Reactivity evaluation of NASICON-type solid electrolyte LATP, LAGP and Olivine-type cathode LCP

Abstract

• The solid-state reaction and phase decomposition were remarkable between LAGP-LCP. • LATP-LCP has high thermal stability, no formation of secondary phases at 800 °C. • Co diffused from LCP to LATP and dissolved into the LATP. • Co is a key element that improves the low-temperature sinterability of LATP-LCP. The chemical reactivity and thermal stability of the NASICON-type Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) solid lithium-ion conductive materials with the Olivine-type LiCoPO 4 (LCP) cathode active material were evaluated. The LATP or LAGP and LCP powders were mixed, uniaxially-pressed, and heat-treated in the air at 800, 900, and 1000 °C for 10 h. The obtained sintered bodies were crushed into powders, then characterized by X-ray diffraction and scanning electron microscopy together with energy-dispersive X-ray spectroscopy. LAGP-LCP decomposes and melts at 800 °C, and produces some different phases. On the other hand, LATP-LCP produces different phases at 900 °C, although it does not produce a different phase at 800 °C, thus forming a dense microstructure. This shows that the LATP-LCP system is an excellent combination of electrolyte and cathode active material that can be sintered in air. This mixed composite can also be used as a composite electrode in bulk-type lithium-ion batteries.