Safer solid-state batteries may be on the horizon

A team of scientists from Australia and America have developed a non-flammable electrolyte material for sodium batteries, which are claimed to be safer and cheaper than their lithium-ion brethren.

Liquid electrolytes currently used in lithium and sodium batteries can be flammable if exposed to particular conditions. Therefore, they can pose a safety risk for applications such as in electric vehicles.

Now, a team of researchers from Deakin University’s Institute for Frontier Materials has been working on a solid polymer electrolyte material that replaces the flammable solvents. These developments may serve as a pathway towards a safer form of battery.

An important component in the electrolyte was developed by Dr Cheng Zhang and Professor Andrew K Whittaker from the University of Queensland’s Australian Institute for Bioengineering and Nanotechnology. Researchers from the University of Illinois Chicago and the University of California Santa Barbara also contributed to the research.

“Most industries that develop sodium batteries generally use carbon-based electrode and liquid electrolyte, which has low capacity and also can fuel a fire if the battery overheats,” said Dr Xiaoen Wang, who is leading the research.

“We are taking a different approach, using reactive sodium metal as an anode to increase battery capacity and in the process are developing safer electrolytes to ensure the safety of sodium batteries.”

The researchers have stated that this is the first time that a fluorine-containing polymer has been used in solid-state sodium batteries before, with its use allowing them to be solvent-free and therefore less likely to be set alight spontaneously.

Additionally, one particular advantage of sodium batteries is that they have a low production cost, with sodium being plentiful and cheap.

“As lithium could become a rare commodity, the price of lithium batteries is high, while on the other hand, sodium resources are more abundant,” Wang said. “Our polymer will support the use of sodium batteries, which are low-cost when compared to lithium batteries.”

The use of the electrolyte material is helping to counteract another problem of sodium-based batteries, which is their reduced lifespan and lower energy density; by adopting it the scientists have found that their batteries have been able to reach 1000 cycles, which is comparable to a lithium battery.

Having done small-scale testing, the researchers are continuing their research, and larger models and prototypes will be moved ahead with soon. They are also hoping to utilise the batteries in solar energy storage or for electric cars in the future.

The full paper describing the electrolyte material is available from the journal Nature Materials.

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