CN111048759A - Negative active material for lithium battery, and preparation method and application thereof - Google Patents
Negative active material for lithium battery, and preparation method and application thereof Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
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- 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
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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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- 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
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- 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 negative active material for a lithium battery, and a preparation method and application thereof. Wherein the method of preparing the anode active material comprises: mixing the first SiO dispersion liquid with the first graphene oxide dispersion liquid to obtain a first product; mixing the first product with a binder and a solvent, and granulating to obtain silica particles; mixing the silica particles with a solvent to obtain a second silica dispersion; mixing the second silica dispersion with the second graphene oxide dispersion and a reducing agent to obtain a second product; and calcining the second product to obtain the cathode active material. According to the method, the secondary coating is carried out on the silicon oxide material, so that the problem that the volume change of the silicon oxide material in the lithium removal/insertion process causes particle pulverization failure can be effectively relieved, the consumption of electrolyte and the corrosion of the material are reduced, in addition, the electronic conductivity of the negative electrode material can be effectively improved, and the cycle performance and the rate performance of the silicon negative electrode of the lithium ion battery are improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a negative active material for a lithium battery, and a preparation method and application thereof.
Background
The silicon protoxide material is used as an alloying type negative electrode material, the theoretical specific capacity of the silicon protoxide material is larger than 2000 mA.h/g, the lithium potential of the silicon protoxide material is lower (<0.5V), and the voltage platform is slightly higher than that of graphite. In the process of commercial application, the silicon oxide negative electrode material still has the following problems. Firstly, the silicon monoxide belongs to a semiconductor material, and has low conductivity, is not beneficial to electron transmission, and has poor rate performance in a battery. And secondly, the particle pulverization failure caused by the huge volume change of the silicon monoxide negative electrode material in the lithium removal/insertion process is caused, the volume expansion exceeds 300 percent, the negative electrode material is separated from a current collector, the capacity is rapidly reduced, and the cycle performance of the battery is greatly reduced. In addition, the volume expansion can lead the silicon monoxide negative electrode material to form a stable SEI film in the electrolyte to be broken, a new active surface is exposed, and a new SEI film is formed on the surface of the newly exposed material, so that a series of problems of electrolyte consumption, material corrosion and the like are aggravated, the capacity of the battery is reduced, and the cycle performance is poor.
It follows that how to reduce the volume effect and lower conductivity of the siliconoxide negative electrode during cycling is crucial to improve the electrochemical performance of the siliconoxide negative electrode.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, an object of the present invention is to propose a method of preparing a negative active material for a lithium battery, a negative active material prepared by the method, and a lithium battery containing the negative active material. According to the method for preparing the lithium battery negative electrode active material, the silicon oxide material is coated for the second time, so that the problem that particle pulverization failure is caused by volume change of the silicon oxide material in the lithium removal/insertion process can be effectively relieved, the consumption of electrolyte and the corrosion of the material are reduced, in addition, the electronic conductivity of the negative electrode material can be effectively improved, and the cycle performance and the rate performance of the lithium battery silicon negative electrode are improved.
In one aspect of the present invention, a method of preparing a negative active material for a lithium battery is provided. According to an embodiment of the invention, the method comprises: (1) mixing silica with a solvent to obtain a first silica dispersion; mixing graphene oxide with a solvent to obtain a first graphene oxide dispersion liquid; (2) mixing the first SiO dispersion with the first graphene oxide dispersion to obtain a first product; (3) mixing the first product with a binder and a solvent, and performing granulation treatment to obtain silica microparticles; (4) mixing the silica microparticles with a solvent to obtain a second silica dispersion; mixing graphene oxide with a solvent to obtain a second graphene oxide dispersion liquid; (5) mixing the second silica dispersion with the second graphene oxide dispersion and a reducing agent to obtain a second product; (6) and calcining the second product to obtain the negative active material.
According to the method for preparing the negative active material of the lithium battery, disclosed by the embodiment of the invention, the silicon oxide is coated with the graphene oxide for the second time, and the graphene oxide is reduced by using the reducing agent, so that the graphene secondary-coated silicon oxide material can be obtained. Through the secondary coating of the graphene, the volume change of the silicon oxide material in the lithium removal/insertion process can be effectively relieved, the stability of the material is obviously improved, and the pulverization failure of the silicon oxide particles is avoided, so that the loss of electrolyte and active substances and the corrosion of the material are relieved. In addition, the negative active material has better electronic conductivity, and can effectively improve the cycle performance and rate performance of the silicon oxide negative electrode of the lithium battery.
