Optimization Of Preparation Process And Space Regulation Of Positive Electrode For Lithium-sulfur Battery

In the requirements of process equipment and control engineering,we attach great importance to the mastery of chemical process foundation,because the quality of any chemical process will directly or indirectly influence the quality of production results.In recent years,the side reform of energy structure in China has been continuously promoted,and the new energy of environmental protection has gradually replaced the supply of petroleum energy to become a new force in the market.Such as electric vehicles,artificial intelligence robots,wireless network communication base stations and other emerging products to the stage,and the steady operation of these products relies on the power plant is a kind of new energy technology-lithium-ion battery.Through the continuous optimization of battery process,researchers find that the theoretical specific capacity and energy density of lithium-sulfur battery are much higher than those of traditional lithium-ion battery.Therefore,in order to reduce environmental pollution,improve the specific capacity and cycle stability of the battery,obtain more rapid energy conversion,and achieve its portability and cost reduction.In this paper,taking rectorite as the research object,carbon-sulfur composites were prepared for the cathode of lithium-sulfur battery by a heat treatment carbonization process,equal impregnation catalysis process and self-cleaning coating process.In the experiment,the surface morphology and structure of carbon-sulfur composites were studied by XRD,BET,SEM,TG and other methods,and the reasons of electrical conductivity,adsorption and utilization of active materials were discussed.Combined with the electrochemical tests,the effects of the electrochemical performance of the carbon-sulfur composite in the battery charge and discharge process were investigated,and the optimal conditions of different processes were optimized by using the control variable method.The main contents and experimental results of this paper are as follows:(1)Taking pickled rectorite as the research object,the heat treatment carbonization process of sucrose was selected to coat pickled rectorite,and effects of the carbon content,carbonization temperature and carbonization time of carbon coating on the performance of the prepared samples were investigated respectively.Through the phenomenon of surface morphology and microstructure,the thickness,uniformity and integrity of carbon coating under the different process conditions were studied.The electrochemical test data were used to analyze the effects of different process conditions on the electrochemical properties of the materials.The results show that in the process of carbon coating,the process conditions are optimized as follows: when the mass ratio of carbon source to rectorite is 3:1,the carbon coating is complete at 650 ? for 3 h,and then the surface of the sulfur-loaded sample is uniform and doesn't exist accumulation phenomenon.In terms of electrochemical performance,the sample is the best in rate performance,cycling performance,cyclic voltammetry performance and AC impedance.Under the condition of 0.1C rate,the initial discharge specific capacity is 722.7mAh/g and the specific discharge capacity is 361.0mAh/g after 200 laps.From the point of view of spatial regulation,this may be the result of the enhancement of the spatial conduction of electrons and ions in the material.(2)Taking pickled rectorite as the research object,the same amount of transition metal sulphide catalytic process was selected to impregnate the pickled rectorite and then covered with carbon,and the type and proportion of sulfides were investigated in gradient.The compactness,dispersion and adequacy of sulfide loading under different process conditions were studied by means of surface morphology,microstructure and isochronous adsorption.The electrochemical test data were used to analyze the effects of different process conditions on the electrochemical properties of the materials.The results show: under the optimal condition of carbon coating,when a layer of metal sulfide is loaded on the surface of rectorite,the optimal process condition is that the carbon coating effect is the best after loading cobalt sulfide,and the adsorption effect on lithium polysulfide is the strongest,the carbon coating is complete,and the sulfur loading is uniform.Under the condition of 0.1C rate,the initial stable discharge specific capacity of the composite sample loaded with 0.004M/g of cobalt sulphide is 834.8 mAh/g.After 200 charge-discharge cycles,it still retains the discharge specific capacity of 373.4mAh/g.From the point of view of spatial regulation,this may be the result of the enhanced effect of matter inside the material on spatial anchoring.(3)Taking the carbon rectorite coated with cobalt sulfide as the research object,the self-cleaning coating process of aluminum fluoride was selected to cover the whole object,and the proportion of sulfur and dosage of aluminum fluoride were investigated respectively.The thickness,uniformity and integrity of aluminum fluoride coating under different process conditions were studied by means of surface morphology and microstructure.The results show that when the coating process is optimized as 0.003M/g ratio of aluminum fluoride and 60%wt of sulfur content,the coating of aluminum fluoride on the research object is the most complete,and the sulfur load reaches the ultimate capacity.Under the condition of 0.1C ratio,the initial stable specific capacity of the composite is 1228.2mAh/g,and the discharge specific capacity is 461.0mAh/g after 200 cycles,and the Coulomb efficiency is maintained at more than 95% during the whole cycles.From the point of view of spatial regulation,this may be the result of the enhancement of space utilization efficiency by the matter inside the material.