Carbon-coated graphene/antimony composite with a sandwich-like structure for enhanced sodium storage

Abstract

Sodium-ion batteries (SIBs) are considered to be one of the most promising alternatives to lithium-ion batteries (LIBs) for energy storage due to the low cost and large abundance of natural sodium resources. However, the search for suitable sodium storage anode materials with enhanced rate capability and cycling stability is much more difficult for SIBs, due to the larger ionic radius of the sodium-ion than that of the lithium-ion. In this work, we design and fabricate a new type of carbon coated graphene/antimony composite (G@Sb@C) with a unique sandwich-like structure. The graphene framework and carbon layer can enhance the electronic conductivity and disperse the Sb particles uniformly. In addition, the covered carbon layer can buffer the volume change, suppress the aggregation of Sb, and stabilize the integrated structure of the composite during the cycling processes. As an anode material for SIBs, the G@Sb@C electrode delivers a high reversible capacity of 569.5 mA h g⁻¹ after 200 cycles at a current rate of 0.1 A g⁻¹, and the coulombic efficiency is ca. 99%. Moreover, the capacity reaches 433 mA h g⁻¹ even at a high current rate of 5.0 A g⁻¹. We believe that the unique sandwich-like structure design could also be extended to develop other materials suffering from the large volume change during charge/discharge cycling.