CN108054355B - Foamed silicon powder, preparation method thereof and lithium ion battery - Google Patents

Foamed silicon powder, preparation method thereof and lithium ion battery Download PDF

Info

Publication number
CN108054355B
CN108054355B CN201711267352.3A CN201711267352A CN108054355B CN 108054355 B CN108054355 B CN 108054355B CN 201711267352 A CN201711267352 A CN 201711267352A CN 108054355 B CN108054355 B CN 108054355B
Authority
CN
China
Prior art keywords
powder
silicon
tin
magnesium
magnesium alloy
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201711267352.3A
Other languages
Chinese (zh)
Other versions
CN108054355A (en
Inventor
王振宇
朱凌云
何旻雁
刘鑫雨
赵霞妍
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Guilin Electrical Equipment Scientific Research Institute Co Ltd
Original Assignee
Guilin Electrical Equipment Scientific Research Institute Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Guilin Electrical Equipment Scientific Research Institute Co Ltd filed Critical Guilin Electrical Equipment Scientific Research Institute Co Ltd
Priority to CN201711267352.3A priority Critical patent/CN108054355B/en
Publication of CN108054355A publication Critical patent/CN108054355A/en
Application granted granted Critical
Publication of CN108054355B publication Critical patent/CN108054355B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • 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
    • H01M4/36—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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Nanotechnology (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Silicon Compounds (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses foamed silicon powder for a lithium ion battery cathode and a preparation method thereof. The preparation method of the foamed silicon powder comprises the following steps: coating a tin-bismuth alloy layer on the surface of the silicon-magnesium alloy powder; carrying out solid-phase diffusion heat treatment on the silicon-magnesium alloy powder coated with the tin-bismuth alloy layer to promote the reaction and combination of tin and bismuth metals in the coating layer and magnesium; carrying out oxidation treatment on the silicon-magnesium alloy powder subjected to solid phase diffusion heat treatment; and carrying out acid washing on the silicon-magnesium alloy powder subjected to oxidation treatment to remove tin, bismuth and magnesium, and carrying out ball milling and calcination in a medium containing carbon organic matters to obtain the foam silicon powder with the microporous structure and the surface containing the carbon conductive layer. The safety risk that magnesium powder dust is easy to catch fire and explode in a workshop in the prior art is overcome, the method is suitable for industrial mass production, the foamed silicon powder is of a microporous structure, the micropores are uniform in gaps, and the whole oxygen content of the powder is lower than 5%; the lithium iron phosphate cathode material has good conductivity and high first charge-discharge coulombic efficiency.

