WO2024197837A1 - 二次电池及用电装置 - Google Patents

二次电池及用电装置 Download PDF

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Publication number
WO2024197837A1
WO2024197837A1 PCT/CN2023/085554 CN2023085554W WO2024197837A1 WO 2024197837 A1 WO2024197837 A1 WO 2024197837A1 CN 2023085554 W CN2023085554 W CN 2023085554W WO 2024197837 A1 WO2024197837 A1 WO 2024197837A1
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Prior art keywords
silicon
composite material
carbon composite
carbon
secondary battery
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PCT/CN2023/085554
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English (en)
French (fr)
Inventor
徐宁波
邹海林
陈培培
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2023/085554 priority Critical patent/WO2024197837A1/zh
Priority to CN202380044858.5A priority patent/CN119301789A/zh
Priority to EP23929422.6A priority patent/EP4604242A1/en
Publication of WO2024197837A1 publication Critical patent/WO2024197837A1/zh
Priority to US19/210,834 priority patent/US20250279474A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/147—Lids or covers
    • H01M50/148—Lids or covers characterised by their shape
    • H01M50/15—Lids or covers characterised by their shape for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery.
  • the initial coulombic efficiency and cycle capacity retention rate of the battery are improved, thereby optimizing the capacity and cycle performance of the battery.
  • the first aspect of the present application provides a secondary battery, characterized in that it comprises a negative electrode plate and an electrolyte;
  • the negative electrode plate comprises a silicon-carbon composite material having a three-dimensional network cross-linked pore structure;
  • the electrolyte comprises a first component, and the first component comprises at least one of the compounds represented by Formula I and Formula II,
  • M and O can be connected by a single bond or a double bond.
  • M and O can be connected by a double bond, there is no chemical bond between O and R 4 or R 3 ; It means that M1 and O can be optionally connected by a single bond or a double bond.
  • R1 , R2 , R3 , R4 , R5 , R6 , and R7 are each independently selected from fluorine, fluorine-substituted or unsubstituted C1 - C10 hydrocarbon groups, aryl groups, carbonyl groups, carboxyl groups, ester groups, cyano groups, silane groups, or ether groups; and M and M1 each independently contain P, S, Si, or B.
  • the silicon-carbon composite material with a three-dimensional network cross-linked pore structure has a stable porous skeleton and good mechanical strength. It can effectively reduce the volume change of silicon before and after charging and discharging while loading a high silicon content, thereby improving the cycle performance of the battery.
  • the M element of the first component in the electrolyte can be combined with the active groups on the silicon-carbon composite material, such as hydroxyl, carboxyl, and amino groups, to stabilize the active groups, reduce their consumption of active lithium, improve the first coulomb effect of the battery, and improve the capacity of the battery.
  • the stability of the active groups on the silicon-carbon composite material can also further reduce the capacity attenuation of the battery during the cycle and improve the cycle performance of the battery.
  • the first component additive can generate inorganic substances containing M elements in the solid electrolyte membrane (SEI) on the surface of the silicon-carbon composite material, such as phosphates, sulfates, etc., which can further improve the strength of the SEI membrane, reduce its rupture caused by the expansion of the silicon negative electrode, and improve the battery cycle performance.
  • SEI solid electrolyte membrane
  • the specific surface area of the silicon-carbon composite material is SSA m 2 /g
  • the mass proportion of the first component is EL g/g
  • EL SSA is 0.0001 ⁇ 0.03, and can be optionally 0.0004 ⁇ 0.01.
  • the ratio EL:SSA between the mass proportion of the first component in the electrolyte and the specific surface area SSA of the silicon-carbon composite material meets the above range, the first component can effectively "passivate" the active groups on the silicon-carbon composite material, thereby improving the capacity and cycle performance of the battery.
  • the mass proportion of the first component is EL g/g, in the peripheral region of the silicon-carbon composite material, the mass percentage of silicon element in the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material is B1, wherein the peripheral region of the silicon-carbon composite material is a region extending from the outer surface of the silicon-carbon composite material to the inside of the silicon-carbon composite material within a distance of r/2, r represents the short diameter of the silicon-carbon composite material,
  • EL: B1 is 0.001 ⁇ 0.1, and can be optionally 0.005 ⁇ 0.06.
  • the silicon elements in the peripheral area are more likely to have residual active groups during the preparation process, and are not easily bound by the carbon skeleton, and the volume expansion is more significant.
  • the ratio between the mass proportion of the first component in the electrolyte and the mass percentage content B1 of the silicon element in the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material meets the above range, it is beneficial to "passivate" the active groups on the silicon element through the first component, and further improve the first coulombic efficiency and cycle capacity retention rate of the battery.
  • the total pore volume of pores with a pore size greater than 100 nm in the silicon-carbon composite material is V1 g/cm 3 , based on the total mass of the electrolyte, the mass ratio of the first component is EL g/g, and EL:V1 is 1-30, preferably 2-15.
  • the first component can easily enter the pore structure of the silicon-carbon composite material, forming mutual cooperation with it to further improve the capacity utilization level and cycle capacity retention rate of the battery.
  • the mass percentage A1 of the carbon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material and the mass percentage B1 of the silicon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material satisfy 0.8 ⁇ B1/A1 ⁇ 2.5, optionally, 1 ⁇ B1/A1 ⁇ 1.5.
  • the mass of silicon in the pore structure of the silicon-carbon composite material is relatively high, which can significantly improve the capacity of the negative electrode active material, and the voltage for metal ion embedding is low, which is conducive to the embedding of metal ions, thereby improving the cycle performance of the secondary battery.
  • the three The 3D network cross-linked pore structure can inhibit the volume expansion of silicon during the cycle, improve the structural stability of the negative electrode active material, and thus improve the cycle performance of the battery.
  • the mass percentage A of the carbon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material has a decreasing tendency along the direction from the geometric center of the silicon-carbon composite material to the outer surface of the silicon-carbon composite material
  • the mass percentage B of the silicon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material has an increasing tendency along the direction from the geometric center of the silicon-carbon composite material to the outer surface of the silicon-carbon composite material.
  • the geometric center of the silicon-carbon composite material can be equivalent to the geometric center of the rectangular parallelepiped tangent thereto.
  • the mass percentage A of the carbon element gradually decreases
  • the mass percentage B of the silicon element gradually increases
  • the silicon content in the pore structure of the silicon-carbon composite material gradually increases.
  • the silicon content is relatively high, which can significantly improve the capacity of the negative electrode active material.
  • the silicon content increases from the outer surface to the center, which makes the surface active functional groups of the silicon-based particles continue to decrease, and the inhibitory effect of the carbon-based particles on the expansion of the silicon element becomes more and more significant, thereby further improving the capacity and cycle performance of the battery.
  • the specific surface area SSA of the silicon-carbon composite material satisfies: 2m 2 /g ⁇ SSA ⁇ 10m 2 /g; optionally, 3m 2 /g ⁇ SSA ⁇ 7m 2 /g.
  • the specific surface area SSA of the silicon-carbon composite material meets the above range, the specific surface area of the silicon-carbon composite material is large, the kinetic properties of the material are good, and it is beneficial to improve the first coulombic efficiency of the battery.
  • the silicon-carbon composite material includes carbon matrix particles and silicon nanoparticles, the carbon matrix particles include a three-dimensional network cross-linked pore structure; at least a portion of the silicon nanoparticles are disposed in the three-dimensional network cross-linked pore structure.
  • the carbon matrix particles of the present application have a stable porous skeleton structure, strong supporting capacity, high stress resistance, and excellent mechanical properties and electrical conductivity; the carbon matrix particles include a three-dimensional network cross-linked pore structure, which provides more space for embedding silicon-based nanoparticles, and can be used for large-scale silicon storage, effectively increasing the silicon loading capacity in the silicon-carbon composite material.
  • the conductivity of the silicon-carbon composite material can be improved, while the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the silicon-based nanoparticles can be fully withstood.
  • the stress change of the particles ensures the structural stability of the silicon-carbon composite material and improves the cycle stability and lithium storage capacity of the silicon-carbon composite material. Therefore, when the silicon-carbon composite material is used in a secondary battery, the cycle performance and energy density of the secondary battery can be improved.
  • the silicon nanoparticles include one or more of silicon oxide compounds, pre-lithium silicon oxide compounds, amorphous silicon, crystalline silicon and silicon-carbon composites, and may be amorphous silicon.
  • the carbon matrix includes one or more of graphite, soft carbon, and hard carbon.
  • the mass ratio of the silicon nanoparticles in the silicon-carbon composite material is greater than or equal to 40%, and can be optionally 40-60%.
  • the negative electrode material used in the secondary battery of the present application achieves a high loading amount of silicon nanoparticles in the negative electrode material by adopting a carbon-based material having a three-dimensional network cross-linked pore structure, so that the silicon-carbon composite material has a high capacity and can further improve the energy density of the battery.
  • the ratio of the powder compaction density P11g/ cm3 of the silicon-carbon composite material tested after one powder compaction under a force of 20000N to the compaction density P21g/ cm3 of the silicon-carbon composite material tested after 20 powder compactions under a force of 20000N satisfies: 1.00 ⁇ P21/P11 ⁇ 1.20, optionally, 1.02 ⁇ P21/P11 ⁇ 1.10.
