Solid Electrolyte Coated NCM523 for Composite Cathode in All-Solid-State Batteries

Abstract

All-solid-state battery using sulfide solid electrolyte has advantages such as high lithium ionic conductivity and wide electrochemical stability window. Although it is attracting great attention in that it is capable of high power and high energy density, there are problems to be improved.Organic liquid electrolytes in conventional lithium ion batteries have excellent wettability and can form uniform lithium ion transfer channels in electrodes. However, in the case of all-solid-state battery, the formation of a solid-solid interface is limited due to the solid characteristics. In addition, the degradation of the interfacial contact between the active material and solid electrolyte in the composite electrode due to the volume change of the active material with (de)-intercalation of lithium ion during cycling causes loss of the lithium ionic pathway and deterioration of cell performance. This study focuses on improving battery performance by coating the surface of active material with solid electrolyte to maintain an even lithium ion transfer path in the composite electrode. The solid electrolyte coating of the active material has a decisive effect on the electrochemical behavior of the cell because it affects the formation of smooth lithium ionic pathway and suppression of voids in the composite electrode. Therefore, the focus of this study is to confirm the formation of uniform solid electrolyte coating layer according to the size of the solid electrolyte.Therefore, the particle size of the solid electrolyte was diversified using a liquid-phase process and a dispersant, and the solid electrolyte coating was performed using a dispersion process. It was confirmed that an even solid electrolyte coating layer was formed as the particles size of the solid electrolyte decreased, and the electrochemical performance was improved due to the solid electrolyte coating layer. In addition, it was confirmed that the lithium ionic pathway was maintained even after long cycling with the solid electrolyte coating layer, and also the side reactions occurred less according to the homogeneous electrochemical reaction.