The magic bullet is sulfur, apparently. Sony’s new batteries are based on a hybrid lithium-sulfur design: they swap the plain negative electrode in lithium-ion batteries for a sulfur-based one, and retain the lithium-based positive electrode. That has allowed the company to dramatically increase energy density — up to 1,000Wh/L, or 40 percent larger than your run-of-the-mill, 700Wh/L lithium-ion battery.
Another important benefit of sulfur? It’s cheap; a spokeswoman for Oxis Energy, an energy startup that’s also refining lithium-sulfur tech, told PV Magazine that “the overall cost of the materials is less” and that the “predicted costs of lithium sulfur when production is ramped up is lower than competing lithium ion technologies.”
Lithium-sulfur batteries aren’t new. An international team of researchers from South Korea and Italy produced a 750mAh rechargeable sulfur-lithium ion battery earlier this year. Oxis intends to commercialize its sulfur-lithium batteries in 2016. And Tuscon, Arizona-based company Sion Power has partnered with Airbus to test 350 Wh lithium-sulfur power packs.
But despite their promise, lithium-sulfur batteries aren’t without their inherent flaws — according to the American Institute of Physics, sulfur’s tendency to dissolve into the battery’s liquid electrolyte means the batteries don’t typically last long.
Sony has presumably developed a countermeasure, possibly involving graphene. When used as a physical barrier inside sulfur-lithium batteries, the highly conductive material facilitates the transfer of electrons while preventing exposure to the electrolyte.
And Sony’s got a backup plan, too: magnesium-sulfur batteries. These eschew the lithium altogether for a denser, more efficient, and less fire-prone cell than can be offered by lithium-ion designs. Unlike sulfur, magnesium doesn’t degrade in the electrolyte, and the element is cheap and abundant. But magnesium-based batteries have their own Achilles heel: low capacities and low voltage.
That’s likely why Sony’s sticking with lithium-sulpher for now. It told Nikkei that if all goes according to plan, it’ll start mass-producing laminated sulfur-lithium batteries — the sort bound for consumer electronics such as smartphones, laptops, and digital cameras — within the next few years.
