CN112421047A - Method for improving multiplying power performance of silicon-based composite negative electrode of lithium battery - Google Patents

Method for improving multiplying power performance of silicon-based composite negative electrode of lithium battery Download PDF

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CN112421047A
CN112421047A CN202011369016.1A CN202011369016A CN112421047A CN 112421047 A CN112421047 A CN 112421047A CN 202011369016 A CN202011369016 A CN 202011369016A CN 112421047 A CN112421047 A CN 112421047A
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silicon
negative electrode
parts
based composite
lithium battery
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陈庆
廖健淞
司文彬
李钧
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Chengdu New Keli Chemical Science 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

Abstract

The invention relates to the field of lithium battery cathodes, and discloses a method for improving the rate capability of a silicon-based composite cathode of a lithium battery. The preparation method comprises the following preparation processes: (1) adding phenolic resin into absolute ethyl alcohol, uniformly stirring, then sequentially adding organic siloxane, a catalyst, an oxidant, a surfactant and a dilute hydrochloric acid aqueous solution, stirring to obtain sol, adding a cross-linking agent, curing and drying to obtain precursor gel powder; (2) and mixing and ball-milling the precursor gel powder and the carbon-based powder, then carrying out microwave heating treatment, carrying out carbonization reaction, then heating up for reduction reaction, cooling, washing and drying to obtain the silicon-based composite anode material with good rate capability. According to the invention, the catalyst and the oxidant are reduced to induce the negative electrode material to realize surface micro-oxidation in the carbonization process and form a nanowire structure, so that the obtained Si/SiOC/C composite negative electrode material has good rate capability, can relieve volume expansion and improves cycle performance.

Description

Method for improving multiplying power performance of silicon-based composite negative electrode of lithium battery
Technical Field
The invention relates to the field of lithium battery cathodes, and discloses a method for improving the rate capability of a silicon-based composite cathode of a lithium battery.
Background
In recent years, rapid development in the field of new energy power generation puts new requirements on matched energy storage systems. In the updating and upgrading of energy storage batteries, lithium ion batteries have become an important research field due to various advantages of the lithium ion batteries, and have been practically applied to a large number of energy storage projects to achieve certain results. The capacity of the lithium ion battery is determined by active lithium ions of a positive electrode material and the lithium-inserting and extracting capacity of a negative electrode material, and the stability of the positive electrode and the negative electrode in various environments determines the performance of the battery and even seriously affects the safety of the battery, so that the performance of the electrode determines the comprehensive performance of the lithium ion battery to a certain extent.
At present, the cathode material of the commercial lithium ion battery is mainly a graphite carbon cathode material, the theoretical specific capacity of the cathode material is only 372mAh/g, and the further development of the lithium ion battery is severely limited. The silicon-based material is the highest theoretical specific capacity in the current cathode materials, the formed alloy is LixSi (x = 0-4.4), the theoretical specific capacity is up to 4200mAh/g, and the silicon-based material is considered to be an alternative product of the carbon cathode material due to the low lithium intercalation potential, the low atomic mass, the high energy density and the high Li mole fraction in the Li-Si alloy.
In the carbon negative electrode material, the silicon-oxygen-based negative electrode material has a porous skeleton structure, and the structure also contains free carbon dispersed in the skeleton. The silicon-oxygen-based negative electrode material has high conductivity and thermal stability besides high tap density. However, similar to graphite-based negative electrode materials, silicon-based negative electrode materials have low rate performance due to the problems of self conductivity and compatibility with electrolyte. Therefore, the method has very important practical significance for improving the rate capability of the silicon-based negative electrode material of the lithium battery.
Chinese patent application No. 201610125508.3 discloses SiO for lithium ion battery cathodex-a method for preparing a C-CNT composite. The method comprises the steps of adding a carbon nano tube Conductive Network (CNT) and directly pouring the CNT into a culture dish to form a filmA novel silicon/carbon composite structure, the structure comprising: graphite skeleton material, amorphous silicon oxide SiOxAnd a carbon nanotube conductive mesh. However, the composite material silicon and carbon synthesized in this way are not combined through covalent bonds, and the volume expansion of the composite material silicon and carbon easily causes pulverization of the material.