  • the silicon-carbon composite material When the ratio of P21/P11 satisfies the above range, the silicon-carbon composite material has a higher gram capacity and better compression resistance, which improves the structural stability of the negative electrode film layer, so that the secondary battery containing this material has a higher energy density and better cycle performance.
  • the powder compaction density P11 g/cm 3 of the silicon-carbon composite material tested after one powder compaction under a force of 20,000 N satisfies: 1.10 ⁇ P11 ⁇ 1.40, optionally, 1.12 ⁇ P11 ⁇ 1.35.
  • the negative electrode film layer has a higher compaction density, so that the secondary battery has a higher energy density.
  • the compound represented by formula I is selected from one or more of the following compounds:
  • the compound represented by formula II is selected from one or more of the following compounds:
  • the compound shown in the above formula I and the compound shown in the above formula II include B, P, S or Si elements.
  • the B element and the Si element can combine with the oxygen element in the surface active group of the silicon-carbon composite material by providing an empty orbital, play the role of "passivating” the active group, and improve the first coulomb efficiency and cycle performance of the battery.
  • the P element and the S element can combine with the hydrogen element in the surface active group of the silicon-carbon composite material by providing electrons, play the role of "passivating” the active group, and improve the first coulomb efficiency and cycle performance of the battery.
  • the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • a second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;
  • FIG. 3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the terms “include” and “comprising” mentioned in this application may be open-ended or closed-ended.
  • the terms “include” and “comprising” may mean that other components not listed may also be included or contained, or may only include or contain List the components.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • Silicon-based materials have high specific capacity and are suitable for negative electrode materials of high energy density batteries.
  • silicon-based materials have a large volume expansion rate during the charging and discharging process, resulting in poor battery cycle performance.
  • silicon-based materials are easy to introduce more surface groups during the production and preparation process. For example, silicon-based materials are easy to introduce carboxyl or hydroxyl groups on their surface when treated with acid, and silicon-based materials are easy to introduce amino groups on their surface when treated with alkali. The presence of surface groups easily consumes active lithium and affects the capacity of the battery.
  • a secondary battery which comprises: a negative electrode plate and an electrolyte, wherein the negative electrode plate comprises a silicon-carbon composite material having a three-dimensional network cross-linked pore structure; the electrolyte comprises a first component, wherein the first component comprises at least one of the compounds represented by Formula I and Formula II,
  • M and O can be connected by a single bond or a double bond.
  • M and O can be connected by a double bond, there is no chemical bond between O and R 4 or R 3 ;
  • M1 and O can be connected by a single bond or a double bond, and when M1 and O are connected by a double bond, there is no chemical bond between O and R7 ;
  • R1 , R2 , R3 , R4 , R5 , R6 , and R7 are each independently selected from fluorine, fluorine-substituted or unsubstituted C1 - C10 hydrocarbon groups, aryl groups, carbonyl groups, carboxyl groups, ester groups, cyano groups, silane groups, or ether groups, and M and M1 each independently contain P, S, Si, or B.
  • C 1 to C 10 hydrocarbon group refers to a hydrocarbon group having 1 to 10 carbon atoms.
  • aryl refers to a group formed by losing a hydrogen atom from an aromatic hydrocarbon molecule.
  • Non-limiting examples of aryl include phenyl, naphthyl, and the like.
  • ester group refers to Wherein, R is a C 1 -C 3 hydrocarbon group.
  • cyano refers to -C ⁇ N.
  • silyl refers to -Si( R1 )( R2 )( R3 ) groups, wherein R1 , R2 , R3 are each independently selected from hydrogen, substituted or unsubstituted C1 - C3 alkyl.
  • silyl groups include but are not limited to -SiH3 , -Si( CH3 ) 3 .
  • ether group refers to -RO-R'-, wherein R and R' are C1 - C3 hydrocarbon groups.
  • the three-dimensional network cross-linked pore structure generally refers to a structure in which two or more pores are interconnected or interlaced and share pore volume in a silicon-carbon composite material, especially in a pore structure formed by carbon matrix particles.
  • the pore structure of the silicon-carbon composite material can be tested using equipment and methods known in the art. For example, it can be tested by using a scanning electron microscope (such as ZEISS Sigma 300). As an example, the following steps can be followed: first, the negative electrode sheet containing the silicon-carbon composite material is cut into a sample to be tested of a certain size (for example, 6mm ⁇ 6mm), and the sample to be tested is clamped with two conductive and thermally conductive thin sheets (such as copper foil), and the sample to be tested and the thin sheet are glued and fixed with glue (such as double-sided tape), and a certain mass (such as about 400g) of a flat iron block is pressed for a certain time (such as 1h) to make the gap between the sample to be tested and the copper foil as small as possible, and then the edges are trimmed with scissors, and glued to the sample stage with conductive glue, and the sample slightly protrudes from the edge of the sample stage.
  • a scanning electron microscope such as ZEISS Sigma 300.
  • the sample stage into the sample holder and lock it, turn on the power of the argon ion cross-section polisher (such as IB-19500CP) and evacuate (for example, 10Pa-4Pa), set the argon gas flow rate (for example, 0.15MPa) and voltage (for example, 8KV) and polishing time (for example, 2 hours), adjust the sample stage to the swing mode and start polishing.
  • the argon ion cross-section polisher such as IB-19500CP
  • evacuate for example, 10Pa-4Pa
  • the argon gas flow rate for example, 0.15MPa
  • voltage for example, 8KV
  • polishing time for example, 2 hours
  • the silicon-carbon composite material with a three-dimensional network cross-linked pore structure has a stable porous skeleton and good mechanical strength. It can effectively reduce the volume change of silicon before and after charging and discharging while loading a high silicon content, thereby improving the cycle performance of the battery.
  • the M element of the first component in the electrolyte can combine with the active groups on the silicon-carbon composite material, such as hydroxyl, carboxyl, and amino groups, to stabilize the active groups, reduce their consumption of active lithium, improve the first coulomb effect of the battery, and improve the capacity of the battery.
  • the stability of the active groups on the silicon-carbon composite material can also further reduce the capacity attenuation of the battery during the cycle and improve the cycle performance of the battery.
  • the first component additive can generate inorganic substances containing M elements in the solid electrolyte membrane (SEI) on the surface of the silicon-carbon composite material, such as phosphates, sulfates, etc., which can further improve the strength of the SEI membrane, reduce its rupture caused by the expansion of the silicon negative electrode, and improve the battery cycle performance.
  • SEI solid electrolyte membrane
  • the specific surface area of the silicon-carbon composite material is SSA m 2 /g, based on the total mass of the electrolyte, the mass proportion of the first component is EL g/g, and EL:SSA is 0.0001-0.03, and can be 0.0004-0.01.
  • the specific surface area of the silicon-carbon composite material is SSA m 2 /g
  • the mass proportion of the first component in the electrolyte is EL g/g
  • EL:SSA can be selected from 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02 or 0.03 g/m 2 .
  • the specific surface area SSA has a well-known meaning in the art, and the surface area is usually expressed in units of m2 /g, and can be tested by methods and instruments known in the art. For example, it can be tested by an inert gas (such as nitrogen) adsorption specific surface area analysis test method according to GB/T 19587-2017, and calculated by the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by a Tri-Star 3020 specific surface area pore size analysis tester from Micromeritics, USA.
  • an inert gas such as nitrogen
  • BET Brunauer Emmett Teller
  • the ratio EL:SSA between the mass proportion of the first component in the electrolyte and the specific surface area SSA of the silicon-carbon composite material meets the above range, the first component can effectively "passivate" the active groups on the silicon-carbon composite material, thereby improving the capacity and cycle performance of the battery.
  • the mass percentage of the first component in the electrolyte is EL g/g.
  • the mass percentage of silicon element in the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material is B1, wherein the peripheral region of the silicon-carbon composite material is a region extending from the outer surface of the silicon-carbon composite material to the inside of the silicon-carbon composite material within a distance of r/2, r represents the short diameter of the silicon-carbon composite material, and EL: B1 is 0.001 to 0.1, and can be optionally 0.005 to 0.06.
  • the three-axis diameter characterization method can be used to characterize the particle size of the silicon-carbon composite material.
  • the specific characterization method is as follows: the long diameter l and the short diameter r are measured on the plane projection of the silicon-carbon composite material, and the thickness h of the silicon-carbon composite material is measured in the direction perpendicular to the projection plane; it can also be understood as placing the silicon-carbon composite material in a rectangular block tangent to it, with the long side of the rectangular block being l, the short side being r, and the thickness being h, to reflect the actual size of the silicon-carbon composite material.
  • the silicon content can be determined by emission spectroscopy test (Inductively coupled plasma, ICP), as follows: take a silicon-carbon composite material as a sample, digest the sample with aqua regia and hydrofluoric acid HF, take the solution digested for 15 minutes and the solution completely digested for ICP testing, and the silicon content in the solution digested for 45 minutes is the silicon content in the "peripheral area of the silicon-carbon composite material".
  • ICP Inductively coupled plasma
  • the ratio EL:B1 between the mass percentage of the first component in the electrolyte and the mass percentage B1 of the silicon element in the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material can be selected to be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1.
  • the silicon elements in the peripheral area are more likely to have residual active groups during the preparation process, and are not easily bound by the carbon skeleton, and the volume expansion is more significant.
