve the purpose of this application.
  • it may include but is not limited to carbonate compounds, carboxylate compounds, ethers At least one of compounds or other organic solvents.
  • the above-mentioned carbonate compound may include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound or a fluorinated carbonate compound.
  • the above-mentioned chain carbonate compound may include, but is not limited to, at least one of dipropyl carbonate (DPC), methylpropyl carbonate (MPC) or ethylpropyl carbonate (EPC).
  • DPC dipropyl carbonate
  • MPC methylpropyl carbonate
  • EPC ethylpropyl carbonate
  • the above-mentioned cyclic carbonate may include, but is not limited to, at least one of butylene carbonate (BC) or vinyl ethylene carbonate (VEC).
  • the above-mentioned fluorocarbonate compounds may include, but are not limited to, fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-difluoroethylene carbonate.
  • Trifluoroethylene 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, At least one of 2-difluoro-1-methylethylene carbonate, 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, propyl propionate, ⁇ -butyrolactone, decane At least one of ester, valerolactone, mevalonolactone or caprolactone.
  • ether compounds may include, but are not limited to, glycol dimethyl ether, diglyme, tetraglyme, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane At least one of ring, 1,4-dioxane or 1,3-dioxane.
  • the above-mentioned other organic solvents may include, but are not limited to, ethyl vinyl sulfone, methyl isopropyl sulfone, isopropyl sec-butyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl -At least one of 2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate ester.
  • the mass percentage of the above-mentioned other organic solvents is 5% to 80%, such as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or to any range in between.
  • the electrolyte includes lithium salts, and the lithium salts include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), lithium bistrifluoromethanesulfonimide (LiN(CF 3 SO 2 ) 2 , LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO 2 F) 2 ), LiFSI), lithium bisoxalatoborate (LiB(C 2 O 4 ) 2 , LiBOB) or difluoride At least one of lithium oxalate borate (LiBF 2 (C 2 O 4 ), LiDFOB). Based on the quality of the electrolyte, the concentration of lithium salt is 0.5mol/L to 1.5mol/L.
  • the positive electrode sheet of the present application includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.
  • the above-mentioned "positive electrode active material layer provided on at least one surface of the positive electrode current collector” means that the positive electrode active material layer can be provided on one surface of the positive electrode current collector along its own thickness direction, or can also be provided on the positive electrode current collector along its own thickness direction. direction on both surfaces.
  • the "surface” here can be the entire area of the positive electrode current collector, or it can be a partial area of the positive electrode current collector. There is no particular limitation in this application, as long as the purpose of this application can be achieved. This application has no particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application.
  • the positive active material layer includes a positive active material.
  • the positive active material can include lithium nickel cobalt manganate (such as common NCM811, NCM622, NCM523, NCM111), at least one of lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO 2 ), lithium manganate, lithium iron manganese phosphate or lithium titanate.
  • the positive active material layer also includes a conductive agent and a binder.
  • This application has no particular restrictions on the types of the conductive agent and the binder, as long as the purpose of the application can be achieved.
  • it can be any of the above-mentioned conductive agent and the above-mentioned binder. of at least one.
  • This application has no special restrictions on the mass ratio of the cathode active material, conductive agent, and binder in the cathode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.
  • This application has no special restrictions on the thickness of the cathode current collector and the cathode material layer, as long as the purpose of this application can be achieved.
  • the thickness of the positive electrode current collector is 6 ⁇ m to 12 ⁇ m, and the thickness of the positive electrode material layer is 30 ⁇ m to 120 ⁇ m.
  • the application has no special restrictions on the thickness of the positive electrode piece, as long as the purpose of the application can be achieved.
  • the thickness of the positive electrode piece is 50 ⁇ m to 150 ⁇ m.
  • the positive electrode plate may further include a conductive layer located between the positive electrode current collector and the positive electrode material layer.
  • the composition of the conductive layer is not particularly limited and may be a conductive layer commonly used in this field.
  • the conductive layer includes conductive agent and adhesive. This application has no particular limitations on the conductive agent and the adhesive in the conductive layer. For example, it may be at least one of the above-mentioned conductive agent and the above-mentioned adhesive.
  • the electrochemical device also includes an isolation membrane.
  • the material of the isolation film may include polyethylene (PE), polypropylene (PP)-based polyolefin (PO) isolation film, polyester film (for example, distinguished by film type, including polyethylene terephthalate At least one of ester (PET) film), cellulose film, polyimide film (PI), polyamide film (PA), spandex or aramid film;
  • the type of isolation film may include woven film, non-woven film At least one of (non-woven fabric), microporous film, composite film, rolled film or spun film.
  • the isolation film may include a base material layer and a surface treatment layer.
  • the base material layer can be a non-woven fabric, film or composite film with a porous structure.
  • the material of the base material layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.
  • a surface treatment layer is provided on at least one surface of the base material layer.
  • the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are not particularly limited and may include, for example, aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, At least one of zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.
  • the binder is not particularly limited, and may be at least one of the above binders, for example.
  • the polymer layer contains a polymer, and the polymer material includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application also includes a packaging bag.
  • the packaging bag is not particularly limited in the present application and can be a packaging bag known in the art, as long as the purpose of the application can be achieved.
  • the electrochemical device of the present application is not particularly limited and may include any device that undergoes electrochemical reactions.
  • the electrochemical device may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, a lithium ion polymer secondary battery, and the like.
  • the preparation process of the electrochemical device of the present application is well known to those skilled in the art, and the present application is not particularly limited.
  • it may include but is not limited to the following steps: stacking the positive electrode sheet, the isolation film and the negative electrode sheet in order, And perform winding, folding and other operations as needed to obtain an electrode assembly with a rolled structure, put the electrode assembly into a packaging bag, inject the electrolyte into the packaging bag and seal it to obtain an electrochemical device; or, place the positive electrode piece and isolation
  • the membranes and negative electrode plates are stacked in order, and then the four corners of the entire lamination structure are fixed with tape to obtain the electrode assembly of the lamination structure.
  • the electrode assembly is placed in the packaging bag, and the electrolyte is injected into the packaging bag and sealed to obtain Electrochemical device.
  • overcurrent prevention components, guide plates, etc. can also be placed in the packaging bag as needed to prevent pressure rise inside the electrochemical device and overcharge and discharge.
  • a third aspect of the present application provides an electronic device, which includes the electrochemical device in any of the preceding embodiments. Therefore, the electronic device provided by the present application has good performance.
