Unveiling solid electrolyte interface morphology and electrochemical kinetics of amorphous Sb2Se3/CNT composite anodes for ultrafast sodium storage

Sb2Se3 based anodes are widely studied for advanced Na-ion batteries. However, their Na storage performance at high rates is limited to 2000 mA g(-1) because of poor kinetics of redox reactions. Here, the heterointerfacial interactions taking place between Sb2Se3 and functionalized CNTs are probed to understand the formation of Sb-O-C and Se-C bonds in the amorphous a-Sb2Se3/CNT composite using the density functional theory and ab-initio molecular dynamics simulations. The distinct morphologies and thicknesses of solid electrolyte interface layers formed on crystalline c-Sb2Se3 and a-Sb2Se3/CNT composite electrodes are revealed by advanced cryogenic transmission electron microscopy and their influences on the kinetics of redox reactions in the corresponding electrodes are identified. The structurally robust a-Sb2Se3/CNT composite electrode exhibits four orders of magnitude higher Na-ion diffusion coefficient than the crystalline c-Sb2Se3 counterpart, giving rise to an exceptional high-rate capacity of 454 mA h g(-1) at 12800 mA g(-1) and capacity retention of over 62% after 200 cycles at 10000 mA g(-1). The full cells containing the composite electrodes present energy and power densities of similar to 175 Wh kg(-1) at 0.5C and similar to 5784 W kg(-1) at 80C, respectively, and stable cyclic performance up to 120 cycles. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study investigates the heterointerfacial interactions between Sb2Se3 and functionalized CNTs to enhance the energy storage performance of Na-ion batteries. Results show that the a-Sb2Se3/CNT composite electrode exhibits significantly higher Na-ion diffusion coefficient and high-rate capacity, along with good cyclic stability.