Conductivity and Pseudocapacitance Optimization of Bimetallic Antimony-Indium Sulfide Anodes for Sodium-Ion Batteries with Favorable Kinetics

Metal sulfides show promise for use in alkali-ion batteries because of their high theoretical capacities. However, their poor cycling stability and rate performance hinder their further development. To avoid these issues, In2S3 into Sb2S3 is introduced to improve its electrochemical properties by optimizing its crystal structure and sodium storage mechanism. A heterostructure composed of In2S3 and Sb2S3 shows a unique morphology of formicary microspheres, which provide abundant channels for fast transfer of sodium ions, large surface area for a high pseudocapacitance effect, and enough voids to relieve volume expansion. A sodium-ion battery containing the bimetallic sulfide anode exhibits a high reversible capacity of 400 mA h g(-1) and long cycle life of about 1000 cycles. Similarly, a high capacity of approximate to 610 mA h g(-1) is achieved for a lithium-ion battery containing the anode. During sodiation/desodiation, the synergistic effect of In2S3 and Sb2S3 enhances electronic conductivity and supports the host structure, preventing collapse. The cycling performance and rate performance of the In2S3-Sb2S3 anode are further improved by wrapping the electrode with carbon nanotubes. Even at a high current density of 3.2 A g(-1), this carbon composite structure still shows a capacity of about 355 mA h g(-1).