  • the electronic device of the present application is not particularly limited and may be used in any electronic device known in the art.
  • electronic devices may include, but are not limited to, laptop computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, Video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the sample powder of the prelithiated carbon-doped silicon-oxygen composite material in each embodiment or the negative active material other than graphite in the comparative example is placed on the sample stage of the XRD testing instrument, using a scanning rate of 2°/min and a scanning angle range of 10° to 80° to obtain the XRD diffraction pattern.
  • MDI Jade 6.0 conduct phase analysis on the characteristic peaks of the prelithiated carbon-doped silicon-oxygen composite materials in each embodiment or the negative active materials except graphite in the comparative examples to see whether there are Li 2 SiO 3 , Li The diffraction peak corresponding to 2 Si 2 O 5 or Li 4 SiO 4 .
  • TEM Transmission electron microscopy
  • Cycle capacity retention rate (%) of a lithium-ion battery (discharge capacity of the 500th cycle/discharge capacity of the first cycle) ⁇ 100%.
  • ED volumetric energy density
  • the carbon-doped silicon-oxygen composite material and the lithium source lithium hydride at a mass ratio of 10:1, add deionized water, and stir evenly to obtain composite material powder; in an argon atmosphere, mix the composite material powder at 3°C/min The heating rate is increased to 700°C and kept for 3 hours, the heat treatment is completed, and then repeatedly washed three times with deionized water and dried to obtain the prelithiated carbon-doped silicon-oxygen composite material.
  • the mass percentage content of carbon element in the carbon-doped silicon-oxygen composite material is 1.1%
  • the mass percentage content of silicon element is 60.2%
  • the mass percentage content of oxygen element is 38.7%.
  • the negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil with a thickness of 10 ⁇ m, and dried at 90°C to obtain a negative electrode sheet with a coating thickness of 100 ⁇ m and a negative electrode active material layer coated on one side.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • EP ethyl propionate
  • a porous polyethylene film with a thickness of 7 ⁇ m (provided by Celgard) was used.
  • the positive electrode piece, isolation film and negative electrode piece prepared above are stacked in order, so that the isolation film is between the positive electrode piece and the negative electrode piece to play an isolation role, and the electrode assembly is obtained by winding. Put the electrode assembly into an aluminum-plastic film packaging bag, remove the moisture at 80°C, inject the prepared electrolyte, and go through processes such as vacuum packaging, standing, formation, degassing, and trimming to obtain a lithium-ion battery.
  • Example 1-1 Except for adjusting relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.
  • Example 1-1 Except for adjusting relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.
  • Example 1-1 Except for adjusting relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.
  • the "element content” in Table 1 refers to the mass percentage of the corresponding element
  • the “negative active material” refers to the prelithiated carbon-doped silicon-oxygen composite material in each embodiment or other than graphite in the comparative example. Negative active material, "/" indicates that the corresponding parameter or substance does not exist.
  • Lithium silicate in Table 2 refers to at least one of Li 2 SiO 3 , Li 2 Si 2 O 5 or Li 4 SiO 4 .
  • “(Li 2 "SiO 3 +Li 4 SiO 4 )” means that the XRD pattern of the negative electrode active material in this embodiment contains the diffraction peaks of Li 2 SiO 3 and Li 4 SiO 4
  • "0.4-28” means that the particle size distribution of the negative electrode active material is 0.4 ⁇ m to 28 ⁇ m, and the rest of the examples and comparative examples are understood by analogy.
  • the “negative active material” refers to the prelithiated carbon-doped silicon-oxygen composite material in each example or the negative active material other than graphite in the comparative example. "/" indicates that the corresponding parameter or substance does not exist.
  • Example 1-1 to Example 1-11 and Comparative Example 1 shows that the XRD pattern of the prelithiated carbon-doped silicon-oxygen composite material has the above-mentioned diffraction peak of lithium silicate, as shown in Figure 1 shows that the X-ray diffraction pattern of the prelithiated carbon-doped silicon-oxygen composite material in Example 1-1 includes the diffraction peaks corresponding to Li 2 SiO 3 and Li 4 SiO 4 lithium silicate and silicon, indicating that the use of this The applied prelithiation process generates lithium silicate in advance in the prelithiated carbon-doped silicon-oxygen composite material.
  • the lithium-ion battery obtained in the embodiments of the present application has higher energy density, capacity retention rate, first Coulombic efficiency, and smaller expansion rate, which illustrates that the use of the negative electrode sheet provided by the present application can effectively improve the cycle performance of the lithium-ion battery. and first Coulombic efficiency, and lithium-ion batteries have high energy density.
  • Examples 1-1 to 1-11 contain carbon elements, while Comparative Example 2 does not contain carbon elements.
  • the prelithiated carbon-doped silicon-oxygen composite material contains carbon elements, as shown exemplarily in Figure As shown in 2, (a) is the EDS layered image, (b), (c) and (d) are the distribution images of carbon, silicon and oxygen elements in the pre-lithiated carbon-doped silicon-oxygen composite material.
  • the interior of the prelithiated carbon-doped silicon-oxygen composite material contains silicon, carbon, and oxygen elements, and from Table 1, it can be seen that the interior of the pre-lithiated carbon-doped silicon-oxygen composite material contains lithium element, And in Figure 2, carbon, silicon and oxygen elements are relatively evenly distributed in the pre-lithiated carbon-doped silicon-oxygen composite material. Among them, in Figure 2(b), the pre-lithiated carbon-doped silicon-oxygen composite material has accumulated at the periphery. The carbon element is the carbon element in the conductive adhesive during the test.
  • the lithium-ion battery obtained in the embodiments of the present application has high energy density, high capacity retention rate, first Coulombic efficiency, and small expansion rate, which illustrates that the use of the negative electrode sheet provided by the present application can effectively improve the cycle performance and performance of the lithium-ion battery.
  • Coulombic efficiency for the first time, and lithium-ion batteries have higher energy density.
  • the mass percentage of elements in prelithiated carbon-doped silicon-oxygen composite materials usually affects the cycle performance, energy density and first Coulombic efficiency of lithium-ion batteries. It can be seen from Example 1-1 to Example 1-11, When the mass percentage of lithium element in the prelithiated carbon-doped silicon-oxygen composite material is within the range of the present application, the resulting lithium-ion battery has higher first Coulomb efficiency and energy density, as well as good cycle performance.
