Flux Growth and Surface Modification of Highly-Crystalline Active Materials and Solid Electrolytes for High Performance Libs

Abstract

Materials for energy devices are often multicomponent with a number of interfaces and heterojunctions. In particular, lithium-ion batteries (LIBs) have been studied extensively because of their potential use as power sources. Recently, there has been a particular focus on all-solid-state LIBs (and high-performance LIBs). They have attracted considerable attention due to their high energy densities, which are the result of device miniaturization, and high safety due to their non-flammability. However, there is an extremely large innovation gap between general purpose LIBs and all-solid-state LIBs due to difficulties in the smooth transfer of lithium ions, i.e., the diffusion of lithium ions and electrons are disturbed at the interfaces of different solid materials. Therefore, we have tried to control and design their interfaces between active materials and solid electrolytes and fabricate materials for all-solid-state LIBs based on crystal science and engineering. Our research group has developed flux crystal growth and its extended methods for the preparation of high crystalline materials. Flux method is a liquid phase crystal growth in which idiomorphic highly crystalline particles can be obtained below the melting point of the target. Therefore, outmost crystal planes are tuned by our techniques where they have desired various ion and electron paths (i.e., hyper-spaces). In addition, the grown crystals are expected to have high crystallinity because diffusion and rearrangement of atoms easily occurred compared to conventional particle fabrication methods. Recently, we have developed a flux method to fabricate crystal layers on various substrates, which is called "flux coating method". For example, the target LIB-based materials are cathode active materials such as LCO, LNM, NCM, LFP and so on, anode active materials such as LTO, TNO and the related materials, and solid electrolytes such as LLZ, LLT, LLN, etc. and their crystal layers. Furthermore, their surface conditions are precisely controlled in our laboratory. Details on material design and hyperspace control of flux-grown crystalline particles and crystal layers via flux-related techniques will be reported at the 244th ECS Meeting.