CN110707290B - Preparation method of flexible lithium ion battery negative electrode with sandwich-like structure - Google Patents

Preparation method of flexible lithium ion battery negative electrode with sandwich-like structure Download PDF

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CN110707290B
CN110707290B CN201910991317.9A CN201910991317A CN110707290B CN 110707290 B CN110707290 B CN 110707290B CN 201910991317 A CN201910991317 A CN 201910991317A CN 110707290 B CN110707290 B CN 110707290B
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dispersion liquid
weight
parts
suction filtration
lithium ion
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CN110707290A (en
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杨书廷
张芬丽
郑延辉
董红玉
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Battery Research Institute Of Henan Co ltd
Henan Normal University
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Henan Normal University
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0433—Molding
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses a preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure, belonging to the technical field of preparation of the lithium ion battery cathode electrode. The preparation process is simple and easy to implement, the prepared flexible lithium ion battery cathode electrode has excellent cycle performance, and the energy density of the lithium ion battery can be improved to a certain extent.

Description

Preparation method of flexible lithium ion battery negative electrode with sandwich-like structure
Technical Field
The invention belongs to the technical field of preparation of negative electrodes of lithium ion batteries, and particularly relates to a preparation method of a flexible negative electrode of a lithium ion battery with a sandwich-like structure.
Background
The lithium ion battery has the advantages of high voltage, large energy density, long cycle life, environmental friendliness and the like, and is widely applied to the fields of portable electronic products, new energy automobiles and the like. Meanwhile, people also put forward higher and higher requirements on the energy density of the lithium ion battery, and the theoretical capacity of the graphite is only 372mAh/g and cannot meet the requirements of the power battery. Tin dioxide (SnO) 2 ) Because the specific capacity is high (782 mAh/g), the lithium storage potential (about 0.5V) is safe, nontoxic and easy to obtain, theoretically, the lithium ion battery can meet the requirements of high energy density and safety of a power lithium ion battery, receives extensive attention of researchers, and becomes a popular material in the research field of lithium ion battery cathode materials. However, tin dioxide as an electrode material expands in volume during charging and discharging, causing electrode pulverization, resulting in separation of active materials from a current collector, thereby causing rapid capacity degradation of the electrode material. Compounding tin dioxide with other materials, such as carbon materials, can buffer capacity fade during cycling.
In addition, the conventional preparation method of the lithium ion battery cathode electrode is completed through the working procedures of material preparation, coating and the like: mixing the negative electrode material, the conductive agent and the binder to prepare slurry, and then uniformly coating the slurry on the current collector. The current collector is needed in the process, and the energy density of the battery is reduced to a certain extent due to the existence of the current collector. Therefore, reducing or avoiding the use of current collectors is an effective way to increase the energy density of lithium ion batteries.
Disclosure of Invention
The invention provides a preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure, which is simple and easy in process and aims at overcoming the defects of the prior art 2 The problem of volume expansion during the circulation process is solved, thereby improving SnO 2 In addition, a current collector is not needed in the preparation process of the flexible lithium ion battery cathode electrode, so that the cycle performance is improved to a certain extentEnergy density of lithium ion batteries.
The invention adopts the following technical scheme for solving the technical problems:
a preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 10-25 parts by weight of graphene and 10-25 parts by weight of carbon nanotubes in water, ultrasonically dispersing for 0.5-3h, and mechanically stirring for 1-5h to obtain uniform dispersion liquid A;
step S2: dissolving 8-64 parts by weight of stannous chloride/stannic chloride in water, adding 8-64 parts by weight of carbon material, mechanically stirring for 0.5-5h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH of the mixed system to 2-10, and mechanically stirring for 1-5h to obtain a dispersion liquid B, wherein the carbon material is one or more of graphite, soft carbon or hard carbon;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake in vacuum at 60 ℃, and treating for 2-8h at 200 ℃ in an air atmosphere to obtain a tin oxide/carbon material compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.1-10%, wherein the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, polyacrylic acid or sodium alginate;
step S5: adding the tin oxide/carbon material composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 1-10 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (2) removing the filter cake obtained after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with a sandwich-like structure, wherein the thickness of the flexible lithium ion battery cathode electrode is 10-70 mu m, the upper layer and the lower layer are flexible supporting layers, the components of the flexible lithium ion battery cathode electrode are graphene and carbon nano tubes, the middle layer is a tin oxide/carbon material compound, the tin oxide is nano particles with the particle size of 10-200nm, the nano particles are uniformly distributed on the surface of the carbon material, the tin oxide/carbon material compound is uniformly dispersed in a network structure formed by the graphene and the carbon nano tubes, the graphene and the carbon nano tubes play a role of a conductive bridge and also provide the supporting layer for the tin oxide/carbon material compound, and in addition, the flexible structure relieves the volume expansion in the tin oxide circulation process.
