Synthesis of nano-crystalline LiNbO3-decorated LiCoO2 and resulting high-rate capabilities

Abstract

We decorated nano-crystalline LiNbO3 (LN) particles, which played the role of artificial solid electrolyte interfaces (SEIs) on an active material, namely LiCoO2 (LC). Conventional one-step synthesis using metal organic decomposition (MOD) was used initially, but resulted in the presence of an undesired Li-rich compound, Li3NbO4 (L3N), along with a counterpart phase, Co3O4. Hence, we incorporated crystalline LN into the LC matrix via a two-step synthesis method. Treatment at 500–700°C resulted in single-phase LN-decorated LCs with improved high rate capabilities. The improvement in the rate capability is related to the temperature dependencies of the two most important parameters: 1) the degree of LN crystallinity, which corresponds to the improvement in the polarization, and 2) the density of the triple phase junctions, which act as active Li ion pathways. The optimized capacity, 78mAh/g at 20C, of the specimen annealed at 600°C was 20C, which is approximately 1.7-fold larger than that of amorphous LN-decorated LC and is 2.6 times higher than that of bare LC. This implied the introduction of a dielectric polarization architecture had a greater impact on the improvement to the rate capability than Li transportation through the amorphous LN.