Description

Foamed silicon powder, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of battery material preparation, and relates to foamed silicon powder, a preparation method thereof and a lithium ion battery.
Background
Because silicon has more than ten times higher theoretical specific capacity than graphite negative electrode (the theoretical specific capacity value of silicon is 4200mAh/g), the utilization of silicon to replace the graphite negative electrode which is commonly used at present has become the target of the research of the high-energy density power battery. Silicon has the following disadvantages in use as a negative electrode: the volume expansion is large, and silicon particles are easy to break and pulverize; the first charge-discharge coulomb efficiency is low; the impedance is high; in view of the above disadvantages, a series of improved methods have been proven effective, such as reducing the cracking of bulk silicon by using nano-scale silicon particles, alleviating the volume expansion during charging by using porous silicon particles, improving the conductivity of silicon by coating carbon layer on the surface, and so on. On the basis of the research results, the preparation method of the porous silicon powder composed of nano silicon crystals has become a hot research point of battery materials.
The method for preparing the nano silicon powder comprises a high-energy ball milling method, a plasma heating evaporation condensation method, a chemical method and the like. The high-energy ball milling method is suitable generally, but the preparation of the nano silicon powder is time-consuming, and the porous structure on the surface of the powder is difficult to form. The plasma heating evaporation condensation method has complex equipment, and the selection of raw materials and the selection of subsequent process treatment processes also have certain limitations, such as: in some researches, although the prepared nano silicon primary particles have high sphericity, the spherical nano silicon is difficult to combine to form secondary polymerized silicon particles with a large number of gaps, so that the subsequent process treatment is not facilitated; in some researches, the specific surface area of the prepared nano silicon powder is large, but the raw material cost is high when the nano silicon powder is prepared by utilizing silane. The problem of environmental pollution caused by chemical reagents in the preparation of the nano silicon powder by a chemical method is solved, the research on the preparation of the nano silicon by treating the mixture of silicon dioxide and silicon by hydrofluoric acid is carried out, and the used hydrofluoric acid has high corrosivity, is difficult to operate and has difficulty in solving the problem of environmental pollution.
In the methods for preparing porous silicon powder, the silicon powder prepared by some methods has the defects of large silicon particles, larger primary particle size and poorer uniformity; some methods use a large amount of magnesium powder in the process of synthesizing the silicon-magnesium alloy powder, and the production process needs to have strict environmental control means such as helium protection to reduce the explosion risk of the magnesium powder; in the process of magnesium removal treatment, the temperature is often higher than the ignition point of magnesium, so that magnesium is easy to catch fire, burn and oxidize, the whole powder is subjected to high-temperature spontaneous combustion and overburning, and silicon oxidation and silicon particle rapid growth are caused, so that the process for industrially producing the porous nano silicon powder by using the method is difficult to control, and particularly the granularity of the nano silicon powder is difficult to control; a method for decomposing silicon-magnesium alloy powder by utilizing a metal chloride molten salt medium for long-time heat preservation (10-15 h) and then obtaining porous silicon by hydrochloric acid pickling is also researched, the method eliminates the ignition and combustion risks of magnesium in industrial production, but the process requires long-time heat preservation and has the problem of low powder preparation efficiency.
Disclosure of Invention
Technical problem to be solved
The disclosure provides a preparation method of foamed silicon powder, a negative electrode material containing the foamed silicon powder and a lithium ion battery, and aims to at least partially solve the technical problems.
(II) technical scheme
According to one aspect of the present disclosure, there is provided a method for preparing a foamed silicon powder, comprising: coating a tin-bismuth alloy layer on the surface of the silicon-magnesium alloy powder; carrying out solid-phase diffusion heat treatment on the silicon-magnesium alloy powder coated with the tin-bismuth alloy layer to promote the reaction and combination of tin and bismuth metals in the coating layer and magnesium; carrying out oxidation treatment on the silicon-magnesium alloy powder subjected to solid phase diffusion heat treatment; and carrying out acid washing on the silicon-magnesium alloy powder subjected to oxidation treatment to remove tin, bismuth and magnesium, and carrying out ball milling and calcination in a medium containing carbon organic matters to obtain the foam silicon powder with the microporous structure and the surface containing the carbon conductive layer.
In some embodiments of the present disclosure, a method for coating a tin-bismuth alloy layer on a surface of a silicon-magnesium alloy powder includes: mixing silicon-magnesium alloy powder with mixed powder of metal tin powder and bismuth powder or tin-bismuth alloy powder, and coating by adopting a mechanical ball milling mode; or mixing silicon-magnesium alloy powder with mixed powder of metal tin powder and bismuth powder or tin-bismuth alloy powder, loading the mixed powder into a heat treatment furnace with a stirring device, and mechanically stirring and heating the mixed powder to realize coating; or mixing silicon-magnesium alloy powder with mixed powder of metal tin powder and bismuth powder or tin-bismuth alloy powder, and coating by adopting a mechanical ball milling mode; and loading the mixed powder subjected to the mechanical ball milling into a heat treatment furnace with a stirring device, and promoting further coating by mechanically stirring and heating the mixed powder.
In some embodiments of the present disclosure, the tin in the tin-bismuth alloy is 1-20% by mass; in the silicon-magnesium alloy, the mass percent of silicon is 30-35%.
In some embodiments of the present disclosure, the temperature of the solid phase diffusion heat treatment is 250-350 ℃.
In some embodiments of the present disclosure, the oxidation treatment is performed in an oxygen-nitrogen mixed gas having an oxygen content of 5-20% by volume, and the temperature of the treatment is 250-350 ℃.
In some embodiments of the present disclosure, acid washing the silicon-magnesium alloy powder after the oxidation treatment to remove tin, bismuth, and magnesium, ball milling in a carbon-containing organic medium, and calcining comprises: acid washing the oxidized silicon-magnesium alloy powder with hydrochloric acid and/or nitric acid in the ratio of 1 to remove oxides and metal impurities, repeatedly washing the silicon-magnesium alloy powder with deionized water to neutrality, and drying the silicon-magnesium alloy powder to prepare original foamed silicon powder; ball-milling the obtained original foam silicon powder in a medium containing carbon organic matters to obtain powder slurry; and drying the powder slurry, and calcining at high temperature in the atmosphere of nitrogen to obtain the carbon coating layer.