Further preferably, the solvent in the binder solution in step S4 is water or N-methylpyrrolidone.
A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 20 parts by weight of graphene and 20 parts by weight of carbon nanotubes in water, ultrasonically dispersing for 1 hour, and mechanically stirring for 2 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of stannous chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 1h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 6, and mechanically stirring for 2h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 4h in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of binder solution with the mass fraction of 3%, wherein the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/graphite composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 3 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 569.3mAh/g, the first charging and discharging efficiency is tested to be 79.4%, the 100-cycle reversible specific capacity is 504.7mAh/g, and the 100-cycle capacity retention rate is 88.7%.
A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 10 parts by weight of graphene and 10 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 0.5h, and then mechanically stirring for 1h to obtain a uniform dispersion liquid A;
step S2: dissolving 32 parts by weight of stannous chloride in water, adding 64 parts by weight of hard carbon, mechanically stirring for 0.5h in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to be 2, and mechanically stirring for 1h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake in vacuum at 60 ℃, and treating for 2h at 200 ℃ in an air atmosphere to obtain a tin oxide/hard carbon compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.1%, wherein the binder is polytetrafluoroethylene, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/hard carbon composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 1 hour to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 658.7mAh/g, the first charging and discharging efficiency is tested to be 79.3%, the 100-cycle reversible specific capacity is 563.8mAh/g, and the 100-cycle capacity retention rate is 85.6%.
A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 25 parts by weight of graphene and 25 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 3 hours, and then mechanically stirring for 5 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 64 parts by weight of tin chloride in water, adding 8-parts by weight of soft carbon, mechanically stirring for 5 hours in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of a mixed system to 10, and mechanically stirring for 5 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 8h in an air atmosphere to obtain a tin oxide/soft carbon compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 5%, wherein the binder is sodium carboxymethylcellulose, and the solvent is water;
step S5: adding the tin oxide/soft carbon composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 10 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 702.3mAh/g, the first charging and discharging efficiency is tested to be 75.5%, the 100-cycle reversible specific capacity is 583.6mAh/g, and the 100-cycle capacity retention rate is 83.1%.
A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 25 parts by weight of graphene and 15 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 2 hours, and then mechanically stirring for 3 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of tin chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 5 hours in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 10%, wherein the binder is sodium carboxymethylcellulose, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 526.4mAh/g, the first charging and discharging efficiency is tested to be 80.6%, the 100-cycle reversible specific capacity is 462.7mAh/g, and the 100-cycle capacity retention ratio is 87.9%.
A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 20 parts by weight of graphene and 20 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 2 hours, and then mechanically stirring for 3 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of tin chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 5 hours in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.3%, wherein the binder is sodium alginate, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the assembled button battery is assembled into a button battery, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is 551.5mAh/g, the first reversible specific capacity of the battery is 78.9 percent, the 100-cycle reversible specific capacity of the battery is 476.5mAh/g, and the 100-cycle capacity retention rate is 86.4 percent.
The flexible lithium ion battery cathode electrode prepared by the invention has a sandwich-like structure, the thickness is 10-70 mu m, the upper layer and the lower layer are flexible supporting layers, the components are graphene and carbon nano tubes, and the middle layer is a tin oxide/carbon material compound. The graphene and the carbon nanotubes not only play a role of a conductive bridge, but also provide a support layer for the tin oxide/carbon material composite, and in addition, the flexible structure relieves the volume expansion in the tin oxide circulation process. The preparation process is simple and easy to implement, the prepared flexible lithium ion battery negative electrode has excellent cycle performance, and the energy density of the lithium ion battery can be improved to a certain extent.
