Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a composite material for an electrode and a preparation method thereof.
The invention provides a composite material for an electrode, which comprises a vulcanized nickel metal organic framework, wherein tin disulfide is distributed on the vulcanized nickel metal organic framework, and the surface of the composite material has a honeycomb structure.
According to some embodiments of the present invention, the above-mentioned composite material for an electrode has a structure of: banded tin disulfide vertically grows on the flaky nickel sulfide nanosheets.
According to some embodiments of the invention, the sulfided nickel metal organic framework is a platelet structure.
According to some embodiments of the invention, the specific surface area of the sulfided nickel metal organic framework is 40-80 μm2/μm3。
The composite material for the electrode according to the embodiment of the present invention has at least the following technical effects:
compared with a single metal compound, the composite material for the electrode has higher conductivity, wherein a heterojunction exists at the joint of the nickel sulfide and the tin disulfide, so that the transmission path of ions can be shortened, and the reaction kinetics are improved.
The composite material for the electrode has a multi-stage structure, the specific surface area of the material is further improved, the sites of chemical reaction are increased, the surface of the composite material has a honeycomb structure, a space is provided for the desorption of ions, a buffer space is provided for the deformation of a battery in the cycle work, and the service life of the battery is prolonged.
The nickel metal organic frame is of a sheet structure, and the two-dimensional structure is not easy to deform in the charging and discharging process of the battery, can better maintain the capacity retention rate and is not easy to fade.
The second aspect of the present invention provides a method for preparing the above composite material for an electrode, comprising the steps of:
s1: dissolving a nickel source and sodium dodecyl sulfate in water;
s2: slowly adding the solution prepared in the step S1 into a potassium tetracyanide nickelate solution, uniformly stirring, aging and standing to obtain a nickel metal organic framework;
s3: sintering and vulcanizing the nickel metal organic framework in a protective atmosphere to obtain a vulcanized nickel metal organic framework;
s4: and (4) dispersing the vulcanized nickel metal organic framework obtained in the step (S3), uniformly mixing the dispersed nickel metal organic framework with a solution of thioacetamide and stannic chloride pentahydrate, carrying out hydrothermal reaction, and washing and drying a product to obtain the composite material for the electrode.
According to some embodiments of the invention, in step S1, the nickel source is selected from at least one of nickel chloride hexahydrate, nickel nitrate and nickel acetate.
The sodium dodecyl sulfate is used as a dispersing agent, so that the appearance of the material is uniform and uniform, and the material cannot be replaced by other dispersing agents.
In step S2, potassium tetracyanium nickelate provides the final composite metal-organic framework with the contour structure of the organic ligands and metal, which is the main framework of the material.
According to some embodiments of the present invention, the aging and standing time in step S2 is 24 hours.
In the process of preparing the nickel metal organic framework, the ratio of nickel chloride hexahydrate to potassium tetracyanide is 1:1, in the technical scheme of the application, 2mmol of nickel chloride hexahydrate and 9g of sodium dodecyl sulfate are preferably dissolved in 400ml of water and stirred for 30min, too much and too little ratio can prevent the morphology of the material from forming a uniform original sheet-shaped structure, and the structure can provide a large surface area and provide a foundation for subsequent treatment.
According to some embodiments of the invention, in step S3, the sintering is temperature programmed sintering, the temperature rise rate of the temperature programmed sintering is 2-3 ℃/min, the temperature of the temperature programmed sintering is 600 ℃, and the holding time is 2 h.
According to some embodiments of the invention, in step S3, the method of vulcanizing is: and (3) placing the nickel metal organic frame in a lower tuyere of the tubular furnace, placing the sulfur powder in an upper tuyere of the tubular furnace, and vulcanizing the nickel metal organic frame in the sintering process.
Because the boiling point of sulfur is low, in the temperature rising process, if the flow rate of protective gas in the tube is too high, sulfur steam is carried away from a high-temperature area in the furnace without reaction, so that the reaction is insufficient. The nickel metal organic frame is arranged at the lower tuyere of the tubular furnace, and the sulfur powder is arranged at the upper tuyere of the tubular furnace, so that the retention time of sulfur steam can be prolonged, and the reaction is more sufficient.
According to some embodiments of the present invention, in step S4, the temperature of the hydrothermal reaction is 150 to 170 ℃.
According to some embodiments of the invention, in step S4, the hydrothermal reaction time is 8-16 h.