In some embodiments of the present disclosure, the carbon-containing organic medium is selected from at least one of: asphalt acetone solution, asphalt tetrahydrofuran solution, polyvinyl alcohol aqueous solution and PI/NMP solution.
According to another aspect of the present disclosure, there is provided a foamed silicon powder, which is a microporous structure with a carbon conductive layer on the surface, and has a micropore size of: 3nm-500 nm; the primary particle size of the silicon powder is as follows: 5nm-1000 nm.
In some embodiments of the present disclosure, the primary particle size of the foamed silicon powder is: 10nm-800 nm; and/or the specific surface area of the foamed silicon powder is as follows: 20m2/g-200m2/g。
According to yet another aspect of the present disclosure, there is provided a lithium ion battery comprising a negative electrode material prepared from the foamed silicon powder disclosed in any of the above.
(III) advantageous effects
According to the technical scheme, the foamed silicon powder, the preparation method thereof and the lithium ion battery provided by the disclosure have the following beneficial effects:
the tin-bismuth alloy with the melting point lower than the burning point of magnesium is utilized to form a coating layer on the surface of the silicon-magnesium alloy powder particles, so that the risk of surface oxidation ignition of the silicon-magnesium alloy powder is reduced; the diffusion reaction of the tin-bismuth alloy coating layer and magnesium is promoted through solid-phase diffusion alloying to form tin-magnesium and bismuth-magnesium metal compounds, the problem that the processed powder is over-burnt due to spontaneous combustion of the processed powder caused by magnesium ignition in the heat treatment process is solved, and the production efficiency is greatly improved; the controllable slow oxidation of magnesium and the controlled growth of silicon nanocrystals are realized by combining a low-oxygen oxidation process, so that the problems of the rapid oxidation and the violent combustion of magnesium and the defect of abnormal growth of silicon particles caused by the heat generated by the combustion of magnesium are solved; the method adopts the intermediate frequency vacuum smelting technology, overcomes the safety risk that workshop magnesium powder dust is easy to catch fire and explode in the prior art, is suitable for industrial batch production, and the prepared foam-shaped silicon powder has a microporous structure, a carbon conductive layer is arranged on the surface of the foam-shaped silicon powder, the microporous gaps are uniform, the crystallinity of silicon particles is high, the integral oxygen content of the powder is lower than 5 percent, and the porous silicon powder is superior to the porous silicon powder prepared by other prior art; the lithium ion battery anode material has good conductivity and high first charge-discharge coulombic efficiency when used in the anode material of the lithium ion battery.
Drawings
FIG. 1 is a flow chart of a method for preparing a foamed silicon powder according to an embodiment of the present disclosure.
FIG. 2 is an SEM picture of a foamed silicon powder containing a microporous structure made according to an embodiment of the disclosure.
FIG. 3 is an X-ray diffraction pattern of a foamed silicon powder prepared according to an embodiment of the present disclosure.
Detailed Description
In the present disclosure, the primary particle size refers to a single silicon particle size.
The invention provides a foamed silicon powder and a preparation method thereof, and a lithium ion battery, wherein a medium-frequency vacuum smelting technology is adopted, the safety risk that workshop magnesium powder dust is easy to catch fire and explode in the prior art is overcome, the foamed silicon powder is suitable for industrial batch production, the prepared foamed silicon powder is of a microporous structure, a carbon conductive layer is arranged on the surface of the foamed silicon powder, the microporous gaps are uniform, the crystallinity of silicon particles is high, the integral oxygen content of the powder is lower than 5%, and the foamed silicon powder is superior to porous silicon powder prepared by other prior arts; the lithium ion battery anode material has good conductivity and high first charge-discharge coulombic efficiency when used in the anode material of the lithium ion battery.
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
In a first exemplary embodiment of the present disclosure, a method of preparing a foamed silicon powder is provided.
FIG. 1 is a flow chart of a method for preparing a foamed silicon powder according to an embodiment of the present disclosure.
Referring to fig. 1, the method for preparing the foamed silicon powder of the present disclosure includes:
step S102: preparing silicon-magnesium alloy powder;
the step further comprises the sub-steps of:
sub-step S102 a: casting a silicon-magnesium alloy ingot by adopting an intermediate-frequency vacuum smelting technology;
the method comprises the following steps of (1) adopting a conventional intermediate frequency vacuum smelting method, using a graphite crucible as a smelting crucible, melting silicon blocks and magnesium blocks in a determined proportion in an argon atmosphere, adding metal magnesium blocks step by step according to the proportion that the finally formed silicon-containing mass percentage is 30-35%, controlling the temperature of silicon-magnesium alloy melt to be more than 1100 ℃, and pouring silicon-magnesium alloy ingots;
the silicon-magnesium alloy is prepared by preparing Mg2The silicon-magnesium alloy containing about 35% by mass of silicon is easily brittle, and the silicon-magnesium alloy is selected according to the proportion so as to facilitate crushing and powdering of the alloy;
sub-step S102 b: crushing, sieving and grading the cast silicon-magnesium alloy ingot under the protection of atmosphere to obtain silicon-magnesium alloy powder;
the silicon-magnesium alloy powder obtained in this step has a certain particle size, which is related to the mesh size of the sieve, i.e. the mesh size, and the mesh size of the sieve is selected according to the actual required particle size.
In this embodiment, the specific implementation process of step S102 includes: selecting a small intermediate frequency vacuum smelting furnace, preparing silicon and magnesium blocks according to the proportion that the smelting graphite crucible is used for proportioning according to the capacity of a smelting graphite crucible, 1kg of the proportioning of each furnace and the mass percent of silicon contained in the silicon-magnesium alloy is 30-35%, firstly melting the silicon and a small amount of massive magnesium in the proportioning under the argon atmosphere, adding the rest metal magnesium blocks step by step while controlling the temperature of the molten liquid at 1100-1200 ℃ in the smelting process, and finally, after preserving the heat for 2-5 minutes, pouring into a cast iron casting mold preheated at 300 ℃ in the presence of 250-300 ℃ to obtain a silicon-magnesium alloy ingot; and taking out the cooled silicon-magnesium alloy ingot, coarsely crushing the silicon-magnesium alloy ingot by using a jaw crusher in a dry air atmosphere until the granularity is less than 5mm, vibrating and ball-milling the silicon-magnesium alloy ingot in a nitrogen atmosphere, and sieving and grading the silicon-magnesium alloy ingot.
