US battery companies are focusing on sodium-ion technology, with some currently relying on China-sourced cells for their products. San Diego-based Unigrid, which sells nine kilowatt-hour home batteries, has seen increased demand from European homeowners looking to store power. The company has shipped 100 units and anticipates shipping 1,000 by the end of 2026.
Unigrid's batteries incorporate chromium-3 in their cathode. Prof Dame Clare Grey of the University of Cambridge noted that chromium-3 may form chromium-6, a toxic, cancer-causing material, under certain conditions. Ivana Hasa at the University of Warwick agreed this is possible at very high states of charge, though mitigation through voltage control is possible. Unigrid co-founder Darren Tan stated that concerns are "overblown" and that the battery has passed European certification and safety tests, with third-party tests unable to produce chromium-6.
Other companies are also entering the sodium-ion market. Seattle-based Emerald Battery Labs is developing 12-volt auxiliary batteries for vehicles, currently using China-sourced cells. California and Colorado-based Peak Energy announced a partnership with General Motors in June, aiming to establish a US supply chain for sodium-ion batteries and launch a production facility in Michigan by the end of 2028.
Sodium-ion batteries are seen as a potentially cheaper alternative to lithium-ion, with some suggesting costs could reach as low as $30 per kilowatt-hour, though analysts indicate this may be years away. While not as energy-dense as lithium-ion, their reliability has reportedly increased, making them suitable for grid storage applications.