Accurately tailoring yolk-shell spheres to balance cycling stability and volumetric capacity of lithium storage

Yolk-shell structure is a promising material design for alloying type anode due to its void space accommodating the volume change during battery cycle life. However, the coordination between void space and core size is an issue for yolk-shell structured anode materials achieving excellent cycling stability and reasonable high volumetric energy density. Herein, we propose a strategy of in-situ shell-to-core evolution to accurately control the void space and core size in yolk-shelled spheres. Based on this approach, we have synthesized a yolk shelled composite with a Sn nanoparticle encapsulated in a N doped C shell (YS-Sn@ void@NxC). The controlled core size and void space, and their relationship with anode electrochemical performance have been systematically studied. The optimal YS-Sn@void@NxC electrode demonstrates excellent cycling stability of 1110 mAh cm-3 for volumetric capacity and 820 mAh g-1 for gravimetric capacity after 1000 cycles at 1 C (1 C = 1000 mA g-1). We believe that the facile yolk-shelled structure designing strategy in this work could be extended to synthesize other low melting point metals, such as Bi, Pb, In, Ge, etc., for their functional applications.

Automated summary

The yolk-shell structure is a promising material design for anodes in batteries due to its ability to accommodate volume changes. However, achieving coordination between space and core size is a challenge. In this study, a strategy of in-situ shell-to-core evolution was proposed to accurately control the void space and core size. A composite with controlled core size and void space was synthesized and demonstrated excellent cycling stability and high volumetric energy density.