Investigation of Reversible Li Insertion into LiY(WO4)2

The layered structure of LiY(WO4)2 accommodates a reversible insertion of two Li per formula unit near 1.5 V versus Li+/Li0. At low charge/discharge rates, there is a voltage step on charge from 1.55 to 1.6 V at one Li extraction per formula unit, the efficiency of electrical energy storage is reasonable, and the specific capacity is 90 m Ah g–1. At higher rates, less than one Li per formula unit is inserted reversibly. A solid-electrolyte interphase (SEI) is formed in the voltage range 1.2 < V < 1.4 V versus Li+/Li0 on the initial charge.