WO2025199684A1 - 一种二次电池及其制备方法、电子装置 - Google Patents

一种二次电池及其制备方法、电子装置

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Publication number
WO2025199684A1
WO2025199684A1 PCT/CN2024/083580 CN2024083580W WO2025199684A1 WO 2025199684 A1 WO2025199684 A1 WO 2025199684A1 CN 2024083580 W CN2024083580 W CN 2024083580W WO 2025199684 A1 WO2025199684 A1 WO 2025199684A1
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WIPO (PCT)
Prior art keywords
silicon
compound
carbon
secondary battery
negative electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/CN2024/083580
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English (en)
French (fr)
Inventor
任文臣
张丽娟
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Filing date
Publication date
Application filed by Ningde Amperex Technology Ltd filed Critical Ningde Amperex Technology Ltd
Priority to PCT/CN2024/083580 priority Critical patent/WO2025199684A1/zh
Publication of WO2025199684A1 publication Critical patent/WO2025199684A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • 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, and in particular to a secondary battery and a preparation method thereof, and an electronic device.
  • silicon-containing negative electrodes Compared with traditional graphite-containing negative electrodes, silicon-containing negative electrodes have higher theoretical specific capacity and energy density. The use of silicon-containing negative electrodes can produce higher-capacity secondary batteries, thereby providing longer service time and higher endurance.
  • silicon-containing negative electrodes one of the important problems being the fragility of silicon particles. Silicon has a large volume expansion rate and contraction rate, and is prone to volume expansion and contraction during the charge and discharge process, resulting in stress concentration of silicon particles and rupture of nanoparticles. This will lead to capacity decay, coulombic efficiency and poor high-temperature storage performance of secondary batteries.
  • lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries.
  • the specific technical solutions are as follows:
  • the mass percentage x1 of the oxygen element in the silicon-carbon compound is within the above range, the resulting silicon-carbon compound has good compressive strength, a small rate of change in oxygen content after compression, and good oxidation resistance, thereby facilitating improved initial discharge capacity, initial coulombic efficiency, and high-temperature storage performance of the secondary battery.
  • the molar ratio of the phenolic compound, the formaldehyde, and the ammonia is 1:(1.0 to 2.0):(0.006 to 0.013)
  • the phenolic compound includes at least one of resorcinol, cresol, nonylphenol, aralkylphenol, cardanol, octylphenol, bisphenol A or xylenol
  • the temperature T1 of the insulation reaction is 55°C to 90°C, and the time t1 is 0.5h to 3h
  • the mass ratio of the emulsifier to the phenolic compound is (0.065 to 0.11):1
  • the temperature T2 of the temperature increase reaction is 100°C to 150°C
  • the time t2 is 0.5h to 5h
  • the carbonization treatment temperature T3 is 450°C to 700°C, and the time t3 is 1h to 3h;
  • the flow rate V1 of the first compound gas in the atmosphere containing the first compound is 1L/min to 3L/min, and the activation treatment temperature T4 is 750°C to 1100°C, and the time t4 is 6h to 14h;
  • the pretreatment temperature T5 is 400°C to 550°C, and the time t5 is 1h to 3h;
  • the silane-containing atmosphere includes at least one of monosilane, disilane, trisilane, phenylsilane or tolylsilane, and the flow rate V2 of the silane gas in the silane-containing atmosphere is 1.5L/min to 3L/min, and the ventilation time t6 is 220min to 420min;
  • the insulation treatment temperature T7 is 450°C to 600°C, and the time t7 is 0.5h to 2h;
  • the flow rate V3 of the second compound gas in the atmosphere containing the second compound is 2L/min to 7L/min, and the ventilation time t8 is 180min to 400min.
  • a third aspect of the present application provides an electronic device, which includes the secondary battery in any of the aforementioned embodiments or the secondary battery manufactured by the manufacturing method in any of the aforementioned embodiments.
  • the present application provides a secondary battery and a preparation method thereof, and an electronic device.
  • the secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator; the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, the negative electrode material layer includes a silicon-carbon compound; the sphericity of the silicon-carbon compound is 0.71. 1, the silicon-carbon compound includes silicon, carbon, and oxygen, the mass percentage of oxygen in the silicon-carbon compound is x1, and after being compressed at 200 MPa, the mass percentage of oxygen in the silicon-carbon compound is x2, and (x2-x1)/x1 ⁇ 100% ⁇ 300%.
  • the secondary battery provided by this application has a high initial discharge capacity, a high initial coulombic efficiency, and a low thickness expansion rate.
  • FIG1 is an electron microscope photograph of the silicon-carbon compound in Example 4.
  • FIG2 is an electron microscope photograph of the silicon-carbon compound in Comparative Example 1.
  • the first aspect of the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator; the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer comprising a silicon-carbon compound.
  • the silicon-carbon compound has a degree of sphericity of 0.71 to 1. In some embodiments of the present application, the degree of sphericity of the silicon-carbon compound is 0.75 to 1. For example, the degree of sphericity of the silicon-carbon compound may be 0.71, 0.73, 0.78, 0.8, 0.85, 0.9, 0.95, 1, or a range consisting of any two values therebetween.
  • the silicon-carbon compound comprises silicon, carbon, and oxygen, the mass percentage of oxygen in the silicon-carbon compound being x1, and after being compressed at 200 MPa, the mass percentage of oxygen in the silicon-carbon compound being x2, and (x2-x1)/x1 ⁇ 100% ⁇ 300%.
  • the value of (x2-x1)/x1 ⁇ 100% can be 1%, 3%, 5%, 7%, 10%, 20%, 30%, 50%, 75%, 100%, 125%, 150%, 175%, 200%, 225%, 250%, 275%, 300%, or a range consisting of any two values therebetween.
  • the mass percentage of oxygen element x1 in the silicon-carbon compound refers to the mass percentage of oxygen element in the silicon-carbon compound before the silicon-carbon compound is subjected to pressure treatment.
  • the sphericity of silicon carbon compounds can characterize the shape of silicon carbon compound particles.
  • the silicon-carbon compound particles When the sphericity is small, for example, When the ratio is greater than 0.71, the silicon-carbon compound particles have many sharp corners. After being subjected to force, the sharp corners are prone to stress concentration, which leads to particle breakage.
  • the broken cross-section of the particles will quickly react with the air or electrolyte to lose activity, thereby affecting the first discharge capacity and the first coulomb efficiency of the secondary battery.
  • the broken cross-section of the particles is very likely to react with the electrolyte at high temperatures to produce gas, thereby affecting the high-temperature storage performance of the secondary battery.
  • (x2-x1)/x1 ⁇ 100% can be understood as the rate of change of the oxygen content in the silicon-carbon compound before and after being subjected to a pressure of 200Mpa.
  • the value of (x2-x1)/x1 ⁇ 100% is too large, for example, greater than 300%, it means that the silicon-carbon compound particles are severely broken and the structural integrity is poor after being subjected to force.
  • it is easy to have the problem of oxidation side reactions caused by particle damage, thereby affecting the first discharge capacity, first coulomb efficiency and high-temperature storage performance of the secondary battery.
  • the sphericity of the silicon-carbon compound in the secondary battery of the present application and the value of (x2-x1)/x1 ⁇ 100% are within the above ranges, the silicon-carbon compound particles have fewer sharp corners and good structural integrity after being subjected to force, and are therefore less likely to undergo side reactions with the electrolyte, thereby improving the initial discharge capacity, initial coulombic efficiency and high-temperature storage performance of the secondary battery.
  • x1 can be 0.12%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.1%, 2.2%, 2.3%, or a range consisting of any two values therebetween.
  • the mass percentage x1 of the oxygen element in the silicon-carbon compound is within the above range, the resulting silicon-carbon compound has good compressive strength, and the rate of change of its oxygen content after being compressed is small, and has good oxidation resistance, which is beneficial to improving the initial discharge capacity, initial coulombic efficiency, and high-temperature storage performance of the secondary battery.
  • the 10% strain compressive strength F of the silicon-carbon compound is greater than or equal to 152.2 MPa. In some embodiments of the present application, the 10% strain compressive strength F is greater than or equal to 152.2 MPa and less than or equal to 300 MPa. For example, it can be 152.2 MPa, 155 MPa, 160 MPa, 180 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa or a range consisting of any two values therebetween.
  • the 10% strain compressive strength F of the silicon-carbon compound is within the above range, indicating that the particles of the silicon-carbon compound have high compressive strength and are not easily broken after being subjected to force, which is beneficial to improving the first discharge capacity, first coulomb efficiency and high temperature storage performance of the secondary battery.
  • the mass percentage content W1 of silicon in particles with a particle diameter greater than or equal to 10 ⁇ m in the silicon-carbon compound is 40.3% to 55.7%.
  • the mass percentage content W1 of silicon can be 40.3%, 40.5%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 55.7%, or a range consisting of any two values therebetween.
  • the element content in particles with a diameter greater than or equal to 10 ⁇ m is more representative.
  • the silicon-carbon compound obtained has suitable compressive strength and specific capacity, thereby improving the first discharge capacity, first coulombic efficiency and high-temperature storage performance of the secondary battery, while the secondary battery also has a higher energy density.
