Silicon-carbon composite material and its manufacturing method, electrochemical device, electronic device

Abstract

To provide: a silicon-carbon composite material having a capacitance of a final material and an initial efficiency effectively improved by restricting expansion of a silicon-based material as far as possible and retaining long-term cycle stability and excellent conductivity thereof and a production method thereof; an anode sheet; and an electrochemical device and electronic device.SOLUTION: A silicon-carbon composite material includes an amorphous carbon matrix and a silicon material located on a surface and / or an inside of the amorphous carbon matrix, and has a specific surface area coefficient B of 20-1,250. A production method thereof includes obtaining the silicon-carbon composite material by synthesizing the amorphous carbon matrix material and a silicon source by a chemical vapor deposition method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of secondary batteries, and in particular to silicon-carbon composite materials and their manufacturing methods, electrochemical devices, and electronic devices. [Background technology]

[0002] With the increasing popularity of various portable electronic devices and the rapid development of electric vehicles and renewable energy storage systems, the requirements for the energy density, power density, cycle life, and safety of lithium-ion batteries are now higher than ever before. Currently, the energy density of common NCM ternary material (cathode) / graphite (anode) lithium-ion batteries is approaching its theoretical limit. Regarding anode materials, the actual specific capacity of graphite (up to 360 mAh / g) is close to the theoretical specific capacity (372 mAh / g). Silicon has a much higher theoretical specific capacity (-3600 mAh / g) and a lower discharge platform (-0.2 V vs. Li) than graphite. + Silicon-based anode materials have attracted widespread attention due to their high lithium content (e.g., lithium ion / Li) and abundant resources. However, their commercialization is limited by the large volume changes during the lithium insertion and extraction process, which makes them susceptible to crushing, breakage, and peeling from the current collector. Furthermore, continuous interfacial side reactions cause a rapid decrease in the specific capacity of the materials during cycling.

[0003] To solve the above problems, structural design of silicon-based materials such as nanoscale, composite, hollow / porous materials has become a popular research topic. x Although pure silicon materials can buffer the expansion of the material to some extent, their initial coulombic efficiency is only about 75%. Prelithiation or graphite composites also have initial coulombic efficiencies of only about 80% to 85%. Both of these materials are based on the positive electrode ternary layered material (LiNi x Co y Mn 1-x-yThis is lower than the initial efficiency of 88% for the cathode (LiFePO4) and 98% for the cathode (LiFePO4), and offers no advantage over batteries using graphite as the anode material. It has been reported that the surface coating layer of hollow / porous silicon materials is often prone to cracking or shattering when subjected to large pressures. Although the space reserved for expansion within the material is compressed and released, the material and battery still experience large volume expansion during charging and discharging. Interfacial side reactions between the material and the electrolyte continue, eliminating the inherent advantages of the material. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a silicon-carbon composite material that structurally suppresses the expansion of silicon-based materials to the maximum extent possible, a method for producing the same, a negative electrode sheet, an electrochemical device, and an electronic device. [Means for solving the problem]

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a silicon-carbon composite material, a manufacturing method thereof, a negative electrode sheet, an electrochemical device, and an electronic device, which structurally suppress the expansion of silicon-based materials to the greatest extent possible, ensure long-term cycle stability and excellent conductivity, solve the problems of low capacity and initial efficiency of silicon-based materials in the prior art, and ensure certain processing performance.

[0006] To achieve the above and other related objectives, a first aspect of the present invention provides a silicon-carbon composite material comprising an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix.

[0007] Silicon-carbon composite materials satisfy the following relationship:

[0008] B=B A / B a

[0009] The value range of B is 20 to 1250.

[0010] B is the specific surface area coefficient (i.e., BET coefficient) of the silicon-carbon composite, and B A is the specific surface area of ​​the amorphous carbon matrix, and B a is the specific surface area of ​​the silicon-carbon composite.

[0011] The range B of the specific surface area coefficient of the silicon-carbon composite material is 100-900, and preferably 150-500.

[0012] In addition, the specific surface area B of the amorphous carbon matrix A The range is 500m 2 / g~2500m 2 / g, preferably 800m 2 / g~1800m 2 / g.

[0013] In addition, the specific surface area B of the silicon-carbon composite a The range is 2m 2 / g~25m 2 / g, preferably 2m 2 / g~8m 2 / g.

[0014] Furthermore, the silicon-carbon composite material satisfies the following relationship:

[0015] P v =P v1 / P v2

[0016] P v The value range is 0.4 to 120.

[0017] P v represents the pore volume coefficient of the silicon-carbon composite, and P v1 represents the pore volume diameter of the amorphous carbon matrix, and P v2 represents the pore volume diameter of the silicon-carbon composite material.

[0018] In addition, the pore volume coefficient P of the silicon-carbon composite vThe range is 1 to 100, preferably 10 to 90.

