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Extremely Small Pyrrhotite Fe 7 S 8 Nanocrystals with Simultaneous Carbon‐Encapsulation for High‐Performance Na–Ion Batteries
Author(s) -
Choi MinJae,
Kim Jongsoon,
Yoo JungKeun,
Yim Soonmin,
Jeon Jaebeom,
Jung Yeon Sik
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201702816
Subject(s) - materials science , nanocrystal , anode , pyrrhotite , ion , chemical engineering , carbon fibers , nanotechnology , battery (electricity) , electrochemistry , electrode , optoelectronics , sulfide , power (physics) , composite number , chemistry , thermodynamics , composite material , physics , organic chemistry , engineering , metallurgy
Abstract Na/FeS x batteries have remarkable potential applicability due to their high theoretical capacity and cost‐effectiveness. However, realization of high power‐capability and long‐term cyclability remains a major challenge. Herein, ultrafine Fe 7 S 8 @C nanocrystals (NCs) as a promising anode material for a Na–ion battery that addresses the above two issues simultaneously is reported. An Fe 7 S 8 core with quantum size (≈10 nm) overcomes the kinetic and thermodynamic constraints of the Na‐S conversion reaction. In addition, the high degree of interconnection through carbon shells improves the electronic transport along the structure. As a result, the Fe 7 S 8 @C NCs electrode achieves excellent power capability of 550 mA h g −1 (≈79% retention of its theoretical capacity) at a current rate of 2700 mA g −1 . Furthermore, a conformal carbon shell acts as a buffer layer to prevent severe volume change, which provides outstanding cyclability of ≈447 mA h g −1 after 1000 cycles (≈71% retention of the initial charge capacity).