Interfacial phenomena between lithium ion conductors and cathodes

Nanocomposites of a lithium ion conductor Li1.3Al 0.3Ti1.7(PO4)3 and electrode materials (TiO2 and FePO4) were prepared to investigate interfacial structure and ionic conductivity at the interface between the solid electrolyte and electrode materials. It was revealed that lithium ions in the solid electrolyte were attracted to the cathode materials with increasing electrode potential, which increases lithium vacancies in the solid electrolyte. For the FePO4 containing composites, due to the high electrode potential, lithium transfer across the interface and ionic conduction through the cathode materials was remarkable. The results suggest that severe lithium depletion occurs and interfacial resistance is large at the interface of high ionic conductors and cathode materials. The space charge layer thickness is also discussed

Reduced Grain Boundary Resistance by Surface Modification

Interfacial resistance is one of the severe problems in composite electrodes of all solid state batteries (ASSBs), especially oxide-type ASSBs. Conflicts between poor sinterability and possible unfavorable reaction with active materials limit applicable materials and processes. In this report, a novel approach is proposed to decrease grain boundary resistance among nonsintered solid electrolyte particles. The concept is successfully demonstrated, and the nonsintered grain boundary resistance of a highly conducting solid electrolyte (Li_1.3Al_0.3Ti_1.7(PO₄)₃) was suppressed by being coated with poorly conducting solid electrolyte (Li₂SiO₃). Increased total conductivity and variation of apparent activation energy are well explained from the viewpoint of defect chemistry