Effect of MnSO₄ concentration on the electrochemical performance of β-MnO₂/3D graphene-carbon nanotube hybrids cathode for aqueous zinc-ion batteries

Manganese-based cathode material has a wide range of applications in aqueous zinc-ion batteries, but its structural stability is poor. We can improve the microstructure of manganese-based cathode materials by simple mechanical ball milling methods, thus increasing the discharge capacity of batteries. However, the capacity of manganese-based cathode material batteries decreases rapidly during cycling, which is caused by the dissolution of manganese-based materials in the electrolyte. To ameliorate this problem, in this work, MnSO₄ is pre-added to the ZnSO₄ electrolyte, which can effectively inhibit the dissolution of the manganese-based material and maintain the conversion reaction inside the battery, providing better cycle life and higher discharge capacity. In addition, with the increase of MnSO₄ additive concentration in a certain range, the discharge capacity and cycle life of the batteries were improved (the battery pre-added with 0.5 M MnSO₄ solution had the highest reversible specific capacity of up to 521.91 mAh·g⁻¹ at a current density of 100 mA·g⁻¹ and 109.12 mAh·g⁻¹ even at 1 A·g⁻¹, the capacity retention rate remained at 83.8% after cycling for more than 8000 cycles), which provides an idea for the electrolyte regulation of aqueous zinc-ion batteries.