  • the ratio between the mass proportion of the first component in the electrolyte and the mass percentage content B1 of the silicon element in the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material meets the above range, it is beneficial to "passivate" the active groups on the silicon element through the first component, and further improve the first coulombic efficiency and cycle capacity retention rate of the battery.
  • the total pore volume of pores with a pore size greater than 100 nm in the silicon-carbon composite material is V1 cm 3 /g
  • the ratio of the mass proportion EL of the first component in the electrolyte to the total pore volume V1 of pores with a pore size greater than 100 nm in the silicon-carbon composite material is EL:V1. 1 ⁇ 30, optional 2 ⁇ 15.
  • the pore volume test method for pores of different sizes can refer to GB/T 19587-2004, adopt the mesopore pore size distribution test BJH (Barret Joyner Halenda), use the gas adsorption and desorption method to test and select the adsorption branch data under the micro-mesopore model, and measure and count the total pore volume V1 of pores with a pore size greater than 100nm.
  • BJH Barret Joyner Halenda
  • the total pore volume of pores with a pore size greater than 100 nm in the silicon-carbon composite material is V1 cm 3 /g
  • the ratio EL:V1 between the mass proportion EL of the first component in the electrolyte and the total pore volume V1 of pores with a pore size greater than 100 nm in the silicon-carbon composite material may preferably be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30.
  • the first component can easily enter the pore structure of the silicon-carbon composite material, forming mutual cooperation with it to further improve the capacity utilization level and cycle capacity retention rate of the battery.
  • the mass percentage A1 of the carbon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material and the mass percentage B1 of the silicon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material satisfy 0.8 ⁇ B1/A1 ⁇ 2.5, optionally, 1 ⁇ B1/A1 ⁇ 1.5.
  • the carbon content can be analyzed by infrared absorption carbon-sulfur content analysis according to the GB/T20123-2006 test standard, as follows: take the silicon-carbon composite material as a sample, and the carbon content at 20 minutes of testing is the carbon content of the "peripheral area of the silicon-carbon composite material".
  • the mass of silicon in the pore structure of the silicon-carbon composite material is relatively high, which can significantly improve the capacity of the negative electrode active material, and the voltage of metal ion embedding is low, which is conducive to the embedding of metal ions, thereby improving the cycle performance of the secondary battery.
  • the three-dimensional network cross-linked pore structure can inhibit the volume expansion of silicon during the cycle, improve the structural stability of the negative electrode active material, and further improve the cycle performance of the battery.
  • the carbon element of the silicon-carbon composite material is relative to the carbon element of the silicon-carbon composite material.
  • the mass percentage A of the total mass of the material has a tendency to decrease along the direction from the geometric center of the silicon-carbon composite material to the outer surface of the silicon-carbon composite material
  • the mass percentage B of the silicon element of the silicon-carbon composite material relative to the total mass of the silicon-carbon composite material has an increasing tendency along the direction from the geometric center of the silicon-carbon composite material to the outer surface of the silicon-carbon composite material.
  • the geometric center of the silicon-carbon composite material can be equivalent to the geometric center of a rectangular parallelepiped tangent thereto.
  • the mass percentage A of the carbon element gradually decreases
  • the mass percentage B of the silicon element gradually increases
  • the silicon content in the pore structure of the silicon-carbon composite material gradually increases.
  • the silicon content is relatively high, which can significantly increase the capacity of the negative electrode active material.
  • the silicon content increases from the outer surface to the center, which makes the surface active functional groups of the silicon-based particles continue to decrease, and the inhibitory effect of the carbon-based particles on the expansion of the silicon element becomes more and more significant, thereby further improving the capacity and cycle performance of the battery.
  • the specific surface area SSA of the silicon-carbon composite material satisfies: 2m 2 /g ⁇ SSA ⁇ 10m 2 /g; optionally, 3m 2 /g ⁇ SSA ⁇ 7m 2 /g.
  • the specific surface area SSA of the silicon-carbon composite material may be 2 m 2 /g, 3 m 2 /g, 4 m 2 /g, 5 m 2 /g, 6 m 2 /g, 7 m 2 /g, 8 m 2 /g, 9 m 2 /g or 10 m 2 /g, or a range consisting of any two of the above values.
  • the specific surface area SSA of the silicon-carbon composite material meets the above range, the specific surface area of the silicon-carbon composite material is large, the kinetic properties of the material are good, and it is beneficial to improve the first coulombic efficiency of the battery.
  • the silicon-carbon composite material includes: carbon matrix particles and silicon nanoparticles, the carbon matrix particles include a three-dimensional network cross-linked pore structure, and at least a portion of the silicon nanoparticles are disposed in the three-dimensional network cross-linked pore structure.
  • the carbon matrix particles of the present application have a stable porous skeleton structure, strong supporting capacity, high stress resistance, and excellent mechanical properties and electrical conductivity; the carbon matrix particles include a three-dimensional network cross-linked pore structure, which provides more space for embedding silicon-based nanoparticles, and can be used to store a large amount of silicon, effectively increasing the silicon loading capacity in the silicon-carbon composite material.
  • the conductivity of the silicon-carbon composite material can be improved, while the volume effect of silicon in the process of lithium insertion and extraction can be alleviated, and the stress changes of silicon-based nanoparticles can be fully withstood, thereby ensuring the structural stability of the silicon-carbon composite material and improving the silicon-carbon composite material.
  • the material's cycle stability and lithium storage capacity Therefore, when the silicon-carbon composite material is applied to a secondary battery, the cycle performance and energy density of the secondary battery can be improved.
  • the silicon nanoparticles include one or more of silicon-oxygen compounds, amorphous silicon, crystalline silicon, and silicon-carbon composites, and may be amorphous silicon.
  • the carbon matrix includes one or more of graphite, soft carbon, and hard carbon.
  • the mass ratio of silicon nanoparticles in the silicon-carbon composite material is greater than or equal to 40%, and can be optionally 40-60%.
  • the mass ratio of silicon nanoparticles in the silicon-carbon composite material may be 40%, 45%, 50%, 55% or 60%.
  • the quality of silicon nanoparticles in silicon-carbon composite materials can be tested by methods and equipment known in the art, for example, it can be measured with reference to EPA 6010D-2014 standard; specifically, ICP-OES (elemental analysis-inductively coupled plasma optical emission spectrometry) testing can be used.
  • the solid to be tested is first dissolved into a liquid with a strong acid, and then the liquid is introduced into an ICP light source by atomization.
  • the gaseous atoms to be tested are further ionized and excited in a strong magnetic field, and then recovered from the excited state to the ground state. In the above process, energy is released and recorded as different characteristic spectral lines for quantitative analysis of trace elements.
  • the negative electrode material used in the secondary battery of the present application achieves a high loading amount of silicon nanoparticles in the negative electrode material by adopting a carbon-based material having a three-dimensional network cross-linked pore structure, so that the silicon-carbon composite material has a high capacity and can further improve the energy density of the battery.
  • the ratio of the powder compaction density P11g/ cm3 of the silicon-carbon composite material tested after one powder compaction under a force of 20000N to the compaction density P21g/ cm3 of the silicon-carbon composite material tested after 20 powder compactions under a force of 20000N satisfies: 1.00 ⁇ P21/P11 ⁇ 1.20, optionally, 1.02 ⁇ P21/P11 ⁇ 1.10.
  • the silicon-carbon composite material When the ratio of P21/P11 satisfies the above range, the silicon-carbon composite material has a higher gram capacity and better compression resistance, which improves the structural stability of the negative electrode film layer, so that the secondary battery containing this material has a higher energy density and better cycle performance.
  • the powder compaction density P11 g/cm 3 of the silicon-carbon composite material tested after one powder compaction under a force of 20000 N satisfies: 1.10 ⁇ P11 ⁇ 1.40, optional Ground, 1.12 ⁇ P11 ⁇ 1.35.
  • the negative electrode film layer has a higher compaction density, so that the secondary battery has a higher energy density.
  • the compound represented by Formula I is selected from one or more of the following compounds:
  • the compound represented by formula II is selected from one or more of the following compounds:
  • the compound shown in the above formula I and the compound shown in the above formula II include B, P, S or Si elements.
  • the B element and the Si element can combine with the oxygen element in the surface active group of the silicon-carbon composite material by providing an empty orbital, play the role of "passivating” the active group, and improve the first coulomb efficiency and cycle performance of the battery.
  • the P element and the S element can combine with the hydrogen element in the surface active group of the silicon-carbon composite material by providing electrons, play the role of "passivating” the active group, and improve the first coulomb efficiency and cycle performance of the battery.
  • a secondary battery includes a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS). One less.
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • a secondary battery includes a positive electrode sheet, which includes a positive electrode collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the lithium transition metal oxide examples of the material may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode active material is a nickel-rich material, and the molar ratio of nickel in the transition metal of the positive electrode active material is higher than 85%.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • an electric device comprising the secondary battery of any embodiment.
  • FIG1 is a secondary battery 1 of a square structure as an example.
  • the outer package may include a shell 11 and a cover plate 13.
  • the shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 12 through a winding process or a lamination process.
  • the electrode assembly 12 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 12.
  • the number of electrode assemblies 12 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the electrical device includes the secondary battery provided in the present application.
  • the secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • FIG3 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • a gas containing a silicon precursor is provided to carbon matrix particles having a three-dimensional network cross-linked pore structure; silicon nanoparticles attached to the carbon matrix particles are generated from the silicon precursor by chemical vapor deposition to obtain a silicon-carbon composite material.