Drawings
FIG. 1 is an SEM image of a tin oxide/graphite composite prepared in example 1;
fig. 2 is an SEM image of the flexible lithium ion battery negative electrode prepared in example 1;
FIG. 3 is a graph of the cycle performance of the negative electrode of the flexible lithium ion battery prepared in example 1;
fig. 4 is a graph of cycle performance of the tin oxide/graphite composite prepared in comparative example 1.
Detailed Description
The present invention is described in further detail below with reference to examples, but it should not be construed that the scope of the above subject matter of the present invention is limited to the following examples, and that all the technologies realized based on the above subject matter of the present invention belong to the scope of the present invention.
Example 1
Step S1: uniformly dispersing 20g of graphene and 20g of carbon nanotubes in water, ultrasonically dispersing for 1h, and mechanically stirring for 2h to obtain a uniform dispersion liquid A;
step S2: dissolving 10g of stannous chloride in water, adding 40g of graphite, mechanically stirring for 1h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 6, and mechanically stirring for 2h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 4h in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100g of binder solution with the mass fraction of 3%, wherein the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/graphite compound obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 3 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (5) removing the filter cake subjected to suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery negative electrode with the sandwich-like structure.
Fig. 1 is an SEM picture of the tin oxide/graphite composite obtained in step S3 of this example, and it can be seen that tin oxide is nanoparticles with a particle size of 10-200nm, most of the tin oxide is uniformly attached to the graphite surface, and a small amount of the tin oxide exists in the form of tin oxide particles.
The flexible lithium ion battery cathode electrode prepared by the embodiment has a sandwich-like structure, the thickness is 10-70 μm, the upper layer and the lower layer are flexible supporting layers, the components are graphene and carbon nano tubes, the middle layer is a tin oxide/graphite compound, and tin oxide is nano particles with the particle size of 10-200nm and is uniformly distributed on the surface of graphite. The tin oxide/graphite composite is uniformly dispersed in the network structure formed by the graphene and the carbon nanotubes. Graphene and carbon nanotubes not only play a role of a conductive bridge, but also provide a support layer for the tin oxide/graphite composite, and in addition, the flexible structure of the composite can buffer the volume expansion of tin oxide in the circulating process. The existence of the binder not only enables the tin oxide/graphite compound and the tin oxide/graphite compound, graphene and carbon nano tubes to be tightly bonded together, but also enables the layers in the sandwich-like structure to be combined more firmly.
Fig. 2 is an SEM picture of the flexible lithium ion battery negative electrode prepared in this example, and it can be seen that the tin oxide/graphite composite is uniformly dispersed in the network structure formed by the graphene and the carbon nanotubes.
Example 2
Step S1: uniformly dispersing 10g of graphene and 10g of carbon nanotubes in water, ultrasonically dispersing for 0.5h, and mechanically stirring for 1h to obtain a uniform dispersion liquid A;
step S2: dissolving 32g of stannous chloride in water, adding 64g of hard carbon, mechanically stirring for 0.5h in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 2, and mechanically stirring for 1h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake in vacuum at 60 ℃, and then treating for 2 hours at 200 ℃ in an air atmosphere to obtain a tin oxide/hard carbon compound;
step S4: 100g of binder solution with the mass fraction of 0.1% is prepared, wherein the binder is polytetrafluoroethylene, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/hard carbon composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 1 hour to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (5) removing the filter cake subjected to suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery negative electrode with the sandwich-like structure.
Example 3
Step S1: uniformly dispersing 25g of graphene and 25g of carbon nanotubes in water, ultrasonically dispersing for 3 hours, and mechanically stirring for 5 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 64g of stannic chloride in water, adding 8g of soft carbon, mechanically stirring for 5 hours in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 10, and mechanically stirring for 5 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 8h in an air atmosphere to obtain a tin oxide/soft carbon compound;
step S4: 100g of a binder solution with the mass fraction of 5% is prepared, wherein the binder is sodium carboxymethyl cellulose, and the solvent is water;
step S5: adding the tin oxide/soft carbon composite obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 10 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (5) removing the filter cake subjected to suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery negative electrode with the sandwich-like structure.