Step S104: coating a tin-bismuth alloy layer on the surface of the silicon-magnesium alloy powder;
in this step, a tin-bismuth alloy layer which is relatively stable in air containing water and has a melting point lower than the ignition point of magnesium is coated on the surface of the prepared silicon-magnesium alloy powder with a certain particle size, and the coating method can be selected from but not limited to: powder mixing mechanical alloying method and/or molten metal stirring cladding method at certain temperature;
selecting 1-20 mass percent of tin content corresponding to the tin-bismuth alloy with the melting point lower than the magnesium burning point and the balance of bismuth, wherein the melting point of the alloy is lower than 275 ℃, and coating silicon-magnesium alloy powder particles with the tin-bismuth alloy with the melting point lower than the magnesium burning point so as to reduce the risk of ignition and spontaneous combustion of the silicon-magnesium alloy powder; the powder mixing mechanical alloying method and/or the molten metal stirring cladding method can adapt to various process conditions.
In this embodiment, the specific implementation process of step S104 includes: selecting the obtained silicon-magnesium alloy powder with the granularity of 20-300 meshes, preferably selecting a proper amount of silicon-magnesium alloy powder with the granularity of 80-200 meshes, determining the weight of the coated metal powder according to the proportion of 1: 3-1: 5, wherein the coated metal powder consists of 1-20 percent (mass percent) of metallic tin powder and the balance of bismuth powder, and can also select 1-20 percent (mass percent) of tin-bismuth alloy powder; the silicon-magnesium alloy powder and the coating metal powder are put into a stainless steel tank with the diameter of 185mm, hard alloy balls with the diameter of 6-12mm which is 2-4 times of the weight of the mixed powder are added, nitrogen or argon is filled for protection and sealing, and a common rolling ball mill is adopted for mixing and ball milling for 12-48 hours. In other embodiments, the silicon-magnesium alloy powder and the metallic tin powder, or the bismuth powder, or the tin-bismuth alloy powder can be fully mixed and coated by using a well-known high-energy vibration ball milling method under the conditions of proper ball-to-material ratio and the like.
Wherein, more preferably, 200 grams of silicon-magnesium alloy powder with the grain size of 40-100 meshes is selected, 800 grams of coating metal powder is prepared according to the proportion of 1: 4, the coating metal powder is preferably prepared by mixing 50 grams of metal tin powder with the grain size of less than 100 meshes and 750 grams of metal bismuth powder, the silicon-magnesium alloy powder and the coating metal powder are put into a stainless steel tank with the diameter of 185mm, hard alloy balls with the weight of 2-4 times of the weight of the mixed powder are added, the diameter of the hard alloy balls is 6-12mm, nitrogen or argon is filled for protection and sealing, and the mixture is ball-milled for 56 hours by adopting a common rolling ball mill.
In this embodiment, in order to improve the integrity of the coating layer, the mixed powder after ball milling is selected and placed in a heat treatment furnace with a stirring device, the temperature in the furnace is controlled to be above the tin-bismuth eutectic point, i.e. the temperature is 250-.
Wherein the temperature in the heat treatment furnace is controlled to be 250-350 ℃, preferably 270-300 ℃, and the powder mixture is stirred at a stirring speed of about 100 revolutions per minute to promote coating so as to form a compact coating layer on the surface of the silicon-magnesium alloy powder.
Step S106: carrying out solid-phase diffusion heat treatment on the silicon-magnesium alloy powder coated with the tin-bismuth alloy layer;
in this step, the atmosphere of the solid phase diffusion heat treatment is: vacuum or inert gas atmosphere, wherein the inert gas comprises nitrogen or argon, the temperature of the solid phase diffusion heat treatment is higher than the temperature (139 ℃) of the tin-bismuth alloy eutectic point of the coating layer, the temperature of the solid phase diffusion heat treatment in the embodiment is 250-350 ℃, and the heat preservation time is 0.25-2.0 h;
the solid phase diffusion heat treatment process with the temperature of 250-350 ℃ is carried out under vacuum or inert gas, so that the reaction combination of tin and bismuth metals in the coating layer and magnesium is promoted, and a relatively stable tin-magnesium-bismuth-magnesium alloying coating layer with high ignition point is formed on the surface of the powder, so that the spontaneous combustion risk of the powder caused by the ignition of the metal magnesium is reduced in the process;
in this embodiment, the specific implementation process of step S106 includes: loading the obtained coating powder into a tubular vacuum furnace, maintaining the vacuum degree below 200Pa, selecting the temperature of the vacuum furnace to be 250-350 ℃, preferably the temperature of the vacuum furnace to be 300-330 ℃, and carrying out solid phase diffusion heat treatment for 0.25-2.0h, preferably 1-1.5 h to form a diffusion alloy layer; the diffusion heat treatment in this step can also be performed in a vacuum furnace filled with an inert gas such as nitrogen or argon in a protective atmosphere.
Step S108: carrying out oxidation treatment on the silicon-magnesium alloy powder subjected to solid phase diffusion heat treatment;
in the step, the low-oxygen oxidation treatment is carried out in oxygen-nitrogen mixed gas with the oxygen content volume ratio of 5-20%, the treatment temperature is 250-350 ℃, and the heat preservation time is 5-60 minutes;
the powder after the solid-phase diffusion heat treatment is subjected to heat preservation treatment in oxygen-nitrogen mixed gas with low oxygen pressure and low oxygen content, and the metal of the alloy coating layer, such as tin, bismuth, tin-magnesium alloy and bismuth-magnesium alloy, is slowly oxidized to realize controllable oxidation speed, so that the defects that powder is combusted due to rapid oxidation of magnesium and primary silicon grains in silicon powder grow abnormally due to heat generated by combustion of magnesium in the prior art are overcome;
in this embodiment, the specific implementation process of step S108 includes: and (3) filling the powder after the solid phase diffusion heat treatment into a tubular vacuum furnace, introducing oxygen-nitrogen mixed gas with the oxygen content volume ratio of 5-20%, preferably oxygen-nitrogen mixed gas with the oxygen content of 10%, maintaining the pressure in the furnace at 0.05-0.1MPa, and keeping the temperature in the furnace at 250-350 ℃, preferably at 300-330 ℃, for 30-180 minutes to complete the low-oxygen oxidation treatment, wherein the time is preferably 30 minutes.
Step S110: acid washing the oxidized silicon-magnesium alloy powder to remove tin, bismuth and magnesium, ball milling in a medium containing carbon organic matters and calcining to obtain foam silicon powder with a microporous structure and a carbon conducting layer on the surface;