  • the particle size distribution range, Dv50 and Dv99 of prelithiated carbon-doped silicon-oxygen composite materials usually also affect the cycle performance and first Coulombic efficiency of lithium-ion batteries.
  • the particle size distribution range, Dv50 and Dv99 of the prelithiated carbon-doped silicon-oxygen composite material are within the range of the present application, the obtained lithium-ion battery has good cycle performance and high first Coulombic efficiency.
  • the powder conductivity of prelithiated carbon-doped silicon-oxygen composite materials usually also affects the cycle performance and first Coulombic efficiency of lithium-ion batteries. It can be seen from Example 1-1 to Example 1-11 that when prelithiated carbon The powder conductivity of the doped silicon-oxygen composite material is within the scope of the present application, and the resulting lithium-ion battery has good cycle performance and high first Coulombic efficiency.
  • the mass ratio of prelithiated carbon-doped silicon-oxygen composites to graphite usually affects the cycle performance, energy density and first Coulombic efficiency of lithium-ion batteries. From Example 1-1, Example 2-1 and Example 2-2 It can be seen that when the mass ratio of the prelithiated carbon-doped silicon-oxygen composite material and graphite is within the range of the present application, the obtained lithium-ion battery has higher energy density, capacity retention rate and first Coulomb efficiency, as well as smaller The expansion rate shows that the lithium-ion battery has good cycle performance, as well as high first Coulomb efficiency and energy density.

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Abstract

一种负极极片、包含该负极极片的电化学装置和电子装置，该负极极片的负极活性材料层中包括预锂化碳掺杂硅氧复合材料和石墨，其中，预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li2SiO3、Li2Si2O5或Li4SiO 中的至少一种所对应的衍射峰。本申请负极极片中的预锂化碳掺杂硅氧复合材料中具有Si-C键，能够抑制硅的歧化，有利于改善电化学装置的循环性能；同时由于预锂化所提前形成的硅酸锂，能够减少对锂离子不可逆的消耗，有利于提升电化学装置的首次库伦效率。

Description

一种负极极片、包含该负极极片的电化学装置及电子装置 技术领域
本申请涉及电化学领域，具体涉及一种负极极片、包含该负极极片的电化学装置及电子装置。
背景技术
锂离子电池具有储能密度大、开路电压高、自放电率低、循环寿命长、安全性好等优点，广泛应用于电能储存、移动电子设备、电动汽车和航天航空设备等各个领域。随着移动电子设备和电动汽车进入高速发展阶段，市场对锂离子电池的能量密度、安全性、循环性能和使用寿命等都提出了越来越高的要求。
由于硅材料的理论克容量高达到4200mAh/g，是目前已知具有最高理论克容量的负极材料。同时硅材料储量丰富，价格低廉，因此，硅材料在锂离子电池中具有广阔的应用前景。但硅材料在脱嵌锂过程中会发生120％至300％的体积膨胀，导致硅材料破裂、粉碎甚至脱离集流体，从而导致负极极片导电性变差，降低锂离子电池的循环性能。同时，硅材料在首次嵌锂过程中会形成固体电解质界面(SEI)膜以及大量不可逆的硅酸盐，消耗了大量来自正极极片和电解液中的锂离子，导致锂离子电池首次库伦效率低。
发明内容
本申请的目的在于提供一种负极极片、包含该负极极片的电化学装置及电子装置，以改善电化学装置的循环性能和首次库伦效率。
需要说明的是，在以下内容中，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。具体技术方案如下：
本申请的第一方面提供了一种负极极片，其包括负极活性材料层，所述负极活性材料层包括负极活性材料，所述负极活性材料包括预锂化碳掺杂硅氧复合材料和石墨；其中，所述预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种所对应的衍射峰。通过调控本申请的负极极片满足上述要求，能够抑制硅的歧化和减少对锂离子不可逆的消耗，有利于改善电化学装置的循环性能和首次库伦效率。
在本申请的一些实施方案中，所述预锂化碳掺杂硅氧复合材料包括碳、硅、氧、锂元素；基于预锂化碳掺杂硅氧复合材料的总质量，所述锂元素的质量百分含量为2.5％至12％，所述硅元素的质量百分含量为45％至65％，所述碳元素的质量百分含量为1％至10％。通 过将各元素的质量百分含量调控在上述范围内，能够使负极活性材料层保持高克容量，同时抑制硅的歧化和减少对锂离子不可逆的消耗，有利于改善电化学装置的循环性能和首次库伦效率。
