Preparation And Performance Study Of Silicon-based Anode Materials For Lithium-ion Batteries

At present,graphite is used as the major anode material for commercial lithium-ion batteries.The specific capacity of most commercial graphite anode material has reached 360-365 m Ah g^-1,while traditional graphite anode materials can hardly meet the requirements of today's new-energy electric vehicles and advanced electronic products.Silicon?Si?is considered as one of the most promising next-generation anode materials for lithium-ion batteries for its advantages in high theoretical capacity(as high as 4200 m Ah g^-1)and more suitable embedded lithium removal platform.Silicon anode material has low inherent conductivity and its volume change could be huge?as high as 300%?during the process of lithium insertion and deinsertion,which can easily lead to the pulverization and peeling of the electrode,affecting the stability of the cycle.In order to solve the problem of the poor cycle stability of silicon anode materials,the author adopted micro-nano silicon powder,porous silicon-silver composite powder,and carbon-silicon-silver composite powder materials,which were made into anode material for lithium-ion battery.The author studied the electrical properties of this anode material.The research steps and finding are summarized below:?1?Research on the technical parameters for preparing micro-nano silicon powder through high-energy ball milling.The author adopted high-energy ball milling method to prepare micro-nano silicon powder and characterize the morphology and particle size of samples in the different all milling process,and looked into how the ratio of grinding media to material and the amount of agent added in the ball milling process affected the grain size and tap density of the silicon powder.It was found that when nano-silicon powder was prepared under the condition where the ratio of grinding media to material was 20:1,and the amount of stearic acid added was1.0wt%,the D₅₀of the nano-silicon powder was 500-600 nm and the tap density was1.27 g cm^-3.?2?Research on the preparation techniques and electrical properties of porous silicon-silver composite powder.The micro-nano silicon powder after ball milling was used as the silicon source,and the porous silicon-silver composite powder was prepared by metal-assisted chemical etching.The structure of sample and pore size under different etching the chemical conditions were studied.The author mainly studied the impact of different etching temperature on the surface area,pore volume,and electrochemical performance of the porous silicon-silver composite powder material.The study found that when the etching temperature was 80?,the prepared porous silicon-silver composite powder material had a more suitable specific surface area and pore volume,which were 20.13 m²g^-1and 7.3×10^-2cm³g^-1,respectively.Under the current density of 0.1 C(1 C=4000 m A g^-1),its initial lithium insertion and deinsertion capacity reached 2511.2 m Ah g^-1and 2973 m Ah g^-1,respectively,with initial Coulomb Efficiency at 86.16%and reversible capacity after 100 cycles at 1226m Ah g^-1,showing good cycle stability compared with anode materials prepared under other temperature conditions.?3?Research on preparation techniques and electrical properties of carbon-silicon-silver composite powder.High-energy ball milling method was adopted to mill 30 wt%porous silicon-silver composite powder and 70 wt%synthetic graphite to prepare carbon-silicon-silver composite powder material,which was then tested to study the microstructure of the composite material and its electrochemical performance when used as anode material of lithium-ion batteries.The research showed that carbon-silicon-silver composite material had a sandwich composite structure and could maintain a specific capacity of 910.5 m Ah g^-1after 100 cycles under the current density of 0.2 C(1 C=1500 m A g^-1)and a specific capacity of 670m Ah g^-1under the current density as high as 2 C.