锡硅负极循环过程中体积变化特性研究OA

Currently available commercial graphite-anode materials have low cost,low volume-expansion rate,and good structural stability.However,their theoretical specific capacity(372 mAh/g)is relatively low,which limits the further improvement of their energy density and fails to meet the growing market demand for high-energy-density batteries.Therefore,lithium-alloy anode materials with ultra-high theoretical capacity—such as those using silicon(Si,4200 mAh/g)and tin(Sn,990 mAh/g)as alloy materials—are considered to be highly promising next-generation anode materials.However,the volume expansion of silicon and tin during lithium intercalation and deintercalation leads to electrode pulverization and continuous growth of the solid electrolyte interface film,which seriously affect the battery's cycle life and safety performance.A structural design consisting of silicon nanosheets with tin nanowires grown on their surfaces enables the tin nanowires to form an efficient conducting network within the electrode,which enhances the migration speed of both ions and electrons.Moreover,the highly ductile tin nanowires effectively buffer the volume changes of the silicon nanoparticles during repeated lithium intercalation and deintercalation,thereby effectively suppressing volume expansion.Combining the high capacity of silicon and the high conductivity of tin significantly improves the electrochemical performance of high-capacity alloy anodes.We assembled the silicon-tin composite-anode material(SSA)into a button cell with a high-nickel ternary cathode(LiNi0.9Co0.05Mn0.05O2,NCM90),and the capacity-retention rate still reached 89%after 800 cycles.A 3.5 Ah pouch battery based on this anode technology had an energy density per unit mass of 320 Wh/kg and a volume energy density of 923 Wh/L,with a capacity-retention rate of 91%after 300 cycles.At the same time,the volume expansion of the battery in both the charged and discharged states was controlled effectively,being only 8.13%(charged state)and 3.14%(discharged state)after 200 cycles.This silicon-tin composite-anode technology thus achieves a good balance between high energy density and long cycle life,with excellent volume-change suppression and cycle performance,and it has shown significant potential for practical applications.