[11a-N104-1~8] 9.5 New functional materials and new phenomena

[11a-N104-2] How does the Li-distribution in the 16d sites determine the stability of A₃(Li,Ti₅)O₁₂(A = Li and Na)?

〇Kohei Tada¹, Hiroyuki Ozaki¹, Tetsu Kiyobayashi¹, Mitsunori Kitta¹, Shingo Tanaka¹ (1.AIST)

Keywords:cubic crystal system (spinel), stable anode for Li-ion battery, stable anode for Na-ion battery

Li₃(Li,Ti₅)O₁₂ (LTO) is a stable and safe negative electrode material for Li-ion batteries, and its Na substitute Na₃(Li,Ti₅)O₁₂ (NTO) is a counterpart for the Na-ion battery. In LTO and NTO, a sixth of the Ti-sites (16d) in the spinel framework is replaced by Li: Li mixing in the 16d sites. Herein, we statistically analyzed the DFT total energy of more than 2×10⁴ model structures of LTO and NTO that were extracted from the 4×10⁸ possible combinations of Li-mixing with computer-aided symmetry analysis and an automated model building system. We found that LTO and NTO stability can be well explained by the apparent Coulombic repulsion between Li⁺ in the 16d sites as if they were placed in a matrix of dielectric constants of 1.92 and 2.04 for LTO and NTO, respectively. These results suggest that the spinel framework tolerates the structural instability and variety to some extent, which is important in constructing a spinel structure with the mixing of other cations.