Molten Salt Synthesis of a Single-Crystal LiNi0.5Mn1.5O4 Cathode with an In Situ Constructed Stable Interface for 4.8 V-Class All-Solid-State Batteries

• • Single-crystal LNMO synthesized from commercial polycrystalline powder via molten salt flux yields submicron particles with improved contact to Li3InCl6 SE, enabling higher specific capacity than pristine polycrystalline LNMO in ASSLB composite cathodes. • • In situ formation of a uniform Li2MoO4 coating during molten salt synthesis suppresses oxidative side reactions at the LNMO/Li3InCl6 interface, allowing stable cycling at a 4.8 V upper cutoff voltage—a critical threshold where uncoated LIC undergoes decomposition. • • The molten salt approach eliminates the need for separate coating steps, reducing process complexity and cost while utilizing low-cost, Co-free LNMO, which is essential for commercial viability of high-voltage ASSLBs. • • The single-crystal morphology mitigates chemo-mechanical failure by reducing grain boundary density and preventing particle cracking, addressing a key degradation mode in polycrystalline LNMO-based composite cathodes.