Composite material, preparation method of composite material and battery

Abstract

The invention discloses a composite material, a preparation method of the composite material and a battery, the composite material comprises a silicon substrate and a coating layer coating the silicon substrate, the material of the coating layer comprises Cu, in the composite material, the mass of a silicon element accounts for 87%-98% of the total mass of the composite material, the mass of a copper element accounts for 1%-10% of the total mass of the composite material, and the mass of the copper element accounts for 1%-10% of the total mass of the composite material. The mass of the oxygen element accounts for 0.5%-3.5% of the total mass of the composite material, the composite material can be used for preparing an electrode of a battery, and the coulombic efficiency and the cycling stability of the battery can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, and particularly relates to a composite material, a preparation method of the composite material and a battery. BACKGROUND

[0002] With the rapid development of portable electronic devices, electric vehicles and energy systems, batteries as the core device of energy conversion are constantly updated and iterated. Batteries have been widely used in consumer electronics, advanced robotics, grid-scale energy storage, electric vehicles and other technical fields.

[0003] The electrode material is one of the key factors that determine the comprehensive performance of the battery. Silicon material is considered as one of the electrode materials with potential prospects due to its high specific capacity and abundant resources. However, the silicon material has the disadvantages of significant volume expansion and poor electrical conductivity, which leads to the structure pulverization of the electrode based on the silicon material, and the continuous rupture and regeneration of the solid electrolyte interface film formed on the surface of the electrode, and the poor interface stability, so that the comprehensive performance of the battery still needs to be further improved.

[0004] Therefore, how to provide a silicon-based material which can be used to prepare an electrode of a battery and can improve the electrochemical performance of the electrode is of great significance to the development of the battery. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a composite material, a preparation method of the composite material and a battery.

[0006] In a first aspect, the present application provides a composite material, which comprises a silicon substrate and a coating layer coated on the silicon substrate, and the material of the coating layer comprises Cu. In the composite material, the mass percentage of silicon element in the total mass of the composite material is 87% to 98%, the mass percentage of copper element in the total mass of the composite material is 1% to 10%, and the mass percentage of oxygen element in the total mass of the composite material is 0.5% to 3.5%.

[0007] In a second aspect, the present application provides a preparation method of a composite material, which comprises the following steps: mixing and reacting a silicon substrate, Fehling reagent and a reducing agent to form a coating layer on the surface of the silicon substrate, the material of the coating layer comprising Cu, to obtain a reaction product; and solid-liquid separating the reaction product, collecting the solid to obtain the composite material; The silicon substrate is the silicon substrate in the composite material as described in the first aspect.

[0008] In a third aspect, the application provides a battery, which comprises a positive electrode and a negative electrode, and the material of the positive electrode or the material of the negative electrode comprises the composite material as described in the first aspect or the composite material prepared by the method as described in the second aspect.

[0009] The application provides a composite material, a preparation method of the composite material and a battery, which have the following technical effects: In the composite material of the application, the Cu coating layer can construct an effective conductive network, thereby making up for the deficiency of the silicon matrix in the conductive performance, giving the composite material good conductive capacity, and based on the good toughness of Cu, Cu can be closely combined with the silicon matrix and provide reliable mechanical support, thereby improving the toughness of the composite material and improving the pulverization phenomenon caused by the expansion of the silicon matrix. In addition, the Cu coating layer can reduce the surface activity of the silicon matrix, so that the composite material has good oxidation resistance.

[0010] In the preparation method of the composite material of the application, the reducing agent and Cu in Fehling reagent 2+ react to generate cuprous oxide, and then the cuprous oxide is further reduced to metallic copper by the reducing agent, and the preparation method has the advantages of simple process, easy control of copper doping amount and high uniformity of Cu distribution in the prepared composite material.

[0011] In the battery of the application, the material of the electrode comprises the composite material or the composite material prepared by the preparation method, which is beneficial to improve the coulomb efficiency and cycle stability of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced as follows.

[0013] Figure 1 A flowchart of the preparation method of the composite material provided in the embodiments of the application is shown.

[0014] Figure 2 A charge-discharge curve of the lithium ion battery in application example 1 is shown. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Also, any method and material similar or equivalent to those described herein can be used in the practice of the present application. The methods and materials described herein are illustrative only and not intended to be limiting.

[0017] It is to be understood that the order of steps or description of steps in the embodiments described is not limited to the order presented but can be carried out in any order practical. Additionally, each of the embodiments of the present application can be implemented in a range of versions; it should be understood that the description of a range version is merely for the convenience and brevity and should not be construed as a limitation of the scope of the present application; therefore, it should be considered that the range description has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has been specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0018] In the description of the present application, the term "comprising" means "including but not limited to".

[0019] The term "plurality", "multiple" or similar expressions refers to two (times) or more than two (times), for example, can be two (times), three (times), four (times), five (times), six (times), etc.

[0020] The term "and / or" refers to the selection range of any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" includes three parallel schemes of A, B and A+B.

[0021] The term "inert gas" refers to a class of gases with stable chemical properties, which are not easy to react with other substances at normal temperature and pressure, including one or more of nitrogen, helium, neon, argon, krypton and xenon.

[0022] The term "D10 particle size" refers to the particle size value corresponding to the cumulative percentage of particle volume reaching 10% in the cumulative particle size distribution curve of the particle population.

[0023] The term "D50 particle size" refers to a particle size value corresponding to 50% of the cumulative volume percentage of particles in a cumulative particle size distribution curve of a particle population, also referred to as "volume median diameter". In other words, the particles are sorted by particle size from small to large, and when the total volume of all particles having a particle size not greater than a certain particle size accounts for 50% of the total volume of all particles, the particle size is the D50 particle size.

[0024] The term "D90 particle size" refers to a particle size value corresponding to 90% of the cumulative volume percentage of particles in a cumulative particle size distribution curve of a particle population.

