Sheet-Type Electrodes for All-Solid-State Lithium-Ion Batteries

Abstract

Safety concerns of conventional lithium-ion batteries (LIBs), which originate from flammable liquid electrolytes, are one of the most critical obstacles for large-scale applications such as electric vehicles and energy storage systems. In this regard, composite-structured bulk-type all-solid-state lithium-ion batteries (ASLBs) employing nonflammable inorganic solid electrolytes (SEs) have attracted much attention as an ultimate solution. In particular, promising electrochemical performances for bulk-type ASLBs were reported by employing sulfide SEs, which is attributed to their high ionic conductivities (max. ~10-2 S cm-1) and favorable mechanical property (deformability). In most previous reports, lab-scale fabrication of bulk-type ASLBs was based on dry-mixing of a particulate mixture of active materials, SEs, and carbon additives. However, practical ASLBs should employ large-sized sheet-type electrodes. Thus, a fabrication protocol based on wet-slurry method using polymeric binders, which is similar to that for the conventional LIB electrodes, would be inevitable. However, the wet-slurry process using sulfide SEs is not easy because of severe reactivity of sulfide SEs toward conventional polar solvents such as N-methyl pyrrolidinone and water. Moreover, satisfying both electronic and ionic percolations for three components of active materials, SEs, and super P is challenging. In this regard, innovations in fabrication of sheet-type electrodes for ASLB are imperative for their practical applications. In this presentation, our recent results on new scalable fabrication protocols for ASLB electrodes will be presented.