  • the mass percentage content W2 of the oxygen element in the particles with a particle diameter greater than or equal to 10 ⁇ m in the silicon-carbon compound is 0.1% to 1.12%, further ensuring that the silicon-carbon compound has good oxidation resistance and improving the first discharge capacity, first coulomb efficiency and high-temperature storage performance of the secondary battery.
  • the mass percentage content W2 of the oxygen element can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.12% or a range consisting of any two values therebetween.
  • the element content in particles with a diameter greater than or equal to 10 ⁇ m is more representative.
  • the mass percentage content W3 of carbon element in particles with a particle diameter greater than or equal to 10 ⁇ m in the silicon-carbon compound is 43.2% to 59.2%, and W1+W3 ⁇ 99%. This can improve the initial discharge capacity, initial coulombic efficiency and high-temperature storage performance of the secondary battery while making the secondary battery have a higher energy density.
  • the mass percentage content W3 of carbon element can be 43.2%, 43.5%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 59.2% or a range consisting of any two values therebetween.
  • the Dv50 of the silicon-carbon compound is 5.4 ⁇ m to 8.9 ⁇ m.
  • the Dv50 of the silicon-carbon compound can be 5.4 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, 8.9 ⁇ m, or a range consisting of any two values therebetween.
  • the obtained silicon-carbon compound particles have fewer surface defects, are less likely to crack after being subjected to force, and have good compressive resistance, which is beneficial to improving the initial discharge capacity, initial coulombic efficiency, and high-temperature storage performance of the secondary battery.
  • the tap density TD of the silicon carbon compound is 0.7 g/cc to 1.2 g/cc.
  • the tap density TD can be 0.7 g/cc, 0.72 g/cc, 0.74 g/cc, 0.85 g/cc, 0.87 g/cc, 0.90 g/cc, 0.92 g/cc, 0.97 g/cc, 1.01 g/cc, 1.05 g/cc, 1.17 g/cc, 1.19 g/cc, 1.2 g/cc, or any two values therebetween.
  • the obtained silicon-carbon compound has a high tap density, which is beneficial for reducing the thickness of the negative electrode sheet, and thus the obtained secondary battery has a high energy density.
  • the compacted density PD of the silicon-carbon compound is 1.22 g/cc at 0.83 g/cc.
  • the compacted density PD can be 0.83 g/cc, 0.85 g/cc, 0.90 g/cc, 0.93 g/cc, 0.95 g/cc, 0.98 g/cc, 1.00 g/cc, 1.03 g/cc, 1.05 g/cc, 1.08 g/cc, 1.1 g/cc, 1.13 g/cc, 1.15 g/cc, 1.18 g/cc, 1.20 g/cc, 1.22 g/cc, or a range consisting of any two values therebetween.
  • a second aspect of the present application provides a method for preparing a secondary battery according to any of the aforementioned embodiments, comprising the following steps: preparing a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, and assembling them to obtain a secondary battery;
  • the method for preparing the silicon-carbon compound in the negative electrode plate comprises the following steps:
  • a phenolic compound, formaldehyde, ammonia and water are mixed, mixed evenly and then subjected to heat preservation reaction, and then an emulsifier is added, mixed evenly and then subjected to temperature reaction to obtain a porous carbon precursor.
  • the molar ratio A of the phenolic compound, formaldehyde and ammonia is 1: (1.0 to 2.0): (0.006 to 0.013)
  • the phenolic compound includes at least one of resorcinol, cresol, nonylphenol, arylalkylphenol, cardanol, octylphenol, bisphenol A or xylenol
  • the temperature T1 of the heat preservation reaction is 55°C to 90°C, and the time t1 is 0.5h to 3h
  • the mass ratio B of the emulsifier to the phenolic compound is (0.065 to 0.11): 1
  • the temperature T2 of the temperature rise reaction is 100°C to 150°C
  • the time t2 is 0.5h
  • the molar ratio A can be 1:1:0.006, 1:1.5:0.006, 1:2:0.006, 1:1:0.010, 1:1.5:0.010, 1:2:0.010, 1:1:0.013, 1:1.5:0.013, 1:2:0.013, or a range consisting of any two ratios therebetween.
  • the temperature T1 can be 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or a range consisting of any two values therebetween.
  • the time t1 can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or a range consisting of any two values therebetween.
  • the mass ratio B can be 0.065:1, 0.070:1, 0.075:1, 0.080:1, 0.085:1, 0.090:1, 0.095:1, 0.100:1, 0.105:1, 0.110:1, or a range consisting of any two ratios therebetween.
  • the temperature T2 can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, or a range consisting of any two values therebetween.
  • the time t2 can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or a range consisting of any two values therebetween.
  • the porous carbon precursor is carbonized in an inert atmosphere, and then activated in an atmosphere containing a first compound to obtain a porous carbon matrix, wherein the first compound includes carbon dioxide or water vapor.
  • the carbonization temperature T3 is 450°C to 700°C
  • the time t3 is 1h to 3h
  • the flow rate V1 of the first compound gas in the atmosphere containing the first compound is 1L/min to 3L/min
  • the activation treatment temperature T4 is 750°C to 1100°C
  • the time t4 is 6h to 14h.
  • the temperature T4 may be 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, or a range consisting of any two values therebetween.
  • the time t4 may be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or a range consisting of any two values therebetween.
  • the pretreatment temperature T5 is 400°C to 550°C, and the time t5 is 1h to 3h;
  • the silane-containing atmosphere includes at least one of monosilane, disilane, trisilane, phenylsilane or tolylsilane, the flow rate V2 of the silane gas in the silane-containing atmosphere is 1.5L/min to 3L/min, and the ventilation time t6 is 220min to 420min;
  • the heat preservation temperature T7 is 450°C to 600°C, and the time t7 is 0.5h to 2h;
  • the flow rate V3 of the second compound gas in the second compound-containing atmosphere is 2L/min to 7L/min, and the ventilation time t8 is 180min to 400min.
  • the temperature T5 can be 400°C, 425°C, 450°C, 475°C, 500°C, 525°C, 550°C, or a range consisting of any two values therebetween.
  • the time t5 can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or a range consisting of any two values therebetween.
  • the flow rate V2 can be 1.5 L/min, 1.8 L/min, 2 L/min, 2.2 L/min, 2.5 L/min, 2.8 L/min, 3 L/min, or a range consisting of any two values therebetween.
  • the flow rate V3 can be 2L/min, 3L/min, 4L/min, 5L/min, 6L/min, 7L/min, or a range consisting of any two values therebetween.
  • the ventilation duration t8 can be 180min, 200min, 225min, 250min, 275min, 300min, 325min, 350min, 375min, 400min, or a range consisting of any two values therebetween.
  • the porous carbon precursor obtained by the above step (1) has fewer sharp corners, which is conducive to obtaining silicon-carbon compounds with high sphericity in the subsequent process.
  • the activation treatment in step (2) makes the pores inside the porous carbon precursor more abundant, and the obtained porous carbon matrix is conducive to the subsequent deposition of silicon materials.
  • the porous carbon precursor can be heated to the silane decomposition temperature through pretreatment , and then silane gas is introduced to deposit silicon materials in the pores of the porous carbon matrix; after heating, The heat preservation treatment heats the porous carbon precursor of the deposited silicon to the decomposition temperature of the second compound, and finally introduces a gas containing the second compound to coat the exposed surface of the deposited silicon with the carbon material.
  • the resulting silicon-carbon compound has a sphericity of 0.71 to 1 and a (x2-x1)/x1 ⁇ 100% ⁇ 300%. This means that the silicon-carbon compound has a high sphericity, a small change in oxygen content before and after compression, good structural integrity after stress, and is less likely to react with the electrolyte. This can improve the initial discharge capacity, initial coulombic efficiency, and high-temperature storage performance of the secondary battery.
  • the present application does not limit the gas composition and flow rate in the inert atmosphere in steps (2) and (3).
  • the gas in the inert atmosphere may include but is not limited to nitrogen, argon, helium, etc., and the flow rate may be 1 L/min to 10 L/min.
  • the silicon-carbon compound can be further treated as follows: the reaction product is heat-treated in a blast oven, with the heat treatment temperature T9 being 120° C. to 160° C. and the heat treatment time t9 being 6 h to 10 h.
  • the term "negative electrode material layer disposed on at least one surface of the negative electrode current collector” means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on both surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface” here can refer to the entire surface of the negative electrode current collector or a portion of the surface of the negative electrode current collector. This is not particularly limited in this application, as long as the purpose of this application can be achieved.
  • the present application has no particular restrictions on the negative electrode current collector, as long as the purpose of the present application can be achieved.
  • it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector.
  • the composite current collector can be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.
  • the above-mentioned silicon-carbon compound can be used as the negative electrode active material in the negative electrode material layer.
  • the negative electrode material layer may also include other negative electrode active materials.
  • the present application has no particular limitation on other negative electrode active materials as long as the purpose of the present application can be achieved.
  • other negative electrode active materials may include but are not limited to natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, Li-Sn alloy, Li-Sn-O alloy, Sn , SnO, SnO2 , spinel structured lithiated TiO2 - Li4Ti5O12 or at least one of Li-Al alloy.
  • the negative electrode material layer may further include a conductive agent and a binder.
  • the present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved.
  • the conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black.
  • the above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and/or nano-carbon fibers.
  • the above-mentioned metal materials may include but are not limited to metal powder and/or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver.
  • the above-mentioned conductive polymer may include but is not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.