Chinese patent application No. 201310741836.2 discloses a silicon/carbon composite negative electrode material for lithium ion batteries and a preparation method thereof. The material consists of a graphite framework material, an intermediate buffer layer SiOC material, carbon fiber and a silicon-containing material coated with carbon on the surface, wherein the silicon-containing material coated with carbon on the surface is combined with the graphite framework material through the buffer layer SiOC and the carbon fiber. However, this method does not solve the problems of poor electrolyte wettability and low rate capability.
According to the above, although the silicon-based negative electrode material for the lithium battery in the existing scheme has high tap density, conductivity and thermal stability, the rate capability of the silicon-based negative electrode material is poor due to poor compatibility with an electrolyte, and the development and application of the silicon-based negative electrode material are restricted.
Disclosure of Invention
The silicon-oxygen-based negative electrode material of the lithium battery which is widely applied at present has poor self-conductivity and poor electrolyte compatibility, so that the silicon-oxygen-based negative electrode material has the problem of low multiplying power.
The invention solves the problems through the following technical scheme:
a method for improving the multiplying power performance of a silicon-based composite negative electrode of a lithium battery comprises the following specific preparation processes:
(1) adding phenolic resin into absolute ethyl alcohol, magnetically stirring, sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, adding a cross-linking agent, curing the sol, and finally drying to obtain precursor gel powder;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, ball-milling, then carrying out microwave heating treatment on the ball-milled product under the protection of argon gas to enable the ball-milled product to carry out carbonization reaction, then heating up to carry out reduction reaction, naturally cooling to room temperature, finally washing and drying to obtain the silicon-based composite anode material with good rate capability.
The invention selects the organic siloxane as a silicon source of a negative electrode material, preferably the aromatic organic siloxane, and aims to ensure that after the siloxane is hydrolyzed and condensed, the structure of an organic matter can be kept stable by an aromatic group with a larger molecular weight, and the organic matter is carbonized to form more free carbon in the heat treatment process to promote the carbothermic reduction reaction. In the present invention, the organosiloxane of step (1) is an aromatic organosiloxane. As a further preferred mode of the present invention, the organosiloxane in the step (1) is phenyltriethoxysilane.
Lanthanum nitrate is selected as a catalyst, nitrate of low-melting-point metal is selected as an oxidant, cetyl trimethyl ammonium bromide is selected as a surfactant, and the lanthanum nitrate, the nitrate of the low-melting-point metal and the cetyl trimethyl ammonium bromide are added into a hydrolysis system, so that the gel is induced to form a nano linear structure in the curing and sintering processes. Preferably, the catalyst in the step (1) is lanthanum nitrate; the oxidant is nitrate of low-melting point metal; the surfactant is cetyl trimethyl ammonium bromide.
In a further preferred embodiment of the present invention, in the step (1), the oxidizing agent is one of aluminum nitrate, calcium nitrate, zinc nitrate, and cerium nitrate.
In the invention, the molar concentration of the dilute hydrochloric acid aqueous solution in the step (1) is preferably 0.05-0.5 mol/L.
Preferably, the crosslinking agent in step (1) is hexamethylenetetramine.
Preferably, the rotation speed of the magnetic stirring in the step (1) is 200-400 r/min, and the time is 15-30 min.
Preferably, the drying temperature in the step (1) is 105-115 ℃, and the time is 30-50 min.
According to the invention, firstly, the phenolic resin is added into absolute ethyl alcohol, then the organic siloxane, the catalyst, the oxidant, the surfactant and the dilute hydrochloric acid aqueous solution are sequentially added, the phenolic resin can coat the siloxane, the catalyst, the oxidant and the surfactant while the gel is generated through hydrolysis reaction, and finally the sol is solidified by using the cross-linking agent, so that precursor gel powder is obtained.
