WO2022205031A1 - Silicon-oxygen-carbon composite material, and preparation method therefor and application thereof - Google Patents

Abstract

Provided in the present invention are a silicon-oxygen-carbon composite material, and a preparation method therefor and application thereof. The silicon-oxygen-carbon composite material includes a matrix material, which includes a three-dimensional framework material and a SiOC layer on the surface of the three-dimensional framework material, the SiOC layer containing Si, O and C; and a carbon layer on the surface of the matrix material. The silicon-oxygen-carbon composite material of the present invention has the characteristics such as high capacity, good electrical conductivity and ionic conductivity, and can effectively improve the cycle performance and other qualities of an electrochemical device.

Description

Silicon oxycarbon composite material and its preparation method and application technical field

The invention relates to the field of batteries, in particular to a silicon oxycarbon composite material, a preparation method and application thereof, and more particularly, to a negative electrode sheet, an electrochemical device and an electronic device using the silicon oxycarbon composite material.

Background technique

Silicon-containing materials have the advantages of higher capacity and lower voltage platform, and have good application prospects in electrochemical devices such as batteries. SiOC material is a material obtained by cracking silicon-containing organic compounds. It is mainly composed of Si-OC framework and free carbon (C _free ). The disordered Si-OC network structure has rigidity, which makes SiOC material excellent in resisting external force damage. Compared with other silicon-containing materials, it has the advantages of small volume expansion and other advantages, and has gradually attracted widespread attention. However, as a ceramic material, SiOC material has low electrical conductivity and dense structure, which makes its electrical conductivity and ion transport ability poor, limiting its application.

There are two main methods to improve the conductivity of SiOC materials: (1) Increase the carbon content in the SiOC material (that is, to prepare a carbon-rich SiOC material) to improve its conductivity. When the amount of C _free in the SiOC material is small, the The _free is separated by the Si-OC tetrahedral monomer, and it is difficult to form a continuous conductive network. Increasing the carbon content can improve the conductivity of the material to a certain extent. However, when the C _free content is high, the active sites of the SiOC material contribute to the capacity. The sharp decline is not conducive to the improvement of capacity; (2) the use of SiOC materials with high-conductivity carbon-based materials is still limited in improving the conductivity of the overall material. For example, two-dimensional nano-carbon and SiOC are generally used. When the materials are mixed and used, the two-dimensional nano-carbon is easy to agglomerate, resulting in its uneven and discontinuous distribution in the SiOC material matrix, and the two-dimensional structure of the nano-carbon material only has good electrical conductivity along the axial or plane direction, while Conductivity is almost zero in the vertical direction.

In addition, the ion transport ability of SiOC material is also an important factor affecting its practical application, and in the prior art, there are few effective means to improve the ion transport ability of SiOC material. Therefore, how to improve the performance of SiOC materials such as ion transport ability, conductivity and capacity, and then improve the quality of electrochemical devices such as cycle performance, is still an important issue faced by those skilled in the art.

SUMMARY OF THE INVENTION

The present invention provides a silicon oxygen carbon composite material, a preparation method and application thereof. The silicon oxygen carbon composite material has the characteristics of high capacity, high electrical conductivity and high ion transport ability, and can effectively overcome the defects of the prior art.

In one aspect of the present invention, a silicon oxycarbon composite material is provided, comprising: a matrix material, the matrix material includes a three-dimensional framework material and a SiOC layer on the surface of the three-dimensional framework material, the SiOC layer includes Si, O, and C elements; and a matrix material carbon layer on the surface.

In some embodiments, the three-dimensional carbon framework material includes 2 to 30 layers of graphene, and the three-dimensional carbon framework material has a thickness of 1 nm to 1 μm; and/or, the three-dimensional carbon framework material may have a length of 0.5 μm to 10 μm; and/or Or, the three-dimensional carbon skeleton material may specifically be a sheet; and/or, the Raman spectrum of the three-dimensional carbon skeleton material shows that the ratio of the peak height I ₁₃₅₀ of 1350cm ^-1 and the peak height I ₁₅₈₀ of 1580cm ^-1 satisfies 0.7≤I ₁₃₅₀ /I ₁₅₈₀ ≤1.8.

In some embodiments, the thickness of the SiOC layer is 10 nm to 500 nm; and/or, in the SiOC layer, the atomic ratio of silicon element to oxygen element is 1:0.2 to 1:1.5; and/or, m _Si /m _c is satisfied is 1: 0.05 to 1: 1.2, m _Si is the mass of silicon element in the silicon-oxygen-carbon composite material, m _c is the mass of carbon element in the silicon-oxygen-carbon composite material; and/or, m _O1 /m _O2 is 1: 1 to 1:1.1, m _O1 is the mass of oxygen elements in the SiOC layer, m _O2 is the mass of oxygen elements in the silicon-oxygen-carbon composite material; and/or, the SiOC layer contains SiOC materials containing Si, O, and C elements, SiOC The particle size Dv50 ₁ of the material and the particle size Dv50 ₂ of the three-dimensional carbon framework material satisfy: Dv50 ₁ /Dv50 ₂ is 1:5 to 1:50, and Dv50 ₁ indicates that in the particle size distribution based on the volume, the SiOC material particles are from the small particle size side. Dv50 ₂ represents the particle size of the three-dimensional carbon framework material particles starting from the small particle size side and reaching 50% of the volume accumulation in the particle size distribution based on volume.

