An Electron/Ion Dual Conductive Integrated Cathode Using Cationic/Anionic Redox for High‐Energy‐Density All‐Solid‐State Lithium‐Sulfur Batteries

Abstract All‐solid‐state lithium‐sulfur batteries (ASSLSB), composed of sulfur cathode and lithium metal anode with high theoretical capacity, have a potentially higher energy density by weight than a typical lithium‐ion battery (LIB). However, due to insulating sulfur, a relatively large proportion of electronic (carbon) and ionic (solid electrolyte) conductors are mixed for cathode fabrication, leading to inferior practical capacity. Herein, we report a novel integrated cathode Li₂S‐LiI‐MoS₂ which has relatively high electronic and ionic conductivities (the order of 10⁻⁴ S cm⁻¹) without any carbon and solid electrolyte. The ASSLSB with integrated Li₂S‐LiI‐MoS₂ cathode delivers a remarkably high energy density of 1020 Wh kg⁻¹ at the cathode level at room temperature. By applying precise X‐ray diffraction, pair distribution function analysis and X‐ray computed tomography, it is found that the formation of an ionic conducting phase composed mainly of LiI during discharge is responsible for the high rate capability. Furthermore, X‐ray absorption fine structure (XAFS) has also revealed the charge compensation mechanism and ascertained the involvement of both Mo 3d and S 3p orbitals during the charging and discharging process. It is believed the strategy will pave the way for developing high practical energy density at room temperature for all‐solid‐state batteries.