Reversible Cation-Mediated Anionic Redox in Defect Spinel Structure for High Power Batteries

Abstract

With ever-increasing energy demand, more efforts are dedicated to designing innovative electrode materials providing higher storage capability and power output. As it has been demonstrated recently, the use of mixed cation–anion redox reactions opens up new possibilities for the significant rise of material's capacity and unusual electrochemical characteristics of lithium-ion battery electrodes. In this paper, a new type of fast cation-mediated anionic redox reaction in the 3D spinel structure is presented. Li0.98K0.01Mn1.86Ni0.11O4 shows 170% of stoichiometric spinel theoretical capacity without voltage hysteresis or significant capacity and voltage fading attributed to limitations of reversible anionic redox. The authors’ sol–gel-derived defect spinel structure can deliver 250 mAh g−1 at 1C and retain 64% of this capacity under a high 50C current rate. The observed electrochemical process shows the reversibility unseen before in mixed cation–anion redox cathode materials for Li-ion systems.