in the step, the silicon-magnesium alloy powder after the low-oxygen oxidation treatment is subjected to acid washing, the acid washing solution is hydrochloric acid and/or nitric acid with the ratio of 1: 1, the soaking treatment time is 1-5 hours, so as to remove oxides and metal impurities, wherein the oxides and the metal impurities comprise: metal oxides of the alloy cladding, such as tin, bismuth and tin-magnesium, bismuth-magnesium alloys, and residual metal impurities that are not fully oxidized; repeatedly washing the silicon powder by deionized water until the silicon powder is neutral, and drying the silicon powder to prepare original foam silicon powder; then, performing medium ball milling on the obtained foamed silicon powder in at least one of a pitch acetone solution, a pitch tetrahydrofuran solution, a polyvinyl alcohol aqueous solution and a polyimide/NMP solution for 1-2 hours to obtain powder slurry; in some embodiments, the media ball milling employs a ratio of zirconia balls to ball material; the ball milling time can be adjusted according to actual needs; drying the powder slurry, and calcining at high temperature in the atmosphere of nitrogen to obtain foam silicon powder with a microporous structure and a carbon conductive layer on the surface; in some embodiments, the temperature of the high temperature calcination is less than 650 ℃.
In this embodiment, the specific implementation process of step S110 includes: soaking the powder after low-oxygen oxidation treatment in an excessive hydrochloric acid and/or nitric acid solution with the volume ratio of the powder to deionized water being 1: 1 for 5 hours to remove oxides and residual metal impurities which are not completely oxidized, and obtaining original foam silicon powder after multiple times of water washing, drying and sieving; carrying out medium ball milling crushing on the obtained original foam silicon powder under a proper zirconia ball-to-ball material ratio; and drying the powder slurry subjected to ball milling in an oven at the temperature of lower than 100 ℃, and then calcining and crushing the powder slurry at the temperature of 500-650 ℃ in a nitrogen atmosphere to obtain the foam silicon powder with the microporous structure shown in figure 2. Wherein, the ball milling medium adopts 5-10% polyvinyl alcohol aqueous solution by mass, the volume content of the silicon powder and the balls in the solution is adjusted to be not more than 80%, the ball milling time can be adjusted according to the requirement, generally not more than 2 hours, in this embodiment, 1 hour; in order to obtain a stable carbon conductive layer on the surface of the final foamed silicon powder, solutions containing organic carbon sources such as pitch acetone solution, pitch tetrahydrofuran solution, and polyimide/NMP solution can also be used.
It should be noted that the preparation method of the foamed silicon powder of the present disclosure is not limited to the melting, mixing and ball milling, heat treatment, and acid washing methods described above, other methods known to those skilled in the art may also be used, the ball milling medium during the powder crushing process is not limited to the pitch acetone solution, the pitch tetrahydrofuran solution, the polyvinyl alcohol aqueous solution, and the polyimide/NMP solution, and carbon-containing organic substances known to those skilled in the art, including organic polymer compounds, may also be added to obtain a certain carbon conductive layer on the surface of the silicon powder.
In a second exemplary embodiment of the present disclosure, a method for preparing a foamed silicon powder is provided, which differs from the first embodiment in that: the parameter settings of step S104 'and step S108' are different from those of step S104 and step S108.
In this embodiment, the implementation process of step S104' includes: 200 g of silicon-magnesium alloy powder with the granularity of 100-200 meshes is optimized, 1000 g of coating metal powder is prepared according to the proportion of 1: 5, the coating metal powder is preferably prepared by mixing 100 g of metal tin powder with the granularity of less than 100 meshes and 900 g of metal bismuth powder, the silicon-magnesium alloy powder and the coating metal powder are put into a stainless steel tank with the diameter of 185mm, hard alloy balls with the weight 2-4 times of the weight of the mixed powder are added, the diameter of the hard alloy balls is selected from 6-12mm, nitrogen or argon is filled for protection and sealing, and a common rolling ball mill is adopted for mixing and ball milling for 48 hours;
in this embodiment, the specific implementation process of step S108' includes: and (3) filling the powder after the diffusion heat treatment into a tubular vacuum furnace, introducing oxygen-nitrogen mixed gas with the oxygen content volume ratio of 5-20%, preferably with the oxygen content of 15%, maintaining the gas pressure in the furnace at 0.05MPa, the temperature in the furnace at 350 ℃ and preferably at 330 ℃ and 300 ℃ for 120 minutes, and preserving the temperature for completing the low-oxygen oxidation treatment of the coated powder.
In a third exemplary embodiment of the present disclosure, there is provided a method for preparing a foamed silicon powder, which differs from the first embodiment in that: the parameter settings of step S104 "and step S108" are different from those of step S104 and step S108.
In this embodiment, the implementation process of step S104 ″ includes: 200 g of silicon-magnesium alloy powder with the granularity of 200-300 meshes is optimized, 1000 g of coating metal powder is prepared according to the proportion of 1: 5, the coating metal powder is preferably prepared by mixing 200 g of metal tin powder with the granularity of less than 100 meshes and 800 g of metal bismuth powder, the silicon-magnesium alloy powder and the coating metal powder are put into a stainless steel tank with the diameter of 185mm, hard alloy balls with the weight 2-4 times of the weight of the mixed powder are added, the diameter of the hard alloy balls is selected from 6-12mm, nitrogen or argon is filled for protection and sealing, and a common rolling ball mill is adopted for mixing and ball milling for 36 hours;
in this embodiment, the implementation process of step S108 ″ includes: and (3) putting the obtained powder after the diffusion heat treatment into a tubular vacuum furnace, introducing oxygen-nitrogen mixed gas with the oxygen content volume ratio of 5-20%, preferably 5%, maintaining the gas pressure in the furnace at about 0.1MPa, the temperature in the furnace at 250-350 ℃, preferably at 300-330 ℃, and preserving the temperature for 60 minutes to finish the low-oxygen-content oxidation treatment of the coated powder.
In order to illustrate the beneficial effects of the preparation method of the foamed silicon powder disclosed by the disclosure, the foamed silicon powder prepared by the preparation method disclosed by the embodiment is subjected to SEM characterization and XRD analysis, and the specific surface area of the foamed silicon powder is determined by a nitrogen adsorption method; and experiments are carried out by adopting the preparation method of the porous silicon powder in the prior art, and the prepared porous silicon powder is taken as a comparative example to comprehensively evaluate the preparation method disclosed by the disclosure.
FIG. 2 is an SEM picture of a foamed silicon powder containing a microporous structure made according to an embodiment of the disclosure. FIG. 3 is an X-ray diffraction pattern of a foamed silicon powder prepared according to an embodiment of the present disclosure. Table 1 shows the primary particle size and specific surface area of the foamed silicon powders prepared in the three examples and the porous silicon powders prepared in the comparative example.
