CN113611858A - Battery negative electrode active material and preparation method thereof - Google Patents
Battery negative electrode active material and preparation method thereof Download PDFInfo
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- CN113611858A CN113611858A CN202110703575.XA CN202110703575A CN113611858A CN 113611858 A CN113611858 A CN 113611858A CN 202110703575 A CN202110703575 A CN 202110703575A CN 113611858 A CN113611858 A CN 113611858A
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 229910021426 porous silicon Inorganic materials 0.000 claims abstract description 93
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- 239000003575 carbonaceous material Substances 0.000 claims abstract description 26
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- 238000000034 method Methods 0.000 claims description 22
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- 229910000676 Si alloy Inorganic materials 0.000 claims description 14
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- 239000010703 silicon Substances 0.000 claims description 13
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- 239000006183 anode active material Substances 0.000 claims description 9
- 239000002994 raw material Substances 0.000 claims description 9
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- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical group [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 7
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- 230000035484 reaction time Effects 0.000 claims description 2
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- 229920000642 polymer Polymers 0.000 abstract description 3
- 238000010000 carbonizing Methods 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 17
- 230000008569 process Effects 0.000 description 13
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- 229910021641 deionized water Inorganic materials 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
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- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 4
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
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- CTENFNNZBMHDDG-UHFFFAOYSA-N Dopamine hydrochloride Chemical compound Cl.NCCC1=CC=C(O)C(O)=C1 CTENFNNZBMHDDG-UHFFFAOYSA-N 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
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- 238000005054 agglomeration Methods 0.000 description 1
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- 150000001450 anions Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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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
- H01M4/628—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 battery negative active material and a preparation method thereof, wherein the negative active material comprises porous silicon microspheres and a carbon material, and the porous silicon microspheres and the carbon material form a core-shell structure: the porous silicon microspheres are cores, and the carbon material is coated on the surfaces of the porous silicon microspheres to form shell layers. The preparation method comprises the following steps: (1) preparing porous silicon microspheres; (2) preparing polymer-coated porous silicon microspheres; (3) and heating and carbonizing the porous silicon microspheres coated with the polymer to obtain the battery negative active material. The cathode active material has excellent comprehensive electrochemical performance, and the preparation method is simple and low in production cost.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a battery cathode active material and a preparation method thereof.
Background
At present, the negative active material with more practical application in the field of lithium ion batteries is a carbon material, in the non-carbon negative active material, silicon has extremely high theoretical specific capacity and a moderate lithium storage reaction voltage platform, and the silicon is widely distributed in the nature, and the content of the silicon in the crust is only inferior to that of oxygen, so the silicon-based negative active material is a novel high-energy material with great development prospect. However, the electronic conductivity and ionic conductivity of silicon are low, resulting in poor kinetics of electrochemical reactions; the cycle stability of ordinary pure silicon is poor. And the phase change and the volume expansion of the silicon in the lithiation process can generate larger stress, so that the electrode is broken and pulverized, the resistance is increased, and the cycle performance is suddenly reduced; in this regard, the prior art generally adopts the silicon-carbon composite material to solve the above problems, but the prior silicon-carbon composite material still has the following technical problems:
1. the silicon material has overlarge grain diameter and is difficult to maintain a porous skeleton structure, the original grain diameter of the silicon material in the prior art is 50 microns, the grain diameter of the powder obtained after crushing is 15 microns, and due to the problem of raw material selection, the silicon material subjected to dealuminization metal treatment is difficult to maintain a porous skeleton, is easy to pulverize and is difficult to thoroughly solve the defects of the silicon-based material.
2. In the aspect of the process, firstly, the pretreatment process of raw materials is complex, manpower and material resources are consumed, the production cost and time are not favorably saved, the particle size of the powder obtained by pretreatment is large, the volume change is large in the lithium intercalation and deintercalation process, and the defect that the silicon-based material is easy to pulverize is not fundamentally overcome structurally, so that the cycle performance of the battery is reduced; secondly, in the prior art, glucose is often used as a carbon source, a spray drying process is adopted, the surface of each silicon particle is difficult to be coated with glucose molecules and realize uniform coating of the glucose, after carbonization, uniform and complete coating of a carbon film is difficult to realize, and the required carbonization temperature is too high and reaches 950 ℃.
