Entropy-Driven Solvation Manipulation Enables Reversible and Stable K-Storage for Sb-Based Anodes

To develop advanced electrolytes for potassium-ion batteries (PIBs) with high energy density and long cycle life, a comprehensive balance design between thermodynamic stability and ion transport kinetics is highly required, but this still remains a critical challenge. Herein, an entropy-driven solvation manipulation strategy was proposed to develop a linear ether-based medium-entropy electrolyte (MSE) for a K-storage alloy anode of antimony/super P (Sb/SP). The dual entropy and weak solvation effects during the design of multicomponent ethers-based electrolytes enabled the MSE balanced solvation structures of solvent-separated ion pairs (SSIPs) and contact ion pairs (CIPs) with enhanced ionic conductivity and decreased desolvation energy barrier (Edes), thus guaranteeing K-storage stability and kinetics for the Sb/SP anode simultaneously. As a result, the Sb/SP anode in the MSE delivered a highly maintained specific capacity of 460 mAh/g after 500 cycles at 50 mA/g. More notably, paired with a Prussian blue (PB) cathode, the built full cell of PB||MSE||Sb/SP achieved a high energy density of 194 Wh/kg calculated based on the total active mass of cathode/anode, suggesting the practical application potential of entropy-driven electrolytes in energy storage devices. This work provides new insights into developing high-performance electrolytes through entropy engineering, offering a promising direction for next-generation energy storage technologies.