3991 results about "Carbon composites" patented technology

The invention relates to a method for preparing a lithium iron phosphate / carbon composite material of a lithium ion battery, which belongs to the technical field of lithium ion batteries. The method for preparing the lithium iron phosphate / carbon composite material of the lithium ion battery comprises the following steps of: 1) preparing a suspending graphene-dispersed aqueous solution system, namely, crushing graphite to 1 to 5 microns, adding the crushed graphite into distilled water or purified water, adding 0.1 to 5 percent of surfactant, heating with stirring the mixed solution to 180 to 250 DEG C in a sealing way, performing stirring for 2 to 6 hours and reducing the temperature; 2) crushing lithium iron phosphate to the particle size of 1 to 5 microns, adding the crushed lithium iron phosphate into the distilled water or the purified water, adding with stirring 0.01 to 1 percent of coupling agent, performing uniform stirring, adding the graphene-dispersed aqueous solution, and performing stirring and filtration; and 3) vacuum-drying solid powder obtained by the filtration, and calcinating the dried solid powder for 2 to 12 hours to obtain the graphene-coated lithium iron phosphate cathode material. The method has the advantages of simple process, high material performance, high conductivity, high bulk density, high compacted density and the like.

The invention relates to the field of lithium battery negative electrode materials, and particularly discloses a silicon-carbon composite negative electrode material for a lithium ion battery and a preparation method of the silicon-carbon composite negative electrode material. The method comprises the following steps: preparing a porous carbon substrate, and depositing silicon nanoparticles in pores and on the surface of the porous carbon substrate by adopting a fluidized bed chemical vapor deposition process and taking silane as a silicon source to obtain a silicon-carbon core material; continuously carrying out carbon coating on the surface of the silicon-carbon core material in the fluidized bed by taking acetylene as a carbon source to form a carbon coating layer; and leading out the obtained material from the fluidized bed, taking acetylene as a carbon source, and carrying out carbon coating on the surface of the primary carbon coating layer again by adopting the rotary furnace to form a secondary carbon coating layer. According to the preparation method, a porous carbon matrix and double-layer functional carbon coating process is adopted, so that the volume expansion of silicon in the circulation process is remarkably inhibited, the interface side reaction is reduced, and the circulation stability of the material is effectively improved.

The invention provides a high-rate and high-first-effect biomass hard carbon composite negative electrode material and a preparation method and application thereof, the hard carbon composite negative electrode material has a core-shell structure, the core-shell structure comprises a core, an inner shell and an outer shell, the core comprises biomass hard carbon containing P and graphite microcrystals, the inner shell comprises graphene, and the outer shell comprises a carbon nanotube. According to the invention, the surface of the biomass hard carbon is coated with the graphene layer, the carbon nanotubes grow on the surface of the graphene in situ, and transition metal synergistically induces the hard carbon to be arranged and grow along the graphene layer in a high-temperature carbonization process, so that the graphene coating layer is tightly coated, and the cycle performance of the material is improved; transition metal ions catalyze graphitization to generate a more regular and ordered graphite-like layer microcrystalline structure coating layer, so that the defects of graphene and carbon nanotubes are reduced, and the first coulombic efficiency is improved; in addition, the ion transmission capability is improved by phosphorus doping, the electron transmission capability is improved by graphite microcrystals generated by catalysis in hard carbon, and the rate capability is ensured by synergistic improvement of ion transmission and electron transmission.

The invention discloses a carbon composite ceramic linear resistor and a preparation method thereof, and belongs to the technical field of power electronic components. The invention provides a preparation method of a carbon composite ceramic linear resistor, which comprises the following steps: uniformly mixing bentonite, silicon carbide and nano carbon black to obtain powder, uniformly mixing the powder and ethanol, drying, adding a binder solution, and carrying out green body forming to obtain a green body; carrying out heat preservation on the green body at 1150-1300 DEG C in a nitrogen-containing gas atmosphere to obtain a sample; and polishing the sample, and spraying aluminum to obtain the carbon composite ceramic linear resistor. According to the method for preparing the carbon composite ceramic linear resistor, the resistivity of the material can be reduced, and the thermal shock resistance of the ceramic resistor can be improved.

