CN113991095A - Negative active material, preparation method thereof, electrode and battery - Google Patents

Negative active material, preparation method thereof, electrode and battery Download PDF

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CN113991095A
CN113991095A CN202111618643.9A CN202111618643A CN113991095A CN 113991095 A CN113991095 A CN 113991095A CN 202111618643 A CN202111618643 A CN 202111618643A CN 113991095 A CN113991095 A CN 113991095A
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active material
carbon film
particles
silicon oxide
film layer
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CN113991095B (en
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罗姝
李喆
王岑
张和宝
查道松
连芸芸
叶兰
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Boselis Hefei Co ltd
Bosellis Nanjing Co ltd
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Amprius Nanjing Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01—ELECTRIC ELEMENTS
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a negative active material, a preparation method thereof, an electrode and a battery. The negative active material includes negative active material particles; the negative active material particles include silicon oxide particles, lithium elements inserted into the silicon oxide particles, and a carbon film layer, the silicon oxide particles include an inner core and a porous shell layer, and a surface of the porous shell layer is partially or completely covered with the carbon film layer. The negative electrode active material for a battery provided by the present invention has electrochemical characteristics of high efficiency, high energy density, and small expansion when used. The battery prepared by the cathode active material has the advantages of high energy density, excellent cycle performance, small cycle expansion, good high-temperature performance and the like.

Description

Negative active material, preparation method thereof, electrode and battery
Technical Field
The application relates to the field of batteries, in particular to a negative electrode active material for a battery, a preparation method of the negative electrode active material, an electrode and the battery.
Background
In recent years, with the continuous development of various portable electronic devices and electric vehicles, the demand for batteries having high energy density and long cycle life is becoming more urgent. The negative active material of the lithium ion battery commercialized at present is mainly graphite, but further improvement of the energy density of the battery is limited due to low theoretical capacity (372 mAh/g). The simple substance silicon cathode active material has high capacity advantage (the lithium insertion state is Li at room temperature)15Si4And the theoretical lithium storage capacity is about 3600 mAh/g), is about 10 times of the theoretical capacity of the current commercial graphite negative electrode active material, has the advantage of high capacity which cannot be matched by other negative electrode active materials, and therefore becomes a research and development hotspot for years in academia and industry, and gradually goes from laboratory research and development to commercial application.
At present, three main developments are provided for silicon cathode active materials, namely elemental silicon (including nano silicon, porous silicon, amorphous silicon and the like) and composite materials of the elemental silicon and the amorphous silicon and carbon materials; second, the alloy material that silicon combines with other metal (such as iron, manganese, nickel, chromium, cadmium, tin, copper, etc.), non-metal (carbon, nitrogen, phosphorus, boron, etc.); and thirdly, a silicon oxide compound and a composite material of the silicon oxide compound and the carbon material. In the above three structures, the theoretical capacity of the simple substance silicon material is the highest, so the theoretical energy density is also the highest. However, the elemental silicon negative active material has a severe volume effect during the lithium intercalation and deintercalation process, and the volume change rate is about 300%, which may cause pulverization of the electrode material and separation of the electrode material from the current collector. In addition, as the silicon negative electrode active material continuously expands and contracts during the charge and discharge processes of the battery to continuously crack, a new SEI film can be formed when the generated fresh interface is exposed in the electrolyte, so that the electrolyte is continuously consumed, and the cycle performance of the electrode material is reduced. The above drawbacks severely limit the commercial application of elemental silicon anodes.
The silicon oxide compound has more inactive substances, so that the capacity of the silicon oxide compound is lower than that of a simple substance silicon negative electrode active material; at the same time, however, the expansion of silicon during cycling is effectively inhibited by the inactive phase due to the presence of these inactive components, and thus its cycling stability is a significant advantage. However, silicone compounds also have their specific problems. For example, a thick SEI film is generated, lithium silicate, lithium oxide and other substances which cannot be reversibly delithiated are generated inside particles, ionic and electronic conductivity is low, and coulombic efficiency in a battery cycle process is low.
The statements in the background section merely represent prior art, and are not exhaustive of the prior art.
Disclosure of Invention
In order to solve one of the above-described technical problems, the present invention provides an anode active material for a battery, which includes anode active material particles;
the negative active material particles include silicon oxide particles, lithium elements embedded in the silicon oxide particles, and a carbon film layer, the silicon oxide particles include an inner core and a porous shell layer, and a surface of the porous shell layer is partially or completely covered with the carbon film layer.
In some embodiments of the present invention, the specific surface area of the negative active material is 0.1 to 15m2A/g, preferably from 0.3 to 10m2A/g, more preferably 0.3 to 6m2/g。
In some embodiments of the invention, the relative surface area of the negative electrode active material
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5, preferably
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3, more preferably
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2, further preference is given to
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1.5。
In some embodiments of the present invention, the negative active material particles have a relative tap density of 0.8 or more, preferably 0.85 or more.
In some embodiments of the present invention, the content of lithium element in the silicon oxide particles is 0.1 to 20wt%, preferably 2 to 18wt%, and more preferably 4 to 15 wt%.
In some embodiments of the present invention, the silicon element content in the silicon oxide particles is 30 to 80wt%, preferably 35 to 65wt%, and more preferably 40 to 65 wt%.
In some embodiments of the present invention, the proportion of silicon element in the porous shell layer is higher than the proportion of silicon element in the core.
In some embodiments of the invention, the proportion of lithium element in the porous shell layer is lower than the proportion of lithium element in the core.
In some embodiments of the present invention, the particles of the silicon oxide compound have a median particle diameter of 0.2 to 20 μm, preferably 1 to 15 μm, and more preferably 3 to 13 μm.
