Inorganic all-solid-state lithium-sulfur batteries enhanced by facile thermal formation

All-solid-state lithium-sulfur batteries (ASSLSBs) are particularly promising for the high theoretical performance. The utilization of solid-state electrolytes (SSE) also prevents the shuttle effect of polysulfides, inhibits the dendrite growth and improves the safety. However, the cycling stability of current ASSLSBs is still hindered by the unstable interface at both S and Li electrodes, due to complex chemical and electrochemical reactions between solid electrolytes and Li/S electrodes. To turn complexity to simplicity, LiBH4 with high reductivity and high compatibility with Li metal anode is selected as the SSE, spontaneously diverting the obstacle focused on the interface between LiBH4 and S. Motivated by the electrochemical formation process of commercial liquid-electrolyte lithium-ion batteries, we employ a facile thermal formation technology to initially stabilize the intermediate phase between LiBH4 and S within ASSLSBs. Accordingly, such ASSLSBs with thermal formation process show improved cycling stability with a capacity decay of only 0.33% per cycle, lower than 0.71% of the counterpart without thermal formation. This work not only comprehensively elucidates the main component of this intermediate phase upon thermal formation, but also shows the possibility of the ASSLSBs working at a wide temperature range 60-125 °C, once coupled with suitable solid-state electrolytes.