[0025] The term "aliphatic chain hydrocarbon group" refers to an aliphatic straight chain hydrocarbon group or an aliphatic branched chain hydrocarbon group, and the aliphatic chain hydrocarbon group can contain an unsaturated bond or can not contain an unsaturated bond. The aliphatic chain hydrocarbon group is a group obtained by removing one hydrogen atom from an aliphatic chain hydrocarbon. The "C1-C10 aliphatic chain hydrocarbon group" can be a C1-C8 aliphatic chain hydrocarbon group, a C1-C7 aliphatic chain hydrocarbon group, a C1-C6 aliphatic chain hydrocarbon group, a C1-C5 aliphatic chain hydrocarbon group, a C1-C4 aliphatic chain hydrocarbon group, or a C1-C3 aliphatic chain hydrocarbon group. The C1-C10 aliphatic chain hydrocarbon group is, for example, a C1-C10 alkyl group, a C2-C10 alkenyl group, or a C2-C10 alkynyl group. Suitable examples of the "aliphatic chain hydrocarbon group" include, but are not limited to, methyl, ethyl, ethenyl, ethynyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, isobutyl, and the like.

[0026] The term "aliphatic chain hydrocarbon oxy group" refers to a group of the general formula -O-aliphatic chain hydrocarbon group, O represents an oxygen atom. The "C1-C10 aliphatic chain hydrocarbon oxy group" can be a C1-C8 aliphatic chain hydrocarbon oxy group, a C1-C7 aliphatic chain hydrocarbon oxy group, a C1-C6 aliphatic chain hydrocarbon oxy group, a C1-C5 aliphatic chain hydrocarbon oxy group, a C1-C4 aliphatic chain hydrocarbon oxy group, or a C1-C3 aliphatic chain hydrocarbon oxy group. Suitable examples of the aliphatic chain hydrocarbon oxy group include methoxy, ethoxy, t-butoxy, or n-hexyloxy.

[0027] In the present application, the method for measuring the specific surface area, pore volume, and pore size distribution of a material includes the steps of: degassing a sample of the material to be measured at 200°C in a vacuum environment (pressure of -0.1 MPa) for 10 hours; then, obtaining a nitrogen adsorption / desorption isotherm of the sample at a temperature of 77 K using a Micromeritcs Tristar 3030 instrument; and then, calculating the specific surface area using the Brunauer-Emmett-Teller method and the adsorption curve branch data in the range of relative pressure P / P0 of 0.005 to 1, and analyzing the pore volume and pore size distribution from the adsorption curve, and the model for analyzing the pore volume and pore size distribution is the Density Function Theory model.

[0028] The composite material provided by the embodiments of the present application includes a silicon substrate and a cladding layer cladded on the silicon substrate, and the material of the cladding layer includes copper (Cu). In the composite material, the mass percentage of silicon element in the total mass of the composite material is 87% to 98%, for example, 87%, 92%, 94%, 96%, 98%, or a range or value between any two of the foregoing values; the mass percentage of copper element in the total mass of the composite material is 1% to 10%, for example, 1%, 3%, 5%, 7%, 10%, or a range or value between any two of the foregoing values; and the mass percentage of oxygen element in the total mass of the composite material is 0.5% to 3.5%, for example, 0.5%, 1%, 2%, 3%, 3.5%, or a range or value between any two of the foregoing values.

[0029] In the composite material of the embodiments of the present application, the Cu cladding layer can construct an effective conductive network, thereby making up for the deficiency of the silicon substrate in the conductive performance, giving the composite material good conductive capacity, and based on the good toughness of Cu, Cu can be closely combined with the silicon substrate and provide reliable mechanical support, thereby improving the toughness of the composite material and improving the pulverization phenomenon caused by the expansion of the silicon substrate. In addition, the Cu cladding layer can reduce the surface activity of the silicon substrate, so that the composite material has good oxidation resistance.

[0030] In the composite material of the embodiments of the present application, the mass percentage of copper element in the total mass of the composite material is 1% to 10%, and the amount of copper doping is appropriate, which can further improve the capacity of the composite material. It can be understood that too much copper doping (for example, higher than 10%) will cause the overall capacity of the composite material to decrease, and too little copper doping (for example, less than 1%) will limit the improvement degree of the conductive capacity and toughness of the composite material.

[0031] It should be noted that the cladding layer can partially or completely cladding the silicon substrate, and the cladding degree of the cladding layer to the silicon substrate can be 80% to 100%, for example, 80%, 85%, 90%, 95%, 100%, or a range or value between any two of the foregoing values, wherein the cladding degree refers to the percentage of the surface area of the silicon substrate covered by the cladding layer in the total surface area of the silicon substrate.

[0032] In some embodiments of the present application, the composite material further includes Cu3Si, and at least part of the Cu3Si is distributed at the interface between the silicon substrate and the cladding layer, which can further improve the conductivity and toughness of the composite material, and further improve the close combination between the cladding layer and the silicon substrate.

[0033] In the composite material of the embodiments of the present application, the silicon substrate can be crystalline silicon or amorphous silicon according to the classification of crystal structure. The silicon substrate can be metallurgical silicon, electronic grade silicon or solar grade silicon according to the classification of preparation process. The silicon substrate can be porous silicon or bulk silicon according to the classification of morphology.

[0034] To further improve the electrochemical performance of the composite material, in some embodiments of the present application, the material of the silicon substrate comprises porous silicon. In this case, the D10 particle size of the porous silicon is 1.98 μm~ 2.62 μm, for example, it can be 2.00 μm, 2.10 μm, 2.20 μm, 2.30 μm, 2.40 μm, 2.50 μm, 2.60 μm or a range or value between any two of the foregoing. The D50 particle size of the porous silicon is 5.87 μm~7.21 μm, for example, it can be 5.87 μm, 6.00 μm, 6.30 μm, 6.80 μm, 7.20 μm or a range or value between any two of the foregoing. The D90 particle size of the porous silicon is 12.12 μm~13.99 μm, for example, it can be 12.12 μm, 12.50 μm, 13.00 μm, 13.50 μm, 13.90 μm or a range or value between any two of the foregoing. The specific surface area of the porous silicon is 98.8 m 2 / g ~123.5 m 2 / g, for example, it can be 98.8 m 2 / g, 100.0 m 2 / g, 110 m 2 / g, 123.5 m 2 / g or a range or value between any two of the foregoing. The porosity of the porous silicon is 60%~90%, for example, it can be 60%, 70%, 80%, 90% or a range or value between any two of the foregoing. The ratio of mesopore volume to total pore volume of the porous silicon is 5%~10%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10% or a range or value between any two of the foregoing. It should be noted that mesopore refers to pore structure with pore size of 2 nm~50 nm.

