Enhancing Electrochemical Performance of Layered Birnessite Materials with Metal Ions Intercalated Cation for Aqueous Zinc-Ion Batteries

Abstract

Recently, rechargeable aqueous-based batteries become promising candidates owing to their cost-effectiveness, environmental friendliness, and high safety. Furthermore, aqueous electrolytes provide high ionic conductivity and also provide facile manufacturing processes. Among all rechargeable aqueous-based batteries, aqueous Zn-based batteries (AZBs) exhibit low redox potential (-0.76 V vs standard hydrogen electrode (SHE)) and high theoretical capacity of the Zn metal anode (840 mAh g-1), leading to superior energy density as compared to other low-cost batteries. However, there are many challenges remaining for AZBs including the cathode dissolution limiting their practical applications. Manganese-based oxides are promising cathode materials for AZBs due to their low cost and low toxicity. Moreover, there are various valence states of manganese (Mn2+, Mn3+, Mn4+, and Mn7+) and different crystallographic structures, including ɑ-, β-, γ-, δ-, and λ-MnO2. According to promising manganese-based oxides, δ-MnO2 is one of the most interesting materials because it exhibits a high theoretical capacity of about 616 mAh g-1. Also, the δ-MnO2 or layered structure provides a facile Zn2+ insertion, leading to high-rate capability. However, this structure is facing collapse issue during cycling, resulting in poor stability. In this work, we demonstrate the facile synthesis method of δ-MnO2 and investigate the effect of intercalated cations on its electrochemical performance towards AZBs. The as-fabricated Zn-MnO2 battery achieves 200 mAh g-1 at 0.1 A g-1 and high stability up to 68% after 200 cycles at 1 A g-1.