Enhancing Zn Metal Anode Stability via Ti₃C₂T_x MXene/PEI Composite Coating

Aqueous Zn-ion batteries (AZIBs) are considered a promising candidate for large-scale energy storage application owing to their high capacity, good safety, low cost, and environmental friendliness. However, the presence of active water leads to issues such as corrosion, dendrite growth and hydrogen evolution reaction on Zn metal anodes, severely limiting the cycle lifetime and reversibility of AZIBs. To address these challenges, this study introduces a simple drop-casting method to deposit a composite protective coating of 2D titanium carbide (Ti₃C₂T_x) MXene and polyethyleneimine (PEI) on the surface of Zn foil, i.e., MXene/PEI@Zn. The MXene/PEI composite coating contains polar groups such as -OH that can regulate Zn deposition. Additionally, these groups prevent active water from directly contacting the Zn metal surface. The results show that the MXene/PEI@Zn anodes can cycle for over 2600 and 1100 h at the corresponding current density of 1 and 5 mA cm^-2 (Areal capacity: 1 mAh cm^-2). When paired with a V₂O₅·1.6H₂O cathode, it contributes to the evidently improved full-cell performance with 85% capacity retention after 4800 cycles at 5 A g^-1. This work provides new insights into the practical design of highly reversible Zn metal anodes.