  • the binder may include but is not limited to polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polyethylene, polypropylene, acrylic acid (ester) styrene-butadiene rubber, epoxy resin or nylon or polyvinylidene fluoride.
  • the present application does not particularly limit the mass ratio of the negative electrode active material, conductive agent and binder in the negative electrode material layer, and those skilled in the art can select according to actual needs, as long as the purpose of the application can be achieved.
  • the present application does not particularly limit the thickness of the negative electrode material layer, as long as it can achieve the purpose of the present application.
  • the thickness of the negative electrode material layer is 30 ⁇ m to 120 ⁇ m.
  • the present application does not particularly limit the thickness of the negative electrode current collector, as long as it can achieve the purpose of the present application.
  • the thickness of the negative electrode current collector is 4 ⁇ m to 15 ⁇ m.
  • the negative electrode sheet may further include a conductive layer positioned between the negative electrode current collector and the negative electrode material layer.
  • a conductive layer positioned between the negative electrode current collector and the negative electrode material layer.
  • the present application does not particularly limit the composition of the conductive layer, and it may be any conductive layer commonly used in the art.
  • the conductive layer may include a conductive agent and a binder.
  • the present application does not particularly limit the conductive agent and binder in the conductive layer, and for example, it may be at least one of the above-mentioned conductive agents and binders.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector.
  • the phrase "positive electrode material layer disposed on at least one surface of the positive electrode current collector” means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its thickness direction, or on both surfaces of the positive electrode current collector along its thickness direction.
  • the "surface” here can refer to the entire surface of the positive electrode current collector or a portion of the surface of the positive electrode current collector. This is not particularly limited in the present application, as long as the purpose of this application can be achieved.
  • the positive electrode material layer includes a positive electrode active material.
  • the present application has no particular limitation on the positive electrode active material as long as the purpose of the present application can be achieved.
  • the positive electrode active material may include but is not limited to at least one of lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide ( LiCoO2 ), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate.
  • the positive electrode material layer may also include a conductive agent and a binder.
  • the present application has no particular restrictions on the types of the conductive agent and the binder, as long as they can achieve the purpose of the present application. For example, it can be at least one of the above conductive agents and the above binder.
  • the present application has no particular restrictions on the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer. Technical personnel can choose according to actual needs, as long as the purpose of this application can be achieved.
  • the thickness of the positive electrode current collector and the positive electrode material layer is not particularly limited in this application, as long as the purpose of this application can be achieved.
  • the thickness of the positive electrode current collector is 5 ⁇ m to 20 ⁇ m
  • the thickness of the positive electrode material layer is 30 ⁇ m to 120 ⁇ m.
  • the positive electrode sheet may further include a conductive layer positioned 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 any commonly used conductive layer in the art.
  • the conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and binder in the conductive layer; for example, the conductive layer may be at least one of the aforementioned conductive agents and binders.
  • the separator may include a substrate layer and a surface treatment layer.
  • the substrate layer may be a non-woven fabric, a film, or a composite film having a porous structure
  • the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.
  • a binder may include but is not limited to at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • Above-mentioned carbonate compound can include but not limited to at least one in linear carbonate compound, cyclic carbonate compound or fluorinated carbonate compound.
  • Above-mentioned linear carbonate compound can include but not limited to at least one in dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or ethyl methyl carbonate (EMC).
  • Absove-mentioned cyclic carbonate can include but not limited to at least one in ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC).
  • the fluorinated carbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 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, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.
  • FEC fluoroethylene carbonate
  • the above-mentioned carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decanoic acid lactone, valerolactone, or caprolactone.
  • the above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran.
  • the above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.
  • the present application does not particularly limit the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved.
  • the secondary battery also includes a shell for accommodating a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, as well as other components known in the field of secondary batteries.
  • a shell for accommodating a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, as well as other components known in the field of secondary batteries.
  • This application does not limit the above-mentioned other components.
  • This application has no special restrictions on the shell, and it can be a shell known in the art, as long as it can achieve the purpose of this application.
  • the shell can be a hard shell or a flexible shell.
  • the material of the hard shell can be metal.
  • the flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.
  • the preparation process of the secondary battery of the present application is well known to those skilled in the art and is not particularly limited in the present application.
  • the preparation process of the secondary battery may include but is not limited to the following steps: stacking the positive electrode sheets, the separator and the negative electrode sheets in order, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery.
  • the secondary battery of the present application includes, but is not limited to: a lithium ion battery or a sodium ion battery. In some embodiments of the present application, the secondary battery includes a lithium ion battery.
  • a third aspect of the present application provides an electronic device, which includes the secondary battery in any of the aforementioned embodiments or the secondary battery manufactured by the manufacturing method in any of the aforementioned embodiments.
  • the present application does not particularly limit the type of electronic device, and it can be any electronic device known in the prior art.
  • the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.
  • the sphericity of silicon-carbon compounds was tested using the equivalent diameter method.
  • the test method was to use a ZEISS-SEM (sigma-02-33) scanning electron microscope to observe the silicon-carbon compound particles in the cross section of the negative electrode material layer along the thickness direction.
  • the test field size was 50 ⁇ m ⁇ 50 ⁇ m.
  • the silicon-carbon compound particles whose cross sections all fell within the test field were tested and calculated, and the equivalent diameter of the circumference and the equivalent diameter of the particle area of the above silicon-carbon compound particles were tested.
  • Image analysis was used to test the silicon-carbon compound particles in a cross-section of the negative electrode material layer along the thickness direction using a ZEISS-SEM (Sigma-02-33) in backscattered mode. The silicon-carbon compound particles whose cross-sections fell within the microscopic image were tested and calculated. ImageJ software was used to identify the edges of the silicon-carbon compound particles in the image, and then the projected area of each particle was calculated. The area equivalent diameter of each particle was calculated based on the equivalent projected area. The calculated area equivalent diameters were then statistically analyzed to obtain the Dv50 of the silicon-carbon compound.
  • the silicon-carbon compound particles in the cross-section of the negative electrode material layer along the thickness direction were observed using a ZEISS-SEM (sigma-02-33).
  • the silicon content of the silicon-carbon compound particles was measured using an energy dispersive spectrometer (EDS).
  • EDS energy dispersive spectrometer
  • the silicon content and oxygen content of 50 particles with an equivalent diameter greater than or equal to 10 ⁇ m were counted and averaged. These values are recorded as the mass percentage of silicon in the silicon-carbon compound particles with a diameter greater than or equal to 10 ⁇ m (W1) and the mass percentage of oxygen in the silicon-carbon compound particles with a diameter greater than or equal to 10 ⁇ m (W2).
  • a 3.0g sample of silicon-carbon compound powder was placed in an extrusion die with a diameter of 25mm.
  • the sample was then pressurized using an electronic pressure testing machine at a controlled pressure of 200MPa, a displacement rate of 10mm/min, and a holding time of 30s. After the holding period, the pressure was released.
  • the silicon-carbon compound was removed from the die and exposed to air at room temperature for 5 hours. The oxygen content by mass in the silicon-carbon compound was then measured using EDS, recorded as x2.
  • Silicon-carbon compound powder, conductive agent (SP), binder (PAA-Li), carbon nanotubes (CNTs), and dispersant (CMC) were mixed in a mass ratio of 84:10:5:0.4:0.6, and deionized water was added to produce a negative electrode slurry with a solid content of 48 wt%.
  • the slurry was mixed evenly and applied to 6 ⁇ m thick copper foil. Drying was performed at 120°C, resulting in a coating weight of 100.1 mg/1540 mm2 of negative electrode material. After cold pressing and punching, the negative electrode sheet was obtained.
  • the thickness of the negative electrode material layer on a single side was 54.5 ⁇ m.
  • EMC ethyl methyl carbonate
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • FEC Fluoroethylene carbonate
  • LiPF6 lithium salt LiPF6 was added to create an electrolyte solution. The concentration of the lithium salt LiPF6 was 1 mol/L.
  • the above-mentioned negative electrode plate, the counter electrode metal lithium plate, the polypropylene (PP) separator and the above-mentioned electrolyte were assembled into a button battery.
  • the initial coulombic efficiency of a lithium-ion battery C2/C1 ⁇ 100%.
  • the newly prepared lithium-ion battery was charged to 4.5V at a constant current rate of 0.5C, and charged to 0.05C at a constant voltage of 4.5V, and allowed to stand for 5 minutes.
  • the thickness of the lithium-ion battery at this step was measured and recorded as H1; the lithium-ion battery was placed in an 85°C forced air oven for 24 hours, then the lithium-ion battery was taken out and cooled to 25°C, and the thickness of the lithium-ion battery at this step was measured and recorded as H2.
  • the high-temperature storage thickness expansion rate of a lithium-ion battery (H2 - H1) / H1 ⁇ 100%.
  • the high-temperature storage thickness expansion rate is used to characterize the high-temperature storage performance of a lithium-ion battery. The smaller the high-temperature storage thickness expansion rate, the better the high-temperature storage performance, while the larger the high-temperature storage thickness expansion rate, the worse the high-temperature storage performance.
  • Phenolic compounds resorcinol, formaldehyde, and ammonia are mixed in a molar ratio A of 1:1.5:0.010, and after mixing evenly, the mixture is heated to a temperature of 80°C and a time of 2h.
  • the mass of water added is 10 times the mass of the phenolic compound.
