Elucidation of the reaction mechanism upon lithiation and delithiation of Cu0.5TiOPO4

Abstract

The reaction mechanism of Cu_0.5TiOPO₄ upon lithiation and delithiation was elucidated by XAS, ³¹P-NMR, XRD, EDX, and electrochemical methods. The material reacts with a combined insertion and conversion process, in which first copper is extruded irreversibly by forming LiTiOPO₄. Afterwards, Ti⁴⁺ is reduced reversibly in an insertion reaction followed by a conversion reaction. The conversion reaction leads to amorphization of the sample while titanium is reduced to oxidation states below 2+.