Jahn-Teller Distortion Induced Mn²⁺-Rich Cathode Enables Optimal Flexible Aqueous High-Voltage Zn-Mn Batteries

Although one of the most promising aqueous batteries, all Zn-Mn systems suffer from Zn dendrites and the low-capacity Mn⁴⁺/Mn³⁺ process (readily leading to the occurrence of Jahn-Teller distortion, which in turn causes structural collapse and voltage/capacity fading). Here, the Mn³⁺ reconstruction and disproportionation are exploited to prepare the stable, Mn²⁺-rich manganese oxides on carbon-cloth (CMOs) in a discharged state through an inverted design, which promotes reversible Mn²⁺/Mn⁴⁺ kinetics and mitigates oxygen-related redox activity. Such a 1.65 V Mn²⁺-rich cathode enable constructing a 2.2 V Zn-Mn battery, providing a high area capacity of 4.16 mA h cm^-2 (25 mA h cm^-2 for 10 mL electrolyte) and superior 4000-cycle stability. Moreover, a flexible hybrid 2.7 V Zn-Mn battery is constructed using 2-pH hydrogel electrolytes to demonstrate excellent practicality and stability. A further insight has been gained to the commercial application of aqueous energy storage devices toward low-cost, high safety, and excellent energy density.