OH-BNNSs reinforced polyvinyl alcohol/ carboxymethyl cellulose-based deep eutectic gel electrolyte for rechargeable zinc-air batteries

As an important component of flexible Zinc-air batteries (ZAB), the gel electrolyte has a direct impact on battery performances and applications. Polyvinyl alcohol (PVA) is a commonly used electrolyte matrix material in ZAB, which has film-forming and environment-friendly, but poor mechanical properties and ionic conductivity limit its application in flexible ZAB. As a new type of environment-friendly solvent, deep eutectic solvent (DES) not only has the extremely low volatility, excellent electrochemical stability and excellent thermal stability, but also has the advantages of low cost and stable performances. Hydroxy-boron nitride nanosheets (OH-BNNSs) are obtained by grafting hydroxyl groups onto boron nitride nanosheets. In this paper, PVA was modified by carboxymethyl cellulose (CMC) firstly. After adding DES and OH-BNNSs, the deep eutectic gel electrolyte was obtained by cryogenic freezing. The optimized system containing 50 wt% DES and 1 wt% OH-BNNSs demonstrated remarkable enhancements. Ionic conductivity increased to 137.61 mS·cm −1 , representing a 1.86-fold improvement over conventional PVA-based electrolytes. Electrolyte uptake rate reached 183.5% with 88.7% retention rate after 12 h, achieving 2.03-fold and 1.92-fold of the performance of PVA, respectively. Mechanical properties showed substantial gains, with elongation at break escalating to 586% (3.66 times better than PVA) and tensile strength registering 0.55 MPa. When implemented in ZAB, power density peaked at 35.3 mW·cm −2 , surpassing pure PVA by 4.53-fold. Cycling stability exhibited prolonged durability, sustaining 110 cycles over 36.7 h at 1 mA·cm −2 . Single discharge duration attained 10.7 h. Our paper provides design scheme and theoretical references for application and progress of flexible devices.