Incorporating TiO2 nanoparticles into the multichannels of electrospun carbon fibers to increase the adsorption of polysulfides in room temperature sodium-sulfur batteries

Abstract

With the rapid development of electric vehicles and large-scale power grids, lithium-ion batteries inevitably face the problem that their limited energy density and high cost cannot meet the growing demand. Room temperature sodium-sulfur (RT Na-S) batteries, which have the potential to replace lithium-ion batteries, have become a focus of attention. However, the challenging problem of their poor cycling performance cause by the “shuttle effect” of the reaction intermediates (sodium polysulfides) needs to be addressed. We report a method to incorporate TiO2 nano particles into the multichannels of electrospun carbon fibers (TiO2@MCCFs) to stabilize the sulfur compounds and produce high-performance RT Na-S batteries. The TiO2@MCCFs were prepared by electrospinning followed by heat treatment, and were infiltrated by molten sulfur to fabricate S/TiO2@MCCF cathode materials. The addition of the TiO2 nanoparticles increases the affinity of cathode materials for polysulfides and promotes the conversion of polysulfides to lower order products. This was verified by DFT calculations. A S/TiO2@MCCF cathode with a S content of 54% has improved electrochemical rate and cycling performance, with a specific capacity of 445.1 mAh g−1 after 100 cycles at 0.1 A g−1 and a nearly 100% Coulombic efficiency. Even at 2 A g−1, the cathode still has a capacity of 300.5 mAh g−1 after 500 cycles. This work provides a new way to construct high performance RT Na-S battery cathodes.