  • the silicon precursor is silane and the carbon matrix is hard carbon.
  • the negative electrode active material silicon-carbon composite material
  • conductive carbon black thickener sodium carboxymethyl cellulose (CMC)
  • binder styrene-butadiene rubber latex SBR
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 ), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in a solvent N-methylpyrrolidone (NMP) at a weight ratio of 93:2:5, and the positive electrode slurry was obtained after being fully stirred and mixed; then the positive electrode slurry was evenly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent, and 1wt% tri(trimethylsilyl)borate is added as an additive to prepare an electrolyte with a lithium salt concentration of 1 mol/L.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the lithium-ion battery product of Example 1.
  • the preparation method of the battery of Comparative Example 1 is similar to that of Example 1, but the first component is not added to the electrolyte.
  • the preparation method of the battery of Comparative Example 2 is similar to that of Example 1, but the pore structure of the carbon matrix particles of Comparative Example 2 is a honeycomb pore structure.
  • the preparation method of the battery of Comparative Example 3 is similar to that of Example 2, but the carbon
  • the pore structure of the matrix particles is a honeycomb pore structure.
  • the preparation method of the battery of Comparative Example 4 is similar to that of Example 3, but the pore structure of the carbon matrix particles of Comparative Example 4 is a honeycomb pore structure.
  • the preparation method of the battery of Comparative Example 5 is similar to that of Example 4, but the pore structure of the carbon matrix particles of Comparative Example 5 is a honeycomb pore structure.
  • the preparation method of the battery of Comparative Example 6 is similar to that of Example 5, but the pore structure of the carbon matrix particles of Comparative Example 6 is a honeycomb pore structure.
  • the pore structure of the silicon-carbon composite material can be tested using equipment and methods known in the art. For example, it can be tested by using a scanning electron microscope (such as ZEISS Sigma 300). As an example, the following steps can be followed: first, the negative electrode sheet containing the silicon-carbon composite material is cut into a sample to be tested of a certain size (for example, 6mm ⁇ 6mm), and the sample to be tested is clamped with two conductive and thermally conductive thin sheets (such as copper foil), and the sample to be tested and the thin sheet are glued and fixed with glue (such as double-sided tape), and a certain mass (such as about 400g) of a flat iron block is pressed for a certain time (such as 1h) to make the gap between the sample to be tested and the copper foil as small as possible, and then the edges are trimmed with scissors, and glued to the sample stage with conductive glue, and the sample slightly protrudes from the edge of the sample stage.
  • a scanning electron microscope such as ZEISS Sigma 300.
  • the sample stage into the sample holder and lock it, turn on the power of the argon ion cross-section polisher (such as IB-19500CP) and draw a vacuum (such as 10Pa-4Pa), set the argon gas flow rate (such as 0.15MPa) and voltage (such as 8KV) and polishing time (such as 2 hours), adjust the sample stage to the rocking mode and start polishing.
  • the argon ion cross-section polisher such as IB-19500CP
  • draw a vacuum such as 10Pa-4Pa
  • the argon gas flow rate such as 0.15MPa
  • voltage such as 8KV
  • polishing time such as 2 hours
  • the specific surface area was tested by gas adsorption method according to GB/T19587-2017 test standard. The details are as follows: the battery was disassembled, the negative electrode was scraped, and the binder was removed by high temperature ablation. The powder material is used as a silicon-carbon composite material sample. The sample tube is immersed in liquid nitrogen at -196°C. The adsorption amount of nitrogen on the solid surface at different pressures is measured at a relative pressure of 0.05-0.30. The monolayer adsorption amount of the sample is obtained based on the BET multilayer adsorption theory and its formula, thereby calculating the specific surface area of the negative electrode active material.
  • the pore size is tested by the gas adsorption method according to the GB/T19587-2017 & GB/T21650.2-2008 test standards. The details are as follows: take the silicon-carbon composite material as the sample, immerse the sample tube in liquid nitrogen at -196°C, and adsorb the nitrogen on the material to be tested at a relative pressure of 0-1.
  • the pore size distribution of the porous material is characterized based on the relationship between the volume of each pore size and the corresponding partial pressure.
  • GB/T 24533-2009 and use an electronic pressure testing machine (such as UTM7305) for testing: place a powder sample of a certain mass G on a special compaction mold (bottom area S), set different pressures (20000N or 50000N can be used in this application), maintain the pressure for 20s, release the pressure, wait for 10s, read the thickness H of the powder after compaction under the pressure on the equipment, and calculate the compaction density under the pressure.
  • the compaction density of the material under the pressure G/(H*S).
  • the elemental analysis of ion polished cross section was carried out by energy dispersive spectrometry, and the element distribution of the particle cross section was tested according to the GB-T17359-2012 test standard.
  • the silicon content was determined by emission spectroscopy (Inductively coupled plasma, ICP), as follows: a silicon-carbon composite material was taken as a sample, and aqua regia and hydrofluoric acid were used to measure the silicon content. The sample was digested with HF, and the solution digested for 15 minutes and the solution completely digested were taken for ICP testing. The silicon content in the solution digested for 45 minutes was the silicon content in the "peripheral area of the silicon-carbon composite material", and the difference between the silicon content in the solution completely digested and that in the solution digested for 1 hour was the silicon content in the "central area of the silicon-carbon composite material".
  • ICP Inductively coupled plasma
  • the infrared absorption method for carbon-sulfur content analysis is carried out in accordance with the GB/T20123-2006 test standard, as follows: a silicon-carbon composite material is taken as a sample, and the carbon content at 20 minutes of testing is the carbon content of the "peripheral area of the silicon-carbon composite material", and the difference between the carbon content at 20 minutes of testing and at the end of the test is the carbon content of the "peripheral area of the silicon-carbon composite material".
  • the short diameter r is measured according to the three-axis characterization method, specifically as follows: the short diameter r is measured on a plane projection diagram of the silicon-carbon composite material.
  • the secondary batteries prepared in the examples and comparative examples were charged at a constant current of 0.33C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current of ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2V.
  • the first charge capacity of the battery cell divided by the discharge capacity is the coulomb efficiency of the first cycle of the battery.
  • the secondary batteries prepared in the examples and comparative examples were charged at a constant current of 0.5C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current of ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2V, left to stand for 5 minutes. This was a charge and discharge cycle.
  • the battery was subjected to a cyclic charge and discharge test according to this method, and the capacity retention rate of the lithium-ion battery after 800 cycles was calculated.
  • the negative electrode active materials of the batteries of Examples 1-17 are three
  • the battery of Examples 1-17 shows higher first coulombic efficiency and higher cycle capacity retention rate than the battery in Comparative Example 1 in which the negative electrode active material is a silicon-carbon composite material with a honeycomb pore structure and the electrolyte does not contain the compound shown in Formula I or Formula II
  • the batteries in Comparative Examples 2-6 in which the negative electrode active material is a silicon-carbon composite material with a honeycomb pore structure and the electrolyte contains the compound shown in Formula I or Formula II.
  • the negative electrode is a silicon-carbon composite material with a honeycomb pore structure. Silicon particles are not easily deposited inside the honeycomb pore structure. Therefore, the mass content of silicon-based particles in the silicon-carbon composite material with a honeycomb pore structure is low, only 7%, and the silicon element is concentrated on the surface of the composite material. The carbon matrix can hardly limit the expansion of the silicon-based particles, and the battery's cycle performance is poor.

