Sheet-Type Electrodes Prepared by Solution-Process for All- Solid- State Li-Ion Batteries

Abstract

Bulk-type all-solid-state lithium-ion batteries (ASLBs), based on composite-structured electrode and electrolyte layers, have the potential to outperform the conventional lithium-ion batteries (LIBs) in terms of safety and energy density. Owing to high ionic conductivities (max. 10-2 S cm-1) and mechanical sinterability, sulfide-based solid electrolyte(SE) materials are considered as the key to the development of high-performance bulk-type ASLBs. While the conventional preparation of lab-scale bulk-type ASLBs is based on mixing a particulate mixture of active materials, SEs, and conductive additives in a dry condition, addition of polymeric binders would be necessary to obtain sheet-type electrodes for practical ASLBs. Thus, wet-slurry process using solvents to dissolve the polymeric binders should be applied for fabrication of the ASLB electrodes. However, it is complicated because of severe restrictions in available solvents and binders. As the sulfides show reactivity toward common polar solvents such as N-methyl-pyrrolidinone (NMP), nonpolar or less polar solvents such as toluene and xylene should be used. In turn, appropriate binders such as nitrile−butadiene rubber (NBR) and styrene−butadiene rubber (SBR), which can be dissolved into the nonpolar or less polar solvents, must be used. Moreover, in the case of the slurry for ASLBs careful engineering should be made to achieve favorable percolations in terms of not only electronic but ionic pathways by homogenizing three components of active materials, SEs, and conducting additives, which is contrasted by homogenization of only two components of active materials and conducting additives in the case of the slurry for conventional LIBs. In this presentation, our recent results of scalable fabrication of sheet-type ASLBs by infiltrating conventional LIB electrodes with solution-processable SEs will be presented.