Dynamic compensation of MnOOH to mitigate the irregular dissolution of MnO2 in rechargeable aqueous Zn/MnO2 batteries

Abstract

As a recognized promising cathode material for rechargeable aqueous Zn batteries, an MnO₂ cathode often suffers from rapid fading of capacity due to irreversible Mn dissolution, which hinders high-performance Zn batteries. Herein, we introduced Ce(SO₄)₂ additives into the electrolyte of Zn/MnO₂ batteries to cope with the irreversible dissolution of MnO₂. During charging, the MnOOH formed by the reaction between Ce⁴⁺ and Mn²⁺ deposited on the cathode with the attraction of H⁺ and was converted subsequently to MnO₂ to achieve dynamic compensation. Meanwhile, MnOOH was generated from the transformation of MnO₂ during discharge, and the reaction between Ce³⁺ and MnOOH was beneficial for the reversibility of Ce⁴⁺, but also competitive with the disproportionation of MnOOH. As a result, Zn/MnO₂ batteries with Ce(SO₄)₂ additives showed high capacity retention of 97.4% at 1.0 A g⁻¹ after 1000 cycles, which far exceeded that of the batteries without Ce(SO₄)₂ (40.5%).