Ultra-High Zinc Utilization Enabled by MXene Anode for Flexible Dual-Plating Zn–Br2 Microbatteries

Abstract

Aqueous zinc-ion microbatteries exhibit promising prospects for wearable devices due to their high safety and cost-effectiveness but face challenges such as low energy density and short cycle life. To address these challenges, a dual-plating flexible Zn–Br₂ microbattery was developed using freestanding MXene films as a zinc metal free anode. The MXene anode retains no redundant Zn, as Zn²⁺ from the electrolyte undergoes deposition/stripping reactions on its substrate, thereby eliminating the necessity for excess zinc. Compared to Zn anode, it exhibits significantly reduced mass while achieving enhanced depth of discharge and markedly ultrahigh zinc utilization efficiency. The MXene anode can in situ form a ZnF₂-rich layer and exhibits low solvation energy, excellent hydrophilicity, and mechanical properties. Leveraging these properties, the MXene anode demonstrates low nucleation overpotential (2.8 mV) and remarkable cycling stability (970 h). More importantly, assembled Zn–Br₂ microbatteries show 6000-cycle stability, flexibility, high energy density, and advance wearable energy storage.