Deciphering\nChemical/Electrochemical Compatibility\nof Li<sub>3</sub>InCl<sub>6</sub> in 5.2 V High-Voltage LiCoO<sub>2</sub> All-Solid-State Batteries

Large interfacial resistance is a widely recognized impediment\nto the advancement of high-voltage, all-solid-state batteries. However,\na comprehensive understanding of the fundamental cause behind the\ninterfacial resistance between solid electrolytes and typical layered\noxide cathodes has not yet been achieved. Here, we investigated the\nhigh-voltage stability of Li<sub>3</sub>InCl<sub>6</sub> and elucidated\nthe underlying interfacial electrochemical reactions between LiCoO<sub>2</sub> and Li<sub>3</sub>InCl<sub>6</sub>. The pairing of Li<sub>3</sub>InCl<sub>6</sub> with LiCoO<sub>2</sub> exhibited a superior\ncapacity retention of 73.6% even at 5.2 V, much higher than 28.2%\ncharged at 4.6 V in lithium-ion batteries after 70 cycles. The enhanced\nhigh-voltage stability of ASSBs is attributed to the stable interface\nformed between LiCoO<sub>2</sub> and Li<sub>3</sub>InCl<sub>6</sub> and the reinforced surface and bulk structure stability. On the\nother hand, the ultrahigh voltage still causes the partial decomposition\nof Li<sub>3</sub>InCl<sub>6</sub> and generates interfacial compounds\nsuch as InClO and cobalt and indium chlorides/oxides.