- The team inserted an additional “anti-short layer” on the separator, preventing any dendrite from reaching the cathode.
- The anti-short layer is a common material used in battery manufacturing and can be easily integrated into the current separator manufacturing process, making it easy for companies to adopt and scale up.
- The team will be further developing the technology and testing it on commercial standardised Li-ion battery cells, in partnership with interested companies.
Lithium (Li)-ion batteries occasionally catch fire and no one will forget about the Note7 smartphones in 2016.
These batteries have been in the headlines for many years and have caused fires in laptops, hoverboards, Tesla cars, smartphones and even in the electrical system of a Boeing 787 Dreamliner jumbo jet.
In most Li-ion battery fires, the cause is due to a build-up of lithium deposits known as dendrites (tiny wire-like tendrils) that cross the separator between the positive (cathode) and negative (anode) electrodes of the battery when it is being charged, causing a short-circuit leading to an uncontrolled chemical fire.
In a conventional lithium-ion battery, the positive electrode and negative electrode are kept apart by a separator. As the battery charges, the lithium dendrites grow from the negative electrode towards the positive side in the polyethene separator.
When the battery is charging, Li-ions are transferred from the cathode to the anode, and when discharging, the Li-ions move vice-versa
As batteries improved and engineers try to pack more power into a smaller package, the separator is taxed to its limit and causes a short circuit, one of the major ways that fires begin.
The chemicals inside the battery begin to heat up and can ignite or even explode when exposed to the oxygen in the air.
Even with an estimated failure rate of less than one-in-a-million, solving this problem would not only protect lives and property, it would also make it possible to use larger battery packs with more closely packed cells.
Scientists from Nanyang Technological University, Singapore (NTU Singapore), have found a way to prevent internal short-circuits by inventing an additional “anti-short layer” on the separator, preventing any dendrite from reaching the cathode.
Global battery demand to soar
“We know that for a Li-ion battery to work, Li-ions must be able to travel between the positive and negative sides during charge and discharge cycles,” Professor Xu Zhichuan, who is also the Cluster Director of Energy Storage and Renewables & Low Carbon Generation: Solar, at the Energy Research Institute @ NTU (ERI@N).
“However, the transfer of the Li-ions also means the formation of dendrites is inevitable for current commercial Li-ion batteries.”
Global battery demand is set to grow, with electric vehicles alone requiring up to 2,700 GWh worth of Li-ion batteries a year by 2030, equivalent to some 225 billion mobile phone batteries.
Instead of preventing the formation of dendrites, Professor Zhichuan and his research team from the School of Materials Science and Engineering decided to make use of their intrinsic properties by coating an additional layer of conductive material on the separator for these dendrites to connect with.
Once the dendrites make the connection they will not be able to continue their growth further, thus preventing them from ever reaching the other side.
Zhichuan’s team has tested their technology in the laboratory on over 50 cells with different Li-ion battery compositions and no short-circuits have been detected during the charging phase even when the battery cells are used beyond their lifecycle.
The anti-short layer is a common material used in battery manufacturing and can be easily integrated into the current separator manufacturing process, making it easy for companies to adopt and scale up.
Patent-pending technology
The team estimates that the cost increase after adopting this technology would be around five per cent more than the existing production cost of a Li-ion battery.
This technology is now patent-pending and is being commercialised by NTUitive, NTU’s innovation and enterprise company.
The NTU innovation has also gained the interest of several battery technology firms.
“This technology breakthrough is of significant interest to our business in electrifying e-mobility and stationary energy storage applications that are presently heavily dependent on Li-ion batteries,” Durapower Group’s Chief Executive Officer, Kelvin Lim, said.
Dr Avishek Kumar, CEO and Co-Founder of V-Flow Tech, an energy storage technology firm, said the invention solves the most critical puzzle of thermal runaway issue in Li-ion energy storage solutions and will prove to be one of the biggest enablers for mass adoption of Li-ion energy storage technology.
The team will be further developing the technology and testing it on commercial standardised Li-ion battery cells, in partnership with interested companies.
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