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Abstract

本申请提供一种二次电池。该二次电池包括：负极极片和电解液，负极极片包括具有三维网络交联孔结构的硅碳复合材料；电解液包含第一组分，第一组分包含式I、式II所示化合物中的至少一种。通过硅碳复合材料的三维网络交联孔结构与电解液中第一组分的配合，抑制了活性材料在充放电过程中的体积效应，改善了电池的首次库仑效率和循环稳定性。

Description

二次电池及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种二次电池及用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
随着市场对电池能量要求的逐步提高，采用高容量电极材料成为本领域的共识。然而诸多具有高理论容量的电极材料难以发挥其容量水平，如何通过电池各组分的相互配合提高电池的容量发挥，是本领域亟需解决的技术问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于提供一种二次电池。通过电解液与负极材料的匹配，提高电池的首次库仑效率和循环容量保持率，从而优化电池的容量发挥和循环性能。
本申请的第一方面提供了一种二次电池，其特征在于，包括负极极片和电解液；所述负极极片包括具有三维网络交联孔结构的硅碳复合材料；所述电解液包含第一组分，所述第一组分包含式I、式II所示化合物中的至少一种，
其中，是指M与O可以任选为单键或双键连接，M与O双键连接的时候，O与R4或R3之间无化学键；是指M1与O可以任选为单键或双键连接，M1与O双键连接的时候，O与R7之间无化学键；R1、R2、R3、R4、R5、R6、R7各自独立地选自氟、氟取代的或未取代的C1～C10烃基，芳基、羰基、羧基、酯基、氰基、硅烷基或醚基，M、M1各自独立地包含P、S、Si或B。
具有三维网络交联孔结构的硅碳复合材料具有稳定的多孔骨架、良好的机械强度，能够在负载高的硅含量的同时有效减少硅在充放电前后的体积变化，提高电池的循环性能。同时，电解液中第一组分的M元素可以和硅碳复合材料上的活性基团，如羟基、羧基、氨基结合，起到稳定活性基团的作用，减少其对活性锂的消耗，提高电池的首次库伦效果，改善电池的容量发挥水平。对于硅碳复合材料上活性基团的稳定也能进一步减少电池在循环过程中容量的衰减，提高电池的循环性能。再者，第一组分添加剂能够在硅碳复合材料表面的固态电解质膜(SEI)中生成包含M元素的无机物，如磷酸盐、硫酸盐等能够进一步提高SEI膜的强度，减少其随硅负极膨胀带来的破裂，提高电池循环性能。
在任意实施方式中，所述硅碳复合材料的比表面积为SSA m2/g，
基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，
EL：SSA为0.0001～0.03，可选为0.0004～0.01。
硅碳复合材料的比表面积越大，其表面官能团含量越高。当第一组分在电解液中的质量占比与硅碳复合材料的比表面积SSA之间的比值EL：SSA满足上述范围时，第一组分可以对硅碳复合材料上的活性基团起到有效地“钝化”作用，提高电池的容量发挥和循环性能。
在任意实施方式中，
基于所述电解液的总质量计，所述第一组分的质量占比为EL  g/g，在所述硅碳复合材料的外周区域中，所述硅碳复合材料中硅元素相对于所述硅碳复合材料总质量的质量百分含量为B1，其中，所述硅碳复合材料的外周区域为从所述硅碳复合材料的外表面向所述硅碳复合材料内部延伸距离在r/2以内的区域，r表示所述硅碳复合材料的短径，
EL：B1为0.001～0.1，可选为0.005～0.06。
硅碳复合材料外周区域的硅元素相比于内部的硅元素在制备过程中更容易残留活性基团，且其不容易受到碳骨架的束缚，体积膨胀更为显著。当第一组分在电解液中的质量占比与硅碳复合材料中硅元素相对于硅碳复合材料总质量的质量百分含量B1之间的比值满足上述范围时，有利于通过第一组分“钝化”硅元素上的活性基团，进一步提高电池的首次库伦效率和循环容量保持率。
在任意实施方式中，所述硅碳复合材料中孔径大于100nm的孔的总孔容积为V1g/cm3，基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，EL：V1为1～30，可优选为2～15。
第一组分在电解液中的质量占比EL与硅碳复合材料中孔径大于100nm的孔的总孔容积V1之间的比值EL：V1满足上述范围时，第一组分容易进入硅碳复合材料的孔结构中，与其形成相互配合进一步提高电池的容量发挥水平和循环容量保持率。
在任意实施方式中，在所述硅碳复合材料的外周区域中，所述硅碳复合材料的碳元素相对于所述硅碳复合材料总质量的质量百分含量A1与所述硅碳复合材料的硅元素相对于所述硅碳复合材料总质量的质量百分含量B1满足0.8≤B1/A1≤2.5，可选地，1≤B1/A1≤1.5。
在所述硅碳复合材料的外周区域中，所述硅碳复合材料的碳元素相对于所述硅碳复合材料总质量的质量百分含量A1与所述硅碳复合材料的硅元素相对于所述硅碳复合材料总质量的质量百分含量B1满足上述范围时，硅碳复合材料的孔结构中硅的质量相对较高，能够显著提高负极活性材料的容量，并且金属离子嵌入的电压较低，有利于金属离子的嵌入，从而提高二次电池的循环性能。同时，三 维网络交联孔结构可以抑制循环过程中硅的体积膨胀，提高负极活性材料结构稳定性，从而提高电池的循环性能。
在任意实施方式中，所述硅碳复合材料的碳元素相对于所述硅碳复合材料总质量的质量百分含量A沿从所述硅碳复合材料的几何中心向所述硅碳复合材料的外表面的方向具有减小趋势，所述硅碳复合材料的硅元素相对于所述硅碳复合材料总质量的质量百分含量B沿从所述硅碳复合材料的几何中心向所述硅碳复合材料的外表面的方向具有增大趋势。
由于硅碳复合材料可能为不规则形状的例子，硅碳复合材料的几何中心可以等同于与其相切的长方体的几何中心。由硅碳复合材料的几何中心至硅碳复合材料的外表面的方向上，碳元素的质量百分含量A逐渐减小，硅元素的质量百分含量B逐渐上升，硅碳复合材料的孔结构中硅的含量逐渐上升，硅的含量相对较高，可以显著提高负极活性材料的容量。且硅元素含量从外表面向中心不断增多使得硅基颗粒表面活性官能团不断减少，碳基颗粒对硅元素膨胀的抑制作用愈发显著，从而进一步提高电池的容量发挥和循环性能。
在任意实施方式中，所述硅碳复合材料的比表面积SSA满足：2m2/g≤SSA≤10m2/g；可选地，3m2/g≤SSA≤7m2/g。
硅碳复合材料的比表面积SSA满足上述范围时，硅碳复合材料的比表面积大，材料的动力学性能较好，有利于提高电池的首次库伦效率。
在任意实施方式中，所述硅碳复合材料包括碳基体颗粒以及硅纳米颗粒，所述碳基体颗粒包括三维网络交联的孔结构；硅纳米颗粒的至少一部分设置于所述三维网络交联的孔结构中。
本申请的碳基体颗粒具有稳定的多孔骨架结构，支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；碳基体颗粒包括三维网络交联的孔结构，可供嵌入硅基纳米颗粒的空间较多，可以用于大量储硅，有效提高硅碳复合材料中硅的负载量。在碳基体颗粒与硅基纳米颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基纳米 颗粒的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合材料的循环稳定性和储锂能力。因此，在硅碳复合材料应用于二次电池时，能够提高二次电池的循环性能和能量密度。
在任意实施方式中，所述硅纳米颗粒包括硅氧化合物、预锂硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或多种，可选为非晶硅。
在任意实施方式中，所述碳基体包括石墨、软碳和硬碳中的一种或多种。
在任意实施方式中，所述硅纳米颗粒在所述硅碳复合材料中的质量比大于等于40％，可选为40～60％。
本申请二次电池采用的负极材料通过采用包括具有三维网络交联孔结构的碳基材料实现了硅纳米颗粒在负极材料中高的负载量，使得硅碳复合材料具有高的容量，能够进一步提高电池的能量密度。
在任意实施方式中，所述硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3与所述硅碳复合材料在20000N的作用力下经过20次粉压后测试的压实密度P21g/cm3的比值满足：1.00＜P21/P11≤1.20，可选地，1.02≤P21/P11≤1.10。
当P21/P11的比值满足上述范围时，硅碳复合材料在具有较高克容量的同时还具有较好的抗压性，提高了负极膜层的结构稳定性，从而使得含有该材料的二次电池在具有较高能量密度的同时兼顾较好的循环性能。
在任意实施方式中，所述硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3满足：1.10≤P11≤1.40，可选地，1.12≤P11≤1.35。
硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3满足上述范围时，负极膜层具有较高的压实密度，从而使得二次电池具有较高的能量密度。
所述式I所示的化合物选自以下化合物中的一种或多种：
磷酸三甲酯磷酸三苯酯三(三甲基硅基)磷磷酸三丁酯硫酸二乙酯双(三甲基硅基)硫酸酯硅酸乙酯四丙氧基硅烷硅酸四苯酯硅酸四烯丙酯正硅酸四乙酯
所述式II所示的化合物选自以下化合物中的一种或多种：
亚硫酸二异丙酯三(三甲基硅烷)硼酸酯硼酸三乙酯三苯基硼酸酯 硼酸三异丙酯
上述式I所示的化合物和式II所示的化合物中包括B、P、S或Si元素。B元素和Si元素通过提供空轨道能够与硅碳复合材料表面活性基团中的氧元素结合，起到“钝化”活性基团的作用，提高电池的首次库伦效率和循环性能。P元素和S元素通过提供电子能够与硅碳复合材料表面活性基团中的氢元素结合，起到“钝化”活性基团的作用，提高电池的首次库伦效率和循环性能。
在任意实施方式中，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
本申请的第二方面提供一种用电装置，包括第一方面的二次电池。
附图说明
