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

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.