The obtained silicon-carbon cathode active material has limited improvement on the comprehensive electrochemical performance of the lithium ion battery due to the problems, and the market demand on the high-performance lithium ion battery cannot be met.
Disclosure of Invention
The invention provides a battery cathode active material and a preparation method thereof, which are used for solving the technical problem that the improvement of the comprehensive electrochemical performance of a lithium ion battery by the existing silicon-carbon composite cathode active material is limited.
In order to solve the technical problems, the invention adopts the following technical scheme:
a battery negative active material comprises porous silicon microspheres and a carbon material, wherein the porous silicon microspheres and the carbon material form a core-shell structure; wherein the porous silicon microspheres are cores, and the carbon material is coated on the surfaces of the porous silicon microspheres to form a shell layer; the particle size of the porous silicon microspheres is 1-2 μm.
The design idea of the technical scheme is that aluminum metal atoms are removed to ensure that residual silicon forms porous silicon, then the carbon layer is coated in situ to construct the carbon-coated porous silicon material with the core-shell structure, the porous structure provides a buffer space for volume expansion of the silicon material in the charging and discharging process, meanwhile, the coated carbon layer can prevent the porous silicon skeleton pore structure from being damaged and pulverized due to transition expansion, and the cathode active material with the structure has excellent electrochemical performance. The particle size of the porous silicon microspheres is limited to 1-2 microns, so that the problems of poor structural strength and easy pulverization of the porous silicon caused by overlarge particle size can be solved, the situation that the comprehensive performance of the negative electrode active material is reduced due to the fact that the aggregation phenomenon is easy to occur in the preparation and use processes due to the fact that the particle size of the porous silicon microspheres is too small can be avoided, and meanwhile the loading capacity of the active material on the unit area of the electrode can be increased.
As a further preferable mode of the above aspect, the mass fraction of the carbon material in the battery negative electrode active material is 2% to 20%.
As a further preferable mode of the above aspect, the carbon material is doped with a nitrogen element. The nitrogen-doped carbon material layer has better conductivity than a pure carbon layer, is favorable for electron transmission on the surface of an electrode and is favorable for comprehensive electrochemical performance of a lithium ion battery.
Based on the same technical concept, the invention also provides a preparation method of the battery negative active material, which comprises the following steps:
(1) preparing porous silicon microspheres;
(2) adding the porous silicon microspheres into a solvent, adding a surfactant, and mixing to form a mixed solution; adding a carbon source and a reaction auxiliary agent into the mixed solution, carrying out solid-liquid separation after mixing and reacting for a certain time, collecting a solid product, and carrying out vacuum drying on the solid product to obtain an intermediate product;
(3) and heating the intermediate product to 600-800 ℃ in a protective atmosphere, preserving heat for 2-3 h, and cooling to obtain the battery cathode active material.
As a further preferable mode of the above technical solution, in the step (1), the porous silicon microspheres are prepared by using aluminum-silicon alloy powder with a particle size of 1 to 2 μm as a raw material, and the specific preparation method includes: and adding the aluminum-silicon alloy powder into an acid solution, reacting for a certain time, carrying out solid-liquid separation, and collecting filter residues to obtain the porous silicon microspheres. The aluminum-silicon alloy (AlSi) powder with the particle size of 1-2um is used as a raw material, the raw material does not need pretreatment, a complex pretreatment process is omitted, the production time and the cost can be effectively saved, and the prepared porous silicon has smaller powder particle size, so that the improvement of the overall performance of the cathode active material is facilitated.
In a further preferred embodiment of the present invention, the aluminum-silicon alloy powder contains silicon in an amount of 15 to 40% by mass. The aluminum-silicon alloy powder with the silicon content is easy to form a stable porous framework after being treated by acid, so that porous silicon microspheres with strong structural strength can be obtained, and the problems of poor structural strength and easiness in pulverization of the porous silicon can be avoided to a certain extent.
