Methyl Asymmetric Interference‐Enhanced Dipole–Dipole Interaction for High‐Performance Potassium–Graphite Battery Electrolyte Design

Abstract

ABSTRACT Potassium‐ion batteries are the only new alkali metal battery system, apart from lithium‐ion batteries, that can directly use graphite as the anode. However, the development of potassium–graphite batteries has been restricted due to the lack of high‐voltage electrolytes compatible with graphite anodes. To address this issue, a graphite‐compatible high‐voltage electrolyte is designed based on methyl asymmetric interference‐enhanced dipole–dipole interactions. The formulated electrolyte achieves an initial Coulombic efficiency of 86.5% by reducing the desolvation energy of K + ions and forming a sulfur‐rich inorganic solid electrolyte interface. At a low current density of 1 µA cm −2 , the maximum stable electrochemical window of the electrolyte reaches 4.6 V, which is compatible with the currently used Prussian blue analogue cathodes. Notably, the potassium–graphite battery with K 1.92 Fe[Fe(CN) 6 ] 0.94 ·0.5H 2 O as the cathode and untreated graphite as the anode can deliver an energy density of 265.6 Wh kg −1 (based on the total mass of cathode and anode) with a capacity retention of 81.3% after 600 cycles. When K 1.68 Mn[Fe(CN) 6 ] 0.92 ·1.36H 2 O is used as the cathode, the energy density can reach 306.2 Wh kg −1 . A five‐stacked pouch full cell with a capacity of ∼24 mAh can rapidly drive a small motor, demonstrating the application potential of the electrolyte.