The SEM result of the foamed silicon powder ① prepared by the preparation method shown in the first example is shown in fig. 2, and it can be seen that the prepared foamed silicon powder has uniform voids and one-time particleThe particle size of the particles is less than 120 nm; as shown in fig. 3, the characteristic broad peak of the amorphous phase (mainly silicon dioxide) does not appear in the X-ray spectrum, and is basically a sharp peak corresponding to each crystal orientation of silicon, so that the silicon particles of the foamed silicon powder have good crystallinity; the specific surface area measured by nitrogen adsorption was about 19m2(iv)/g, as shown in Table 1.
The foamed silicon powder ② prepared in the second example has uniform voids and good crystallinity, and no significant amorphous phase of silica, similar to the foamed silicon powder ① of the first example, and SEM picture and XRD results thereof do not show that the foamed silicon powder has a primary particle size of less than 100nm and a specific surface area of about 22m as measured by nitrogen adsorption2(iv)/g, as shown in Table 1.
The foamed silicon powder ③ prepared in the third example has uniform voids and good crystallinity, and no significant amorphous phase of silica, similar to the foamed silicon powder ① of the first example, and SEM picture and XRD results thereof do not show that the foamed silicon powder has a primary particle size of less than 150nm and a specific surface area of about 17m as measured by nitrogen adsorption2(iv)/g, as shown in Table 1.
For comparison with examples, the preparation of porous silicon powder was carried out according to the method for preparing porous silicon powder in the prior art, and the prepared porous silicon powder was taken as a comparative example.
In the comparative example, the method for preparing porous silicon powder includes:
(1) heating the mixed powder of silicon powder and magnesium powder to 1000-1100 ℃ under the protection of helium gas and preserving the heat for 3-4 hours to synthesize magnesium-silicon alloy powder;
(2) under the protection of argon, magnesium-silicon alloy powder with the particle size of 100-;
(3) taking the treated powder out of the pure bismuth melt bath at the temperature of 500-550 ℃, pouring the powder into an open stainless steel boat without argon protection, and firstly forming a small amount of yellow oxide, and then starting spontaneous combustion of the powder and expanding the powder to the whole powder;
(4) and pouring the self-ignited yellow powder into an excessive concentrated nitric acid solution for soaking for 5 hours to remove oxides and residual metal bismuth which is not completely oxidized, and washing, drying and sieving for multiple times to obtain the porous silicon powder of the comparative example.
According to the characteristics of SEM and XRD, the porous silicon powder prepared by the comparative example has good crystallinity, and no obvious amorphous phase of silicon dioxide appears; however, the porous silicon powder has a primary particle size of 50-300nm and a specific surface area of about 9m measured by nitrogen adsorption2See Table 1 for,/g.
TABLE 1 Primary particle size and specific surface area of the silicon powders of examples and comparative examples
Figure BDA0001494726270000101
In a fourth embodiment of the present disclosure, a negative electrode material containing foamed silicon powder is provided, and the foamed silicon powder is prepared by the following steps: reacting 5kg of Mg powder with 5kg of Si powder for 3 hours under the protection of helium at 1100 ℃, preparing MgSi alloy, and crushing the MgSi alloy; 1kg of 100-mesh MgSi powder with 200 meshes is placed in an excess pure bismuth molten bath, and the temperature is kept for 0.5h at 550 ℃ under the protection of helium; after the heat preservation is finished, putting the powder into air for self-combustion; and adding 1L of concentrated nitric acid into the powder after spontaneous combustion for corrosion, and filtering, washing and drying the obtained powder to obtain the foamed silicon powder.
In a fifth embodiment of the present disclosure, a lithium ion battery containing the above-described anode material is provided. The battery adopts the foamed silicon powder as an active substance, and the half-battery is prepared by mixing slurry according to the ratio of the active substance to the conductive agent to the adhesive of 8: 1. The capacity is 3789mAh/g, and the first charge-discharge coulombic efficiency is 82.17%.
In summary, embodiments of the present disclosure provide a preparation method of foamed silicon powder, and a negative electrode material and a lithium ion battery containing the same, in which a tin-bismuth alloy with a melting point lower than a magnesium ignition point is used to form a coating layer on the surface of silicon-magnesium alloy powder particles, so that the risk of surface oxidation ignition of the silicon-magnesium alloy powder is reduced; the diffusion reaction of the tin-bismuth alloy coating layer and magnesium is promoted through solid-phase diffusion alloying to form tin-magnesium and bismuth-magnesium metal compounds, the problem that the processed powder is over-burnt due to spontaneous combustion of the processed powder caused by magnesium ignition in the heat treatment process is solved, and the production efficiency is greatly improved; the controllable slow oxidation of magnesium and the controlled growth of silicon nanocrystals are realized by combining a low-oxygen oxidation process, so that the problems of the rapid oxidation and the violent combustion of magnesium and the defect of abnormal growth of silicon particles caused by the heat generated by the combustion of magnesium are solved; the method adopts the intermediate frequency vacuum smelting technology, overcomes the safety risk that workshop magnesium powder dust is easy to catch fire and explode in the prior art, is suitable for industrial batch production, and the prepared foam-shaped silicon powder has a microporous structure, a carbon conductive layer is arranged on the surface of the powder, the micropores have uniform gaps, the crystallinity of silicon particles is high, the integral oxygen content of the powder is lower than 5 percent, the specific surface area is large, and the method is superior to porous silicon powder prepared by other prior art; the lithium ion battery anode material has good conductivity and high first charge-discharge coulombic efficiency when used in the anode material of the lithium ion battery.
It is emphasized that the word "comprising" or "comprises", does not exclude the presence of elements or steps other than those listed in a claim. In addition, unless steps are specifically described or must occur in sequence, the order of the steps is not limited to that listed above and may be changed or rearranged as desired by the desired design. The embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e., technical features in different embodiments may be freely combined to form further embodiments.
Unless otherwise indicated, the numerical parameters set forth in the specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. In particular, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Generally, the expression is meant to encompass variations of ± 10% in some embodiments, 5% in some embodiments, 1% in some embodiments, 0.5% in some embodiments by the specified amount.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

