Sodium-ion isn’t quite ready for widespread use, but one startup thinks it has surmounted the battery chemistry’s key hurdles.
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If there’s one thing holding batteries back, it’s cost.
The most widespread type of battery, lithium-ion, still costs around $140 per kilowatt-hour for a pack. While that’s low enough to have triggered quickening adoption of electric vehicles, even the cheapest lithium-ion chemistries are still too expensive to put a big battery in every home to protect against blackouts.
Instead, manufacturers have started to explore sodium-ion batteries, not as a replacement, but as a complement to lithium-ion.
“When produced at the same scale, sodium-ion should be about half of where lithium-iron-phosphate is in terms of cost to produce because the raw materials are a hundred times cheaper,” Darren Tan, co-founder and CEO of Unigrid, told TechCrunch.
Despite the promise, sodium-ion isn’t quite ready for widespread use. Batteries made with it are not very dense, making them too large and too heavy for EVs. Plus, many variants behave differently from lithium-ion when they’re charging and discharging, meaning packs made with sodium-ion need new electronics to manage them.
Tan’s startup thinks it has solved those problems by using a new chemistry based on sodium-chromium-oxide in one half of the battery and tin in the other (though Tan emphasizes the company can substitute other materials on either side). Unigrid’s batteries don’t take up any more space than a lithium-iron-phosphate cell, sometimes less. Plus, their power output mimics that of lithium-ion so the company can use the same electronics, and they are made with widely available materials. “Chromium is produced at twice the quantity of copper each year,” Tan said.
The company was borne out of Tan’s research at UC San Diego, where he was a doctoral student under Shirley Meng, a prolific materials scientist who focuses on energy storage. Their goal wasn’t just to create a cheaper battery, but also one that’s safer.
Unigrid’s batteries won’t go into thermal runaway and catch fire until the internal temperature rises to several hundred degrees Celsius, Tan said. “Sodium-ion should not just be like lithium-ion, it should be way safer such that we can put it in buildings, hospitals, data centers, so we can achieve widespread distributed energy storage,” he said.
To deliver that many batteries, Unigrid isn’t going to be building its own factories. Instead, it’ll be working with smaller battery manufacturers that exist simply to make other company’s designs. Think of them like TSMC, which produces computer chips for companies like Apple and Nvidia, albeit much smaller in scale. Unigrid’s chemistry works on their existing equipment, and Tan said there’s enough spare capacity at these facilities to produce batteries on a megawatt-hour scale.
Unigrid’s first market will be energy storage for buildings and small campuses, but it’s also looking to supply manufacturers of so-called light EVs, things like scooters, motorcycles and tuk-tuks. Small vehicles like these are popular in India and Southeast Asia, where the intense heat can make lithium-ion batteries prone to overheating. “There’s a huge opportunity there where the climate is very warm and lots of battery fires occur,” Tan said.
To get its sodium-ion batteries into production, Unigrid has raised a $12 million Series A. The round was led by Transition VC and Ritz Venture Capital with participation from Union Square Ventures and Foothill Ventures.
Tan hopes that Unigrid will be selling cells sooner than later. “We really wanted to do something that could make a more immediate and shorter term impact, something that we could get into the market in the next five years,” he said.
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