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Rechargeable lithium-ion batteries are the mobile power sources of choice today, used in everything from laptop computers, smart phones and even electric cars. For years, though, they’ve been known to overheat and, at times, catch fire.
This was made painfully clear in January, when the lithium-ion batteries in Boeing’s newest commercial aircraft, the Dreamliner, caught fire, leading to a brief grounding of the planes until the fire hazard was resolved.
This is much less likely to happen with batteries made with magnesium, however. And magnesium ions in the batteries’ electrolytes, which transmit electricity, carry a double positive charge, increasing the device’s energy density, or the amount of electricity the battery can store.
Still, no one’s been able to make a commercially viable magnesium-ion battery, mostly because of fears of magnesium’s high reactivity with other materials in a battery, which would interfere with the movement of the ions through the electrolyte.
Liwen Wan and David Prendergast of the Lawrence Berkeley National Laboratory in California conducted computer simulations that show this reactivity actually isn’t a problem. In the October issue of the Journal of the American Chemical Society, they write that the interference is much lower than had been feared, and therefore that a magnesium-ion battery would be more efficient than expected.
On that basis, researchers at the National Cheng Kung University (NCKU) in Taiwan improved the stability of the magnesium-ion battery. Fei-Yi Hung, one of the three leaders of the team, told the online publication EnergyTrends that they accomplished this in part by turning to a new technology that uses electrodes made of magnesium membranes and magnesium powder.
The idea of a magnesium-ion battery has long been attractive not only because it’s less likely to overheat, Hung said, but also has up to 12 times the energy density of a lithium-ion battery and its charge-discharge efficiency is 5 times greater.
To illustrate magnesium’s superiority over lithium, Hung said, an electric bicycle with a fully depleted lithium-ion battery needs about three hours to recharge fully. If equipped with a magnesium battery, he said, the process would take a mere 36 minutes.
Also, he said, lithium batteries ordinarily can’t operate properly in temperatures below 5 degrees Fahrenheit. But if these lithium batteries were coated with a film of magnesium, they work fine at temperatures as low as 22 degrees below zero Fahrenheit and as high as 131 degrees Fahrenheit.
Only two problems remain, Hung said. First, negative electrodes high-storage rechargeable batteries normally are made from graphite, which is inefficient at storing electrical energy. Second, graphite is derived from processed petroleum coke, a fossil fuel that emits greenhouse gases.
Hung said his team hopes to replace the graphite with a more efficient material that “would be more environmentally friendly.”
By Andy Tully of Oilprice.com
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Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com