  • the temperature T1 of the heating reaction is 80°C and the time t1 is 2h.
  • an emulsifier F127 is added, and the mass ratio B of the emulsifier to the phenolic compound is 0.065:1.
  • the mixture is stirred for 0.5h, and after mixing evenly, the mixture is heated to a temperature of 100°C and a time t2 is 4h.
  • the reaction solution is filtered and washed to obtain a porous carbon precursor.
  • porous carbon precursor 1000 g was carbonized in a nitrogen atmosphere with a nitrogen flow rate of 2.5 L/min, a carbonization temperature T3 of 600°C, and a time t3 of 2 h; then, an activation treatment was performed in an atmosphere containing a first compound to obtain a porous carbon matrix, the first compound was carbon dioxide, the flow rate V1 of the first compound gas was 2.5 L/min, the activation temperature T4 was 900°C, and the time t4 was 12 h.
  • the silicon-carbon compound and artificial graphite prepared above were mixed in a mass ratio of 1:9 as the negative electrode active material.
  • the negative electrode active material, carbon nanotubes, lithium carboxymethyl cellulose, and lithium polyacrylate were mixed in a mass ratio of 97.4:0.2:0.4:2, and deionized water was added as a solvent to prepare a slurry with a solid content of 45wt%.
  • a negative electrode slurry with a viscosity of 6000mPa.s was obtained.
  • the negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 ⁇ m.
  • the copper foil was then dried at 120°C to obtain a negative electrode sheet coated on one side with a negative electrode material layer.
  • the coating weight of the negative electrode material layer was 100.1 mg/1540 mm2 .
  • the above steps were then repeated on the other side of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode material layer.
  • a negative electrode sheet measuring 661 mm x 78 mm was obtained for future use.
  • the thickness of the negative electrode material layer on one side was 54.5 ⁇ m.
  • the positive electrode active material LiCoO2 , the conductive agent acetylene black, and the binder polyvinylidene fluoride were mixed in a mass ratio of 96.7:1.7:1.6.
  • N-methylpyrrolidone (NMP) was added as a solvent to form a slurry with a solid content of 76 wt%. After vacuum stirring, the slurry was evenly coated on one surface of a 9 ⁇ m thick positive electrode current collector aluminum foil and dried at 120°C to obtain a single-sided positive electrode sheet coated with a positive electrode material layer.
  • the coating weight of the positive electrode material layer was 260 mg/1540 mm2 .
  • FEC fluoroethylene carbonate
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, with the separator positioned between the positive and negative electrode sheets to act as a separator, and then wound to form an electrode assembly.
  • the electrode assembly is placed in an aluminum-plastic film packaging bag, dehydrated at 80°C, and then injected with the electrolyte prepared above.
  • the lithium-ion battery is produced through vacuum packaging, standing, forming, degassing, and trimming.
  • the upper limit of the formation voltage is 4.15V
  • the formation temperature is 70°C
  • the formation standing time is 2 hours.

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Abstract

本申请提供了一种二次电池及其制备方法、电子装置，二次电池包括正极极片、负极极片、电解液以及隔膜；所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面上的负极材料层，所述负极材料层包括硅碳化合物；所述硅碳化合物的球形化度为0.71至1，所述硅碳化合物包括硅元素、碳元素和氧元素，所述硅碳化合物中氧元素的质量百分含量为x1，在200Mpa受压后，所述硅碳化合物中氧元素的质量百分含量为x2，(x2-x1)/x1×100％≤300％。本申请提供的二次电池具有高的首次放电容量、高的首次库伦效率和低的厚度膨胀率。

Description

一种二次电池及其制备方法、电子装置 技术领域
本申请涉及电化学技术领域，特别是涉及一种二次电池及其制备方法、电子装置。
背景技术
相对于传统的含石墨的负极，含硅的负极具有更高的理论比容量和能量密度。使用含硅的负极可以得到更高容量的二次电池，从而提供更长的使用时间和更高的续航能力。然而，含硅的负极也存在一些问题，其中一个重要问题是硅颗粒的易碎性。硅具有较大的体积膨胀率和收缩率，在充放电过程中容易发生体积膨胀和收缩，导致硅颗粒的应力集中和纳米颗粒的破裂。这会导致二次电池的容量衰减、库伦效率和高温存储性能变差。
为了解决硅颗粒易碎的问题，研究人员采取了一系列措施。例如，通过设计和合成核壳结构的硅纳米颗粒，可以提高颗粒的机械稳定性和电子传导性能。此外，引入可弯曲和可伸缩的纳米和微米材料，如碳纳米管、多孔碳和聚合物，可以有效缓解硅颗粒的体积膨胀和收缩压力，改善材料的机械强度和稳定性。但上述核壳结构会降低材料的体积能量密度并限制离子传递速度，且引入纳米微米材料不能解决硅颗粒易碎性的问题。
发明内容
本申请的目的在于提供一种二次电池及其制备方法、电子装置，以提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
需要说明的是，本申请的发明内容中，以锂离子电池作为二次电池的例子来解释本申请，但是本申请的二次电池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二次电池，其包括正极极片、负极极片、电解液以及隔膜；所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面上的负极材料层，所述负极材料层包括硅碳化合物；所述硅碳化合物的球形化度为0.71至1，所述硅碳化合物包括硅元素、碳元素和氧元素，所述硅碳化合物中氧元素的质量百分含量为x1，在200MPa受压后，所述硅碳化合物中氧元素的质量百分含量为x2，(x2-x1)/x1×100％≤300％。本申请二次电池中的硅碳化合物的球形化度和(x2-x1)/x1×100％的值在上述范围内，硅碳化合物颗粒的尖角较少而且在受力后结构完整性好，从而不易与电解液发生副反应，能够提高二次电池的首次放电容量、首次库伦效率及高温存储性能。在本申请的一些实施方案中，所述硅碳化合物的球形化度为0.75至1。
在本申请的一些实施方案中，0.12％≤x1≤2.3％。硅碳化合物中氧元素的质量百分含量x1在上述范围内，得到的硅碳化合物具有良好的耐压强度，而且在受压后其氧含量的变化率小，具有良好的耐氧化能力，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，所述硅碳化合物的10％应变压缩强度大于或等于152.1MPa。硅碳化合物的10％应变压缩强度在上述范围内，说明硅碳化合物的颗粒具有高的抗压强度，在受力后不易破碎，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，所述硅碳化合物中颗粒直径大于或等于10μm的颗粒中硅元素的质量百分含量W1为40.3％至55.7％。通过调控硅元素的质量百分含量在上述范围内，得到的硅碳化合物，具有合适的抗压能力和比容量，从而在提高二次电池的首次放电容量、首次库伦效率及高温存储性能的同时，二次电池还具有较高的能量密度。