Example 4
Step S1: uniformly dispersing 25g of graphene and 15g of carbon nanotubes in water, ultrasonically dispersing for 2h, and mechanically stirring for 3h to obtain a uniform dispersion liquid A;
step S2: dissolving 10g of tin chloride in water, adding 40g of graphite, mechanically stirring for 5 hours in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of a mixed system to be 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100g of a binder solution with the mass fraction of 10%, wherein the binder is sodium carboxymethylcellulose, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (5) removing the filter cake subjected to suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery negative electrode with the sandwich-like structure.
Example 5
Step S1: uniformly dispersing 20g of graphene and 20g of carbon nanotubes in water, performing ultrasonic dispersion for 2 hours, and mechanically stirring for 3 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10g of tin chloride in water, adding 40g of graphite, mechanically stirring for 5 hours in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of a mixed system to be 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100g of a binder solution with the mass fraction of 0.3%, wherein the binder is sodium alginate, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (5) removing the filter cake subjected to suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery negative electrode with the sandwich-like structure.
Comparative example 1
Dissolving 10g of stannous chloride in water, adding 40g of graphite, mechanically stirring for 1h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 6, and mechanically stirring for 2h to obtain a dispersion liquid; and (3) carrying out suction filtration on the dispersion liquid by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 4 hours at 200 ℃ in an air atmosphere to obtain the tin oxide/graphite compound.
TABLE 1
Examples First reversible specific capacity (mAh/g) First charge-discharge efficiency (%) 100 weeks reversible specific capacity (mAh/g) Capacity retention ratio at 100 weeks (%)
Example 1 569.3 79.4 504.7 88.7
Example 2 658.7 79.3 563.8 85.6
Example 3 702.3 75.5 583.6 83.1
Example 4 526.4 80.6 462.7 87.9
Example 5 551.5 78.9 476.5 86.4
Comparative example 1 492.8 88.8 340.7 69.1
The flexible lithium ion battery negative electrode prepared in examples 1 to 5 was cut into a circular piece having a diameter of 12mm, and the battery was assembled. The battery assembly is carried out in a glove box, and a button battery is assembled by taking a metal lithium sheet as a counter electrode, a polypropylene film as a diaphragm and 1M lithium hexafluorophosphate (a solvent is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1: 1) as an electrolyte. And charging and discharging the assembled button cell at 0.1 ℃ within the voltage range of 0.05V-2V. The first reversible specific capacity (mAh/g), the first charge-discharge efficiency (%), the 100-week reversible specific capacity (mAh/g) and the 100-week capacity retention rate (%) of the battery were tested, and the results are shown in Table 1.
And uniformly mixing and grinding the tin oxide/graphite composite prepared in the comparative example 1, acetylene black and polyvinylidene fluoride according to the mass ratio of 8:1:1 for 30min, uniformly coating the mixture on a copper foil, drying the copper foil, cutting the copper foil into a wafer with the diameter of 12mm, and assembling the battery. The cell is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, and 1M lithium hexafluorophosphate (the solvent is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1: 1) is used as an electrolyte to assemble the button cell. And charging and discharging the assembled button cell at 0.1 ℃ within the voltage range of 0.05V-2V. The first reversible specific capacity (mAh/g), the first charge-discharge efficiency (%), the 100-week reversible specific capacity (mAh/g) and the 100-week capacity retention rate (%) of the battery were tested, and the results are shown in Table 1.
As can be seen from the examples, by adjusting the ratio of the tin oxide/stannous oxide to the carbon material (graphite, hard carbon, soft carbon) in step S2, and the mass of the graphene and the carbon nanotube and the ratio of the tin oxide/stannous oxide to the carbon material, the negative electrode of the lithium ion battery with different specific capacities can be obtained. Compared with a simple tin oxide and carbon material composite (a comparative example), the flexible lithium ion battery cathode electrode with the sandwich-like structure has higher specific capacity and more excellent cycle performance.
