Theoretical study of Si (100) doping influence on lithium sorption and diffusion

Currently, silicon is the most promising anode material for a new generation of lithium-ion batteries due to its very high theoretical specific capacity (4200 mAh/g). However, one of the problems hindering the wider use of this material is the slow diffusion of lithium from silicon surface into volume that can be solved by modifying silicon surface. The simulation of surface processes of sorption and diffusion of lithium in doped Si (100) was carried out by using the density functional method. In the study Si (100) doped with single atoms B, Ga, Ge, found that the silicon replacement compared to adsorption are more profitable for all dopants. The binding energy of dopant to silicon decreases from germanium to gallium. It was found that boron atom substitutes for the third layer of silicon, germanium and gallium occupy positions in the first layer. In comparison with the pure material the trend of initial lithium sorption in the channel between silicon dimmers retain for Si (100) doped with single atoms of B, Ga, Ge. Energy barriers of lithium transition on silicon surface substantially reduce (in the case of boron) and increase (in the case of gallium and germanium). The energy barrier of transition from surface to surface layers L-U during the doping increases by 0.05 eV, this shows a moderation of the stage. According to the study, Si (100) doping with boron, gallium and germanium (concentration of 0.3 atomic %) has not significant influence on sorption and diffusion parameters.