在本申请的一些实施方案中，所述硅碳化合物中颗粒直径大于或等于10μm的颗粒中氧元素的质量百分含量W2为0.1％至1.12％，进一步保证硅碳化合物具有良好的耐氧化能力，提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，硅碳化合物中颗粒直径大于或等于10μm的颗粒中碳元素的质量百分含量W3为43.2％至59.2％，而且W1+W3≤99％。可在提高二次电池的首次放电容量、首次库伦效率及高温存储性能的同时，使二次电池具有较高的能量密度。
在本申请的一些实施方案中，所述硅碳化合物的Dv50为5.4μm至8.9μm。通过调控硅碳化合物的Dv50在上述范围内，得到的硅碳化合物的颗粒，表面缺陷较少，受力后不易产生裂纹，抗压能力好，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，所述硅碳化合物的振实密度为0.7g/cc至1.2g/cc。通过调控硅碳化合物的振实密度TD在上述范围内，得到的硅碳化合物振实密度高，有利于减小负极极片的厚度，进而得到的二次电池具有高的能量密度。
在本申请的一些实施方案中，所述硅碳化合物的压实密度在0.83g/cc为1.22g/cc。通过调控硅碳化合物的压实密度PD在上述范围内，得到的硅碳化合物压实密度高，有利于减小负极极片的厚度，进而得到的二次电池具有高的能量密度。
本申请的第二方面提供了一种前述任一实施方案中的二次电池的制备方法，其包括以 下步骤：制备所述正极极片、所述负极极片、所述隔膜和所述电解液，组装得到所述二次电池；
其中，所述负极极片中的所述硅碳化合物的制备方法包括以下步骤：
(1)将酚类化合物、甲醛、氨气与水混合，混合均匀后进行保温反应，再加入乳化剂，混合均匀后进行升温反应得到多孔碳前驱体；
其中，所述酚类化合物、所述甲醛、所述氨气的摩尔比为1:(1.0至2.0):(0.006至0.013)，所述酚类化合物包括间苯二酚、甲酚、壬基酚、芳烷基酚、腰果酚、辛基酚、双酚A或二甲酚中的至少一种；所述保温反应的温度T1为55℃至90℃、时间t1为0.5h至3h；所述乳化剂与所述酚类化合物的质量比为(0.065至0.11):1；所述升温反应的温度T2为100℃至150℃、时间t2为0.5h至5h；
(2)将所述多孔碳前驱体在惰性气氛下进行碳化处理，然后在含第一化合物的气氛中进行活化处理得到多孔碳基体，第一化合物包括二氧化碳或水蒸气；
其中，所述碳化处理的温度T3为450℃至700℃、时间t3为1h至3h；所述含第一化合物的气氛中第一化合物气体的流速V1为1L/min至3L/min，所述活化处理的温度T4为750℃至1100℃、时间t4为6h至14h；
(3)将所述多孔碳基体在惰性气氛下进行预处理后在含硅烷气氛下进行处理，然后升温进行保温处理后在含第二化合物的气氛下进行处理得到所述硅碳化合物，第二化合物包括乙炔、丙烯或甲苯；
其中，所述预处理的温度T5为400℃至550℃、时间t5为1h至3h；所述含硅烷气氛包括甲硅烷、乙硅烷、丙硅烷、苯基硅烷或甲苯基硅烷中的至少一种，所述含硅烷气氛中硅烷气体的流速V2为1.5L/min至3L/min、通气时长t6为220min至420min；保温处理的温度T7为450℃至600℃、时间t7为0.5h至2h；所述含第二化合物的气氛中第二化合物气体的流速V3为2L/min至7L/min、通气时长t8为180min至400min。
本申请的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二次电池或前述任一实施方案中的制备方法制得的二次电池。
本申请的有益效果：
本申请提供了一种二次电池及其制备方法、电子装置，二次电池包括正极极片、负极极片、电解液以及隔膜；所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面上的负极材料层，所述负极材料层包括硅碳化合物；所述硅碳化合物的球形化度为0.71 至1，所述硅碳化合物包括硅元素、碳元素和氧元素，所述硅碳化合物中氧元素的质量百分含量为x1，在200Mpa受压后，所述硅碳化合物中氧元素的质量百分含量为x2，(x2-x1)/x1×100％≤300％。本申请提供的二次电池具有高的首次放电容量、高的首次库伦效率和低的厚度膨胀率。
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
此处所说明的附图用来提供对本申请的进一步理解，构成本申请的一部分，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。
图1为实施例4中的硅碳化合物的电镜照片；
图2为对比例1中的硅碳化合物的电镜照片。
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，以下参照附图并举实施例，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。本领域技术人员基于本申请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，本申请的具体实施方式中，以锂离子电池作为二次电池的例子来解释本申请，但是本申请的二次电池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二次电池，其包括正极极片、负极极片、电解液以及隔膜；负极极片包括负极集流体和设置在负极集流体至少一个表面上的负极材料层，负极材料层包括硅碳化合物。硅碳化合物的球形化度为0.71至1。在本申请的一些实施方案中，硅碳化合物的球形化度为0.75至1。例如，硅碳化合物的球形化度可以为0.71、0.73、0.78、0.8、0.85、0.9、0.95、1或为其间任意两个数值组成的范围。硅碳化合物包括硅元素、碳元素和氧元素，硅碳化合物中氧元素的质量百分含量为x1，在200Mpa受压后，硅碳化合物中氧元素的质量百分含量为x2，(x2-x1)/x1×100％≤300％。在本申请的一些实施方案中，0％＜(x2-x1)/x1×100％≤300％。例如，(x2-x1)/x1×100％的值可以为1％、3％、5％、7％、10％、20％、30％、50％、75％、100％、125％、150％、175％、200％、225％、250％、275％、300％或为其间任意两个数值组成的范围。在本申请中，硅碳化合物中氧元素的质量百分含量x1是指硅碳化合物未经施压处理前硅碳化合物中氧元素的质量百分含量。
硅碳化合物的球形化度可以表征硅碳化合物颗粒的形状，当球形化度较小时，例如小 于0.71，硅碳化合物颗粒的尖角较多，在受力后，尖角除容易形成应力集中导致颗粒破碎，颗粒破碎后的断面会迅速和空气或电解液发生副反应失去活性，从而影响二次电池的首次放电容量和首次库伦效率。而且，颗粒破碎后的断面在高温下极易与电解液发生副反应而产气，从而影响二次电池的高温存储性能。(x2-x1)/x1×100％可以理解为硅碳化合物在经200Mpa受压前后硅碳化合物中氧含量的变化率，当(x2-x1)/x1×100％的值过大时，例如大于300％，说明硅碳化合物受力后颗粒破碎严重、结构完整性较差，将其应用于二次电池，容易存在因颗粒破损带来的氧化副反应的问题，从而影响二次电池的首次放电容量、首次库伦效率及高温存储性能。从而，本申请二次电池中的硅碳化合物的球形化度和(x2-x1)/x1×100％的值在上述范围内，硅碳化合物颗粒的尖角较少而且在受力后结构完整性好，从而不易与电解液发生副反应，能够提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，0.12％≤x1≤2.3％。例如，x1可以为0.12％、0.15％、0.2％、0.3％、0.4％、0.5％、1％、1.2％、1.5％、1.8％、2％、2.1％、2.2％、2.3％或为其间任意两个数值组成的范围。硅碳化合物中氧元素的质量百分含量x1在上述范围内，得到的硅碳化合物具有良好的耐压强度，而且在受压后其氧含量的变化率小，具有良好的耐氧化能力，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，3.8％≤x2≤300％。例如，x2可以为3.8％、4％、4.5％、5％、10％、20％、30％、40％、50％、60％、70％、80％、90％、100％、120％、140％、150％、160％、180％、200％、220％、240％、250％、260％、280％、300％或为其间任意两个数值组成的范围。在200Mpa受压后，硅碳化合物中氧元素的质量百分含量x2在上述范围内说明硅碳化合物在受压后的耐氧化能力强，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，硅碳化合物的10％应变压缩强度F大于或等于152.2MPa。在本申请的一些实施方案中，10％应变压缩强度F大于或等于152.2MPa且小于或等于300MPa。例如，可以为152.2MPa、155MPa、160MPa、180MPa、200MPa、210MPa、220MPa、230MPa、240MPa、250MPa、260MPa、270MPa、280MPa、290MPa、300MPa或为其间任意两个数值组成的范围。硅碳化合物的10％应变压缩强度F在上述范围内，说明硅碳化合物的颗粒具有高的抗压强度，在受力后不易破碎，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，硅碳化合物中颗粒直径大于或等于10μm的颗粒中硅元素的质量百分含量W1为40.3％至55.7％。例如，硅元素的质量百分含量W1可以为40.3％、40.5％、41％、42％、43％、44％、45％、46％、47％、48％、49％、50％、51％、52％、53％、54％、55％、55.7％或为其间任意两个数值组成的范围。直径大于或等于10μm的颗粒中的元素含量更具代表性，通过调控硅元素的质量百分含量W1在上述范围内，得到的硅碳化合物，具有合适的抗压能力和比容量，从而在提高二次电池的首次放电容量、首次库伦效率及高温存储性能的同时，二次电池还具有较高的能量密度。
在本申请的一些实施方案中，硅碳化合物中颗粒直径大于或等于10μm的颗粒中氧元素的质量百分含量W2为0.1％至1.12％，进一步保证硅碳化合物具有良好的耐氧化能力，提高二次电池的首次放电容量、首次库伦效率及高温存储性能。例如，氧元素的质量百分含量W2可以为0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1％、1.1％、1.12％或为其间任意两个数值组成的范围。直径大于或等于10μm的颗粒中的元素含量更具代表性，通过调控氧元素的质量百分含量W2可以在上述范围内，得到的硅碳化合物，具有良好的耐氧化能力，有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，硅碳化合物中颗粒直径大于或等于10μm的颗粒中碳元素的质量百分含量W3为43.2％至59.2％，而且W1+W3≤99％。可在提高二次电池的首次放电容量、首次库伦效率及高温存储性能的同时，使二次电池具有较高的能量密度。例如，碳元素的质量百分含量W3可以为43.2％、43.5％、44％、45％、46％、47％、48％、49％、50％、51％、52％、53％、54％、55％、56％、57％、58％、59％、59.2％或为其间任意两个数值组成的范围。
