CN113540416A - Solid electrolyte coated graphite composite material, preparation method and application thereof, and lithium ion battery - Google Patents

Solid electrolyte coated graphite composite material, preparation method and application thereof, and lithium ion battery Download PDF

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CN113540416A
CN113540416A CN202110771316.0A CN202110771316A CN113540416A CN 113540416 A CN113540416 A CN 113540416A CN 202110771316 A CN202110771316 A CN 202110771316A CN 113540416 A CN113540416 A CN 113540416A
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solid electrolyte
composite material
graphite
layer
core
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徐军红
陈和平
陈玉
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LUOYANG YUEXING NEW ENERGY TECHNOLOGY CO LTD
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LUOYANG YUEXING NEW ENERGY 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/08—Oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/223—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating specially adapted for coating particles
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light 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
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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 belongs to the field of lithium ion battery preparation, and particularly discloses a solid electrolyte coated graphite composite material, a preparation method and application thereof, and a lithium ion battery. The intermediate layer containing the solid electrolyte is arranged between the graphite core and the carbon layer, because the solid electrolyte is in a cubic structure, and has more lithium ion embedding passages and stable structure, the solid electrolyte is coated on the graphite surface, so that the conduction rate of lithium ions can be improved by using an artificial electrolyte membrane formed by the solid electrolyte on one hand, and the transmission rate of electrons can be improved by using the amorphous carbon layer on the outermost layer on the other hand, and the quick charge performance and the safety performance of the composite material are improved. The invention adopts the magnetron sputtering method to deposit the solid electrolyte composite material, which can obviously improve the structural stability and the quick charging performance of the material shell; in addition, the amorphous carbon layer on the outermost layer can effectively prevent the electrolyte from directly contacting with the electrolyte, and reduce the occurrence of side reactions, thereby improving the storage performance and the cycle performance of the composite material.

Description

Solid electrolyte coated graphite composite material, preparation method and application thereof, and lithium ion battery
Technical Field
The invention belongs to the field of lithium ion battery preparation, and particularly relates to a solid electrolyte coated graphite composite material, a preparation method and application thereof, and a lithium ion battery.
Background
With the increasing demand of the market on the quick charge capacity and the mileage of the lithium ion battery, the quick charge performance of the lithium ion battery cathode material is required to be greatly improved while the lithium ion battery cathode material has high energy density. The current commercialized negative electrode material mainly takes graphite material as main material, and the surface coating material is soft carbon or hard carbon formed by carbonizing asphalt or resin. As the lithium ion is mainly inserted/extracted along the interlayer of the material in the charging and discharging processes of the material, the problems of long path, easy expansion and the like exist, and the rate performance deviation and the volume expansion of the material are serious.
In order to solve the problem, chinese patent CN105529466B discloses an amorphous carbon coated graphite composite material for lithium pre-storage, which comprises the following steps: 1) mixing a template agent and an acrylonitrile monomer, and adding an initiator to perform a polymerization reaction to obtain a template agent/polyacrylonitrile composite material; dispersing graphite and an emulsifier in water to obtain a graphite mixture; 2) adding the template agent/polyacrylonitrile composite material into the graphite mixture for an emulsion reaction, adding acid liquor for etching after the reaction to remove the template agent, and obtaining the porous polyacrylonitrile/graphite composite material; 3) and soaking the porous polyacrylonitrile/graphite composite material in a lithium-containing solution for lithium storage in advance, taking out the porous polyacrylonitrile/graphite composite material, drying and cracking the porous polyacrylonitrile/graphite composite material to obtain the amorphous carbon-coated graphite composite material with lithium storage in advance. The composite material has the advantages of large interlayer spacing, high gram capacity, strong liquid absorption and retention capacity and the like, and the micropore lithium storage is utilized in advance, so that the consumption of lithium can be reduced, and the specific capacity of the lithium ion battery is improved. However, the cycle performance of the composite material prepared by the patent still needs to be improved. In addition, chinese patent application CN107768595A discloses a negative electrode plate of a lithium ion battery, in which a thin solid electrolyte layer (solid electrolyte is selected from Li) is disposed on a negative active layer (active material is graphite, silicon or lithium titanate) of the negative electrode platexPOyNz、Li3N, perovskite, LISICON, NASICON or modified materials thereof), wherein the thin film stateThe solid electrolyte layer is used as a protective layer, so that the reaction between lithium ions and electrolyte can be effectively inhibited, the capacity loss of the battery in the aging process is reduced, and the storage life and the cycle life of the battery are prolonged. However, the application only improves the power performance and energy density of the battery through the negative pole piece, and does not improve the energy density and fast charge power performance of the battery from the perspective of the material.