In some embodiments, m ₂ /m ₁ is 2 to 20, m ₂ is the mass of the SiOC layer, and m ₁ is the total mass of carbon elements in the silicon oxycarbon composite material; and/or, the thickness of the carbon layer is 0.1 nm to 10 nm; and/or, the carbon layer includes a carbon material, and the Raman spectrum of the carbon material shows that the ratio of the peak height I ₁₃₅₀ at 1350 cm ⁻¹ and the peak height I ₁₅₈₀ at 1580 cm ⁻¹ satisfies 0.7≦I ₁₃₅₀ /I ₁₅₈₀ ≦ 1.8.

In some embodiments, the silicon oxycarbon composite material has at least one of micropores, mesopores or macropores; and/or, in the X-ray photoelectron spectroscopy analysis result, the binding energy peak position of Si 2p includes 101.4± At least one of 0.3eV, 102.2±0.3eV, 103.1±0.3eV or 104.40±0.3eV, and the binding energy peak position of C 1s includes 283.8±0.3eV, 284.6±0.3eV, 286.3±0.3eV or 104.40±0.3eV At least one of; and/or, in its solid NMR test results, the shifts of silicon include -5ppm, -35ppm, -75ppm, -110ppm, and the half-peak width K ppm at -5ppm satisfies 7<K<28.

Another aspect of the present invention provides a method for preparing the above silicon oxycarbon composite material, comprising: impregnating a three-dimensional carbon skeleton material with a solution containing an organosiloxane, and subjecting the obtained impregnated product to a pyrolysis treatment to obtain a three-dimensional carbon skeleton material. A SiOC layer is formed on the surface of the carbon skeleton material to obtain a matrix material; a carbon layer is formed on the surface of the matrix material by chemical vapor deposition to obtain a silicon-oxygen-carbon composite material.

In yet another aspect of the present invention, a negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material comprises the above-mentioned silicon oxycarbon composite Material. Optionally, the negative electrode active material further includes graphite. In the negative electrode active material, the mass content of the silicon oxycarbon composite material is 40% to 80%. The electrical conductivity of the negative electrode active material is 2 S/cm to 30 S/cm; and/or the resistance of the negative electrode sheet is 0.2Ω to 1Ω.

As an extension of the idea of the present invention, an electrochemical device including the above-mentioned negative electrode sheet and an electronic device including the electrochemical device are also provided.

The silicon-oxygen-carbon composite material provided by the present invention adopts the three-dimensional carbon skeleton material-design of the multi-level structure of the SiOC layer-carbon layer, uses the SiOC layer to provide active sites, and at the same time ensures ion transport, and cooperates with the three-dimensional carbon skeleton material and the carbon layer. It can take into account the improvement of the capacity, ion transport capacity, conductivity and other properties of the silicon oxycarbon composite material, which is beneficial to its function as a negative electrode active material, showing excellent characteristics such as high capacity and long cycle, making the negative electrode sheet/electrochemical device compatible. With good cycle performance, stability and safety and other qualities, it is of great significance for practical industrial application.

Description of drawings

Fig. 1 is the structural representation of silicon-oxygen-carbon composite material of the present invention;

FIG. 2 is a graph showing the change of the capacity of the battery during the cycle with the number of cycles according to an embodiment of the present invention;

FIG. 3 is a capacity fading curve diagram of a battery during cycling according to an embodiment of the present invention.

Detailed ways

In order for those skilled in the art to better understand the solution of the present invention, the present invention is further described in detail below.

As shown in FIG. 1, the silicon oxycarbon composite material of the present invention includes: a matrix material, the matrix material includes a three-dimensional framework material and a SiOC layer on the surface of the three-dimensional framework material, the SiOC layer includes Si, O, and C elements; and the surface of the matrix material carbon layer.

The three-dimensional carbon framework material, as the framework of the silicon-oxygen carbon composite material, has an important influence on the electrical conductivity and structural stability of the material. Further optimization results show that the three-dimensional carbon framework material can include 2 to 30 layers of graphene, namely The three-dimensional carbon skeleton material is a graphene skeleton, and has a three-dimensional carbon skeleton structure formed by 2 to 30 layers of graphene, and the number of layers of graphene forming the three-dimensional carbon skeleton structure is, for example, 2, 5, 8, 10, 12, 15 , 20, 22, 25, 30, or a range of any two of these values. In the present invention, the number of graphene layers in the three-dimensional carbon framework material can generally be measured by transmission electron microscopy (TEM).

Relatively speaking, if the thickness of the three-dimensional carbon skeleton material is too large, it will affect the compaction density of the silicon-oxygen carbon composite material when it is used as the negative electrode active material, thereby affecting the energy density of the negative electrode sheet, while the thickness of the three-dimensional carbon skeleton material is too small. The electrical conductivity of the silicon-oxy-carbon composite material affects its capacity. Considering these factors, in some embodiments, the thickness of the three-dimensional carbon framework material can generally be 1 nm to 1 μm, such as 1 nm, 10 nm, 50 nm, 100 nm, 300 nm, 600 nm , 800nm, 1μm, or any two of these ranges. Further, the length of the three-dimensional carbon framework material can be 0.5 μm to 10 μm, for example, a range composed of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any two thereof.