[0035] In some embodiments of the present application, the D10 particle size of the composite material is 2.06 μm to 2.98 μm, for example, it can be 2.10 μm, 2.30 μm, 2.50 μm, 2.70 μm, 2.98 μm, or a range or value between any two of the foregoing. The D50 particle size of the composite material is 6.01 μm to 7.50 μm, for example, it can be 6.05 μm, 6.30 μm, 6.50 μm, 6.80 μm, 7.00 μm, 7.50 μm, or a range or value between any two of the foregoing. The D90 particle size of the composite material is 12.90 μm to 14.66 μm, for example, it can be 12.95 μm, 13.20 μm, 13.50 μm, 13.80 μm, 14.20 μm, 14.66 μm, or a range or value between any two of the foregoing. The specific surface area of the composite material is 78.2 m 2 / g to 125 m 2 / g, for example, it can be 78.2 m 2 / g, 85.00 m 2 / g, 95.00 m 2 / g, 105.00 m 2 / g, 115.00 m 2 / g, 120 m 2 / g, 125 m 2 / g, or a range or value between any two of the foregoing.

[0036] The present application also provides a preparation method of a composite material, which can be used to prepare the composite material as described above, such as Figure 1 As shown in the figure, the preparation method of the composite material comprises the following steps: S1, mixing and reacting a silicon substrate, Fehling reagent and a reducing agent to form a coating layer on the surface of the silicon substrate, the material of the coating layer comprising Cu, to obtain a reaction product; S2, solid-liquid separation of the reaction product, collecting the solid to obtain a composite material.

[0037] Wherein, the silicon substrate and the coating layer are as described above.

[0038] In the above preparation method, the reducing agent reacts with Cu 2+ in the Fehling reagent to generate cuprous oxide, and then the cuprous oxide is further reduced to metallic copper by the reducing agent, and the preparation method has the advantages of simple process, easy control of copper doping amount, and high uniformity of Cu distribution in the prepared composite material.

[0039] It should be noted that compared with the silicon copper material prepared by mixing Cu and Si through mechanical grinding, the composite material prepared by the above preparation method has the advantages of appropriate copper doping amount and high Cu distribution uniformity, so that the composite material has higher capacity and stable electrochemical performance.

[0040] In step S1, the Fehling reagent is a liquid reagent prepared by mixing a copper salt, a base and a copper ion complexing agent in a solvent. The Fehling reagent is generally prepared on site.

[0041] In some embodiments of the present application, the preparation method of the Fehling reagent comprises the step of mixing equal volumes of a first solution containing a copper salt, a second solution containing a base and a third solution containing a copper ion complexing agent, wherein the solvents of the first solution, the second solution and the third solution independently comprise water, and the concentration of the base in the second solution is greater than the concentration of the copper ion in the first solution to ensure the stability of the basic environment and the copper complex.

[0042] It should be noted that the preparation method of the Fehling reagent can further comprise the step of mixing equal volumes of A liquid and B liquid, wherein the A liquid contains a copper salt, and the B liquid contains a base and a copper ion complexing agent.

[0043] In the Fehling reagent, the copper salt is soluble in water. In some embodiments of the present application, one or more of copper sulfate and copper halide are included, wherein the copper sulfate can be one or more of anhydrous copper sulfate and copper sulfate pentahydrate, and the copper halide includes one or more of copper chloride, copper bromide and copper iodide.

[0044] In some embodiments of the present application, the base includes one or more of sodium hydroxide and potassium hydroxide.

[0045] In some embodiments of the present application, the copper ion complexing agent includes one or more of sodium potassium tartrate, sodium citrate and disodium ethylenediaminetetraacetate.

[0046] In some embodiments of the present application, in the step of mixing and reacting the silicon substrate, the Fehling reagent and the reducing agent, the mass ratio between the silicon substrate and the copper salt used to prepare the Fehling reagent is 100:(2-30), for example, it can be 100:2, 100:5, 100:10, 100:15, 100:20, 100:25, 100:30 or a range or value between any two of the foregoing values. Under this condition, the content of Cu in the prepared composite material is in a more appropriate range, which can further improve the capacity of the prepared composite material. Taking anhydrous copper sulfate as an example, the mass ratio between the silicon substrate and the copper salt used to prepare the Fehling reagent is 100:(2.6-26.6).

[0047] In some embodiments of the present application, the concentration of copper ions in the first solution is 0.05 mol / L to 1 mol / L, the concentration of the base in the second solution is 1 mol / L to 5 mol / L, and the concentration of the copper ion complexing agent in the second solution is 1 mol / L to 3 mol / L.

[0048] In some embodiments of the present application, the compound containing an aldehyde group has a structure of R1-CHO, wherein R1 is selected from a C1-C10 aliphatic chain hydrocarbon group unsubstituted or substituted with at least one R0, a C1-C10 aliphatic chain hydrocarbonoxy group unsubstituted or substituted with at least one R0, or a combination thereof; R0 is independently selected at each occurrence from a hydroxyl group, an aldehyde group, a C1-C5 aliphatic chain hydrocarbon group, a C1-C5 aliphatic chain hydrocarbonoxy group, or a combination thereof.

[0049] In some embodiments of the present application, the compound containing an aldehyde group includes one or more of formaldehyde, acetaldehyde, and glucose.

[0050] In step S1, the amount of the reducing agent is in excess relative to the amount of the copper salt to gradually reduce the copper salt to form metallic copper. Taking the compound containing an aldehyde group including one or more of formaldehyde, acetaldehyde, and glucose, and the copper salt being copper sulfate as an example, in the step of mixing the silicon substrate, the Fehling reagent, and the reducing agent to react, the mass ratio between the copper salt used to prepare the Fehling reagent and the compound containing an aldehyde group is 1:(0.07-0.61), which can be 1:0.07, 1:0.10, 1:0.30, 1:0.50, 1:0.61, or a range or value between any two of the foregoing.