In a further preferred embodiment of the foregoing technical solution, the acid solution is a 2M HCl aqueous solution, and the reaction time of the aluminum-silicon alloy and the acid solution is 12 to 24 hours.
As a further preferable mode of the above technical solution, in the step (2), the carbon source is one of pyrrole, aniline and dopamine. Pyrrole, aniline and dopamine serve as a carbon source and a nitrogen source, when the three monomers serve as raw materials, uniform coating can be achieved through in-situ chemical oxidative polymerization, the formed polymer can be guaranteed to uniformly coat porous silicon, and a carbon material layer formed through final carbonization is complete and uniform; meanwhile, as the macromolecular chains of the polypyrrole, the polyaniline and the polydopamine are pyrolyzed and further carbonized at the temperature of 600-800 ℃, the subsequent carbonization temperature can be reduced by taking the polypyrrole, the polyaniline and the dopamine as raw materials, and the formation of silicon carbide is effectively avoided.
As a further preferred aspect of the above technical solution, when the carbon source is pyrrole or aniline, the surfactant is sodium dodecyl sulfate, and the reaction auxiliary agent is hydrochloric acid; when the carbon source is dopamine, the buffering agent is tris (hydroxymethyl) aminomethane, and the reaction auxiliary agent is hydrochloric acid. The sodium dodecyl sulfate can play a role in helping the porous silicon to disperse in the solution, the hydrochloric acid is a doping agent, and the chloride ions in the solution can be used as doping anions; hydroxymethyl aminomethane is a buffer to maintain the pH of the solution at 8.5.
As a further preferable mode of the above technical solution, the temperature increase rate of the intermediate product heating process in the step (3) is 5 ℃/min. Too fast a temperature rise rate leads to a large temperature difference between the furnace temperature and the sample temperature, so that the sample temperature does not reach the carbonization temperature when the tube furnace starts holding, resulting in a reduction in the actual carbonization time of the sample, and therefore, the temperature rise rate should not be too fast.
Compared with the prior art, the invention has the advantages that:
(1) according to the cathode active material, the core-shell structure provides a buffer space for volume expansion in the charge and discharge processes of the silicon material, and the coated nitrogen-doped carbon layer can prevent the porous silicon skeleton pore structure from being damaged and pulverized due to transitional expansion, so that the electrochemical performance of the cathode active material is remarkably improved; meanwhile, the particle size of porous silicon in the cathode active material is 1-2um, and the smaller powder particle size reduces the absolute volume change of silicon particles in the lithium desorption and intercalation process, reduces the pulverization degree of silicon and further improves the cycling stability of the battery; compared with nano silicon, the micron silicon can reduce the agglomeration phenomenon of particles and increase the loading capacity of active substances on the unit area of the electrode. When the negative active material is applied to a battery, the first coulombic efficiency of the battery is up to 87.52% under the current density of 0.1A/g, the first discharge specific capacity reaches 2609.2mAh/g, the discharge specific capacity can still reach 1574.8mAh/g after charge-discharge circulation for 2000 times, the reversible specific capacity under the current density of 5A/g reaches 884.1mAh/g, and the negative active material shows excellent comprehensive electrochemical performance.
(2) The preparation method of the cathode active material is simple in process and suitable for industrial large-scale production, and the selected raw materials do not need pretreatment, so that the production cost and time are saved. Meanwhile, the prepared porous silicon has a porous framework with higher strength, the carbon material coating layer finally formed by the process is complete in appearance and uniform in coating, the temperature range in the carbonization process is 600-800 ℃, the formation of silicon carbide can be avoided, and the production cost is reduced.
Drawings
Fig. 1 is a scanning electron micrograph of a negative active material of example 1;
fig. 2 is a transmission electron micrograph of a negative active material of example 1;
fig. 3 is a graph of cycle performance and coulombic efficiency at a current density of 0.1A/g for the negative active material of example 1 and the comparative example product.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1
The negative active material of the embodiment includes porous silicon microspheres and a carbon material layer coated on the porous silicon microspheres, and the porous silicon microspheres and the carbon material layer together form a core-shell structure, wherein the particle size of the porous silicon microspheres is 1 μm, and the carbon material layer is doped with nitrogen.