Disclosure of Invention
The invention aims to provide a solid electrolyte coated graphite composite material, which solves the problems of poor multiplying power performance and poor cycle performance of a negative electrode material.
Secondly, the invention provides a preparation method of the solid electrolyte coated graphite composite material.
The invention further provides an application of the solid electrolyte coated graphite composite material in preparation of a lithium ion battery.
Finally, the invention provides a lithium ion battery using the solid electrolyte coated graphite composite material.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the composite material is of a core-shell structure, a core of the core-shell structure comprises graphite, a shell is sequentially provided with a first outer shell layer and a second outer shell layer from inside to outside, the first outer shell layer comprises solid electrolyte, and the second outer shell layer is a carbon layer.
The intermediate layer containing the solid electrolyte is arranged between the graphite core and the carbon layer, because the solid electrolyte is in a cubic structure, and has more lithium ion embedding passages and stable structure, the solid electrolyte is coated on the graphite surface, so that the conduction rate of lithium ions can be improved by using an artificial electrolyte membrane formed by the solid electrolyte on one hand, and the transmission rate of electrons can be improved by using the amorphous carbon layer on the outermost layer on the other hand, and the quick charge performance and the safety performance of the composite material are greatly improved.
In a preferred embodiment, the thickness ratio of the inner core to the first and second outer shells is 100 (5-10) to (1-5).
As a preferred embodiment, the solid electrolyte is selected from Li1.3Al0.3Ti1.7(PO4)3、Li0.35La0.55TiO3、Li7La3Zr2O12One or more of (a).
As a preferred embodiment, the inner core is mainly composed of graphite and a binder. The binder is preferably polyvinylidene fluoride (PVDF). The mass ratio of the graphite to the polyvinylidene fluoride is (80-100) to (5-20), and preferably 90: 10. The preparation method of the inner core comprises the following steps: mixing graphite (such as artificial graphite and natural graphite) and binder, and pressing into block.
As a preferred embodiment, the first outer shell layer is mainly composed of a solid electrolyte, carbon nanotubes, and a conductive polymer. The mass ratio of the solid electrolyte, the carbon nano tube and the conductive polymer is (50-80): (10-30): 10-20). Further preferably, the mass ratio of the solid electrolyte, the carbon nano tube and the conductive polymer is (50-60): (10-30): (10-20). The conductive polymer is selected from one or more of polyaniline, polythiophene and polypyrrole.
In a preferred embodiment, the first outer shell layer is prepared by a magnetron sputtering method, an inner core containing graphite is used as a substrate, a composite material containing a solid electrolyte is used as a target material, and the solid electrolyte composite material is implanted into a surface layer of a graphite bulk material, wherein the deposition thickness is 100-500 nm. Further preferably, the preparation method of the composite material containing the solid electrolyte comprises the following steps: the solid electrolyte, the carbon nano tube and the conductive polymer are uniformly mixed and pressed into a block material.
As a preferred embodiment, the conditions for preparing the first outer shell layer by using the magnetron sputtering method are as follows: in a closed environment, adjusting the distance between the substrate and the target to be 5-15cm, and adjusting the included angle between the substrate and the horizontal plane to be 3-10 degrees (preferably 5 degrees); vacuumizing the closed environment, and introducing inert gas into the closed environment to serve as sputtering gas; controlling the air pressure of the closed environment to be 0.1-0.5Pa, and performing magnetron sputtering for 30-120min by using a direct current sputtering source. Further preferably, the vacuuming treatment is performed under the condition that the air pressure is reduced to 2 x 10-4-5×10-4And introducing inert gas into the closed environment after Pa. The inert gas is argon, and the gas flow is 10-100 sccm.
In a preferred embodiment, the carbon layer is an amorphous carbon layer. The amorphous carbon layer is obtained by carbonizing a mixed liquid containing a resin. The resin is selected from one or more of phenolic resin, furfural resin and epoxy resin. The mixed solution contains resin and organic solvent so as to facilitate coating; the concentration of the resin is 1-10 wt%. The organic solvent is selected from any one of N-methyl pyrrolidone, carbon tetrachloride, cyclohexane, ethylene glycol, dimethylformamide and tetrahydrofuran.
As a preferred embodiment, the temperature of the carbonization treatment is 700-1000 ℃, and the carbonization time is 1-48 h.
As a preferred embodiment, the particle size of the solid electrolyte-coated graphite composite material is 8 to 18 μm.