Claims (10)

1. A preparation method of foamed silicon powder comprises the following steps:
coating a tin-bismuth alloy layer on the surface of the silicon-magnesium alloy powder;
carrying out solid-phase diffusion heat treatment on the silicon-magnesium alloy powder coated with the tin-bismuth alloy layer to promote the reaction and combination of tin and bismuth metals in the coating layer and magnesium;
carrying out oxidation treatment on the silicon-magnesium alloy powder subjected to solid phase diffusion heat treatment; and
and (3) carrying out acid washing on the silicon-magnesium alloy powder subjected to oxidation treatment to remove tin, bismuth and magnesium, and carrying out ball milling and calcination in a medium containing carbon organic matters to obtain the foam silicon powder with the microporous structure and the surface containing the carbon conductive layer.
2. The preparation method according to claim 1, wherein the method for coating the tin-bismuth alloy layer on the surface of the silicon-magnesium alloy powder comprises the following steps:
mixing silicon-magnesium alloy powder with mixed powder of metal tin powder and bismuth powder or tin-bismuth alloy powder;
coating the mixed powder by adopting a mechanical ball milling mode; or
The mixed powder is put into a heat treatment furnace with a stirring device, and the coating is realized by mechanically stirring and heating the mixed powder; or
Coating the mixed powder by adopting a mechanical ball milling mode; and loading the mixed powder subjected to the mechanical ball milling into a heat treatment furnace with a stirring device, and promoting further coating by mechanically stirring and heating the mixed powder.
3. The production method according to claim 1, wherein:
in the tin-bismuth alloy, the mass percent of tin is 1-20%;
in the silicon-magnesium alloy, the mass percent of silicon is 30-35%.
4. The method as claimed in claim 1, wherein the temperature of the solid phase diffusion heat treatment is 250-350 ℃.
5. The production method according to claim 1, wherein the oxidation treatment is carried out in an oxygen-nitrogen mixed gas having an oxygen content of 5 to 20% by volume at a temperature of 250-350 ℃.
6. The preparation method according to claim 1, wherein the acid washing of the silicon-magnesium alloy powder after the oxidation treatment to remove tin, bismuth and magnesium, the ball milling in the medium containing carbon organic matter and the calcination comprises:
acid washing the oxidized silicon-magnesium alloy powder with hydrochloric acid and/or nitric acid in the ratio of 1 to remove oxides and metal impurities, repeatedly washing the silicon-magnesium alloy powder with deionized water to neutrality, and drying the silicon-magnesium alloy powder to prepare original foamed silicon powder;
ball-milling the obtained original foam silicon powder in a medium containing carbon organic matters to obtain powder slurry; and
and drying the powder slurry, and then calcining the powder slurry at high temperature in the atmosphere of nitrogen to obtain the carbon coating layer, wherein the high-temperature calcination temperature is 500-650 ℃.
7. The method of claim 6, wherein the carbon-containing organic medium is selected from at least one of: asphalt acetone solution, asphalt tetrahydrofuran solution, polyvinyl alcohol aqueous solution and PI/NMP solution.
8. A foamed silicon powder produced by the production method according to any one of claims 1 to 7, wherein the silicon powder has a microporous structure with a carbon conductive layer on the surface, and the micropore size is: 3nm-500 nm; the primary particle size of the silicon powder is as follows: 5nm-1000 nm.
9. The foamed silicon powder of claim 8, wherein:
the primary particle granularity of the foamed silicon powder is as follows: 10nm-800 nm; and/or
The specific surface area of the foamed silicon powder is as follows: 20m2/g-200m2/g。
10. A lithium ion battery comprising a negative electrode material prepared from the foamed silicon powder of claim 8 or 9.
CN201711267352.3A 2017-12-05 2017-12-05 Foamed silicon powder, preparation method thereof and lithium ion battery Active CN108054355B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201711267352.3A CN108054355B (en) 2017-12-05 2017-12-05 Foamed silicon powder, preparation method thereof and lithium ion battery

