Ultrasmall CoS nanoparticles embedded in heteroatom-doped carbon for sodium-ion batteries and mechanism explorations via synchrotron X-ray techniques

• Published in: Journal of energy chemistry 2023-04, Vol.79, p.373-381
• Main Authors: Liu, Congcong, Lu, Qiongqiong, Gorbunov, Mikhail V., Omar, Ahmad, Gonzalez Martinez, Ignacio G., Zhao, Panpan, Hantusch, Martin, Dimas Chandra Permana, Antonius, He, Huanyu, Gaponik, Nikolai, Mikhailova, Daria
• Format: Article
• Language: English
• Subjects: Cobalt sulfide nanoparticles; Heteroatom-doped porous carbon matrix; Reaction mechanisms; Sodium-ion batteries; Synchrotron X-ray techniques
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2023.01.011

A composite containing ultrasmall CoS nanoparticles (∼7 nm) embedded in heteroatoms (N, S, and O)-doped carbon framework was synthesized and it exhibited remarkable sodium storage performance. Moreover, the structural transformation and Co valence evolution during cycling were revealed with advanced synchrotron X-ray techniques. [Display omitted] Transition metal sulfides have been regarded as promising anode materials for sodium-ion batteries (SIB). However, they face the challenges of poor electronic conductivity and large volume change, which result in capacity fade and low rate capability. In this work, a composite containing ultrasmall CoS (∼7 nm) nanoparticles embedded in heteroatom (N, S, and O)-doped carbon was synthesized by an efficient one-step sulfidation process using a Co(Salen) precursor. The ultrasmall CoS nanoparticles are beneficial for mechanical stability and shortening Na − ions diffusion pathways. Furthermore, the N, S, and O − doped defect-rich carbon provides a robust and highly conductive framework enriched with active sites for sodium storage as well as mitigates volume expansion and polysulfide shuttle. As anode for SIB, CoS@HDC exhibits a high initial capacity of 906 mA h g−1 at 100 mA g−1 and a stable long-term cycling life with over 1000 cycles at 500 mA g−1, showing a reversible capacity of 330 mA h g−1. Meanwhile, the CoS@HDC anode is proven to maintain its structural integrity and compositional reversibility during cycling. Furthermore, Na − ion full batteries based on the CoS@HDC anode and Na3V2(PO4)3 cathode demonstrate a stable cycling behavior with a reversible specific capacity of ∼ 200 mA h g−1 at least for 100 cycles. Moreover, advanced synchrotron operando X-ray diffraction, ex-situ X-ray absorption spectroscopy, and comprehensive electrochemical tests reveal the structural transformation and the Co coordination chemistry evolution of the CoS@HDC during cycling, providing fundamental insights into the sodium storage mechanism.