Co-sintering process of LiCoO 2 cathodes and NASICON-type LATP solid electrolytes studied by X-ray diffraction and X-ray absorption near edge structure.

The composites of a high-capacity cathode material in lithium-ion batteries, LiCoO 2 (LCO) and an oxide-based solid electrolyte, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), were sintered at various temperatures and their reaction products were subsequently identified by X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES). Rietveld analysis of XRD and the linear combination fitting of XANES showed that the reaction of LCO and LATP proceeds via three major steps; from 300 °C to 500 °C, LCO and LATP react with each other to form Co 3 O 4 , amorphous TiO 2 and Li 3 PO 4 ; from 500 °C at which crystalline LCO is completely decomposed, LATP reacts not only with remaining amorphous/low crystalline LCO but also with Co 3 O 4 to form LiCoPO 4 and TiO 2 ; from 700 °C to 750 °C, Co 3 O 4 and TiO 2 react with each other to form CoTiO 3 . The final products at 900 °C are LiCoPO 4 , CoTiO 3 , TiO 2 , and Li 3 PO 4 .