The invention discloses a silicon-carbon negative electrode material, porous carbon and a preparation method, the porous carbon is prepared by mixing ammonium fluoride and a pre-carbonized material to prepare a premix; and putting the premix in an inert atmosphere, and carrying out pre-activation, drying, carbonization, activation and crushing treatment to obtain the composite material. And uniformly depositing the nano silicon particles into the porous carbon skeleton through a mature CVD (Chemical Vapor Deposition) process to obtain the silicon-carbon composite material. Fluorine and nitrogen co-doping modification can increase the defect degree of a carbon skeleton, efficiently relieve mechanical stress accompanied by lithium storage volume expansion of the silicon negative electrode in a micro scale, provide abundant lithium ion transport and mass transfer channels and enhance the conductivity of porous carbon, and ammonium fluoride is used as a supplementary activator besides water vapor, so that the porosity of the porous carbon is further improved, and the conductivity of the porous carbon is improved. An effective space is provided for uniform deposition of silicon, the fluorine-containing carbon layer can induce formation of a high-stability SEI film rich in LiF on the surface of the nano silicon material, and the interface stability and coulombic efficiency of the silicon negative electrode are further improved.

A graphite composite material and a preparation method therefor, a negative electrode active material, a secondary battery, and an electric device. The graphite composite material comprises an inner core and a coating layer located on the surface of the inner core, wherein the material of the inner core comprises graphite, and the material of the coating layer comprises a nitrogen-doped porous aluminum oxide-carbon composite material. The provided graphite composite material improves the initial efficiency of the graphite material, and improves the rate capability of a battery.

The invention relates to a silicon-carbon composite material and a preparation method and application thereof.The preparation method comprises the steps that a porous graphite raw material is subjected to acid pickling and smashing to obtain pretreated porous graphite, then the pretreated porous graphite is soaked in a carbon precursor solution in a vacuum mode, carbonization treatment is conducted after centrifugal separation, pores of the porous graphite are filled with carbides, physical activation is conducted, and the silicon-carbon composite material is obtained; the preparation method comprises the following steps: forming pores in a carbide to form a graded pore structure to obtain a porous graphite composite material, then carrying out silicon deposition in a fluidized bed to obtain a uniform nano silicon layer, and then carrying out carbon coating treatment to obtain a silicon-carbon composite material; the graphite with relatively low cost is adopted as a matrix, high capacity and long cycle performance of the graphite-based silicon-carbon negative electrode material are realized through hierarchical pore structure design, carbonization-activation synergistic pore forming and interface deposition process optimization, and the graphite-based silicon-carbon negative electrode material can be applied to the fields of power batteries and high-energy-density energy storage, especially the field of lithium ion batteries and has wide application prospects. The expansion rate of the battery can be reduced, and the specific capacity, cycling stability and safety of the lithium ion battery can be improved.

The invention relates to the technical field of lithium ion battery silicon-carbon coating, in particular to a silicon-carbon composite material, a silicon-carbon negative electrode material, a preparation method of the silicon-carbon negative electrode material and a battery. The preparation method of the silicon-carbon composite material comprises the following steps: S1, mixing porous carbon and a gaseous organic silicon source for reaction under the conditions of 450-550 DEG C and 100-200 kPa; s2, under the condition of 500-800 DEG C, carrying out carbon coating on the product obtained in the step S1 by using a carbon source to obtain a silicon-carbon composite material; the flow velocity of the gaseous organic silicon source is 12-30L / min. The silicon-carbon composite material provided by the invention has good conductivity, and the subsequently prepared silicon-carbon negative electrode material and battery material have good electrochemical performance.

The present invention relates to a porous silicon-carbon composite having a core-shell structure, a preparing method therefor, and an anode active material comprising same, wherein the core comprises silicon particles and the shell comprises two or more carbon layers including a first carbon layer and a second carbon layer, so that the application of the composite as an anode active material for a secondary battery can enhance the discharge capacity, initial efficiency, and capacity retention rate of the secondary battery. In addition, the preparing method for the porous silicon-carbon composite having the core-shell structure enables the mass production through a continuous process with minimized steps.

