Interfacial Solvent Molecular Engineering via High‐Safety Dense Separators for High‐Rate Lithium‐Ion Batteries

To address the conflicting challenges of energy density, rate performance, and safety in lithium metal batteries and self‐generated lithium metal anodes, we propose a synergistic optimization strategy that employs a high‐density polyphenylene sulfide (PPS‐separator) and a dimethyl carbonate‐based electrolyte. Density functional theory calculations and experiments demonstrate that due to its weak polyphenylene sulfide adsorption energy (−0.3261 eV) and small molecular size, the dimethyl carbonate solvent can construct efficient ion hopping channels at the polyphenylene sulfide crystal interface, achieving a room‐temperature ionic conductivity of 1.02 × 10 −3 S cm −1 (3.5 times that of conventional ceramic separators). Functional additives (LiPO 2 F 2 /FEC/VC) are used to optimize the electrode interface, forming a LiF/Li 2 CO 3 dual‐phase composite SEI, which drives uniform two‐dimensional lithium metal deposition and reduces interfacial impedance. The system has been stably cycled 435 cycles under extreme conditions, maintaining a capacity retention of over 80%. The intrinsic flame retardancy of polyphenylene sulfide‐separator, coupled with its minimal electrolyte requirements, facilitates electrolyte vaporization‐induced self‐blocking of ion channels during nail penetration tests. This effectively suppresses thermal runaway in 6‐Ah high‐nickel NCM811/SiC pouch cells, keeping peak temperatures below 50 °C and offering a novel approach to resolving the trade‐off between high energy density and high safety.