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-xSn_2+xP₂, 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 ³¹P nuclear magnetic resonance analysis. The lattice thermal conductivity of Li_1-xSn_2+xP₂ was found to be relatively low (1.2 Wm⁻¹K⁻¹ at 525 K). The room-temperature electrical resistivity of Li_1-xSn_2+xP₂ 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-xSn_2+xP₂ are significantly dependent upon x. Electrochemical measurements using a single-particle technique demonstrated the activity of Li_1-xSn_2+xP₂ as an anode material for rechargeable Li-ion batteries.