Cellulose Fiber based self-supporting paper cathode with multi-scale network structure for high performance lithium-sulfur battery

Lithium-sulfur batteries (LSBs) are gaining attention as a potential energy storage option due to their impressive theoretical specific capacity. However, the main challenges hindering its implementation include the expansion in volume of sulfur and lithium sulfide during the conversion process of charge-discharge, the limited conductivity of the active material, and specifically, the phenomenon known as shuttle effect caused by lithium polysulfides (LiPSs). The development of high-performance LSBs have led to the need for self-supporting cathode materials that can efficiently accommodate volume expansion, build up efficient conductive pathways, and suppress shuttle effects. The poly(3,4-ethylenedioxythiophene) (PEDOT) was synthesized in situ on cellulose nanofibers (CNFs), resulting in the formation of CNF@PEDOT. Subsequently, CNF@PEDOT was combined with plant fibers (PFs) and multi-wall carbon nanotubes (MWCNTs) to fabricate a self-supporting cathode featuring a multi-scale network structure denoted as CNF@PEDOT/MWCNT/PF/S. The PFs serve as the primary backbone network, CNF@PEDOT to form the secondary conductive network, and MWCNTs act as tertiary conducting networks. In fact, the design of multi-level conductive network effectively improves the conductivity of the material, and PEDOT can further adsorb and catalyze LiPSs. The incorporation of PFs significantly enhanced the mechanical robustness of the cathode and augmented its electrolyte permeability. The self-supporting CNF@PEDOT/MWCNT/PF/S cathode exhibits an initial capacity of 1204.6 mA h g−1 when loaded with 2.4 mg cm−2 of sulfur at a rate of 0.2 C. Notably, it maintains an initial discharge specific capacity of 712.9 mA h g−1 even when the sulfur load is increased to 4.3 mg cm−2. This study presents a comprehensive framework for the development of self-supporting cathodes in LSBs.