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201711267352.3A CN108054355B (en) 2017-12-05 2017-12-05 Foamed silicon powder, preparation method thereof and lithium ion battery

Publications (2)

Publication Number Publication Date
CN108054355A CN108054355A (en) 2018-05-18
CN108054355B true CN108054355B (en) 2020-01-17

Family

ID=62122291

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201711267352.3A Active CN108054355B (en) 2017-12-05 2017-12-05 Foamed silicon powder, preparation method thereof and lithium ion battery

Country Status (1)

Country Link
CN (1) CN108054355B (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102157731A (en) * 2011-03-18 2011-08-17 上海交通大学 Silicon and carbon compound anode material of lithium ion battery and preparation method of silicon and carbon compound anode material
CN102185128A (en) * 2011-04-02 2011-09-14 上海交通大学 Silicon carbon composite material and preparation method thereof
CN102208634A (en) * 2011-05-06 2011-10-05 北京科技大学 Porous silicon/carbon composite material and preparation method thereof
CN102709565A (en) * 2012-05-30 2012-10-03 力芯（青岛）新能源材料有限公司 Preparation method of lithium ion battery porous silicon carbon composite negative material
CN104975336A (en) * 2014-04-14 2015-10-14 微宏动力系统（湖州）有限公司 Preparation method of porous silicon used in lithium ion battery anode material

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102157731A (en) * 2011-03-18 2011-08-17 上海交通大学 Silicon and carbon compound anode material of lithium ion battery and preparation method of silicon and carbon compound anode material
CN102185128A (en) * 2011-04-02 2011-09-14 上海交通大学 Silicon carbon composite material and preparation method thereof
CN102208634A (en) * 2011-05-06 2011-10-05 北京科技大学 Porous silicon/carbon composite material and preparation method thereof
CN102709565A (en) * 2012-05-30 2012-10-03 力芯（青岛）新能源材料有限公司 Preparation method of lithium ion battery porous silicon carbon composite negative material
CN104975336A (en) * 2014-04-14 2015-10-14 微宏动力系统（湖州）有限公司 Preparation method of porous silicon used in lithium ion battery anode material

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Room-Temperature Solution Synthesis of Mesoporous Silicon for Lithium Ion Battery Anodes;Lin Sun et al;《Appl.Mater.Interfaces》;20171030;第9卷(第46期);全文 *

Also Published As

Publication number Publication date
CN108054355A (en) 2018-05-18

Similar Documents

Publication Publication Date Title
US6461766B1 (en) Hydrogen storage powder and process for preparing the same
CN105063457B (en) Nano-graphite compounded high-capacity RE-Mg-Ni-based hydrogen storage material and preparation method thereof
CN113948688B (en) Modified pre-lithiated silica composite material and preparation method and application thereof
CN111477849B (en) Preparation method of porous Si/SiC/C material and negative electrode material
CN113579246A (en) Preparation method of nano high-entropy alloy powder
CN113148947A (en) Rare earth alloy hydrogen storage material and preparation method thereof
CN108039467B (en) Spongy silicon powder, preparation method thereof and lithium ion battery applying spongy silicon powder
CN108011091B (en) Method for preparing ferrosilicon powder by coating magnesium-silicon-iron particles with indium-bismuth alloy and ferrosilicon powder
CN108039484B (en) Spongy silicon powder, preparation method thereof and lithium ion battery
CN108054355B (en) Foamed silicon powder, preparation method thereof and lithium ion battery
CN107790712B (en) Copper-aluminum-silicon alloy nano negative electrode material of lithium battery and preparation method thereof
CN108002389B (en) The method and silicon powder of zinc bismuth alloy coated Si magnesium granules preparation foam-like silicon powder
CN108039485B (en) Foam-like silicon powder is with preparation method and using its lithium ion battery
CN111101041A (en) Magnesium-yttrium-zinc hydrogen storage magnesium alloy and preparation method thereof
CN108017057B (en) The method and silicon powder of tin-indium alloy coated Si magnesium granules preparation foam-like silicon powder
CN116079066A (en) TaNbTiZr refractory high-entropy alloy spherical powder and preparation method thereof
CN107999781B (en) The method and ferrosilicon composite powder of zinc bismuth alloy cladding magnesium ferrosilicon particle preparation ferrosilicon powder
CN111375782B (en) Preparation method of iron-nickel-molybdenum soft magnetic powder
CN108011093A (en) Lithium occlusion releasable material, electrode, the manufacture method of lithium rechargeable battery and lithium occlusion releasable material
CN113881880A (en) High-capacity Gd-Mg-Ni-based composite hydrogen storage material doped with fluoride and preparation method thereof
CN111952569A (en) Silicon oxide-based negative electrode material for lithium ion battery and preparation method thereof
CN115852273B (en) Preparation method of nanocrystalline magnesium-based hydrogen storage alloy
CN117650238B (en) Method for preparing porous silicon-carbon composite material by direct magnesia reduction
CN107154481B (en) Hydrogen storage electrode alloy for Ni-MH battery and preparation method thereof
JPH06248306A (en) Production of hydrogen storage alloy powder

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant