Flexible Hydrogel Electrolyte with Superior Mechanical Properties Based on Poly(vinyl alcohol) and Bacterial Cellulose for the Solid-State Zinc-Air Batteries

Flexible solid-state zinc-air batteries are promising energy technologies with low cost, superior performance and safety. However, flexible electrolytes are severely limited by their poor mechanical properties. Here, we introduce flexible bacterial cellulose (BC)/poly(vinyl alcohol) (PVA) composite hydrogel electrolytes (BPCE) based on bacterial cellulose (BC) microfibers and poly(vinyl alcohol) (PVA) by an in situ synthesis. Originating from the hydrogen bonds among BC microfibers and PVA matrix, these composites form load-bearing percolating dual network and their mechanical strength is increased 9 times (from 0.102 MPa of pristine PVA to 0.951 MPa of 6-BPCE). 6-BPCE shows extremely high ionic conductivities (80.8 mS cm^-1). In addition, the solid-state zinc-air batteries can stably cycle over 440 h without large discharge and charge polarizations equipped with zinc anode and Co₃O₄@Ni cathode. Moreover, flexible solid-state zinc-air batteries can cycle well at any bending angle. As flexible electrolytes, they open up a new opportunity for the development of superior-performance, flexible, rechargeable, zinc-air batteries.