Preparation Of Silicon-Carbon Composite Anode Material And Research On Full Cell Technology

In the past few decades,the market of electrochemical energy storage equipment has grown rapidly in the field of portable electronic equipment.There is widespread interest in developing high energy density lithium-ion batteries to meet electricity demand.Silicon-carbon composite materials have high capacity and excellent cycling performance.It is expected to be one of the most promising anode materials for the next generation of lithium-ion batteries.In this paper,commercial micron and nano silicon powder are used as silicon sources to prepare micron silicon-carbon composites and nano silicon-carbon composites respectively.The effects of different kinds of electrolyte,conductive agent,and binder on the electrochemical properties of these two composites were studied.(1)Micron-sized Silicon/graphite(Si/G)composites were prepared with commercial micron-sized silicon powder and graphite as raw materials by simple mixing with V-type mixer.The effects of different mixing time on the properties of the composites were studied.The results showed that when the mixing time was 1 h,the composite was uniformly mixed,the morphology of the composite did not change,and showed excellent cycle performance.The capacity retention rate was92.94% after 50 cycles.The battery process system of the material was further studied.The results show that the matching degree between Tianci electrolyte and this material is higher.After 100 cycles,the capacity retention rate is 82.65%;When using the water-based adhesive NV-1T produced by Zhejiang Zhongke Lide,the pole piece has higher peel strength,smaller rebound rate and swelling degree,and the structural stability of the pole piece is better during charging and discharging.The assembled battery has the best cycle performance and rate performance.After 100 cycles,the capacity retention rate is 85.69%;When single-walled carbon nanotubes(SWCNT)and conductive carbon black(SP)were added together,the cycle performance of the battery was significantly improved.This is because SWCNT has a high aspect ratio and forms a stable conductive network with spherical SP,which improves the structural stability of the electrode and thus improves the cycle performance of the material.(2)Silicon/graphite/carbon nanotubes/pyrolytic carbon composites(Si/G/CNT/C)were prepared using commercial nano-silicon powder,graphite,asphalt,and carbon nanotubes(CNT)as raw materials by two mixing methods of high-efficiency vibration fusion coating machine(VSH)+ high-efficiency mixing modification machine(VCH)and high temperature pyrolysis,and the battery process system of the composites was studied.The results show that the matching degree between Tianci electrolyte and the material is higher.After 100 cycles,the capacity retention rate is 83.61%;When using the water-based binder BA-290 S produced by Fujian Lanhai Blackstone,the battery cycle performance is the best.After 100 cycles,the capacity retention rate is 86.69%;Adding SWCNT or conductive graphite(KS-6)can improve the cycle performance and high current charge-discharge performance of the battery.When linear SWCNT is used together with nano-scale SP,it is easy to form a stable conductive network,which can relieve the volume expansion of silicon and improve the electrochemical performance of the material.Therefore,when0.03%SWCNT is added to interact with 1.87%SP,the capacity retention rate is88.62% after 100 cycles.When 0.7%KS-6 and 1.2%SP are added together,after 100 cycles,the capacity retention rate is 85.01%,which is because the large-size KS-6fills the larger void in the composite material and the small-size SP fills the smaller void,making the contact between particles closer and improving the stability of the electrode.