Bifunctional hydrogen-bonding cross-linked polymeric binder for high sulfur loading cathodes in lithium/sulfur batteries

An Expansion-Mitigant Binder for Stable Cycling of High-Loading Lithium-Sulfur Batteries

Lithium-sulfur batteries with high sulfur content and mass loading are promising energy storage technologies due to sulfur's exceptional theoretical energy density. However, in practice, their actual capacity drastically decays when the sulfur cathode is loaded to the commercially required levels of 4 mgsulfur cm-2 and above, significantly reducing the energy density. This reduction is due to the excessive formation of polysulfides during sulfur lithiation, which not only deteriorates battery performance through their detrimental shuttling but also results in substantial stress buildup due to their significantly larger volume compared to sulfur. To address these challenges, we have developed an approach to suppress lithium polysulfide shuttling by limiting the space for sulfur expansion while improving the Li+ ion diffusion. This was achieved through a straightforward but effective method to cross-link the organic binder used in sulfur electrodes. Specifically, PVDF, one of the most common binder materials for battery electrodes, was studied. The chemical, mechanical, and structural properties of the cross-linked PVDF binder were thoroughly investigated, compared with standard PVDF, and correlated to the achieved electrochemical performance of sulfur electrodes. As a result, sulfur cathodes with cross-linked PVDF binder exhibited prolonged cycle life compared to their standard counterparts. Moreover, using this expansion-mitigant binder, cathodes with areal sulfur loading of 4 mg cm-2 showed exceptional stability for more than 200 cycles and a Coulombic efficiency above 97%. This approach offers a promising avenue to alleviate the major roadblocks of lithium-sulfur battery commercialization while allowing the utilization of the commonly accessible and well-studied binder chemistries.

Hybrid Membrane Composed of Nickel Diselenide Nanosheets with Carbon Nanotubes for Catalytic Conversion of Polysulfides in Lithium-Sulfur Batteries

Lithium-sulfur batteries demonstrate enormous energy density are promising forms of energy storage. Unfortunately, the slow redox kinetics and polysulfides shuttle effect are some of the factors that prevent the its development. To address these issues, the hybrid membrane with combination of nickel diselenide nanosheets modified carbon nanotubes (NSN@CNTs) and utilized Li2 S6 catholyte for lithium sulfur battery. The conductive CNTs facilitates fast electronic/ionic transport, while the polarity of NSN as a strong affinity to lithium polysulfides, effectively anchoring them, facilitating the redox conversion of polysulfide species, and effectively diminishing reaction barriers. The cell with NSN@CNTs delivers the first discharge capacity of 1123.8 mAh g-1 and maintains 786.5 mAh g-1 after 300 cycles (0.2 C) at the sulfur loading 5.4 mg. Its rate capability is commendable, enabling it to sustain a capacity of 559.8 mAh g-1 even at a high discharge rate of 2 C. In addition, its initial discharge capacity can remain 8.33 mAh even at 10.8 mg for duration of 100 cycles. This research indicates the potential application of NSN@CNTs hybrid materials in lithium-sulfur batteries.

Intermolecular interactions of an isoindigo-based organic semiconductor with various crosslinkers through hydrogen bonding

The effects of crosslinkers, functioning via hydrogen bonding, on controlling the arrangement of molecules were investigated. The hole mobility of hydrogen-bonded organic materials displaying long-range order was significantly enhanced.