A Triple‐Modulator Electrolyte Enables Aqueous Potassium‐Ion Batteries Operating Down to –40°C

ABSTRACT The low‑temperature application of aqueous potassium‑ion batteries is strictly limited by electrolyte freezing and unstable electrode/electrolyte interfaces. To address these challenges simultaneously, we propose a triple‑modulator electrolyte engineering strategy that introduces diethyl phosphoramidate (DEPA) as a molecular triple modulator. DEPA operates through three interconnected mechanisms. First, its ─NH 2 and ─P═O functional groups act as potent hydrogen‐bond disruptors that effectively dismantle the intrinsic tetrahedral ordering of water networks, thereby lowering the electrolyte freezing point to −40°C. Second, it actively participates in the K + solvation sheath and loosens the coordination environment, thereby lowering the desolvation energy barrier. Third, it guides the in‐situ formation of a robust, inorganic‐rich solid electrolyte interphase featuring a highly homogeneous organic‐inorganic hybrid architecture. The optimized electrolyte endows the full cell with exceptionally low‑temperature performance, delivering an initial reversible capacity of 63.1 mAh g −1 at 10 mA g −1 at −40°C. Moreover, a pouch cell with this electrolyte retains 83.2% of its initial capacity after 70 cycles at −40°C, demonstrating clear practical application potential. This work achieves synergistic “bulk‑interface” optimization through the rational design of intermolecular interactions, providing a viable molecular engineering paradigm for the development of low‐temperature‐tolerant aqueous batteries.