If there's one thing that's holding back batteries from becoming more widespread, it's cost.
Lithium-ion, the most popular type of battery, still costs about $140 per kilowatt-hour per pack, low enough to accelerate the adoption of electric vehicles, but even the cheapest lithium-ion chemistry is still too expensive to install large batteries in every home to protect against power outages.
Instead, manufacturers are beginning to research sodium-ion batteries as a complement to lithium-ion, rather than a replacement.
“At the same scale, sodium-ion should cost about half as much to produce as lithium iron phosphate, because the raw materials are 100 times cheaper,” Unigrid co-founder and CEO Darren Tan told TechCrunch.
Despite the high expectations, sodium-ion isn't ready for widespread adoption yet: Batteries made with sodium-ion aren't dense enough, making them too big and heavy for EVs, and many varieties behave differently than lithium-ion when charging and discharging, so sodium-ion packs require new electronics to manage them.
Tan's startup believes it has solved these problems by using a new chemistry based on sodium chromium oxide on one side of the battery and tin on the other (though Tan stresses that either side could be replaced with other materials). Unigrid's batteries take up the same space as lithium iron phosphate batteries, and in some cases even less. Plus, their power output is similar to lithium-ion, allowing the company to use the same electronics. And they're made from widely available materials: “Chromium is produced in twice the amount of copper each year,” Tan says.
The company was born out of Tan's work as a PhD student at the University of California, San Diego, under the mentorship of Shirley Meng, a renowned materials scientist specializing in energy storage. Their goal was not just to make cheaper batteries, but to make them safer as well.
Tan said Unigrid's batteries would not experience thermal runaway and catch fire until their internal temperatures rose to several hundred degrees. “Sodium-ion is not like lithium-ion, and it's much safer to put in buildings, hospitals and data centers, enabling widespread distributed energy storage,” he said.
To supply so many batteries, Unigrid won't build its own factories. Instead, it will work with smaller battery manufacturers that exist only to produce other people's designs, like TSMC, which makes computer chips for companies like Apple and Nvidia, but on a much smaller scale. Unigrid's chemistry works with existing equipment, and Mr. Tan says those facilities have enough spare capacity to produce megawatt-hour-scale batteries.
Unigrid's first market will be energy storage for buildings and small campuses, but it's also looking to supply makers of so-called light electric vehicles like scooters, motorcycles and tuk-tuks. Such small vehicles are popular in India and Southeast Asia, where hot weather can easily overheat lithium-ion batteries. “There's a big opportunity in this region because the climate is so warm and we have a lot of battery fires,” Tan said.
Unigrid has raised $12 million in Series A funding to begin production of its sodium-ion batteries. The round was led by Transition VC and Ritz Venture Capital, with participation from Union Square Ventures and Foothill Ventures.
Tan expects Unigrid to start selling the cells soon. “We really wanted to do something that would have a more immediate, short-term impact, something that we could bring to market within the next five years,” he said.