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1二次电池；11壳体；12电极组件；13盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的粘结剂、制备方法、电极、电池及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下 说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含 列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
随着二次电池应用范围的推广，对二次电池性能例如能量密度的要求逐步提升。硅基材料克容量高，是适用于高能量密度电池的负极材料。然而，硅基材料在充放电过程中体积膨胀率大，导致电池循环性能差。而且硅基材料相比于传统的碳基材料在生产制备过程中易于引入更多的表面基团，如硅基材料在酸处理时容易在其表面引入羧基或羟基，硅基材料在碱处理时容易在其表面引入氨基，表面基团的存在容易消耗活性锂，影响电池的容量发挥。
基于此，本申请的提供了一种二次电池，该二次电池包括：负极极片和电解液，负极极片包括具有三维网络交联孔结构的硅碳复合材料；电解液包含第一组分，所述第一组分包含式I、式II所示化合物中的至少一种，
其中，是指M与O可以任选为单键或双键连接，M与O双键连接的时候，O与R4或R3之间无化学键；是指M1与O可以任选为单键或双键连接，M1与O双键连接的时候，O与R7之间无化学键；R1、R2、R3、R4、R5、R6、R7各自独立地选自氟、氟取代的或未取代的C1～C10烃基，芳基、羰基、羧基、酯基、氰基、硅烷基或醚基，M、M1各自独立地包含P、S、Si或B。
在本文中，术语“C1～C10烃基”是指具有1至10个碳原子的碳氢基团。C1～C10烃基的非限制性示例可以包括甲基(CH3-)、乙基 (C2H5-)、异丙基((CH3)2CH-)、乙烯基(CH2＝CH-)、丙炔基(HC≡CCH2-)、亚甲基(-CH2-)。
在本文中，“芳基”是指芳烃分子失去一个氢原子而形成的基团。芳基的非限制性示例包括苯基、萘基等。
在本文中，“羰基”是指
在本文中，“羧基”是指
在本文中，“酯基”是指其中，R为C1-C3烃基。
在本文中，“氰基”是指-C≡N。
在本文中，术语“硅烷基”是指-Si(R1)(R2)(R3)基团，其中，R1、R2、R3各自独立地选自氢、取代或未取代的C1-C3烷基。作为示例，硅烷基包括但不限于-SiH3，-Si(CH3)3。
在本文中，“醚基”是指-R-O-R'-，其中，R和R'为C1-C3烃基。
在本文中，三维网络交联的孔结构通常是指在硅碳复合材料中，尤其是碳基体颗粒形成的孔结构中，存在两个或者多个孔相互联通或交错且相互共用孔容积的结构。
硅碳复合材料的孔结构可以采用本领域已知的设备和方法进行测试。例如，可以通过使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。作为示例，可以按照如下步骤操作：首先将包含所述硅碳复合材料的负极极片裁成一定尺寸的待测样品(例如6mm×6mm)，用两片导电导热的薄片(如铜箔)将待测样品夹住，将待测样品与薄片之间用胶(如双面胶)粘住固定，用一定质量(如400g左右)平整铁块压一定时间(如1h)，使待测样品与铜箔间缝隙越小越好，然后用剪刀将边缘剪齐，粘在具有导电胶的样品台上，样品略突出样品台边缘即可。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源并抽真空(例如10Pa-4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光，抛光结束后，使用扫描电子显微镜(例如ZEISS Sigma 300)得到待测样品的离子抛光断面形貌(CP)图片。
具有三维网络交联孔结构的硅碳复合材料具有稳定的多孔骨架、良好的机械强度，能够在负载高的硅含量的同时有效减少硅在充放电前后的体积变化，提高电池的循环性能。同时，电解液中第一组分的M元素可以和硅碳复合材料上的活性基团，如羟基、羧基、氨基结合，起到稳定活性基团的作用，减少其对活性锂的消耗，提高电池的首次库伦效果，改善电池的容量发挥水平。对于硅碳复合材料上活性基团的稳定也能进一步减少电池在循环过程中容量的衰减，提高电池的循环性能。再者，第一组分添加剂能够在硅碳复合材料表面的固态电解质膜(SEI)中生成包含M元素的无机物，如磷酸盐、硫酸盐等能够进一步提高SEI膜的强度，减少其随硅负极膨胀带来的破裂，提高电池循环性能。
在一些实施方式中，硅碳复合材料的比表面积为SSA m2/g，基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，EL：SSA为0.0001～0.03，可选为0.0004～0.01。
在一些实施方式中，硅碳复合材料的比表面积为SSA m2/g，第一组分在所述电解液中的质量占比为EL g/g，EL：SSA可选为0.0001、0.0002、0.0003、0.0004、0.0005、0.0006、0.0007、0.0008、0.0009、0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.009、0.01、0.02或0.03g/m2。
在本文中，比表面积SSA为本领域公知的含义，通常表面积以m2/g的单位表示，可采用本领域已知的方法和仪器测试。例如可参照GB/T 19587-2017，采用惰性气体(例如氮气)吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪进行。
硅碳复合材料的比表面积越大，其表面官能团含量越高。当第一组分在电解液中的质量占比与硅碳复合材料的比表面积SSA之间的比值EL：SSA满足上述范围时，第一组分可以对硅碳复合材料上的活性基团起到有效地“钝化”作用，提高电池的容量发挥和循环性能。
在一些实施方式中，第一组分在所述电解液中的质量占比为EL g/g。在硅碳复合材料的外周区域中，硅碳复合材料中硅元素相对于硅碳复合材料总质量的质量百分含量为B1，其中，硅碳复合材料的外周区域为从硅碳复合材料的外表面向硅碳复合材料内部延伸距离在r/2以内的区域，r表示硅碳复合材料的短径，EL：B1为0.001～0.1，可选为0.005～0.06。
可以采用三轴径表征法表征硅碳复合材料的粒子径，具体表征方法如下：在硅碳复合材料的平面投影图上测定长径l与短径r，在投影平面的垂直方向测定硅碳复合材料的厚度h；也可以理解为将硅碳复合材料放置于与其相切的长方体中，长方体的长边为l，短边为r，厚度为h，以此来反映硅碳复合材料的实际尺寸。
硅元素含量可以通过发射光谱测试(Inductively coupled plasma，ICP)测定，具体如下：取硅碳复合材料作为样品，用王水和氢氟酸HF对样品进行消解，取15min消解的溶液和完全消解的溶液进行ICP测试，45min消解的溶液中硅含量为“硅碳复合材料的外周区域”硅含量。
在一些实施方式中，第一组分在电解液中的质量占比与硅碳复合材料中硅元素相对于硅碳复合材料总质量的质量百分含量B1之间的比值EL：B1可选为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.009、0.01、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.09或0.1。
硅碳复合材料外周区域的硅元素相比于内部的硅元素在制备过程中更容易残留活性基团，且其不容易受到碳骨架的束缚，体积膨胀更为显著。当第一组分在电解液中的质量占比与硅碳复合材料中硅元素相对于硅碳复合材料总质量的质量百分含量B1之间的比值满足上述范围时，有利于通过第一组分“钝化”硅元素上的活性基团，进一步提高电池的首次库伦效率和循环容量保持率。
在一些实施方式中，硅碳复合材料中孔径大于100nm的孔的总孔容积为V1cm3/g，第一组分在电解液中的质量占比EL与硅碳复合材料中孔径大于100nm的孔的总孔容积V1之间的比值EL：V1为 1～30，可选为2～15。
不同大小孔径的孔容积测试方法可以参考GB/T 19587-2004，采用介孔孔径分布测试BJH(Barret joyner Halenda)，在微-介孔模型下采用气体吸脱附方法测试并选取吸附支数据，测定并统计孔径大于100nm的孔的孔容积总和V1。
在一些实施方式中，硅碳复合材料中孔径大于100nm的孔的总孔容积为V1cm3/g，第一组分在电解液中的质量占比EL与硅碳复合材料中孔径大于100nm的孔的总孔容积V1之间的比值EL：V1可优选为1、2、3、4、5、6、7、8、9、10、11、12、13、14、15、16、17、18、19、20、21、22、23、24、25、26、27、28、29或30。
第一组分在电解液中的质量占比EL与硅碳复合材料中孔径大于100nm的孔的总孔容积V1之间的比值EL：V1满足上述范围时，第一组分容易进入硅碳复合材料的孔结构中，与其形成相互配合进一步提高电池的容量发挥水平和循环容量保持率。
在一些实施方式中，硅碳复合材料的外周区域中，硅碳复合材料的碳元素相对于硅碳复合材料总质量的质量百分含量A1与硅碳复合材料的硅元素相对于硅碳复合材料总质量的质量百分含量B1满足0.8≤B1/A1≤2.5，可选地，1≤B1/A1≤1.5。
碳元素含量可以通过红外吸收法碳-硫含量分析，依据GB/T20123-2006测试标准测试，具体如下：取硅碳复合材料作为样品，测试20min时的碳含量为“硅碳复合材料的外周区域”碳含量。
在硅碳复合材料的外周区域中，硅碳复合材料的碳元素相对于硅碳复合材料总质量的质量百分含量A1与硅碳复合材料的硅元素相对于硅碳复合材料总质量的质量百分含量B1满足上述范围时，硅碳复合材料的孔结构中硅的质量相对较高，能够显著提高负极活性材料的容量，并且金属离子嵌入的电压较低，有利于金属离子的嵌入，从而提高二次电池的循环性能。同时，三维网络交联孔结构可以抑制循环过程中硅的体积膨胀，提高负极活性材料结构稳定性，进一步提高电池的循环性能。
在一些实施方式中，硅碳复合材料的碳元素相对于硅碳复合材 料总质量的质量百分含量A沿从硅碳复合材料的几何中心向硅碳复合材料的外表面的方向具有减小趋势，硅碳复合材料的硅元素相对于硅碳复合材料总质量的质量百分含量B沿从硅碳复合材料的几何中心向硅碳复合材料的外表面的方向具有增大趋势。
