Engineering researchers at the University of Alberta have found a way to make rechargeable, environmentally friendly water-based batteries perform far better than those currently available.
The idea of using batteries that use a water-based electrolyte solution — rather than the organic solvents used in lithium batteries — has been around since the 19th century.
Invented in 1859, the lead-acid "aqueous" battery used to start most internal combustion vehicles is one example still used today. But aqueous batteries don't have the energy density, voltage and storage capacity to power electric vehicles or to adequately store energy produced by renewable technologies like solar panels and wind turbines.
On the other hand, lithium-ion batteries — with their high energy density, long life, charging speed and lightweight construction — have their own drawbacks. Chief among them are their high cost and the risk of fire and even explosion.
Materials scientists Xiaolei Wang and his student Zhixiao Xu in the Department of Chemical and Materials Engineering have begun to close the proficiency gap, finding a way to make rechargeable aqueous batteries perform far better than those currently available.
"Aqueous batteries are cheaper, easily disposed of because we use just water, and aren't toxic or flammable," says Wang. The results of the breakthrough were published recently in Nature Communications.
Batteries made of organic materials, like the aqueous variety, tend to conduct electricity poorly, so that a lot of extra carbon has to be added to make them work, says Wang, meaning there is less room for materials that store energy. They are also low-density and don't hold much energy.
The key to the team's breakthrough is in the design of electrode materials, where the battery's energy is stored. In an aqueous battery, the transfer of electrical current between the cathode and anode is facilitated by a water-based electrolyte, as opposed to an organic solvent used in a lithium-ion battery.
By constructing what they call pressurized organic electrodes, Wang's team achieved increased energy density, chemical reactivity, electronic conductivity, thermal stability, mechanical strength and adhesive property.
"As a result they charge faster, last longer, and store much more energy, now outperforming almost all other organic batteries," says Wang.
Wang's results were based on the lab performance of a coin-size battery and a larger battery pack about the size of a small sandwich bag, says Wang, adding that more work needs to be done to make larger batteries viable for commercial use.
The next phase, he says, is to find an industry partner willing to invest in upscaling his technology.
"We aim to build these batteries for large-scale (industrial) energy storage. But if we can reach comparable performance for electric vehicles with lower cost and safety concerns, why not?"
