The electrochemical storage mechanism of an In2S3/C nanofiber anode for high-performance Li-ion and Na-ion batteries

Abstract

There are only a handful of reports on indium sulfide (In₂S₃) in the electrochemical energy storage field without a clear electrochemical reaction mechanism. In this work, a simple electrospinning method has been used to synthesize In₂S₃/C nanofibers for the first time. In lithium-ion batteries (LIBs), the In₂S₃/C nanofiber electrode can not only deliver a high initial reversible specific capacity of 696.4 mA h g⁻¹ at 50 mA g⁻¹, but also shows ultra-long cycle life with a capacity retention of 80.5% after 600 cycles at 1000 mA g⁻¹. In sodium-ion batteries (SIBs), the In₂S₃/C nanofibers electrode can exhibit a high initial reversible specific capacity (393.7 mA h g⁻¹ at 50 mA g⁻¹) and excellent cycling performance with a high capacity retention of 97.3% after 300 cycles at 1000 mA g⁻¹. The excellent electrochemical properties mainly benefited from In₂S₃ being encapsulated by a carbon matrix, which buffers the volume expansion and significantly improves the conductivity of the composite. Furthermore, the structural evolution of In₂S₃ during the first lithiation/delithiation and sodiation/desodiation processes has been illustrated by ex situ XRD. The results confirm that the reaction mechanism of In₂S₃ in both LIBs and SIBs can be summarized as conversion reactions and alloying reactions, which provide theoretical support for the development of In₂S₃ in the field of electrochemistry.