In general, the three-dimensional carbon framework material is sheet-like, with SiOC layers on the front and back sides, and a carbon layer on the surface of the SiOC layer. The surface of the three-dimensional carbon skeleton material, and the SiOC layer and the carbon layer are closely combined. Under this structural system, SiOC provides active sites to ensure the capacity of the silicon-oxy-carbon composite material. The three-dimensional carbon framework material and the carbon layer can keep the silicon-oxy-carbon composite material well. The electrical contact improves the reversibility of the electrochemical reaction, thereby improving the cycle stability of the silicon-oxycarbon composite material as the negative electrode active material, thereby improving the cyclability and other qualities of the electrochemical device.

After further research, the Raman spectrum of the three-dimensional carbon framework material shows that the ratio of the peak height I ₁₃₅₀ at 1350 cm ^-1 and the peak height I ₁₅₈₀ at 1580 cm ^-1 satisfies 0.7≤I ₁₃₅₀ /I ₁₅₈₀ ≤1.8, and I ₁₃₅₀ / I ₁₅₈₀ is, for example, a range of 0.7, 1, 1.3, 1.5, 1.8, or any two of these values.

The SiOC layer can be a nano-scale sheet layer, which can shorten the ion transmission path and improve the ion transmission capacity of the silicon oxycarbon composite material. In some preferred embodiments, the thickness of the SiOC layer is 10nm to 500nm, such as 10nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or a range of any two of them.

In addition, in the SiOC layer, the atomic ratio of silicon element to oxygen element may be 1:0.2 to 1:1.5, such as 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5 or these The range of any two of the ratios is conducive to further improving the capacity and ion transport capacity of the silicon-oxygen-carbon composite material. Within the above range, the oxygen-rich SiOC material with relatively high oxygen content can provide more active sites , which is beneficial to improve the capacity of silicon-oxy-carbon composites.

In some embodiments, m _Si /m _c is 1:0.05 to 1:1.2, m _Si is the mass of silicon element in the silicon oxycarbon composite material, m _c is the mass of carbon element in the silicon oxygen carbon composite material, m _Si /m _c is, for example, a range of 1:0.05, 1:0.1, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2 or any two of these ratios, and _mSi /m is controlled _c is within the above range, it is beneficial to take into account both the improvement of the electrical conductivity and the gram capacity of the silicon-oxy-carbon composite material. In general, the mass content of silicon element in the silicon oxycarbon composite material is 50% to 90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or A range consisting of any two of them.

In addition, it can also satisfy that m _O1 /m _O2 is 1:1 to 1:1.1, m _O1 is the mass of oxygen element in the SiOC layer, and m _O2 is the mass of oxygen element in the silicon-oxygen-carbon composite material, which is conducive to taking into account the improvement of silicon-oxy-carbon Capacity and cycle performance of composites. In general, the mass content of oxygen in the SiOC layer is 10% to 40%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any two of them.

The SiOC layer may be specifically formed of a SiOC material containing Si, O, and C elements. In some embodiments, the SiOC layer includes a SiOC material containing Si, O, and C elements. The particle size of the SiOC material is Dv50 ₁ and the three-dimensional carbon The particle size Dv50 ₂ of the framework material satisfies the Dv50 ₁ /Dv50 ₂ ratio of 1:5 to 1:50, and Dv50 ₁ represents the particle size distribution of the SiOC material particles from the small particle size side to reach 50% of the volume accumulation in the particle size distribution based on volume , Dv50 ₂ indicates that in the particle size distribution based on volume, the three-dimensional carbon framework material particles reach 50% of the particle size of the volume accumulation from the small particle size side. Relatively speaking, Dv50 ₁ /Dv50 ₂ is too large (greater than 1:5), The particle size of the SiOC material is too large, which is not conducive to the full contact between the SiOC material and the _{three -} dimensional carbon framework material, and affects the conductivity and capacity of the silicon-oxycarbon composite material. The particle size of the skeleton material is too large, which affects the compaction density of the silicon oxycarbon composite material as the negative electrode active material, which in turn affects the energy density of the negative electrode sheet. Wherein, Dv50 ₁ /Dv50 ₂ is, for example, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50 or these A range of any two of the ratios. In some embodiments, the Dv50 ₁ may be 0.1 μm to 5 μm, such as a range of 0.1 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any two thereof .

In addition, in order to further improve the capacity, electrical conductivity and ion transport capability of the silicon oxycarbon composite material, in some embodiments, m ₂ /m ₁ can also be satisfied, m ₂ is the quality of the SiOC layer, and m ₁ is The total mass of carbon elements in the silicon oxycarbon composite material, m ₂ /m ₁ , is, for example, a range of 2, 5, 8, 10, 12, 15, 18, 20 or any two of these ratios. In some embodiments, in the silicon oxycarbon composite material, the mass content of the SiOC layer is 70% to 95%, such as a range of 70%, 75%, 80%, 85%, 90% or any two thereof.

As the outer layer existing on the surface of the base material, the carbon layer has an important influence on ensuring the structural stability and electrical conductivity of the silicon-oxycarbon composite material. 10nm, such as 0.1nm, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm or the range of any two of them, and the thickness of the carbon layer is controlled within this range. The comprehensive properties of the composite material, such as capacity and electrical conductivity, are favorable.

The carbon layer is mainly formed of carbon material, that is, it mainly contains carbon element. In addition, at least one of sulfur element (S), nitrogen (N) element or other foreign elements can also be introduced into the carbon layer, The conductivity of the silicon-oxy-carbon composite material can be further improved, which is beneficial to its function.

