Synergy Between Weak Solvent and Solid Electrolyte Interphase Enables High‐rate and Temperature‐resilient Potassium Ion Batteries

The rate and wide‐temperature performance of graphite‐based potassium ion batteries (PIBs) are limited by slow reaction kinetics at the interphases and the solid electrolyte interphase (SEI) stability. Herein, we strategically designed weak solvating electrolytes (WSEs) to construct an efficient solvated K+ desolvation with K2SO3‐rich SEI and achieve fast reaction kinetics at the electrode interface through the synergy between the SEI and the WSE. As a result of the beneficial fast reaction kinetics and stability of the electrode interface, the graphite anode shows high levels of rate performance and cycling stability, with a capacity of 249.6 mAh g−1 at 500 mA g−1 and 96.6% capacity retention after 1600 cycles. Moreover, assembled potassiated graphite (KC8)||Prussian blue nanoparticles (K‐PBNPs) cells in our designed electrolyte show high‐rate performance (63.1 mAh g−1 at 1500 mA g−1) and over wide operating temperature range (> 99% Coulombic efficiency for over 1000 cycles and 200 cycles at −20 °C and 80 °C, respectively). Impressively, the pouch cell shows long‐term stability for 2400 cycles at 500 mAg−1. This work bridges a longstanding gap elucidating the synergy between the SEI components and WSEs, leading to fast‐charging and temperature‐resilient PIBs.