Flexible and rechargeable Zn–air batteries based on green feedstocks with 75% round-trip efficiency

Here, we report a flexible solid-state Zn–air battery (SZAB) that achieves a record round-trip efficiency of 75%. The major components of the SZAB are based on biomass derivatives. Glucose acts as the carbon source to construct the bifunctional oxygen electrocatalyst. Methylcellulose simultaneously enhances the ionic conductivity and water retention of the gel electrolyte, endowing the SZAB with enhanced flexibility and efficiency.