Silica restricting the sulfur volatilization of nickel sulfide for high-performance lithium-ion batteries

Nickel sulfides are regarded as promising anode materials for advanced rechargeable lithium-ion batteries due to their high theoretical capacity. However, capacity fade arising from significant volume changes during operation greatly limits their practical applications. Herein, confined NiS${}_x$@C yolk–shell microboxes are constructed to address volume changes and confine the active material in the internal void space. Having benefited from the yolk–shell structure design, the prepared NiS${}_x$@C yolk–shell microboxes display excellent electrochemical performance in lithium-ion batteries. Particularly, it delivers impressive cycle stability (460 mAh g${}^{-1}$ after 2000 cycles at 1 A g${}^{-1}$) and superior rate performance (225 mAh g${}^{-1}$ at 20 A g${}^{-1}$). Furthermore, the lithium storage mechanism is ascertained with in situ synchrotron high-energy X-ray diffractions and in situ electrochemical impedance spectra. This unique confined yolk–shell structure may open up new strategies to create other advanced electrode materials for high performance electrochemical storage systems. (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)