Crystal Structure and Electrical/thermal Transport Properties of Li1-xSn2+xP2 and Its Performance as a Li-Ion Battery Anode Material

A new ternary layered pnictide, Li 1-x Sn 2+x P 2 , was synthesized by a solid-state reaction and its properties were examined to explore its potential as a multifunctional material. The compound crystallizes in a layered structure in the R-3m space group with buckled honeycomb Sn-P layers separated by mixed-occupation Li/Sn layers. Crystal structure analysis using synchrotron X-ray diffraction showed that the substitution degree of Li by Sn (x) is approximately 0.3. Local ordering of Li/Sn occupation was demonstrated using 31 P nuclear magnetic resonance analysis. The lattice thermal conductivity of Li 1-x Sn 2+x P 2 was found to be relatively low (1.2 Wm −1 K −1 at 525 K). The room-temperature electrical resistivity of Li 1-x Sn 2+x P 2 was found to be 0.3-0.4 mohm cm and metallic conductivity was observed down to 0.5 K. First-principles calculations demonstrated that the electronic structure and Fermi energy of Li 1-x Sn 2+x P 2 are significantly dependent upon x. Electrochemical measurements using a single-particle technique demonstrated the activity of Li 1-x Sn 2+x P 2 as an anode material for rechargeable Li-ion batteries.