ИСТИНА

Layered structure of vanadium (III) oxychloride together with its high theoretical capacity (260 mAh/g per 1 alkali cation) allows considering VOCl as a perspective electrode material for metal-ion batteries1. Electrochemical Li+ and Na+ intercalation into VOCl was investigated by cycling voltammetry and galvanostatic charge-discharge using two-electrode coin-type cells assembled in argon-filled glove-box. Electrode characterization was carried out by means of ex situ powder X-ray difraction and energy-dispersive X-ray spectroscopy. Structure transformation caused by Li+ and Na+ (de)intercalation into VOCl electrode material was studied by operando synchrotron X-ray powder diffraction. Irreversible phase transition of VOCl occurring during the first charge in both Li- and Na-cell has been revealed. As a result, the isostructural phases with the structure closely related to the host structure (aInt  5сVOCl, bInt  2aVOCl, cInt  bVOCl) are formed. Upon further cycling these phases participate in reversible red-ox reactions followed by progressive conversion with reversible capacity of ca. 100 mAh·g–1.