Zinc-ion rechargeable battery (ZIRB) is a promising candidate for future energy storage systems due to its cost-effectiveness, operational safety, and environmental friendliness. However, the commercial-scale application of ZIRB is hindered by its insufficient energy efficiency, poor rate capability, and inferior cycling stability. Here, we introduce a gel biopolymer electrolyte (GBE) empowered Zn/K dual-ion battery with exceptional cycling and rate performance. Calling for sustainability, this cellulose-encapsulated bisalt electrolyte presents strong mechanical robustness that inhibits Zn dendrite growth and promotes anodic plating/stripping reversibility. Sandwiching the GBE between a potassium manganese hexacyanoferrate (KMnHCF) cathode and a Zn anode, the coin-cell configuration of KMnHCF|GBE|Zn demonstrates a high voltage discharge plateau of 1.80 V, an initial capacity of up to 65 mAh g−1, and excellent cycling stability with capacity retention of 92 % after 1,000 cycles. Furthermore, the superior durability, flexibility, safety, and endurance with extreme conditions (e.g., bending, puncturing, and cutting) demonstrated by KMnHCF|GBE|Zn pouch-cell enables its future application in wearable electronics.