Preparation Of Micron Silicon Anode Material And Research On Its Carbon Coating Modification

Silicon materials have attracted much attention due to its excellent performance.However,there is a significant volume effect during the charging and discharging process,which can make the conductive network broken and electrode failure.Moreover,as a semiconductor,silicon has low conductivity.Therefore,it is generally considered to use nano silicon with better performance for industrial application currently,but the high cost of nano silicon is not easily accepted by the vast energy storage market.In order to overcome the shortcomings of silicon materials and developing lithium-ion battery anode material with low-cost and excellent performance,we using industrial micro-silicon as raw materials and modified it in the same time,the main results are as follows:（1）After acid pickling in hydrochloric acid and hydrofluoric acid mixture,impurities and oxide layer on silicon powder were removed,and micron silicon powder with excellent crystalline properties and low cost was prepared,and its discharge specific capacity in the first cycle is 3281 mA g^-1.The discharge capacity of graphite-silicon anode material can be significantly increased by 5%silicon doping,increases from 355.3 mA g^-1 to 551.2 mA g^-1 with an increase of more than55.1%.According to the proportional relationship,the specific capacity of industrial silicon powder after acid pickling can be calculated as high as 4200 mA g^-1.（2）After using asphalt as the carbon source to modify the micron silicon powder obtained after acid pickling,it is found that with the increase of the asphalt content,the first charge specific capacity of the composite material is slightly reduced,but the cycle stability is obviously improved,and the material properties gradually increase with the increase of carbonization temperature before 900°C.Material carbonized at 800°C with 20%asphalt showed the best electrochemical performance,the charge specific capacity still maintain at 1157.8 mAh g^-1 with a cycle retention rate of 49.1%after 10 cycles,while pure silicon has lost its lithium storage capacity in the fifth cycle.（3）The glucose-modified silicon-carbon material was characterized by adding90%graphite as active material,the results show that discharge specific capacity of the silicon-carbon composite obtained by adding 5%glucose was 690.1 mAh g^-1 in the first cycle.According to the proportional relationship,the modified micron silicon powder has a specific capacity of 3703.3 mAh g^-1,and the capacity is still higher than 3332 mAh g^-1 after 10 cycles.