在本申请的一些实施方案中，所述预锂化碳掺杂硅氧复合材料的粒径分布范围为0.3μm至33μm，Dv50为5.5μm至10μm，Dv99为20μm至31μm。通过将预锂化碳掺杂硅氧复合材料的粒径分布范围、Dv50、Dv99调控在上述范围内，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，所述预锂化碳掺杂硅氧复合材料的粉末电导率为2S/cm至30S/cm。通过将预锂化碳掺杂硅氧复合材料的粉末电导率调控在上述范围内，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，所述石墨包括天然石墨、人造石墨或中间相碳微球等中的至少一种。通过选用上述石墨，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，所述预锂化碳掺杂硅氧复合材料与所述石墨的质量比为(3至7)：(93至97)。通过将预锂化碳掺杂硅氧复合材料的与石墨的质量比调控在上述范围内，有利于改善电化学装置的循环性能。
本申请第二方面提供了一种电化学装置，其包括正极极片、电解液和前述任一实施方案中的负极极片。
在本申请的一些实施方案中，所述电解液包括有机溶剂，所述有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯、碳酸二甲酯、碳酸亚丙酯或丙酸乙酯中的至少一种。通过选用上述有机溶剂，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，所述电解液还包括锂盐，所述锂盐包括六氟磷酸锂、四氟硼酸锂、二氟磷酸锂、双三氟甲烷磺酰亚胺锂、双(氟磺酰)亚胺锂、双草酸硼酸锂或二氟草酸硼酸锂中的至少一种。通过选用上述锂盐，有利于改善电化学装置的循环性能。
本申请第三方面提供了一种子装置，其包括前述任一实施方案中的电化学装置。
本申请提供的一种负极极片、包含该负极极片的电化学装置和电子装置。该负极极片的负极活性材料层中包括预锂化碳掺杂硅氧复合材料和石墨，其中，预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种所对应的衍射峰。本申请负极极片中的预锂化碳掺杂硅氧复合材料中具有Si-C键，能够抑制硅的歧化，有利于改善电化学装置的循环性能；同时由于预锂化所提前形成的硅酸锂，能够减少对锂离子 不可逆的消耗，有利于提升电化学装置的首次库伦效率。
当然，实施本申请的任一产品或方法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发明实施例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发明的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其他的实施例。
图1为实施例1-1中的预锂化碳掺杂硅氧复合材料的X射线衍射(XRD)图谱；
图2为实施例1-1中的预锂化碳掺杂硅氧复合材料的X射线能谱仪(EDS)图谱。
具体实施方式
为使本发明的目的、技术方案、及优点更加清楚明白，以下参照附图并举实施例，对本发明进一步详细说明。显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，在以下内容中，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。具体技术方案如下：
本申请的第一方面提供了一种负极极片，其包括负极活性材料层，负极活性材料层包括负极活性材料，负极活性材料包括预锂化碳掺杂硅氧复合材料和石墨；其中，预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种所对应的衍射峰。
本申请提供的负极极片包括负极活性材料层，负极活性材料层包括预锂化碳掺杂硅氧复合材料和石墨，其中，预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种所对应的衍射峰，能够使负极活性材料层保持高的克容量，预锂化碳掺杂硅氧复合材料中的碳可以改善负极极片的导电性，且碳和硅之间可以形成稳定的Si-C键，有利于抑制硅的歧化以缓解硅的体积膨胀，进而改善电化学装置的循环性能；并且由于预锂化所提前形成的硅酸盐，具体为Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种的硅酸锂，可以有效减少首次放电过程中在负极活性材料表面额外形成的硅酸盐，减少对来自正极极片和电解液中的锂离子不可逆的消耗，从而有利于改善电化学装置的首次库伦效率。整体而言，本申请提供的负极极片具有良好的导电性，将本申请提供的负极极片应用于电化学装置中，有利于改善电化学装置的循环性能和首次库伦效率。
在本申请的一些实施方案中，预锂化碳掺杂硅氧复合材料包括碳、硅、氧、锂元素；基于预锂化碳掺杂硅氧复合材料的总质量，锂元素的质量百分含量为2.5％至12％，硅元素的质量百分含量为45％至65％，碳元素的质量百分含量为1％至10％；优选地，锂元素的质量百分含量为6％至11％，硅元素的质量百分含量为55％至65％，碳元素的质量百分含量为1.5％至5％。例如，锂元素的质量百分含量可以为2.5％、5％、7.5％、10％、12％或上述任意两个数值组成的范围；硅元素的质量百分含量可以为45％、50％、55％、60％、65％或上述任意两个数值组成的范围；碳元素的质量百分含量可以为1％、2％、4％、6％、8％、10％或上述任意两个数值组成的范围。通过将碳、硅、锂元素的质量百分含量控制在上述范围内，能够使负极活性材料层保持高的克容量，预锂化碳掺杂硅氧复合材料中的碳可以改善负极极片的导电性，且碳和硅之间可以形成稳定的Si-C键，有利于抑制硅的歧化以缓解硅的体积膨胀，进而改善电化学装置的循环性能；并且由于预锂化提前形成的上述硅酸锂，可以有效减少首次放电过程中在负极活性材料表面额外形成的硅酸盐，减少对来自正极极片和电解液中的锂离子不可逆的消耗，从而有利于改善电化学装置的首次库伦效率。
需要说明的是，预锂化碳掺杂硅氧复合材料通常会包含一些含量较低(例如质量百分含量小于或等于0.1％)的杂质元素，本申请在计算上述锂元素、硅元素、碳元素的质量百分含量时，“基于预锂化碳掺杂硅氧复合材料的总质量”是指将上述杂质元素排除后得到的总质量，也即是以锂元素、硅元素、碳元素、氧元素的总质量为基准，进而得到锂元素、硅元素、碳元素的质量百分含量，氧元素的质量百分含量则为100％减去锂元素、硅元素和碳元素的质量百分含量之和。
在本申请的一些实施方案中，预锂化碳掺杂硅氧复合材料的粒径分布范围为0.3μm至33μm，Dv50为5.5μm至10μm，Dv99为20μm至31μm。例如，粒径分布范围可以为0.3μm至33μm、0.3μm至30μm、0.4μm至30μm、0.5μm至30μm、0.6μm至30μm中的任一范围；Dv50可以为5.5μm、6μm、6.5μm、7μm、7.5μm、9μm、10μm或上述任意两个数值组成的范围；Dv99可以为20μm、22μm、23μm、24μm、25μm、26μm、27μm、28μm、29μm、30μm、31μm上述任意两个数值组成的范围。通过将预锂化碳掺杂硅氧复合材料的粒径分布范围、Dv50和Dv99调控在上述范围内，能够减少预锂化碳掺杂硅氧复合材料与电解液之间的副反应，以缓解预锂化碳掺杂硅氧复合材料的体积变化，增强预锂化碳掺杂硅氧复合材料的抗压强度，进一步增加负极极片的结构稳定性，从而有利于改善电化学装置的循环性能。
在本申请中，Dv50表示在材料的体积基准的粒度分布中，从小粒径测起，到达体积累积50％的粒径，Dv99表示在材料的体积基准的粒度分布中，从小粒径测起，到达体积累积99％的粒径。