Preferably, in the step (1), the raw materials comprise, by weight, 300-400 parts of phenolic resin, 50-200 parts of absolute ethyl alcohol, 100-150 parts of organosiloxane, 1-5 parts of catalyst, 1-10 parts of oxidant, 1-2 parts of surfactant, 10-30 parts of dilute hydrochloric acid aqueous solution and 1-10 parts of cross-linking agent.
The invention selects the fibrous carbon powder as the carbon-based powder, not only can be used as a support framework of the composite negative electrode material to inhibit the volume expansion of the negative electrode material, but also can be used as a reducing agent to reduce the silicon dioxide generated by the organic siloxane into the nano silicon. Preferably, the carbon-based powder in the step (2) is fibrous carbon powder. In a further preferred embodiment of the present invention, the carbon-based powder is one of carbon fiber and carbon nanotube.
Preferably, the rotation speed of the ball milling in the step (2) is 200-300 r/min, and the time is 2-3 h.
Ball milling the precursor gel powder and fibrous carbon-base powder, microwave heating to carbonize phenolic resin while organic siloxane reaction to form SiOC and SiO2And the carbon thermal reduction oxidant and the catalyst generate a metal simple substance, and the metal simple substance is fused with SiO2Forming a solid solution in which the reactant is saturated with SiO2Precipitating in the form of nanowires. In the present invention, the temperature of the carbonization reaction in the step (2) is preferably 800 to 1000 ℃.
After the above carbonization reaction, the temperature is further raised to perform a reduction reaction in order to cause carbothermic reduction reaction between the precipitated SiO2 nanowire and the fibrous carbon-based powder to form SiO2Reducing the silicon dioxide into Si simple substance and CO, washing off metal silicate and silicon dioxide in the subsequent process to form an SiOC/Si/C composite structure,the problem of volume expansion of the negative electrode material can be effectively solved; in addition, the surface of the carbon-based material is slightly oxidized by siloxane, a catalyst and an oxidant in the solid-phase reaction process of carbothermic reduction, so that the roughness and porosity of the surface of the carbon-based material can be improved, the wettability of the negative electrode material and electrolyte is improved, and the rate capability is improved. Preferably, the temperature of the reduction reaction in the step (2) is 1500-1700 ℃.
Preferably, the washing in the step (2) is acid washing solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, and the washing times are 1-3 times.
Preferably, the pickling solution comprises 100-400 parts by weight of nitric acid, 20-50 parts by weight of hydrofluoric acid and 300-500 parts by weight of deionized water.
The lithium battery silicon-based composite negative electrode prepared by the method has good wettability with electrolyte and good rate capability, and can effectively inhibit volume expansion. Through tests, the button cell prepared from the prepared silicon-based composite negative electrode material has the first discharge capacity of 335.5-338.0 mAh/g and the first coulombic efficiency of 77.5-79.0% under the condition that the charge-discharge rate is 3C.
The invention provides a method for improving the multiplying power performance of a silicon-based composite negative electrode of a lithium battery, which comprises the steps of adding phenolic resin into an absolute ethyl alcohol solution, carrying out magnetic stirring, sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent to solidify the sol, and drying to obtain precursor gel powder; mixing and ball-milling precursor gel powder and carbon-based powder, then carrying out microwave heating treatment on a ball-milled product under the protection of argon, carrying out carbonization reaction, then heating up for reduction reaction, naturally cooling to room temperature, washing the product by using nitric acid, hydrofluoric acid and deionized water, and drying.
The invention provides a method for improving the multiplying power performance of a silicon-based composite negative electrode of a lithium battery, which has the outstanding characteristics and excellent effects compared with the prior art:
1. the method for improving the multiplying power performance of the silicon-based composite negative electrode of the lithium battery by realizing the micro-oxidation of the surface of the composite negative electrode material and forming the nanowire structure is provided.