[0019] In addition, the pore volume diameter P of the amorphous carbon matrix v1 The value range is 0.2 cm 3 / g~0.9cm 3 / g, preferably 0.2 cm 3 / g~0.8cm 3 / g, more preferably 0.2 cm 3 / g~0.7cm 3 / g.

[0020] In addition, the pore volume diameter P v2 The range is 0.005cm 3 / g~0.2cm 3 / g, preferably 0.008 cm 3 / g~0.02cm 3 / g.

[0021] Furthermore, the weight loss due to thermal decomposition of a silicon-carbon composite material heated to 1400°C in an air atmosphere is 5% to 60%, preferably 24% to 42%, or 15% to 40%.

[0022] A second aspect of the present invention provides a method for producing a silicon-carbon composite material, comprising the steps of: synthesizing an amorphous carbon matrix material and a silicon source by chemical vapor deposition to obtain a silicon-carbon composite material, the silicon-carbon composite material comprising an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix.

[0023] Silicon-carbon composite materials satisfy the following relationship:

[0024] B=B A / B a .

[0025] The value range of B is 20 to 1250.

[0026] B is the specific surface area coefficient of the silicon-carbon composite, and B A is the specific surface area of ​​the amorphous carbon matrix, and B a is the specific surface area of ​​the silicon-carbon composite.

[0027] The silicon source is at least one selected from monosilane (SiH4), dimethyldichlorosilane, trichloromethylsilane, tetramethylsilane, trichlorosilane, tetrachlorosilane, methyl silicate, and ethyl silicate.

[0028] Additionally, the amorphous carbon matrix material is porous amorphous carbon.

[0029] The amorphous carbon matrix material is also a porous amorphous carbon-metal composite, which includes a porous amorphous carbon matrix and metal nanoparticles located on the surface and / or within the porous amorphous carbon matrix.

[0030] A third aspect of the present invention provides a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material. The negative electrode active material includes the silicon-carbon composite material according to the first aspect and / or the silicon-carbon composite material produced according to the method according to the second aspect.

[0031] A fourth aspect of the present invention provides an electrochemical device comprising the negative electrode sheet according to the third aspect.

[0032] A fifth aspect of the present invention provides an electronic device comprising an electrochemical device according to the fourth aspect.

[0033] As described above, the silicon-carbon composite material and its manufacturing method, negative electrode sheet, electrochemical device, and electronic device of the present invention provide the following effects.

[0034] In the present invention, the specific surface area coefficient B of the silicon-carbon composite material is controlled within the above range to ensure long-term cycling stability and improve capacity and initial efficiency. Based on the specific surface area of ​​the silicon-carbon composite material being within a certain range, if the specific surface area coefficient is too high, the specific surface area of ​​the amorphous carbon matrix will be too large, reducing the uniformity of the subsequent silicon material introduction and further reducing the cycling stability of the subsequent silicon-carbon composite material. If the specific surface area coefficient is too low, the specific surface area of ​​the amorphous carbon matrix will be too small, reducing the active sites for silicon introduction and the amount of silicon added, resulting in a lower capacity of the resulting material and not contributing to achieving a high energy density of the battery cell.

[0035] Pore ​​volume coefficient P of silicon-carbon composites v By maintaining the pore volumes of the silicon-carbon composite and amorphous carbon within the above ranges, the content of silicon subsequently introduced can be controlled, thereby controlling the capacity of the material and contributing to balancing the energy density and cycling performance of the lithium-ion battery.

[0036] By controlling the content of various elements and the thermal decomposition loss in the silicon-carbon composite material within the above ranges, long-term cycle stability can be ensured and the capacity and initial efficiency can be improved. If the thermal decomposition loss is too high and the C content is too high, it becomes difficult to achieve high capacity in the material and high energy density in the battery cell. If the thermal decomposition loss is too low and the Si content is too high, it becomes difficult to achieve better cycle stability. [Effects of the Invention]

[0037] The present invention relates to the structure of silicon-carbon composite materials, the specific surface area coefficient B, the pore volume coefficient P vBy controlling the content of various elements and the loss due to thermal decomposition, the expansion of the silicon-based material is minimized, ensuring long-term cycle stability and excellent conductivity, thereby effectively improving the capacity and initial efficiency of the final material and facilitating the commercialization of silicon-based anode materials while maintaining consistent processing performance. At the same time, the method for producing the silicon-carbon composite material of the present invention is simple and easy to operate, making it suitable for large-scale industrial production. The silicon-carbon composite material provided by the present invention can be used as an anode active material by applying it to a layer of anode active material to form an anode sheet, which can then be assembled with a cathode sheet, separator, electrolyte, etc. to form an electrochemical device such as a lithium-ion battery, significantly improving its electrical performance. [Brief explanation of the drawings]

[0038] [Figure 1] 1 shows a schematic structural diagram of a silicon-carbon composite material in one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be described below with reference to specific examples, but those skilled in the art will readily understand other advantages and effects of the present invention from the contents disclosed herein. The present invention may be implemented or applied through other different specific embodiments, and the details of the present specification may be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] One embodiment of the present invention provides a silicon-carbon composite material that includes an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix.

