A high-energy-density aqueous zinc–manganese battery with a La–Ca co-doped ε-MnO2 cathode

Abstract

Aqueous zinc–manganese dioxide batteries (Zn//MnO₂) are gaining considerable research attention for energy storage taking advantage of their low cost and high safety. However, the capacity and cycling stability of the state-of-the-art devices are still utterly disappointing because of the inevitable MnO₂ dissolution and its low conductivity. In this work, to elevate the energy density of Zn//MnO₂, a La–Ca co-doping strategy is proposed to boost the electrochemical performance of the ε-MnO₂ cathode. Specifically, the introduction of heteroatoms, La³⁺ and Ca²⁺, is achieved via a facile one-step liquid coprecipitation method. Our experimental results reveal that Ca²⁺ significantly improves the stability of ε-MnO₂ while Ca²⁺ and La³⁺ both contribute to the capacity and reversibility enhancement. Therefore, the overall performance of the La–Ca co-doped ε-MnO₂ cathode exceeds the pristine sample, as demonstrated by its commendable capacity of 297.3 mA h g⁻¹ at 0.2 A g⁻¹, superior cycle stability (up to 76.8% capacity retention after 200 cycles) and excellent rate capability (161 mA h g⁻¹ when the current density increased to 1.6 A g⁻¹). Besides, the assembled Zn//ε-MnO₂ device delivers a maximum energy and power density of 401.22 W h kg⁻¹ and 5.2 kW kg⁻¹ respectively, outperforming most of the recently reported Zn//MnO₂ counterparts.