CN116230911A - High-power silicon-carbon negative electrode composite material and preparation method thereof - Google Patents

High-power silicon-carbon negative electrode composite material and preparation method thereof Download PDF

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CN116230911A
CN116230911A CN202310241127.1A CN202310241127A CN116230911A CN 116230911 A CN116230911 A CN 116230911A CN 202310241127 A CN202310241127 A CN 202310241127A CN 116230911 A CN116230911 A CN 116230911A
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composite material
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silicon
electrode composite
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CN116230911B (en
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薛永
郝宇
张文杰
赵珍
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Inner Mongolia Xinyuan Graphene Technology 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
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/626—Metals
    • 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 discloses a high-power silicon-carbon negative electrode composite material and a preparation method thereof, and relates to the technical field of preparation of lithium ion battery materials. The high-power silicon-carbon negative electrode composite material is of a core-shell structure, the inner core is of a nano silicon-porous metal-carbon fiber composite material, and the outer shell is composed of organic lithium salt and amorphous carbon; the content of the shell in the high-power silicon-carbon negative electrode composite material is 5-15wt%. According to the invention, the nano silicon is deposited in the porous metal carbon fiber by adopting a gas atomization method, and the organic lithium salt is deposited on the surface of the core by adopting the gas atomization method, so that the power performance and the cycle performance of the silicon-carbon composite material are improved.

Description

High-power silicon-carbon negative electrode composite material and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion battery material preparation, in particular to a high-power silicon-carbon negative electrode composite material and a preparation method thereof.
Background
The silicon-carbon material is applied to the lithium ion battery with high specific energy density due to the advantages of high specific capacity, wide material source and the like, but is only applied to the fields of electric tools, digital codes and the like due to the high full-charge expansion and poor cycle performance, and cannot be applied to the fields of EV and the like. The reason why the silicon-carbon material expands greatly is that the silicon crystal grains of the silicon-carbon material prepared by the sand milling method are large (about 20 nm) so that the cycle performance is poor, and the improvement of the cycle performance and the reduction of the expansion need to start from the reduction of the size of the silicon crystal grains. The nano silicon for preparing the silicon-carbon material by the silane cracking method has the advantages of small silicon crystal grain (2-3 nm), low expansion, good cycle performance and the like, but the power performance of the porous carbon structure is deviated, and the multiplying power performance of the porous carbon structure is reduced.
Disclosure of Invention
The invention aims to provide a high-power silicon-carbon negative electrode composite material and a preparation method thereof, wherein nano silicon is deposited in a porous metal carbon compound of the high-power silicon-carbon negative electrode composite material by adopting a gas atomization method, and organic lithium salt is deposited on the surface of the high-power silicon-carbon negative electrode composite material by adopting the gas atomization method, so that the power performance and the cycle performance of the silicon-carbon composite material are improved.
In order to achieve the above object, the present invention provides the following solutions:
according to one of the technical schemes, the high-power silicon-carbon negative electrode composite material is of a core-shell structure, the inner core is of a nano silicon-porous metal carbon fiber composite material, and the shell consists of organic lithium salt and amorphous carbon; the content of the shell in the high-power silicon-carbon negative electrode composite material is 5-15wt%;
the mass ratio of the porous metal carbon fiber to the nano silicon in the inner core is 20-80:20-80; the content of metal in the porous metal carbon fiber is 20-30%; the mass ratio of the organic lithium salt to the amorphous carbon in the shell is 10-30:70-90.
Further, the preparation method of the porous metal carbon fiber comprises the following steps:
dissolving acrylonitrile and an organic metal compound in an organic solvent, uniformly mixing to obtain a spinning solution, and carrying out electrostatic spinning to obtain nano organic metal carbon fibers;
sintering the nano organic metal carbon fiber for 1-6 hours at 750-850 ℃ in inert atmosphere to obtain the porous metal carbon fiber.
Further, the conditions of the electrospinning are as follows: the voltage is 15-25kV, the injection speed is 0.1-1mm/min, and the receiving distance is 15-25cm; the organic metal compound is one of zirconium acetylacetonate, tetrabutyl zirconate, zirconium vanadate and zirconium isooctanoate; the organic solvent is N, N-dimethylformamide; the mass ratio of the acrylonitrile to the organic metal compound is 100:1-10; the concentration of acrylonitrile in the spinning solution is 10-30wt%.