In addition, the method of preparing the negative active material for a lithium battery according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the present invention, the average particle size of the silica is 15 to 25 nm.
In some embodiments of the invention, the mass ratio of the silicon monoxide to the graphene oxide is 100 (0.1-2).
In some embodiments of the invention, the mass ratio of the first product to the binder is 100 (0.5-2).
In some embodiments of the present invention, the binder comprises at least one selected from styrene-butadiene rubber, polyvinyl alcohol, hydroxymethylcellulose salt, polyacrylic acid, polyacrylate and its derivatives, polyacrylonitrile, acrylate-acrylonitrile copolymer, polymethylmethacrylate.
In some embodiments of the invention, the granulation process comprises a closed cycle spray drying process.
In some embodiments of the present invention, the average particle size of the fine silica particles is 5 to 15 μm.
In some embodiments of the invention, the reducing agent comprises at least one of hydrazine hydrate, sodium borohydride.
In some embodiments of the invention, the solvent comprises at least one selected from the group consisting of water, ethanol, propanol, and isopropanol.
In some embodiments of the present invention, the mass ratio of the silica particles to the graphene oxide is 100 (0.1-2).
In some embodiments of the present invention, the calcination is performed at 100-800 ℃ for 3-8 hours.
In another aspect of the present invention, the present invention provides a negative active material for a lithium battery. According to the embodiment of the present invention, the negative active material is prepared by the method of preparing the negative active material for a lithium battery of the above embodiment. Therefore, on the basis of having excellent electrochemical performance of the silicon oxide material, the negative active material is subjected to secondary coating by the graphene, so that the volume change in the lithium removal/insertion process is small, the stability is high, and the negative active material is not easy to pulverize and lose efficacy, thereby relieving the loss of electrolyte and active substances and the corrosion of the material. In addition, the negative active material has better electronic conductivity, and can effectively improve the cycle performance and rate performance of the silicon oxide negative electrode of the lithium battery.
In yet another aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery includes: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder. The negative electrode includes: an anode current collector and an anode material supported on the anode current collector, the anode material comprising: the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder of the above examples. Thus, the lithium battery has all the features and advantages described above for the negative active material, and thus, the description thereof is omitted. In general, the lithium battery has excellent electrochemical properties such as cycle performance, rate performance and the like.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic flow chart of a method of preparing a negative active material for a lithium battery according to one embodiment of the present invention;
FIG. 2 shows the results of cycle performance tests of batteries fabricated using the negative active materials prepared in example 1 and comparative examples 1 to 3;
fig. 3 shows the results of rate performance tests of batteries made of the negative electrode active materials prepared in example 1 and comparative examples 1 to 3.
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In one aspect of the present invention, a method of preparing a negative active material for a lithium battery is provided. According to an embodiment of the invention, the method comprises: (1) mixing silica with a solvent to obtain a first silica dispersion; mixing graphene oxide with a solvent to obtain a first graphene oxide dispersion liquid; (2) mixing the first SiO dispersion liquid with the first graphene oxide dispersion liquid to obtain a first product; (3) mixing the first product with a binder and a solvent, and performing granulation treatment to obtain silica particles; (4) mixing the silica particles with a solvent to obtain a second silica dispersion; mixing graphene oxide with a solvent to obtain a second graphene oxide dispersion liquid; (5) mixing the second silica dispersion with the second graphene oxide dispersion and a reducing agent to obtain a second product; (6) and calcining the second product to obtain the cathode active material.
According to the method for preparing the negative active material of the lithium battery, disclosed by the embodiment of the invention, the silicon oxide is coated with the graphene oxide for the second time, and the graphene oxide is reduced by using the reducing agent, so that the graphene secondary-coated silicon oxide material can be obtained. Through the secondary coating of the graphene, the volume change of the silicon oxide material in the lithium removal/insertion process can be effectively relieved, the stability of the material is obviously improved, and the pulverization failure of the silicon oxide particles is avoided, so that the loss of electrolyte and active substances and the corrosion of the material are relieved. In addition, the negative active material has better electronic conductivity, and can effectively improve the cycle performance and rate performance of the silicon oxide negative electrode of the lithium battery.