[0041] Silicon-carbon composite materials satisfy the following relationship:

[0042] B=B A / B a

[0043] The value range of B is 20 to 1250.

[0044] B is the specific surface area coefficient of the silicon-carbon composite, and B A is the specific surface area of ​​the amorphous carbon matrix, and B a is the specific surface area of ​​the silicon-carbon composite.

[0045] In some embodiments, the specific surface area coefficient B of the silicon-carbon composite material ranges from 100 to 900, more preferably from 150 to 500. The specific surface area B of the amorphous carbon matrix A The value range is 500m 2 / g~2500m 2 / g, preferably 800m 2 / g~1800m 2 / g. The specific surface area of ​​the silicon-carbon composite material is B a The value range is 2m 2 / g~25m 2 / g, preferably 2m 2 / g~8m 2 / g.

[0046] In the above embodiment, controlling the specific surface area coefficient B of the silicon-carbon composite material within the above range ensures long-term cycling stability and contributes to improving capacity and initial efficiency. Based on the specific surface area of ​​the silicon-carbon composite material being within a certain range, if the specific surface area coefficient is too high, the specific surface area of ​​the amorphous carbon matrix will be too large, which will help the subsequent uniformity of silicon material loading but will reduce the subsequent cycling stability of the silicon-carbon composite material. If the specific surface area coefficient is too low, the specific surface area of ​​the amorphous carbon matrix will be too small, which will reduce the active sites for silicon loading and lead to a reduced amount of silicon loading, resulting in a lower capacity of the final material and not contributing to achieving a higher energy density of the battery cell.

[0047] In another embodiment of the present invention, the silicon-carbon composite material satisfies the following relationship:

[0048] P v =Pv1 / P v2

[0049] P v The value range is 0.4 to 120.

[0050] P v represents the pore volume coefficient of the silicon-carbon composite, and P v1 represents the pore volume diameter of the amorphous carbon matrix, and P v2 represents the pore volume diameter of the silicon-carbon composite material.

[0051] In some embodiments, the P of the silicon-carbon composite v The value range of is 1 to 100, preferably 10 to 90. The pore volume diameter Pv1 of the amorphous carbon matrix is ​​0.2 cm 3 / g~0.9cm 3 / g, preferably 0.2 cm 3 / g~0.8cm 3 / g, more preferably 0.2 cm 3 / g~0.7cm 3 / g. The pore volume diameter P v2 is 0.005cm 3 / g~0.2cm 3 / g, preferably 0.008 cm 3 / g~0.02cm 3 / g.

[0052] In the above embodiments, maintaining the pore volume coefficient of the silicon-carbon composite and the pore volumes of the silicon-carbon composite and amorphous carbon within the above ranges helps control the amount of silicon subsequently incorporated, thereby controlling the capacity of the material and helping to balance the energy density and cycling performance of the lithium-ion battery.

[0053] In another embodiment of the present invention, the weight loss due to pyrolysis of a silicon-carbon composite heated to 1400°C in an air atmosphere ranges from 5% to 60%, preferably from 24% to 42% or from 15% to 40%.

[0054] In another embodiment of the present invention, the mass ratio of carbon:silicon in the silicon-carbon composite material is 3-8:2-7.

[0055] In the above embodiment, controlling the content of various elements and the thermal decomposition loss in the silicon-carbon composite material within the above ranges contributes to ensuring long-term cycle stability and improving capacity and initial efficiency. If the thermal decomposition loss is too high and the C content is too high, it becomes difficult to achieve high capacity of the material and high energy density of the battery cell. If the thermal decomposition loss is too low and the Si content is too high, it becomes difficult to achieve better cycle stability.

[0056] In some embodiments, the amorphous carbon matrix is ​​a porous carbon material, and the silicon material is uniformly distributed on the surface and / or pore walls of the amorphous carbon matrix. Figure 1 shows a schematic structural diagram of a silicon-carbon composite material provided by an embodiment of the present invention. The amorphous carbon matrix is ​​a porous carbon material, and the silicon material is uniformly distributed on the pore walls of the amorphous carbon matrix.

[0057] In some embodiments, the silicon material is Si and SiO x At least one selected from the following.

[0058] In some embodiments, the silicon material is nanoscale, and the particle size of the silicon material is 1 nm to 20 nm, preferably 1 nm to 5 nm.

[0059] In some embodiments, the silicon material is rod-shaped and / or granular, including but not limited to spherical, quasi-spherical, or acicular particles.