In some embodiments of the present invention, the negative active material particles further comprise elemental silicon nanoparticles, and the median particle diameter of the elemental silicon nanoparticles dispersed in the negative active material particles is between 0.1 nm and 35nm, preferably between 0.5 nm and 20nm, and more preferably between 1 nm and 15 nm.
In some embodiments of the present invention, the thickness of the carbon film layer is 0.001 to 5 μm, preferably 0.005 to 2 μm, and more preferably 0.01 to 1 μm.
In some embodiments of the present invention, the ratio of the carbon film layer in the negative active material particles is 0.01 to 20wt%, preferably 0.1 to 15wt%, and more preferably 1 to 12 wt%.
In some embodiments of the present invention, the coverage of the carbon film layer on the surface of the porous shell layer is 95% or more, preferably 98% or more.
In some embodiments of the present invention, further comprising a coating layer comprising an organic compound and/or a metal oxygen-containing compound, wherein a surface of the carbon film layer is partially or completely covered with the coating layer.
In some embodiments of the invention, the metal oxygen-containing compound is a composite oxide of a metal and phosphorus.
In some embodiments of the invention, the metal comprises one or more of lithium, titanium, magnesium, aluminum, zirconium, calcium, zinc.
The invention also provides an electrode comprising the anode active material.
The invention also provides a battery, which comprises the electrode.
The present invention also provides a method of preparing a negative active material for a battery, comprising the steps of:
coating a carbon film layer on the surface of the silicon oxide compound particles;
carrying out corrosion pore-forming on the silicon oxide compound particles coated with the carbon film layer to enable the silicon oxide compound particles coated with the carbon film layer to form a structure comprising an inner core and a porous shell layer; wherein the surface of the porous shell layer is partially or completely covered by the carbon film layer;
and carrying out lithium doping on the silicon oxide compound particles subjected to the pore forming by corrosion.
In some embodiments of the invention, the method further comprises:
and forming a coating layer comprising an organic compound and/or a metal oxygen-containing compound on the surface of the carbon film layer.
The present invention also provides a method of preparing a negative active material for a battery, comprising the steps of:
coating a carbon film layer on the surface of the silicon oxide compound particles;
performing lithium doping on the silicon oxide compound particles coated with the carbon film layer;
corroding the doped silicon oxide compound particles to form pores, so that the doped silicon oxide compound particles form a structure comprising an inner core and a porous shell layer; wherein the surface of the porous shell layer is partially or completely covered by the carbon film layer.
In some embodiments of the invention, the method further comprises:
and forming a coating layer comprising an organic compound and/or a metal oxygen-containing compound on the surface of the carbon film layer.
The negative electrode active material for a battery provided by the present invention has electrochemical characteristics of high efficiency, high energy density, and small expansion when used. The battery prepared by the cathode active material has the advantages of high energy density, excellent cycle performance, small cycle expansion, good high-temperature performance and the like.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
Fig. 1 is a flowchart of preparation of a negative active material according to an exemplary embodiment of the present invention.
Fig. 2 is a flowchart of preparation of a negative active material according to another exemplary embodiment of the present invention.
Fig. 3(a) and 3(b) are SEM images of a silicon oxide particle having a porous shell layer according to an exemplary embodiment of the present invention.
FIG. 4 is an SEM image of silica particles with a porous shell layer prepared according to another exemplary embodiment of the present invention.
FIG. 5 is a SEM image of a cross-section of the silicon oxide particle having a porous shell layer shown in FIG. 4, showing an enlarged cross-section of the porous shell layer.
Detailed Description
The following detailed description of the present invention, taken in conjunction with the accompanying drawings and examples, is provided to enable the invention and its various aspects and advantages to be better understood. However, the specific embodiments and examples described below are for illustrative purposes only and are not limiting of the invention.
It is expressly intended that all such similar substitutes and modifications which would be obvious to one skilled in the art are deemed to be included in the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.
[ NEGATIVE-ELECTRODE ACTIVE MATERIAL ]
The present invention provides a negative active material for a battery, which has negative active material particles. The negative electrode active material particles contain a silicon oxide compound in the form of particles and a lithium element embedded in the silicon oxide compound particles. The silica compound particles include a solid core and a porous shell layer, and the surface of the porous shell layer is partially or completely covered with a carbon film layer. That is, the negative active material provided by the present invention includes an inner core, a porous intermediate layer (i.e., a porous shell layer of silicon oxide compound particles), and a carbon film layer.
The porous shell layer as the intermediate layer can effectively accommodate partial volume expansion of silicon in the lithium intercalation process, release the stress in the particles and reduce the breakage degree of the particles. Meanwhile, in the circulation process, the repeated damage and the rapid thickening of the SEI film can be effectively inhibited, the circulation expansion and the internal resistance increase amplitude of the battery after multiple charging and discharging are reduced, and the service life and the stability of the battery are improved.
The existence of the solid core can improve the mechanical strength of the negative active material particles and the volume ratio of effective active materials, on one hand, the negative active material particles are prevented from being broken in the pole piece rolling process, and on the other hand, the volume ratio capacity and the volume ratio energy of the material are also improved.
In the present invention, the specific surface area of the anode active material particles may be 0.1 to 15m2A/g, preferably from 0.3 to 10m2/g，More preferably 0.3 to 6m2(ii) in terms of/g. In the specific surface area range, the negative electrode active material particle surface has fewer side reactions and higher stability.
