APPLICATIONS OF TECHNOLOGY:
Lithium Sulfur (Li-S) rechargeable batteries for
- Consumer electronic devices (especially cellular devices)
- Electric Vehicles
- Grid storage
- Electric powered aviation
- Highly reversible discharge capacity
- Stable and high rate battery cycling
- Redox active binder
A team of researchers at Berkeley Lab led by Elton J. Cairns and Brett Helms has developed a technology to improve electron and ion transport in solid-state lithium sulfur (Li-S) battery electrode binders. This technology will enable high capacity, low cost, and large scale Li-S cells competitive with lithium ion batteries.
The Berkeley Lab binder uses a mix of perylene bisimide (PBI) and polyvinylidene difluoride (PVDF) molecules instead of solely PVDF molecules. Recent reports have suggested that PVDF can block the pores of mesostructured conductive carbons, which negatively impacts the available surface area for Li2S electrodeposition. Comparatively, the mix of PBI and PVDF creates a redox-active supramolecular binder that can self-heal to accommodate volume changes in the sulfur cathode on cycling and adaptive charge transport upon activation.
The PVDF molecule showed a discharge capacity of 1050 mAh/g S, however, the specific discharge capacity of the PVDF cathode decreased dramatically as the test C-rate increased, and finally, a specific discharge capacity of only about 320 mAh/g S was obtained at 1.0 C discharge. In contrast, the PBI/PVDF composite binder cathode exhibited the better rate capability with a highly reversible discharge capacity of about 800 and 350 mAh/g S at C- rates of 1.0 and 3.0 C, respectively, and the specific discharge capacity recovered quickly to 1066 mAh/g S, when the C-rate was decreased back to 0.1 C.
The high theoretical specific capacity of a sulfur cathode and the low cost and environmental impact of sulfur make Li-S cells a strong contender to overtake lithium ion batteries in the marketplace. However, sulfur cathodes engineered for high energy density and durability lack high power while attaining high specific energy. Berkeley Lab’s flexible redox-active binders show reduced cell impedance and stable cycling to help Li-S batteries reach their commercial potential.
DEVELOPMENT STAGE: Proven principle.
STATUS: Published U. S. Patent Application 15/467,099 (Publication No. US2017-0279122). Available for licensing or collaborative research.
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