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Researchers have proposed a new lithium-oxygen battery technology that could make long-distance electric cars (and smartphones that don't need recharging every day) a reality.
Lithium-air or lithium-oxygen batteries hold the potential for between 5-15 times the efficiency of existing lithium-ion batteries for electric cars, but have seen a number of technological challenges hindering progress - primarily that nearly a third of the energy is still being wasted as heat, and they don't tend to last very long.
Ju Li, professor of nuclear science and engineering at the Battelle Energy Alliance and MIT, led the study, along with Zhi Zhu and five other researchers from MIT, Argonne National Laboratory and Peking University.
The new approach, outlined in the journal Nature, results in a 'nanolithia cathode' battery, which is more versatile and side-steps a few of the key issues with Lithium-oxygen batteries, such as needing other systems to keep away carbon dioxide and water.
Existing Lithium-oxygen batteries draw in air to cause a chemical reaction (while the battery is being used) and this is then released again to reverse the action and recharge the battery. It's that requirement to have an internal and external air flow process that allows the ingress of carbon dioxide and water. To get around this, the researchers devised a method of discharging and recharging without ever needing to let oxygen return to its gaseous form, which means no need for pumps or membranes.
"Instead, the oxygen stays inside the solid and transforms directly between its three redox states, while bound in the form of three different solid chemical compounds, Li2O, Li2O2, and LiO2, which are mixed together in the form of a glass," the team wrote in their research paper. "This reduces the voltage loss by a factor of five, from 1.2 volts to 0.24 volts, so only eight per cent of the electrical energy is turned to heat."
The end result is faster charging and more efficient batteries, due to lower heat wastage. Li also claimed the batteries could prove to have a much longer life than current lithium-ion models as they're protected from overcharging through the chemical reaction's natural process; once charged, it shifts to a different form to prevent overcharging.
"We have overcharged the battery for 15 days, to a hundred times its capacity, but there was no damage at all," Li said.
The team wants to move to produce a practical prototype within a year and have them in the hands of manufacturers within 18 months. The group told WIRED that it had just renewed its provisional patent application and is now seeking investment to bring it to fruition. The researchers added the technology could "certainly fit" in a smartphone.
A number of other research groups have also proposed improvements to lithium-oxygen batteries (or, indeed, using molten metals), as well as ways to make existing lithium-ion batteries far cheaper.