[0060] In another embodiment of the present invention, the silicon-carbon composite further comprises nanometal particles attached to the surface and / or interior of the amorphous carbon matrix. In some embodiments, the amorphous carbon matrix is ​​a porous carbon material, and the nanometal is uniformly distributed on the surface and / or pore walls of the amorphous carbon matrix. The mass ratio of the nanometal particles in the silicon-carbon composite may be greater than 0% to 2%. The nanometal particles are at least one type selected from titanium, iron, copper, nickel, cobalt, manganese, silver, gold, and tin particles. The nanometal particles have a particle size of 2 nm to 5 nm.

[0061] One embodiment of the present invention provides a method for producing a silicon-carbon composite material, comprising the steps of: synthesizing an amorphous carbon matrix material and a silicon source by chemical vapor deposition to obtain a silicon-carbon composite material, the silicon-carbon composite material comprising an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix.

[0062] Silicon-carbon composite materials satisfy the following relationship:

[0063] B=B A / B a

[0064] The value range of B is 20 to 1250.

[0065] B is the specific surface area coefficient of the silicon-carbon composite, and B A is the specific surface area of ​​the amorphous carbon matrix, and B a is the specific surface area of ​​the silicon-carbon composite.

[0066] In some embodiments, the silicon source is at least one selected from monosilane (SiH4), dimethyldichlorosilane, and trichloromethylsilane.

[0067] In some embodiments, the amorphous carbon matrix material is porous amorphous carbon.

[0068] In some embodiments, the amorphous carbon matrix material is a porous amorphous carbon-metal composite, which comprises a porous amorphous carbon matrix and nanometal particles attached to the surface and / or within the porous amorphous carbon matrix.

[0069] In some embodiments, a method for producing a porous amorphous carbon-metal composite includes the following steps: attaching metal nanoparticles to the surface and / or interior of a porous amorphous carbon matrix by mechanical mixing (e.g., stirring), liquid-phase reduction, or vapor-phase reduction. Preferably, the nanometal particles are at least one selected from titanium, iron, copper, nickel, cobalt, manganese, silver, gold, and tin particles. Specifically, in the embodiments of the present invention, the mechanical mixing method, liquid-phase reduction method, and vapor-phase reduction method employed to attach the nanometal particles to the surface and / or interior of the porous amorphous carbon matrix are conventional and well-known techniques, and no special requirements apply. Therefore, further details are omitted.

[0070] In another embodiment of the present invention, a method for producing a silicon-carbon composite material includes the following steps: placing an amorphous carbon matrix material and a silicon source in a chemical vapor deposition reactor, using hydrogen as a carrier gas and hydrogen and / or argon as a diluent gas at a flow rate of 1 L / min to 5 L / min, raising the temperature to 400°C to 600°C, and reacting for 1 hour to 20 hours, followed by pyrolysis synthesis to obtain a silicon-carbon composite material.

[0071] The silicon-carbon composite material described in the above embodiment can be produced by the method described in the above example, but is not limited to this.

[0072] One embodiment of the present invention provides a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, the negative electrode active material including the silicon-carbon composite material described in the above embodiments and / or a silicon-carbon composite material produced according to the method described in the above embodiments. In some embodiments, the negative electrode active material includes 24% to 45% by mass of the silicon-carbon composite material.

[0073] One embodiment of the present invention provides an electrochemical device including the negative electrode sheet, positive electrode sheet, separator, and electrolyte described in the above embodiment.

[0074] The electrochemical device in embodiments of the present invention may be any electrochemical device, such as, but not limited to, a lithium ion battery or a sodium ion battery.

[0075] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0076] The positive electrode active material generally includes lithium-containing composite oxides, such as LiMnO2, LiFeO2, LiMn2O4, Li2FeSiO4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi5CO2Mn3O2, Li z Ni (1-x-y) Co x M y O2 (wherein 0.01≦x≦0.20, 0≦y≦0.20, 0.97≦z≦1.20, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, and Al), LiFePO4, and Li z CO (1-x) M x O2 (wherein 0≦x≦0.1, 0.97≦z≦1.20, and M represents at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb, and Al).

[0077] Generally, conductive agents, binders, and other materials are added to the active material. The amount of these additives can be adjusted as needed within the range of 1% to 50% of the total mass of the positive electrode active material, or 55% to 76% of the total mass of the active material.

[0078] Conductive agents are reagents used to improve the charge-discharge performance of electrodes. Examples include graphite materials such as natural graphite and artificial graphite, carbon black materials such as conductive carbon black (Super P), conductive fibers such as carbon fiber and metal fiber, such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, metal powders such as carbon fluoride powder, aluminum powder, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, and conductive metal oxides such as titanium dioxide and polyphenylene derivatives.

[0079] Binders are components that promote the bonding between the active material and the conductive agent, and between the active material and the current collector. Typically, binders can be selected from the following: polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid (PAA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, styrene-propylene rubber, fluororubber, and various copolymers.

