Highly Reversible Solid-State Silicon Anodes Enabled by Hydride Based Electrolytes

Silicon is considered a promising candidate for anodes in solid-state batteries due to its high energy density and unique properties in addressing problems associated with Li metal anodes such as dendrite formation and morphological instability. Despite many exciting results from previous works on solid-state Si anodes, the initial Coulombic efficiency, a critical parameter that characterizes the electrochemical reversibility for the first cycle and directly influences the battery's energy density, has not been well considered. In this presentation, we report our study on the (electro)chemical stability between Si and three representative solid electrolytes, including a typical sulfide (75Li₂S-25P₂S₅), an iodide-substituted sulfide (70(0.75Li₂S-0.25P₂S₅)-60LiI) and a hydride-based solid electrolyte (3LiBH₄-LiI, LBHI). Our results indicate that LBHI demonstrates superior electrochemical and chemical stability with Si anodes compared with sulfide-based electrolytes, enabling a high-performance solid-state Si anode with a record high initial Coulombic efficiency of 96.2% among all Si anodes reported to date. The excellent (electro)chemical reversibility of Si anodes was also demonstrated in solid-state full cells with nickel-rich layered oxide cathodes. The results highlight the importance of solidifying Si anode to improve its performance, and the excellent stability of hydride-based solid electrolytes also offers potential opportunities to be used as an interlayer or 3D ionic framework for other low voltage anodes, including Li metal.