Reconfiguring Zn-Mn Battery via Controlled Water Nanoconfinement Within Zn-Absence Electrolyte

Zn-Mn batteries are appealing candidates for next-generation stationary storage applications. Mainstream electrolytes use Zn²⁺ ions as major charge carrier while the operating mechanism of Mn-based cathode has been argued to be mostly dominated by proton intercalation/de-intercalation and MnO₂/Mn²⁺ dissolution/deposition, which means that the Zn²⁺ ions may not be essential in electrolyte composition. Herein, we demonstrate a new Zn-Mn battery chemistry with Zn-absence electrolyte (NH₄Ac hybrid electrolyte). The use of Zn-absence electrolyte greatly changes the charge storage mechanism of both cathode and anode. On the anode side, hydrous organic electrolyte with nanoscale water domains within the ethylene glycol matrix expands the electrochemical working window and prevents water decomposition. The Zn plating/stripping is found to be highly reversible and corrosion-free, despite low concentration, due to the gradient solid-electrolyte interphase formation and interfacial alloying reaction. On the cathode side, Mn-based materials undergo the fast Grotthuss intercalation of protons from the hydrolysis of NH₄ ⁺ ions, which benefits the fast charging function. The Zn-Mn batteries with Zn²⁺ absence electrolyte show excellent cycling performance for over 2200 cycles, even outperforming the traditional Zn-Mn battery system. This work provides a new design roadmap for smarter design of aqueous battery.