Synthesis and electrochemical properties of Li+-ion conducting solid electrolytes in the system xLiCl·(25-x)LiBr·75Li3PS4

The sulfide solid electrolyte xLiCl·(25-x)LiBr·75Li₃PS₄ was synthesized by a two-step glass-ceramic method. In the first step, amorphous precursors were obtained by a high-energy ball-milling method, and in the second step, the obtained precursors were heated up to a temperature in the range of 165 to 180 °C in order to obtain crystalline samples. The LGPS-like crystalline phase was precipitated in the heat-treated samples in the 0 < x < 12.5 composition range. The glass-ceramic samples showed high ion conductivities of 3 × 10⁻³ to 4 × 10⁻³ S cm⁻¹ at 25 °C. A charge-discharge test was conducted on an all-solid-state test cell using the 7.5LiCl·17.5LiBr·75Li₃PS₄ (mol%) glass-ceramic sample as a separator. The cathode composite of the test cell was a mixture of LiNi_1/3Mn_1/3Co_1/3O₂ (NMC) active materials, the solid electrolyte, and acetylene black. The test cell exhibited high electrochemical stability and the electrochemical capacity based on NMC active materials was 145 mAhg⁻¹.