[0080] The current collector functions as a substrate that supports the electrode active material, and is usually made of a metal foil with a thickness of 3 to 500 microns. There are no particular restrictions on the material, as long as it has high conductivity and does not cause a chemical reaction within the secondary battery system. For example, the material may be a foil material obtained by surface-treating nickel, titanium, aluminum, silver, stainless steel, carbon, or the like. The surface of the current collector is usually smooth, but fine wires may be formed on the surface to improve adhesion between the positive electrode active material and the current collector. In addition to foil, the current collector may be used in any one or combination of various forms such as film, mesh, porous material, foam, nonwoven fabric, etc.

[0081] The separator is placed between the positive electrode sheet and the negative electrode sheet, and is usually made of an insulating film with high ion permeability and mechanical strength. The separator's thickness is usually 9 μm to 18 μm, its pore size is 5 μm to 300 μm, its air permeability is 180 sec / 100 mL to 380 sec / 100 mL, and its porosity is 30% to 50%. The separator is made of a sheet or nonwoven fabric made of chemical-resistant and hydrophobic polypropylene, glass fiber, or an olefin polymer such as polyethylene.

[0082] The electrolyte used in lithium-ion batteries generally includes a non-aqueous solvent, a lithium salt, and an additive.

[0083] The non-aqueous solvent may be a conventional non-aqueous solvent in the art, preferably an ester solvent, more preferably a carbonate solvent. Specifically, the carbonate solvent may be at least one selected from ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0084] Lithium salts include LiPF6, LiBF4, LiN(SO2F)2 (abbreviated as LiFSI), LiClO4, LiAsF6, LiB(C2O4)2 (abbreviated as LiBOB), LiBF2(C2O4) (abbreviated as LiDFOB), LiN(SO2R F)2, and LiN(SO2F)(SO2R F ) Preferably, the content of the lithium salt in the electrolyte is 5% to 20%.

[0085] The additive may be at least one selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), vinylene sulfate, 1,3-propane sultone (PS), 1-propene 1,3-sultone, and 1,4-butane sultone. The additive is typically added in an amount of 1% to 4% of the electrolyte, for example, 2%.

[0086] In some embodiments, the negative electrode active material includes a silicon-carbon composite material, graphite, conductive carbon black, and a binder. The negative electrode active material preferably contains, by mass, 24% to 45% silicon-carbon composite material, 40% to 63% graphite, 2% to 8% conductive carbon black, and 2% to 18% binder.

[0087] In some embodiments, the method for producing the negative electrode sheet described in the above embodiments includes the following steps.

[0088] A silicon-carbon composite and graphite are mixed at high speed in a mass ratio of 30-50:70-50 to prepare a negative electrode active material mixture powder, which is then thoroughly mixed with conductive carbon black and a binder in an appropriate amount of deionized water in a mass ratio of 80-90:2-8:2-18 to form a uniform negative electrode slurry. The negative electrode slurry is applied to the surface of the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0089] It should be noted that in the above-mentioned embodiments of the present invention, other process conditions and parameters in the preparation process of the negative electrode sheet are not described in detail, and those skilled in the art can obtain the negative electrode sheet by using the method described in the above-mentioned embodiments in combination with conventional technical means and common sense.

[0090] One embodiment of the present invention provides an electronic device including the electrochemical device described in the above embodiment.

[0091] The electronic device in the present embodiment may be any electronic device, such as, but not limited to, a notebook computer, a pen-based computer, a mobile computer, an e-book player, a mobile phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headphone, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc, a walkie-talkie, an electronic organizer, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electrically assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large-scale household storage battery, and a lithium-ion capacitor. The electrochemical device of the present invention is applicable not only to the electronic devices listed above, but also to energy storage power plants, maritime transport vehicles, and air transport vehicles. Air transport vehicles include both atmospheric and extraterrestrial air transport vehicles.

[0092] It should be noted that the above-described embodiments of the present invention do not provide detailed descriptions of the packaging methods and steps for the lithium ion battery, and those skilled in the art can assemble the positive electrode sheet and the negative electrode sheet according to conventional or common technical means and common knowledge in the art to package the positive electrode sheet, the negative electrode sheet, the electrolyte, and the separator to form a lithium ion battery.

[0093] The following specific examples are provided to explain the present invention in detail. It should also be understood that the following examples are used solely to specifically explain the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art according to the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters in the following examples are merely examples of appropriate ranges. Those skilled in the art can select within the appropriate ranges through the explanations in this specification and are not limited to the specific numerical values ​​exemplified below.

[0094] Example 1

[0095] In this example, a silicon-carbon composite material was prepared, and the specific preparation process is as follows:

[0096] Specific surface area 1000m 2 / g, pore volume 0.54 cm 3 500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material, and the fluidized bed was heated to 500°C. After the temperature stabilized, monosilane was introduced at 3 L / min for 95 minutes, and the pressure of the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, The inert gas was continuously introduced until the reaction product was cooled to room temperature, yielding a silicon-carbon composite material.

