Chloro‐Functionalized Ether‐Based Electrolyte for High‐Voltage and Stable Potassium‐Ion Batteries

Ether‐based electrolyte is beneficial to obtaining good low‐temperature performance and high ionic conductivity in potassium ion batteries. However, the dilute ether‐based electrolytes usually result in ion‐solvent co‐intercalation of graphite, poor cycling stability, and hard to withstand high voltage cathodes above 4.0 V. To address the aforementioned issues, an electron‐withdrawing group (chloro‐substitution) was introduced to regulate the solid‐electrolyte interphase (SEI) and enhance the oxidative stability of ether‐based electrolytes. The dilute (~0.91 M) chloro‐functionalized ether‐based electrolyte not only facilitates the formation of homogeneous dual halides‐based SEI, but also effectively suppress aluminum corrosion at high voltage. Using this functionalized electrolyte, the K||graphite cell exhibits a stability of 700 cycles, the K||Prussian blue (PB) cell (4.3 V) delivers a stability of 500 cycles, and the PB||graphite full‐cell reveals a long stability of 6000 cycles with a high average Coulombic efficiency of 99.98 %. Additionally, the PB||graphite full‐cell can operate under a wide temperature range from −5 °C to 45 °C. This work highlights the positive impact of electrolyte functionalization on the electrochemical performance, providing a bright future of ether‐based electrolytes application for long‐lasting, wide‐temperature, and high Coulombic efficiency PIBs and beyond. The ether‐based electrolyte functionalized with an electron‐withdrawing group (chloro‐substitution) enabled the formation of a dual halides‐based solid‐electrolyte interphase (SEI), thereby enhancing the cycling stability (6000 cycles), high voltage (4.3 V) performance, and wide temperature operation (−5 °C to 45 °C) of potassium ion batteries.