Electrochemical Reactivity of Li₂VOSiO₄ toward Li

We report on the chemical/electrochemical reactivity of the insulating layered V-based silicate-phase Li 2 VOSiO 4 toward Li. The silicate phase, made by a ceramic approach and consisting of 5−20 μm agglomerates, exhibits only a slight reactivity with Li in chemical or electrochemical reactions. By ball milling Li 2 VOSiO 4 in the presence of carbon, we succeeded in preparing composites that reversibly react with 0.7 Li + per unit formula at an average voltage of 3.6 V vs Li + /Li 0 . This electrochemical reactivity was chemically mimicked using NO 2 BF 4 or Br 2 and LiI as oxidizing and reducing agents, respectively. Through a combination of X-rays and HRTEM measurements, we showed that the insertion−deinsertion mechanism is a two-phase process with poor kinetics. The delithiated phase crystallizes in space group P 4 ( a = 6.206 Å, c = 4.5715Å), whereas the precursor lithiated phase crystallizes in P 4/ nmm ( a = 6.366(9) Å, c = 4.456(6) Å). Because silicates such as phosphates are cheap and can also be made redox-active by carbon coatings, they should not be overlooked as possible electrode candidates in future research.