[0097] Example 2

[0098] In this example, a silicon-carbon composite material was prepared, and the specific preparation process is as follows:

[0099] Specific surface area 800m 2 / g, pore volume 0.54 cm 3500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 500°C. After the temperature stabilized, monosilane was introduced at 2 L / min for 95 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite material.

[0100] Example 3

[0101] In this example, a silicon-carbon composite material is prepared, and the specific preparation process is as follows:

[0102] Specific surface area 1000m 2 / g, pore volume 0.2 cm 3 500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 500°C. After the temperature stabilized, monosilane was introduced at 5 L / min for 95 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite material.

[0103] Example 4

[0104] In this example, a silicon-carbon composite material was prepared, and the specific preparation process is as follows:

[0105] Specific surface area 1200m 2 / g, pore volume 0.7 cm 3 500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 600°C. After the temperature stabilized, monosilane was introduced at 1 L / min for 60 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite material.

[0106] Comparative Example 1

[0107] In this example, a silicon-carbon composite material was prepared, and the specific preparation process is as follows:

[0108] Specific surface area 1800m 2 / g, pore volume 0.68 cm 3 500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 500°C. After the temperature stabilized, monosilane was introduced at 1 L / min for 60 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite.

[0109] Comparative Example 2

[0110] In this example, a silicon-carbon composite material was prepared, and the specific preparation process is as follows:

[0111] Specific surface area 200m 2 / g, pore volume 0.4 cm 3 500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 500°C. After the temperature stabilized, monosilane was introduced at 1 L / min for 60 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite.

[0112] Comparative Example 3

[0113] Specific surface area 1000m 2 / g, pore volume 0.12 cm 3500 g of porous amorphous carbon material with a molecular weight of 1 / g was added to the fluidized bed, and nitrogen gas was introduced at 10 L / min to fluidize the material. The fluidized bed was then heated to 500°C. After the temperature stabilized, monosilane was introduced at 1 L / min for 60 minutes, and the pressure in the fluidized bed was controlled at 6 kPa. The introduction of monosilane gas was stopped, and inert gas was continued until the reaction product cooled to room temperature, yielding a silicon-carbon composite.

[0114] Example 5

[0115] In the present examples, lithium ion batteries were fabricated according to the following method using the silicon-carbon composite materials of Examples 1 to 4 and Comparative Examples 1 to 3. The specific steps are as follows.

[0116] 1. Preparation of the positive electrode sheet

[0117] Ternary material LiNi 0.8 Co 0.1 Mn 0.1 A positive electrode active material mixture powder was prepared by stirring and mixing O2 at high speed. Conductive carbon black (Super P), conductive carbon tubes (CNT), nitrogen methylpyrrolidone solvent (NMP), and polyvinylidene fluoride (PVDF) were dispersed in a mass ratio of 1:0.5:40 and stirred at high speed for 2 hours. The mixed active material powder and conductive slurry were mixed at high speed to prepare a positive electrode slurry with a specified viscosity. The prepared slurry was uniformly coated on aluminum foil using a doctor blade, placed in a fan drying oven, and dried at 120°C for 20 minutes. Finally, the dried electrode sheet was rolled and cut to prepare a positive electrode sheet.

[0118] 2. Preparation of the negative electrode sheet

[0119] The prepared silicon-based material and graphite with a D50 of 10 μm were mixed at high speed with stirring at a mass ratio of 40:60 to prepare a negative electrode active material mixture powder. Next, Super P and PAA (polyacrylic acid) were mixed in an appropriate amount of deionized water with sufficient stirring at a mass ratio of 85:5:10 to form a uniform negative electrode slurry. The negative electrode slurry was applied to the surface of the copper foil of the negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0120] 3. Preparation of electrolyte:

[0121] The organic solvent was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of 20:20:60. In an argon atmosphere glove box with a water content of less than 10 ppm, completely dried lithium salt (LiPF6) was dissolved in the above organic solvent and mixed uniformly to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0122] 4. Preparation of insulating films:

[0123] A polypropylene insulating film with a thickness of 12 μm was selected.

[0124] 5. Battery Fabrication:

[0125] The positive electrode sheet, separator, and negative electrode sheet prepared as described above were stacked in this order, with a separator placed between the positive and negative electrode sheets to provide insulation. The outer surface was then wrapped in aluminum plastic film, transferred to a vacuum oven, dried at 120°C, and sealed after 3.0 g / Ah of electrolyte was injected. After standing, hot and cold pressing, chemical formation, fixing, and grading, a pouch battery (i.e., a lithium-ion battery) with a capacity of 1 Ah was finally obtained.