The method of preparing the negative active material for a lithium battery according to an embodiment of the present invention is further described in detail below. According to an embodiment of the invention, the method comprises:
s100: obtaining a first SiO dispersion and a first graphene oxide dispersion
In the step, the silicon monoxide is mixed with a solvent to obtain a first silicon monoxide dispersion liquid; and mixing the graphene oxide with a solvent to obtain a first graphene oxide dispersion liquid. In the above mixing, the ratio of the silica, the graphene oxide and the solvent is not particularly limited, and those skilled in the art can select the ratio according to actual needs.
According to some embodiments of the present invention, the average particle size of the silica is 15 to 25nm, such as 15nm, 20nm, 25nm, and the like. Before the first SiO dispersion is prepared, the SiO is ball milled and milled to the above particle size. Therefore, the specific surface area of the silicon oxide can be further increased, and the coating of the surface of the graphene oxide is further facilitated. In addition, the specific operating conditions of the ball milling are not particularly limited, and can be selected by those skilled in the art according to actual needs. In some embodiments of the present invention, the silica and the solvent may be put into a ball mill according to a certain ratio, the beads are added for ball milling, then the silica with the target particle size is obtained by washing and filtering, and the material for preparing the silica dispersion is obtained by vacuum drying. According to the specific example of the invention, the silicon monoxide and the solvent can be mixed according to the mass ratio of 1 (10-30), and the diameter of the grinding bead can be 1-3 mm. Therefore, the ball milling effect is better.
According to some embodiments of the present invention, the solvent may include at least one selected from the group consisting of water, ethanol, propanol, and isopropanol. The solvent used for preparing the first silicon monoxide dispersion liquid is preferably water, the solvent used for preparing the first graphene monoxide dispersion liquid is preferably a mixed solvent of water and the organic solvent, and the solvent used for ball milling the silicon monoxide is preferably the organic solvent.
S200: one-time coating
In the step, the first silicon monoxide dispersion liquid and the first graphene oxide dispersion liquid are mixed, so that graphene oxide is coated on the surface of silicon monoxide, and a first product is obtained. Specifically, the first graphene oxide dispersion solution may be added to the first silicon oxide dispersion solution, stirred at room temperature for 4-8 hours, and then filtered and dried to obtain a graphene oxide-coated silica material (i.e., a first product).
According to some embodiments of the present invention, the mass ratio of the silicon monoxide to the graphene oxide is 100 (0.1-2), such as 100:0.1, 100:0.5, 100:1, 100:1.5, 100:2, and the like. That is, the mixing ratio of the first SiO dispersion and the first graphene oxide dispersion is determined such that the mass ratio of SiO in the first SiO dispersion to graphene oxide in the first graphene oxide dispersion is 100 (0.1-2). By mixing the first silicon oxide dispersion liquid and the first graphene oxide dispersion liquid according to the above ratio, the coating effect of graphene oxide on the surface of the silicon oxide can be further improved.
S300: granulation treatment
In this step, the first product is mixed with a binder and a solvent, and subjected to granulation treatment to obtain fine silica particles. Therefore, the particles with larger particle size can be prepared from the silicon oxide coated with the graphene oxide for the second coating of the graphene oxide. In some embodiments of the present invention, after mixing the first product with the binder and the solvent, ultrasonic dispersion may be assisted to further improve the dispersion effect of the material.
According to some embodiments of the invention, the mass ratio of the first product to the binder may be 100 (0.5-2), such as 100:0.5, 100:0.75, 100:1, 100:1.5, 100:2, and the like. The inventor finds in research that if the dosage of the binder is too low, the primary coating amount is less, the coating effect is not obvious, and the performance of the final product as a negative active material is affected; if the amount of the binder is too high, the electrical properties of the material may be affected.
According to some embodiments of the present invention, the binder may include at least one selected from the group consisting of styrene-butadiene rubber, polyvinyl alcohol, a hydroxymethylcellulose salt, polyacrylic acid, polyacrylate and its derivatives, polyacrylonitrile, an acrylate-acrylonitrile copolymer, and polymethylmethacrylate. The adhesive has wide source, low cost and easy obtaining, has good adhesive effect on the first product, and has small influence on the electrical property of the material.