In some embodiments, the carbon layer includes a carbon material, and the Raman spectrum of the carbon material shows that the ratio of the peak height I ₁₃₅₀ at 1350 cm ⁻¹ and the peak height I ₁₅₈₀ at 1580 cm ⁻¹ satisfies 0.7≦I ₁₃₅₀ /I ₁₅₈₀ ≦1.8. In specific implementation, a Raman light source with a shallow detection depth can be selected (to avoid detecting the SiOC layer and inner layer materials) to detect the Raman characteristics of the carbon layer on the surface of the silicon-oxygen-carbon composite material, and obtain the Raman test result.

In some embodiments, the silicon oxycarbon composite material has a porous structure, and specifically may have micropores (pore diameters less than 2 nm), mesopores (pore diameters between 2 nm and 50 nm) or macropores (pore diameters between 50 nm and 50 μm). ), especially may have a hierarchical pore structure comprising at least two of micropores, mesopores or macropores.

In addition, the silicon oxycarbon composite material with good electrical conductivity and ion transport ability can also have the following characteristics: in its X-ray photoelectron spectroscopy (XPS) analysis, the binding energy peak positions of Si 2p include 101.4±0.3 eV, 102.2± At least one of 0.3eV, 103.1±0.3eV or 104.40±0.3eV, and the binding energy peak position of C 1s includes at least one of 283.8±0.3eV, 284.6±0.3eV, 286.3±0.3eV or 104.40±0.3eV ; Further, in its solid nuclear magnetic test (sNMR) results, the shifts of silicon include -5ppm, -35ppm, -75ppm, -110ppm, and the half-peak width Kppm at -5ppm satisfies 7<K<28.

In the present invention, the preparation method of the silicon oxycarbon composite material comprises: impregnating the three-dimensional carbon skeleton material with a solution containing organosiloxane, and subjecting the obtained impregnated product to pyrolysis treatment to form a SiOC layer on the surface of the three-dimensional carbon skeleton material, A base material is obtained; a carbon layer is formed on the surface of the base material by chemical vapor deposition (CVD) to obtain a silicon-oxygen-carbon composite material.

In some embodiments, the impregnated product is also subjected to a crosslinking treatment followed by a pyrolysis treatment. In specific implementation, the three-dimensional carbon skeleton material can be completely immersed in a solution containing organosiloxane, and impregnated by a vacuum impregnation method. After the impregnation is completed, the system is placed at 20°C to 120°C for crosslinking. The crosslinking time is generally It can be about 2 hours, but is not limited to this, and then in an inert atmosphere such as argon (Ar), the temperature is raised to 800°C to 1200°C at a heating rate of 2°C/min to 10°C/min for pyrolysis treatment. The treatment time can generally be 0.5 hours (h) to 4 hours; after the pyrolysis treatment is completed, the pyrolysis product (matrix material) can be crushed and sieved to obtain the matrix material that meets the particle size requirements, and then the carbon source is used as the A carbon layer is formed on the surface of the base material by the CVD method, so as to obtain a silicon-oxy-carbon composite material. Wherein, the mass concentration of organosiloxane in the solution containing organosiloxane can be 20% to 60%, and the organosiloxane includes, for example, tetramethyl-tetravinyl-cyclotetrasiloxane and/or polymethyl Hydrogen siloxane; the carbon source used in the CVD process may include at least one of methane, ethylene or acetylene, but is not limited thereto, and suitable materials may be selected according to the elements to be introduced into the carbon layer in the specific implementation process.

The negative electrode sheet of the present invention includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material includes the above-mentioned silicon oxycarbon composite material.

In addition, the negative electrode active material may also include graphite. For example, the negative electrode active material may be a mixture of silicon-oxygen carbon composite material and graphite. Specifically, the graphite may include natural graphite, artificial graphite, and mesocarbon microspheres. at least one of. In some embodiments, the gram capacity of the negative electrode active material obtained by blending the silicon oxycarbon composite material with the negative electrode active material such as graphite is 500 mAh/g to 1800 mAh/g, such as 500 mAh/g, 650 mAh/g, 800 mAh/g g, 1000mAh/g, 1200mAh/g, 1400mAh/g, 1600mAh/g, 1800mAh/g or the range of any two of them. During the specific implementation, the negative electrode can be adjusted according to the ratio of the silicon-oxygen-carbon composite material and the graphite composite The gram capacity of the active substance.

In some embodiments, in the negative electrode active material, the mass content of the silicon oxycarbon composite material is 40% to 80%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% , 80% or any two of them, and the balance can be graphite or other negative electrode active materials. Controlling the amount of silicon-oxygen carbon composite material within this range is conducive to improving the energy density, cyclability and stability of the negative electrode sheet. performance, etc.

In general, the conductivity of the negative electrode active material can be 2S/cm to 30S/cm, such as 2S/cm, 5S/cm, 10S/cm, 15S/cm, 20S/cm, 25S/cm, 30S/cm or among them A range of any two of them. The resistance of the negative electrode sheet is generally 0.2Ω to 1Ω, such as a range of 0.2Ω, 0.4Ω, 0.6Ω, 0.8Ω, 1Ω or any two thereof.

