Researchers have built a prototype lithium-sulphur battery that — when perfected — could have up to five times the energy density of current lithium-ion devices. Researchers in the UK and China drew inspiration from intestines to overcome problems in the battery construction.
In your intestine, small hair-like structures called villi increase the surface area that your body uses to absorb nutrients from food. In the new lithium-sulphur battery, researchers used tiny zinc oxide wires to form a layer of material with a villi-like structure. These villi cover one electrode and can trap fragments of the active material when they break off, allowing them to continue participating in the electrochemical reaction that produces electricity.
Lithium-sulphur batteries aren’t new (in fact, they were used in 2008 in a solar-powered plane that broke several records), but this new technique may make them more practical. You can see a video about ordinary lithium-sulphur batteries below along with more on how this research improves the state of the art.
A typical lithium-ion battery contains graphite and lithium cobalt oxide. Positively charged lithium ions move back and forth from the cathode, through the electrolyte and into the anode. Since the carbon atoms in the graphite can only take (at most) one lithium ion, that sets the theoretical limit on how much energy you can draw from the battery.
Sulphur and lithium react differently, via a multi-electron transfer mechanism. That’s why sulphur can offer a much higher theoretical capacity. However, as the battery undergoes several charge-discharge cycles, bits of the sulphur break away causing the battery to gradually lose active material. The zinc oxide villi tend to trap these pieces which slows the degradation of the battery.
The villi improved the number of times the prototype battery can be charged and discharged, but it is still not able to match a conventional lithium-ion battery. On the other hand, the new battery doesn’t need recharging as often.
Photo credit: [Teng Zhao]