Design of High‐Energy Anode for All‐Solid‐State Lithium Batteries–A Model with Borohydride‐Based Electrolytes

Abstract To produce high‐energy‐density all‐solid‐state secondary batteries, it is essential to develop high‐energy anodes comprising hosts that enable nonmetallic lithium insertion without dendritic growth and the formation of high‐resistance interphases while maintaining intimate interfacial contact with the solid electrolyte. Using a LiBH ₄ solid electrolyte that is compatible with active lithium and exhibits high conformability, this study proposes a model high‐energy anode: a massive artificial graphite (MAG) | indium‐dispersed acetylene‐black–LiBH ₄ mixture. This electrode achieves a reversible lithiation and delithiation capacity of 589 and 466 mAh·g ⁻¹ , surpassing those of intercalation‐type anodes. This performance is attributed to the low degree of graphitization of acetylene black, which serves as a host for dendrite‐free ionic lithium insertion; indium, which enhances shape conformability; and the highly graphitized MAG layer, which suppresses segregation between acetylene black and indium. This function‐sharing design provides useful guidelines for the development of high‐energy anodes for all‐solid‐state batteries.