在本申请的一些实施方案中，预锂化碳掺杂硅氧复合材料的粉末电导率为2S/cm至30S/cm。例如，预锂化碳掺杂硅氧复合材料的粉末电导率可以为2S/cm、5S/cm、10S/cm、15S/cm、20S/cm、25S/cm、30S/cm或上述任意两个数值组成的范围。通过将预锂化碳掺杂硅氧复合材料的粉末电导率调控在上述范围内，能够有效控制负极极片与电解液之间界面的电流密度，从而缓解负极极片的析锂现象，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，石墨包括天然石墨、人造石墨或中间相碳微球等中的至少一种。通过选用上述石墨，有利于改善电化学装置的循环性能。
在本申请的一些实施方案中，预锂化碳掺杂硅氧复合材料与石墨的质量比为(3至7)：(93至97)。例如，预锂化碳掺杂硅氧复合材料与所述石墨的质量比可以为7:93、6:94、5:95、4:96、3:97或上述任两个数值范围间的任一比值。通过将预锂化碳掺杂硅氧复合材料的与石墨的质量比调控在上述范围内，能够使负极活性材料层保持高的克容量，同时降低硅与电解液直接接触的概率以减少硅与电解液之间的副反应和SEI膜的形成，缓解硅的体积膨胀，并且石墨可以增加负极极片的导电性，从而有利于协同改善电化学装置的循环性能。
在本申请中，负极活性材料层还可以包括导电剂和粘结剂，本申请对导电剂没有特别限制，只要能够实现本申请目的即可，例如导电剂可以包括导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、鳞片石墨、科琴黑或石墨烯等中的至少一种。本申请对粘结剂没有特别限制，只要能够实现本申请目的即可，例如，粘结剂可以包括聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶(SBR)、海藻酸钠、聚乙烯醇(PVA)、聚四氟乙烯(PTFE)、聚丙烯腈、羟甲基纤维素钠(CMC-Na)或羟甲基纤维素钾(CMC-Ka)中的至少一种。本申请对负极活性材料层中负极活性材料、导电剂、粘结剂的质量比没有特别限制，本领域技术人员可以根据实际需要选择，只要能够实现本申请目的即可。
本申请的负极极片包括负极集流体以及设置于负极集流体至少一个表面上的负极活性材料层。上述“设置于负极集流体至少一个表面上的负极活性材料层”是指，负极活性材料层可以设置于负极集流体沿自身厚度方向上的一个表面上，也可以设置于负极集流体沿自身厚度方向上的两个表面上。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，可以包含铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体(例如碳铜复合集流体、镍铜复合集流体、钛铜复合集流体等)等。本申请对负极集流体和负极活性材料层的厚度没有特别限制，只要能够实现本申请目的即可，例如，负极集流体的厚度为6μm至12μm，负极活性材料层的厚度为30μm至120μm。申请对负极极片的厚度没有特别限制，只要能够实现本申请目的即可，例如，负极极片的厚度为50μm至150μm。
任选地，负极极片还可以包含导电层，导电层位于负极集流体和负极活性材料层之间。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，导电层包括导电剂和粘结剂。本申请对导电层中的导电剂和粘结剂没有特别限制，例如可以是上述导电剂和上述粘结剂中的至少一种。
在本申请的一些实施方案中，预锂化碳掺杂硅氧复合材料是通过将碳掺杂硅氧复合材料预锂化处理得到，预锂化处理是将碳掺杂硅氧复合材料与锂源进行热处理，其中，热处理的温度为400℃至900℃，热处理的升温速率为1℃/min至10℃/min，热处理的保温时间为1h至6h。例如，热处理的温度可以为400℃、500℃、600℃、700℃、800℃、900℃或上述任意两个数值组成的范围；热处理的升温速率可以为1℃/min、2℃/min、4℃/min、6℃/min、8℃/min、10℃/min或上述任意两个数值组成的范围；热处理的保温时间可以为1h、2h、3h、4h、5h、6h或上述任意两个数值组成的范围。通过将热处理温度、热处理升温速率和热处理保温时间调控在上述范围内，可以使预锂化处理更加充分，生成足够含量的硅酸锂，可以有效减少首次放电过程中在负极活性材料表面额外形成的硅酸盐，减少对来自正极极片和电解液中的锂离子不可逆的消耗，有利于改善电化学装置的首次库伦效率。同时将热处理温度、热处理升温速率和热处理保温时间调控在上述范围内，可以有效控制硅的结晶程度，减少硅的膨胀，有利于改善电化学装置的循环性能。
通常情况下，可以改变热处理的温度、升温速率和保温保温时间来调控预锂化碳掺杂硅氧复合材料中锂元素的含量。例如，提高热处理温度，预锂化碳掺杂硅氧复合材料中锂元素含量提升；降低热处理温度，预锂化碳掺杂硅氧复合材料中锂元素含量降低。提高升温速率，预锂化碳掺杂硅氧复合材料中锂元素含量降低；降低升温速率，预锂化碳掺杂硅氧复合材料中锂元素含量提升。延长热处理的保温时间，锂元素含量提升；缩短热处理的保温时间，锂元素含量降低。预锂化碳掺杂硅氧复合材料中硅、碳、氧元素的含量主要取决于碳掺杂硅氧复合材料中的硅、碳、氧元素的含量，热处理条件的变化对其硅、碳、氧 元素的含量变化有一定影响，但影响不大。
改变热处理的温度、升温速率和保温保温时间还可以调控预锂化碳掺杂硅氧复合材料的粒径分布范围、Dv50和Dv99。例如，提高热处理温度，预锂化碳掺杂硅氧复合材料的粒径分布范围变宽，Dv50增大，Dv99增大；降低热处理温度，预锂化碳掺杂硅氧复合材料的粒径分布范围变窄，Dv50减小，Dv99减小。提高升温速率，预锂化碳掺杂硅氧复合材料的粒径分布范围变窄，Dv50减小，Dv99减小；降低升温速率，预锂化碳掺杂硅氧复合材料的粒径分布范围变宽，Dv50增大，Dv99增大。延长热处理的保温时间，预锂化碳掺杂硅氧复合材料的粒径分布范围变宽，Dv50增大，Dv99增大；缩短热处理的保温时间，预锂化碳掺杂硅氧复合材料的粒径分布范围变窄，Dv50减小，Dv99减小。
本申请对碳掺杂硅氧复合材料的制备方法没有特别限制，只要能实现本申请的目的即可，例如，碳掺杂硅氧复合材料的制备方法可以包括但不限于以下步骤：将硅和二氧化硅混合均匀并装入真空沉积炉中，控制温度为1300℃至1350℃且真空度在1Pa至100Pa，通入适量的碳源气体(例如甲烷、乙炔、乙烯等)，得到碳掺杂硅氧复合材料。碳掺杂硅氧复合材料中碳元素、硅元素、氧元素的含量可以通过硅和二氧化硅和混合比例以及通入的碳源气体的含量来调控，例如，硅与二氧化硅的混合比例增大，硅元素的含量增加，氧元素含量降低；硅与二氧化硅的混合比例减小，硅元素的含量降低，氧元素的含量增加；通入的碳源气体增多，碳元素的含量增加；通入的碳源气体的含量减少，碳元素的含量降低。
在本申请中，基于碳掺杂硅氧复合材料的总质量，碳元素的质量百分含量为1％至11.4％，硅元素的质量百分含量为46.2％至73.9％，氧元素的质量百分含量为14.7％至52.8％。需要说明的是，碳掺杂硅氧复合材料通常会包含一些含量较低(例如质量百分含量小于或等于0.1％)的杂质元素，本申请在计算上述碳元素、硅元素、氧元素的质量百分含量时，“基于碳掺杂硅氧复合材料的总质量”是指将上述杂质元素排除后得到的总质量，进而得到碳元素、硅元素、氧元素的质量百分含量。
