Our cathode design concurrently provides expansion tolerance, strong polysulfide crossover limitation, and ion diffusion highways via nano-structuring-and it can be fabricated at scale from commonly sourced materials. Unfortunately, these features have not yet delivered long term stable Li-S batteries because all prospective properties need to be combined within one system. The general conclusion from such studies for targeted retardation of polysulfide shuttling is that binders with polar/electronegative functional groups are beneficial to the sulfur cathode 16. Furthermore, novel binder systems have been critically designed to add polysulfide absorbing functionality to the binder such as the electroactive nanocomposite binder composed of polypyrrole and polyurethane (PPyPU) 16, and modified cyclodextrin (C-β-CD) 17. From these studies it can be inferred that cellulose-based binders serve well in fabricating mechanically robust cathodes. To date several binder systems, such as natural gums 11, 12 and cellulose based binders 13, 14, 15 have been explored to assist with the volume change. Li-S cycle life can be improved by using cathodes that can simultaneously accommodate the volume change and confine the polysulfides. Eventually, the cell dries up and fails - presenting the biggest challenge to Li-S battery chemistry. The continuous reformation of the SEI is accompanied by the continuous consumption of the electrolyte. This leaves the freshly formed lithium surface in dynamic exchange with the polysulfide containing electrolyte 10. In stark contrast with Li-ion batteries, the solid electrolyte interphase (SEI) layer on the anode of the Li-S battery, while readily formed, also easily cracks due to polysulfide attack and the large swelling associated with lithium exchange. However, the problem of achieving high capacity simultaneously with extended cycle life has largely remained unsolved. Quite recently, we have uncovered a pathway to overcome the structural instability of cathode, by introducing the expansion-tolerant architecture 9. Later on, they reported on the introduction of polysulfide absorbents and mediators to the composition of the sulfur cathode and addressed the issue of ‘polysulfide shuttling’ to a large extent 8. carried out pioneering research in the area of composite sulfur cathodes and addressed the challenge of the low-electrical conductivity of the sulfur cathode 7. The power performance of the Li-S system is also inherently slow, particularly when the sulfur cathode is loaded to the required levels, mainly due to poor ion diffusion across the thickness of the cathode.Įxtensive research over the past ten years has delivered marked improvements in the sulfur cathode, as well as a profound understanding of the failure mechanisms 2, 3, 4, 5, 6. Until now, the realization of Li-S batteries has been challenging, mainly due to the instability of both electrodes, which results in a short cycle life of the battery.
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They can be made from materials that are readily and sustainably available around the world. One such technology could be lithium-sulfur batteries (Li-S): which theoretically store as much as five times the energy of Li-ion and have a realizable specific energy of 400–600 Wh kg −1. At the same time, the viability of many emerging technologies, for example in aviation, require lighter-weight batteries. But as society moves away from fossil fuels at a massive scale, new battery chemistries with higher storage capacities and lower demands on critical minerals are going to be central 1. Lithium-ion batteries (Li-ion) have changed the world. A pouch cell prototype with a specific energy of up to 206 Wh kg −1 is produced, demonstrating the promising potential for practical applications. Taken together this leads to 97% sulfur utilisation with a cycle life of 1000 cycles (9 months) and capacity retention (around 700 mAh g −1 after 1000 cycles). Furthermore, the binder promotes the formation of viscoelastic filaments during casting which endows the sulfur cathode with a desirable web-like microstructure. Here, we present a saccharide-based binder system that has a capacity for the regulation of polysulfides due to its reducing properties. Therefore, development of a durable cathode with minimal polysulfide escape is critical. Most instability stems from the release and transport of polysulfides from the cathode, which causes mossy growth on the lithium anode, leading to continuous consumption of electrolyte.
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The viability of lithium-sulfur batteries as an energy storage technology depends on unlocking long-term cycle stability.