由于硅碳复合材料可能为不规则形状的例子，硅碳复合材料的几何中心可以等同于与其相切的长方体的几何中心。由硅碳复合材料的几何中心至硅碳复合材料的外表面的方向上，碳元素的质量百分含量A逐渐减小，硅元素的质量百分含量B逐渐上升，硅碳复合材料的孔结构中硅的含量逐渐上升，硅的含量相对较高，可以显著提高负极活性材料的容量。且硅元素含量从外表面向中心不断增多使得硅基颗粒表面活性官能团不断减少，碳基颗粒对硅元素膨胀的抑制作用愈发显著，从而进一步提高电池的容量发挥和循环性能。
在一些实施方式中，硅碳复合材料的比表面积SSA满足：2m2/g≤SSA≤10m2/g；可选地，3m2/g≤SSA≤7m2/g。
在一些实施方式中，硅碳复合材料的比表面积SSA可选为2m2/g、3m2/g、4m2/g、5m2/g、6m2/g、7m2/g、8m2/g、9m2/g或10m2/g，或者是上述任意两个数值组成的范围。
硅碳复合材料的比表面积SSA满足上述范围时，硅碳复合材料的比表面积大，材料的动力学性能较好，有利于提高电池的首次库伦效率。
在一些实施方式中，硅碳复合材料包括：碳基体颗粒以及硅纳米颗粒，碳基体颗粒包括三维网络交联的孔结构，硅纳米颗粒的至少一部分设置于三维网络交联的孔结构中。
本申请的碳基体颗粒具有稳定的多孔骨架结构，支撑能力较强，表现为应力能力较高，且具有优异的机械性能和导电性；碳基体颗粒包括三维网络交联的孔结构，可供嵌入硅基纳米颗粒的空间较多，可以用于大量储硅，有效提高硅碳复合材料中硅的负载量。在碳基体颗粒与硅基纳米颗粒复合后，可以提高硅碳复合材料的导电性，同时缓解硅在脱嵌锂过程中的体积效应，且能够充分承受硅基纳米颗粒的应力变化，保证硅碳复合材料的结构稳定性，提高硅碳复合 材料的循环稳定性和储锂能力。因此，在硅碳复合材料应用于二次电池时，能够提高二次电池的循环性能和能量密度。
在一些实施方式中，硅纳米颗粒包括硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或多种，可选为非晶硅。
在一些实施方式中，碳基体包括石墨、软碳和硬碳中的一种或多种。
在一些实施方式中，硅纳米颗粒在硅碳复合材料中的质量比大于等于40％，可选为40～60％。
在一些实施方式中，硅纳米颗粒在硅碳复合材料中的质量比可选为40％、45％、50％、55％或60％。
硅纳米颗粒在硅碳复合材料中的质量可以采用本领域已知的方法和设备测试，例如可参考EPA 6010D-2014标准进行测定；具体地，可以采用ICP-OES(元素分析-电感耦合等离子体发射光谱法)测试，先将待测固体用强酸溶解为液体，随后通过雾化的方式将液体引入ICP光源，进一步待测气态原子在强磁场中发生电离和激发后，由激发态恢复到基态；在上述过程中释放能量并被记录为不同的特征谱线，进行痕量元素定量分析。
本申请二次电池采用的负极材料通过采用包括具有三维网络交联孔结构的碳基材料实现了硅纳米颗粒在负极材料中高的负载量，使得硅碳复合材料具有高的容量，能够进一步提高电池的能量密度。
在一些实施方式中，硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3与硅碳复合材料在20000N的作用力下经过20次粉压后测试的压实密度P21g/cm3的比值满足：1.00＜P21/P11≤1.20，可选地，1.02≤P21/P11≤1.10。
当P21/P11的比值满足上述范围时，硅碳复合材料在具有较高克容量的同时还具有较好的抗压性，提高了负极膜层的结构稳定性，从而使得含有该材料的二次电池在具有较高能量密度的同时兼顾较好的循环性能。
在一些实施方式中，硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3满足：1.10≤P11≤1.40，可选 地，1.12≤P11≤1.35。
硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3满足上述范围时，负极膜层具有较高的压实密度，从而使得二次电池具有较高的能量密度。
在一些实施方式中，式I所示的化合物选自以下化合物中的一种或多种：
磷酸三甲酯磷酸三苯酯三(三甲基硅基)磷磷酸三丁酯硫酸二乙酯双(三甲基硅基)硫酸酯硅酸乙酯四丙氧基硅烷硅酸四苯酯硅酸四烯丙酯正硅酸四乙酯
式II所示的化合物选自以下化合物中的一种或多种：
亚硫酸二异丙酯三(三甲基硅烷)硼酸酯 硼酸三乙酯三苯基硼酸酯硼酸三异丙酯
上述式I所示的化合物和式II所示的化合物中包括B、P、S或Si元素。B元素和Si元素通过提供空轨道能够与硅碳复合材料表面活性基团中的氧元素结合，起到“钝化”活性基团的作用，提高电池的首次库伦效率和循环性能。P元素和S元素通过提供电子能够与硅碳复合材料表面活性基团中的氢元素结合，起到“钝化”活性基团的作用，提高电池的首次库伦效率和循环性能。
在一些实施方式中，二次电池包括负极极片，负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至 少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
在一些实施方式中，二次电池包括正极极片，正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化 物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物(如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极活性材料为富镍材料，镍元素在正极活性材料过渡金属中的摩尔比例高于85％。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
本申请的一个实施方式中，提供一种用电装置，包括任意实施方式的二次电池。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池1。
在一些实施方式中，参照图2，外包装可包括壳体11和盖板13。其中，壳体11可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体11具有与容纳腔连通的开口，盖板13能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件12。电极组件12封装于所述容纳腔内。电解液浸润于电极组件12中。二次电池1所含电极组件12的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
用电装置包括本申请提供的二次电池。二次电池可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
图3是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。 该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、二次电池
实施例1
(1)、硅碳复合材料的制备
提供包含硅前驱体的气体至具有三维网络交联孔结构的碳基体颗粒；通过化学气相沉积，由所述硅前驱体生成附着于所述碳基体颗粒上的硅纳米颗粒，得到硅碳复合材料。硅前驱体为硅烷，碳基体为硬碳。
(2)、负极极片的制备
将负极活性材料(硅碳复合材料)、导电炭黑、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶乳液(SBR)按96.5：1.0：1.0：1.5重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体上，经烘干等工序后，得到负极极片。
(3)、正极极片的制备
采用厚度为8μm的铝箔作为正极集流体。将正极活性材料LiNi0.8Co0.1Mn0.1O2(NCM811)，导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为93:2:5溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，再经过烘干、冷压、分切，得到正极极片。
(4)、电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF6溶解于混合后的有机溶剂中，再加入1wt％的三(三甲基硅烷)硼酸酯作为添加剂，配制成锂盐浓度为1mol/L的电解液。
(5)、隔离膜
以聚丙烯膜作为隔离膜。
(6)、电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的锂离子电池产品。
实施例2-5
实施例2-5的电池的制备方法与实施例2相似，但是调整了第一组分的种类，具体参数如表1所示。
实施例6-9
实施例6-9的电池的制备方法与实施例2相似，但是调整了第一组分的含量，具体参数如表1所示。
实施例10-13
实施例10-13的电池的制备方法与实施例2相似，但是调整了硅碳复合材料中硅基颗粒的沉积位置，以调整EL：B1的比值，具体参数如表1所示。
实施例14-17
实施例14-17的电池的制备方法与实施例2相似，但是调整了硅碳复合材料中大小孔的比例，以调整EL：V1的比值。
对比例1
对比例1的电池的制备方法与实施例1相似，但是不在电解液中加入第一组分。
对比例2
对比例2的电池的制备方法与实施例1相似，但是对比例2的碳基体颗粒的孔结构为蜂窝状孔结构。
对比例3
对比例3的电池的制备方法与实施例2相似，但是对比例3的碳 基体颗粒的孔结构为蜂窝状孔结构。
对比例4
对比例4的电池的制备方法与实施例3相似，但是对比例4的碳基体颗粒的孔结构为蜂窝状孔结构。
对比例5
对比例5的电池的制备方法与实施例4相似，但是对比例5的碳基体颗粒的孔结构为蜂窝状孔结构。
对比例6
对比例6的电池的制备方法与实施例5相似，但是对比例6的碳基体颗粒的孔结构为蜂窝状孔结构。
二、测试方法
1、硅碳复合材料
1)硅碳复合材料的结构表征
硅碳复合材料的孔结构可以采用本领域已知的设备和方法进行测试。例如，可以通过使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。作为示例，可以按照如下步骤操作：首先将包含所述硅碳复合材料的负极极片裁成一定尺寸的待测样品(例如6mm×6mm)，用两片导电导热的薄片(如铜箔)将待测样品夹住，将待测样品与薄片之间用胶(如双面胶)粘住固定，用一定质量(如400g左右)平整铁块压一定时间(如1h)，使待测样品与铜箔间缝隙越小越好，然后用剪刀将边缘剪齐，粘在具有导电胶的样品台上，样品略突出样品台边缘即可。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源并抽真空(例如10Pa-4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光，抛光结束后，使用扫描电子显微镜(例如ZEISS Sigma 300)得到待测样品的离子抛光断面形貌(CP)图片。
