Gel polymer electrolyte with MXene to extend cycle lifespan of flexible and rechargeable Zinc–Air batteries

Flexible and rechargeable zinc–air batteries (ZABs) are promising energy sources for wearable electronic devices due to their high energy density and safe operation. However, the performance of quasi-solid-state electrolytes gradually degrades during the ion-exchange process, mainly because of water evaporation on the open cathode side, which reduces the lifespan of ZABs. Thus, a novel electrolyte needs to be designed that can retain water to increase the cycle lifespan of ZABs. Herein, we propose a near-neutral gel polymer electrolyte (GPE) composite comprising polyvinyl alcohol (PVA) and hydroxy-functionalized MXene. Benefiting from the three-dimensional porous network and numerous surface-functionalized hydroxy groups, the network of alkalized MXene inside the PVA matrix serves as a water reservoir, resulting in enhanced water retention, and therefore, a high ionic conductivity of 77.6 mS cm−1. The molecular dynamic simulations validate stronger hydrophilicity of alkalized MXene surface for water molecular than the pristine MXene. Resultantly, the assembled ZABs show a long cycle lifespan of 160 h at a current density of 2 mA cm−2 and a charging–discharging period of 15 min.