在本申请的一些实施方案中，硅碳化合物的Dv50为5.4μm至8.9μm。例如，硅碳化合物的Dv50可以为5.4μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、8.5μm、8.9μm或为其间任意两个数值组成的范围。通过调控硅碳化合物的Dv50在上述范围内，得到的硅碳化合物的颗粒，表面缺陷较少，受力后不易产生裂纹，抗压能力好，从而有利于提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
在本申请的一些实施方案中，硅碳化合物的振实密度TD为0.7g/cc至1.2g/cc。例如，振实密度TD可以为0.7g/cc、0.72g/cc、0.74g/cc、0.85g/cc、0.87g/cc、0.90g/cc、0.92g/cc、0.97g/cc、1.01g/cc、1.05g/cc、1.17g/cc、1.19g/cc、1.2g/cc或为其间任意两个数值组成的 范围。通过调控硅碳化合物的振实密度TD在上述范围内，得到的硅碳化合物振实密度高，有利于减小负极极片的厚度，进而得到的二次电池具有高的能量密度。
在本申请的一些实施方案中，硅碳化合物的压实密度PD在0.83g/cc为1.22g/cc。例如，压实密度PD可以为0.83g/cc、0.85g/cc、0.90g/cc、0.93g/cc、0.95g/cc、0.98g/cc、1.00g/cc、1.03g/cc、1.05g/cc、1.08g/cc、1.1g/cc、1.13g/cc、1.15g/cc、1.18g/cc、1.20g/cc、1.22g/cc或为其间任意两个数值组成的范围。通过调控硅碳化合物的压实密度PD在上述范围内，得到的硅碳化合物压实密度高，有利于减小负极极片的厚度，进而得到的二次电池具有高的能量密度。
本申请的第二方面提供了一种前述任一实施方案中的二次电池的制备方法，其包括以下步骤：制备正极极片、负极极片、隔膜和电解液，组装得到二次电池；
其中，负极极片中的硅碳化合物的制备方法包括以下步骤：
(1)将酚类化合物、甲醛、氨气与水混合，混合均匀后进行保温反应，再加入乳化剂，混合均匀后进行升温反应得到多孔碳前驱体。其中，酚类化合物、甲醛、氨气的摩尔比A为1:(1.0至2.0):(0.006至0.013)，酚类化合物包括间苯二酚、甲酚、壬基酚、芳烷基酚、腰果酚、辛基酚、双酚A或二甲酚中的至少一种；保温反应的温度T1为55℃至90℃、时间t1为0.5h至3h；乳化剂与酚类化合物的质量比B为(0.065至0.11):1；升温反应的温度T2为100℃至150℃、时间t2为0.5h至5h。
例如，摩尔比A可以为1:1:0.006、1:1.5:0.006、1:2:0.006、1:1:0.010、1:1.5:0.010、1:2:0.010、1:1:0.013、1:1.5:0.013、1:2:0.013或为其间任意两个比值组成的范围。例如，温度T1可以为55℃、60℃、65℃、70℃、75℃、80℃、85℃、90℃、或为其间任意两个数值组成的范围。例如，时间t1可以为0.5h、1h、1.5h、2h、2.5h、3h或为其间任意两个数值组成的范围。例如，质量比B可以为0.065:1、0.070:1、0.075:1、0.080:1、0.085:1、0.090:1、0.095:1、0.100:1、0.105:1、0.110:1或为其间任意两个比值组成的范围。例如，温度T2可以为100℃、105℃、110℃、115℃、120℃、125℃、130℃、135℃、140℃、145℃、150℃或为其间任意两个数值组成的范围。例如，时间t2可以为0.5h、1h、1.5h、2h、2.5h、3h、3.5h、4h、4.5h、5h或为其间任意两个数值组成的范围。
(2)将多孔碳前驱体在惰性气氛下进行碳化处理，然后在含第一化合物的气氛中进行活化处理得到多孔碳基体，第一化合物包括二氧化碳或水蒸气。其中，碳化处理的温度T3为450℃至700℃、时间t3为1h至3h；含第一化合物的气氛中第一化合物气体的流速V1为 1L/min至3L/min，活化处理的温度T4为750℃至1100℃、时间t4为6h至14h。
例如，温度T3可以为450℃、500℃、550℃、600℃、650℃、700℃或为其间任意两个数值组成的范围。例如，时间t3可以为1h、1.5h、2h、2.5h、3h或为其间任意两个数值组成的范围。例如，流速V1可以为1L/min、1.5L/min、2L/min、2.5L/min、3L/min或为其间任意两个数值组成的范围。例如，温度T4可以为750℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃或为其间任意两个数值组成的范围。例如，时间t4可以为6h、7h、8h、9h、10h、11h、12h、13h、14h或为其间任意两个数值组成的范围。
(3)将多孔碳基体在惰性气氛下进行预处理后在含硅烷气氛下进行处理，然后升温进行保温处理后在含第二化合物的气氛下进行处理得到硅碳化合物，第二化合物包括乙炔、丙烯或甲苯。其中，预处理的温度T5为400℃至550℃、时间t5为1h至3h；含硅烷气氛包括甲硅烷、乙硅烷、丙硅烷、苯基硅烷或甲苯基硅烷中的至少一种，含硅烷气氛中硅烷气体的流速V2为1.5L/min至3L/min、通气时长t6为220min至420min；保温处理的温度T7为450℃至600℃、时间t7为0.5h至2h；含第二化合物的气氛中第二化合物气体的流速V3为2L/min至7L/min、通气时长t8为180min至400min。
例如，温度T5可以为400℃、425℃、450℃、475℃、500℃、525℃、550℃或为其间任意两个数值组成的范围。例如，时间t5可以为1h、1.5h、2h、2.5h、3h或为其间任意两个数值组成的范围。例如，流速V2可以为1.5L/min、1.8L/min、2L/min、2.2L/min、2.5L/min、2.8L/min、3L/min或为其间任意两个数值组成的范围。例如，通气时长t6可以为220min、250min、275min、300min、325min、350min、375min、400min、420min或为其间任意两个数值组成的范围。例如，温度T7可以为400℃、425℃、450℃、475℃、500℃、525℃、550℃、575℃、600℃或为其间任意两个数值组成的范围。例如，时间t7可以为0.5h、0.7h、0.9h、1h、1.2h、1.4h、1.5h、1.7h、2h或为其间任意两个数值组成的范围。例如，流速V3可以为2L/min、3L/min、4L/min、5L/min、6L/min、7L/min或为其间任意两个数值组成的范围。例如，通气时长t8可以为180min、200min、225min、250min、275min、300min、325min、350min、375min、400min或为其间任意两个数值组成的范围。
通过上述步骤(1)得到的多孔碳前驱体的颗粒尖角少，在后续有利于得到球形度高的硅碳化合物。通过步骤(2)中的活化处理，使得多孔碳前驱体内部的孔隙更加丰富，得到的多孔碳基体有利于后续沉积硅材料。步骤(3)中，先通过预处理，可以将多孔碳前驱体的加热至硅烷分解温度，然后通入硅烷气体在多孔碳基体的孔隙中沉积硅材料；升温后进行 保温处理，可以将沉积硅的多孔碳前驱体加热至第二化合物分解温度，最后通入含第二化合物的气体，可以在裸露的沉积硅表面包覆碳材料。从而得到的硅碳化合物球形化度为0.71至1、(x2-x1)/x1×100％≤300％，也即硅碳化合物的球形化度高、受压前后的氧含量变化率小，在受力后结构完整性好，不易与电解液发生副反应，能够提高二次电池的首次放电容量、首次库伦效率及高温存储性能。
本申请对步骤(2)和(3)中惰性气氛中的气体组成和流速不做限定，示例性地，惰性气氛中的气体可以包括但不限于氮气、氩气、氦气等，流速可以为1L/min至10L/min。
在上述步骤(3)结束后还可以对硅碳化合物进行如下处理：将反应产物在鼓风烘箱中热处理，热处理的温度T9为120℃至160℃、时间t9为6h至10h。
在本申请中，上述“设置在负极集流体至少一个表面上的负极材料层”是指，负极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”可以是负极集流体表面的全部区域，也可以是负极集流体表面的部分区域，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，示例性地，复合集流体可以为锂铜复合集流体、碳铜复合集流体、镍铜复合集流体、钛铜复合集流体等。
上述硅碳化合物可以作为负极材料层中的负极活性材料，负极材料层还可以包括其它负极活性材料，本申请对其它负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，其它负极活性材料可以包含但不限于天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO2、尖晶石结构的锂化TiO2-Li4Ti5O12或Li-Al合金中的至少一种。
在本申请的一些实施方案中，负极材料层还可以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，导电剂可以包括但不限于导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、鳞片石墨、石墨烯、金属材料或导电聚合物中的至少一种，导电炭黑可以包括但不限于乙炔黑或科琴黑中的至少一种。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。例如，粘结剂可以包括但不限于聚丙烯酸、聚丙烯酸钠、聚丙烯酸钾、聚丙烯酸锂、聚酰亚胺、聚乙烯醇、羧甲基纤维素、羧甲基纤维素钠、羧甲基纤维素锂、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶、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、聚乙烯吡咯烷酮、聚乙烯、聚丙烯、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙或聚偏二氟乙烯中的至少一种。本申请对负极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。
本申请对负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，负极材料层的厚度为30μm至120μm。本申请对负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，负极集流体的厚度为4μm至15μm。
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。
