Li-richening strategy in Li2ZrCl6 lattice towards enhanced ionic conductivity

All-solid-state Li batteries (ASSLBs) with solid-state electrolytes (SSEs) are exciting candidates for next-generation energy storage and receive considerable attention owing to their reliability. Halide SSEs are promising candidates due to their excellent stability against 4 V-class layered cathodes. Compared with Li3InCl6 or Li3ScCl6, the low ionic conductivity of Li2ZrCl6 (LZC) is a challenge despite its low raw-material cost. Herein, we report a family of Li-Richened chloride, Li2+2xZr1–xMxCl6, which can be used in high-performance ASSLBs owing to its high ionic conductivity (up to 0.62 mS cm−1). The theoretical (ab initio molecular dynamics simulations) and experimental results prove that the strategy of aliovalent substitution with divalent metals to obtain Li-Richened LZC is effective in improving Li+ conductivity in SSEs. By combining Li2.1Zr0.95Mg0.05Cl6 (Mg5-LZC) with a Li–In anode and a LiCoO2 cathode, a room-temperature ASSLBs with excellent long-term cycling stability (88% capacity retention at 0.3C for 100 cycles) and high-rate capability (121 mA h g−1 at 1C) is reported. This exploratory work sheds light on improving the Li+ conductivity of low-cost LZC-family SSEs for constructing high performance ASSLBs.