In the present invention, the relative surface area of the anode active material may be 5 or less, preferably 3 or less, more preferably 2 or less, and further preferably 1.5 or less. In the invention, the specific surface area of the negative active material is defined as A, the specific surface area of the silicon-containing material which does not have a porous shell layer but has other structures consistent with those of the negative active material is defined as B, and the relative ratio surface area is A/B. The "silicon-containing material having no porous shell layer but having a structure identical to that of the negative active material" as used herein means that the silicon-containing material is the same as the negative active material of the present invention except that it has no porous shell layer.
In the present invention, the relative tap density of the anode active material particles is defined as D, and optionally, the value of D satisfies D.gtoreq.0.8, preferably D.gtoreq.0.85. In the present invention, the tap density of the anode active material particles is defined as D1, and the tap density of a silicon-containing material having no porous shell layer but otherwise having a structure consistent with the anode active material is defined as D2, and the relative tap density D = D1/D2. In the range of the relative tap density, the volume ratio of the porous shell layer and the solid core in the particle is balanced, so that the functions of accommodating the volume expansion of the silicon cathode and reducing SEI (solid electrolyte interphase) damage of the porous shell layer can be realized, and the reduction of the mechanical strength of the particle and the loss of volumetric specific energy can be avoided.
In the present invention, the porous shell layer may include micropores and/or mesopores, wherein the micropores are pores having a diameter of 2nm or less, and the mesopores are pores having a diameter of 2 to 50 nm. The porous shell may also comprise macropores, which are pores with a diameter of more than 50 nm.
In the present invention, the content of lithium element in the silicon oxide particles may be 0.1 to 20% by weight, preferably 2 to 18% by weight, more preferably 4 to 15% by weight.
In the present invention, the silicon element content of the silicon oxide compound particles may be 30 to 80wt%, preferably 35 to 65wt%, more preferably 40 to 65wt%, and therefore the anode active material of the present invention has a high reversible capacity.
Further, in the anode active material particle of the present invention, the proportion of silicon element in the porous shell layer may be more than the proportion of silicon element in the solid core. The element distribution is beneficial to improving the first effect and reversible capacity of the negative active material particles.
Further, in the anode active material particle of the present invention, the proportion of the lithium element in the porous shell layer may be lower than the proportion of the lithium element in the solid core.
In the present invention, the median particle diameter of the silicon oxide compound particles may be 0.2 to 20 μm, preferably 1 to 15 μm, more preferably 3 to 13 μm.
The anode active material particles of the present invention may further include elemental silicon nanoparticles, which may be uniformly dispersed in the anode active material particles. The median particle diameter of the elementary silicon nanoparticles can be 0.1-35nm, preferably 0.5-20nm, and more preferably 1-15 nm. When the particles are subjected to a cycle of lithium ion intercalation and deintercalation, the particles are less expanded and less prone to rupture, so that the lithium ion secondary battery using the material is less expanded and stable in cycle.
In the present invention, the thickness of the carbon film layer may be 0.001 to 5 μm, preferably 0.005 to 2 μm, and more preferably 0.01 to 1 μm. The existence of the carbon film layer can effectively improve the conductivity of particles, and reduce the contact resistance among particles in the negative pole piece, the negative pole piece and the current collector, thereby improving the lithium desorption and insertion efficiency of the material, reducing the polarization of the lithium ion battery and promoting the cycle stability of the lithium ion battery.
Further, the proportion of the carbon film layer in the anode active material particle may be 0.01 to 20wt%, preferably 0.1 to 15wt%, more preferably 1 to 12 wt%.
Further, the coverage rate of the carbon film layer on the surface of the porous shell layer is more than 95%, preferably more than 98%. The higher the coverage rate of the carbon film layer on the surface of the porous shell layer is, the more effective the carbon film layer can isolate the direct contact between the porous shell layer and the electrolyte, and the adverse effect caused by the larger specific surface area of the porous shell layer is greatly reduced. The coverage rate of the carbon film layer is high, the specific surface area of the negative active material particles containing the porous shell layer can be reduced, the side reaction of the material and the electrolyte is reduced, and the stability of the material in the battery is improved.
In the invention, the surface of the negative active material particle can also comprise a coating layer, and the coating layer completely covers or partially covers the carbon film layer. The coating may comprise an organic compound and/or a metal oxygen-containing compound. The coating layer can further isolate the contact between the porous shell layer and the electrolyte, so that the specific surface area of the negative active material particles containing the porous shell layer is further reduced, the side reaction of the material and the electrolyte is reduced, and the stability of the negative active material particles in the battery is improved.
The metal oxygen-containing compound may be a composite oxide of a metal and phosphorus. The metal may include one or more elements of lithium, titanium, magnesium, aluminum, zirconium, calcium, zinc.
The negative active material for a battery has electrochemical characteristics of high efficiency, high energy density, and less expansion when used. The battery prepared by the cathode active material has the advantages of high energy density, excellent cycle performance, small cycle expansion, good high-temperature performance and the like.
[ METHOD FOR PRODUCING NEGATIVE-ELECTRODE ACTIVE MATERIAL ]
Fig. 1 is a flowchart of preparation of a negative active material according to an exemplary embodiment of the present invention.
S101: silica compound particles are prepared.
The specific preparation process can be carried out by adopting the following steps:
first, a mixture of a metal silicon powder and a silicon dioxide powder is heated at a temperature ranging from 900 to 1600 ℃ in an inert gas atmosphere or under reduced pressure to generate a silicon oxide gas, and the molar ratio of the metal silicon powder to the silicon dioxide powder is set in the range of 0.5 to 1.5. Gas generated by the heating reaction of the raw materials is deposited on the adsorption plate. When the temperature in the reaction furnace is lowered to 100 ℃ or lower, the deposit is taken out, and pulverized and powdered by means of a ball mill, a jet mill or the like, thereby obtaining silicon oxide particles.
