Ionic conductivity regulating strategies of sulfide solid-state electrolytes

Sulfide solid-state electrolytes (SEs) are the most promising candidate to be employed in high-energy-density all-solid-state lithium batteries due to high ionic conductivity. Recently, significant progress has been made in sulfide SEs to achieve the ionic conductivities of more than 10−3 S cm−1 at room temperature. However, the lack of systematic summarization of optimization methods to enhance the ionic conductivity restricts the development of sulfide SEs with higher ionic conductivity. Herein, this review summarizes the modulation of the ionic conductivity of sulfide SEs, with particular attention to the latest research advances that have emerged from the three different strategies, including ion doping strategy, lithium content control and preparation method optimization to achieve high ionic conductivity. In addition, the internal mechanisms and effects of the three strategies for improving ionic conductivity are discussed in detail. Finally, future challenges and research directions are presented to improve the ionic conductivity of sulfide SEs and looks forward to the development trend of sulfide all-solid-state lithium-ion batteries.