According to some embodiments of the invention, the granulation process comprises a closed cycle spray drying process. The first product, the binder and the solvent are mixed and granulated through closed circulation spray drying treatment, the product granularity is easy to control, and no external impurity is introduced into the material.
According to some embodiments of the present invention, the average particle size of the silica fine particles is 5 to 15 μm, for example, 5 μm, 10 μm, 15 μm, or the like.
According to some embodiments of the present invention, the solvent may include at least one selected from the group consisting of water, ethanol, propanol and isopropanol, preferably one of ethanol, propanol and isopropanol. This improves the granulation effect.
S400: obtaining a second silica dispersion and a second graphene oxide dispersion
In this step, the silica fine particles are mixed with a solvent to obtain a second silica dispersion; and mixing the graphene oxide with a solvent to obtain a second graphene oxide dispersion liquid. In the above mixing, the ratio of the fine silica particles, the graphene oxide, and the solvent is not particularly limited, and those skilled in the art can select the ratio according to actual needs.
According to some embodiments of the present invention, the solvent may include at least one selected from the group consisting of water, ethanol, propanol, and isopropanol. The solvent used for preparing the second silica dispersion is preferably water, the solvent used for preparing the second graphene oxide dispersion is preferably a mixed solvent of water and the above organic solvent, and the solvent used for ball milling silica is preferably the above organic solvent.
S500: secondary coating
In the step, the second silica dispersion liquid, the second graphene oxide dispersion liquid and a reducing agent are mixed so that graphene oxide is coated on the surface of the silica particles, and graphene oxide introduced in the secondary coating and the primary coating is reduced to graphene under the action of the reducing agent, so that a second product is obtained. Specifically, the second graphene oxide dispersion liquid can be added into the second silica oxide dispersion liquid, stirred at room temperature for 4-8 hours, and then filtered and dried to obtain a graphene secondary-coated silica oxide material (i.e., a second product).
According to some embodiments of the present invention, the reducing agent may include at least one of hydrazine hydrate and sodium borohydride. By adopting the reducing agent, the reduction effect of the graphene oxide can be further improved, the graphene oxide can be easily removed from a reaction system, and impurities cannot be introduced into a product.
According to some embodiments of the present invention, the mass ratio of the silica particles to the graphene oxide is 100 (0.1-2), such as 100:0.1, 100:0.5, 100:1, 100:1.5, 100:2, and the like. That is, the mixing ratio of the second silica dispersion liquid and the second graphene oxide dispersion liquid is determined such that the mass ratio of the silica fine particles in the second silica dispersion liquid to the graphene oxide in the second graphene oxide dispersion liquid is 100 (0.1 to 2). By mixing the second silica dispersion liquid and the second graphene oxide dispersion liquid in the above ratio, the coating effect of graphene oxide on the surface of the silica fine particles can be further improved.
S600: calcination treatment
In this step, the second product is calcined to obtain a negative electrode active material. Specifically, the above calcination treatment is performed in an inert gas (e.g., nitrogen, helium, argon) atmosphere. By calcining the second product, the stability of the graphene coated on the surface of the silicon oxide can be obviously improved.
According to some embodiments of the present invention, the calcination treatment can be performed at 100-800 ℃ for 3-8 hours. Specifically, the calcination temperature may be 100 degrees celsius, 200 degrees celsius, 400 degrees celsius, 600 degrees celsius, 800 degrees celsius, or the like, and the calcination time may be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or the like. By performing the calcination treatment under the above conditions, the stability of the graphene coating on the surface of the silicon oxide can be further improved.
In another aspect of the present invention, the present invention provides a negative active material for a lithium battery. According to the embodiment of the present invention, the negative active material is prepared by the method of preparing the negative active material for a lithium battery of the above embodiment. Therefore, on the basis of having excellent electrochemical performance of the silicon oxide material, the negative active material is subjected to secondary coating by the graphene, so that the volume change in the lithium removal/insertion process is small, the stability is high, and the negative active material is not easy to pulverize and lose efficacy, thereby relieving the loss of electrolyte and active substances and the corrosion of the material. In addition, the negative active material has better electronic conductivity, and can effectively improve the cycle performance and rate performance of the silicon oxide negative electrode of the lithium battery.