The silicon oxide compound particles include silicon oxide (silicon monoxide and/or silicon dioxide) material. In exemplary embodiments of the present invention, the stoichiometric ratio of silicon to oxygen in the silicon oxide compound particles may be 1:0.4 to 1:2, alternatively 1:0.6 to 1:1.5, and more alternatively 1:0.8 to 1: 1.2. Of course, there may be other trace impurity elements in addition to silicon oxide.
S102: and coating a carbon film layer on the surfaces of the silicon oxide particles.
According to exemplary embodiments, the silicon oxide compound may be a silicon oxide compound that is not disproportionated, or a silicon oxide compound that is disproportionated heat-treated. Wherein the disproportionation heat treatment temperature may be 600-1100 ℃, alternatively 700-1000 ℃, more preferably 800-1000 ℃.
In the present invention, the carbon film layer can be directly obtained by Chemical Vapor Deposition (CVD). The carbon source used in CVD is hydrocarbon gas, and the decomposition temperature of the hydrocarbon gas can be 600-1100 ℃, preferably 700-1000 ℃, and more preferably 800-1000 ℃.
The carbon film layer can also be obtained by carrying out carbon reaction coating and then carrying out heat treatment carbonization in a non-oxidizing atmosphere. The carbon reaction coating method can adopt any one of a mechanical fusion machine, a VC mixer, a coating kettle, spray drying, a sand mill or a high-speed dispersion machine, and the solvent selected during coating is one or a combination of more of water, methanol, ethanol, isopropanol, N-butanol, ethylene glycol, diethyl ether, acetone, N-methylpyrrolidone, methyl butanone, tetrahydrofuran, benzene, toluene, xylene, N-dimethylformamide, N-dimethylacetamide and trichloromethane. The carbon reactive source may be one or a combination of coal pitch, petroleum pitch, polyvinyl alcohol, epoxy resin, polyacrylonitrile, polymethyl methacrylate, glucose, sucrose, polyacrylic acid, polyvinylpyrrolidone. The equipment used for heat treatment carbonization can be any one of a rotary furnace, a ladle furnace, a roller kiln, a pushed slab kiln, an atmosphere box furnace or a tubular furnace. The temperature for heat treatment carbonization can be 600-1100 ℃, preferably 700-1000 ℃, more preferably 800-1000 ℃, and the holding time is 0.5-24 hours. The non-oxidizing atmosphere may be provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
S103: and carrying out corrosion pore-forming on the silicon oxide compound particles coated with the carbon film layer to enable the silicon oxide compound particles coated with the carbon film layer to form a structure comprising a solid inner core and a porous shell layer.
Wherein the surface of the porous shell layer is partially or completely covered by the carbon film layer.
The corrosive pore-forming agent used can include various acids, bases or oxidants used in combination. The acid which may be used includes nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, perchloric acid, chloric acid, etc., the base which may be used includes sodium hydroxide, potassium hydroxide, barium hydroxide, etc., and the oxidant which may be used cooperatively includes hydrogen peroxide, etc. By adjusting the proportion and concentration of the used corrosive pore-forming agent, the temperature, stirring speed, time and the like in the reaction process, the porous shell layers with different pore sizes and different thicknesses (or volume ratios) can be obtained.
The step of etching and pore-forming the silicon oxide compound particles is placed after the step of coating the carbon film layer, so that the carbon film layer with better quality and more complete coating can be obtained. The coating rate of the carbon film layer on the particle surface is preferably 95% or more, more preferably 98% or more. In this way, a relatively complete and continuous carbon film coating can be formed on the particle surface.
After the silicon oxide compound particles coated with the carbon film layer are subjected to corrosion pore-forming, the carbon film layer is reserved and completely covers the surface of the porous shell layer, and the porous shell layer is isolated and protected. If the above steps are reversed and the carbon film layer is coated after pore formation, a continuous carbon film coating layer is difficult to form due to the unevenness and unevenness of the porous surface, and thus the coverage rate and the protective and isolating effects of the carbon film layer are greatly reduced. In addition, after the step of etching and pore-forming is completed on the silicon oxide compound particles coated with the carbon film layer, secondary carbon coating can be performed on the particles, so that the coverage rate of the carbon film layer on the surface of the particles is further improved, and the isolation and protection effects of the carbon film layer on the porous shell layer are further optimized.
S104: and carrying out lithium doping on the silicon oxide compound particles after the pore is formed by corrosion.
In the present invention, the doping (lithium intercalation) of the silicon oxide particles may be performed by electrochemical doping, liquid phase doping, thermal doping, or the like. The doping atmosphere of the lithium element is a non-oxidizing atmosphere composed of at least one of nitrogen, argon, hydrogen, and helium.
The lithium intercalation method (lithium doping modification method) may be:
1) electrochemical process
An electrochemical cell is provided, which comprises a bath, an anode electrode, a cathode electrode and a power supply, wherein the anode electrode and the cathode electrode are respectively connected with two ends of the power supply. At the same time, the anode electrode is connected to a lithium source, and the cathode electrode is connected to a container containing silicon oxide particles. The bath was filled with an organic solvent, and a lithium source (anode electrode) and a container (cathode electrode) containing particles of a silicon oxide compound were immersed in the organic solvent. After the power is switched on, lithium ions are inserted into the silicon oxide structure due to the occurrence of electrochemical reaction, and lithium-doped modified silicon oxide particles are obtained. As the organic solvent, there can be used ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide and the like. The organic solvent may further contain an electrolyte lithium salt, and lithium hexafluorophosphate (LiPF) may be used6) Lithium tetrafluoroborate (LiBF)4) Lithium perchlorate (LiClO)4) And the like. The lithium source (anode electrode) may be a lithium foil or a lithium compound such as lithium carbonate, lithium oxide, lithium hydroxide, lithium cobaltate, lithium iron phosphate, lithium manganate, lithium vanadium phosphate, lithium nickelate, or the like.