The invention belongs to the technical field of lithium ion battery negative electrode materials, and particularly relates to a method for preparing a lithium ion battery negative electrode material from sulfur-doped black phosphorus-carbon. A carbon material and sulfur powder are subjected to ball milling, uniform mixing and vacuum high-temperature calcination to obtain a sulfur-doped carbon material; and uniformly mixing the sulfur-doped carbon material with black phosphorus, and performing high-energy ball milling in an inert atmosphere to obtain the sulfur-doped black phosphorus-carbon composite negative electrode material. According to the preparation method provided by the invention, the black phosphorus, the carbon material and the sulfur are well combined, so that the high capacity of the material is ensured, the structural stability of the composite material can be improved, the polarization of the material is reduced, and the cycling stability and the rate capability of the battery are improved.

The invention discloses a silicon-carbon composite material and a preparation method thereof, a pole piece and a battery. The silicon-carbon composite material comprises a cluster structure and a third carbon layer coating the cluster structure, wherein the cluster structure comprises a plurality of silicon-carbon composite particles, pores are distributed among the plurality of silicon-carbon composite particles, each silicon-carbon composite particle has a core-shell structure, each silicon-carbon composite particle comprises an inner core and an outer shell coating the inner core, each outer shell sequentially comprises a first carbon layer and a second carbon layer in the direction far away from the inner core, the first carbon layer comprises a conductive carbon material with a three-dimensional structure, an annular gap exists between the second carbon layer and the first carbon layer, and the inner core comprises porous silicon nanoparticles. The battery prepared from the silicon-carbon composite material has excellent electrochemical performance.

The preparation method of the silicon-carbon composite material comprises the following steps: uniformly mixing a carbon source, a pore forming agent and a cross-linking agent, and introducing peroxide gas into a tubular furnace for sintering to obtain porous carbon; uniformly mixing the porous carbon with liquid silane and a surfactant, and transferring the mixture into a high-pressure reaction kettle for reaction to obtain a silicon-carbon precursor; and introducing the obtained material into a carbon source gas containing a heteroatom gas for deposition to obtain the silicon-carbon composite material. The obtained material generates porous carbon with high strength and high pore volume by utilizing the cross-linking agent and the pore-forming agent thereof, so that the expansion is reduced; and the liquid silane has the characteristics of low decomposition temperature, low cost and high safety performance, so that the specific capacity is improved, and the cost is reduced.

The invention relates to a preparation method and application of a composite porous carbon-based negative electrode material with soft carbon coated with hard carbon. The preparation method comprises the following steps: (S1) carbonizing and activating a soft carbon material precursor to obtain soft carbon core particles; (S2) carrying out graft modification on the oxidized soft carbon inner core particles through dopamine polyethylene glycol silane, and then carrying out in-situ copolymerization reaction on the modified soft carbon inner core particles and dopamine to obtain organic silicon-polydopamine coated soft carbon composite particles; (S3) carrying out in-situ polymerization of phenolic aldehyde on the surfaces of the composite particles to form phenolic aldehyde coated soft carbon composite particles; (S4) carbonizing and activating the phenolic aldehyde coated soft carbon composite particles to obtain hard carbon coated soft carbon composite porous carbon; and (S5) carrying out silicon deposition and carbon coating on the composite porous carbon to obtain the composite porous carbon-based negative electrode material with soft carbon coated with hard carbon. When the composite porous carbon-based negative electrode material with the soft carbon coated with the hard carbon prepared by the invention is applied to a negative electrode of a lithium battery, the composite porous carbon-based negative electrode material has good electrochemical performance, and particularly has excellent cycle performance and compression resistance.

