Preparation Of Silicon Alloy Anode For Lithium-Ion Battery And Its Lithium-Storage Performance

Due to its high theoretical capacity,suitable lithiation voltage,low cost and environmental friendliness,silicon has been considered as the most promising anode material for the next-generational high-energy-density lithium-ion battery.In spite all of the features,the large volume change during lithiation and low intrinsic conductivity make silicon hard to commercialize in the future.In view of the above problems,this paper mainly aims to improve the cyclability and rate performance of silicon anode by in situ introducing alloy phase and carbon-based surface modification materials.High energy ball milling was used to prepare Si/Cu composites,and the effects of Cu and graphite addition on the lithiation mechanism and cyclability of the final Si/Cu composite were systematically studied.The experimental results showed that the introduction of Cu could effectively promote the formation of Cu₃Si alloy phase and alleviate the volume expansion of silicon in the lithiation process,while graphite coating layer could effectively stable the interface state of the material,promoting the composite to form robust SEI film during the first discharge.Finally,the material（SCG50-30）prepared by adding 50 at%Cu and 30 wt%graphite performed excellent electrochemical properties with a reversible capacity of 460.8 m Ah g^-1 after 100 cycles and capacity retention of 62.1%.Si/Fe-based composites were prepared by high energy ball milling.The effects of additional Fe and SWCNT content as well as heat treatment temperature on the lithiation mechanism of silicon were studied.Results showed that adding Fe could effectively reduce the lithiation voltage.Combining Si/Fe with SWCNT could effectively improve the electrochemical performance.Finally,the Si/Fe/SWCNT/C composite prepared by introducing 30 at%Fe and 5 wt%SWCNT by holding at 300℃for 3 hours exhibited excellent electrochemical properties.Specifically,the initial coulombic efficiency of the composite reached 78.1%.After 100 cycles,the reversible charge specific capacity was 636.4 m Ah g^-1,and capacity retention was 75.4%.Even at high current density of 4.0 A g^-1,the reversible capacity of Si/Fe/SWCNT/C could reach 398.8 m Ah g^-1.