Construction of dicyandiamide-coated manganese dioxide composite and its mechanism for improving zinc storage performance

Abstract

Manganese dioxide (MnO₂) is considered one of the most promising cathode materials for aqueous zinc-ion batteries because of its high theoretical capacity, high working voltage, and environmental friendliness. However, its severe capacity fading is caused by unstable crystal structure and manganese dissolution during discharge. Based on these reasons, dicyandiamide (DCDA) was used to coat α-MnO₂ and the effect mechanism of DCDA on the electrochemical performance of α-MnO₂@DCDA was systematically investigated. The results indicate that the physical confinement function of the DCDA not only improves significantly the structural stability of α-MnO₂ but also inhibits dissolution of manganese during discharge. More importantly, electrostatic interaction between nitrogen atoms in DCDA and cations in electrolyte can inhibit Mn²⁺ dissolution during discharge and promote Mn²⁺ deposition during charging, effectively inhibiting the loss of manganese active material. Compared with unmodified α-MnO₂ cathodes, α-MnO₂@DCDA cathodes exhibit significantly improved cycling stability, with a stable capacity of 102.6 mA·h/g after 1500 cycles at a high current density of 3 A/g, with a capacity retention rate exceeding 60%. This work provides an effective way to achieve stable cycling of MnO₂-based zinc-ion batteries.