In the invention, the organic metal compound is selected from zirconium compounds, and zirconium metal is expected to have the characteristic of good structural stability for other metals (such as titanium and the like), thereby being more beneficial to rapid transmission of lithium ions.
The second technical scheme of the invention is that the preparation method of the high-power silicon-carbon negative electrode composite material comprises the following steps:
step 1, depositing nano silicon in porous metal carbon fiber by a gas atomization method to obtain the inner core;
and 2, depositing organic lithium salt on the surface of the inner core by a gas spraying method to obtain the high-power silicon-carbon negative electrode composite material.
Further, in the step 1, the porous metal carbon fiber is transferred into a reaction cavity, vacuum is firstly pumped, then silane gas and carbon source gas are simultaneously introduced, the pressure in the cavity is kept at 0.1-1Mpa, and the porous metal carbon fiber is cracked for 30-300min at the temperature of 200-500 ℃ to obtain the inner core.
Further, the silane gas is SiH 4 The carbon source gas is one of methane, ethane, acetylene and ethylene.
Further, the flow rate of the silane gas is 10-100mL/min; the flow rate of the carbon source gas is 1-10mL/min.
If the flow rate of the silane gas is too high, nano silicon is easy to deposit on the surface of the porous carbon and cannot enter the pores of the porous carbon, so that the expansion is larger, if the flow rate of the silane gas is too low, the deposition efficiency is reduced, so that the deposition time is too long, the nano silicon also grows up, and the expansion is larger.
If the flow rate of the carbon source gas is too high, the amorphous carbon of the outer layer is not compact, and the circulation performance is affected; if the flow rate of the carbon source gas is too low, the deposition time is long, the nano silicon deposited by the inner core grows larger, and the expansion is larger.
In the step 2, transferring the inner core into a vacuum reaction cavity to serve as a matrix, taking an organic lithium solution as a spray liquid, and adopting a gas spraying method to obtain the high-power silicon-carbon negative electrode composite material; the gas spraying method specifically comprises the following steps: the vacuum degree of the vacuum cavity is 0.1-1atm, the temperature of the atomizing chamber is 100-200 ℃, the carrier gas is argon, the atomizing speed is 0.1-1kg/min, and the time is 1-6h.
Further, the concentration of the organic lithium salt in the organic lithium salt solution is 1-10wt%; the organic lithium salt is one of lithium acetate, lithium oxalate, lithium bis (trifluoromethane) sulfonate and lithium trifluoromethane sulfonate.
According to the third technical scheme of the invention, the lithium ion battery is prepared from the high-power silicon-carbon negative electrode composite material.
The invention discloses the following technical effects:
according to the invention, nano silicon is deposited in the porous metal carbon fiber, and expansion is reduced by virtue of the porous structure and the metal fibrous carbon structure; meanwhile, the metal fiber structure has the characteristic of high electronic conductivity, and the rate capability is improved.
According to the invention, the organic lithium is deposited on the surface of the nano silicon-metal carbon fiber by adopting a gas atomization method, the irreversible capacity of the nano silicon-metal carbon fiber in the first charge and discharge process is reduced by means of the organic lithium on the surface of the nano silicon-metal carbon fiber, the first efficiency and the lithium ion transmission rate are improved, and meanwhile, the gas atomization method has the advantages of low reaction temperature, small silicon grain growth, high efficiency and the like compared with a vapor deposition method; and the organic lithium is deposited on the surface of the inner core (composed of porous metal carbon fiber and nano silicon) and has the advantages of high compatibility with electrolyte, and the like, so that the storage performance is improved. Meanwhile, as the nano silicon is contacted with the electrolyte, more side reactions and gas production can be caused, amorphous carbon is coated on the nano silicon, and the nano silicon is isolated from being directly contacted with the electrolyte, so that the side reactions are reduced; meanwhile, the amorphous carbon of the shell has better compatibility with electrolyte, and the storage performance and the power performance are improved.
