Developing better batteries
In July this year, a team led by two researchers from City University of Hong Kong, Professor Yang Ren and Professor Qi Liu, published a paper in Nature Energy entitled “A Li-rich layered oxide cathode with negligible voltage decay”.
Behind this technical-sounding headline, there is cause for some quiet excitement on the part of researchers, as the achievement by Ren, Liu and their team is an important step in developing new better technology for batteries, which have been described as the next engine of economic growth.
Croucher News caught up with the lead researchers to find out more.
Professor Ren and Professor Liu explained that the race has been on to discover alternatives to the use of cobalt in batteries, which, among other things, is very expensive. Due to their high capacity and low cost, lithium- and manganese-rich (LMR) layered oxides are regarded as a promising class of cathodes for the lithium-ion batteries widely used in electronic devices.
“The cathode, however, is the current bottleneck”, said Liu. “And the key issue is voltage decay”, he added.
One practical result of this, is that if you compare the battery technology of different generations of smartphones: “there will be no significant difference between iPhone 15 and iPhone 6 in the batteries because the development of battery technology has not progressed”, said Liu. “So you can see, this is a longstanding issue that we are dealing with”.
The problem with using lithium-rich oxides is their instability. They are partly made up of a kind of honeycomb structure. If the lithium flows out of the honeycomb structure, the honeycomb is prone to collapse, ultimately leading to voltage decay and material degradation. Other teams have worked on this issue and failed to come up with an answer.
The solution the CityU team came up with was atomic pinning, effectively using “pins” at an atomic level to keep the honeycomb structure stable, so that when lithium flowed in and out, the honeycomb didn’t collapse.
“Just like a civil engineer stabilises buildings, we were trying to stabilise a structure - only at an atomic level”, said Ren.
With stability added to the honeycomb structure, enough to withstand high-voltage cycling, the voltage decay problem can be effectively mitigated.
More work was still required to further develop their technology, “but what this will lead to is a way of making cheaper batteries that will last longer”, said Liu. This is especially significant in larger batteries, such as used in EVs, where cost is such a major issue.
So how long would it take for this advance to impact on the phones or other devices that we use?
“It’s hard to say for sure”, said Liu. “But I’d expect to see commercial use within the next five years or so.”
Given that others had tried and failed to solve this problem, we asked what the secret to success had been in this case.
“Collaboration, focus, perseverance and access to the right technology” were key, said Ren. “We were fortunate in being able to bring together a lot of expertise to focus on this issue”.
For recent news of other research into improved battery performance in Hong Kong, please click here.