The above-mentioned negative electrode active material layer (or mixture layer) also includes a conductive agent and a binder, wherein the mass content of the negative electrode active material can generally be 90% to 98%, the mass content of the conductive agent is 1.2% to 5%, and the viscosity The mass content of the binder is 3% to 6%. . For example, the conductive agent may include at least one of conductive carbon black (SP), acetylene black, Ketjen black, conductive graphite or graphene, and the binder may include polyacrylic acid (PAA), polyacrylate, polyacryl Imine, polyamide, polyamideimide, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose , at least one of potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose or potassium hydroxymethyl cellulose.

The negative electrode sheet of the present invention can be prepared by a coating method, but is not limited thereto. In some embodiments, the preparation process of the negative electrode sheet may include: coating the slurry containing the raw material of the negative electrode active material layer on at least one surface of the negative electrode current collector and forming the negative electrode active material layer to obtain the negative electrode sheet. In specific implementation, the negative electrode active material, conductive agent, and binder can be mixed uniformly in a solvent to form the above slurry, the slurry can be coated on the negative electrode current collector, dried/drying, rolling/cold pressing After the treatment, a negative electrode active material layer is formed to obtain a negative electrode sheet. Wherein, the solvent can be a conventional solvent in the field such as water, and the negative electrode current collector can be a conventional negative electrode current collector such as copper foil. Repeat.

The electrochemical device of the present invention includes the above-mentioned negative electrode sheet, and the electrochemical device may specifically be a battery, such as a secondary battery, specifically a lithium ion battery or the like. The electrochemical device further includes a positive electrode sheet and a separator between the negative electrode sheet and the positive electrode sheet. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector. The positive electrode active material layer It includes a positive electrode active material, a conductive agent and a binder, and the positive electrode active material includes, for example, lithium cobalt oxide (LiCoO ₂ ), lithium iron phosphate, nickel-cobalt-manganese ternary material (NCM) or nickel-cobalt-aluminum ternary material (NCA). At least one, the positive electrode current collector can be aluminum foil, etc.; the separator is used to separate the positive electrode sheet and the negative electrode sheet, and it can include polyethylene (PE) porous polymer film and the like.

The above electrochemical device further includes an electrolyte, for example, the electrolyte includes an organic solvent, a lithium salt and an additive, and the organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), carbonic acid At least one of methyl ethyl ester (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate, and lithium salts include organic lithium salts and/or inorganic lithium salts, such as lithium hexafluorophosphate (LiPF6), Lithium Tetrafluoroborate (LiBF ₄ ), Lithium Difluorophosphate (LiPO ₂ F ₂ ), Lithium Bistrifluoromethanesulfonimide LiN(CF ₃ 8O ₂ ) ₂ (LiTFSI), Lithium Bis(fluorosulfonyl)imide At least one of Li(N(SO ₂ F) ₂ ) (LiFSI), Lithium Bisoxalate Borate LiB(C ₂ O ₄ ) ₂ (LiBOB), or Lithium Difluorooxalate Borate LiBF ₂ (C ₂ O ₄ ) (LiDFOB) The additive includes at least one of crown ether compounds, boron compounds, inorganic nano oxides, carbonate compounds or amide compounds, for example, it may include 12-crown-4 ether, boron anion acceptor tri(penta) At least one of fluorophenyl)borane (TFPB), tris(pentafluorophenyl)borate, vinylene carbonate (VC) or acetamide and derivatives thereof. In some embodiments, the content of the lithium salt in the electrolyte is 0.5 mol/L to 1.5 mol/L, such as 0.7 mol/L to 1.3 mol/L or 0.9 mol/L to 1.1 mol/L.

The electrochemical device of the present invention can be prepared according to conventional methods in the art. For example, in some embodiments, the electrochemical device is a wound lithium-ion battery, and the preparation process may include: a positive electrode sheet, a separator, a negative electrode After the sheets are stacked and arranged, they are wound to form a bare cell, and then the bare cell is placed in the outer package, and then the electrolyte is injected, and then the full cell (that is, the battery) is obtained after encapsulation, formation, degassing, trimming and other processes. ). The above-mentioned processes such as winding, liquid injection, packaging, chemical formation, degassing, and trimming are all routine operations in the art, and will not be repeated here.

The electronic device of the present invention includes the above-mentioned electrochemical device, and may be the electrochemical device of any of the above-described embodiments, or may be an electrochemical device of other embodiments without departing from the spirit and scope of the present invention.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless otherwise specified, in the following examples and comparative examples, the spectral analysis and performance testing of materials are conventional methods in the art, and the relevant testing process is briefly described as follows:

(1) Scanning Electron Microscope (SEM) Characterization: Recorded by PhilipsXL-30 Field Emission Scanning Electron Microscope, and detected under the conditions of 10kV and 10mA, to determine the parameters of material particle morphology, size and uniformity (such as three-dimensional carbon framework materials length and thickness, etc.);

(2) TEM characterization: JEOL JEM-2010 transmission electron microscope was used, and the operating voltage was 200kV;

(3) Carbon content test: use a high-frequency infrared carbon-sulfur analyzer (Shanghai Dekai HCS-140) to test, so that the sample is heated and burned at a high temperature in a high-frequency furnace under oxygen-rich conditions, so that the carbon element is oxidized into carbon dioxide, so that the After the carbon dioxide gas is processed, it enters the corresponding absorption cell, absorbs the corresponding infrared radiation, and then is converted into a corresponding signal by the detector. The signal is sampled by the computer and converted into a value proportional to the carbon dioxide concentration after linear correction. Then the values of the whole analysis process are accumulated. After the analysis, the accumulated value is divided by the weight value in the computer, multiplied by the correction coefficient, and the blank is deducted, that is, the carbon content in the sample is obtained;

