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

FeS 2 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 FeS 2 in all‐solid‐state lithium batteries. Herein, an integrated 3D FeS 2 electrode with full infiltration of Li 6 PS 5 Cl 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 FeS 2 and completely eliminates the polysulfide shuttle through direct solid–solid conversion of Li 2 S/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 FeS 2 ‐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.