[0126] Powder tests were carried out on the silicon-carbon composite materials of Examples 1 to 4 and Comparative Examples 1 to 3 according to the following methods. Specifically, the tests were carried out as follows.

[0127] 1. Test method for BET coefficient and pore volume:

[0128] The test sample (80 mg - 2 g) was placed in a sample tube in a degassing tank, and nitrogen was added to the tube, which was then heated at 300 °C for 1 hour to remove any gas adsorbed on the surface. After degassing was complete and the test sample was cooled to room temperature, the quality of the test sample was measured, and the weighed sample tube was placed in the analysis station. The Dewar vessel was filled with liquid nitrogen, and the mass of the test sample was entered into the analysis file. The test parameters were set, and the adsorption and desorption test process was carried out. The specific surface area, pore volume, and other information of the material were calculated using the adsorption and desorption isotherm. Here, the specific surface area of ​​the porous carbon is defined as B A and the pore volume is P v1 The specific surface area of ​​the silicon-carbon composite material was B a and the pore volume is P v2 It was decided.

[0129] 2.TG test method:

[0130] A 5 mg test sample was placed in the sample chamber and heated to 1400°C at a rate of 10°C / min in an air atmosphere, and a mass vs. temperature curve was collected.

[0131] The initial mass was recorded as W0 and the mass after heating was recorded as W1. The weight loss was:

[0132] W loss=(W0-W1) / W0× 100%

[0133] Powder test results for Examples 1 to 4 and Comparative Examples 1 to 3

[0134] [Table 1]

[0135] The electrical characteristics of the lithium ion battery implemented in Example 5 were tested according to the following method as follows.

[0136] The mounted lithium-ion battery was charged to 4.2V at a constant current of 1C, then charged to 0.05C at a constant voltage of 4.2V and left for 10 minutes, and then discharged to 2.8V at a constant current of 1C and left for 10 minutes. The above charge and discharge constituted a cycle of the charge-discharge process, and the discharge capacity of this cycle was recorded. The charge-discharge process was repeated 100 times, and the discharge capacity of each cycle was recorded.

[0137] Cycle capacity retention rate (%) = 100th cycle discharge capacity / 1st cycle discharge capacity × 100%

[0138] Battery mass energy density (Wh / kg) = first discharge energy / battery mass.

[0139] Electrical performance test results of lithium ion batteries manufactured from powders of Examples 1 to 4 and Comparative Examples 1 to 3

[0140] [Table 2]

[0141] In Table 1, the W loss is mainly due to carbon, i.e., the actual silicon content is 1-W loss.

[0142] Analysis of the data in Tables 1 and 2 reveals that the amount of silicon loaded in the silicon-carbon composite manufacturing process is determined by the specific surface area and pore volume of the porous amorphous carbon. A large specific surface area and large pore volume result in silicon deposition within the pores. However, too large a specific surface area or pore volume results in too much silicon, leading to poor circulation. A large specific surface area and small pore volume result in silicon deposition on the surface, making circulation difficult. A small specific surface area and large pore volume limit the amount of silicon deposition, making silicon more likely to agglomerate and making circulation difficult. A small specific surface area and small pore volume result in silicon not being able to deposit, resulting in significant capacity loss.

[0143] The lithium-ion batteries fabricated using the silicon-carbon composite materials of Examples 1 to 4 had higher cycle capacities and cycle capacity retention rates of 90% or higher compared to the lithium-ion batteries fabricated using the silicon-carbon composite materials of Comparative Examples 1 and 3. This is because the amount of silicon loaded is determined by the specific surface area and pore volume of the porous amorphous carbon during the manufacturing process of the silicon-carbon composite material. A large specific surface area and a large pore volume result in silicon deposition within the pores. However, too large a specific surface area or pore volume results in too much silicon, leading to poor circulation. A large specific surface area and a small pore volume result in silicon deposition on the surface, making circulation difficult. A small specific surface area and a large pore volume limit the amount of silicon deposition, making silicon more likely to aggregate and making circulation difficult. A small specific surface area and a small pore volume prevent silicon deposition, resulting in significant capacity loss.

[0144] The lithium-ion battery fabricated using the silicon-carbon composite material of Comparative Example 2 had a cycle capacity retention rate of 95.4%, but its mass energy density was significantly lower than those of Examples 1 to 4. This was because the specific surface area of ​​the porous amorphous carbon and the BET coefficient of the composite material were too small, reducing the number of active sites for silicon to be introduced, reducing the amount of silicon added and resulting in a decrease in the capacity of the final product, making it difficult to achieve a higher energy density for the battery cell.

[0145] The weight loss due to thermal decomposition of the silicon-carbon composite material of Comparative Example 1 is low compared to Examples 1 to 4. Correspondingly, the cycle capacity retention rate of the lithium ion battery obtained by using the silicon-carbon composite material of Comparative Example 1 is significantly lower than those of Examples 1 to 4. This is because the Si content is too high, making it difficult to achieve better cycle performance.