A preparation method of a solid electrolyte coated graphite composite material comprises the following steps:
(1) preparing a composite material comprising a solid electrolyte;
preparing an inner core comprising graphite;
preparing a mixed solution containing resin;
(2) forming a first shell layer on a core by adopting a magnetron sputtering method, wherein the core comprises graphite as a substrate, and a composite material comprising a solid electrolyte as a target material; and then mixing the mixture with a mixed solution containing resin, drying and carbonizing to form a second outer shell layer.
As a preferred embodiment, in step (1), the method for preparing the composite material comprising the solid electrolyte comprises: and uniformly mixing the solid electrolyte, the carbon nano tube and the conductive polymer, and pressing into a block material to obtain the carbon nano tube material. The solid electrolyte is selected from Li1.3Al0.3Ti1.7(PO4)3、Li0.35La0.55TiO3、Li7La3Zr2O12One or more of (a). The mass ratio of the solid electrolyte, the carbon nano tube and the conductive polymer is (50-80): 10-30): 10-20, preferably (50-60): 10-30): 10-20. The conductive polymer is selected from one or more of polyaniline, polythiophene and polypyrrole. The conductive polymer selected by the invention is of a ring structure, the amorphous carbon formed after carbonization has the characteristics of good isotropy and stable structure, and meanwhile, the carbon nano tubes of the ring structure and the chain structure can mutually form a staggered net structure, so that the structure is very stable, and the cycle performance of the carbon nano tubes can be improved.
According to the invention, the solid electrolyte with high ionic conductivity and the conductive agent with high electronic conductivity are deposited on the surface of the graphite core by adopting a magnetron sputtering method, so that the structural stability and the quick charging performance of the material shell are improved, meanwhile, the amorphous carbon such as hard carbon formed after the resin at the outermost layer is carbonized avoids the direct contact of the electrolyte and the electrolyte, the occurrence of side reactions is reduced, and the storage performance and the cycle performance of the composite material are improved.
As a preferred embodiment, in the step (1), the method for preparing the graphite-containing inner core includes: and uniformly mixing the graphite and the binder, and pressing into a block material to obtain the material. The graphite may be artificial graphite or natural graphite. The binder is preferably polyvinylidene fluoride (PVDF). The mass ratio of the graphite to the polyvinylidene fluoride is (80-100) to (5-20), and preferably 90: 10. The pressing pressure is 1-10T, preferably 5T.
As a preferred embodiment, in the step (1), the method for preparing the mixed solution containing the resin comprises: and (3) uniformly mixing the resin and the organic solvent to obtain the resin. The resin is selected from one or more of phenolic resin, furfural resin and epoxy resin. The organic solvent is selected from any one of N-methyl pyrrolidone, carbon tetrachloride, cyclohexane, ethylene glycol, dimethylformamide and tetrahydrofuran. The concentration of the resin is 1-10 wt%.
As a preferred embodiment, in the step (2), the preparation condition for forming the first outer shell layer by using the magnetron sputtering method is: in the closed environment, the air-conditioning system is arranged,adjusting the distance between the substrate and the target to be 5-15cm, and adjusting the included angle between the substrate and the horizontal plane to be 3-10 degrees (preferably 5 degrees); vacuumizing the closed environment, and introducing inert gas into the closed environment to serve as sputtering gas; controlling the air pressure of the closed environment to be 0.1-0.5Pa, and carrying out magnetron sputtering by a direct current sputtering source for 30-120min so as to implant the composite material containing the solid electrolyte into the surface layer of the inner core containing the graphite, wherein the deposition thickness is 100-500 nm. Further preferably, the vacuuming treatment is performed under the condition that the air pressure is reduced to 2 x 10-4-5×10-4And introducing inert gas into the closed environment after Pa. The inert gas is argon, and the gas flow is 10-100 sccm.
According to the invention, by utilizing the characteristics of controllable preparation process, compact deposition thickness and the like of a magnetron sputtering method, the composite materials such as the solid electrolyte, the conductive agent and the like are deposited on the surface of the graphite core, and the ionic and electronic conductivity of the composite material can be improved under the condition of not influencing the energy density of the material, so that the rate capability and the cycle performance of the composite material are improved.
In a preferred embodiment, in step (2), the mixing is performed by wet ball milling.
As a preferred embodiment, in the step (2), the drying is drying or spray drying, preferably drying.
As a preferred embodiment, in the step (2), the temperature of the carbonization treatment is 700-1000 ℃, and the carbonization time is 1-48 h.
In a preferred embodiment, in the step (2), the thickness ratio of the inner core, the first outer shell layer and the second outer shell layer is 100 (5-10) to (1-5).