2. The micro-oxidation of the surface of the carbon-based material is realized through the solid-phase reaction of carbothermic reduction, the porosity of the surface of the carbon-based material is improved, the wettability of the final silicon-carbon composite negative electrode material and electrolyte is further improved, and the rate capability of the negative electrode material is improved.
3. The Si/SiOC/C composite negative electrode material formed by the induction of the catalyst and the oxidant is in a nanowire structure, so that the volume expansion of the negative electrode material can be relieved better, and the cycle performance of the negative electrode material is improved.
Drawings
FIG. 1 is a process flow chart of the method for improving the rate capability of the silicon-based negative electrode of the lithium battery.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is aluminum nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.3 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 280r/min, and the time is 21 min; drying at 109 deg.C for 38 min;
the raw materials comprise, by weight, 360 parts of phenolic resin, 130 parts of absolute ethyl alcohol, 130 parts of organic siloxane, 2 parts of catalyst, 6 parts of oxidant, 1.6 parts of surfactant, 18 parts of dilute hydrochloric acid aqueous solution and 5 parts of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is carbon fiber; the rotation speed of the ball milling is 260r/min, and the time is 2.5 h; the temperature of the carbonization reaction is 880 ℃; the temperature of the reduction reaction is 1580 ℃; the washing is carried out by adopting a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 2 times, and the pickling solution comprises 220 parts by weight of nitric acid, 36 parts by weight of hydrofluoric acid and 410 parts by weight of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 1 are shown in table 1.
Example 2
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is calcium nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.1 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 250r/min, and the time is 25 min; drying at 108 deg.C for 45 min;
the raw materials comprise, by weight, 380 parts of phenolic resin, 150 parts of absolute ethyl alcohol, 110 parts of organic siloxane, 2 parts of catalyst, 3 parts of oxidant, 1.2 parts of surfactant, 15 parts of dilute hydrochloric acid aqueous solution and 3 parts of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is a carbon nano tube; the rotation speed of ball milling is 220r/min, and the time is 3 h; the temperature of the carbonization reaction is 850 ℃; the temperature of the reduction reaction is 1550 ℃; the washing is carried out by adopting a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 1 time, and the pickling solution comprises the raw materials of 200 parts by weight of nitric acid, 30 parts by weight of hydrofluoric acid and 450 parts by weight of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 2 are shown in table 1.
Example 3
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is zinc nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.4 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 350r/min, and the time is 20 min; drying at 112 deg.C for 35 min;
the raw materials comprise, by weight, 320 parts of phenolic resin, 100 parts of absolute ethyl alcohol, 140 parts of organic siloxane, 4 parts of catalyst, 8 parts of oxidant, 1.8 parts of surfactant, 25 parts of dilute hydrochloric acid aqueous solution and 8 parts of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is carbon fiber; the rotation speed of ball milling is 280r/min, and the time is 2 h; the temperature of the carbonization reaction is 950 ℃; the temperature of the reduction reaction is 1650 ℃; washing is carried out by using a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 3 times, and the pickling solution comprises 300 parts by weight of nitric acid, 40 parts by weight of hydrofluoric acid and 350 parts by weight of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 3 are shown in table 1.
Example 4
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is cerium nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.05 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 200r/min, and the time is 30 min; drying at 105 deg.C for 50 min;
the raw materials comprise, by weight, 400 parts of phenolic resin, 200 parts of absolute ethyl alcohol, 100 parts of organic siloxane, 1 part of catalyst, 1 part of oxidant, 1 part of surfactant, 10 parts of dilute hydrochloric acid aqueous solution and 1 part of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is a carbon nano tube; the rotation speed of ball milling is 200r/min, and the time is 3 h; the temperature of the carbonization reaction is 800 ℃; the temperature of the reduction reaction is 1500 ℃; washing is carried out by adopting a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 1 time, and the pickling solution comprises 100 parts by weight of nitric acid, 20 parts by weight of hydrofluoric acid and 500 parts by weight of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 4 are shown in table 1.