The foregoing embodiments illustrate the principles, principal features and advantages of the invention, and it will be understood by those skilled in the art that the invention is not limited to the foregoing embodiments, which are merely illustrative of the principles of the invention, and that various changes and modifications may be made therein without departing from the scope of the principles of the invention.

Claims (7)

1. A preparation method of a flexible lithium ion battery cathode electrode with a sandwich-like structure is characterized by comprising the following specific steps:
step S1: uniformly dispersing 10-25 parts by weight of graphene and 10-25 parts by weight of carbon nanotubes in water, ultrasonically dispersing for 0.5-3h, and mechanically stirring for 1-5h to obtain uniform dispersion liquid A;
step S2: dissolving 8-64 parts by weight of stannous chloride or stannic chloride in water, adding 8-64 parts by weight of carbon material, mechanically stirring for 0.5-5h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH of the mixed system to 2-10, and mechanically stirring for 1-5h to obtain a dispersion liquid B, wherein the carbon material is one or more of graphite, soft carbon or hard carbon;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake in vacuum at 60 ℃, and treating for 2-8h at 200 ℃ in an air atmosphere to obtain a tin oxide/carbon material compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.1-10%, wherein the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, polyacrylic acid or sodium alginate;
step S5: adding the tin oxide/carbon material composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 1-10 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: and (2) removing the filter cake obtained after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with a sandwich-like structure, wherein the thickness of the flexible lithium ion battery cathode electrode is 10-70 mu m, the upper layer and the lower layer are flexible supporting layers, the components of the flexible lithium ion battery cathode electrode are graphene and carbon nano tubes, the middle layer is a tin oxide/carbon material compound, the tin oxide is nano particles with the particle size of 10-200nm, the nano particles are uniformly distributed on the surface of the carbon material, the tin oxide/carbon material compound is uniformly dispersed in a network structure formed by the graphene and the carbon nano tubes, the graphene and the carbon nano tubes play a role of a conductive bridge and also provide the supporting layer for the tin oxide/carbon material compound, and in addition, the flexible structure relieves the volume expansion in the tin oxide circulation process.
2. The preparation method of the flexible lithium ion battery negative electrode with the sandwich-like structure according to claim 1, characterized in that: the solvent in the binder solution in step S4 is water or N-methylpyrrolidone.
3. The preparation method of the negative electrode of the flexible lithium ion battery with the sandwich-like structure according to claim 1, which is characterized by comprising the following specific steps of:
step S1: uniformly dispersing 20 parts by weight of graphene and 20 parts by weight of carbon nanotubes in water, ultrasonically dispersing for 1 hour, and mechanically stirring for 2 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of stannous chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 1h in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 6, and mechanically stirring for 2h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 4h in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of binder solution with the mass fraction of 3%, wherein the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/graphite compound obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 3 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: taking off the filter cake obtained after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the sandwich-like structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 569.3mAh/g, the first charging and discharging efficiency is tested to be 79.4%, the 100-cycle reversible specific capacity is 504.7mAh/g, and the 100-cycle capacity retention rate is 88.7%.
4. The preparation method of the flexible lithium ion battery cathode electrode with the sandwich-like structure according to claim 1, which is characterized by comprising the following specific steps:
step S1: uniformly dispersing 10 parts by weight of graphene and 10 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 0.5h, and then mechanically stirring for 1h to obtain a uniform dispersion liquid A;
step S2: dissolving 32 parts by weight of stannous chloride in water, adding 64 parts by weight of hard carbon, mechanically stirring for 0.5h in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to be 2, and mechanically stirring for 1h to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake in vacuum at 60 ℃, and treating for 2h at 200 ℃ in an air atmosphere to obtain a tin oxide/hard carbon compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.1%, wherein the binder is polytetrafluoroethylene, and the solvent is N-methylpyrrolidone;
step S5: adding the tin oxide/hard carbon composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 1 hour to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 658.7mAh/g, the first charging and discharging efficiency is tested to be 79.3%, the 100-cycle reversible specific capacity is 563.8mAh/g, and the 100-cycle capacity retention rate is 85.6%.