(4) Silicon content test: use inductively coupled plasma (ICP) method to test the silicon content in the material;

(5) Conductivity test: use a resistivity tester (Suzhou Lattice Electronics ST-2255A) to test, take 5g powder sample, use an electronic press to constant pressure to 5000kg ± 2kg, and maintain for 15-25s; place the sample in the test Between the electrodes of the instrument, the height of the sample is h (cm), the voltage at both ends is U, the current is I, and the area of the resistance R (KΩ) after the powder is pressed is S=3.14cm ² , according to the formula δ=h/(S*R) /1000 to calculate the electronic conductivity of the powder, the unit is S/m;

(6) Particle size test: add about 0.02g of powder sample to a 50ml clean beaker, add about 20ml of deionized water to it, and then add a few drops of 1% surfactant to completely disperse the powder in water. Ultrasound at 120W. Ultrasonic in the cleaning machine for 5 minutes, and use a laser particle size analyzer (MasterSizer2000) to test the particle size distribution (Dv50, Dv99, etc.);

(7) sNMR test: The ²⁹ Si sNMR spectrum was measured by a solid 400-megabyte (wide cavity) superconducting nuclear magnetic resonance spectrometer (AVANCE III 400WB), where the rotation rate of 8 kHz corresponds to ²⁹ Si;

(8) Raman test: use the LabRAM HR spectrometer from Jobin Yvon company to test, the light source is 532nm, the selected test range is 0cm ^-1 to 4000cm ^-1 ; the test sample area range is 100 μm×100 μm, and 100 I ₁₃₅₀ are counted. /I ₁₅₈₀ value, get the final I ₁₃₅₀ /I ₁₅₈₀ value;

(9) Negative electrode resistance value and resistivity test: The negative electrode film resistance is tested by the four-point probe method. The instrument used for the four-point probe method test is a precision DC voltage and current source (SB118 type), four 1.5cm long * 1cm wide * The copper plates with a thickness of 2mm are fixed on a line at equal distances, and the distance between the two copper plates in the middle is L (1-2cm). On (the pressure is 3000Kg), the maintenance time is 60s, the copper plates at both ends are connected to the DC current I, the voltage V is measured on the two copper plates in the middle, the values of I and V are read three times, and the average values Ia and Va of I and V are taken respectively, The value of Va/Ia is the membrane resistance at the test place, and the ratio of the resistance value to the thickness of the negative plate is the membrane resistivity; each negative plate is tested at 12 points, and the average value is the final negative plate resistivity result. ;

(10) Battery cycle performance test: At a test temperature of 25°C, charge the battery to 4.45V at a constant current of 0.5C, charge it to 0.025C at a constant voltage, and discharge it to 3.0V at 0.5C after standing for 5 minutes. The capacity obtained in the steps is the initial capacity; then 0.5C charge/0.5C discharge is carried out for cycle test, the ratio of the capacity corresponding to each cycle number to the initial capacity is the capacity retention rate corresponding to the cycle number, and then the capacity decay is obtained Curve (that is, the relationship between the cycle capacity retention rate and the number of cycles);

(11) Rate performance test: at a test temperature of 45°C, charge the battery to 4.45V at a constant current of 0.5C, charge it to 0.025C at a constant voltage, and discharge it to 3.0V at 0.2C after standing for 5 minutes. The capacity is the initial capacity; then 0.5C charge and 2C discharge are performed in sequence, and the ratio of the 2C discharge capacity to the initial capacity is the battery rate performance;

(12) Full-charge expansion rate test of the battery: use a screw micrometer to test the thickness d ₀ of the battery at the initial half-charge, and when the battery is fully charged, use a screw micrometer to test the thickness d _x of the battery at this time when the battery is fully charged. , and compared with the thickness d ₀ of the battery at the initial half-charge, the expansion rate of the fully charged battery at this time can be obtained (ie, the expansion rate=d ₀ /d _x ).

Example 1

1) Preparation of silicon-oxy-carbon composites

(11) Mix tetramethyl-tetravinyl-cyclotetrasiloxane, polymethylhydrogensiloxane, and ethanol according to a mass ratio of 50:50:400, and stir for 30 min to make the system evenly mixed to obtain organosilicon alkane solution;

(12) adopting the vacuum impregnation method, completely immersing the three-dimensional carbon skeleton material in the above-mentioned polysiloxane solution, and keeping it for 30 min to obtain an impregnated product; wherein, the three-dimensional carbon skeleton material is sheet-like;

(13) crosslinking the impregnated product at 80° C. for 2 hours to obtain a crosslinked product;

(14) In an argon atmosphere, the cross-linked product is heated to 1000°C at a heating rate of 5°C/min, pyrolyzed at 1000°C for 2 hours, and a SiOC layer is formed on the surface of the three-dimensional carbon skeleton material to obtain a matrix material;

(15) Using a carbon source as a raw material, the base material is subjected to CVD treatment to form a carbon layer on the surface of the base material to obtain a silicon oxycarbon composite material; wherein, after testing, the thickness of the carbon layer is 2 nm; Hierarchical pore structure of pores, mesopores and macropores.

