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[Display omitted] • Novel double-network crosslinks from electrolyte affinity materials through phase separation. • H-bond sacrifice via free radical-polymerized cellulose network for structure stability. • 3D porous structure and polar functional groups facilitating ion transport and transfer. • Lower free water binding with Zn2+ for uniform Zn2+ flux to suppress zinc dendrite growth. • 87.8 % capacity retention from 200 mA g−1 to 3000 mA g−1 and high capacity retention of 90.6 % after 800 cycles. Aqueous K/Zn dual-ion battery combines swift diffusion of potassium with the advantageous properties of zinc, resulting in increased operational voltage and energy density. However, the limited electrochemical window of the aqueous electrolyte makes it susceptible to unwanted side reactions and dendrite formation. To tackle this challenge, we employed a synergy of H-bonding and polymerization to craft a double-network semi-solid electrolyte. This innovative architecture markedly bolstered structural integrity, while incorporation of polar groups within matrix and network enhanced electrolyte absorption and ion conductivity. Furthermore, –COO− groups interacted with Zn2+, affording stabilization for zinc deposition. The Zn//Zn cell exhibited an impressive cycling life of 800 h at 0.5 mA cm−2 and low water content within electrolyte effectively mitigated side reactions, thereby broadening voltage window. Additionally, a ZnHCF//Zn cell demonstrated a substantial discharge plateau of 1.8 V, an outstanding reversible capacity of 62.2 mAh g−1, remarkable capacity retention at 90.6 % after 800 cycles. Moreover, it boasted a remarkable energy density of 107.7 Wh kg−1 and a high-power density of 5.1 kW kg−1. This pioneering double-network semi-solid electrolyte not only provides a breakthrough method to circumvent dendrite formation but also establishes a robust foundation for advancing high- performance K/Zn dual-ion batteries. [ABSTRACT FROM AUTHOR]