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

Abstract

A new ternary layered pnictide, Li<sub>1-x</sub>Sn<sub>2+x</sub>P<sub>2</sub>, 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 <sup>31</sup>P nuclear magnetic resonance analysis. The lattice thermal conductivity of Li<sub>1-x</sub>Sn<sub>2+x</sub>P<sub>2</sub> was found to be relatively low (1.2 Wm<sup>−1</sup>K<sup>−1</sup> at 525 K). The room-temperature electrical resistivity of Li<sub>1-x</sub>Sn<sub>2+x</sub>P<sub>2</sub> 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<sub>1-x</sub>Sn<sub>2+x</sub>P<sub>2</sub> are significantly dependent upon x. Electrochemical measurements using a single-particle technique demonstrated the activity of Li<sub>1-x</sub>Sn<sub>2+x</sub>P<sub>2</sub> as an anode material for rechargeable Li-ion batteries. <br>