5. The preparation method of the flexible lithium ion battery cathode electrode with the sandwich-like structure according to claim 1, which is characterized by comprising the following specific steps:
step S1: uniformly dispersing 25 parts by weight of graphene and 25 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 3 hours, and then mechanically stirring for 5 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 64 parts by weight of tin chloride in water, adding 8-parts by weight of soft carbon, mechanically stirring for 5 hours in a water bath at the temperature of 80 ℃, dropwise adding ammonia water to adjust the pH value of a mixed system to 10, and mechanically stirring for 5 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating at 200 ℃ for 8h in an air atmosphere to obtain a tin oxide/soft carbon compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 5%, wherein the binder is sodium carboxymethylcellulose, and the solvent is water;
step S5: adding the tin oxide/soft carbon composite obtained in the step S3 into the binder solution obtained in the step S4, and mechanically stirring for 10 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 702.3mAh/g, the first charging and discharging efficiency is tested to be 75.5%, the 100-cycle reversible specific capacity is 583.6mAh/g, and the 100-cycle capacity retention rate is 83.1%.
6. The preparation method of the flexible lithium ion battery cathode electrode with the sandwich-like structure according to claim 1, which is characterized by comprising the following specific steps:
step S1: uniformly dispersing 25 parts by weight of graphene and 15 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 2 hours, and then mechanically stirring for 3 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of tin chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 5 hours in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 10%, wherein the binder is sodium carboxymethylcellulose, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the button battery is assembled, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is tested to be 526.4mAh/g, the first charging and discharging efficiency is tested to be 80.6%, the 100-cycle reversible specific capacity is 462.7mAh/g, and the 100-cycle capacity retention ratio is 87.9%.
7. The preparation method of the flexible lithium ion battery cathode electrode with the sandwich-like structure according to claim 1, which is characterized by comprising the following specific steps:
step S1: uniformly dispersing 20 parts by weight of graphene and 20 parts by weight of carbon nanotubes in water, performing ultrasonic dispersion for 2 hours, and then mechanically stirring for 3 hours to obtain a uniform dispersion liquid A;
step S2: dissolving 10 parts by weight of tin chloride in water, adding 40 parts by weight of graphite, mechanically stirring for 5 hours in a water bath at 80 ℃, dropwise adding ammonia water to adjust the pH value of the mixed system to 8, and mechanically stirring for 2 hours to obtain a dispersion liquid B;
step S3: carrying out suction filtration on the dispersion liquid B obtained in the step S2 by using a sand core funnel, drying a filter cake at 60 ℃ in vacuum, and treating for 6h at 200 ℃ in an air atmosphere to obtain a tin oxide/graphite compound;
step S4: preparing 100 parts by weight of a binder solution with the mass fraction of 0.3%, wherein the binder is sodium alginate, and the solvent is water;
step S5: adding the tin oxide/graphite compound obtained in the step (3) into the binder solution obtained in the step (S4), and mechanically stirring for 5 hours to obtain a uniform dispersion liquid C;
step S6: pouring the dispersion liquid A obtained in the step S1 of 1/2 into a sand core funnel for suction filtration, adding the dispersion liquid C obtained in the step S5 when the dispersion liquid A is quickly dried by pumping, adding the dispersion liquid A obtained in the step S1 of 1/2 when the dispersion liquid A is quickly dried by pumping, and stopping suction filtration when the dispersion liquid A is quickly dried by pumping;
step S7: removing the filter cake after the suction filtration in the step S6 from the filter paper, and freeze-drying in a freeze-drying box to obtain the flexible lithium ion battery cathode electrode with the similar sandwich structure;
the prepared negative electrode of the flexible lithium ion battery is cut into a wafer with the diameter of 12mm to assemble the battery, the battery is assembled in a glove box, a metal lithium sheet is used as a counter electrode, a polypropylene film is used as a diaphragm, 1M lithium hexafluorophosphate is used as electrolyte, a solvent in the electrolyte is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1, the assembled button battery is assembled into a button battery, the assembled button battery is charged and discharged within the voltage range of 0.05V-2V at 0.1C, the first reversible specific capacity of the battery is 551.5mAh/g, the first reversible specific capacity of the battery is 78.9 percent, the 100-cycle reversible specific capacity of the battery is 476.5mAh/g, and the 100-cycle capacity retention rate is 86.4 percent.
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