[0051] In some embodiments of the present application, the mixing reaction is performed at a temperature of 50-90 °C to further improve the efficiency and completeness of the reduction reaction, thereby further improving the purity of the reduced Cu. In order to further improve the uniformity of the Cu coating, in some embodiments of the present application, the mixing reaction is performed under the condition of a water bath.

[0052] In step S2, the solid-liquid separation can include one or more of filtration, sedimentation, membrane separation, and thermal evaporation. Among them, the filtration can be one or more of normal pressure filtration, suction filtration, and pressure filtration, the sedimentation can be one or more of gravity sedimentation and centrifugal separation, and the membrane separation can be one or more of microfiltration and ultrafiltration. It can be understood that the collected solid can be subjected to a washing and drying process to remove impurities.

[0053] In order to further improve the conductivity and toughness of the prepared composite material, and further improve the bonding tightness between the cladding layer and the silicon substrate, in some embodiments of the present application, the collected solid is an intermediate, the intermediate comprises a silicon substrate and a first layer cladding the silicon substrate, the material of the first layer comprises Cu, after the step of collecting the solid and before the step of obtaining the composite material, the method for preparing the composite material further comprises the step of: heat treating the intermediate, so that at least part of the Cu in the first layer in contact with the silicon substrate is converted into Cu3Si.

[0054] In some embodiments of the present application, the heat treatment is carried out in an atmosphere of inert gas, the temperature of the heat treatment is 700 ℃-900 ℃, and the time of the heat treatment is 0.5 h-2 h.

[0055] The embodiments of the present application provide a battery, the battery comprises a positive electrode and a negative electrode, the material of the positive electrode or the material of the negative electrode comprises the composite material as described in the foregoing or the composite material prepared by the method for preparing the composite material as described in the foregoing, and the battery has good performance.

[0056] Specifically, for the electrode whose material comprises the composite material as described in the foregoing or the composite material prepared by the method for preparing the composite material as described in the foregoing, first, based on the good toughness of the composite material, the electrode pulverization phenomenon caused by the expansion of the silicon substrate can be improved, thereby facilitating the improvement of the cycle performance of the battery; second, the Cu uniformly covers the surface of the silicon substrate, which can reduce the direct contact between the silicon substrate and the electrolyte, improve the continuous regeneration of the solid electrolyte interface (SEI) film, improve the electrochemical stability of the interface between the electrode and the electrolyte, and improve the oxidation resistance of the electrode, thereby improving the performance stability of the electrode, further improving the coulomb efficiency of the battery, and prolonging the service life of the battery; third, the copper doping amount of the composite material is appropriate, which improves the performance stability of the electrode while the battery has high capacity.

[0057] In addition, for the lithium ion battery, since the Cu is a lithium intercalation inert material, the lithium intercalation path of the electrode can be controlled, the expansion of the silicon substrate starts from the inside of the hole, which can fully utilize the void space, and further improve the anti-expansion property of the electrode.

[0058] Furthermore, when the composite material also includes Cu3Si, it can significantly improve the conductivity of the electrode. Since Cu3Si exists at the interface between the silicon substrate and the coating layer, Cu3Si acts as a conductive framework, further improving the toughness of the electrode. This further suppresses the pulverization phenomenon caused by the expansion of the silicon substrate during cycling. In addition, Cu3Si acts as a connector between the silicon substrate and the coating layer, improving the bonding tightness between the silicon substrate and the coating layer, and further improving the performance stability of the electrode.

[0059] Based on its geometric shape, the battery in this application embodiment can be a square battery, a cylindrical battery, a button battery, or an irregularly shaped battery. Based on its packaging form, the battery in this application embodiment can be a pouch battery or a hard-case battery. Based on its assembly form, the battery in this application embodiment can be a battery cell, a battery module, or a battery pack. Based on its operating nature and storage method, the battery in this application embodiment can be a primary battery, a secondary battery, or an activated battery. Based on the type of current-carrying ions in the battery, the battery in this application embodiment can be a lithium-ion battery or a sodium-ion battery.

[0060] In the battery of this application embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. It is understood that the positive electrode current collector includes a first surface and a second surface disposed opposite to each other along its own thickness direction, and at least one of the first surface and the second surface is provided with a positive electrode active material layer.

[0061] The positive electrode current collector is made of metal foil or a composite current collector. The metal foil includes aluminum foil, platinum foil, or palladium foil. The composite current collector includes a substrate and a metal layer. The substrate includes a third surface and a fourth surface disposed opposite each other along its thickness direction. At least one of the third and fourth surfaces has a metal layer. The substrate is made of one or more of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene. The metal layer is made of one or more of aluminum, platinum, palladium, nickel, titanium, and silver. The positive electrode active material layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

[0062] In some embodiments of this application, the battery is a lithium-ion battery, and the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium permanganate, lithium iron phosphate, lithium nickel oxide, lithium manganese phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0063] In other embodiments of this application, the battery is a sodium-ion battery, and the positive electrode active material includes one or more of metal oxides, Prussian compounds, and polyanionic compounds. The chemical formula of the metal oxide is Na. xMO2, where M is a transition metal element, including one or more of Mn, Ni, Cr, Fe, Ti, and V. Suitable examples include Na(Li). 1 / 3 Ti 1 / 6 Mn 1 / 2 O2, NaFeO2 and Na 2 / 3 Ni 1 / 3 Mn 1 / 2 Ti 1 / 6 One or more of O2; the chemical formula of Prussian compounds is Na. x M a (M b (CN)6), M a Including one or more of Fe, Mn, and Ni, M b Suitable examples of Prussian compounds include one or more of Fe and Mn, including Na. x Mn(Fe(CN)6); the chemical formula of the polyanionic compound is Na x A y ((XO m ) n ) z A is a metallic element with a variable valence state, including one or more of Fe and V, X is one or more of P and S, and suitable examples of polyanionic compounds include one or more of Na3V2(PO4)3, NaFePO4, Na2Fe2(SO4)3 and Na4Mn(SO4)2.