2) Preparation of negative electrode sheet

Mix SiOx@SiMC@C and graphite in a mass ratio of 6:4 to obtain a mixed powder with a gram capacity of 650mAh/g, put the mixed powder, acetylene black and PAA in deionized water in a weight ratio of 95:1.2:3.8, After stirring evenly, a negative electrode slurry is prepared, and the negative electrode slurry is coated on the positive and negative surfaces of the copper foil. After drying and cold pressing, a negative electrode active material layer is formed on the positive and negative surfaces of the copper foil to obtain a negative electrode. piece.

3) Preparation of positive electrode sheet and battery

LiCoO ₂ , conductive carbon black, and PVDF were fully stirred and mixed in N-methylpyrrolidone at a weight ratio of 96.7:1.7:1.6, and then coated on both surfaces of Al foil (ie, the positive electrode current collector), and then dried. , cold pressing to form a positive electrode functional layer on the positive electrode current collector to obtain a positive electrode sheet;

With the PE porous polymer film as the separator, the positive electrode sheet, separator film and negative electrode sheet are stacked in sequence, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to isolate the film, and then rolled to form a bare cell, the bare battery The core is placed in the outer package, and the electrolyte is injected into it and packaged, and then the lithium ion battery is obtained after forming, degassing, trimming, etc.; wherein, the electrolyte is composed of LiPF ₆ , organic solvent and additives, and the organic solvent is EC , DMC, DEC, FEC composition, wherein, the volume percentage (vol%) ratio of EC, DMC, DEC in organic solvent is EC:DMC:DEC=1:1:1, the mass content of FEC in electrolyte is 10% , the concentration of LiPF ₆ in the electrolyte is 1mol/L, the additives include TFPB, 12-crown-4 ether, VC, the concentration of TFPB in the electrolyte is 0.1mol/L, and the concentration of 12-crown-4 ether in the electrolyte is 0.05mol/L, the concentration of VC in the electrolyte is 0.1mol/L.

Referring to the process of Example 1, the silicon oxycarbon composite materials, negative electrode sheets and batteries of Examples 1 to 15 and Comparative Examples 1 to 3 were obtained. In each example, the organosiloxane solution composition, step (13) ) in the crosslinking temperature, the heating rate in step (14), the pyrolysis temperature, and the pyrolysis time are shown in Table 1; the three-dimensional framework material and its thickness and length, the Raman spectrum test results of the three-dimensional carbon framework material I ₁₃₅₀ /I ₁₅₈₀ , thickness of SiOC layer, atomic ratio of silicon element to oxygen element in SiOC layer (Si:O), mass content of oxygen element in SiOC layer, mass of oxygen element in SiOC layer and total mass of oxygen element in silicon-oxygen-carbon composite material (m _O2 ) ratio (m _O1 /m _O2 ), mass content of the SiOC layer in the silicon oxycarbon composite material, ratio of the mass of the SiOC layer to the mass of carbon element in the silicon oxycarbon composite material (m ₂ /m ₁ ) , the ratio of Dv50 ₁ of SiOC material to Dv50 ₂ of three-dimensional carbon framework material (Dv50 ₁ /Dv50 ₂ ), thickness of carbon layer, Raman spectrum test result of carbon material in carbon layer I ₁₃₅₀ /I ₁₅₈₀ , silicon oxycarbon composite material The mass ratio of silicon to carbon (m _Si /m _c ), the binding energy peak position of Si 2p and the binding energy peak position of C 1s in the XPS test results of the silicon oxycarbon composite, and the sNMR of the silicon oxycarbon composite The Si shift in the test results and the K value of the half-peak width K ppm at -5ppm are shown in Table 2; among them,

Embodiment 16 does not carry out the cross-linking process of step (13);

The difference between Comparative Example 1 and the Example is that the silicon-oxygen-carbon composite material consists of a SiOC layer and a carbon layer on the surface of the SiOC layer (that is, there is no three-dimensional carbon skeleton material), which is denoted as SiOC layer@C;

The difference between Comparative Example 2 and the Example is that the silicon-oxygen-carbon composite material consists of a three-dimensional carbon framework material and a SiOC layer (ie, no carbon layer) existing on the surface of the three-dimensional carbon framework material, which is denoted as a three-dimensional carbon framework@SiOC layer;

The difference between the comparative example 3 and the embodiment is that the silicon oxycarbon composite material is a SiOC material (ie, there is no three-dimensional framework material and carbon layer).

Except for the differences shown in Table 1, the remaining conditions of each embodiment are basically the same.

The electrical conductivity, negative electrode sheet resistance, capacity retention rate, rate performance, and volume expansion rate of the battery when the battery is cycled 400 cycles are measured in Table 3. In addition, the variation curve of the capacity with the number of cycles in the battery cycle in Example 2 and Comparative Example 3 is measured as shown in Figure 2, and the capacity decay curve in the battery cycle in Example 2 and Comparative Example 3 is shown in Figure 3.