An application of a solid electrolyte coated graphite composite material in the preparation of a lithium ion battery. Specifically, the solid electrolyte coated graphite composite material is used as a negative electrode material of a lithium ion battery.
The lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode material layer coated on the surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode material, a conductive agent and a binder, and the negative electrode material adopts the solid electrolyte coated graphite composite material.
The invention has the beneficial effects that:
the intermediate layer containing the solid electrolyte is arranged between the graphite core and the carbon layer, because the solid electrolyte is in a cubic structure, the lithium ion intercalation and deintercalation channels are more, the structure is stable, and the lithium ion intercalation and deintercalation channels are coated on the surface of the graphite core, so that the quick charging performance and the safety performance of the composite material can be greatly improved. The artificial electrolyte membrane formed by the solid electrolyte is used for improving the conduction rate of lithium ions on one hand, and the amorphous carbon layer on the outermost layer is used for improving the transmission rate of electrons on the other hand.
The invention preferably adopts the magnetron sputtering method to deposit the solid electrolyte with high ionic conductivity and the conductive agent with high electronic conductivity on the surface of the graphite core, because the magnetron sputtering method has the characteristics of controllable preparation process, compact deposition thickness and the like, the structural stability and the quick-charging performance of the material shell can be obviously improved under the condition of not influencing the energy density of the material; meanwhile, the outermost layer of the material is formed by hard carbon and other amorphous carbon formed after resin carbonization, so that direct contact between electrolyte and electrolyte can be avoided, and side reactions are reduced, thereby improving the storage performance and the cycle performance of the composite material.
Drawings
Fig. 1 is an SEM image of a solid electrolyte-coated graphite composite material prepared in example 1 of the present invention.
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings obtained in the experimental examples are briefly described above. It is understood that the above-mentioned drawings only show some experimental examples of the present invention and should not be considered as limiting the scope of protection of the claims in any way. For a person skilled in the art, it is possible to derive other relevant figures from these figures without inventive effort.
Detailed Description
In order to make the technical problems to be solved, the technical solutions adopted and the technical effects achieved by the present invention easier to understand, the technical solutions of the present invention are clearly and completely described below with reference to specific examples, comparative examples and experimental examples. It is to be noted that the examples, comparative examples and experimental examples, in which specific conditions are not specified, were conducted according to conventional conditions or conditions recommended by the manufacturers. The reagents, instruments and the like used in examples, comparative examples and experimental examples were all purchased from commercial sources.
Example 1
The solid electrolyte coated graphite composite material is of a core-shell structure, wherein a core of the core-shell structure comprises graphite, a shell is sequentially provided with a first shell layer and a second shell layer from inside to outside, the first shell layer comprises a solid electrolyte and a conductive agent, and the second shell layer is an amorphous carbon layer.
The preparation method of the solid electrolyte coated graphite composite material of the embodiment comprises the following steps:
(1) preparation of a composite comprising a solid electrolyte: 60g of Li1.3Al0.3Ti1.7(PO4)330g of carbon nano tube and 10g of polyaniline are uniformly mixed and then are pressed into a blocky solid electrolyte composite material A by a tablet press under the pressure of 5T;
preparing a core comprising graphite: uniformly mixing 90g of artificial graphite and 10g of PVDF binder, and pressing into a blocky graphite composite material B by a tablet press under the pressure of 5T;
(2) adopting a magnetron sputtering method, taking a blocky solid electrolyte composite material A as a target material and a blocky graphite composite material B as a substrate, arranging the target material and the substrate in a closed environment, adjusting the distance between the substrate and the target material to be 10cm, adjusting the included angle between the substrate and the horizontal plane to be 5 degrees, then vacuumizing the closed environment, and reducing the air pressure in the closed environment to be 3 multiplied by 10-4When Pa is needed, introducing argon gas serving as sputtering gas into the closed environment, wherein the gas flow is 50 sccm; controlling the air pressure of a closed environment to be 0.2Pa, performing magnetron sputtering by a direct-current sputtering source for 90min, implanting the solid electrolyte composite material into the surface layer of the graphite body material, and obtaining a precursor material C with the deposition thickness of 300 nm;
weighing 100g of precursor material C, soaking in 400mL of N-methyl pyrrolidone solution of phenolic resin with the concentration of 5 wt%, then uniformly mixing by wet ball milling, filtering, drying, and carbonizing at 800 ℃ for 25h to obtain the solid electrolyte coated graphite composite material.