The method for preparing the anode active material of the present embodiment includes the steps of:
(1) preparation of porous silicon (P-Si) microspheres: preparing 300mL of 2M HCl aqueous solution, weighing 5g of aluminum silicon alloy (AlSi) powder with the particle size of 1-2um, slowly adding the powder into the prepared HCl aqueous solution, and magnetically stirring the solution at room temperature for 24 hours to remove Al; and (3) carrying out suction filtration and collection on the reaction product, washing the sample for several times by using deionized water and absolute ethyl alcohol, and placing the washed sample in an oven for vacuum drying at 60 ℃ to obtain the porous silicon.
(2) Preparation of polypyrrole-coated porous silicon (P-Si @ PPy) microspheres: dissolving 10mg Sodium Dodecyl Sulfate (SDS) into 100ml deionized water, weighing 0.16g porous silicon, adding the solution, performing ultrasonic treatment for 5min to disperse the porous silicon, and then stirring at room temperature overnight; then, 1mL of 1MHCl aqueous solution and 100uL of pyrrole are sequentially added into the mixed solution; dissolving 0.228g of ammonium persulfate in 10mL of deionized water, adding the mixed solution, and magnetically stirring for 3 hours at the temperature of 0-5 ℃; and centrifuging to collect reaction products, sequentially cleaning the sample for several times by using deionized water and absolute ethyl alcohol, and placing the cleaned sample in a drying oven for vacuum drying at 60 ℃ to obtain the polypyrrole-coated porous silicon.
(3) Preparing a nitrogen-doped carbon-coated porous silicon (P-Si @ NC) microsphere: and (3) putting the obtained polypyrrole coated porous silicon into a magnetic boat, putting the magnetic boat into a tubular furnace, keeping the temperature at 800 ℃ for 3h in Ar protective atmosphere, heating at the rate of 5 ℃/min, and cooling to room temperature along with the furnace after heating to obtain the nitrogen-doped carbon coated porous silicon.
Example 2
The negative active material of the embodiment includes porous silicon microspheres and a carbon material layer coated on the porous silicon microspheres, and the porous silicon microspheres and the carbon material layer together form a core-shell structure, wherein the particle size of the porous silicon microspheres is 1.5 μm, and the carbon material layer is doped with nitrogen.
A scanning electron micrograph of the negative active material of this example is shown in fig. 1 to see that the porous silicon surface was coated with a nitrogen-doped carbon layer.
A transmission electron micrograph of the negative active material of this example is shown in fig. 2, and it can be seen from the figure that the product is composed of porous silicon as an inner core and an outer nitrogen-doped carbon shell, and the observed lattice fringes with a interplanar spacing of 0.31nm correspond to the (111) crystal plane of silicon, and the thickness of the nitrogen-doped carbon shell is about 18 nm.
The method for preparing the anode active material of the present embodiment includes the steps of:
(1) preparation of porous silicon (P-Si) microspheres: preparing 300mL of 2M HCl aqueous solution, weighing 5g of aluminum silicon alloy (AlSi) powder with the particle size of 1-2um, slowly adding the powder into the prepared HCl aqueous solution, and magnetically stirring the solution at room temperature for 12 hours to remove Al; and (3) carrying out suction filtration and collection on the reaction product, washing the sample for several times by using deionized water and absolute ethyl alcohol, and placing the washed sample in an oven for vacuum drying at 60 ℃ to obtain the porous silicon.
(2) Preparing polyaniline-coated porous silicon (P-Si @ PANI) microspheres: dissolving 10mg Sodium Dodecyl Sulfate (SDS) into 100ml deionized water, weighing 0.16g porous silicon, adding the solution, performing ultrasonic treatment for 5min to disperse the porous silicon, and then stirring at room temperature overnight; then, 1mL of 1MHCl aqueous solution and 80uL of aniline are sequentially added into the mixed solution; dissolving 0.2g of ammonium persulfate in 5mL of deionized water, adding the mixed solution, and magnetically stirring at 0 ℃ for 6 hours; and centrifuging to collect reaction products, sequentially cleaning the sample for several times by using deionized water and absolute ethyl alcohol, and placing the cleaned sample in a drying oven for vacuum drying at 60 ℃ to obtain the polyaniline-coated porous silicon.