2)硅碳复合材料的比表面积SSA
依据GB/T19587-2017测试标准采用气体吸附法测试比表面积，具体如下：将电池拆解，取负极刮粉，高温烧蚀去除粘结剂后，取 粉末材料作为硅碳复合材料样品，样品管浸没在-196℃液氮中，在0.05-0.30相对压力下测定不同压力下氮气在固体表面的吸附量，基于BET多层吸附理论及其公式求得试样单分子层吸附量，从而计算出负极活性材料的比表面积。
BET的计算公式如下：
式中，na—被吸附气体的量，单位mol/g；p/p0—相对压力；nm—单分子层吸附量；C表示修订参数，其用于限制吸附剂表面上的吸附层的数量。
3)硅碳复合材料的孔径
气体吸附法测试孔径，依据GB/T19587-2017&GB/T21650.2-2008测试标准测试，具体如下：取硅碳复合材料作为样品，将样品管浸没在-196℃液氮中，氮气在0-1的相对压力下吸附在待测材料上，基于各级孔径的体积与相应分压下的关系图来表征多孔材料的孔径分布。
4)粉体压实密度
参照GB/T 24533-2009，使用电子压力试验机(如UTM7305)测试：将一定质量G的待测粉末样品放于压实专用模具上(底面积S)，设置不同压力(本申请中可采用20000N或50000N)，保压20s，卸除压力，等待10s，在设备上读出该压力下粉末压5实后的厚度H，计算可得该压力下的压实密度，材料在该压力下的压实密度＝G/(H*S)。
5)硅碳复合材料中硅、碳元素分布表征
采用能谱法离子抛光断面元素分析，依据GB-T17359-2012测试标准，测试颗粒断面的元素分布。
6)硅碳复合材料中硅元素含量测试
采用发射光谱测试(Inductively coupled plasma，ICP)测定硅元素含量，具体10如下：取硅碳复合材料作为样品，用王水和氢氟酸 HF对样品进行消解，取15min消解的溶液和完全消解的溶液进行ICP测试，45min消解的溶液中硅含量为“硅碳复合材料的外周区域”硅含量，完全和1h消解的溶液中硅含量的差值为“硅碳复合材料的中心区域”硅含量。
7)硅碳复合材料中碳元素含量测试15
红外吸收法碳-硫含量分析，依据GB/T20123-2006测试标准测试，具体如下：取硅碳复合材料作为样品，测试20min时的碳含量为“硅碳复合材料的外周区域”碳含量，测试20min和测试结束时的碳含量的差值为“硅碳复合材料的外周区域”碳含量。
8)硅碳复合材料的短径r测试
依据三轴表征法测定短径r，具体如下：在硅碳复合材料的平面投影图上测定短径r。
2、电池性能
1)首次库伦效率
在25℃下，将各实施例和对比例制备得到的二次电池以0.33C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压2V。将电芯第一次的充电容量除以放电容量，即为电池首圈的库伦效率。
2)循环容量保持率
在25℃下，将各实施例和对比例制备得到的二次电池以0.5C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压2V，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，计算锂离子电池循环800次后的容量保持率。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的二次电池，并测量各项参数，结果见下表1。
表1
根据表1的结果可知，实施例1-17的电池的负极活性材料为三 维网络交联孔结构的硅碳复合材料，并且电解液包含式I或式II所示化合物，相比于对比例1中负极活性材料为蜂窝状孔结构的硅碳复合材料且电解液不包含式I或式II所示化合物的电池以及对比例2-6中负极活性材料为蜂窝状孔结构的硅碳复合材料且电解液包含式I或式II所示化合物的电池，实施例1-17的电池表现出更高的首次库伦效率，更高的循环容量保持率。
对比例中负极为蜂窝状孔结构的硅碳复合材料，硅颗粒不容易沉积在蜂窝状孔结构的内部，因此，蜂窝孔状结构的硅碳复合材料中硅基颗粒的质量含量低，仅为7％，且硅元素集中于复合材料的表面分布，碳基体难以起到限制硅基颗粒膨胀的作用，电池的循环性能差。
从实施例7、8与实施例6、9的对比可见，控制第一组分在电解液中的质量占比EL与硅碳复合材料的比表面积之间的比值EL：SSA在0.0004～0.01的范围内，有利于进一步提高电池的首次库伦效率和循环容量保持率。
从实施例10-13可见，进一步控制EL：B1在0.005～0.06范围内，电池的首次库伦效率和循环容量保持率会进一步提高。
从实施例14-17可见，进一步使得EL：V1在1～30cm3/g范围内，电池的首次库伦效率和循环容量保持率会进一步提高。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种二次电池，其特征在于，包括
    负极极片，所述负极极片包括具有三维网络交联孔结构的硅碳复合材料；和
    电解液，所述电解液包含第一组分，所述第一组分包含式I、式II所示化合物中的至少一种，
    其中，是指M与O可以任选为单键或双键连接，M与O双键连接的时候，O与R4或R3之间无化学键；是指M1与O可以任选为单键或双键连接，M1与O双键连接的时候，O与R7之间无化学键；R1、R2、R3、R4、R5、R6、R7各自独立地包含氟、氟取代的或未取代的C1～C10烃基，芳基、羰基、羧基、酯基、氰基、硅烷基或醚基，M、M1各自独立地包含P、S、Si或B。
  2. 根据权利要求1所述的二次电池，其特征在于，
    所述硅碳复合材料的比表面积为SSA m2/g，
    基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，
    EL：SSA为0.001～0.02，可选为0.004～0.01。
  3. 根据权利要求1或2所述的二次电池，其特征在于，
    基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，
    在所述硅碳复合材料的外周区域中，所述硅碳复合材料中硅元素相对于所述硅碳复合材料总质量的质量百分含量为B1，其中，所 述硅碳复合材料的外周区域为从所述硅碳复合材料的外表面向所述硅碳复合材料内部延伸距离在r/2以内的区域，r表示所述硅碳复合材料的短径，
    EL：B1为0.001～0.1，可选为0.005～0.06。
  4. 根据权利要求1至3中任一项所述的二次电池，其特征在于，所述硅碳复合材料中孔径大于100nm的孔的总孔容积为V1cm3/g，基于所述电解液的总质量计，所述第一组分的质量占比为EL g/g，
    EL：V1为1～30，可优选为2～15。
  5. 根据权利要求1至4中任一项所述的二次电池，其特征在于，所述式I所示的化合物选自以下化合物中的一种或多种：
    磷酸三甲酯、磷酸三苯酯、三(三甲基硅基)磷、磷酸三丁酯、硫酸二乙酯、双(三甲基硅基)硫酸酯、硅酸乙酯、四丙氧基硅烷、硅酸四苯酯、硅酸四烯丙酯、正硅酸四乙酯；
    所述式II所示的化合物选自以下化合物中的一种或多种：
    亚硫酸二异丙酯、三(三甲基硅烷)硼酸酯、硼酸三乙酯、三苯基硼酸酯、硼酸三异丙酯。
  6. 根据权利要求3至5中任一项所述的二次电池，其特征在于，在所述硅碳复合材料的外周区域中，所述硅碳复合材料的碳元素相对于所述硅碳复合材料总质量的质量百分含量A1与所述硅碳复合材料的硅元素相对于所述硅碳复合材料总质量的质量百分含量B1满足0.8≤B1/A1≤2.5，可选地，1≤B1/A1≤1.5。
  7. 根据权利要求1至6中任一项所述的二次电池，其特征在于，所述硅碳复合材料的碳元素相对于所述硅碳复合材料总质量的质量百分含量A沿从所述硅碳复合材料的几何中心向所述硅碳复合材料的外表面的方向具有减小趋势，所述硅碳复合材料的硅元素相对于所述硅碳复合材料总质量的质量百分含量B沿从所述硅碳复合材料 的几何中心向所述硅碳复合材料的外表面的方向具有增大趋势。
  8. 根据权利要求1至7中任一项所述的二次电池，其特征在于，
    所述硅碳复合材料的比表面积SSA满足：2m2/g≤SSA≤10m2/g；可选地，3m2/g≤SSA≤7m2/g。
  9. 根据权利要求1至8中任一项所述的二次电池，其特征在于，所述硅碳复合材料包括：碳基体颗粒，所述碳基体颗粒包括三维网络交联的孔结构；以及硅纳米颗粒，其至少一部分设置于所述三维网络交联的孔结构中。
  10. 根据权利要求9所述的二次电池，其特征在于，所述硅纳米颗粒包括硅氧化合物、非晶硅、晶体硅和硅碳复合物中的一种或多种，可选为非晶硅。
  11. 根据权利要求9或10所述的二次电池，其特征在于，所述碳基体包括石墨、软碳和硬碳中的一种或多种。
  12. 根据权利要求9至11中任一项所述的二次电池，其特征在于，所述硅纳米颗粒在所述硅碳复合材料中的质量比大于等于40％，可选为40～60％。
  13. 根据权利要求1至12中任一项所述的二次电池，其特征在于，所述硅碳复合材料在20000N的作用力下经过1次粉压后测试的粉体压实密度P11g/cm3与所述硅碳复合材料在20000N的作用力下经过20次粉压后测试的压实密度记P21g/cm3的比值满足：1.00＜P21/P11≤1.20，可选地，1.02≤P21/P11≤1.10。
  14. 根据权利要求1至13中任一项所述的二次电池，其特征在于，所述硅碳复合材料在20000N的作用力下经过1次粉压后测试的 粉体压实密度P11g/cm3满足：1.10≤P11≤1.40，可选地，1.12≤P11≤1.35。
  15. 根据权利要求1至14中任一项所述的二次电池，其特征在于，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
  16. 一种用电装置，其特征在于，包括权利要求1至15中任一项所述的二次电池。
PCT/CN2023/085554 2023-03-31 2023-03-31 二次电池及用电装置 Ceased WO2024197837A1 (zh)

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