Electron push–pull engineering enables sustainable, anti-corrosive, and nonflammable phosphate electrolytes for long-lifespan lithium–sulfur batteries

Abstract

Triethyl phosphate (TEP) electrolytes hold significant promise for high-safety lithium metal batteries (LMBs) due to their eco-friendliness and intrinsic nonflammability. However, parasitic reactions with lithium metal, coupled with sluggish reaction kinetics, hinder their practical deployment in LMBs. Hence, we propose a sustainable TEP-based localized high-concentration electrolyte (LHCE) by molecularly regulating the coordination ability and reduction chemistry of anisole diluents, thereby simultaneously overcoming the thermodynamic and kinetic limitations associated with high-concentration electrolytes and conventional LHCEs. The optimized p-methylanisole (pMA) diluent modulates Li–TEP coordination and facilitates anions to enter primary solvation sheath through H^δ+–O^δ− hydrogen-bonding interactions, while the weak ion–dipole interaction between Li⁺ and pMA promotes pMA participation in interfacial reactions and preserves the cation-hopping transport mechanism. This strategy yields robust LiF/Li₂O-rich interphases and accelerates reaction kinetics, enabling lithium metal to achieve a high average coulombic efficiency of 98.7% over 650 cycles and an ultralong-lifespan exceeding 1600 h. When deployed in LMBs paired with 2.5 mAh cm⁻² sulfurized polyacrylonitrile cathodes, the batteries demonstrate an extended lifespan over 600 cycles with an average capacity decay of only 0.03% per cycle. Furthermore, the molecular-level design of diluents is broadly applicable to other alkali–metal batteries, offering a new pathway toward the development of high-energy LMBs.