Example 2
The solid electrolyte coated graphite composite material is of a core-shell structure, wherein a core of the core-shell structure comprises graphite, a shell is sequentially provided with a first shell layer and a second shell layer from inside to outside, the first shell layer comprises a solid electrolyte and a conductive agent, and the second shell layer is an amorphous carbon layer.
The preparation method of the solid electrolyte coated graphite composite material of the embodiment comprises the following steps:
(1) preparation of a composite comprising a solid electrolyte: 50g of Li7La3Zr2O1230g of carbon nano tube and 20g of polythiophene are uniformly mixed and then are pressed into a blocky solid electrolyte composite material A by a tablet press under the pressure of 5T;
preparing a core comprising graphite: uniformly mixing 90g of artificial graphite and 10g of PVDF binder, and pressing into a blocky graphite composite material B by a tablet press under the pressure of 5T;
(2) adopting a magnetron sputtering method, taking a blocky solid electrolyte composite material A as a target material and a blocky graphite composite material B as a substrate, arranging the target material and the substrate in a closed environment, adjusting the distance between the substrate and the target material to be 5cm, adjusting the included angle between the substrate and the horizontal plane to be 5 degrees, then vacuumizing the closed environment, and reducing the air pressure in the closed environment to 2 multiplied by 10-4When Pa is needed, introducing argon gas serving as sputtering gas into the closed environment, wherein the gas flow is 10 sccm; controlling the air pressure of a closed environment to be 0.1Pa, performing magnetron sputtering by a direct-current sputtering source for 30min, implanting the solid electrolyte composite material into the surface layer of the graphite body material, and obtaining a precursor material C with the deposition thickness of 100 nm;
weighing 100g of precursor material C, soaking in 1000mL of carbon tetrachloride solution of furfural resin with the concentration of 1 wt%, then performing wet ball milling and mixing uniformly, filtering, drying, and carbonizing at 700 ℃ for 48h to obtain the solid electrolyte coated graphite composite material.
Example 3
The solid electrolyte coated graphite composite material is of a core-shell structure, wherein a core of the core-shell structure comprises graphite, a shell is sequentially provided with a first shell layer and a second shell layer from inside to outside, the first shell layer comprises a solid electrolyte and a conductive agent, and the second shell layer is an amorphous carbon layer.
The preparation method of the solid electrolyte coated graphite composite material of the embodiment comprises the following steps:
(1) preparation of a composite comprising a solid electrolyte: 80g of Li7La3Zr2O12After 10g of carbon nano tube and 10g of polypyrrole are uniformly mixed, pressing the mixture into a blocky solid electrolyte composite material A by a tablet press under the pressure of 5T;
preparing a core comprising graphite: uniformly mixing 90g of artificial graphite and 10g of PVDF binder, and pressing into a blocky graphite composite material B by a tablet press under the pressure of 5T;
(2) adopting a magnetron sputtering method, taking a blocky solid electrolyte composite material A as a target material and a blocky graphite composite material B as a substrate, arranging the target material and the substrate in a closed environment, adjusting the distance between the substrate and the target material to be 15cm, adjusting the included angle between the substrate and the horizontal plane to be 5 degrees, then vacuumizing the closed environment, and reducing the air pressure in the closed environment to 5 multiplied by 10-4When Pa is needed, introducing argon gas serving as sputtering gas into the closed environment, wherein the gas flow is 100 sccm; controlling the air pressure of a closed environment to be 0.5Pa, performing magnetron sputtering by a direct-current sputtering source for 120min, implanting the solid electrolyte composite material into the surface layer of the graphite body material, and obtaining a precursor material C with the deposition thickness of 500 nm;
weighing 100g of precursor material C, soaking in 200mL of cyclohexane solution of epoxy resin with the concentration of 10 wt%, then performing wet ball milling and mixing uniformly, filtering, drying, and carbonizing at 1000 ℃ for 1h to obtain the solid electrolyte coated graphite composite material.
In other embodiments of the present invention, the solid electrolyte in step (1) is Li0.35La0.55TiO3。
Comparative example
The carbon-coated graphite composite material of the comparative example is a core-shell structure, the core of the core-shell structure comprises graphite, and the shell is an amorphous carbon layer.
The preparation method of the carbon-coated graphite composite material of the comparative example comprises the following steps:
soaking 100g of artificial graphite in 400mL of cyclohexane solution of epoxy resin with the concentration of 5 wt%, then uniformly mixing by wet ball milling, filtering, drying, and carbonizing at 1000 ℃ for 1h to obtain the carbon-coated graphite composite material.
Examples of the experiments
1 test of physical and chemical Properties
1.1SEM test
SEM test was performed on the solid electrolyte-coated graphite composite material prepared in example 1, and the test results are shown in fig. 1.