Example 5
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is aluminum nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.5 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 400r/min, and the time is 15 min; drying at 115 deg.C for 30 min;
the raw materials comprise, by weight, 300 parts of phenolic resin, 50 parts of absolute ethyl alcohol, 150 parts of organic siloxane, 5 parts of catalyst, 10 parts of oxidant, 2 parts of surfactant, 30 parts of dilute hydrochloric acid aqueous solution and 10 parts of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is carbon fiber; the rotation speed of ball milling is 300r/min, and the time is 2 h; the temperature of the carbonization reaction is 1000 ℃; the temperature of the reduction reaction is 1700 ℃; the washing is carried out by adopting a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 3 times, and the pickling solution comprises 400 parts by weight of nitric acid, 50 parts by weight of hydrofluoric acid and 500 parts by weight of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 5 are shown in table 1.
Example 6
(1) Firstly adding phenolic resin into absolute ethyl alcohol, magnetically stirring, then sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, then adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, then adding a cross-linking agent, solidifying the sol, and finally drying to obtain precursor gel powder; the organic siloxane is phenyl triethoxy silane; the catalyst is lanthanum nitrate; the oxidant is aluminum nitrate, calcium nitrate, zinc nitrate and cerium nitrate; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 3 mol/L; the cross-linking agent is hexamethylenetetramine; the rotating speed of magnetic stirring is 300r/min, and the time is 22 min; drying at 110 deg.C for 40 min;
the raw materials comprise, by weight, 350 parts of phenolic resin, 120 parts of absolute ethyl alcohol, 125 parts of organic siloxane, 3 parts of catalyst, 6 parts of oxidant, 1.5 parts of surfactant, 20 parts of dilute hydrochloric acid aqueous solution and 6 parts of cross-linking agent;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, performing ball milling, performing microwave heating treatment on a ball milling product under the protection of argon gas to perform carbonization reaction on the ball milling product, heating to perform reduction reaction, naturally cooling to room temperature, and finally washing and drying to obtain the silicon-based composite anode material with good rate capability; the carbon-based powder is a carbon nano tube; the rotation speed of the ball milling is 250r/min, and the time is 2.5 h; the temperature of the carbonization reaction is 900 ℃; the temperature of the reduction reaction is 1600 ℃; the washing is carried out by adopting a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water, wherein the washing frequency is 2 times, and the pickling solution comprises the following raw materials in parts by weight of 250 parts of nitric acid, 35 parts of hydrofluoric acid and 400 parts of deionized water.
The first discharge capacity and the first coulombic efficiency of the silicon-based composite negative electrode material prepared in the example 6 are shown in table 1.
Comparative example 1
Comparative example 1 lanthanum nitrate and an oxidant were not added, and other preparation conditions were the same as in example 6, and the first discharge capacity, the first coulombic efficiency, and the charge-discharge rate of the obtained silicon-based composite negative electrode material for a button cell are shown in table 1.
The performance index testing method comprises the following steps:
rate capability: the composite negative electrode material prepared in the embodiment and the comparative example, PVDF and Super-P are added into an NMP solvent according to the mass ratio of 8:1:1 to prepare slurry, the slurry is coated on the surface of copper foil to serve as a positive electrode, a lithium sheet serves as a negative electrode, 1mol/L lithium hexafluorophosphate and EC/DMC serve as electrolyte, celgard2400 serves as a diaphragm, the slurry is assembled into a CR2032 button cell, and the first discharge capacity and the first coulombic efficiency of the cell are respectively tested under the charge-discharge rate of 3C.