2) Liquid phase doping method
Adding metallic lithium, an electron transfer catalyst and silicon oxide compound particles into an ether-based solvent, continuously stirring and heating in a non-oxidizing atmosphere to keep constant temperature reaction until the metallic lithium in the solution completely disappears. Under the action of an electron transfer catalyst, metallic lithium can be dissolved in an ether-based solvent and forms a coordination compound of lithium ions, which has a low reduction potential and can react with a silicon oxide compound, and the lithium ions enter the structure of the silicon oxide compound. The electron transfer catalyst includes biphenyl, naphthalene, and the like. The ether-based solvent comprises methyl butyl ether, ethylene glycol butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and the like. The constant temperature reaction temperature is 25-200 ℃. The non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
3) Thermal doping method
Silicon oxide particles are uniformly mixed with a lithium-containing compound, and then heat-treated in a non-oxidizing atmosphere. The lithium-containing compound includes lithium hydroxide, lithium carbonate, lithium oxide, lithium peroxide, lithium hydride, lithium nitrate, lithium acetate, lithium oxalate, and the like. The mixing method adopts any one of a high-speed dispersion machine, a high-speed stirring mill, a ball mill, a conical mixer, a spiral mixer, a stirring mixer or a VC mixer. The equipment used for the heat treatment is any one of a rotary furnace, a ladle furnace, a liner furnace, a roller kiln, a pushed slab kiln, an atmosphere box furnace or a tubular furnace. The temperature of the heat treatment is 400-850 ℃, preferably 550-800 ℃; the heat preservation time is 1-12 hours; the heating rate is more than 0.1 ℃ per minute and less than 10 ℃ per minute. The non-oxidizing atmosphere is provided by at least one of the following gases: nitrogen, argon, hydrogen or helium.
The step of inserting lithium element is performed after the carbon film layer is coated, and the growth of silicon crystal grains in the silicon oxide compound in the heat treatment process can be inhibited. Therefore, the nanoscale simple substance silicon particles are uniformly dispersed and fixed in the lithium silicate compound or silicon oxide compound matrix, the expansion of the silicon nanoparticles can be effectively inhibited, and the silicon particles are prevented from being gradually fused into particles with larger sizes in the charging and discharging processes, so that the expansion deformation of the battery in the circulating process is reduced, the electrical failure of the silicon material is reduced, and the lithium ion secondary battery using the material has small circulating expansion and stable circulation. In addition, the step of coating the carbon film layer is carried out before lithium element is inserted, so that the carbon film layer with better quality and more complete coating can be obtained.
Fig. 2 shows a preparation flow of an anode active material according to another exemplary embodiment of the present invention. The method comprises the following steps:
s201: silica compound particles are prepared.
S202: and coating a carbon film layer on the surfaces of the silicon oxide particles.
S203: and carrying out lithium doping on the silicon oxide compound particles coated with the carbon film layer.
S204: and etching the doped silicon oxide compound particles to form pores, so that the doped silicon oxide compound particles form a structure comprising an inner core and a porous shell layer.
The embodiment shown in fig. 2 differs from the embodiment shown in fig. 1 only in the order of etching the pores. In the embodiment shown in fig. 1, the carbon film is coated and then etched to form a hole, and then lithium doping is performed, while in the embodiment shown in fig. 2, the carbon film is coated and then lithium doping is performed, and then the hole is etched to form a hole.
According to an exemplary embodiment, after the above-described steps are completed, a coating layer of an organic compound and/or a metal oxygen-containing compound may be further coated on the surface of the anode active material particles. In the forming of the coating layer, the coating layer may be formed on the surface of the anode active material particle by a solid-phase mechanical mixing method, a liquid-phase in-situ growth method, or a gas-phase method. When the coating is carried out by a liquid phase in-situ growth method, a water-soluble or alcohol-soluble reactant is prepared into a solution with a certain concentration, and then the coating is grown in situ on the surface of the negative active material particles by the solution method. The vapor phase method may be selected from Atomic Layer Deposition (ALD), physical vapor deposition, chemical vapor deposition, evaporation, and the like. The forming step of the coating layer can comprise a heat treatment step, wherein the heat treatment temperature is not higher than 850 ℃, the holding time is 0.1-12 hours, and the atmosphere can be vacuum or non-oxidizing atmosphere. Wherein the non-oxidizing atmosphere comprises at least one of nitrogen, argon, hydrogen, or helium. Further, the heat treatment temperature should not be higher than the heat treatment temperature for lithium intercalation.
[ characterization method of negative electrode active material ]:
1. and (3) material detection: the anode active materials prepared in the respective examples and comparative examples were characterized using the following apparatus: the particle size distribution of the negative active material was tested using a laser particle sizer model BetterSize 2000, Dandong Baite. The surface morphology of the negative active material was observed with a Hitachi SU8010 Scanning Electron Microscope (SEM). The specific surface area of the negative active material was measured using a specific surface area tester model NOVA 4200e from Quantachrome Instruments. The specific surface area test requirements are as follows: weighing the sample by using a sample tube, and testing the specific surface area of the sample by using a multipoint method at a relative pressure p/p0= 0.05-0.3 by using nitrogen.