As can be seen from FIG. 1, the solid electrolyte coated graphite composite material prepared in the examples has a spheroidal structure, uniform size and a particle size of 8-18 μm.
1.2 powder conductivity test
The solid electrolyte-coated graphite composite materials prepared in examples 1 to 3 and the carbon-coated graphite composite material prepared in the comparative example were subjected to a powder conductivity test, which was performed by the following method: the powder was pressed into a block structure on a powder compaction densitometer at a pressure of 2T, and then a four-probe tester was used for powder conductivity testing, with the test results shown in table 1.
1.3 tap Density test
Similarly, the tap density was tested according to GB/T2433and 2009 graphite-based cathode material for lithium ion batteries, and the test results are shown in Table 1.
TABLE 1 comparison of the physico-chemical properties of the composites prepared in examples 1-3 with those of the comparative example
Item Example 1 Example 2 Example 3 Comparative example
Conductivity (S/cm) 4.13 4.01 3.81 1.84
Tap density (g/cm)3) 1.11 1.09 1.03 0.90
As can be seen from Table 1, the conductivity of the solid electrolyte coated graphite composite material prepared by the magnetron sputtering method of the invention is obviously higher than that of the comparative example, and the reason for this is as follows: the surface of the composite material is coated with the solid electrolyte with higher conductivity, so that the transmission rate of ions/electrons is improved; the outermost dense carbon layer also contributes to the improvement of electron conductivity. Meanwhile, the solid electrolyte coated on the surface of the material has the characteristics of high density, high density and the like, so that the tap density of the material is obviously improved.
2 button cell test
Button cells were assembled from the solid electrolyte-coated graphite composite materials prepared in examples 1 to 3 and the carbon-coated graphite composite material prepared in comparative example, respectivelya1, a2, a3, b 1. The assembling method comprises the following steps: adding a binder, a conductive agent and a solvent into the negative electrode material, stirring and pulping, then coating the slurry on a copper foil, and drying and rolling to prepare a negative electrode sheet; the binder used was LA132 binder, the conductive agent was SP, the negative electrode materials were the composite materials of examples 1 to 3 and comparative example, respectively, and the solvent was secondary distilled water. The proportion of each component is as follows: and (3) anode material: SP: LA 132: 95g of secondary distilled water: 1 g: 4 g: 220 mL; the electrolyte is LiPF6/EC+DEC(LiPF6The concentration of (A) is 1.2mol/L, the volume ratio of EC to DEC is 1:1), the metal lithium sheet is used as a counter electrode, and the diaphragm is made of Polyethylene (PE) (polypropylene (PP) or polyethylene propylene (PEP) composite membrane can also be used). The button cell was assembled in a hydrogen-filled glove box, and the electrochemical performance test was performed on a Wuhan blue CT2001A type cell tester with a charge-discharge voltage range of 0.005V to 2.0V and a charge-discharge rate of 0.1C, with the test results shown in Table 2.
Table 2 comparison of the performance of button cells prepared from the composites of examples 1-3 and comparative example
Item Button cell a1 Button cell a2 Button cell a3 Button cell b1
First discharge capacity (mAh/g) 371.3 369.4 364.5 354.4
First efficiency (%) 97.1 96.8 95.7 93.2
Multiplying power (3C/0.2C) 93.5％ 92.6％ 91.3％ 83.9％
As can be seen from table 2, the first discharge capacity and the first charge-discharge efficiency of the lithium ion battery prepared by using the composite materials of examples 1 to 3 of the present invention are significantly higher than those of the comparative examples, and the reasons for this are as follows: the surface of the graphite core is coated with the solid electrolyte composite material, the intercalation and deintercalation of lithium ions are accelerated by utilizing the characteristic of high lithium ion conductivity of the solid electrolyte, the loss of irreversible capacity of the material is reduced, and the first efficiency is improved. Meanwhile, the high lithium ion conductivity of the solid electrolyte is utilized to improve the rate capability of the button cell.
3 pouch cell testing
Preparing a negative electrode plate by using the solid electrolyte coated graphite composite material prepared in the examples 1 to 3 and the carbon coated graphite composite material prepared in the comparative example as negative electrode materials; with ternary materials (LiNi)1/3Co1/3Mn1/3O2) As a positive electrode material, LiPF6Solution (solvent EC + DEC, volume ratio 1:1, LiPF)6Concentration of 1.3mol/L) as electrolyte and celegard2400 as separator, 5Ah soft package batteries A1, A2, A3 and B1 were prepared. And then testing the cycle performance, the rate performance and the expansion performance of the soft package battery in different states.
