Synergistic Coupling of Sulfide Electrolyte and Integrated 3D FeS₂ Electrode Toward Long-Cycling All-Solid-State Lithium Batteries

FeS₂ cathode is promising for all-solid-state lithium batteries due to its ultra-high capacity, low cost, and environmental friendliness. However, the poor performances, induced by limited electrode-electrolyte interface, severe volume expansion, and polysulfide shuttle, hinder the application of FeS₂ in all-solid-state lithium batteries. Herein, an integrated 3D FeS₂ electrode with full infiltration of Li₆PS₅Cl sulfide electrolytes is designed to address these challenges. Such a 3D integrated design not only achieves intimate and maximized interfacial contact between electrode and sulfide electrolytes, but also effectively buffers the inner volume change of FeS₂ and completely eliminates the polysulfide shuttle through direct solid–solid conversion of Li₂S/S. Besides, the vertical 3D arrays guarantee direct electron transport channels and horizontally shortened ion diffusion paths, endowing the integrated electrode with a remarkably reduced interfacial impedance and enhanced reaction kinetics. Benefiting from these synergies, the integrated all-solid-state lithium battery exhibits the largest reversible capacity (667 mAh g⁻¹), best rate performance, and highest capacity retention of 82% over 500 cycles at 0.1 C compared to both a liquid battery and non-integrated all-solid-state lithium battery. The cycling performance is among the best reported for FeS₂-based all-solid-state lithium batteries. This work presents an innovative synergistic strategy for designing long-cycling high-energy all-solid-state lithium batteries, which can be readily applied to other battery systems, such as lithium-sulfur batteries.