Progress in lithium thioborate superionic conductors

All-solid-state batteries can greatly improve safety and energy/power density, bringing superionic conductors to the research frontier of this field. Among all studied solid electrolytes, sulfides have become the most promising technical system due to their highest ionic conductivity, desirable mechanical ductility, and good interfacial contact with electrodes. Theoretical calculations predicted that lithium thioborate materials may have extremely high lithium-ion conductivity, good electrochemical stability, and thus great application promise. In this paper, the research history of lithium thioborate (Li–B–S) solid electrolytes is summarized and reviewed, with elaborations on milestone discoveries. Furthermore, both glassy and crystalline Li–B–S solid electrolytes are discussed in details, followed by introductions of Li–B–S system from experimental and theoretical perspectives. Moreover, the existing challenges and potential solutions are also proposed for the benign development of this field in the future.Graphical abstract