Cycle performance test conditions: the charging and discharging current is 1C/1C, the voltage range is 2.8-4.2V, and the cycle times are 500 times.
Multiplying power performance test conditions: the charging multiplying power is 1C/3C/5C/8C, and the discharging multiplying power is 1C; the voltage range is 2.8-4.2V.
Expansion performance test conditions: and (3) at 25 ℃, 1C/1C, fully electrically expanding the negative pole piece in an initial state, and circulating for 500 weeks.
The test results are shown in tables 3, 4 and 5.
Table 3 comparison of cycling performance of pouch cells prepared from composites of examples 1-3 and comparative examples
Figure BDA0003153561940000091
As can be seen from table 3, the cycling performance of the pouch cells prepared using the composites of examples 1-3 was superior to the comparative example for the following reasons: in the aspect of 1C/1C multiplying power cycle performance, the solid electrolyte and the conductive agent deposited on the surface of the graphite core improve the transmission rate of lithium ions; meanwhile, the circulation performance is improved by utilizing the characteristic of stable structure of the solid electrolyte.
Table 4 comparison of rate charge performance of pouch cells prepared from composites of examples 1-3 and comparative example
Figure BDA0003153561940000092
Figure BDA0003153561940000101
As can be seen from table 4, the pouch cells prepared using the composites of examples 1-3 had better constant current ratios for the following reasons: the solid electrolyte is coated on the surface of the graphite inner core, so that the lithium ion intercalation and deintercalation rate of the material in the multiplying power charging process is improved, and the multiplying power charging performance is improved.
Table 5 comparison of swelling properties of pouch cells prepared from composites of examples 1-3 and comparative examples
Item Initial negative pole piece full electric expansion 500 weeks of full charge expansion of negative pole piece
Laminate polymer battery A1 23.8％ 31.9％
Laminate polymer battery A2 24.9％ 31.5％
Laminate polymer battery A3 25.1％ 32.1％
Soft-package battery B1 26.7％ 37.4％
As can be seen from table 5, the negative full electrical expansion (initially and after 500 cycles) of the pouch cells prepared with the composites of examples 1-3 is significantly lower than the comparative examples for the following reasons: in examples 1 to 3, the solid electrolyte can be firmly implanted into the surface layer of the graphite core by the magnetron sputtering method, the material structure is stable, expansion caused by lithium ion intercalation in the charging and discharging processes is restrained, and the expansion caused by lithium ion intercalation in the material can be further restrained by the double-shell structure.
The method comprises the steps of firstly depositing the solid electrolyte on the surface of graphite by adopting a magnetron sputtering mode, then soaking the graphite in a resin solution, drying and carbonizing to obtain the solid electrolyte-coated graphite composite material. The composite material utilizes the artificial electrolyte membrane formed by the solid electrolyte to improve the conduction rate of lithium ions, utilizes the amorphous carbon on the outer layer to improve the electron transmission rate, and the magnetron sputtering method has the characteristics of controllable preparation process, compact deposition thickness and the like, so that the rate capability and the cycle performance of the composite material are effectively improved under the condition of not influencing the energy density of the material.
The above are only preferred examples and experimental examples of the present invention, and do not limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the invention as embodied and described. Any modification, replacement (equivalent), improvement and the like made within the spirit of the present invention should be included in the scope of protection of the present invention.

Claims (10)

1. A solid electrolyte coated graphite composite material is characterized in that: the composite material is of a core-shell structure, the core of the core-shell structure comprises graphite, the shell is sequentially provided with a first shell layer and a second shell layer from inside to outside, the first shell layer comprises solid electrolyte, and the second shell layer is a carbon layer.
2. The solid electrolyte-coated graphite composite material according to claim 1, characterized in that: the thickness ratio of the inner core to the first outer shell layer to the second outer shell layer is 100 (5-10) to (1-5); and/or the solid electrolyte is selected from Li1.3Al0.3Ti1.7(PO4)3、Li0.35La0.55TiO3、Li7La3Zr2O12One or more of (a).
3. The solid electrolyte-coated graphite composite material according to claim 1, characterized in that: the inner core mainly comprises graphite and a binder; the binder is polyvinylidene fluoride, the mass ratio of the graphite to the polyvinylidene fluoride is (80-100) to (5-20), and the preferred mass ratio is 90: 10; and/or the first shell layer consists essentially of a solid electrolyte, carbon nanotubes, and a conductive polymer; the mass ratio of the solid electrolyte, the carbon nano tube and the conductive polymer is (50-80): 10-30): 10-20, preferably (50-60): 10-30): 10-20; the conductive polymer is selected from one or more of polyaniline, polythiophene and polypyrrole; and/or the carbon layer is an amorphous carbon layer which is obtained by carbonizing a mixed solution containing resin; the resin is selected from one or more of phenolic resin, furfural resin and epoxy resin.
