| Abstract
| - We report on the chemical/electrochemical reactivity of the insulating layered V-based silicate-phaseLi2VOSiO4 toward Li. The silicate phase, made by a ceramic approach and consisting of 5−20 μmagglomerates, exhibits only a slight reactivity with Li in chemical or electrochemical reactions. By ballmilling Li2VOSiO4 in the presence of carbon, we succeeded in preparing composites that reversiblyreact with 0.7 Li+ per unit formula at an average voltage of 3.6 V vs Li+/Li0. This electrochemicalreactivity was chemically mimicked using NO2BF4 or Br2 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 inspace group P4 (a = 6.206 Å, c = 4.5715Å), whereas the precursor lithiated phase crystallizes in P4/nmm (a = 6.366(9) Å, c = 4.456(6) Å). Because silicates such as phosphates are cheap and can also bemade redox-active by carbon coatings, they should not be overlooked as possible electrode candidates infuture research.
- Li2VOSiO4, whose structure can be viewed as being packed along the c-direction of [VOSiO4]n sheets linked together by lithium ions located in distorted octahedral sites coordinated by oxygen, can reversibly react with 0.7 Li+ per unit formula at an average voltage of 3.6 V vs Li+/LiO in the presence of carbons.
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