Application of operando X-ray diffraction to evaluate phase transformations of a LiCoVO₄ cathode

Abstract

Characterization by in situ or operando methods is very important to deeper understand the chemical and electrochemical processes, as well as the degradation processes that occur during the operation of a lithium-ion battery. A variant of the operando electrochemical cell for the simultaneous study of the structural and electrochemical behavior of electrode materials was proposed. In designing the cell, special attention was paid to the simplicity of assembly, as well as to the use of the materials that provide high chemical and electrochemical stability when cycling in the potential range from 0 to 5 V vs. Li+/Li. The paper presents the first results of the X-ray diffraction studies of the operando material of cobalt (II)-lithium vanadate (V) (LiCoVO4) with the inverted spinel structure. The new results concerning the structural behavior of LiCoVO4 showed a single-phase mechanism of lithium de/intercalation with a reversible change of the unit cell volume in the first cycle of about 3.7%. The reversibility of the volume change decreases in the second cycle along with the decrease of the cycling capacity, which is explained by rearrangement in the cationic sublattices of the inverted spinel.

Keywords

• lithium-ion battery
• cathode material
• cobalt(ii)-lithium vanadate(v)
• licovo₄
• x-ray diffraction
• operando