[0064] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0065] Positive conductive agents include one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0066] The preparation method of the positive electrode may include the following steps: mixing and dispersing a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder in a first dispersion medium to form a positive electrode slurry; then, coating the positive electrode slurry onto a positive electrode current collector, followed by a drying process and a rolling process to obtain the positive electrode. It should be noted that the positive electrode slurry can also be cast onto a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the first surface and / or the second surface of the positive electrode current collector. The first dispersion medium includes one or more of N-methylpyrrolidone, acetone, and water.

[0067] In the battery of this application embodiment, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. It is understood that the negative electrode current collector includes a fifth surface and a sixth surface disposed opposite to each other along its own thickness direction, and at least one of the fifth surface and the sixth surface is provided with a negative electrode active material layer.

[0068] The negative electrode current collector is made of copper foil, composite copper foil, or copper mesh. The negative electrode active material layer is made of negative electrode active material, negative electrode binder, and negative electrode conductive agent.

[0069] In some embodiments of this application, the negative electrode active material includes the composite material as described above, or the composite material prepared by the method described above.

[0070] The negative electrode binder includes one or more of the following: lithium polyacrylate, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0071] Negative electrode conductive agents include one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0072] The preparation method of the negative electrode may include the following steps: mixing and dispersing the negative electrode active material, negative electrode conductive agent, and negative electrode binder in a second dispersion medium to form a negative electrode slurry; then, coating the negative electrode slurry onto a negative electrode current collector, followed by a drying process and a rolling process to obtain the negative electrode. It should be noted that the negative electrode slurry can also be cast on a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the fifth and / or sixth surfaces of the negative electrode current collector. The second dispersion medium includes one or more of N-methylpyrrolidone, acetone, and water.

[0073] It is understood that the battery in this application embodiment may also include other conventional structures. For example, the battery in this application embodiment may also include a separator disposed between the positive and negative electrodes. The separator may be a single-layer thin film or a composite membrane with a multi-layer structure. When the separator is a composite membrane, the material of each layer in the composite membrane may be the same or different. The material of the separator includes one or more of glass fiber, non-woven fabric, polyester, Teflon, polyethylene, polypropylene, ceramic, and polytetrafluoroethylene.

[0074] The battery in this application embodiment further includes an electrolyte or a solid electrolyte. The electrolyte can be a conventional electrolyte in the art, comprising a metal salt and an organic solvent. The organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, 1,4-butyrolactone, ethylene carbonate, propylene carbonate, propylene sulfite, propyl acetate, propyl propionate, methyl butyrate, butyl acetate, ethyl propionate, ethyl butyrate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0075] When the battery is a lithium-ion battery, the metal salt includes lithium salts, including LiPF6, LiClO4, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiODFB, LiTFSI, LiFSI, LiCl, LiI, and LiN(C x F 2x+1 SO2)(C y F 2y+1 One or more of SO2, wherein x and y are integers from 1 to 20.

[0076] When the battery is a sodium-ion battery, the metal salt includes sodium salts, which include one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium 4,5-dicyano-2-trifluoromethylimidazolium, sodium 4,5-dicyano-2-pentafluoromethylimidazolium, and sodium fluorosulfonyl (perfluorobutylsulfonyl)imide.

[0077] It should be noted that the positive electrode, negative electrode, and separator can be formed into a battery cell through a winding or stacking process. The electrolyte wets the positive and negative electrodes, and packaging one or more battery cells yields a single battery cell. The battery cell can be packaged using a rigid shell or a pouch. The rigid shell includes a metal shell or a plastic shell with high hardness, while the pouch material includes one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0078] Battery cells can be assembled to form a battery module. Each battery module includes multiple battery cells arranged sequentially along a first direction and secured with fasteners. The first direction can be the length, width, or height of the battery module. It is understood that the battery module also has a housing for accommodating the multiple battery cells.

[0079] Battery modules can be assembled to form a battery pack, with each battery pack containing multiple battery modules. The battery pack also includes a housing for accommodating the multiple battery modules, which can be arranged sequentially along the length or width of the housing. Understandably, the battery pack also includes some conventional components, including a battery management system, buffers, and cooling devices.

[0080] This application also provides an application of the aforementioned battery in electronic devices, electric vehicles, and energy storage systems. The electronic devices, electric vehicles, and energy storage systems respectively employ the aforementioned battery as a power source and / or energy storage component. The electronic devices include mobile phones, computers, digital cameras, camcorders, video game consoles, smart wearable devices, drones, Bluetooth speakers, wireless headphones, security equipment, medical equipment, and aerospace equipment. The electric vehicles include electric cars, electric motorcycles, electric bicycles, electric scooters, and electric balance scooters. The energy storage systems include home energy storage systems, solar energy storage systems, wind energy storage systems, and grid-connected energy storage power stations.

[0081] The technical solutions and effects of this application will be described in detail below through specific embodiments and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application in any specific way.

[0082] Material Example 1 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​porous silicon with a specific surface area of ​​112.1 m². 2 The porous silicon has a porosity of 86% and a mesopore volume accounting for 6% of the total pore volume. The D10 particle size is 2.4 μm, the D50 particle size is 6.5 μm, and the D90 particle size is 13.8 μm.

[0083] The method for preparing the composite material in this embodiment includes the following steps S1.1 to S1.3.

[0084] In step S1.1, 60 g of porous silica is added to Fehling's reagent and stirred to obtain a mixture. 10 mL of a 10% (mass percentage) formaldehyde aqueous solution is added to the mixture in two portions, 5 mL each time, with a 30 s interval between each addition. The mixture is then stirred to obtain the reaction mixture. The method includes the following steps: dissolving copper sulfate in deionized water to prepare a first solution with a copper sulfate concentration of 1 mol / L; dissolving NaOH in deionized water to prepare a second solution with a NaOH concentration of 2 mol / L; and dissolving potassium sodium tartrate in deionized water to prepare a third solution with a potassium sodium tartrate concentration of 1 mol / L. 56 mL of the first solution, 56 mL of the second solution, and 56 mL of the third solution are mixed to obtain Fehling's reagent. Fehling's reagent should be prepared and used immediately.

