Recycling Silicon Waste From Photovoltaic Industry To Prepare Anode Materials For Lithium-Ion Batteries

Power batteries have been developing rapidly in recent years,the silicon based anode material has attracted much attention due to its high capacity.At present,the silicon was facing a series of problem which was used in commercialization,such as high cost and difficult preparation.However,the quality of such resources produced in the field of photovoltaic can reach more than 100,000 tons peryear in China.If such resources can be used as a silicon source for preparing silicon based anode materials for lithium ion batteries,which not only reduces the production cost of commercial raw materials silicon,but also solves the problems of excessive accumulation of silicon waste and low added value.Meanwhile,such silicon resources are also face the problem of volume expansion in the process of lithium intercalation when they are used as anode materials for lithium-ion batteries.In order to solve this problem,this paper aims to achieve this goal by varying carbon coating and changing the crystalline form of silicon.At the same time,different material characterization methods and electrochemical performance tests of electrodes were used to analyze the effects of different structures and crystal types on the properties of the composites.The specific research contents of this paper are as follows:(1)Si/ SiOx /C composites were prepared by cutting waste from silicon wafersWaste silicon was the raw material,Firstly,the waste silicon was purified by pickling and roasting in the atmosphere of argon.Then,the micron-sized silicon particles were nanocrystalized by high-energy ball milling.Finally,glucose was used as the carbon source to and the amorphous carbon layer was formed on the surface of the silicon particles by hydrothermal carbonization.Si/SiOx/C composites were obtained due to oxidation during the reaction.In this chapter,the electrochemical properties of purified waste silicon(WS),ball-milling waste silicon(M-WS)and Si/SiOx/C were compared and analyzed.It was found that the Si/SiOx/C composite with amorphous carbon layer and SiOx layer showed the best electrochemical properties,and the Coulomb efficiency was as high as 67.9% for the first time.When the current density is 0.1A/g,the specific discharge capacity is 850 m Ah/g after 100 cycles.(2)Core-shell structure silicon/carbon composites were prepared by cutting waste from silicon wafersTaking nanoscale waste silicon as raw materials,sucrose was used as carbon source in this chapter.The nickel nitrate was added as catalyst in the hydrothermal process,sucrose molecules were induced to grow into core-shell structure with silicon particles as the core and amorphous carbon as the shell.At the same time,the electrochemical properties of silicon,nickel nitrate and sucrose composites with different mass ratios were studied.By comparing the electrochemical properties of the three materials,it can be seen that the composite shows the best performance when the mass ratio of silicon,nickel nitrate and sucrose was 2:1:6.When the current density is0.1A/g,the Coulomb efficiency is 83.6% for the first time,and the discharge specific capacity was maintained at 750 m Ah/g after 450 cycle.The results show that the cycling performance and stability of silicon-based anode can be effectively improved by combining nano silicon and carbon into a core-shell structure.(3)Si-TiC-C composites were prepared by cutting waste from silicon wafersThe silicon,titanium carbide and graphite composites materials were prepared by fractional high energy ball milling with purified silicon waste as raw material,micron metal compound titanium carbide as ball milling medium and graphite as carbon source.In this paper,the electrochemical properties of Si-TiC-C composites at different mass ratios were studied.At the same time,the silicon-carbon materials with the same ball milling conditions were taken as the reference group.It was found that the crystalline silicon particles were successfully transformed into amorphous state after the introduction of the metal compound titanium carbide.In the samples studied,when the mass ratio of silicon,titanium carbide and graphite is 2:4:4,the composite shows the best electrochemical performance.The first coulomb efficiency can reach 62%when the current density is 0.1A/g,the discharge specific capacity was maintained at650 m Ah/g after 50 cycles,and the capacity retention rate is 40%,showing a relatively good cycle stability and excellent rate performance.