The tap density of the obtained negative electrode material was measured using a Dandongbaut BT-301 tap density tester. The test requirements of tap density are as follows: preparing a measuring cylinder of 25ml, fixing the measuring cylinder on a base of the equipment, aligning an original point on a sample table with an original point on the equipment, and screwing down the base; then adding 10-20 g of sample powder, and recording the mass of the powder as m; the surface of the powder in the measuring cylinder is kept in a horizontal state as much as possible, and a rubber plug is plugged into the orifice of the measuring cylinder; then, vibrating the sample 3000 times according to the vibration frequency of 200 Hz; after the test is finished, if the upper surface of the sample in the measuring cylinder is horizontal, the V is directly read; if the surface of the sample in the measuring cylinder is not horizontal, reading the highest point V1 and the lowest point V2, and taking the average value V of the two points; the tap density ρ = m/V of the sample was then obtained.
2. Homogenizing and manufacturing pole pieces: and (3) homogenizing and coating 30 parts of the negative active material, 64 parts of artificial graphite, 2.5 parts of a conductive additive and 3.5 parts of a binder in an aqueous system, and then drying and rolling to obtain the negative pole piece containing the negative active material.
3. Full cell evaluation: the negative electrode sheet of the negative electrode active material prepared in each example and comparative example was cut, vacuum-baked, wound together with the paired lithium cobaltate positive electrode sheet and separator, and loaded into an aluminum plastic case of a corresponding size, and a certain amount of electrolyte was injected, degassing and sealing were performed, and a lithium ion full cell of about 3.2Ah was obtained after formation. The efficiency, capacity, energy and cycling stability of the full cell at 0.2C were tested with a cell tester from new wile electronics ltd, shenzhen. In addition, the full battery is also made 60oAnd C, testing the cold expansion rate of the system after high-temperature storage in an experiment of full-electricity high-temperature storage for 10 days, and evaluating the high-temperature storage stability of the system. The test method of the cold state expansion rate comprises the following steps: wait for electric core at 60oC, after 10 days of full electricity storage, taking out the cell and cooling for 2 hours, and testing the thickness of the cell to be d, wherein the initial full electricity thickness of the cell is d0, and the cold state expansion rate = (C)d-d0)/d0。
The present application is further illustrated by the following specific examples.
Examples 1 to 1
1000 g of silicon oxide particles having a median particle diameter of 6 μm (silicon to oxygen atom ratio: 1) were weighed and placed in a CVD furnace. Acetylene is used as a carbon source, and a coating reaction is carried out at 950 ℃ to obtain silicon oxide compound particles coated with a relatively complete carbon film layer, wherein the coverage rate of the carbon film layer reaches 95%, and the thickness of the carbon film layer is 20 nm.
Then preparing a hydrofluoric acid solution with the concentration of 2mol/L, adding the silicon oxide particles coated with the carbon film layer, and continuously reacting for 24 hours at the stirring speed of 300r/min to obtain the silicon oxide particles with a porous shell layer, wherein the porous shell layer is mainly macropores with the pore diameter of more than 400nm, and the carbon film layer is kept intact (as shown in fig. 3(a) and fig. 3 (b)).
Then, the lithium metal doping is carried out by adopting a thermal doping method, and specifically: mixing the above particles with lithium-containing compound (such as lithium oxide, lithium hydride, lithium hydroxide, lithium carbonate, etc.), heat treating the mixed powder in argon atmosphere, heating to 720 deg.C at a heating rate of 3 deg.C per minute for 3 hr, and naturally cooling to obtain coated carbon film and negative electrode active material with porous shell layer.
The negative active material obtained in the above step had a relative tap density of 0.8 and a relative surface area (relative BET) of 3.
And (3) taking 30 parts of the negative electrode active material, 64 parts of artificial graphite, 3.5 parts of conductive additive and 2.5 parts of binder, homogenizing and coating in a water-based system, and then drying and rolling to obtain the silicon-containing negative electrode plate. The pole piece can bear at least 1.55-1.6g/cm3At which the negative electrode active material particles in this embodiment are not broken by the rolling process.
In the present example, the full cell evaluation result containing the anode active material was: the first-cycle coulombic efficiency (FCE) of the full cell was 85.3%, the volumetric energy density at 0.2C was 801.6Wh/L, the retention rate of the full cell after 400 cycles was 79%, and the cell expansion rate after 400 cycles was 14.5%.The full battery is also made 60oAnd C, in the experiment of full electricity high-temperature storage for 10 days, the cold state expansion rate of the high-temperature storage is 4.6%.
Examples 1 to 2
Silicon oxide particles were coated with a carbon film layer having a coverage of 96% and a thickness of 40nm by a process similar to that of example 1-1.
Then, a hydrofluoric acid solution with a concentration of 12mol/L is prepared, the silicon oxide particles coated with the carbon film layer are added, and the reaction lasts for 1 hour at a stirring speed of 500r/min, so that the silicon oxide particles with porous shell layers are obtained, the carbon film layer is kept intact, and meanwhile, no macropores exist on the outer surface of the particles (as shown in figure 4). Then observing the section of the porous shell of the particle, as shown in figure 5, the material is seen to mainly contain 10-30nm mesopores; analysis by a nitrogen adsorption and desorption test shows that the material also contains a small amount of micropores.
Next, the above silicone compound powder, metal lithium ribbon and biphenyl were added to a sealable glass container, followed by addition of methyl butyl ether and stirring reaction under an argon atmosphere. And after the reaction is finished and dried, placing the obtained powder in an argon atmosphere for heat treatment, heating to 680 ℃ at a heating rate of 5 ℃ per minute, then preserving heat for 2 hours, and then naturally cooling to obtain the lithium-doped negative electrode active material.