In yet another aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery includes: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder. The negative electrode includes: an anode current collector and an anode material supported on the anode current collector, the anode material comprising: the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder of the above examples. Thus, the lithium battery has all the features and advantages described above for the negative active material, and thus, the description thereof is omitted. In general, the lithium battery has excellent electrochemical properties such as cycle performance, rate performance and the like.
According to some embodiments of the present invention, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is not particularly limited, and may be selected according to actual needs. The specific kinds of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder are not particularly limited, and for example, the positive electrode active material may be LiCoO2、LiMn2O4、LiMnO2、Li2MnO4、LiFePO4NCM ternary positive electrode material, NCA ternary positive electrode material and the like; the positive electrode conductive agent can be at least one of common positive electrode binders such as conductive carbon black SP or ECP, carbon nano tubes (CNT or WCNT), graphene and the like; the positive binder can be polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC) or butylAt least one of common positive electrode binders such as Styrene Butadiene Rubber (SBR) and polyacrylic acid (PAA). The positive electrode material may further include a common solvent (e.g., NMP) for mixing the positive electrode material, and the ratio of the solvent to the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is not particularly limited, and may be selected by those skilled in the art according to actual needs.
According to some embodiments of the present invention, the mass ratio of the above-described anode active material, anode conductive agent, and anode binder to the thickening stabilizer is not particularly limited and may be selected according to actual needs. The specific types of the negative electrode conductive agent and the negative electrode binder are not particularly limited, and the negative electrode conductive agent can be at least one of common negative electrode conductive agents such as conductive carbon black SP or ECP, carbon nanotubes (CNT or WCNT), graphene and the like; the negative electrode binder may be at least one of common negative electrode binders such as polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), and the like. In addition, the negative electrode material may further include a common solvent (e.g., NMP, deionized water, etc.) for mixing the negative electrode material, and the solvent is not particularly limited and may be selected by those skilled in the art according to actual needs.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.
Example 1
(1) Adding 5g of silica with the average particle size of 60nm into 50g of ethanol, ball-milling for 18h by using milling beads with the diameter of 1mm, washing and filtering to obtain silica with the average particle size of 20 nm;
(2) mixing the silicon monoxide obtained by ball milling in the step (1) with deionized water to obtain a first silicon monoxide dispersion liquid; mixing 50mg of graphene oxide with 5mL of ethanol and 5mL of deionized water to obtain a first graphene oxide dispersion liquid;
(3) adding the first graphene oxide dispersion liquid into the first silicon oxide dispersion liquid, stirring for 6 hours at room temperature, and then filtering and drying to obtain a silicon oxide material (namely a first product) coated with graphene oxide for one time;
(4) mixing the first product with 50mg of acrylate-acrylonitrile copolymer and a solvent, and carrying out closed cycle spray drying to obtain silica particles with the average particle size of 10 mu m;
(5) mixing the silica particles with a solvent to obtain a second silica dispersion; mixing 50mg of graphene oxide with 5mL of ethanol and 5mL of deionized water to obtain a second graphene oxide dispersion liquid;
(6) adding the second graphene oxide dispersion liquid into the second silicon oxide dispersion liquid, stirring for 6 hours at room temperature, adding 5 drops of hydrazine hydrate, and filtering and drying to obtain a graphene secondary coated silicon oxide material (namely a second product);
(7) and calcining the second product at 500 ℃ for 4h in a nitrogen atmosphere to obtain the anode active material 1 #.
Comparative example 1
(1) Adding 5g of silica with the average particle size of 60nm into 50g of ethanol, ball-milling for 18h by using milling beads with the diameter of 1mm, washing and filtering to obtain silica with the average particle size of 20 mu m;
(2) mixing the silicon monoxide obtained by ball milling in the step (1) with deionized water to obtain a first silicon monoxide dispersion liquid; mixing 50mg of graphene oxide with 5mL of ethanol and 5mL of deionized water to obtain a first graphene oxide dispersion liquid;
(3) adding the first graphene oxide dispersion liquid into the first silicon oxide dispersion liquid, stirring for 6 hours at room temperature, adding 5 drops of hydrazine hydrate, and filtering and drying to obtain a graphene primary coated silicon oxide material;
(4) and (4) calcining the product obtained in the step (3) at 500 ℃ for 4 hours in a nitrogen atmosphere to obtain the cathode active material No. 2.
