High-Capacity Li<sup>+</sup> Storage through Multielectron Redox in the Fast-Charging Wadsley–Roth Phase (W<sub>0.2</sub>V<sub>0.8</sub>)<sub>3</sub>O<sub>7</sub>
Kira E. Wyckoff, Daniel D. Robertson, Molleigh B. Preefer, Samuel M. L. Teicher, Jadon Bienz, Linus Kautzsch, Thomas E. Mates, Joya A. Cooley, Sarah H. Tolbert, Ram Seshadri
Abstract
The Wadsley–Roth phase (W0.2V0.8)3O7, crystallizing in a structure obtained through crystallographic shear of 3 × 3 × ∞ ReO3 blocks, is a somewhat rare exemplar for this class of compounds in that it contains a relatively small amount of 4d and/or 5d transition elements. Here, we demonstrate that it functions as a high-rate, high-capacity material for lithium-ion batteries. Electrochemical insertion and deinsertion in micron-sized particles made by conventional solid-state preparation and in sub-100 nm particles made by combining sol–gel precursors with freeze-drying methods indicate good rate capabilities. The materials display high capacity—close to 300 mA h g–1 at low rates—corresponding to the insertion of up to 1.3 Li per transition metal at voltages above 1 V. Li insertion is associated with multielectron redox for both V and W observed from ex situ X-ray photoelectron spectroscopy. The replacement of 4d and 5d elements with vanadium results in a higher voltage than seen in other, usually niobium-containing shear-structured electrode materials, and points to new opportunities for tuning voltage, electrical conductivity, and capacity in compounds in this structural class.