The invention adopts silane for cracking, has the advantages of low cracking temperature, weak activity, small silicon grains, uniform deposition and the like, and the surface of the silicon is coated with the lithium compound and the amorphous carbon to promote the electronic and ionic conductivity of the material, and has the advantages of excellent power performance, low expansion, good cycle performance and the like when being applied to a lithium ion battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is an SEM image of the silicon carbon composite material prepared in example 1.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
As used herein, the term "room temperature" means 20 to 30℃unless otherwise specified.
Example 1
Step S1, 100g of polyacrylonitrile is dissolved in 500g of N, N-dimethylformamide solvent to obtain a spinning solution with 20wt%, then 5g of zirconium acetylacetonate is added to be uniformly mixed, and then the nano organic metal carbon fiber is obtained through electrostatic spinning (the voltage is 20kV, the injection speed is 0.5mm/min and the receiving distance is 20 cm); then sintering for 3 hours at 800 ℃ in argon atmosphere to obtain porous metal carbon fibers;
s2, transferring the porous metal carbon fiber into a reaction cavity, vacuumizing to 0.1Torr, and simultaneously introducing SiH 4 Gas and methane gas (SiH) 4 The gas flow rate is 50mL/min, the methane gas flow rate is 5 mL/min), the pressure in the cavity is kept at 0.5Mpa, cracking is carried out for 60min at the temperature of 300 ℃, and then the temperature is reduced to room temperature under the argon atmosphere, so as to obtain the nano silicon-porous metal carbon fiber composite material (wherein the size of nano silicon is 3 nm);
and S3, transferring the nano silicon-porous metal carbon fiber composite material into a vacuum reaction cavity A to serve as a matrix, dissolving 5g of lithium acetate into 100g of chloroform to prepare 5wt% of organic lithium solution serving as spray liquid, adopting a gas spraying method, wherein the vacuum degree of the vacuum cavity is 0.5atm, the temperature of an atomization chamber is 150 ℃, carrier gas is argon, the atomization rate is 0.5kg/min, and the time is 3 hours, so as to obtain the lithium doped amorphous carbon coated nano silicon-porous metal carbon fiber composite material (high-power silicon carbon negative electrode composite material, silicon carbon composite material for short).
Example 2
Step S1, 100g of polyacrylonitrile is dissolved in 1000g of N, N-dimethylformamide solvent to obtain 10wt% spinning solution, then 1g of tetrabutyl zirconate is added and mixed uniformly, and then the nano organic metal carbon fiber is obtained through electrostatic spinning (the voltage is 15kV, the injection speed is 0.1mm/min and the receiving distance is 15 cm); then sintering for 6 hours at 750 ℃ in argon atmosphere to obtain porous metal carbon fiber;
s2, transferring the porous metal carbon fiber into a reaction cavity, vacuumizing to 0.1Torr, and simultaneously introducing SiH 4 Gas and acetylene gas (SiH) 4 The gas flow is 10mL/min, the acetylene gas flow is 1 mL/min), the pressure in the cavity is kept at 0.1Mpa, the cracking is carried out for 300min at the temperature of 200 ℃, and then the temperature is reduced to the room temperature under the argon atmosphere, so as to obtain the nano silicon-porous metal carbon fiber composite material;
and S3, transferring the nano silicon-porous metal carbon fiber composite material into a vacuum reaction cavity A to serve as a matrix, dissolving 1g of lithium oxalate into 100g of chloroform organic solvent to prepare 1wt% of organic lithium solution serving as spray liquid, adopting a gas spraying method, wherein the vacuum degree of the vacuum cavity is 0.1atm, the temperature of an atomization chamber is 100 ℃, carrier gas is argon, the atomization rate is 0.1kg/min, and the time is 6h, so that the lithium doped amorphous carbon coated nano silicon-porous metal carbon fiber composite material (high-power silicon carbon negative electrode composite material, for short, silicon carbon composite material) is obtained.
