Entropy-Repaired Solvation Structure Strategy for High-Efficiency Phosphate-Based Localized High-Concentration Electrolytes in Potassium Batteries.

The safety and cycling stability of potassium-ion batteries (PIBs) are deeply associated with potassium-ion electrolytes. However, due to the weak Lewis acidity of potassium ions, localized high-concentration electrolytes in PIBs are prone to excessive weak solvation. Herein, we propose an entropy repair strategy for the solvation structure of potassium ions and systematically design a moderately weakly solvated high-entropy localized high-concentration electrolyte. The repaired electrolyte can achieve an average stable Coulombic efficiency of 99.4% on the Cu collector surface. The potassium symmetric battery can be stably cycled for over 10000 h under a high current density of 0.5 mA cm-2 and a large deposition capacity of 1 mAh cm-2. The potassium metal pouch cell, using K1.92Fe[Fe(CN)6]0.94∙0.5H2O as the cathode, maintains a capacity retention of 87.5% after 2000 cycles at a current density of 0.5 A g-1. Even when the current density is increased tenfold from 0.1 A g-1, the battery still retains 67.1% of its capacity. Additionally, due to the introduction of multiple solvents, the potassium metal battery with perylene-3,4,9,10-tetracarboxylic dianhydride as the cathode can maintain reversible capacities of 94.0 and 77.3 mAh g-1 and operate stably at ambient temperatures of -20 and -40 ℃, respectively.