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

Abstract

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 50-DMSO 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·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^-1 with excellent cycling performance (84% capacity retention after 3500 cycles) and rate capability (125 mAh g⁻¹ 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.