Making Lithium Sulfur Batteries Last Longer

University of Delaware researchers have demonstrated a new polysulfide entrapping strategy that greatly improves the cycle stability of Lithium Sulfide batteries. This may be significant as the energy density of lithium-sulfur (Li-S) batteries is five times higher than that of Lithium-Ion (Li-ion) batteries.

Rechargeable Li-ion batteries are the power behind most modern portable electronics. But their energy density – that is, the amount of energy stored within a given amount of physical space, or mass – will need to be improved for these batteries to see widespread use in smart grid and electric transport applications.

In contrast, the energy density of Li-S batteries is five times higher than that of Li-ion batteries. That advantage, combined with low cost, suggests that this alternative technology shows promise for high-energy storage applications.

Standing in the way is Li-S batteries are limited by a different problem: rapid capacity fade, which means that the amount of charge these batteries can deliver at the rated voltage decreases significantly with each use.

Bingqing Wei, professor in the Department of Mechanical Engineering at the University of Delaware, explains that this problem stems from a phenomenon known as the polysulfide shuttle effect, in which the spontaneous formation of polysulfides inhibits performance.

Now, Wei and colleagues have demonstrated a new polysulfide entrapping strategy that greatly improves the cycle stability of Li-S batteries.

The team’s study paper “Ferroelectric-Enhanced Polysulfide Trapping for Lithium-Sulfur Battery Improvement” has been published in Advanced Materials. The authors include researchers from Northwestern Polytechnical University, Shenzhen University and Hong Kong Polytechnic University in China.

The team asserts in the study, “By simply adding the nano-ferroelectrics (BaTiO3 nanoparticles) into the cathode, the heteropolar polysulfides can be anchored within the cathode due to the internal electric field originated from the spontaneous polarization BaTiO3 nanoparticles, and thus significantly improving the cycle stability of Li–S batteries.

Wei explains that the addition of ferroelectric nanoparticles into the battery cathode anchors the polysulfides, preventing them from dissolving and causing the loss of active materials at the cathode.

Wei said, “While the mechanism underlying the trapping of polysulfides is unclear at this point, we’re optimistic about the potential of this approach to high-performance lithium-sulfur battery applications, as it not only solves the problem of the polysulfide shuttle effect but also can be seamlessly coupled to current industrial battery manufacturing processes.”

Not only does Li-S battery tech offer more power per volume and weight, the material costs are lower than the equivalent capacity Li-ion technology. If this design works and keeps working over the same or more charging cycles at a low price, the larger Li-ion battery sets could get switched out with a smaller, lighter and lower cost Li-S battery sets really quickly.