Example 3
Step S1, 100g of polyacrylonitrile is dissolved in 33g of N, N-dimethylformamide solvent to obtain 30wt% spinning solution, 10g of zirconium vanadate is added to be uniformly mixed, and then the nano organic metal carbon fiber is obtained through electrostatic spinning (voltage is 25kV, push injection speed is 1mm/min and receiving distance is 25 cm); sintering for 1h at 850 ℃ in argon atmosphere to obtain porous metal carbon fibers;
s2, transferring the porous metal carbon fiber into a reaction cavity, vacuumizing to 0.1Torr, and simultaneously introducing SiH 4 Gas and ethylene gas (SiH) 4 Gas flow rate 100mL/min, ethylene gas flow rate 10 mL/min), and maintainedThe pressure in the cavity is 1Mpa, cracking is carried out for 30min at the temperature of 500 ℃, and then the temperature is reduced to room temperature under the argon atmosphere, so as to obtain the nano silicon-porous metal carbon fiber composite material;
and S3, transferring the nano silicon-porous metal carbon fiber composite material into a vacuum reaction cavity A to serve as a matrix, dissolving 10g of lithium acetate into 100g of chloroform organic solvent to prepare 10wt% of organic lithium solution serving as spray liquid, adopting a gas spraying method, wherein the vacuum degree of the vacuum cavity is 1atm, the temperature of an atomization chamber is 200 ℃, carrier gas is argon, the atomization rate is 1kg/min, and the time is 1h, so that the lithium doped amorphous carbon coated nano silicon-porous metal carbon fiber composite material (high-power silicon carbon negative electrode composite material, silicon carbon composite material for short) is obtained.
Comparative example 1
Porous carbon fibers (manufacturer: hangzhou Heshi New Material science and technology Co., ltd., parameters; pore size of 3-5 μm, pore size of 10-50nm, specific surface area of 200-800 m) 2 Per g) is transferred into a reaction chamber, firstly, the vacuum is pumped to 0.1Torr, and then SiH is simultaneously introduced 4 Gas (flow rate 50 mL/min), keeping the pressure in the cavity at 0.5Mpa, cracking at 300 ℃ for 60min, and then cooling to room temperature under argon atmosphere to obtain the nano silicon-porous carbon fiber composite material;
transferring the nano silicon-porous carbon fiber composite material into a vacuum reaction cavity A to serve as a matrix, dissolving 5g of lithium acetate into 100g of chloroform to prepare 5wt% of organic lithium solution serving as spray liquid, adopting a gas spraying method, wherein the vacuum degree of the vacuum cavity is 0.5atm, the temperature of an atomization chamber is 150 ℃, carrier gas is argon, the atomization rate is 0.5kg/min, and the time is 3h, so that the lithium doped amorphous carbon coated nano silicon-porous carbon fiber composite material (called as silicon carbon composite material for short) is obtained.
Comparative example 2
Transferring the nano silicon-porous metal carbon fiber composite material in the step S2 in the embodiment 1 into a tube furnace, introducing argon atmosphere to remove air in the tube, and heating to 500 ℃ for carbonization for 3 hours to obtain the metal doped nano silicon porous carbon composite material (called as silicon carbon composite material for short).
Effect verification example
1. Morphology of
The silicon carbon composite material prepared in example 1 was subjected to a Scanning Electron Microscope (SEM) test, and the test results are shown in fig. 1. As can be seen from FIG. 1, the silicon carbon composite material has a fibrous structure, and has a diameter of about 1 μm and a length of 20-100 μm.
2. Button cell testing
The silicon-carbon composite materials in examples 1-3 and comparative examples 1-2 were assembled into button cells as lithium ion battery negative electrode materials, and the preparation process comprises: adding a binder, a conductive agent and a solvent into a lithium ion battery anode material, stirring and pulping, coating the mixture on a copper foil, and drying and rolling the mixture to prepare an anode plate; the binder is polyvinylidene fluoride (PVDF), the conductive agent is conductive carbon black (SP), the solvent is N-methyl pyrrolidone (NMP), and the dosage ratio of the negative electrode material to SP, PVDF, NMP is 95g:1g:4g:220mL; liPF in electrolyte 6 As an electrolyte, a mixture of Ethylene Carbonate (EC) and methyl ethyl carbonate (DEC) in a volume ratio of 1:1 is used as a solvent; the metal lithium sheet is a counter electrode, and the diaphragm adopts a polypropylene (PP) film. The button cell assembly was performed in an argon filled glove box. Electrochemical performance tests were performed on button cells comprising the silicon carbon composites of examples 1-3 and comparative examples 1-2, the tests were performed on a wuhan blue CT2001A type cell tester with a charge-discharge voltage ranging from 0.005V to 2.0V and a charge-discharge rate of 0.1C. Meanwhile, the powder conductivity of the material is tested by a four-probe tester, and the granularity, the specific surface area and the tap density are tested according to the national standard GBT-38823-2020 silicon carbon, and the test result is shown in Table 1.
