Lithium Insertion in LiCr3 O 8, NaCr3 O 8, and KCr3 O 8 at Room Temperature and at 125°C

Abstract

Lithium insertion and deinsertion reactions have been carried out with , , and chemically and electrochemically at room temperature and at 125°C. The electrochemical experiments were performed with a nonaqueous liquid electrolyte at room temperature and with a polymer electrolyte at high temperature. At both temperatures, inserts chemically and electrochemically ca. 4 and 5 Li per formula unit, respectively. Experimental data reveal that the reaction involves major structural changes. Insertion of only small amounts of Li leads to irreversible structural breakdown. At elevated temperatures, the isostructural compounds and are able to accommodate more than . During this process, minor structural changes are observed. At room temperature, and also accommodate Li topotactically, but the maximum number of Li inserted per formula is close to and . Lithium ion diffusion coefficients are similar for the two compounds in the comparable composition range. Thermally, the fully lithiated compounds appear to be as stable as the pristine materials.