在本申请中，碳掺杂硅氧复合材料的粒径分布范围为0.2μm至33μm，Dv50为5μm至12μm，Dv99为15μm至31μm。例如，粒径分布范围可以为0.2μm至33μm、0.3μm至33μm、0.3μm至30μm、0.4μm至30μm、0.5μm至30μm、0.6μm至30μm中的任一范围；Dv50可以为5μm、6μm、6.5μm、7μm、7.5μm、9μm、10μm、11μm、12μm或上述任意两个数值组成的范围；Dv99可以为15μm、17μm、20μm、22μm、25μm、26μm、27μm、28μm、29μm、30μm、31μm或上述任意两个数值组成的范围。通过将碳掺杂硅氧复合材料的粒径 分布范围、Dv50和Dv99调控在上述范围内，有利于制备粒径分布范围、Dv50和Dv99符合本申请要求的预锂化碳掺杂硅氧复合材料，进一步获得性能良好的负极极片，从而有利于改善电化学装置的循环性能。
本申请对碳掺杂硅氧复合材料的制备方法没有特别限制，只要能够实现本申请目的即可。
在本申请中，预锂化是通过对负极材料提前进行“补锂”，以抵消形成SEI膜和硅酸盐所造成的不可逆锂损耗，进而提高电池的总容量和首次库伦效率。需要说明的是，本申请对“补锂”所采用的锂源没有特别限定，只要能够实现本申请目的即可，例如，可以包括金属锂、氧化锂、氢化锂、硝酸锂、碳酸锂或硅酸锂中的至少一种。
本申请第二方面提供了一种电化学装置，其包括正极极片、电解液和前述任一实施方案中的负极极片。因此，本申请提供的电化学装置具有良好的循环性能和首次库伦效率。
在本申请的一些实施方案中，电解液包括有机溶剂，有机溶剂包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯或丙酸乙酯中的至少一种。通过选用上述有机溶剂，有利于改善电化学装置的循环性能。基于电解液的质量，有机溶剂的质量百分含量为5％至80％，例如5％、10％、20％、30％、40％、50％、60％、70％、80％或为其间的任意范围。
在本申请中，电解液还可以包括其它有机溶剂，本申请对其它有机剂没有特别限制，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丙酯(DPC)、碳酸甲丙酯(MPC)或碳酸乙丙酯(EPC)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。上述氟代碳酸酯化合物可以包括但不限于碳酸氟代亚乙酯(FEC)、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、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸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乙二醇二甲醚、二乙二醇二甲醚、四乙二醇二甲醚、二丁醚、四氢呋喃、2-甲 基四氢呋喃、1,3-二氧六环、1,4-二氧六环或1,3-二氧五环中的至少一种。上述其它有机溶剂可以包括但不限于乙基乙烯基砜、甲基异丙基砜、异丙基仲丁基砜、环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯或磷酸酯中的至少一种。基于电解液的质量，上述其它有机溶剂的质量百分含量为5％至80％，例如5％、10％、20％、30％、40％、50％、60％、70％、80％或为其间的任意范围。
电解液包括锂盐，锂盐包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂(LiN(CF 3SO 2) 2，LiTFSI)、双(氟磺酰)亚胺锂(Li(N(SO 2F) 2)，LiFSI)、双草酸硼酸锂(LiB(C 2O 4) 2，LiBOB)或二氟草酸硼酸锂(LiBF 2(C 2O 4)，LiDFOB)中的至少一种。基于电解液的质量，锂盐的浓度为0.5mol/L至1.5mol/L。
本申请的正极极片包括正极集流体以及设置于正极集流体至少一个表面上的正极活性材料层。上述“设置于正极集流体至少一个表面上的正极活性材料层”是指，正极活性材料层可以设置于正极集流体沿自身厚度方向上的一个表面上，也可以设置于正极集流体沿自身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。本申请对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，可以包含铝箔、铝合金箔或复合集流体(例如铝碳复合集流体)等。正极活性材料层包括正极活性材料，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，正极活性材料可以包含镍钴锰酸锂(例如常见的NCM811、NCM622、NCM523、NCM111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂(LiCoO 2)、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。正极活性材料层还包括导电剂和粘结剂，本申请对导电剂和粘结剂的种类没有特别限制，只要能够实现本申请目的即可，例如，可以是上述导电剂和上述粘结剂中的至少一种。本申请对正极活性材料层中正极活性材料、导电剂、粘结剂的质量比没有特别限制，本领域技术人员可以根据实际需要选择，只要能够实现本申请目的即可。本申请对正极集流体和正极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，正极集流体的厚度为6μm至12μm，正极材料层的厚度为30μm至120μm。申请对正极极片的厚度没有特别限制，只要能够实现本申请目的即可，例如，正极极片的厚度为50μm至150μm。
任选地，正极极片还可以包含导电层，导电层位于正极集流体和正极材料层之间。导电层的组成没有特别限制，可以是本领域常用的导电层。导电层包括导电剂和粘结剂。本申请对导电层中的导电剂和粘结剂没有特别限制，例如，可以是上述导电剂和上述粘结剂中的至少一种。
在本申请中，电化学装置还包括隔离膜，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。例如，隔离膜的材料可以包括聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类隔离膜、聚酯膜(例如，通过膜种类区分，包括聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)、氨纶或芳纶膜中的至少一种；隔离膜的类型可以包括织造膜、非织造膜(无纺布)、微孔膜、复合膜、碾压膜或纺丝膜中的至少一种。
例如，隔离膜可以包括基材层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层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。
例如，无机物层包括无机颗粒和粘结剂，所述无机颗粒没有特别限制，例如可以包括氧化铝、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。所述粘结剂没有特别限制，例如可以是上述粘结剂中的至少一种。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、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、聚乙烯醚或聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。