(3) Preparing a nitrogen-doped carbon-coated porous silicon (P-Si @ NC) microsphere: and putting the obtained polyaniline-coated porous silicon into a magnetic boat, putting the magnetic boat into a tube furnace, keeping the temperature of the magnetic boat in Ar protective atmosphere at 700 ℃ for 2h, heating at the rate of 5 ℃/min, and cooling the magnetic boat to room temperature along with the furnace after heating to obtain the nitrogen-doped carbon-coated porous silicon.
Example 3
The negative active material of the embodiment includes porous silicon microspheres and a carbon material layer coated on the porous silicon microspheres, and the porous silicon microspheres and the carbon material layer together form a core-shell structure, wherein the particle size of the porous silicon microspheres is 2 μm, and the carbon material layer is doped with nitrogen.
The method for preparing the anode active material of the present embodiment includes the steps of: (1) preparation of porous silicon (P-Si) microspheres: preparing 300mL of 2M HCl aqueous solution, weighing 5g of aluminum silicon alloy (AlSi) powder with the particle size of 1-2um, slowly adding the powder into the prepared HCl aqueous solution, and magnetically stirring the solution at room temperature for 18 hours to remove Al; and (3) carrying out suction filtration and collection on the reaction product, washing the sample for several times by using deionized water and absolute ethyl alcohol, and placing the washed sample in an oven for vacuum drying at 60 ℃ to obtain the porous silicon.
(2) Preparation of polydopamine-coated porous silicon (P-Si @ PDA) microspheres: preparing 100mL of 0.01M Tris solution (pH 8.5); then, 0.4g of porous silicon is added into the solution, and the solution is magnetically stirred for 30min to be uniformly dispersed; then 0.4g of dopamine hydrochloride is added, and the mixture is stirred for 24 hours at room temperature; and centrifuging to collect reaction products, sequentially cleaning the sample for several times by using deionized water and absolute ethyl alcohol, and placing the cleaned sample in a drying oven for vacuum drying at 60 ℃ to obtain the polydopamine-coated porous silicon.
(3) Preparing a nitrogen-doped carbon-coated porous silicon (P-Si @ NC) microsphere: and (3) putting the obtained polydopamine coated porous silicon into a magnetic boat, putting the magnetic boat into a tubular furnace, keeping the temperature at 800 ℃ for 2h in Ar protective atmosphere, heating at the rate of 5 ℃/min, and cooling to room temperature along with the furnace after heating to obtain the nitrogen-doped carbon coated porous silicon.
Comparative example
Preparation of porous silicon (P-Si) microspheres: preparing 300mL of 2M HCl aqueous solution, weighing 5g of aluminum silicon alloy (AlSi) powder with the particle size of 1-2um, slowly adding the powder into the prepared HCl aqueous solution, and magnetically stirring the solution at room temperature for 24 hours to remove Al; and (3) carrying out suction filtration and collection on the reaction product, washing the sample for several times by using deionized water and absolute ethyl alcohol, and placing the washed sample in an oven for vacuum drying at 60 ℃ to obtain the porous silicon.
When the negative active material of example 1 and the negative active material of comparative example were tested for cycle performance and coulombic efficiency at a current density of 0.1A/g, as shown in fig. 3, it can be seen from the graph that the comparative example (P-Si) has a higher initial specific discharge capacity than the product of example 1 (P-Si @ NC), but has an initial coulombic efficiency of only 74.95%, which is much lower than 87.52% of the product of example 1. The capacity of the comparative product decayed rapidly with increasing cycle number. After 2000 cycles, the specific discharge capacity of the comparative product is reduced to 702.5mAh/g, which is only 31.8 percent of the specific discharge capacity of the second time. The coulombic efficiency of the product in example 1 is always higher than 96% from the second charge and discharge, the specific discharge capacity of the product in the 2000 th cycle is 1574.8mAh/g, the capacity retention rate is 69% of that in the second cycle, and the product shows excellent electrochemical performance.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.