The invention relates to the technical field of electrode materials, in particular to a silicon-carbon negative electrode material and a preparation method and application thereof. The silicon-carbon negative electrode material comprises a plurality of silicon-carbon composite particles, each silicon-carbon composite particle comprises porous carbon, nano silicon particles and phosphorus element which are attached in pores of the porous carbon, and coating carbon for coating the porous carbon, and n-type doping of the phosphorus element is formed at the joint of the nano silicon particles and the porous carbon. The preparation method comprises the following steps: (1) adsorbing phosphoric acid in porous carbon, and carrying out a heating reaction in a protective gas atmosphere to generate phosphorus-infiltrated porous carbon; (2) introducing a gaseous silicon source in a protective gas atmosphere, and carrying out silicon deposition on the phosphorus-infiltrated porous carbon by adopting a chemical vapor deposition method to obtain a phosphorus-doped silicon carbon material; and (3) carrying out carbon coating on the phosphorus-doped silicon carbon material to obtain the phosphorus-doped silicon carbon material. According to the method, the rate capability of the silicon-carbon negative electrode material can be remarkably improved while high first efficiency and high gram capacity are ensured.

The invention relates to a silicon-carbon composite material capable of improving the cycling stability of a battery, a preparation method of the silicon-carbon composite material, a negative pole piece and a lithium ion battery. The carbon-silicon composite particle comprises a silicon-carbon inner core and a carbon coating layer, nano-silicon is attached in holes and / or on the surface of a porous carbon matrix to form the silicon-carbon inner core, and the carbon coating layer is coated on at least part of the surface of the inner core; the porous carbon matrix and the carbon coating layer are both doped with halogen. According to the silicon-carbon composite material, the electron conductivity of the silicon-carbon composite material is improved by doping the halogen in the porous carbon matrix inside the silicon-carbon composite material and the carbon coating layer outside the silicon-carbon composite material; and meanwhile, the porous carbon matrix, the inner core composed of the nano silicon and the carbon coating layer are mutually matched and have synergistic interaction, so that the volume expansibility and defects of the silicon-carbon composite material are reduced, and the cycle stability is improved.

The invention discloses a chitosan modified lithium iron phosphate and carbon composite positive electrode material and a preparation method thereof.The preparation method comprises the steps that 1, lithium hydroxide, phosphoric acid and ferrous sulfate heptahydrate are mixed to prepare a uniform and stable solution, and a lithium iron phosphate precursor is prepared through a solvothermal method; step 2, dissolving chitosan in an acetic acid aqueous solution, and magnetically stirring under a water bath condition until the chitosan is completely dissolved to prepare a chitosan solution; and 3, adding the lithium iron phosphate precursor into a chitosan solution, uniformly mixing, carrying out ball milling and freeze drying, and carrying out high-temperature carbonization treatment in an inert gas to obtain the chitosan modified lithium iron phosphate and carbon composite positive electrode material. The method is simple to operate, low in cost and uniform in product particle size distribution.

The invention provides a silicon-carbon composite material as well as a preparation method and application thereof. The silicon-carbon composite material comprises a porous carbon material; the silicon particles are distributed on the surface layer of the porous carbon material and in pore channels in the porous carbon material, the distribution concentration of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material, and the particle size of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material; the silicon dioxide layer is formed on the surface of the silicon particles; and the carbon coating layer is formed on the surface of the silicon dioxide layer. The lithium ion battery prepared by taking the silicon-carbon composite material as a positive electrode active material shows good electrochemical performance, and has relatively high specific capacity, good cycling stability and rate capability.

The invention relates to a catalytically graphitized silicon-carbon composite material, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: providing a porous carbon precursor, sequentially carbonizing, activating and pore-forming, pickling, washing to be neutral, passivating to remove impurities, and then crushing and grading to obtain a porous carbon substrate with the particle size D50 of 5-20 microns; adding a graphitization catalyst into the porous carbon substrate for blending, and carrying out heat treatment at 800-1000 DEG C for 2-6 hours for catalytic modification to obtain modified porous carbon; and putting the obtained modified porous carbon into a chemical vapor deposition reaction furnace, and depositing silicon particles to obtain the catalytically graphitized silicon-carbon composite material. Wherein the graphitization catalyst comprises any one or more of potassium ferrate, iron oxide, nickel oxide, boron, aluminum, titanium, Fe-Si alloy and P-Ni alloy. The graphite catalyst is added to perform catalytic graphitization modification on the porous carbon substrate, so that the energy density, the cycle life and the rate capability of the battery are remarkably improved, and the application requirements of the high-performance battery are met.

