Suppressing side reactions in spinel ZnMn2O4 for high-performance aqueous zinc-ion batteries

Although the spinel ZnMn2O4 is regarded as a cathode with high structural stability for rechargeable aqueous zinc-ion batteries, its unsatisfied charge storage capacity seriously restricts its practical applications. Herein, we propose an electrolyte modification strategy to suppress side reactions of the ZnMn2O4 electrode and improve its charge storage performance. Specifically, dimethyl sulfoxide (50 %) (50-DMSO) is added to a pure ZnSO4 electrolyte to inhibit the oxygen evolution reaction at the cathode, which lifts the charge cutoff voltage and helps to fully utilize the theoretical capacity of ZnMn2O4. Moreover, the introduction of 0.1 M H2SO4 into the 50DMSO electrolyte (50-DMSO+0.1) increases the conductivity of the electrolyte from 22.5 mS cm- 1 to 50.6 mS cm- 1 and eliminates the Zn4SO4(OH)6 & sdot;xH2O by-product. Benefiting from these electrolyte modifications, the ZnMn2O4 cathode in a 50-DMSO+0.1 electrolyte delivers a large specific capacity of 207 mAh g-1 at 0.1 A g with excellent cycling performance (84 % capacity retention after 3500 cycles) and rate capability (125 mAh g at 1.0 A g- 1 ). This work demonstrates the importance of suppressing side reactions of cathode materials and provides an effective electrolyte modification strategy to develop high-performance zinc-ion batteries.