As can be seen from table 1: the button cell made of the silicon-based composite negative electrode prepared in the embodiment of the invention has obviously better discharge performance at high rate than that of the button cell made of the silicon-based composite negative electrode in the comparative example 1, because the composite performance of the negative electrode substrate is better through the induction of the catalyst in the embodiment 1, and meanwhile, the surface of the negative electrode substrate is slightly oxidized to generate a large number of pores, which is beneficial to the infiltration of electrolyte and the conduction of lithium ions, so the discharge capacity and the coulombic efficiency of the button cell are obviously improved at high rate. Comparative example 1 no lanthanum nitrate was added, which did not induce the precursor gel to form a nanofiber structure; the silicon dioxide cannot form a solid solution with a metal simple substance due to no addition of an oxidant, and precipitated silicon dioxide particles are spherical, so that the contact surface with carbon fibers is small, the carbothermic reduction process is difficult, and the formed cathode material has low silicon content, so that the rate performance of the obtained cathode material is poor.
Table 1:
Figure 575203DEST_PATH_IMAGE002

Claims (10)

1. a method for improving the multiplying power performance of a silicon-based composite negative electrode of a lithium battery is characterized by comprising the following specific preparation processes:
(1) adding phenolic resin into absolute ethyl alcohol, magnetically stirring, sequentially adding organic siloxane, a catalyst, an oxidant and a surfactant, adding a dilute hydrochloric acid aqueous solution, keeping mechanical stirring, fully reacting to obtain sol, adding a cross-linking agent, curing the sol, and finally drying to obtain precursor gel powder;
(2) mixing the precursor gel powder obtained in the step (1) with carbon-based powder, ball-milling, then carrying out microwave heating treatment on the ball-milled product under the protection of argon gas to enable the ball-milled product to carry out carbonization reaction, then heating up to carry out reduction reaction, naturally cooling to room temperature, finally washing and drying to obtain the silicon-based composite anode material with good rate capability.
2. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the organic siloxane in the step (1) is aromatic organic siloxane; the catalyst is lanthanum nitrate; the oxidant is nitrate of low-melting point metal; the surfactant is cetyl trimethyl ammonium bromide; the molar concentration of the dilute hydrochloric acid aqueous solution is 0.05-0.5 mol/L; the cross-linking agent is hexamethylenetetramine.
3. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the rotating speed of the magnetic stirring in the step (1) is 200-400 r/min, and the time is 15-30 min.
4. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the drying temperature in the step (1) is 105-115 ℃, and the time is 30-50 min.
5. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the raw materials in the step (1) comprise, by weight, 300-400 parts of phenolic resin, 50-200 parts of absolute ethyl alcohol, 100-150 parts of organic siloxane, 1-5 parts of catalyst, 1-10 parts of oxidant, 1-2 parts of surfactant, 10-30 parts of dilute hydrochloric acid aqueous solution and 1-10 parts of cross-linking agent.
6. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: and (3) the carbon-based powder in the step (2) is fibrous carbon powder.
7. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the rotation speed of the ball milling in the step (2) is 200-300 r/min, and the time is 2-3 h.
8. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the temperature of the carbonization reaction in the step (2) is 800-1000 ℃.
9. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: the temperature of the reduction reaction in the step (2) is 1500-1700 ℃.
10. The method for improving the rate capability of the silicon-based composite negative electrode of the lithium battery as claimed in claim 1, wherein: washing for 1-3 times by using a pickling solution obtained by mixing nitric acid, hydrofluoric acid and deionized water; the pickling solution comprises 100-400 parts by weight of nitric acid, 20-50 parts by weight of hydrofluoric acid and 300-500 parts by weight of deionized water.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113248257A (en) * 2021-05-12 2021-08-13 浙江大学 Co-continuous macroporous SiOC negative electrode material of lithium ion battery and preparation method thereof
CN113991092A (en) * 2021-09-27 2022-01-28 杭州电子科技大学 Preparation method of silicon electrode material

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113248257A (en) * 2021-05-12 2021-08-13 浙江大学 Co-continuous macroporous SiOC negative electrode material of lithium ion battery and preparation method thereof
CN113248257B (en) * 2021-05-12 2022-09-30 浙江大学 Co-continuous macroporous SiOC negative electrode material of lithium ion battery and preparation method thereof
CN113991092A (en) * 2021-09-27 2022-01-28 杭州电子科技大学 Preparation method of silicon electrode material

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