在本申请中，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材料层。上述“设置于正极集流体至少一个表面上的正极材料层”是指，正极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”可以是正极集流体表面的全部区域，也可以是正极集流体表面的部分区域，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但不限于镍钴锰酸锂(例如NCM811、NCM622、NCM523、NCM111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂(LiCoO2)、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
正极材料层还可以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5μm至20μm，正极材料层的厚度为30μm至120μm。
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，本申请对隔膜没有特别限制，只要能够实现本申请目的即可。例如，隔膜的材料可以包括但不限于聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类、聚酯(例如，聚对苯二甲酸二乙酯(PET)膜)、纤维素、聚酰亚胺(PI)、聚酰胺(PA)、氨纶或芳纶中的至少一种。隔膜的类型可以包括织造膜、非织造膜、微孔膜、复合膜、碾压膜或纺丝膜中的至少一种。
在本申请的一些实施方案中，隔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。
在本申请的一些实施方案中，无机物层包括无机颗粒和粘结剂。本申请对无机颗粒没有特别限制，例如无机颗粒可以包括氧化铝、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。本申请对粘结剂没有特别限制，例如粘结剂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、聚乙烯烷氧、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。在本申请的一些实施方案中，聚合物层包括聚合物，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、聚乙烯吡咯烷酮、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。
在本申请中，隔膜的厚度没有特别限制，只要能实现本申请的目的即可，例如隔膜的厚度可以为3μm至30μm。
在本申请中，电解液包括锂盐和非水溶剂。
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。例如锂盐可以包括但不限于LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、Li2SiF6、双草酸硼酸锂(LiBOB)或二氟硼酸锂中的至少一种。本申请对锂盐在电解液中的含量没有特别限制，只要能实现本申请的目的即可。
本申请对非水溶剂没有特别限制，只要能实现本申请的目的即可，例如非水溶剂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(EMC)中的至少一种。上述环状碳酸酯可以包括但不限于碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、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氟代碳酸乙烯酯(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。本申请对非水溶剂在电解液中的含量没有特别限制，只要能实现本申请的目的即可。
在本申请中，二次电池还包括壳体，用于容纳正极极片、隔膜、负极极片和电解液，以及二次电池领域中已知的其它部件，本申请对上述其它部件不做限定。本申请对壳体没有特别限制，可以为本领域公知的壳体，只要能够实现本申请目的即可。例如，壳体可以为硬壳壳体或柔性壳体。硬壳壳体的材料可以为金属，本申请对金属的种类不做限定，可以采用本领域已知的金属硬壳壳体，只要能实现本申请的目的即可。柔性壳体可以为金属塑膜，例如铝塑膜、钢塑膜等。
本申请的二次电池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，二次电池的制备过程可以包括但不限于以下步骤：将正极极片、隔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，将电极组件放入壳体内，将电解液注入壳体并封口，得到二次电池。或者，将正极极片、隔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，将电极组件置入壳体内，将电解液注入壳体并封口，得到二次电池。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止二次电池内部的压力上升、过充放电。
在本申请的一些实施方案中，本申请的二次电池包括，但不限于：锂离子电池或钠离子电池。在本申请的一些实施方案中，二次电池包括锂离子电池。
本申请的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二次电池或前述任一实施方案中的制备方法制得的二次电池。
本申请对电子装置的种类没有特别限定，其可以是用于现有技术中已知的任何电子装置。在本申请的一些实施方案中，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：
球形化度测试：
利用等效直径法测试硅碳化合物的球形化度，测试方法为采用ZEISS-SEM(sigma-02-33)扫描电子显微镜观察负极材料层沿厚度方向的截面中的硅碳化合物颗粒，测试视野大小为50μm×50μm，对颗粒截面均落在测试视野内的硅碳化合物颗粒进行测试计算，测试上述硅碳化合物颗粒的周长等效直径与颗粒面积等效直径。
球形化度＝周长等效直径/面积等效直径
10％应变压缩强度F测试：
采用岛津MCT系列微小压缩试验机对硅碳化合物颗粒进行测试，将一个硅碳化合物颗粒固定在直径为50μm上压杆和下压板之间，记录上压杆压缩位移为10％颗粒高度时的压力F，并通过压力F和颗粒的投影面积S计算10％应变压缩强度P，公式为P＝F/S。用同样的方法随机测试25个硅碳化合物颗粒，并计算平均值，即可得到硅碳化合物的10％应变压缩强度F。
硅碳化合物颗粒粒度测试：
采用图像分析法进行测试，在背散射模式下，采用ZEISS-SEM(sigma-02-33)拍摄负极材料层沿厚度方向的截面中的硅碳化合物颗粒的显微图像。对颗粒截面均落在显微图像中的硅碳化合物颗粒进行测试计算，利用ImageJ软件对图像中硅碳化合物颗粒进行边缘识别，然后计算出每个颗粒的投影面积，根据等效投影面积计算出每个颗粒的面积等效直径，再对所计算出的面积等效直径进行统计即可得到硅碳化合物的Dv50。
硅碳化合物颗粒硅含量测试：
采用ZEISS-SEM(sigma-02-33)对负极材料层沿厚度方向的截面中硅碳化合物颗粒进行观察。利用能谱仪(EDS)方法测试硅碳化合物颗粒的硅含量，统计50个颗粒周长等效直径大于或等于10μm的颗粒的硅含量和氧含量并求平均值，记为硅碳化合物中颗粒直径大于或等于10μm的颗粒中硅元素的质量百分含量W1和硅碳化合物中颗粒直径大于或等于10μm的颗粒中氧元素的质量百分含量W2。
硅碳化合物中氧元素的质量百分含量及受压后氧含量变化率测试：
采用EDS测试硅碳化合物中氧元素的质量百分含量，记为x1。
将3.0g硅碳化合物粉末样品放入直径为25mm的挤压模具中，然后用电子压力试验机进行加压，压强控制为200MPa，加压位移速率为10mm/min，加压保压时间为30s。保压后进行卸压，将模具中的硅碳化合物取出后在室温环境中暴露在空气中5h，然后利用EDS测试硅碳化合物中氧元素的质量百分含量，记为x2。
受压后硅碳化合物中氧含量变化率＝(x2-x1)/x1×100％。
压实密度PD测试：
将m1＝1.0g硅碳化合物颗粒粉末样品放入直径为13mm的挤压模具中，然后用电子压力试验机进行加压，加压载荷控制为5吨，加压位移速率为10mm/min，加压保压时间为30s。保压后进行卸压，卸压位移速率为30mm/min，卸压后材料的体积为V1，根据 D＝m1/V1计算出硅碳化合物的压实密度PD。
振实密度TD测试：
室温下，将m2＝10.0g硅碳化合物颗粒粉末样品放入体积为100cm3的玻璃量筒中，然后将装有样品的玻璃量筒固定在振动机上，设置振动频率为250次/min，振动次数为5000次。振动结束后读取样品在玻璃量筒中的体积，记为V2，根据PD＝m2/V2计算出硅碳化合物的振实密度TD。
硅碳化合物粉末克容量的测试：
将硅碳化合物粉末、导电剂(SP)、粘结剂(PAA-Li)、碳纳米管(CNTs)、分散剂(CMC)按照质量比84:10:5:0.4:0.6进行混合，加入去离子水得到固含量为48wt％的负极浆料。将负极浆料混合均匀后涂敷到厚度为6μm的铜箔上，120℃条件下烘干，负极材料层的涂布重量为100.1mg/1540mm2。经过冷压、冲片后得到负极极片。其中，单面负极材料层的厚度为54.5μm。
在水氧含量均小于10ppm的手套箱中，将碳酸甲乙酯(EMC)、碳酸乙烯酯(EC)与碳酸二乙酯(DEC)按照1:1:1的体积比进行混合得到混合溶剂，然后加入占上述混合溶剂体积分数为10％的氟代碳酸乙烯酯(FEC)，最后加入锂盐LiPF6，得到电解液。其中，锂盐LiPF6浓度为1mol/L。
在水氧含量均小于10ppm的手套箱中，将上述负极极片、对电极金属锂片、聚丙烯(PP)隔膜及上述电解液组装成纽扣电池。
克容量的测试：在25℃环境中将上述纽扣电池静置6h后，以0.05C的电流放电至5mV，接着以50μA的电流放电至5mV，静置5min后再以10μA的电流放电至5mV，将该放电容量记为G0，静置5min，然后以0.05C的倍率充电至0.8V，将该充电容量记为G1。
硅碳化合物粉末克容量＝G1；硅碳化合物粉末首次库伦效率＝G1/G0×100％。
锂离子电池的首次放电容量及首次库伦效率测试：
在25℃、常压环境下，将新制备的锂离子电池以0.5C倍率恒流充电至4.5V，并恒压充电至0.05C，静置5min，记录该步充电容量为C1；以0.2C倍率恒流放电至3.0V，记录该步放电容量为C2，则C2为锂离子电池的首次放电容量。
锂离子电池的首次库伦效率＝C2/C1×100％。
锂离子电池的高温存储性能测试：
在25℃、常压环境下，将新制备的锂离子电池以0.5C倍率恒流充电至4.5V，并以4.5V恒压充电至0.05C，静置5min，测量该步锂离子电池的厚度并记为H1；将锂离子电池放置在85℃鼓风烘箱中存储24h，然后将锂离子电池取出并冷却至25℃，测量该步锂离子电池厚度并记为H2。