Claims (10)
1. The battery negative electrode active material is characterized by comprising porous silicon microspheres and a carbon material, wherein the porous silicon microspheres and the carbon material form a core-shell structure; wherein the porous silicon microspheres are cores, and the carbon material is coated on the surfaces of the porous silicon microspheres to form a shell layer; the particle size of the porous silicon microspheres is 1-2 μm.
2. The battery anode active material according to claim 1, wherein the mass fraction of the carbon material in the battery anode active material is 2% to 20%.
3. The battery anode active material according to claim 1, wherein the carbon material is doped with nitrogen.
4. A method for preparing the negative active material for a battery according to any one of claims 1 to 3, comprising the steps of:
(1) preparing porous silicon microspheres;
(2) adding the porous silicon microspheres into a solvent, adding a surfactant or a buffering agent, and mixing to form a mixed solution; adding a carbon source and a reaction auxiliary agent into the mixed solution, carrying out solid-liquid separation after mixing and reacting for a certain time, collecting a solid product, and carrying out vacuum drying on the solid product to obtain an intermediate product;
(3) and heating the intermediate product to 600-800 ℃ in a protective atmosphere, preserving heat for 2-3 h, and cooling to obtain the battery cathode active material.
5. The method for preparing the battery negative electrode active material according to claim 4, wherein in the step (1), the porous silicon microspheres are prepared by using aluminum-silicon alloy powder with the particle size of 1-2 μm as a raw material, and the preparation method comprises the following specific steps: and adding the aluminum-silicon alloy powder into an acid solution, reacting for a certain time, carrying out solid-liquid separation, and collecting filter residues to obtain the porous silicon microspheres.
6. The method for producing a battery negative electrode active material according to claim 5, wherein the mass fraction of silicon in the aluminum-silicon alloy powder is 15% to 40%.
7. The method for preparing the battery negative electrode active material according to claim 5, wherein the acid solution is a 2M HCl aqueous solution, and the reaction time of the aluminum-silicon alloy and the acid solution is 12-24 hours.
8. The method for preparing the battery anode active material according to claim 4, wherein in the step (2), the carbon source is one of pyrrole, aniline and dopamine.
9. The method for preparing the battery anode active material according to claim 8, wherein when the carbon source is pyrrole or aniline, the surfactant is sodium dodecyl sulfate, and the reaction auxiliary agent is hydrochloric acid; when the carbon source is dopamine, the buffering agent is tris (hydroxymethyl) aminomethane, and the reaction auxiliary agent is hydrochloric acid.
10. The method for preparing a battery anode active material according to claim 4, wherein the temperature increase rate of the intermediate product heating process in the step (3) is 5 ℃/min.
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| CN115483375A (en) * | 2022-09-05 | 2022-12-16 | 南京工业大学 | Method for applying silicon-carbon composite material to lithium ion battery cathode material |
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| CN112768672A (en) * | 2021-02-05 | 2021-05-07 | 昆明理工大学 | Method for preparing graphite-based Si @ C negative electrode material by taking micro silicon powder as Si source |
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| CN114420910A (en) * | 2022-01-19 | 2022-04-29 | 山东能源集团有限公司 | Nitrogen-doped silicon-carbon composite material with core-shell structure and preparation method thereof |
| CN114420910B (en) * | 2022-01-19 | 2023-12-01 | 山东能源集团有限公司 | Nitrogen-doped silicon-carbon composite material with core-shell structure and preparation method thereof |
| CN115483375A (en) * | 2022-09-05 | 2022-12-16 | 南京工业大学 | Method for applying silicon-carbon composite material to lithium ion battery cathode material |
| CN115483375B (en) * | 2022-09-05 | 2024-01-30 | 南京工业大学 | Method for applying silicon-carbon composite material to negative electrode material of lithium ion battery |
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