A silicon-carbon material, a preparation method therefor, a secondary battery, and an electric device. The silicon-carbon material comprises silicon-carbon composite particles; the silicon-carbon composite particles comprise a porous carbon material, nano-silicon grains and a silicon carbide material layer; the porous carbon material is provided with through pores, the nano-silicon grains are located in the through pores, and the silicon carbide material layer is partially located on through pore walls; the grain size of the nano-silicon grains is not smaller than the average pore diameter of the porous carbon material. The silicon-carbon material is used as an active material of a negative electrode sheet, thereby improving the cycle performance of batteries.

The invention relates to the technical field of lithium battery negative electrode materials, in particular to a conductive polymer coated silicon-carbon composite material and a preparation method and application thereof.The conductive polymer coated silicon-carbon composite material comprises a porous silicon-carbon material and a conductive polymer, and the pore width of a porous structure in the conductive polymer coated silicon-carbon composite material is smaller than the in-pore width; the porous silicon carbon material comprises porous carbon and silicon particles, the conductive polymer comprises a polymer frame and a conductive material, the conductive material comprises at least one zero-dimensional conductive substance, at least one one-dimensional conductive substance and at least one two-dimensional conductive substance, and the component content of each conductive substance meets the formula: # imgabs0 # mA is the mass percentage of the component A in the whole system, Pc is the mass percentage of the component B in the whole system, and the component B is the mass percentage of the component B in the whole system. A is the mass fraction percolation threshold of the component A in the polymer framework. According to the invention, not only can a screening type structure be effectively constructed, but also the rate capability can be greatly improved, and finally the silicon-carbon composite material with high initial efficiency, low expansion, high cycle stability and excellent fast charging performance is obtained.

The invention discloses a silicon-carbon composite material which comprises porous carbon, silicon-containing particles are distributed on the surface of the porous carbon and in pore channels, the surfaces of the silicon-containing particles are coated with aluminum silicate layers, and the surface of the porous carbon is coated with a carbon layer. The invention also discloses a preparation method of the silicon-carbon composite material, which comprises the following steps: sequentially carrying out vapor deposition on the porous carbon by using silane, aluminum steam and vapor carbon to obtain the silicon-carbon composite material. The invention also discloses an application of the silicon-carbon composite material in a negative electrode material. When the silicon-carbon composite material is used in the lithium ion battery, the initial coulombic efficiency and the capacity retention rate of the lithium ion battery can be improved, and the expansion rate of a pole piece is reduced.

The invention belongs to the technical field of material preparation, and aims to solve the problems of interface separation and weak oxidation resistance under complex working conditions caused by insufficient interface bonding force of the existing carbon / carbon composite material. In order to achieve the purpose, the invention provides a carbon / carbon composite material and a preparation method thereof. The carbon / carbon composite material comprises the following components in percentage by mass: 40%-55% of polyacrylonitrile-based carbon fibers, 10%-25% of pitch-based carbon fibers, 8%-20% of nano silicon dioxide grafted carbon fibers, 8%-20% of biological pitch, 8%-15% of nano graphene modified phenolic resin, 3%-6% of silicon carbide whiskers, 2%-4% of zirconium boride nanoparticles, 2%-4% of graphitized carbon fibers and 1%-3% of a natural plant extract antioxidant. The carbon / carbon composite material provided by the invention can provide stable interface bonding force and remarkable oxidation resistance, so that the structural integrity and mechanical property stability of the material when bearing various complex stresses such as stretching, compression, bending, shearing and the like are guaranteed, and the application range of the material in the field of high-temperature oxidation resistance is widened.

