Effect of mechanical stress on lithium chemical potential in positive electrodes and solid electrolytes for lithium ion batteries

Abstract

Effects of mechanical stress on lithium chemical potential in electrodes and electrolytes for all-solid-state lithium ion batteries were investigated. Dense film electrodes of LiCoO2 or LiMn2O4 were symmetrically deposited on both surfaces of a plate of various solid state lithium ion conductors, such as Li0.29La0.57TiO3, Li7 La3Zr2O12 and Li1+x+yAlx(Ti,Ge)2?xSiyP3?yO12. Mechanical stress was applied to the specimen by four points bending tests while measuring electromotive force (EMF) between the two electrodes. EMF proportional to the applied stress was observed. EMF was significantly dependent on the electrode material, but was almost independent of the electrolyte material. These results indicated that lithium chemical potential varied under mechanical stress both in the electrode and electrolyte but the influence of mechanical stress appeared more notably in the electrode than the electrolyte. The lithium chemical potential changes in the electrode and the electrolyte under mechanical stress were discussed based on the idea of local equilibrium.