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

Abstract

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 (LiPO₂F₂/FEC/VC) are used to optimize the electrode interface, forming a LiF/Li₂CO₃ 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.