Variation of electrochemical performance of Li2ZrCl6 halide solid electrolyte with Mn substitution for all-solid-state batteries

Abstract

All-solid-state batteries (ASSLBs) have gained attention as a next-generation battery technology. Halide solid electrolytes may be a candidate material for next-generation batteries due to their high stability in combination with cathode-active materials and good deformability. However, the halide solid electrolyte exhibits low ionic conductivity compared to other solid electrolytes, such as oxide and sulfide solid electrolytes. In this study, in order to improve the ionic conductivity, a strategy is presented to increase the ionic conductivity by changing the Li + concentration and metal charge by doping Mn2+ in the trigonal Li2ZrCl6. Mn-doped Li2ZrCl6 is synthesized by high-energy ball-milling. Structural analysis is conducted by powder X-ray diffraction, 7Li-Nuclear magnetic resonance, Raman spectroscopy and X-ray photoelectron spectroscopy. Electrochemical performance is evaluated using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge measurement. Each value of ionic conductivity in the bare and optimized compositions is 0.4 mS cm−1 and 0.8 mS cm−1, respectively. The activation energy of Li2ZrCl6 and 5 mol% Mn doped Li2ZrCl6 is 0.342 and 0.326 eV. Galvanostatic charge-discharge is conducted to confirm cycling performance. The initial discharge capacity for Li2ZrCl6 and 5 mol% Mn-doped Li2ZrCl6 are 171.6 and 185.6 mAh g−1, respectively.