TABLE 1
Figure BDA0004129428250000091
Figure BDA0004129428250000101
As can be seen from the data in table 1, the specific capacity and the first efficiency of the silicon-carbon composite material prepared in the embodiments 1-3 of the present invention are obviously better than those of the comparative examples 1-2, because the surface of the silicon-carbon composite material is coated with organic lithium to reduce irreversible capacity loss and improve the first efficiency, and meanwhile, the porous carbon fiber has the characteristics of low expansion and high specific surface area compared with the carbon fiber material, and the expansion is reduced; meanwhile, the metal doped in the porous metal carbon fiber has the advantages of low electronic impedance and small expansion, and improves the electrical conductivity of the powder and reduces the expansion.
3. Soft package battery test
The silicon-carbon composite materials in the examples 1-3 and the comparative examples 1-2 are respectively doped with 90% of artificial graphite to be used as a negative electrode material to prepare a negative electrode plate, and NCM532 is used as a positive electrode material; liPF6 in the electrolyte is electrolyte, and a mixture of EC and DEC with a volume ratio of 1:1 is used as a solvent; a5 Ah soft package battery was prepared using Celgard 2400 membrane as a separator. And respectively testing the liquid absorption and retention capacity of the negative plate, the full-electricity reverse elasticity of the plate and the cycle performance.
a. Liquid absorption capacity test
And (3) adopting a 1mL burette, sucking 1mL of electrolyte, dripping the electrolyte on the surface of the pole piece once, timing the electrolyte until the electrolyte is absorbed, and recording the time t. The test results are shown in Table 2.
b. Pole piece full-power rebound rate test
Firstly, testing the average thickness of a pole piece by adopting a thickness gauge to be D1, then fully charging the soft-packed battery to 4.2V, then dissecting the battery, taking out a negative pole piece to test the thickness of the negative pole piece to be D2, and calculating according to the following formula: pole piece full charge rebound rate= (D2-D1) ×100%/D1. The test results are shown in Table 2.
C. Cycle performance test
The cycle performance of the battery was tested at 25.+ -. 3 ℃ with a charge/discharge rate of 1C/1C and a voltage range of 2.5V-4.2V. The test results are shown in Table 2.
TABLE 2
Examples Liquid suction speed (t) Full-power rebound rate of pole piece Cycle 500 times capacity retention (%)
Example 1 45 29％ 93.5％
Example 2 54 31％ 92.3％
Example 3 41 28％ 93.9％
Comparative example 1 78 37％ 89.6％
Comparative example 2 95 41％ 87.5％
As can be seen from Table 2, the liquid absorption and retention capacities of the silicon-carbon composites obtained in examples 1-3 are significantly higher than those of comparative examples 1-2. The experimental result shows that the silicon-carbon composite material has higher liquid absorption and retention capacity. The reasons for this may be: the silicon-carbon composite material prepared in the embodiment 1-3 has high specific surface area, so that the liquid absorption and retention capacity of the material is improved. Meanwhile, the full-charge rebound rate of the negative electrode plate made of the silicon-carbon composite material obtained in the embodiment 1-3 is lower than that of the negative electrode plate made of the silicon-carbon composite material in the comparison 1-2, namely the negative electrode plate made of the silicon-carbon composite material has lower full-charge rebound rate of the electrode plate. Meanwhile, by means of the porous structure of the porous carbon fiber and the fibrous carbon structure thereof, the expansion is reduced, the cycle performance is improved, and the transmission rate of lithium ions in the charge and discharge process is improved by means of doped organic lithium, so that the cycle performance is improved.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.

Claims (10)

1. The high-power silicon-carbon negative electrode composite material is characterized in that the high-power silicon-carbon negative electrode composite material is of a core-shell structure, the inner core is of a nano silicon-porous metal carbon fiber composite material, and the shell consists of organic lithium salt and amorphous carbon; the content of the shell in the high-power silicon-carbon negative electrode composite material is 5-15wt%;
the mass ratio of the porous metal carbon fiber to the nano silicon in the inner core is 20-80:20-80; the content of metal in the porous metal carbon fiber is 20-30%; the mass ratio of the organic lithium salt to the amorphous carbon in the shell is 10-30:70-90.