The invention discloses a polypyrrole / cobalt / nitrogen-doped carbon composite material with a coaxial hollow structure and a preparation method thereof, and belongs to the technical field of advanced functional composite materials. The method comprises the following steps: firstly, synthesizing a hollow polypyrrole nanotube by a soft template method; secondly, cobalt / nitrogen-doped carbon is synthesized by adopting a template guiding method; and finally, secondarily coating the outer surface of the cobalt / nitrogen-doped carbon with a polypyrrole layer by adopting an in-situ oxidative polymerization method to construct the polypyrrole / cobalt / nitrogen-doped carbon composite material with a coaxial hollow heterostructure, and the polypyrrole / cobalt / nitrogen-doped carbon composite material has a coaxial sandwich structure: the inner core is a nitrogen-doped carbon hollow tube, the middle layer is a nitrogen-doped porous carbon matrix embedded with cobalt nanoparticles, and the outer surface of the cobalt / nitrogen-doped carbon composite material is a porous carbon matrix embedded with cobalt nanoparticles. And the outer layer is a conductive polypyrrole coating layer. The preparation method provided by the invention can successfully realize in-situ confinement growth and stable combination of ZIF-67, and has the advantages of high repetition rate, high yield and simple method; by adjusting the proportion of polypyrrole in the composite material, good impedance matching and large dielectric loss can be realized, and excellent electromagnetic wave absorption performance can be obtained.

The invention discloses a LiAlO2 fast ion conductor coated silicon-carbon composite material as well as a preparation method and application thereof, and belongs to the technical field of lithium ion battery materials. The LiAlO2 fast ion conductor coated silicon carbon composite material has a core-shell structure; an inner core of the composite material is a silicon-carbon composite material, the silicon-carbon composite material is formed by coating a three-dimensional carbon material with an amorphous carbon layer and loading a nano silicon compound, a shell of the composite material is a LiAlO2 fast ion conductor layer, and the silicon-carbon composite material with a three-dimensional network structure is constructed, and the surface of the silicon-carbon composite material is coated with the LiAlO2 fast ion conductor layer, so that the composite material is obtained. According to the present invention, with the LiAlO2, the volume expansion of the nanometer silicon during the charge-discharge process can be effectively relieved, the stability of the silicon-carbon composite material structure can be improved so as to significantly improve the cycle performance of the battery, and the LiAlO2 can provide the rapid channel for the transmission of the lithium ion during the charge-discharge process so as to improve the rate performance of the battery;

The invention relates to a silicon-carbon composite material, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: adding porous carbon into a fluidized bed, heating and introducing alkaline mixed gas to obtain amino porous carbon; transferring the amino porous carbon into fluidized bed equipment, vacuumizing, heating, and introducing hydroxyl silane gas for nano silicon deposition; after deposition, introducing ultraviolet light for polymerization and oxidation to obtain a modified silicon-carbon precursor material; transferring the modified silicon-carbon precursor material into a tubular furnace, introducing inert gas to discharge air in the tube, and performing first carbonization to obtain a silicon-carbon material; and adding the resin into an organic solvent, adding the fast ion conductor and the silicon carbon material to be uniformly dispersed, performing spray drying, and performing secondary carbonization to obtain the fast ion conductor coated silicon carbon composite material. The preparation method provided by the invention is simple and efficient, and the prepared silicon-carbon composite material can improve the fast charging performance and is suitable for a negative electrode material of a high-energy-density lithium ion battery.

The invention relates to the technical field of lithium ion batteries, and provides a preparation method of a silicon-carbon composite material and a lithium ion battery containing the composite.The preparation method of the silicon-carbon composite material comprises the steps that petroleum coke porous carbon is prepared; the method comprises the following steps: performing vapor deposition doping on petroleum coke porous carbon in a fluidized bed in a protective atmosphere to obtain an intermediate material; mixing the intermediate material with a liquid carbon material, transferring the mixture into a rotary furnace, and carrying out secondary granulation treatment; and carrying out passivating treatment on the material subjected to secondary granulation to obtain the silicon-carbon composite material. The characteristics of high anisotropy and high strength of the petroleum coke matrix are utilized, the impedance is reduced, the compaction density is improved, expansion is reduced, the cycle performance is improved, gas production is reduced through secondary granulation, the electronic conductivity and the coating integrity of the silicon-carbon composite material are improved through passivation, and the service life of the silicon-carbon composite material is prolonged. Therefore, the rate capability and high-temperature storage of the silicon-carbon composite material are improved.