[0085] In step S1.2, the container holding the reaction system is placed in a water bath at 70 °C for heat treatment. During the heat treatment, a red precipitate (cuprous oxide) is first observed to appear in the reaction system. The red precipitate gradually turns into a brick-red precipitate. Finally, heating is stopped when a dark red, metallic-lustered copper mirror forms on the inner wall of the container, and the reaction product is obtained. The reaction product is filtered, the filter cake is collected, washed with ethanol, and then dried to obtain the intermediate.

[0086] In step S1.3, the intermediate is placed in a tube furnace and kept at 860 °C for 1 h under the protective atmosphere of argon. After cooling to room temperature, the material is sieved to obtain the composite material.

[0087] Material Example 2 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​the same as that in Material Example 1.

[0088] Compared to the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that: Fehling's reagent is prepared by mixing 100 mL of 0.1 mol / L copper sulfate aqueous solution, 100 mL of the second solution, and 100 mL of the third solution. The second solution is the same as the second solution in Material Example 1, and the third solution is the same as the third solution in Material Example 1.

[0089] Material Example 3 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​the same as that in Material Example 1.

[0090] Compared to the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that: Fehling's reagent is prepared by mixing 100 mL of a first solution, 100 mL of a second solution, and 100 mL of a third solution. The first solution is the same as the first solution in Material Example 1, the second solution is the same as the second solution in Material Example 1, and the third solution is the same as the third solution in Material Example 1.

[0091] Material Example 4 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​the same as that in Material Example 1.

[0092] Compared to the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that the step S1.1, "adding 10 mL of 10% (mass percentage) formaldehyde aqueous solution to the mixture in two portions, each time adding 5 mL of formaldehyde aqueous solution, with an interval of 30 s between adjacent additions", is replaced with "adding 3 mL of 10% (mass percentage) formaldehyde aqueous solution to the mixture in two portions, each time adding 1.5 mL of formaldehyde aqueous solution, with an interval of 30 s between adjacent additions".

[0093] Material Example 5 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​the same as that in Material Example 1.

[0094] Compared with the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that the step S1.3 "holding the intermediate at 860 ℃ for 1 h" is replaced with "holding the intermediate at 860 ℃ for 0.5 h".

[0095] Material Example 6 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​the same as that in Material Example 1.

[0096] Compared with the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that the step S1.3 "keeping the intermediate at 860 ℃ for 1 h" is replaced with "keeping the intermediate at 860 ℃ for 2 h".

[0097] Material Example 7 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu, and the composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer. The silicon matrix is ​​porous silicon with a specific surface area of ​​99.8 m². 2 The porous silicon has a porosity of 75% and a mesopore volume accounting for 6.3% of the total pore volume. The D10 particle size is 2.44 μm, the D50 particle size is 6.7 μm, and the D90 particle size is 13.6 μm.

[0098] Compared with the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that the silicon matrix in step S1.1 is replaced with the silicon matrix of this example.

[0099] Material Example 8 This embodiment provides a composite material and its preparation method. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The material of the coating layer includes Cu. The silicon matrix is ​​the same as that in Material Example 1.

[0100] Compared with the preparation method of the composite material in Material Example 1, the difference in the preparation method of the composite material in this example is that step S1.3 is omitted, and the intermediate obtained in step S1.2 is screened. The material obtained after screening is the composite material of this example.

[0101] Material Example 9 This embodiment provides a composite material and a method for preparing the same. The composite material includes a silicon matrix and a coating layer covering the silicon matrix. The coating layer is made of Cu. The composite material also includes Cu3Si, with at least a portion of the Cu3Si distributed at the interface between the silicon matrix and the coating layer.

[0102] Compared with the preparation method of the composite material in Material Example 1, the preparation method of the composite material in this example is different in that: step S1.1 is replaced by "taking 60 g of porous silica and adding it to Fehling's reagent (the same as Fehling's reagent in Material Example 1), stirring and mixing to obtain a mixture, adding 10 mL of 10% (mass percentage) glucose aqueous solution to the mixture in two portions, each time adding 5 mL of glucose aqueous solution, with an interval of 30 s between adjacent additions, mixing to obtain a reaction system", and step S1.2 is replaced by "placing the container containing the reaction system in a 70 ℃ water bath for 5 min, then adding 5 mL of 10% formaldehyde aqueous solution, and continuing to heat-treat in a 70 ℃ water bath until a dark red, metallic copper mirror is formed on the inner wall of the container, and the reaction product is obtained".

[0103] Material Comparison Example 1 This comparative example provides a composite material and its preparation method. The composite material includes a silicon matrix and Cu, with a mass ratio of silicon matrix to Cu of 1:0.1. The silicon matrix is ​​the same as that in Material Example 1.

[0104] The preparation method of the composite material in this comparative example includes the following steps: 100 g of pure silicon powder and 10 g of pure copper powder are placed in a ball mill jar with an argon gas atmosphere, and then ball milled for 10 h at a speed of 350 r / min to obtain the ball milling product; the ball milling media in the ball milling product are removed by using a sieve to obtain the composite material.

[0105] Material Comparison Example 2 This comparative example provides a composite material and its preparation method. The composite material includes a silicon matrix, Cu, and Cu3Si.

[0106] Compared with the preparation method of the composite material in Comparative Example 1, the preparation method of the composite material in this comparative example includes the following steps: placing the composite material obtained in Comparative Example 1 in a tube furnace, keeping the intermediate at 860 °C for 1 h under the protective atmosphere of argon, cooling to room temperature, and then sieving the material to obtain the composite material of this comparative example.

[0107] Material Comparison Example 3 This comparative example provides a silicon material, which is the silicon matrix in Material Example 1.

