sciencehabit writes: Industrial-scale batteries, known as flow batteries, could one day usher in widespread use of renewable energy—but only if the devices can store large amounts of energy cheaply and feed it to the grid when the sun isn't shining and the winds are calm. That's something conventional flow batteries can't do. Now, researchers report that they've created a novel type of flow battery that uses lithium ion technology—the sort used to power laptops—to store about 10 times as much energy as the most common flow batteries on the market. With a few improvements, the new batteries could make a major impact on the way we store and deliver energy. The research, from the National University of Singapore, has one big flaw in particular: speed. It's 'very innovative' work, says Michael Aziz, a flow battery expert at Harvard University. But he adds that even though the novel battery has a high energy density, the rate at which it delivers that power is 10,000 times slower than conventional flow batteries, far too slow for most applications. Wang and his colleagues acknowledge the limitation, but they say they should be able to improve the delivery rate with further improvements to the membrane and the charge-ferrying redox mediators.