Designing high-area-loading lithium metal batteries with in-situ polymerized electrolyte featuring gradient molar mass

In-situ polymerized solid-state lithium metal batteries have garnered significant attention due to their conformal interface contact and continuous pathways for lithium ion (Li + ) conduction. However, their electrochemical performance is often hindered by slow Li + transport within high-area-loading cathodes. This study presents an in-situ poly( ɛ -caprolactone) electrolyte with gradient molar mass (iGPCE) through lithium metal anode (LMA)-induced anionic ring-opening polymerization. Our electrochemical and kinetic analyses reveal that the iGPCE, characterized by low molar mass ( M ), significantly enhances Li + diffusion within high-area-loading cathodes and bulk electrolytes, thereby reducing concentration polarization and promoting uniform electrochemical reactions. Moreover, the high M region on LMA side acts as artificial solid electrolyte interphases, stabilizing the stripping and plating of lithium. Consequently, Li//LFP (20 mg cm −2 ) and Li//NCM622 (7.4 mg cm −2 ) utilizing iGPCE exhibit stable charge/discharge behaviors. This study offers a fresh approach to accelerate Li + diffusion kinetics of high-area-loading batteries and suggests broad applicability in other systems.