Flexible quasi-solid-state zinc ion batteries enabled by highly conductive carrageenan bio-polymer electrolyte

Flexible Zn–MnO2 batteries as wearable electronic power source have attracted much attention in recent years due to their low cost and high safety. To promote the practical application of flexible Zn–MnO2 batteries, it is imperative to develop flexible, mechanically robust and high performance solid state electrolyte. Herein, we construct a rechargeable quasi-solid-state zinc ion battery using kappa-carrageenan bio-polymer electrolyte. The kappa-carrageenan electrolyte is eco-friendly, low cost, and highly conductive (3.32 × 10−2 S cm−1 at room temperature). The mechanical robustness of kappa-carrageenan electrolyte is further reinforced by using a rice paper as scaffold. Benefiting from high ionic conductivity of the bio-polymer electrolyte, our zinc ion battery delivers a significant high energy density and power density (400 W h kg−1 and 7.9 kW kg−1, respectively), high specific capacity (291.5 mA h g−1 at 0.15 A g−1), fast charging and discharging capability (120.0 mA h g−1 at 6.0 A g−1). The zinc ion battery with bio-polymer electrolyte also shows excellent cycling stability and high bending durability. This work brings new research opportunities in developing low-cost flexible solid-state zinc ion batteries using green natural polymer.