Zinc-rich cathode material ZnMn2O4 for high-voltage zinc ion batteries

Abstract

Currently, the cathode material of aqueous zinc-ion batteries (AZIBs) encounters difficulties in providing an adequate supply of Zn²⁺. This situation renders the battery highly reliant on the zinc metal anode for Zn²⁺ supply, consequently leading to safety concerns such as severe dendrites. Zincrich cathode materials have attracted attention because their zinc content actively participates in electrochemical reactions for energy storage. Spinel ZnMn₂O₄ (ZMO) is a promising candidate owing to its high capacity, suitable redox potential, abundance, and low cost. However, it suffers from large volume changes, poor conductivity, and slow ion diffusion. To address these issues, we synthesized the precursor using a reversed-phase microemulsion method and obtained ZMO via air calcination. By adjusting the dosage of the surfactant cetyltrimethylammonium bromide (CTAB) in the ZMO synthesis precursor and the air calcination temperature, we reduced grain crystallinity, resulting in smaller grains, more active sites, and improved Zn²⁺ intercalation/deintercalation kinetics, thereby enhancing overall zinc storage performance. The optimized sample ZMO-20C-400 has excellent high-voltage stability and exhibits good electrochemical performance within the working voltage range of 0.8-1.8 V, that is, it has a high reversible capacity of 125 mAh g⁻¹ at a current density of 0.1 A g⁻¹.