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

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 Ti₃C₂ 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 PF₆ ^- 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 Ti₃C₂ 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.