Table 1

Table 3 Performance test results

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (22)

1. A silicon oxycarbon composite material, characterized in that it comprises: a matrix material, the matrix material comprising a three-dimensional framework material and a SiOC layer on the surface of the three-dimensional framework material, the SiOC layer containing Si, O, and C elements; The carbon layer on the surface of the base material.
2. The silicon oxycarbon composite material according to claim 1, wherein the three-dimensional carbon framework material comprises 2 to 30 layers of graphene, and the three-dimensional carbon framework material has a thickness of 1 nm to 1 μm.
3. The silicon oxycarbon composite material according to claim 1 or 2, wherein the length of the three-dimensional carbon framework material is 0.5 μm to 10 μm.
4. The silicon oxycarbon composite material according to claim 1 or 2, wherein the three-dimensional carbon framework material is sheet-like.
5. The silicon oxycarbon composite material according to claim 1 or 2, wherein the Raman spectrum of the three-dimensional carbon framework material shows that the ratio of the peak height I ₁₃₅₀ of 1350 cm ^-1 and the peak height I ₁₅₈₀ of 1580 cm ^-1 0.7≦I ₁₃₅₀ /I ₁₅₈₀ ≦1.8 is satisfied.
6. The silicon oxycarbon composite material according to claim 1, wherein the thickness of the SiOC layer is 10 nm to 500 nm.
7. The silicon-oxygen-carbon composite material according to claim 1, wherein, in the SiOC layer, the atomic ratio of silicon element to oxygen element is 1:0.2 to 1:1.5.
8. The silicon oxycarbon composite material according to claim 1 or 7, wherein,

   Satisfy that m _Si /m _c is 1:0.05 to 1:1.2, m _Si is the mass of silicon element in the silicon oxycarbon composite material, and m _c is the mass of carbon element in the silicon oxygen carbon composite material;

   and / or,

   It is satisfied that m _O1 /m _O2 is 1:1 to 1:1.1, m _O1 is the mass of the oxygen element in the SiOC layer, and m _O2 is the mass of the oxygen element in the silicon-oxygen-carbon composite material.
9. The silicon oxycarbon composite material according to claim 1, wherein the SiOC layer comprises a SiOC material containing Si, O, and C elements, and the particle size of the SiOC material is Dv50 ₁ and the particle size of the three-dimensional carbon framework material. Dv50 ₂ satisfies: Dv50 ₁ /Dv50 ₂ is 1:5 to 1:50, Dv50 ₁ represents the particle size of the SiOC material particles from the small particle size side and reaches 50% of the volume accumulation in the particle size distribution based on volume, Dv50 ₂ represents In the particle size distribution on a volume basis, the three-dimensional carbon skeleton material particles reach a particle size of 50% by volume accumulation from the small particle size side.
10. The silicon oxycarbon composite material according to claim 1, wherein m ₂ /m ₁ is 2 to 20, m ₂ is the mass of the SiOC layer, and m ₁ is the carbon in the silicon oxycarbon composite material The total mass of the element.
11. The silicon oxycarbon composite material according to claim 1, wherein the thickness of the carbon layer is 0.1 nm to 10 nm.
12. The silicon-oxygen-carbon composite material according to claim 1, wherein the carbon layer comprises a carbon material, and the Raman spectrum of the carbon material shows that a peak height of 1350 cm ^-1 is ₁₃₅₀ and a peak height of 1580 cm- ¹ is The ratio of I ₁₅₈₀ satisfies 0.7≦I ₁₃₅₀ /I ₁₅₈₀ ≦1.8.
13. The silicon oxycarbon composite material according to claim 1, characterized in that it has at least one of micropores, mesopores or macropores.
14. The silicon-oxygen-carbon composite material according to claim 1, wherein in the X-ray photoelectron spectroscopy analysis result, the binding energy peak positions of Si 2p include 101.4±0.3eV, 102.2±0.3eV, 103.1±0.3eV or At least one of 104.40 ± 0.3 eV, and the binding energy peak position of C 1s includes at least one of 283.8 ± 0.3 eV, 284.6 ± 0.3 eV, 286.3 ± 0.3 eV or 104.40 ± 0.3 eV.
15. The silicon-oxygen-carbon composite material according to claim 1 or 14, characterized in that, in the solid-state nuclear magnetic test results, the shifts of silicon include -5ppm, -35ppm, -75ppm, -110ppm, and the half-peak width at -5ppm K ppm satisfies 7<K<28.
16. The method for preparing a silicon oxycarbon composite material according to any one of claims 1 to 15, characterized in that it comprises: impregnating the three-dimensional carbon skeleton material with a solution containing organosiloxane, and dipping the obtained impregnated product into Pyrolysis treatment, forming the SiOC layer on the surface of the three-dimensional carbon skeleton material to obtain the base material; using chemical vapor deposition to form the carbon layer on the surface of the base material to obtain the silicon oxycarbon composite material.
17. A negative electrode sheet, characterized in that it comprises a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material comprises claim 1 - The silicon oxycarbon composite material of any one of 15.
18. The negative electrode sheet according to claim 17, wherein the negative electrode active material further comprises graphite.
19. The negative electrode sheet according to claim 17 or 18, wherein, in the negative electrode active material, the mass content of the silicon oxycarbon composite material is 40% to 80%.
20. The negative electrode sheet according to claim 17 or 18, characterized in that,

    The electrical conductivity of the negative electrode active material is 2S/cm to 30S/cm;

    and / or,

    The resistance of the negative electrode sheet is 0.2Ω to 1Ω.
21. An electrochemical device, characterized by comprising the negative electrode sheet according to any one of claims 17-20.
22. An electronic device, characterized by comprising the electrochemical device of claim 21 .

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