[0108] Application Example 1 This embodiment provides a lithium-ion battery and its preparation method. The lithium-ion battery in this embodiment is a CR2032 button cell. It uses a lithium metal sheet as the counter electrode, a glass fiber membrane (Whatman GF / D type) as the separator, and a 1 mol / L LiPF6 solution as the electrolyte. The LiPF6 solution is prepared by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 1:1:1. The working electrode includes an electrode current collector and an electrode active material layer disposed on the surface of the electrode current collector. The electrode current collector is an aluminum foil (9 μm thick). The electrode active material layer includes an electrode active substance, an electrode binder, and an electrode conductive agent. The electrode active substance is the composite material in Material Example 1. The electrode binder is styrene-butadiene rubber and carboxymethyl cellulose. The electrode conductive agent is conductive carbon black Super-P.

[0109] The preparation method of the working electrode includes the following steps: First, the composite material in Material Example 1 is mixed in a mass ratio of 94.5:2.5:1.5:1.5 of styrene-butadiene rubber:carboxymethyl cellulose:conductive carbon black. Then, ultrapure water is added and stirred evenly to form a slurry. Next, the slurry is coated on the surface of aluminum foil. Then, the aluminum foil coated with slurry is placed in a vacuum drying oven and dried at 90 °C for 24 h. After being pressed by a 5T roller, it is pressed into a circular electrode sheet with a diameter of 12 mm by a tablet press to obtain the working electrode.

[0110] The lithium-ion battery in this embodiment is assembled in a glove box, the gas atmosphere inside the glove box includes argon, and the total content of water and oxygen inside the glove box is less than 0.01 ppm.

[0111] Application Examples 2-9 The lithium-ion battery in application example m is basically the same as the lithium-ion battery in application example 1, except that in application example m, the electrode active material is the composite material in material example m, and m is a positive integer from 2 to 9.

[0112] Taking Application Example 2 as an example, the difference between the lithium-ion battery in Application Example 1 and the lithium-ion battery in Application Example 2 is that the electrode active material in the lithium-ion battery is the composite material from Material Example 2. Similarly, the difference between the lithium-ion battery in Application Example 9 and the lithium-ion battery in Application Example 1 is that the electrode active material in Application Example 9 is the composite material from Material Example 9.

[0113] Application Comparative Example 1 This comparative example provides a lithium-ion battery. Compared with the lithium-ion battery in Application Example 1, the difference of the lithium-ion battery in this comparative example is that the electrode active material in the lithium-ion battery is the composite material in Material Comparative Example 1.

[0114] Application Comparative Example 2 This comparative example provides a lithium-ion battery. Compared with the lithium-ion battery in Application Example 1, the difference of the lithium-ion battery in this comparative example is that the electrode active material in the lithium-ion battery is the composite material in Material Comparative Example 2.

[0115] Application Comparative Example 3 This comparative example provides a lithium-ion battery. Compared with the lithium-ion battery in Application Example 1, the difference in this comparative example is that the electrode active material in the lithium-ion battery is the silicon material in Material Comparative Example 3.

[0116] Performance Test 1 The composite materials in Material Examples 1 to 9, Material Comparative Example 1 and Material Comparative Example 2 were subjected to performance tests. The performance test items included element content, D10 particle size, D50 particle size, D90 particle size and specific surface area.

[0117] The XRF method was used to detect the elemental content, including the following steps: 2±0.05 g of stearic acid and 6±0.5 g of the negative electrode material sample to be tested were mixed and ground, then pressed into a tablet, and then tested in an Avio™200 device at a test pressure greater than 2 MPa.

[0118] The particle size was determined according to the method described in GB-T-19077-2024. The instrument used was a Malvern Panaco Zetasizer Ultra dynamic scattering particle size analyzer.

[0119] The test results are shown in Table 1 below: Table 1

[0120] As shown in Table 1, the composite materials of Materials Examples 1 to 9 have a silicon content of 87.02%–96.29%, a copper content of 1.31%–9.88%, a D10 particle size of 2.06 μm–2.98 μm, a D50 particle size of 6.01 μm–7.50 μm, a D90 particle size of 12.90 μm–14.66 μm, and a specific surface area of ​​98.8 m². 2 / g~123.5 m 2 / g.

[0121] Compared to the composite materials in Material Comparative Example 1 and Material Comparative Example 2, the composite materials in Material Examples 1 to 9 have less copper content, which is beneficial to further improve the capacity of the composite materials.

[0122] Performance Test 2 The performance of the lithium-ion batteries in Application Examples 1 to 9 and Application Comparative Examples 1 to 3 was tested respectively.

[0123] The method for detecting the initial coulombic efficiency and specific capacity includes the following steps: Under a constant temperature environment of 25 ℃, a blue-electric testing device is used for testing. The battery is charged and discharged at a current density of 0.1C (1C=300 mA / g), and the charge-discharge cycle is repeated twice within a voltage range of 0.01 V to 2.00 V. During the test, the initial charge specific capacity and initial discharge specific capacity of each lithium-ion battery are obtained, as well as the second discharge specific capacity. The initial coulombic efficiency (ICE, %) of each lithium-ion battery is calculated as: Initial Coulombic Efficiency (ICE, %) = Initial Discharge Specific Capacity / Initial Charge Specific Capacity × 100%. During the testing process, charge-discharge curves of each lithium-ion battery are obtained. Figure 2 The charge-discharge curves of the lithium-ion battery in Application Example 1 are shown.

[0124] The test results are shown in Table 2 below: Table 2

[0125] As shown in Table 2, compared to the lithium-ion batteries in Comparative Examples 1 to 3, the lithium-ion batteries in Application Examples 1 to 9 have higher ICE (Internal Capacity) and higher specific capacity. Specifically, the lithium-ion batteries in Application Examples 1 to 9 have an ICE of 86.21% to 92.01% and a specific capacity of 2886 mAh / g to 2972 ​​mAh / g, while the lithium-ion batteries in Comparative Examples 1 to 3 all have an ICE below 84% and a specific capacity below 2500 mAh / g.

[0126] Therefore, it can be seen that using the composite material of this application to prepare the electrode for a lithium-ion battery can reduce the direct contact between the silicon substrate and the electrolyte, improve the phenomenon of continuous SEI regeneration, enhance the electrochemical stability of the interface between the electrode and the electrolyte, and improve the oxidation resistance of the electrode, thereby improving the performance stability of the electrode, which in turn improves the coulombic efficiency of the lithium-ion battery and extends its service life. Furthermore, due to the appropriate copper doping content of the composite material, while improving the performance stability of the electrode, the lithium-ion battery also exhibits a high capacity.

