Unlocking Fast Potassium Ion Kinetics: High‐Rate and Long‐Life Potassium Dual‐Ion Battery for Operation at −60 °C

Abstract Energy storage devices operating at low temperatures are plagued by sluggish kinetics, reduced capacity, and notorious dendritic growth. Herein, novel potassium dual‐ion batteries (PDIBs) capable of superior performance at −60 °C, and fabricated by combining MXenes and polytriphenylamine (PTPAn) as the anode and cathode, respectively, are presented. Additionally, the reason for the anomalous kinetics of K + (faster at low temperature than at room temperature) on the Ti 3 C 2 anode is investigated. Theoretical calculations, crossover experiments, and in situ XRD at room and low temperatures revealed that K + tends to bind with solvent molecules rather than anions at subzero temperatures, which not only inhibits the participation of PF 6 − in the formation of the solid electrolyte interphase (SEI), but also guarantees co‐intercalation behavior and suppresses undesirable K + storage. The advantageous properties at low temperatures endow the Ti 3 C 2 anode with fast K + kinetics to unlock the outstanding performance of PDIB at ultralow temperatures. The PDIBs exhibit superior rate capability and high capacity retention at −40 °C and −60 °C. Impressively, after charging‐discharging for 20,000 cycles at −60 °C, the PDIB retained 86.7 % of its initial capacity. This study reveals the influence of temperatures on MXenes and offers a unique design for dual‐ion batteries operating at ultralow temperatures.