Sulfur‑Containing Additives for Enhanced Kinetics and Interfacial Stability of Phosphorus Anodes in Li‑Ion Batteries

Red phosphorus offers ultrahigh theoretical capacity for lithium-ion battery anodes but is fundamentally limited by poor electronic conductivity, sluggish lithium-ion diffusion, and severe volume expansion that destabilizes the solid-electrolyte interphase. Here, we introduce a synergistic strategy that simultaneously regulates reaction kinetics and interfacial stability using sulfur-containing additives, lithium sulfide, and in situ generated lithium sulfate. Lithium sulfide confines lithium polyphosphide intermediates, enabling a direct and highly reversible conversion reaction, while lithium sulfate selectively absorbs solvent molecules and directs the formation of a uniform, lithium-oxide-dominated and mechanically adaptive interphase. Through this cooperative modulation, reaction kinetics are accelerated, structural integrity is preserved during cycling, and interfacial failure is effectively suppressed. As a result, the optimized red phosphorus anode retains 96.1% and 94.1% of its capacity after 450 and 1000 cycles at 1 and 4 C respectively, and still maintains 80% capacity retention after 1200 cycles at 6 C. This dual-functional strategy establishes a coherent design principle for durable, high-capacity conversion-type anodes.