Air‐Stable Li<sub>2</sub>S Cathodes Enabled by an In Situ‐Formed Li<sup>+</sup> Conductor for Graphite‐Li<sub>2</sub>S Pouch Cells
Xiaoqun Qi, Xiaoyu Jin, Henghui Xu, Yujun Pan, Fengyi Yang, Zhenglu Zhu, Jie Ji, Ruining Jiang, Haoran Du, Yongsheng Ji, Dan Yang, Long Qie, Yunhui Huang
Abstract
Abstract Using Li 2 S cathodes instead of S cathodes presents an opportunity to pair them with Li‐free anodes (e.g., graphite), thereby circumventing anode‐related issues, such as poor reversibility and safety, encountered in Li‐S batteries. However, the moisture‐sensitive nature of Li 2 S causes the release of hazardous H 2 S and the formation of insulative by‐products, increasing the manufacturing difficulty and adversely affecting cathode performance. Here, Li 4 SnS 4 , a Li + conductor that is air‐stable according to the hard–soft acid–base principle, is formed in situ and uniformly on Li 2 S particles because Li 2 S itself participates in Li 4 SnS 4 formation. When exposed to air (20% relative humidity), the protective Li 4 SnS 4 layer maintains its components and structure, thus contributing to the enhanced stability of the Li 2 S@Li 4 SnS 4 composite. In addition, the Li 4 SnS 4 layer can accelerate the sluggish conversion of Li 2 S because of its favorable interfacial charge transfer, and continuously confine lithium polysulfides owing to its integrity during electrochemical processes. A graphite‐Li 2 S pouch cell containing a Li 2 S@Li 4 SnS 4 cathode is constructed, which shows stable cyclability with 97% capacity retention after 100 cycles. Hence, combining a desirable air‐stable Li 2 S cathode and a highly reversible Li‐free configuration offers potential practical applications of graphite‐Li 2 S full cells.