Improving the Electrochemical Utilization of Oxide-Based LISICON-Type Solid Electrolyte for All-Solid-State Li Ion Battery Through Doping

As the solution of the environmental pollution problem, fossil fuels need to be replaced with eco-friendly energy. Accordingly, the demand for electric vehicles (EVs) and energy storage systems (ESSs) has been steadily increasing. Li-ion batteries (LIBs) have been considered as the most important energy storage technology because of their higher energy density than other batteries such as Ni-Cd, Lead acid batteries, etc. Many studies have been focused on electrode materials, separators, and electrolytes in the cell platform with liquid electrolytes in order to increase the energy density of LIBs. However, it is gradually approaching a physiochemical limit to further increase the energy density of LIB with liquid electrolytes and safety issues that are related to liquid electrolytes have got severed in large scale systems such as EVs and ESSs. To overcome these problems and issues, all-solid-state batteries with oxide-based solid electrolytes (SEs) have been paid a lot of attention as a next generation energy storage platform to simultaneous achieve both high energy density and superior safety. Among oxide based SEs, lithium superionic conductor (LISICON) have several advantages over others with respect to superior compatibility with high capacity electrode materials such as high Ni layered materials partly due to a low sintering temperature (700 °C) and good wetting property with Li metal anode. Low sintering temperature of LISICON SE can enable to use co-sintering process for integrating composite electrodes with LISICON SE layer resulting in very nice interfacial contact and low resistance. As a result, the LISICON SE based solid-state Li metal cell can be operated at room temperature. (<i>Seungjun Woo, Byoungwoo Kang, Journal of Materials Chemistry A, 10.43, 23185-23194)</i> Even with these fascinating properties, the LISICON-type SE still has poor Li ionic conductivity (~ 4.0x10^-6 S/cm), and thereby the electrochemical utilization of the SE in ASSB is not trivial. In this study, we tried to increase the Li ionic conductivity of the LISICON-type SE by using doping. The electrochemical stability of doped-LISICON was evaluated to confirm whether the advantages of LISICON were maintained. Furthermore, we discuss about the effect of the dopants on fascinating compatibilities of LISICON-type SE.