本申请的电化学装置还包括包装袋，本申请对包装袋没有特别限制，可以为本领域公知的包装袋，只要能够实现本申请目的即可。
本申请的电化学装置没有特别限定，其可以包括发生电化学反应的任何装置。在一些实施例中，电化学装置可以包括但不限于锂金属二次电池、锂离子二次电池(锂离子电池)、锂聚合物二次电池或锂离子聚合物二次电池等。
本申请的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。
本申请第三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。因此，本申请提供的电子装置具有良好的使用性能。
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：
负极活性材料物相组成的测试：
将各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料的样品粉末放置在XRD测试仪器样品台中，使用2°/min的扫描速率，扫描角度范围10°至80°，得到XRD衍射图。结合分析软件MDI Jade 6.0对各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料的特征峰进行物相分析，看是否存在Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4对应的衍射峰。
负极活性材料中元素的分布和含量的测试：
将样品台上贴好导电胶，取各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料的粉末状样品平铺于导电胶上，用洗耳球吹走未粘上的粉末，喷金，使用PhilipsXL-30型场发射扫描电子显微镜配备的EDS在加速电压为10kV，发射电流为10mA的条件下面扫测试元素的分布和质量百分含量。
粉末电导率的测试：
取5g各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料的粉末样品，用电子压力机恒压至5000kg，维持20s，得到样品片，此时样品片的面积S＝3.14cm 2，测得样品片高度h后的面积S＝3.14cm 2。将样品片置于电阻测试仪(苏州晶格电子ST-2255A)电极间，在样品片两端施加电压U，测得电流I，根据公式R＝U/I，得到样品片电阻R。根据公式δ＝h/(S×R)/1000计算得到粉末电导率，单位为S/cm。
粒径分布、Dv50和Dv99的测试：
在50ml洁净烧杯中加入0.02g各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料的的粉末样品，加入20ml去离子水，再滴加5滴浓度为1％的表面活性剂，使粉末样品完全分散于水中，在120W超声清洗机中超声5分钟，利用激光散射粒度仪MasterSizer 2000测试粒度分布、Dv50和Dv99。
硅晶粒尺寸的测试：
采用透射电子显微镜(TEM)测试各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料中的硅晶粒尺寸。
首次库伦效率的测试：
在测试温度为25℃下，将锂离子电池以0.2C恒流放电到3.0V，静置5min，以0.5C恒流充电到4.45V，以4.45V恒压充电到0.05C后静置5min，测试锂离子电池的首圈充电容量和首圈放电容量，根据以下公式计算首圈库伦效率：
首圈库伦效率＝首圈充电容量/首圈放电容量×100％。
“1C”是在1小时内将各锂离子电池容量完全放完的电流值。
循环容量保持率的测试：
在45℃的环境中，将锂离子电池以0.5C恒流充电至4.45V，再以4.45V恒压充电至0.025C，静置5min，以0.5C恒流放电至3.0V，静置5min，记录首次循环的放电容量。然后以相同的步骤进行500次的充电和放电循环，记录第500次循环锂离子电池的放电容量。
锂离子电池的循环容量保持率(％)＝(第500次循环的放电容量/首次循环的放电容量)×100％。
能量密度的测试：
在25℃的环境中，将锂离子电池按照下述操作流程充电，再进行放电，得出锂离子电池放电容量：锂离子电池以0.5C恒流充电至4.45V，再以4.45V恒压充电至0.025C，静置 5min，以0.5C恒流放电至3.0V，静置5min，得出放电容量C。
上述锂离子电池充电步骤完成后，用激光测厚仪测试锂离子电池的长L、宽W、高H，得到锂离子电池的体积V＝L×W×H。其体积能量密度(ED)可通过如下公式计算得到：ED(Wh/L)＝C/V。
锂离子电池满充膨胀率测试：
在测试温度为45℃下，用螺旋千分尺测试锂离子电池在50％荷电状态(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500圈时，测试锂离子电池在100％SOC下的厚度，记为H1。循环膨胀率＝(H1-H0)/H0×100％。
实施例1-1
<预锂化碳掺杂硅氧复合材料的制备>
将碳掺杂硅氧复合材料和锂源氢化锂按照质量比10:1进行混合，加入去离子水，搅拌均匀，得到复合材料粉末；在氩气氛围下，将复合材料粉末以3℃/min的升温速率升温至700℃保温3h，完成热处理，然后使用去离子水反复清洗三次，干燥，即可得到预锂化碳掺杂硅氧复合材料。其中，碳掺杂硅氧复合材料中碳元素的质量百分含量为1.1％，硅元素的质量百分含量为60.2％，氧元素的质量百分含量为38.7％。
<负极极片的制备>
将预锂化碳掺杂硅氧复合材料、石墨、导电炭黑和丁苯橡胶(SBR)按照质量比5:92:1.8:1.2进行混合，加入去离子水作为溶剂，调配成为固含量为45wt％的浆料，真空搅拌机搅拌均匀后得到负极浆料。将负极浆料均匀涂覆于厚度为10μm的负极集流体铜箔的一个表面上，90℃条件下烘干，得到涂层厚度为100μm的单面涂布负极活性材料层的负极极片。然后在铜箔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层的负极极片。90℃条件下烘干后冷压，再经裁片、焊接极耳，得到规格为78mm×875mm的负极极片待用。
<正极极片的制备>
将正极活性材料钴酸锂(LiCoO 2)、导电炭黑、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(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100μm的单面涂布负极活性材料层的正极极片。然后在 铝箔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。90℃条件下烘干后冷压，再经裁片、焊接极耳，得到规格为74mm×867mm的正极极片待用。
<电解液的制备>
在干燥氩气气氛手套箱中，将有机溶剂碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)和丙酸乙酯(EP)以质量比EC:PC:DEC:EP＝3:1:3:3混合，然后向有机溶剂中加入锂盐六氟磷酸锂(LiPF6)溶解并混合均匀，得到锂盐的浓度为1mol/L的电解液。
<隔离膜的制备>
采用厚度为7μm的多孔聚乙烯薄膜(Celgard公司提供)。
<锂离子电池的制备>
