First-principles Study On Interstitial Solid Solution Model Of Lithiation Properties Of Cosn Alloy Anode Material For Lithium Ion Battery

Based on the density functional theory of first-principle, an ab initio pseudopotentialplane-wave method was used to calculate the structures, electronic properties, volumeexpansion, average intercalation voltage, insertion formation energy, and theoreticalcapacity of Li_xCo₃Sn₃（x=0,1,2,3,4,6,8,12） alloy as anode material for lithium ion batteryare investigated in the present work. The results show that in the crystal cell of CoSnalloy, the effect between Co-Sn bonds is poorly covalent hybrid and Co-Co arecombined to form ionic bonds, respectively. With the increase of the number of theinserted lithium-ion,alloy system comes out ion characteristics and conductivitygradually, Li atomics bond successively with Sn and Co atoms.But the insertedlithium-ions cause significant changes on electronic structure of LiCo₃Sn₃.However, alarge formation energy and expansion ration for Li_xCo₃Sn₃（8≤x≤12） are found as aconsequence of lithium content increasing, which lead to the bad cycle stability forCoSn alloy as the Li-ion battery electrode material.The ideal tin cobalt electrodesrequires a high content of LiCoSn phase and a relatively small content of Li₂CoSn phaseto solve contradictory relationship of the balance volume expansion and capacity fading.