Owing to their deformability and good (electro)chemical-oxidation stability, halide superionic conductors have emerged as enablers for practical all-solid-state batteries. Herein, we report the dynamic structural evolution of Li3YbCl6, which varies with the heat treatment temperature (400 vs. 500 °C) and aliovalent substitutions with Hf4+ or Zr4+. It is observed that slight differences in Li+ conductivities (0.19 vs. 0.14 mS cm−1 at 30 °C) and activation energies (0.47 vs. 0.53 eV) between unsubstituted Li3YbCl6 heat-treated at 400 and 500 °C diverge upon aliovalent substitution, which results in the evolution of monoclinic and orthorhombic phases, respectively. Enhanced Li+ conductivities reaching 1.5 mS cm−1 with an activation energy of 0.26 eV (Li2.60Yb0.60Hf0.40Cl6 prepared at 400 °C) upon Hf4+- or Zr4+-substitution are ascribed to the optimal concentration of charge carriers of Li+ and vacancies. Importantly, the exclusive comparison of crystal structures affecting Li+ conductivity in halide superionic conductors is enabled for the first time, demonstrating that it is more favorable for the cubic close-packed (ccp) monoclinic structure as compared to the hexagonal close-packed (hcp) orthorhombic structure. Furthermore, the excellent reversibility of single-crystalline LiNi0.88Co0.11Al0.01O2 in all-solid-state cells at 30 °C was achieved by employing ccp monoclinic Li2.60Yb0.60Hf0.40Cl6 prepared at 400 °C with a capacity retention of 83.6% after 1000 cycles.
Bibliographical noteFunding Information:
This research was supported by the Technology Development Program to Solve Climate Changes and by Basic Science Research Program of the National Research Foundation (NRF) funded by the Ministry of Science & ICT (grant no. NRF-2017M1A2A2044501, NRF-2018R1A2B6004996, and NRF-2017M1A2A2044502), and by the Materials and Components Technology Development Program of MOTIE/KEIT (grant no. 20012216).
© 2021 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering