Performance improvement of all-solid-state Li-S batteries with optimizing morphology and structure of sulfur composite electrode

All-solid-state Li-S batteries are fabricated with lithium silicide anodes (Li4.4Si), sulfide-based glass electrolyte (Li2S-P2S5), and sulfur composite (sulfur + acetylene black + solid electrolyte) cathode. Various preparation methods, such as mortar mixing (MM), ball milling (BM), and secondary ball milling (SBM), are applied for the sulfur composite cathode. By changing the preparation methods from MM to SBM, the electrode morphology and the electrolyte/cathode interfacial area are significantly improved, as confirmed with BET, SEM/EDS, and GITT analyses. These effects are reflected in the charge-discharge tests, resulting in higher capacity of the SBM cell. Pyrolytic graphite sheet (PGS) is employed for the gradient structure of the sulfur composite cathode, and the cell with PGS shows higher volumetric capacity and equivalent gravimetric capacity than do cells with the conventional cathode structure. This is because the cathode thickness is reduced and the electron transport to/from the current collector is facilitated. Thus, the present work indicates that design and preparation of the electrode greatly affects the performance of solid state batteries with sulfur composite cathodes. (C) 2017 Elsevier B.V. All rights reserved.