Multi-yolk–shell SnO₂/Co₃Sn₂@C Nanocubes with High Initial Coulombic Efficiency and Oxygen Reutilization for Lithium Storage

Abstract

The challenging problems of SnO₂ anode material for lithium ion batteries are the poor electronic conductivity and the low oxygen reutilization due to the irreversibility of Li₂O generated in the initial discharge leading to a theoretical initial Coulombic efficiency (ICE) of only 52.4%. Different from these strategies, this work proposes a novel strategy to level up the oxygen reutilization in SnO₂ by introducing Co₃Sn₂ nanoalloys which can release Co atoms to reversibly react with Li₂O instead. According to this protocol, multi-yolk-shell SnO₂/Co₃Sn₂@C nanocubes are designed and successfully prepared using hollow CoSn(OH)₆ nanocubes as precursors followed a hydrothermal carbon coating and calcination treatment. The unique multi-yolk-shell nanostructure offers adequate breathing space for the volumetric deformation during long-term cycling. Moreover, the removal of Li₂O allows a high electronic conductivity and resultant rate performance. As a result, the efficient reutilization of oxygen enables a high ICE of 71.7% and a reversible capacity of 1003 mA h g^-1 after 200 cycles at 100 mA g^-1. Cyclic voltammetry, cycling performance at different voltage windows, and X-ray photoelectron spectroscopy confirm the proposed mechanism. This strategy employing oxygen-poor metals or alloys provides a novel approach to enhance the oxygen reutilization in SnO₂ for higher reversibility.