The negative electrode active material obtained in the above step had a relative tap density of 0.97 and a relative surface area of 2.
A negative electrode piece capable of withstanding at least 1.7g/cm was fabricated in the same manner as in example 1-13At which the negative electrode active material particles in this embodiment are not broken by the rolling process.
In this example, the negative active material full cell evaluation results were: the FCE of the full cell was 86.1%, the volumetric energy density at 0.2C was 805Wh/L, the retention rate of the full cell after 400 cycles was 81.2%, and the cell expansion rate after 400 cycles was 13.6%. The full cell had a high temperature storage cold state expansion rate of 3.8%.
Examples 1 to 3
Silicon oxide particles coated with a carbon film were obtained by a similar process to that of example 1-2.
Next, the above-described silicon oxide compound coated carbon film was lithium-doped using a process similar to that of example 1-2.
Then, a hydrofluoric acid solution with the concentration of 1mol/L is prepared, the silica particles are added, and the reaction is continued for 2 hours at the stirring speed of 300r/min, so that the silica particles with porous shell layers are obtained. The performance results of this material are shown in table 1.
Examples 1 to 4
Examples 1-4 were similar to examples 1-3 except that the etch pore-forming process was adjusted and the etch pore-forming agent was replaced with 2mol/L sodium hydroxide solution.
Examples 1-5 to 1-7
By using the process similar to that of example 1-1, a carbon-coated silica compound having a porous shell layer was obtained, and by adjusting the concentration of the corrosive pore-forming agent and the reaction time, a material having a porous shell layer with different relative tap densities and porosities could be obtained. Before the lithium doping step, the material is subjected to secondary carbon coating treatment, and the specific process comprises the following steps: the material and coal tar pitch powder are mixed evenly by a dry method, heated and stirred to ensure that the coal tar pitch is evenly coated on the surface of the material, and then heated to 900 ℃ to ensure that the coal tar pitch is carbonized. After the secondary carbon coating treatment, the coverage rate of the carbon film on the surface of the material is further improved, the direct contact between the porous shell layer and the electrolyte is effectively isolated, and the specific surface area of the negative active material particles containing the porous shell layer can also be reduced.
This material was then lithium doped using a process similar to that of examples 1-2.
Examples 1 to 8
Similar procedures as in examples 1-4 were used except that the carbon film layer coverage of the first step siloxane was reduced to 90%.
Examples 1 to 9 and 1 to 10
The process similar to that of example 1-1 was adopted except that the proportion of the porous shell layer and the proportion of the pores in the material were further increased by adjusting the addition amount of the pore-forming corrosive agent and the reaction time, and the relative tap densities of the obtained products were reduced to 0.75 and 0.7, respectively. The material with higher void fraction can effectively reduce the volume expansion of the material after lithium intercalation, but the final volume specific capacity and volume specific energy of the material are reduced because the volume fraction of the effective active substance is lower.
Comparative examples 1 to 1
The lithium-containing silicone oxide compound of the carbon-coated film layer without the porous shell layer was obtained by a process similar to that of example 1-1, but omitting the step of preparing the porous shell layer. The full cell FCE of this negative active material was 87%, however, since the volume expansion of this material was large, the thickness expansion in the full charge state of the cell was significant, resulting in a drop in the volumetric energy density at 0.2C of 790.1 Wh/L. Meanwhile, after the battery is repeatedly expanded and contracted in the process of multiple cycles, the battery is obviously deformed and the diaphragm is bonded to lose efficacy, so that the retention rate of the full battery after 400 cycles is only 66%, and the expansion rate of the battery cell is as high as 24.1%. In addition, the cold state expansion rate of the high-temperature storage is 3.4%.
Comparative examples 1 to 2
The lithium-containing silicon oxide compound with a porous surface layer and no carbon film layer was obtained by a process similar to that of examples 1 to 3, but omitting the step of coating the carbon film layer in the first step. The relative surface area of the negative active material was as high as 30, and thus the FCE of its full cell was only 80.2%, and the volumetric energy density at 0.2C was only 754 Wh/L. The retention rate of the battery after 400 cycles is only 50%, the battery core generates obvious lithium precipitation and expansion deformation, and the expansion rate reaches 31.9%. Meanwhile, the cold state expansion rate of the high-temperature storage is up to 17.8%.
Comparative examples 1 to 3
A similar procedure to that used in examples 1-3 was used, but the degree of pore-forming corrosion was further increased, so that the material had no solid core, but only a surface carbon film layer and a porous core. The relative tap density of the material decreased to 0.5 while the relative surface area increased to 15. A negative electrode piece was fabricated in the same manner as in example 1-1, and the piece was able to withstand only 0.8 g/cm3The greater the compaction density, the greater the compaction density will result in breakage of the particles during compaction. The FCE of the full cell using this material is therefore only 81.6%, and its volumetric energy density at 0.2C is onlyIs 748.9 Wh/L. The retention rate of the battery after 400 cycles is only 59.8%, the lithium precipitation and deformation of the battery cell are obvious, and the expansion rate is as high as 27.3%. Meanwhile, the cold state expansion rate of the high-temperature storage is up to 12.3%.
TABLE 1
Figure 887921DEST_PATH_IMAGE002
Examples 2-1 to 2-7
Negative active materials having porous shell layers with different carbon film coverage and relative tap densities were obtained using similar processes as in examples 1-1 to 1-4. Then, different kinds of coating layers were coated on the material to obtain different negative electrode active materials of examples 2-1 to 2-7, the performance parameters of which are shown in table 2.
