Lithium-sulphur shows promise for EV power packs

Lithium first became famous as a salve for madness. Now, lithium madness is gripping the auto industry. First there was lithium-ion. Then, care of Hyundai, came lithium-polymer. Now comes another phase in lithium's rise to saviourdom in the battery world: lithium-sulphur.

The latest chapter comes in news from Canada's University of Waterloo that its nanotechnology research team has prototyped a lithium-sulphur-based rechargeable battery with three to five times the energy density of conventional lithium-ion.

As with lithium-ion, it works through the movement of lithium ions between positive and negative electrodes. In the University of Waterloo lithium-sulphur variety however, the whole thing hinges on a the infusion of a particularly porous variety of carbon with melted sulphur to make up the positive electrode, working with metallic lithium at the negative end.

The result is around triple the power storage capacity per unit of volume, from a pack that's also palpably lighter. And because sulphur and carbon are cheap and plentiful, it's potentially cheaper to make.

Several other research outfits are working on lithium-sulphur storage systems, including German chemicals giant BASF and Arizona company Sion Power.

It's early days yet, and they're still facing a number of hurdles, mainly safety issues associated with lithium's instability around sulphur ions (the combination has the potential to catch fire).

And while the constituent materials might be inexpensive, the research team leader Dr Linda Nazar has told media it will be a while before anyone brings down the costs of manufacture.

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