将上述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件装入铝塑膜包装袋中，并在80℃下脱去水分，注入配好的电解液，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1-11
除了按照表1调整相关制备参数以外，其余与实施例1-1相同。
实施例2-1至实施例2-2
除了按照表3调整相关制备参数以外，其余与实施例1-1相同。
对比例1至对比例2
除了按照表1调整相关制备参数以外，其余与实施例1-1相同。
各实施例和对比例的制备参数和性能参数如表1至表3所示。
表1
Figure PCTCN2022118094-appb-000001
Figure PCTCN2022118094-appb-000002
注：表1中的“元素含量”是指对应元素的质量百分含量，“负极活性材料”是指各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料，“/”表示不存在对应的参数或物质。
表2
Figure PCTCN2022118094-appb-000003
Figure PCTCN2022118094-appb-000004
注：表2中的硅酸锂是指Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种，以表2中的实施例1-1为例，“(Li 2SiO 3+Li 4SiO 4)”是指该实施例中负极活性材料的XRD图谱中存在Li 2SiO 3和Li 4SiO 4的衍射峰，“0.4-28”是负极活性材料的粒径分布为0.4μm至28μm，其余实施例和对比例以此类推理解，“负极活性材料”是指各实施例中的预锂化碳掺杂硅氧复合材料或对比例中除石墨以外的负极活性材料，“/”表示不存在对应的参数或物质。
从实施例1-1至实施例1-11和对比例1可以看出，预锂化碳掺杂硅氧复合材料的XRD图谱中存在上述硅酸锂的衍射峰，示例性地如图1所示，实施例1-1中的预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 4SiO 4两种硅酸锂和硅所对应的衍射峰，表明采用本申请的预锂化处理在预锂化预锂化碳掺杂硅氧复合材料中提前生成了硅酸锂。本申请实施例得到的锂离子电池具有更高的能量密度、容量保持率、首次库伦效率，以及较小的膨胀率，从而说明采用本申请提供的负极极片可以有效改善锂离子电池的循环性能和首次库伦效率，而且锂离子电池具有较高的能量密度。
还可以看出，实施例1-1至实施例1-11中包含碳元素，而对比例2中不包含碳元素，预锂化碳掺杂硅氧复合材料包含碳元素，示例性地如图2所示，(a)为EDS分层图像，(b)、(c)和(d)分别为碳、硅和氧元素在预锂化碳掺杂硅氧复合材料中的分布图像。从图中可以看出预锂化碳掺杂硅氧复合材料的内部含有硅、碳、氧元素，以及从表1中可以看出预锂化碳掺杂硅氧复合材料的内部含有锂元素，并且图2中碳、硅和氧元素在预锂化碳掺 杂硅氧复合材料中分布较为均匀，其中，在图2的(b)中，预锂化碳掺杂硅氧复合材料外围聚集的碳元素为测试时导电胶中的碳元素。本申请实施例得到的锂离子电池具有高能量密度、高容量保持率、首次库伦效率，以及较小的膨胀率，从而说明采用本申请提供的负极极片可以有效改善锂离子电池的循环性能和首次库伦效率，而且锂离子电池具有较高的能量密度。
预锂化碳掺杂硅氧复合材料中元素的质量百分含量通常会影响锂离子电池的循环性能、能量密度和首次库伦效率，从实施例1-1至实施例1-11可以看出，当预锂化碳掺杂硅氧复合材料中锂元素的质量百分含量在本申请的范围内，得到的锂离子电池具有更高的首次库伦效率和能量密度，以及良好的循环性能。
预锂化碳掺杂硅氧复合材料的粒径分布范围、Dv50和Dv99通常也会影响锂离子电池的循环性能和首次库伦效率，从实施例1-1至实施例1-11可以看出，当预锂化碳掺杂硅氧复合材料的粒径分布范围、Dv50和Dv99在本申请的范围内，得到的锂离子电池具有良好的循环性能和较高的首次库伦效率。
预锂化碳掺杂硅氧复合材料的粉末电导率通常也会影响锂离子电池的循环性能和首次库伦效率，从实施例1-1至实施例1-11可以看出，当预锂化碳掺杂硅氧复合材料的粉末电导率在本申请的范围内，得到的锂离子电池具有良好的循环性能和较高的首次库伦效率。
表3
Figure PCTCN2022118094-appb-000005
预锂化碳掺杂硅氧复合材料与石墨的质量比通常会影响锂离子电池的循环性能、能量密度和首次库伦效率，从实施例1-1、实施例2-1和实施例2-2可以看出，当预锂化碳掺杂硅氧复合材料与石墨的质量比在本申请的范围内，得到的锂离子电池具有较高的能量密度、容量保持率和首次库伦效率，以及较小的膨胀率，从而说明锂离子电池具有良好的循环性能，以及较高的首次库伦效率和能量密度。
以上所述仅为本发明的较佳实施例，并不用以限制本发明，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明保护的范围之内。

Claims (11)

  1. 一种负极极片，其包括负极活性材料层，所述负极活性材料层包括负极活性材料，所述负极活性材料包括预锂化碳掺杂硅氧复合材料和石墨；
    其中，所述预锂化碳掺杂硅氧复合材料的X射线衍射图谱包括Li 2SiO 3、Li 2Si 2O 5或Li 4SiO 4中的至少一种所对应的衍射峰。
  2. 根据权利要求1所述的负极极片，其中，所述预锂化碳掺杂硅氧复合材料包括碳、硅、氧、锂元素；
    基于所述预锂化碳掺杂硅氧复合材料的总质量，所述锂元素的质量百分含量为2.5％至12％，所述硅元素的质量百分含量为45％至65％，所述碳元素的质量百分含量为1％至10％。
  3. 根据权利要求1所述的负极极片，其符合如下特征中的至少一者：
    a).所述锂元素的质量百分含量为6％至11％；
    b).所述硅元素的质量百分含量为55％至65％；
    c).所述碳元素的质量百分含量为1％至5％。
  4. 根据权利要求1所述的负极极片，其中，所述预锂化碳掺杂硅氧复合材料的粒径分布范围为0.3μm至33μm，Dv50为5.5μm至10μm，Dv99为20μm至31μm。
  5. 根据权利要求1所述的负极极片，其中，所述预锂化碳掺杂硅氧复合材料的粉末电导率为2S/cm至30S/cm。
  6. 根据权利要求1所述的负极极片，其中，所述石墨包括天然石墨、人造石墨或中间相碳微球等中的至少一种。
  7. 根据权利要求1所述的负极极片，其中，所述预锂化碳掺杂硅氧复合材料与所述石墨的质量比为(3至7):(93至97)。
  8. 一种电化学装置，其包括正极极片、电解液和权利要求1至7中任一项所述的负极极片。
  9. 根据权利要求8所述的电化学装置，其中，所述电解液包括有机溶剂，所述有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯、碳酸二甲酯、碳酸亚丙酯或丙酸乙酯中的至少一种。
  10. 根据权利要求8所述的电化学装置，其中，所述电解液还包括锂盐，所述锂盐包括六氟磷酸锂、四氟硼酸锂、二氟磷酸锂、双三氟甲烷磺酰亚胺锂、双(氟磺酰)亚胺锂、双草酸硼酸锂或二氟草酸硼酸锂中的至少一种。
  11. 一种电子装置，其包括权利要求8至10中任一项所述的电化学装置。
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