Examples 2-8 to 2-11
Different kinds of coating layers were coated on the surfaces of the negative electrode active materials obtained in examples 1-1 to 1-4, respectively, to obtain different negative electrode active materials of examples 2-8 to 2-11, whose performance parameters are shown in table 2.
TABLE 2
Figure DEST_PATH_IMAGE003
It should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims (22)

1. A negative electrode active material for a battery, characterized by comprising negative electrode active material particles;
the negative active material particles include silicon oxide particles, lithium elements embedded in the silicon oxide particles, and a carbon film layer, the silicon oxide particles include an inner core and a porous shell layer, and a surface of the porous shell layer is partially or completely covered with the carbon film layer.
2. The negative electrode active material according to claim 1, wherein the specific surface area of the negative electrode active material is 0.1 to 15m2A/g, preferably from 0.3 to 10m2A/g, more preferably 0.3 to 6m2/g。
3. The negative electrode active material of claim 1, wherein the relative surface area of the negative electrode active material
Figure 138976DEST_PATH_IMAGE001
5, preferably
Figure 849443DEST_PATH_IMAGE001
3, more preferably
Figure 593408DEST_PATH_IMAGE001
2, further preference is given to
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1.5。
4. The negative active material of claim 1, wherein the negative active material particles have a relative tap density of 0.8 or more, preferably 0.85 or more.
5. The negative electrode active material according to claim 1, wherein the silicon oxide particles contain lithium in an amount of 0.1 to 20wt%, preferably 2 to 18wt%, and more preferably 4 to 15 wt%.
6. The anode active material according to claim 1, wherein the silicon element content in the silicon oxide particles is 30 to 80wt%, preferably 35 to 65wt%, and more preferably 40 to 65 wt%.
7. The negative active material of claim 1, wherein the proportion of silicon element in the porous shell layer is higher than the proportion of silicon element in the core.
8. The anode active material according to claim 1, wherein a proportion of lithium element in the porous shell layer is lower than a proportion of lithium element in the core.
9. The negative electrode active material according to claim 1, wherein the silica compound particles have a median particle diameter of 0.2 to 20 μm, preferably 1 to 15 μm, and more preferably 3 to 13 μm.
10. The negative electrode active material according to claim 1, wherein the negative electrode active material particles further comprise elemental silicon nanoparticles, and the median particle diameter of the elemental silicon nanoparticles dispersed in the negative electrode active material particles is between 0.1 and 35nm, preferably between 0.5 and 20nm, and more preferably between 1 and 15 nm.
11. The anode active material according to claim 1, wherein the carbon film layer has a thickness of 0.001 to 5 μm, preferably 0.005 to 2 μm, and more preferably 0.01 to 1 μm.
12. The anode active material according to claim 1, wherein the carbon film layer accounts for 0.01 to 20wt%, preferably 0.1 to 15wt%, and more preferably 1 to 12wt% of the anode active material particles.
13. The negative active material of claim 1, wherein the coverage of the carbon film layer on the surface of the porous shell layer is greater than or equal to 95%, preferably greater than or equal to 98%.
14. The anode active material according to claim 1, further comprising a coating layer comprising an organic compound and/or a metal oxygen-containing compound, wherein a surface of the carbon film layer is partially or completely covered with the coating layer.
15. The anode active material according to claim 14, wherein the metal oxygen-containing compound is a composite oxide of a metal and phosphorus.
16. The negative active material of claim 15, wherein the metal comprises one or more of lithium, titanium, magnesium, aluminum, zirconium, calcium, and zinc.
17. An electrode comprising the negative active material according to any one of claims 1 to 16.
18. A battery comprising the electrode of claim 17.
19. A method of preparing a negative active material for a battery, comprising the steps of:
coating a carbon film layer on the surface of the silicon oxide compound particles;
carrying out corrosion pore-forming on the silicon oxide compound particles coated with the carbon film layer to enable the silicon oxide compound particles coated with the carbon film layer to form a structure comprising an inner core and a porous shell layer; wherein the surface of the porous shell layer is partially or completely covered by the carbon film layer;
and carrying out lithium doping on the silicon oxide compound particles subjected to the pore forming by corrosion.
20. The method of claim 19, further comprising:
and forming a coating layer comprising an organic compound and/or a metal oxygen-containing compound on the surface of the carbon film layer.
21. A method of preparing a negative active material for a battery, comprising the steps of:
coating a carbon film layer on the surface of the silicon oxide compound particles;
performing lithium doping on the silicon oxide compound particles coated with the carbon film layer;
corroding the doped silicon oxide compound particles to form pores, so that the doped silicon oxide compound particles form a structure comprising an inner core and a porous shell layer; wherein the surface of the porous shell layer is partially or completely covered by the carbon film layer.
22. The method of claim 21, further comprising:
and forming a coating layer comprising an organic compound and/or a metal oxygen-containing compound on the surface of the carbon film layer.
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CN112018367A (en) * 2020-10-30 2020-12-01 安普瑞斯（南京）有限公司 Negative electrode active material for battery, preparation method of negative electrode active material, battery negative electrode and battery
CN112968152A (en) * 2021-01-29 2021-06-15 深圳市德方纳米科技股份有限公司 Silicon-based negative electrode material, preparation method thereof and lithium ion battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023124603A1 (en) * 2021-12-28 2023-07-06 博赛利斯（南京）有限公司 Negative electrode active material and preparation method therefor, electrode, and battery
CN114784233A (en) * 2022-03-02 2022-07-22 安普瑞斯（南京）有限公司 Negative electrode active material and preparation method and application thereof
WO2023165415A1 (en) * 2022-03-02 2023-09-07 博赛利斯（南京）有限公司 Negative electrode active material, preparation method therefor and application thereof

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