Progressive “Layer to Hybrid Spinel/Layer” Phase Evolution with Proton and Zn²⁺ Co-intercalation to Enable High Performance of MnO₂-Based Aqueous Batteries

Abstract

Manganese oxides are promising host materials in rechargeable aqueous batteries due to their low cost and high capacity; however, their practical applications have long been restricted by their sluggish reaction kinetics and poor cycling stability. Herein, the layered K_0.36H_0.26MnO₂·0.28H₂O (K36) with a proton and Zn²⁺ cointercalation mechanism leads to a progressive phase evolution from layer-type K36 to hybrid layer-type K_<i>x</i>H_<i>y</i>Zn_<i>z</i>MnO₂·<i>n</i>H₂O and spinel-type ZnMn₂O₄ nanocrystal after a long-term cycle. Accordingly, K36 shows a high specific capacity (∼329.8 mAh g^-1 at 0.1C), a superior rate performance (∼100.1 mAh g^-1 at 10C), and a remarkable cycling stability (capacity retention of ∼93.4% over 3000 cycles at 4C). This work provides a new viewpoint of enhancing electrode performance via generating hybrid phases under electrochemical driving and will be a benefit to developing the next-generation aqueous batteries.