To build a better battery, problems in materials science, chemistry, and manufacturing must be solved. We regularly report on work in the former two categories, but we get a slew of complaints about our inability to deal with the third: figuring out how companies manage to find solutions to science and turn them into usable products. So it was exciting to see that a company called StoreDot, which claimed to be developing a battery that could charge electric vehicles for five minutes, appeared to be ready to speak to the press.
Unfortunately, the response to our inquiries fell short of our hopes. "Thank you for your interest," was the answer. "We are still in pure R&D mode and cannot provide any information or answer any questions at the moment." Apparently the company gave The Guardian exclusive and didn't speak to anyone else.
Unimpressed, we've since pulled through all of the information we could find on the StoreDot website to figure out roughly what they were doing, and from there we've gone backwards to find research we've covered before and that related could stand. What follows is an attempt to create a picture of the technology and the challenges that a company must face in order to use research concepts and manufacture products from them.
The need for speed
To some extent, StoreDot uses ideas that have been floating around for years in research labs and startups, but there is some risk involved in using those ideas in a way that is different from their obvious promise. The bet that StoreDot makes is that the absolute charging area of an electric vehicle doesn't matter. That's how quickly you can expand this area. While research is being made into technologies that allow greater capacity in lithium-ion batteries, it is turning around and sacrificing some of that capacity to speed up charging.
In other words, the bet is that people would rather add 300 km to their car's range in five minutes than have a 600 km car that takes an hour to fully charge.
What does this bet mean at the hardware level? They are mainly determined by thermal management. As anyone who has a rechargeable laptop plugged in while sitting on their lap knows, charging a battery generates a lot of heat. Faster loading creates even more. To deal with this heat, StoreDot essentially produces a diffuse battery with plenty of space between each cell, as you can see at the four-minute mark of this video (embedded below). There are significant gaps in the cells and holes in the battery case that allow air to flow between them. It charges in a stand with fans that push air through the battery to keep heat under control.
Anyone could do this with existing battery technology, but the cost is very obvious: a much lower energy density, which means a battery has to be much larger to hold the same amount of charge. StoreDot compensates for this by working on a technology that enables a much higher charge density, which offsets the lower material density. In the end, the battery should contain similar amounts of charge per volume as existing batteries, although there is less battery material.