Electrophoretically deposited binder-free 3-D carbon/sulfur nanocomposite cathode for high-performance Li–S batteries

Abstract

In the present study, the electrophoretic deposition method was successfully applied as a binder-free and scalable approach to deposit carbonaceous nanomaterials on carbon fiber paper (CFP) for cathode applications in Li–S batteries. The microstructural studies of the EPD-CNT film using scanning electron microscopy (SEM) revealed the formation of a crack-free and porous layer of CNTs being uniformly distributed on the CFP surface. The EPD:CFP/CNT/S cathode delivered a capacity around 2.2 times higher than that obtained in the absence of the EPD-CNT film (CFP/S cell) after 50 cycles and a capacity of 935 mAh g −1 after 100 cycles at 0.1 C. The EPD method was then employed to fabricate layer-by-layer structures where the EPD-CNT film was decorated with carbon black particles. The initial capacity as well as the reversible capacity after 100 cycles was further increased by the EPD:CFP/CNT/KB/S layer-by-layer structure to 1473 and 1033 mAh g −1 , respectively, indicating effective suppression of the shuttle effect. In addition, the rate performance of CFP/S was improved by depositing the EPD-CNT and EPD-CNT/carbon black architectures on CFP surface, and even further enhanced through the co-deposition of CNT and Pt nanoparticles by EPD, delivering a specific capacity of around 730 mAh g −1 at 1 C. Finally, the cathodes fabricated by EPD were observed to outperform those made by the conventional casting method in terms of cycling performance, internal resistance, and polarization. This difference was ascribed to the non-uniform microstructure of the Cast-CNT film, which resulted in poor interfacial connection between the CNT agglomerates, hindering uniform sulfide/sulfur deposition during cycling. The obtained results suggested that the binder-free C/S nanocomposite cathode made by EPD is key to further enhance the specific capacity and energy density of Li–S batteries. High capacity and rate performance binder-free Li-S cathode can be fabricated in 10 min by electrophoretic deposition (EPD); the cathode containing a mixture of CNT and Ketjen Black delivers an initial capacity of 1473 mAh g −1 at 0.1 C.