Ti4O7 regulating both Zn(OH)42– and electrons for improving Zn–Ni batteries

Abstract

Zn–Ni battery is prospective green energy storage device. However, Zn(OH)42–, the dissolved product of ZnO in the electrolyte, redistributes during the cycle, leading to the shape changing of the anode. This issue severely limits the lifespan of zinc anodes. Despite the success in improving the electrochemical performances of zinc anode via adding Ti4O7 additive, the important mechanism of such modified anode has not been well understood. In addition, the aluminothermic reduction is facile and energy-saving. But the application of Ti4O7 synthesized by this method in Zn–Ni batteries has not been studied. Herein, Ti4O7 synthesized by facile and rapid aluminothermic reduction was applied to alkaline zinc anode. In subsequent electrochemical tests, the discharge capacity and cyclic performance of the zinc-nickel battery was significantly improved by adding as-prepared Ti4O7 particles. At a high discharge current of 2.5 A (34.54 mA cm−2), the anode modified by Ti4O7 delivered higher discharge capacity of 364 mAh g−1, in contrast to the 283 mAh g−1 of pristine anode. Even at ultra-high discharge current of 10 A (138.16 mA cm−2), the battery operated stably for 480 cycles. Besides, the mechanism of Ti4O7 modifying anode was studied in-depth by a variety of characterizations and density functional theory (DFT) calculations. We discovered that Ti4O7 simultaneously regulates the distribution of electrons on the anode and Zn(OH)42– in the electrolyte, contributing to forming uniform zinc anode during cycling.