US sodium-ion start-ups pursue domestic production while relying on Chinese cells

Unigrid and other US sodium-ion battery start-ups are pursuing home, vehicle and grid storage markets, but their route to domestically made cells is still taking shape. In a report published on 29 September, the BBC said Unigrid, Emerald Battery Labs and Peak Energy currently rely on cells sourced from China, even as they describe plans for US production. The distinction matters for customers and policymakers weighing whether a growing market for sodium-ion storage will also create a domestic supply chain.

The companies are at different points. Unigrid says it has shipped home batteries; Emerald is developing vehicle auxiliary batteries; and Peak is working with General Motors on a US supply chain for large-scale storage, according to the BBC. None of those accounts establishes that the three are already making the sodium-ion cells they use in the United States.

Unigrid's home batteries and imported cells

San Diego-based Unigrid sells a nine kilowatt-hour home battery. Chief executive Darren Tan told the BBC that the company had shipped its first 100 units and expected to ship 1,000 before the end of the year. He said it had received requests from Spain, France, Germany and the Netherlands, where households were interested in storing electricity bought at lower rates for use during hot periods. The shipment count, forecast and explanation of demand are Tan's account.

The cells in Unigrid's current battery come from China, the BBC reported. Tan said the company could use US-made cells later, depending on cost. That leaves domestic sourcing as a possible future choice, rather than a feature of the units it is shipping now. The BBC did not establish a date for such a switch or identify an operating US cell supplier for Unigrid.

Safety questions depend on battery chemistry

Unigrid's cathode contains chromium-3, which makes its safety discussion specific to that design. Cambridge battery scientist Dame Clare Grey told the BBC that chromium-3 could form toxic chromium-6 under certain conditions. University of Warwick researcher Ivana Hasa said formation was possible at very high states of charge, while control of the battery's voltage could mitigate the risk. The concern should not be treated as a finding about every sodium-ion battery.

Tan disputed the extent of the concern. He told the BBC that Unigrid's battery had passed certification and safety tests for sale in Europe and was undergoing evaluation for the US market. He also said third-party attempts to produce chromium-6 through overcharging had failed. Those are the company's statements; the BBC report did not publish the underlying test reports. Hasa described the safety tests reported for the cell chemistry as promising, while also warning that sodium-ion batteries carry some fire risk.

Emerald and Peak pursue different markets

Seattle-based Emerald Battery Labs is developing 12-volt auxiliary batteries for vehicles. Its chief executive, David Bell, told the BBC that its initial product uses China-sourced sodium-ion cells and is being supplied to unnamed US commercial fleets. He said the company's next goal was to develop anodes for US-produced cells. The report did not specify a production date for those cells, so the anode work remains a development goal rather than evidence of domestic manufacturing.

Peak Energy, based in California and Colorado, is targeting storage for electricity grids. The BBC reported that Peak and General Motors announced a partnership in June to develop a US sodium-ion supply chain. Peak co-founder Cameron Wiles said the company hoped to help GM launch a Michigan production facility by the end of 2028. His date is a target for a future facility, not a reported start of commercial production.

Peak also relies on China-sourced cells for its first installations, according to the BBC. That mirrors the gap between US product development and cell manufacturing described by Unigrid and Emerald, although the firms serve different markets. The BBC's accounts identify ambitions to change the supply chain; they do not verify that these companies have already replaced their imported cells with domestic ones.

Why large-scale storage draws interest

Sodium-ion batteries generally store less energy for a given size or weight than lithium-ion batteries, the BBC reported. That makes compact devices such as smartphones a less likely destination for the technology and helps explain the emphasis on home and grid storage, where size and weight can be less restrictive. Battery design still matters: the term sodium-ion covers different choices of cathode, anode and electrolyte, with different implications for performance and safety.

Industry analyst CRU Group offers a cautious view of the economics. Its September analysis estimated that sodium-ion storage systems in China cost 20% more than LFP systems in 2026, partly because lower energy density increases equipment and installation costs. That is CRU's modeled estimate for China, not a measured cost for the US projects in the BBC report. CRU nevertheless identified uses with a low tolerance for fire risk, including data-centre backup, as possible markets.

CRU also said sodium-ion supply chains remain highly concentrated in China. It described Peak's collaboration with GM as the only planned US gigafactory in its analysis and said sodium-ion projects outside China remained years from production. The assessment helps explain why announcing a US battery product or factory plan does not, by itself, establish that locally sourced cells are available at scale.

The milestones still ahead

The next steps differ by company. Unigrid would need to secure an acceptable US cell source if it chooses to switch from Chinese cells. Emerald's stated work on anodes would need to advance to cells made in the US. Peak and GM would need to turn their proposed supply chain and Michigan facility into production. The BBC report gives a company target for Peak's Michigan facility, but it does not establish completed domestic cell manufacturing for any of these three companies.

Their plans also leave open what domestic sourcing would cover. A cell made in the United States and a cell made entirely from US-sourced materials are different claims. The BBC report identifies imported cells in use today and possible future US production, but does not document a fully domestic materials chain for the featured companies. For now, the clearest measure of progress is the distinction between batteries reaching customers, component development, and factories that have yet to begin production.