Exploding lithium-ion batteries may soon be a thing of the past with the development of a safer, lighter version that matches the power level needed to run everyday devices.
Lithium-ion rechargeable batteries, which are found in smartphones, e-cigarettes, hoverboards and electric vehicles, earned their reputation for volatility after a series of high-profile explosive failures that led to the recall of Samsung's Galaxy Note 7 smartphone.
The main problem with existing lithium-ion batteries is the conducting liquid — through which ions are exchanged between positive and negative electrodes — is flammable. So, if the battery overheats or shorts out, there's a risk the liquid can ignite.
Now a team of researchers from the University of Maryland and the US Army Research Laboratory have found a way around this, by developing a battery that contains a water-based salt solution instead of a flammable liquid.
They're not the first to try this approach, but until now, these water-solution-based lithium-ion batteries have only had limited power.
In a paper published today in Joule, they report a new lithium-ion battery that has succeeded in generating four volts — the amount generated by existing lithium-ion batteries used in everyday household products — but without the safety risks.
They achieved this by using an extremely salty water-based solution, and developing a special coating that protects the battery's electrodes from direct interaction with the water-based solution.
This is important for the battery's safety, because lithium itself can react violently when exposed to water.
"Lithium metal is supposed to react with water really quickly, but in this water … the activity is significantly reduced," said researcher Professor Chunsheng Wang from the University of Maryland.
"So the water in salt electrolyte reacts with lithium metal but really slow."
The special coating on the surface of the electrode also repels water molecules and is self-healing, which means even if the battery is damaged, a violent reaction between the electrodes and the solution is much less likely.
The reduced reactivity also means the battery can be lighter, said lead author Dr Chongyin Yang, a postdoctoral researcher at the University of Maryland.
"It's much better because it's high safety so we can even remove some safety control management components of the battery that we are using in the commercial ones," he said.
Exciting but is it commercially viable?
Commenting on the study, Queensland University of Technology associate professor Anthony O'Mullane said the new design was an exciting development in the world of lithium-ion batteries, particularly reaching the four-volt mark.
"That's really pushing the chemistry of the battery in terms of that energy difference between the anode and the cathode," he said.
"The way they've protected their electrode definitely helps."
However he pointed out the study only tested the battery up to 50 cycles of discharge and recharge, but to be commercially viable it needed to prove its worth over thousands of cycles.
If the new battery design makes it through the next stage of development, he said it would most likely be used in electronic devices, such as mobile phones and laptops, and possibly electric cars.