A new materials science discovery could allow lithium-ion batteries used in EVs and electronics to charge substantially faster than today.
One of the biggest struggles in encouraging people to buy electric vehicles (EVs) is the complaint that the time it takes to charge them is too long. However, researchers from the Rensselaer Polytechnic Institute in the US have revealed a new method that could allow lithium-ion batteries, which are used in EVs, to be charged in a matter of minutes.
A lithium-ion battery’s ability to charge and discharge is controlled by lithium ions that move between two electrodes, called an anode and cathode. Traditionally, the anode is made from graphite, while the cathode is composed of lithium cobalt oxide.
While they work well together, attempts are being made to find new and improved materials that could dramatically boost charging time, all while maintaining high capacity.
Published in a study to Nature Communications, this research saw corresponding author Nikhil Koratkar and the rest of his team substitute cobalt oxide with vanadium disulphide (VS2).
“It gives you higher energy density because it’s light. And it gives you faster charging capability because it’s highly conductive,” he said. “From those points of view, we were attracted to this material.”
In recent years VS2 has become a popular material for lithium-ion battery research but has been limited by its instability, which could lead to a short battery life. To better understand this, the researchers discovered that lithium insertion caused an asymmetry in the spacing between vanadium atoms – known as a Peierls distortion – which was responsible for the break-up of the VS2 flakes.
They discovered that covering the flakes with a nanolayered coating of titanium disulphide (TiS2) prevents this distortion and stabilises VS2 flakes to improve the performance of batteries.
“This was new. People hadn’t realised this was the underlying cause,” Koratkar said. “The TiS2 coating acts as a buffer layer. It holds the VS2 material together, providing mechanical support.”
With this problem solved, they found that the VS2-TiS2 electrodes could operate at a high specific capacity, or store a lot of charge per unit mass. Vanadium and sulphur’s small size and weight also make them ideal for being used in compact batteries.
Koratkar sees multiple applications for this discovery, such as improving car batteries, portable electronics and solar energy storage where high capacity is important, but increased charging speed would also be highly sought after as well.