[0127] The lithium-ion batteries in Comparative Example 1 and Comparative Example 2 showed poor overall performance because: firstly, the high copper content in the composite material led to a significant decrease in capacity; secondly, the composite material was prepared by mechanical grinding, which resulted in uneven copper distribution and poor electrode performance stability.

[0128] The lithium-ion battery in Comparative Example 3 exhibited poor overall performance due to the following reasons: Firstly, the silicon substrate has a large number of active sites, and the direct contact between the silicon substrate and the electrolyte increases the probability of side reactions. Secondly, the silicon substrate has poor conductivity and exhibits volume expansion.

[0129] The foregoing has provided a detailed description of a composite material, a method for preparing the composite material, and a battery provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the technical solutions and core ideas of this application; those skilled in the art should understand that modifications can still be made to the technical solutions described in each of the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A composite material, characterized by, The composite material comprises a silicon substrate and a coating layer coated on the silicon substrate, and a material of the coating layer comprises Cu; In the composite material, a mass percentage of silicon element in a total mass of the composite material is 87% to 98%, a mass percentage of copper element in the total mass of the composite material is 1% to 10%, and a mass percentage of oxygen element in the total mass of the composite material is 0.5% to 3.5%.

2. The composite material of claim 1, wherein, The composite material further comprises Cu3Si, and at least part of the Cu3Si is distributed at an interface between the silicon substrate and the coating layer.

3. The composite material of claim 1, wherein, The silicon substrate comprises porous silicon; The porous silicon has a D10 particle size of 1.98 μm to 2.62 μm, a D50 particle size of 5.87 μm to 7.21 μm, and a D90 particle size of 12.12 μm to 13.99 μm; The specific surface area of the porous silicon is 98.8 m 2 / g ~123.5 m 2 / g, the porosity is 60%~90%, and the ratio of mesopore volume to total pore volume is 5%~10%.

4. The composite material of claim 1, wherein, The composite material has a D10 particle size of 2.06 μm to 2.98 μm, a D50 particle size of 6.01 μm to 7.50 μm, and a D90 particle size of 12.90 μm to 14.66 μm; The specific surface area of the composite material is 78.2 m 2 / g ~125 m 2 / g.

5. A method of producing a composite material, characterized by, The method comprises the following steps: mixing a silicon substrate, Fehling reagent and a reducing agent to form a coating layer on a surface of the silicon substrate, wherein a material of the coating layer comprises Cu, and obtain a reaction product; and solid-liquid separation of the reaction product, collection of a solid, and obtaining the composite material; The silicon substrate is the silicon substrate in the composite material as claimed in any one of claims 1 to 4.

6. The method of claim 5, wherein the composite material is prepared by a process comprising: The collected solid is an intermediate, which comprises the silicon substrate and a first layer coated on the silicon substrate, and a material of the first layer comprises Cu. After the step of collecting the solid and before the step of obtaining the composite material, the method for preparing the composite material further comprises a step of heat treating the intermediate to convert at least part of Cu in the first layer, which is in contact with the silicon substrate, into Cu3Si. Optionally, the heat treatment is performed in an atmosphere of inert gas, the temperature of the heat treatment is 700 ℃ to 900 ℃, and the time of the heat treatment is 0.5 h to 2 h.

7. The method of claim 5, wherein the composite material is prepared by a process comprising: The method for preparing the Fehling reagent comprises the following steps: mixing a first solution comprising a copper salt, a second solution comprising a base, and a third solution comprising a copper ion complexing agent in equal volumes, wherein solvents of the first solution, the second solution and the third solution independently comprise water, and a concentration of the base in the second solution is greater than a concentration of copper ions in the first solution; optionally, the copper salt comprises one or more of copper sulfate and copper halide, the base comprises one or more of sodium hydroxide and potassium hydroxide, and the copper ion complexing agent comprises one or more of potassium sodium tartrate, sodium citrate and disodium ethylenediaminetetraacetate; And / or, the mixing reaction is performed at a temperature of 50 ℃ to 90 ℃.

8. The method of claim 7, wherein the composite material is prepared by a process comprising: In the step of mixing and reacting the silicon substrate, the Fehling reagent and the reducing agent, the mass ratio between the silicon substrate and the copper salt used for preparing the Fehling reagent is 100:(2-30); optionally, the copper salt is copper sulfate, and the mass ratio between the silicon substrate and the copper salt used for preparing the Fehling reagent is 100:(2.6-26.6). And / or, the concentration of the copper ions in the first solution is 0.05-1 mol / L, the concentration of the base in the second solution is 1-5 mol / L, and the concentration of the copper ion complexing agent in the second solution is 1-3 mol / L.

9. The method of claim 5, wherein the composite material is prepared by a process comprising: The compound containing an aldehyde group has a structure general formula of R1-CHO, wherein R1 is selected from a C1-C10 aliphatic chain hydrocarbon group unsubstituted or substituted with at least one R0, a C1-C10 aliphatic chain hydrocarbonoxy group unsubstituted or substituted with at least one R0, or a combination of the foregoing groups; R0 is independently selected at each occurrence from a hydroxyl group, an aldehyde group, a C1-C5 aliphatic chain hydrocarbon group, a C1-C5 aliphatic chain hydrocarbonoxy group, or a combination of the foregoing groups; Optionally, the compound containing an aldehyde group includes one or more of formaldehyde, acetaldehyde and glucose, and the copper salt is copper sulfate, and in the step of mixing and reacting the silicon substrate, the Fehling reagent and the reducing agent, the mass ratio between the copper salt used for preparing the Fehling reagent and the compound containing an aldehyde group is 1:(0.07-0.61).

10. A battery, characterized by The battery comprises a positive electrode and a negative electrode, and the material of the positive electrode or the material of the negative electrode comprises the composite material as claimed in any one of claims 1-4 or the composite material prepared by the method as claimed in any one of claims 5-9.

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