Influence of anion substitution on 3D-architectured Ni-Co-A (A=H, O, P) as efficient cathode materials towards rechargeable Zn-based battery

Abstract

Among various Zn-based batteries, transition metal compounds have been widely studied as cathode materials in alkaline electrolyte. However, the correlation between anion species and the electrochemical performance of corresponding compounds is still not well understood. Here, we construct a 3D-architecrured F doping Ni/Co hydroxides/oxides/phosphides (FNCA, A = H, O, P) as the model materials and deeply explore the effect of anion substitution on cathode material for Zn batteries. Electrochemical measurements are combined with theoretical calculations to reveal the mechanisms of FNCA delivering considerable dissimilarity in electrochemical properties. In-depth analysis suggests that the surface-dominated redox behaviors are greatly affected by the anion substitution, though the reversible capacity is just produced by the valence change of metal cations. The FNCP exhibits the highest capacity among three samples but an inferior cycling stability. As contrast, the FNCO shows a balanced characteristic of good capacity and superior cycling performance. Based on the understanding, we construct FNCA//Zn batteries. As expected, the FNCP//Zn batteries delivers the highest specific capacity of 318 mAh g−1 and a superior energy density of 532.7 Wh kg−1 at a power density of 1.673 kW kg−1, but an inferior cycling stability reserved from the individual FNCP electrode. This work provides a rational insight for deep understanding the behaviors that anions affect electrochemical energy storage but not participate in redox reactions, and offer more effective feasibility to design high capacity and durable cathode materials for aqueous Zn-based batteries.