Sn–Co Nanoalloys Encapsulated in N-Doped Carbon Hollow Cubes as a High-Performance Anode Material for Lithium-Ion Batteries

To address the huge volumetric change and unstable solid electrolyte interphase (SEI) issues of Sn-based anodes, this paper proposes a Sn–Co–C ternary composite with a cubic yolk–shell structure. The proposed Sn–Co nanoalloys encapsulated in N-doped carbon hollow cubes (Sn–Co@C) are simply synthesized by the conformal polydopamine coating of home-made CoSn(OH)6 hollow nanocubes subsequent with hydrogen reduction. The cubic Sn–Co@C yolk–shell structure possessing an optimized carbon shell thickness displays excellent cyclic performance and superior rate capability when utilized as an anode for lithium-ion batteries. The composite shows an initial discharge capacity of 885 mA h g–1 at 200 mA g–1 with a high capacity retention of ∼91.2% after 180 cycles. It can still deliver a considerable capacity of 560 mA h g–1 at a high current density of 1 A g–1 after 200 cycles. This attractive electrochemical characteristic can be ascribed to the distinct cubic yolk–shell architecture, in which the inner inactive Co can buffer the volumetric expansion of Sn, the void can provide external space for the volumetric change of Sn, and the outer carbon shell can effectively prevent the agglomeration of Sn–Co nanoalloys and maintain the stability of SEI films.