Hydrogen‐Bond‐Stabilized Organic Potassium‐Ion Full Cell Operating at −40°C

Abstract Low‐temperature energy storage systems confront severe operational constraints due to sluggish ion kinetics and electrolyte solidification. While potassium‐ion batteries (PIBs) offer potential for low‐cost energy storage, the absence of viable cathode materials with adequate stability at ultra‐low temperatures remains a critical barrier. Herein, we demonstrate an organic small molecule, 1,4‐dihydrobenzo[g]quinoxaline‐2,3,5,10‐tetraone (BQXTO), in which intermolecular hydrogen bonds (HB) and robust π─π interactions synergistically enhance charge transfer and impart insolubility, thereby facilitating reaction kinetics and improving cycling stability even under low‐temperature conditions. The assembled BQXTO||HC potassium‐ion full cell achieves remarkable energy density at −40 °C (188 Wh kg −1 ) and exceptional cyclability (88.2% capacity retention over 2000 cycles). This study presents valuable insights into the structure design of organic small molecule cathodes for advanced low‐temperature PIBs.