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 TiC 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 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 TiC 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.