[0146] In summary, the present invention provides a silicon-carbon composite with a structure, a specific surface area coefficient B, a pore volume coefficient P, and a vBy controlling the content of various elements and the loss due to thermal decomposition, the expansion of the silicon-based material is minimized, ensuring long-term cycle stability and excellent conductivity, thereby effectively improving the capacity and initial efficiency of the final material and facilitating the commercialization of silicon-based anode materials while maintaining consistent processing performance. At the same time, the method for producing the silicon-carbon composite material of the present invention is simple and easy to operate, making it suitable for large-scale industrial production. The silicon-carbon composite material provided by the present invention is used as an anode active material and is applied to an anode active material layer to form an anode sheet, which is then assembled with a cathode sheet, separator, electrolyte, etc. to form a lithium-ion battery. This can significantly improve the electrical performance of the lithium-ion battery and promote the development of lithium-ion batteries. [Industrial Applicability]

[0147] The silicon-carbon composite material and its manufacturing method, anode sheet, electrochemical device and electronic device of the present invention can accelerate the commercialization process of silicon-based anode materials and are suitable for large-scale industrial production.

[0148] The above-described embodiments are illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Those skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention are still intended to be included in the scope of the claims of the present invention.

Claims

1. an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix; The silicon-carbon composite material has a thermal decomposition weight loss of 5% to 60% when heated to 1400°C in an air atmosphere; A silicon-carbon composite material that satisfies the following relationship: B=B Ａ / B ａ (The value range of B is 20 to 1250. B is the specific surface area coefficient of the silicon-carbon composite material, and B Ａ is the specific surface area of ​​the amorphous carbon matrix, ranging from 500 m 2 / g to 2500 m 2 / g. ａ is the specific surface area of ​​the silicon-carbon composite material, which ranges from 2 m 2 / g to 25 m 2 / g. Pv=Pv1 / Pv2 (P v represents the pore volume coefficient of the silicon-carbon composite material, and is in the range of 0.4 to 120. P v1 represents the pore volume diameter of the amorphous carbon matrix, and is in the range of 0.2 cm 3 / g to 0.9 cm 3 / g. P v2 represents the pore volume diameter of the silicon-carbon composite material, and is in the range of 0.005 cm 3 / g to 0.2 cm 3 / g.)

2. 2. The silicon-carbon composite material of claim 1, which satisfies the following conditions: The specific surface area coefficient B of the silicon-carbon composite material is in the range of 100-900.

3. 2. The silicon-carbon composite material of claim 1, which satisfies the following conditions: The pore volume coefficient P of the silicon-carbon composite material ｖ The range is 1 to 100.

4. 10. The silicon-carbon composite material of claim 1, further comprising nanometal particles attached to the surface and / or the interior of the amorphous carbon matrix.

5. 1. A method for producing a silicon-carbon composite material, comprising: synthesizing an amorphous carbon matrix material using a silicon source by chemical vapor deposition to obtain a silicon-carbon composite material, the silicon-carbon composite material comprises an amorphous carbon matrix and a silicon material located on and / or within the amorphous carbon matrix; The silicon-carbon composite material has a thermal decomposition weight loss of 5% to 60% when heated to 1400°C in an air atmosphere; The method for producing a silicon-carbon composite material, wherein the silicon-carbon composite material satisfies the following relationship: B=B Ａ / B ａ (The value range of B is 20 to 1250. B is the specific surface area coefficient of the silicon-carbon composite material, and B Ａ is the specific surface area of ​​the amorphous carbon matrix, ranging from 500 m 2 / g to 2500 m 2 / g. ａ is the specific surface area of ​​the silicon-carbon composite material, which ranges from 2 m 2 / g to 25 m 2 / g. Pv=Pv1 / Pv2 (P v represents the pore volume coefficient of the silicon-carbon composite material, and is in the range of 0.4 to 120. P v1 represents the pore volume diameter of the amorphous carbon matrix, and is in the range of 0.2 cm 3 / g to 0.9 cm 3 / g. P v2 represents the pore volume diameter of the silicon-carbon composite material, and is in the range of 0.005 cm 3 / g to 0.2 cm 3 / g.)

6. The method for producing a silicon-carbon composite material according to claim 5, which satisfies at least one of the following conditions (1) and (2): (1) The silicon source is at least one selected from the group consisting of monosilane, dimethyldichlorosilane, and trichloromethylsilane. (2) The amorphous carbon matrix material is at least one material selected from the group consisting of porous amorphous carbon and porous amorphous carbon-metal composites.

7. The battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, an electrochemical device, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including the silicon-carbon composite material according to any one of claims 1 to 4.

8. An electronic device comprising the electrochemical device according to claim 7.

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