In the preparation method, the nickel metal organic framework is firstly vulcanized so that nickel does not compete with tin for sulfide anions in the subsequent synthesis of tin disulfide, thioacetamide is used as a sulfur source, and the thioacetamide can fully react with tin tetrachloride to synthesize tin dichloride and is fixed on a nickel sulfide nano-chip.
A honeycomb structure is formed on the surface of the nanosheet by the thioacetamide and the stannic chloride through a hydrothermal method, the conductivity of the material is improved by combining the two materials, and meanwhile, a certain structural gap is formed to relieve the deformation of the material.
The conventional commercial material of the lithium ion battery is graphite, and the defects of the conventional commercial material are that the capacity is insufficient, the actual requirement of the power battery is difficult to meet, the stability of a laminated structure is poor, and the laminated structure is easy to collapse after long-time charge-discharge circulation, so that the specific capacity is seriously reduced, and the energy storage life is greatly shortened. The material used in the invention is metal sulfide, the synthesis steps are simple, the raw material source is rich, the price is low, and the theoretical specific capacity is higher.
In addition, compared with a common single metal compound, the conductive material has better conductivity and the capability of relieving the volume deformation of the material, and the service life of the battery is greatly prolonged.
Detailed Description
The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.
Examples
This example prepared a composite material for an electrode comprising the steps of:
s1: dissolving 2mmol of nickel chloride hexahydrate and 9g of sodium dodecyl sulfate in 400ml of water, and stirring for 30min to form clear liquid;
s2: dissolving 2mmol of potassium tetracyanide nickelate in 400ml of water, stirring for 30min, slowly adding the solution prepared in the step S1 into the potassium tetracyanide nickelate solution, uniformly stirring, aging and standing for 24h to obtain a nickel metal organic frame, wherein the synthesized nickel metal organic frame is a sheet structure with the diameter of about 2 mu m as shown in figure 1, the two-dimensional structure is not easy to deform in the charging and discharging process of a battery, can better maintain the capacity retention rate and is not easy to fade, and meanwhile, a large surface area can provide wide reaction sites for subsequent treatment;
s3: putting the nickel metal organic framework and the sulfur powder into a tubular furnace, heating to 600 ℃ in the atmosphere of nitrogen as protective gas at the temperature rise rate of 2 ℃/min, and noting that Ni-MOF and the sulfur powder cannot be mixed in the tubular furnace, the sulfur powder is arranged at an upper air inlet of air inlet, and the Ni-MOF is arranged at a lower air inlet. The obtained product is black powder, namely a nickel sulfide metal organic framework;
s4: ultrasonically dispersing 20mg of the nickel sulfide metal organic framework obtained in the step S3 in 20ml of ethanol to obtain a mixed solution A, simultaneously dissolving 56.3mg of thioacetamide and 105.8mg of tin pentahydrate in 15ml of ethanol to obtain a mixed solution B, stirring the mixed solution A and the mixed solution B for 10min, transferring the mixed solution A and the mixed solution B into a polytetrafluoroethylene lining, covering an outer-layer stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven, heating the stainless steel reaction kettle to 160 ℃ for reaction for 12h, naturally cooling the reaction kettle to room temperature, collecting precipitates by using a centrifugal machine, and washing the precipitates by using pure water and ethanol for a plurality of times to obtain a product. The morphology of the product synthesized through the synthesis steps is shown in fig. 2, and strip-shaped tin disulfide vertically grows on the original flaky nickel sulfide nanosheet. The first sulfuration of Ni-MOF in the synthesis step is to prevent nickel from robbing sulfur anion with tin during the subsequent synthesis of tin disulfide, and thioacetamide as a sulfur source can fully react with tin tetrachloride to synthesize tin dichloride and is fixed on a nickel sulfide nano sheet.
Comparative example 1
In this example, a composite material for an electrode was prepared, and the examples were different in that:
in step S1: the addition amount of the nickel chloride hexahydrate is 2mmol, and the addition amount of the sodium dodecyl sulfate is 5 g;
in step S2: the amount of potassium tetracyanonickelate added was 2 mmol.
The morphology of the prepared product is shown in fig. 3, and as can be seen from fig. 3, part of the product is agglomerated and is difficult to form a uniform round flaky structure.
Comparative example 2
In this example, a composite material for an electrode was prepared, and the examples were different in that:
in step S1: the addition amount of the nickel chloride hexahydrate is 2mmol, and the addition amount of the sodium dodecyl sulfate is 9 g;
in step S2: the amount of potassium tetracyanonickelate added was 5 mmol.
The morphology of the prepared product is shown in fig. 4, and as can be seen from fig. 4, the product has large-area agglomeration and cannot form a uniform round flaky structure.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.