Sb2S3-Bi2S3 microrods with the combined action of carbon encapsulation and rGO confinement for improving high cycle stability in sodium/potassium storage

Abstract

For sodium and potassium storage, the inevitably large volume variation in the process of charge/discharge for the anode materials with conversion and alloying mechanisms leads to unsatisfactory structural stability and capacity retention. In this work, Sb2S3-Bi2S3 microrods were designed and constructed to be wrapped by carbon sheaths and attached into graphene sheets to successfully maintain the structural stability of the composite. The dual structural protection of carbon and rGO encapsulations confine the Sb2S3-Bi2S3 within the electrochemical reactions to alleviate the volume fluctuation and thus promote the cycling property. As a consequence, the obtained Sb2S3-Bi2S3@C@rGO composite exhibited a promising long-term cyclic stability in sodium ion batteries with a specific capacity of 460.5 mA h g−1 after 1100 cycles at the current density of 8 A g−1. In addition, a combined reaction mechanism of conversion and alloying was demonstrated by in-situ X-ray diffraction and ex-situ transmission electron microscopy.