Adding sulphur to electrical cells may quintuple their performance – Lithium-sulphur batteries

BUILD a better battery, to paraphrase Ralph Waldo Emerson, and the world will beat a path to your door. For consumer goods, from computers to cars, “better” means “better than lithium-ion”

BUILD a better battery, to paraphrase Ralph Waldo Emerson, and the world will beat a path to your door. For consumer goods, from computers to cars, “better” means “better than lithium-ion”. And several groups of engineers think they have one: it is based on lithium and sulphur.

A lithium-ion (Li-ion) battery works by shuttling the eponymous ions, which are positively charged, through an electrolyte that links two electrodes, one made of carbon and the other of a substance containing a heavy metal such as cobalt, manganese or nickel. Such metals have multiple oxidation states, meaning they can lose or gain different numbers of electrons in different circumstances. To balance the movement of lithium ions, electrons (which are negatively charged) move to or from the heavy metal through an external circuit that also links the electrodes, changing the metal’s oxidation state as they do so. When the battery is discharging, both ions and electrons travel spontaneously in one direction, creating a current and releasing energy. When it is being recharged they are forced, by the application of a voltage, to go the other way and thus to store energy.

Lithium-sulphur batteries work in a similar fashion, but dispense with the heavy metal. Instead, they use sulphur, which also has multiple oxidation states—more of them, indeed, than many metals do. This fact, combined with sulphur’s lightness, means lithium-sulphur batteries can, in principle, store four or five times as much energy per gram as lithium-ion ones manage. And, since sulphur is cheap, they can do so at lower cost.

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