4. The solid electrolyte-coated graphite composite material according to claim 1, characterized in that: the first shell layer is prepared by adopting a magnetron sputtering method, an inner core containing graphite is used as a substrate, and a composite material containing solid electrolyte is used as a target material; the preparation conditions are as follows: in a closed environment, adjusting the distance between the substrate and the target material to be 5-15cm, and adjusting the included angle between the substrate and the horizontal plane to be 3-10 degrees; vacuumizing the closed environment, and introducing inert gas into the closed environment to serve as sputtering gas; controlling the air pressure of a closed environment to be 0.1-0.5Pa, carrying out magnetron sputtering by a direct current sputtering source for 30-120min, implanting the composite material containing the solid electrolyte into the surface layer of the core containing the graphite, and depositing the composite material with the thickness of 100-500 nm; and/or the temperature of the carbonization treatment is 700-1000 ℃, and the carbonization time is 1-48 h.
5. A preparation method of a solid electrolyte coated graphite composite material is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a composite material comprising a solid electrolyte;
preparing an inner core comprising graphite;
preparing a mixed solution containing resin;
(2) forming a first shell layer on a core by adopting a magnetron sputtering method, wherein the core comprises graphite as a substrate, and a composite material comprising a solid electrolyte as a target material; and then mixing the mixture with a mixed solution containing resin, drying and carbonizing to form a second outer shell layer.
6. The method for producing a solid electrolyte-coated graphite composite material according to claim 5, characterized in that: in the step (1), the preparation method of the composite material containing the solid electrolyte comprises the following steps: uniformly mixing the solid electrolyte, the carbon nano tube and the conductive polymer, and pressing into a block material; the solid electrolyte is selected from Li1.3Al0.3Ti1.7(PO4)3、Li0.35La0.55TiO3、Li7La3Zr2O12One or more of; the mass ratio of the solid electrolyte, the carbon nano tube and the conductive polymer is (50-80): 10-30): 10-20, preferably (50-60): 10-30): 10-20; the conductive polymer is selected from one or more of polyaniline, polythiophene and polypyrrole; and/or the presence of a gas in the gas,
in the step (1), the preparation method of the graphite-containing core comprises the following steps: uniformly mixing graphite and a binder, and pressing into a block material; the binder is polyvinylidene fluoride, the mass ratio of the graphite to the polyvinylidene fluoride is (80-100) to (5-20), and the preferred mass ratio is 90: 10; and/or the presence of a gas in the gas,
in the step (1), the resin is selected from one or more of phenolic resin, furfural resin and epoxy resin.
7. The method for producing a solid electrolyte-coated graphite composite material according to claim 5, characterized in that: in the step (2), the preparation conditions for forming the first outer shell layer by using the magnetron sputtering method are as follows: in a closed environment, adjusting the distance between the substrate and the target material to be 5-15cm, and adjusting the included angle between the substrate and the horizontal plane to be 3-10 degrees; vacuumizing the closed environment, and introducing inert gas into the closed environment to serve as sputtering gas; controlling the air pressure of a closed environment to be 0.1-0.5Pa, and carrying out magnetron sputtering by a direct current sputtering source for 30-120min so as to implant the composite material containing the solid electrolyte into the surface layer of the core containing the graphite, wherein the deposition thickness is 100-500 nm;
in the step (2), the temperature of the carbonization treatment is 700-1000 ℃, and the carbonization time is 1-48 h.
8. The method for producing a solid electrolyte-coated graphite composite material according to claim 5, characterized in that: in the step (2), the thickness ratio of the inner core to the first outer shell layer to the second outer shell layer is 100 (5-10) to (1-5).
9. Use of the solid electrolyte-coated graphite composite material according to any one of claims 1 to 4 or the solid electrolyte-coated graphite composite material produced by the production method according to any one of claims 5 to 8 for producing a lithium ion battery.
10. A lithium ion battery, characterized by: the lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode material layer coated on the surface of the negative electrode current collector, the negative electrode material layer comprises a negative electrode material, a conductive agent and a binder, and the negative electrode material adopts the solid electrolyte coated graphite composite material as defined in any one of claims 1 to 4 or the solid electrolyte coated graphite composite material prepared by the preparation method as defined in any one of claims 5 to 8.
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