Investigating the Origin of the Enhanced Sodium Storage Capacity of Transition Metal Sulfide Anodes in Ether‐Based Electrolytes. (24th February 2022)

• Record Type: Journal Article
• Authors: Yin, Xucai; Ren, Yang; Guo, Shu; Sun, Baoyu; Wu, Libin; Du, Chunyu; Wang, Jiajun; Yin, Gepin; Huo, Hua
• Is Part Of: Advanced functional materials. Volume 32:Number 22(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-24
• Subjects: carbonate‐based electrolytes -- ether‐based electrolytes -- excellent electrochemical performance -- porous structures -- sodium‐ion batteries -- solid–liquid phase conversion reactions; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202110017
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Although ether‐based electrolytes have gradually been identified as a vital factor to achieving the excellent electrochemical performance observed in transition metal sulfide (TMS) anodes in sodium‐ion batteries (SIBs), there is still a lack of a fundamental understanding about the origin of the positive effect of ether‐based electrolytes on TMS anodes. Herein, a microspherical CoS2 anode has been taken as a representative of TMS. It has been demonstrated that the sodiation process involves not only a traditional conversion reaction taking place between solid‐state CoS2 and Na2 S, but also a solid–liquid phase conversion process between active materials and soluble sodium polysulfide (Na2 S n, 2 < n < 8). More importantly, it is first revealed that the long‐term stability and the reversibility of CoS2 anode are mainly due to the solid–liquid conversion behavior, which makes bulk CoS2 gradually develop into a stable porous structure with fast Na + transport kinetics and small stress/strain during cycling. Consequently, the CoS2 electrode delivers remarkable long‐cycle life with an ultrahigh capacity retention rate of 94.8% even after 1500 cycles at 2 A g −1 (only 2.13 mAh g −1 fading per 100 cycles) and high volumetric capacity of 949 mAh cm −3 at a high active material loading of 3.3 mg cm −2 . Abstract : The solid–liquid conversion behavior between solid state CoS2 and liquid state soluble sodium polysulfide makes bulk CoS2 gradually develop into a stable porous structure during cycling in ether‐based electrolyte, facilitating fast Na + transport kinetics and small stress/strain during cycling. Therefore, the micron‐sized CoS2 without any modification realizes remarkable rate capacity and ultrastable cyclability.