A first-principles study on Si as an anode material for rechargeable batteries.

Due to its intriguing geometry, possessing an open-channel structure, Si demonstrates potential for storing and/or transporting Li/Na ions in rechargeable batteries. In this work, first-principles calculations were employed to investigate the phase stability and Li/Na storage and transport properties of the Si anode to evaluate its electrochemical performance for batteries. The intercalation of Li and Na into the Si structure could deliver a capacity of 159 mA h g (LiSi and NaSi), and the average intercalation potentials were 0.17 V ( Li) and 0.34 V ( Na). Moreover, the volume change of Si upon intercalation proved very small (0.09% for Li, 2.81% for Na), indicating its "zero-strain" properties with stable cycling performance. Li and Na can diffuse along the channels inside the Si structure with barrier energies of 0.14 and 0.80 eV respectively, and the ionic conductivity of LiSi was calculated to be as high as 1.03 × 10 S cm at 300 K. Our calculations indicate that the fast Li-ionic conductivity properties make the Si structure a novel anode material for both lithium and sodium ion batteries.