The invention discloses a silicon-carbon negative electrode material and a preparation method thereof, the silicon-carbon negative electrode material has a core-shell structure, a high-capacity nano silicon-carbon composite material and graphite are uniformly dispersed to form a core layer, and a carbon coating layer is formed outside the core layer; the high-capacity nano silicon-carbon composite material comprises silicon, graphite and amorphous carbon, according to the preparation method, a high-capacity nano silicon carbon precursor, graphite and an organic carbon source are fully mixed, mechanically fused and then sintered at a high temperature to form the silicon carbon negative electrode material with a carbon coating layer as a shell and the high-capacity nano silicon carbon precursor and graphite uniformly dispersed inside, a multi-layer expansion buffer effect can be formed, and the expansion rate of particles is reduced; compared with a negative electrode material with a certain capacity formed by mixing a high-capacity silicon-carbon negative electrode material and graphite, particles have similar expansion degrees, and the problem that the cycle performance and the stability are reduced due to inconsistent expansion of the graphite and the silicon-carbon particles is solved.

The invention relates to a silicon-carbon composite material and a preparation method thereof, a negative pole piece, a secondary battery and a device, the silicon-carbon composite material comprises a carbon matrix with a pore structure and a silicon-based material distributed in the pore structure of the carbon matrix, and the silicon-carbon composite material contains phosphorus element. The silicon-based material in the silicon-carbon composite material improves the capacity of the carbon matrix, and the carbon matrix with the pore structure can be used as a buffer medium for volume expansion of the silicon-based material in the charging and discharging process while improving the conductivity of the silicon-based material, so that the problem that the volume of the secondary battery is increased due to silicon expansion is effectively relieved; and the phosphorus element doped in the skeleton of the carbon matrix is beneficial to improving the electronic conductivity of the material, so that the cycle performance of the battery is improved.

The invention belongs to the field of lithium ion batteries, and discloses a carbon-coated nanotube lithium titanate / carbon composite negative electrode material, a preparation method and a lithium ion battery. The lithium titanate / carbon composite negative electrode material is of a unique nanotube structure, the structure is composed of nanoparticles which are connected with one another and are covered with carbon layers on the surfaces, and certain gaps are formed among the nanoparticles. The preparation method comprises the following steps: dissolving a carbon source and hexadecyl trimethyl ammonium bromide in an organic solvent, then respectively adding the carbon source and a lithium source according to the proportion, and carrying out solvothermal reaction after fully stirring; and washing, drying and calcining the precipitate obtained after the reaction at high temperature to obtain the lithium titanate / carbon compound. Benefited from the synergistic interaction mechanism of the lithium titanate and the carbon material, the electron / ion transmission kinetics in the charge-discharge process of the lithium titanate / carbon compound is greatly improved, so that the lithium titanate / carbon compound has excellent rate capability and cycle performance. The method has the characteristics of simple process, environment friendliness, low cost, high efficiency and the like.

The invention relates to the field of battery materials, in particular to a preparation method and application of a modified porous carbon material for nano silicon CVD (chemical vapor deposition). According to the invention, the non-porous two-dimensional lamellar material is self-assembled on the porous carbon material, so that the modified porous carbon material for CVD deposition of nano-silicon is obtained, when high-speed carrier gas passes through the surface of the porous carbon material, the two-dimensional lamellar material on the surface of the porous carbon material is stressed intensively, and is not dispersed due to a pore channel structure on the surface of the porous carbon material; therefore, under the same fluidization condition, the modified porous carbon material shows better fluidization characteristics, deposition of nano silicon is more uniform after silane or organic gas is subsequently introduced, the content of floating silicon on the surface is extremely low, silicon enrichment can be reduced while the capacity of the negative electrode material is ensured, and the service life of the negative electrode material is prolonged. Furthermore, the electrochemical performance of the obtained nano silicon-carbon composite negative electrode material is more prominent, and the performance stability of negative electrode materials produced in different batches is also good.