A breakthrough in chemical engineering may pave the way for more powerful, longer-lasting batteries.
For modern battery-powered devices like electric cars, lithium-ion batteries’ relatively low energy capacity limits how far they can travel. Their anodes, the parts through which electricity enters the battery, are currently made from graphite. Batteries with graphite anodes have a relatively low battery capacity, which is why electric cars have to recharge frequently. Silicon anodes have the potential to increase battery capacity by three to five times, but lithium-silicon batteries can only be used a small number of times before they decay.
The research team, based at KAIST, a South Korean research university, has developed a molecular pulley system that significantly slows the decay of the battery, making it much more practical for public use. This molecular system “resolves the issue” of silicon decay and makes lithium-silicon batteries “commercially viable,” said Soojin Park, a professor of energy and chemical engineering at the Ulsan National Institute of Science of Technology who did not contribute to the research. The team’s work was published yesterday in Science.
Silicon is cheap and there’s plenty of it, so it has great potential for use in higher capacity batteries. But as the battery charges, the silicon expands dramatically, leading to significant stress on the system and causing electrode particles to fracture. As a result, these silicon anodes quickly lose their high energy capacity.
According to Park, the team’s novel insight was the construction of an elastic network of molecular strings and rings that allow the anode to expand without breaking. “This system can rapidly release the internal stress,” so the battery is able to maintain a large fraction of its energy capacity over a long period of time, Park wrote in a commentary also published Science.
This has important implications for the commercial use of lithium-silicon batteries, allowing people to use these more practical and powerful batteries for longer periods of time, which could help to popularize the use of electric vehicles. We could see these batteries in use in cars on the road “in the near future,” Park said.