2. The high-power silicon-carbon negative electrode composite material according to claim 1, wherein the preparation method of the porous metal carbon fiber comprises the following steps:
dissolving acrylonitrile and an organic metal compound in an organic solvent, uniformly mixing to obtain a spinning solution, and carrying out electrostatic spinning to obtain nano organic metal carbon fibers;
sintering the nano organic metal carbon fiber for 1-6 hours at 750-850 ℃ in inert atmosphere to obtain the porous metal carbon fiber.
3. The high power silicon carbon negative electrode composite material according to claim 2, wherein the conditions of the electrospinning are: the voltage is 15-25kV, the injection speed is 0.1-1mm/min, and the receiving distance is 15-25cm; the organic metal compound is one of zirconium acetylacetonate, tetrabutyl zirconate, zirconium vanadate and zirconium isooctanoate; the organic solvent is N, N-dimethylformamide; the mass ratio of the acrylonitrile to the organic metal compound is 100:1-10; the concentration of acrylonitrile in the spinning solution is 10-30wt%.
4. A method for preparing the high-power silicon-carbon negative electrode composite material as claimed in claim 1, which is characterized by comprising the following steps:
step 1, depositing nano silicon in porous metal carbon fiber by a gas atomization method to obtain the inner core;
and 2, depositing organic lithium salt on the surface of the inner core by a gas spraying method to obtain the high-power silicon-carbon negative electrode composite material.
5. The preparation method according to claim 4, wherein in step 1, the porous metal carbon fiber is transferred into a reaction chamber, vacuum is firstly pumped, then silane gas and carbon source gas are simultaneously introduced, the pressure in the chamber is kept at 0.1-1Mpa, and the inner core is obtained by cracking for 30-300min at the temperature of 200-500 ℃.
6. The method according to claim 5, wherein the silane gas is SiH 4 The carbon source gas is one of methane, ethane, acetylene and ethylene.
7. The method according to claim 5, wherein the flow rate of the silane gas is 10 to 100mL/min; the flow rate of the carbon source gas is 1-10mL/min.
8. The preparation method of the high-power silicon-carbon negative electrode composite material is characterized in that in the step 2, the inner core is transferred into a vacuum reaction cavity to serve as a matrix, an organic lithium solution serves as a spray liquid, and a gas spraying method is adopted to obtain the high-power silicon-carbon negative electrode composite material; the gas spraying method specifically comprises the following steps: the vacuum degree of the vacuum cavity is 0.1-1atm, the temperature of the atomizing chamber is 100-200 ℃, the carrier gas is argon, the atomizing speed is 0.1-1kg/min, and the time is 1-6h.
9. The method of claim 8, wherein the concentration of the organolithium salt in the organolithium salt solution is 1-10wt%; the organic lithium salt is one of lithium acetate, lithium oxalate, lithium bis (trifluoromethane) sulfonate and lithium trifluoromethane sulfonate.
10. A lithium ion battery, wherein the negative electrode material is the high-power silicon-carbon negative electrode composite material in claim 1.
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Citations (3)

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Publication number Priority date Publication date Assignee Title
US20090269511A1 (en) * 2008-04-25 2009-10-29 Aruna Zhamu Process for producing hybrid nano-filament electrodes for lithium batteries
CN110518226A (en) * 2019-09-10 2019-11-29 石家庄尚太科技有限公司 A kind of silicon-carbon composite cathode material and preparation method thereof
CN115692677A (en) * 2022-11-28 2023-02-03 胜华新材料科技(眉山)有限公司 High-power low-expansion silica metal oxide composite material and preparation method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090269511A1 (en) * 2008-04-25 2009-10-29 Aruna Zhamu Process for producing hybrid nano-filament electrodes for lithium batteries
CN110518226A (en) * 2019-09-10 2019-11-29 石家庄尚太科技有限公司 A kind of silicon-carbon composite cathode material and preparation method thereof
CN115692677A (en) * 2022-11-28 2023-02-03 胜华新材料科技(眉山)有限公司 High-power low-expansion silica metal oxide composite material and preparation method thereof

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