Comparative example 2
(1) Mixing silicon monoxide with the average grain diameter of 10 mu m with deionized water to obtain a first silicon monoxide dispersion liquid; mixing 50mg of graphene oxide with 5mL of ethanol and 5mL of deionized water to obtain a first graphene oxide dispersion liquid;
(2) adding the first graphene oxide dispersion liquid into the first silicon oxide dispersion liquid, stirring for 6 hours at room temperature, adding 5 drops of hydrazine hydrate, and filtering and drying to obtain a graphene primary coated silicon oxide material;
(3) and (3) calcining the product obtained in the step (2) at 500 ℃ for 4h in a nitrogen atmosphere to obtain the cathode active material # 3.
Comparative example 3
Test example
Negative electrode active materials (1#, 2#, 3#, and 4#) prepared in example 1 and comparative examples 1 to 3 were used to prepare button cells for testing, and then rate performance testing and cycle performance testing were performed, and the results are shown in fig. 2 and 3, respectively.
The test result shows that the rate performance and the cycle performance of the battery made of the negative active material prepared by the embodiment of the invention are obviously improved compared with those of a comparative example. As can be seen from comparative examples 1 and 2, the negative active material # 3 is slightly better than # 2 in terms of cycle performance, which may be due to the easy agglomeration of nanoparticles, large volume expansion during the cycle, resulting in particle pulverization, low conductivity, and poor cycle performance.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method of preparing a negative active material for a lithium battery, comprising:
(1) mixing silica with a solvent to obtain a first silica dispersion; mixing graphene oxide with a solvent to obtain a first graphene oxide dispersion liquid;
(2) mixing the first SiO dispersion with the first graphene oxide dispersion to obtain a first product;
(3) mixing the first product with a binder and a solvent, and performing granulation treatment to obtain silica microparticles;
(4) mixing the silica microparticles with a solvent to obtain a second silica dispersion; mixing graphene oxide with a solvent to obtain a second graphene oxide dispersion liquid;
(5) mixing the second silica dispersion with the second graphene oxide dispersion and a reducing agent to obtain a second product;
(6) and calcining the second product to obtain the negative active material.
2. The method according to claim 1, wherein the average particle size of the silica is 15 to 25 nm.
3. The method according to claim 1, wherein the mass ratio of the silicon monoxide to the graphene oxide is 100 (0.1-2);
optionally, the mass ratio of the silicon monoxide particles to the graphene oxide particles is 100 (0.1-2).
4. The method according to claim 1, wherein the mass ratio of the first product to the binder is 100 (0.5-2);
optionally, the binder includes at least one selected from styrene-butadiene rubber, polyvinyl alcohol, hydroxymethylcellulose salt, polyacrylic acid, polyacrylate and its derivatives, polyacrylonitrile, acrylate-acrylonitrile copolymer, and polymethylmethacrylate.
5. The method according to claim 1, characterized in that said granulation process comprises a closed cycle spray-drying process;
optionally, the average particle diameter of the silica fine particles is 5 to 15 μm.
6. The method of claim 1, wherein the reducing agent comprises at least one of hydrazine hydrate, sodium borohydride.
7. The method of claim 1, wherein the solvent comprises at least one selected from the group consisting of water, ethanol, propanol, and isopropanol.
8. The method according to claim 1, wherein the calcination treatment is performed at 100 to 800 ℃ for 3 to 8 hours.
9. A negative active material for a lithium battery, wherein the negative active material is prepared by the method of any one of claims 1 to 8.
10. A lithium battery, comprising: a positive electrode, a negative electrode, a separator and an electrolyte; wherein the content of the first and second substances,
the positive electrode includes: a positive current collector and a positive electrode material supported on the positive current collector, the positive electrode material comprising: a positive electrode active material, a positive electrode conductive agent and a positive electrode binder.
The negative electrode includes: an anode current collector and an anode material supported on the anode current collector, the anode material comprising: the negative active material, the negative conductive agent, and the negative binder of claim 9.
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