锂离子电池的高温存储厚度膨胀率＝(H2-H1)/H1×100％。用高温存储厚度膨胀率表征锂离子电池的高温存储性能，高温存储厚度膨胀率越小，高温存储性能越好，高温存储厚度膨胀率越大，高温存储性能越差。
实施例1-1
<硅碳化合物的制备>
(1)将酚类化合物间苯二酚、甲醛、氨气按照摩尔比A为1:1.5:0.010混合，混合均匀后进行保温反应，水的加入质量为酚类化合物质量的10倍，保温反应的温度T1为80℃、时间t1为2h；再加入乳化剂F127，乳化剂与酚类化合物的质量比B为0.065:1，搅拌0.5h，混合均匀后进行升温反应，升温反应的温度T2为100℃、时间t2为4h；反应结束后将反应后的溶液过滤及洗涤后得到多孔碳前驱体。
(2)将1000g多孔碳前驱体在氮气气氛下进行碳化处理，氮气的流速为2.5L/min，碳化处理的温度T3为600℃、时间t3为2h；然后在含第一化合物的气氛中进行活化处理得到多孔碳基体，第一化合物为二氧化碳，第一化合物气体的流速V1为2.5L/min，活化处理的温度T4为900℃、时间t4为12h。
(3)将1000g多孔碳基体加入流化床反应器中，在氮气气氛下进行预处理，氮气的流速为10L/min，预处理的温度T5为480℃、时间t5为2h；然后通入含硅烷的气体，含硅烷气体中的硅烷为甲硅烷，硅烷的流速V2为2.5L/min、通气时长t6为280min；然后继续升温进行保温处理，保温处理的温度T7为500℃、时间t7为1h；然后在含第二化合物的气氛下进行处理得到硅碳化合物，第二化合物为乙炔，第二化合物气体的流速V3为5L/min、通气时长t8为300min。
<负极极片的制备>
将上述制备得到的硅碳化合物和人造石墨按照质量比1:9进行混合后作为负极活性材料，将负极活性材料、碳纳米管、羧甲基纤维素锂、聚丙烯酸锂按照质量比97.4:0.2:0.4:2，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，粘度为6000mPa.s。将负极浆料均匀涂覆于厚度为6μm的负极集流体铜箔的一个表面 上，120℃条件下烘干，得到单面涂布负极材料层的负极极片，负极材料层的涂布重量为100.1mg/1540mm2。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材料层的负极极片。经冷压、裁片、分切、焊接极耳后，得到规格为661mm×78mm的负极极片待用。其中，单面负极材料层的厚度为54.5μm。
<正极极片的制备>
将正极活性材料LiCoO2、导电剂乙炔黑、粘结剂聚偏二氟乙烯按照质量比96.7:1.7:1.6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76wt％的浆料，真空搅拌均匀后得到正极浆料。将正极浆料均匀涂覆在厚度为9μm的正极集流体铝箔的一个表面上，120℃条件下烘干，得到单面涂布正极材料层的正极极片，正极材料层的涂布重量为260mg/1540mm2。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材料层的正极极片。经冷压、裁片、分切、焊接极耳，得到规格为661mm×76.5mm的正极极片待用。其中，单面正极材料层的厚度为42μm。
<电解液的制备>
在含水量小于10ppm的环境下，将氟代碳酸乙烯酯(FEC)、碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比为5:10:15:20:50混合得到有机溶剂，然后向有机溶剂中加入电解质盐LiPF6，混合均匀，得到电解液。其中，基于电解液的质量，电解质盐的质量百分含量为12.5％，其余为有机溶剂。
<隔膜>
采用厚度为10μm的多孔聚乙烯薄膜(Celgard公司提供)作为隔膜。
<锂离子电池的制备>
将上述制备的正极极片、隔膜、负极极片按顺序叠好，使隔膜处于正极极片和负极极片中间起到隔离的作用，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，注入上述制备得到的电解液，经过真空封装、静置、化成、脱气、切边等工序得到锂离子电池。其中，化成上限电压为4.15V，化成温度为70℃，化成静置时间为2h。
实施例2至实施例11、实施例13至实施例15
除了按照表1调整相关制备参数以外，其余与实施例1相同。
实施例12
除了在<硅碳化合物的制备>中，步骤(3)完成后还进行如下处理以外，其余与实施1相同：将硅碳化合物在T9＝150℃鼓风烘箱中热处理t9＝8h。
对比例1至对比例7
除了按照表1调整相关制备参数以外，其余与实施例1相同。
对比例8
除了按照表1调整相关制备参数以外，其余与实施例12相同。
各实施例及对比例的制备参数及性能测试如表1所示。

从实施例1至实施例15、对比例1至对比例8可以看出，当硅碳化合物的球形化度和(x2-x1)/x1×100％的值同时在本申请的范围内时，其克容量和首次库伦效率较高，得到的锂离子电池具有高的首次放电容量、更高的首次库伦效率和更低的厚度膨胀率，从而说明锂离子电池的首次放电容量、首次库伦效率及高温存储性能得到提高。
图1为实施例4中制备得到的硅碳化合物，图2为对比例1中制备得到的硅碳化合物，从图中可以看出，实施例4中硅碳化合物颗粒的尖角比对比例1少，从而得到的锂离子电池具有更高的首次放电容量、高的首次库伦效率和更低的厚度膨胀率。
从实施例1至实施例15可以看出，硅碳化合物的氧元素质量百分含量x1、10％应变压缩强度F、硅元素的质量百分含量W1、Dv50、振实密度PD、压实密度D随制备参数的变化而变化，当采用本申请中的制备方法制得的硅碳化合物，上述参数均在本申请的范围内，得到锂离子电池具有高的首次放电容量、高的首次库伦效率和低的厚度膨胀率，从而说明锂离子电池具有较高的首次放电容量、首次库伦效率，以及良好的高温存储性能。
需要说明的是，在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法或物品不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法或物品所固有的要素。
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 (10)

  1. 一种二次电池，其包括正极极片、负极极片、电解液以及隔膜；所述负极极片包括负极集流体和设置在所述负极集流体至少一个表面上的负极材料层，所述负极材料层包括硅碳化合物；所述硅碳化合物的球形化度为0.71至1，所述硅碳化合物包括硅元素、碳元素和氧元素，所述硅碳化合物中氧元素的质量百分含量为x1，在200Mpa下受压后，所述硅碳化合物中氧元素的质量百分含量为x2，(x2-x1)/x1×100％≤300％。
  2. 根据权利要求1所述的二次电池，其中，0.12％≤x1≤2.3％。
  3. 根据权利要求1或2所述的二次电池，其中，所述硅碳化合物的10％应变压缩强度大于或等于152.1MPa。
  4. 根据权利要求1至3中任一项所述的二次电池，其中，所述硅碳化合物中颗粒直径大于或等于10μm的颗粒中硅元素的质量百分含量为40.3％至55.7％。
  5. 根据权利要求1至4中任一项所述的二次电池，其中，所述硅碳化合物的Dv50为5.4μm至8.9μm。
  6. 根据权利要求1至5中任一项所述的二次电池，其中，所述硅碳化合物的振实密度为0.7g/cc至1.2g/cc。
  7. 根据权利要求1至6中任一项所述的二次电池，其中，所述硅碳化合物的压实密度在0.83g/cc为1.22g/cc。
  8. 根据权利要求1至7中任一项所述的二次电池，其中，所述硅碳化合物中颗粒直径大于或等于10μm的颗粒中氧元素的质量百分含量为0.10％至1.12％。
  9. 一种权利要求1至8中任一项所述的二次电池的制备方法，其包括以下步骤：制备所述正极极片、所述负极极片、所述隔膜和所述电解液，组装得到所述二次电池；
    其中，所述负极极片中的所述硅碳化合物的制备方法包括以下步骤：
    (1)将酚类化合物、甲醛、氨气与水混合，混合均匀后进行保温反应，再加入乳化剂，混合均匀后进行升温反应得到多孔碳前驱体；
    其中，所述酚类化合物、所述甲醛、所述氨气的摩尔比为1:(1.0至2.0):(0.006至0.013)，所述酚类化合物包括间苯二酚、甲酚、壬基酚、碳原子数为7至20的芳烷基酚、腰果酚、辛基酚、双酚A或二甲酚中的至少一种；所述保温反应的温度T1为55℃至90℃、时间t1为0.5h至3h；所述乳化剂与所述酚类化合物的质量比为(0.065至0.11):1；所述升温反应的温度T2为100℃至150℃、时间t2为0.5h至5h；
    (2)将所述多孔碳前驱体在惰性气氛下进行碳化处理，然后在含第一化合物的气氛中进行活化处理得到多孔碳基体，第一化合物包括二氧化碳或水蒸气；
    其中，所述碳化处理的温度T3为450℃至700℃、时间t3为1h至3h；所述含第一化合物的气氛中第一化合物气体的流速V1为1L/min至3L/min，所述活化处理的温度T4为750℃至1100℃、时间t4为6h至14h；
    (3)将所述多孔碳基体在惰性气氛下进行预处理后在含硅烷气氛下进行处理，然后升温进行保温处理后在含第二化合物的气氛下进行处理得到所述硅碳化合物，第二化合物包括乙炔、丙烯或甲苯；
    其中，所述预处理的温度T5为400℃至550℃、时间t5为1h至3h；所述含硅烷气氛包括甲硅烷、乙硅烷、丙硅烷、苯基硅烷或甲苯基硅烷中的至少一种，所述含硅烷气氛中硅烷气体的流速V2为1.5L/min至3L/min、通气时长t6为220min至420min；保温处理的温度T7为450℃至600℃、时间t7为0.5h至2h；所述含第二化合物的气氛中第二化合物气体的流速V3为2L/min至7L/min、通气时长t8为180min至400min。
  10. 一种电子装置，其包括权利要求1至8中任一项所述的二次电池或权利要求9中所述的制备方法制得的二次电池。
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CN113066985A (zh) * 2021-03-29 2021-07-02 贝特瑞新材料集团股份有限公司 复合负极材料及其制备方法、锂离子电池
CN116495731A (zh) * 2023-06-30 2023-07-28 北京壹金新能源科技有限公司 多孔碳微球、制备方法及应用和硅碳负极材料
CN116868395A (zh) * 2023-04-07 2023-10-10 宁德时代新能源科技股份有限公司 二次电池及用电装置
CN117497764A (zh) * 2023-12-29 2024-02-02 贝特瑞新材料集团股份有限公司 碳材料、负极材料及其制备方法、电池

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CN113066985A (zh) * 2021-03-29 2021-07-02 贝特瑞新材料集团股份有限公司 复合负极材料及其制备方法、锂离子电池
CN116868395A (zh) * 2023-04-07 2023-10-10 宁德时代新能源科技股份有限公司 二次电池及用电装置
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