Dual electrode‐free Zn‐ <scp> MnO ₂ </scp> battery as a future energy source

Abstract Aqueous rechargeable Zn‐MnO 2 batteries are considered one of the most promising energy storage systems and have been extensively studied in recent years, owing to their high energy density, low cost, and intrinsic safety. However, the practical application of conventional Zn‐MnO 2 batteries is hindered by poor cycling stability, corrosion, and unwanted side reactions. Recently, dual electrode‐free Zn‐MnO 2 batteries have emerged as a promising alternative. Their simplified battery configurations and lightweight design, achieved by eliminating the need for pre‐fabricated bulk electrodes, offer higher energy density. Nevertheless, such designs can, in principle, suffer from limited cycle life due to the poor reversibility of the Zn‐MnO 2 deposition/stripping process. This review critically examines recent advances aimed at overcoming these challenges, highlighting the transition from conventional to anode‐free, cathode‐free, and ultimately dual electrode‐free configurations. We also present key strategies including electrolyte engineering, current collector modification via 3D printing, and interfacial engineering to enable stable long‐term cycling, along with insights from advanced in situ characterization techniques such as electrochemical quartz crystal microbalance (EQCM) and optical microscopy. Finally, we outline future opportunities required to advance this promising field toward practical applications. image