COSMOS LAB, a Seoul-based developer of zinc-bromine batteries, is negotiating roughly $15.6 million in Series A financing from existing backers iM Investment Partners and Rising S Ventures, according to DealSite. The three-year-old company is building rechargeable cells that replace flammable lithium compounds with ordinary water, a design choice aimed squarely at the data center and grid storage markets now grappling with fire safety concerns.
The round is slated to close in early July, DealSite reported in June, with about 20 billion won committed and final terms under negotiation. It follows a 4.8 billion won Pre-A2 raise last year from High Investment Partners, Gyeongnam Venture Investment, and a handful of other Korean funds. But perhaps the most telling signal came not from venture investors but from SoftBank, which opted to become a manufacturing partner rather than simply write a check.
In May, the Japanese conglomerate announced plans to mass-produce COSMOS LAB's zinc-halogen batteries domestically, with production targeted around fiscal 2027 or 2028. SoftBank framed the partnership as essential infrastructure for its expanding AI operations, where battery fires pose an unacceptable risk to server uptime and multimillion-dollar hardware. The batteries will initially feed SoftBank's own data centers before potentially reaching energy storage systems and backup power installations.
"It is a very important step to apply the original technology to the actual global market," a COSMOS LAB official told Maeil Business in May. The understatement was deliberate. Landing a customer of SoftBank's scale before most hardware startups have shipped their first commercial units is the sort of validation that rewrites pitch decks.
SoftBank's announcement emphasized the aqueous electrolyte chemistry: "Its key feature is its ability to eliminate fire risks associated with the currently dominant lithium-ion batteries." The company is targeting gigawatt-hour production volumes, a scale that reflects both the voracious energy appetite of AI infrastructure and a bet that fire-safe alternatives will command a premium as regulators and insurers scrutinize lithium-ion deployments more closely.
The Chemistry Beneath the Hype
COSMOS LAB's cells pair a zinc anode with a halogen cathode submerged in water-based electrolyte. That formulation sidesteps the thermal runaway problem that has plagued lithium batteries, where internal short circuits can trigger self-sustaining fires hot enough to melt metal. According to an April report in ETNews covering government commercialization grants, the company claims to have demonstrated 1,000 charge cycles on a 15-ampere-hour cell at room temperature.
"Cosmos Lab's water battery is inexpensive because it does not use rare minerals such as lithium, nickel, or cobalt," CEO Ju-Hyuk Lee said at CES 2024, as quoted by The Asia Business Daily. The aqueous design, he said, reduces fire or explosion risk to "close to zero."
The startup manufactures both prismatic and pouch cell formats. It holds a Patent Cooperation Treaty application for zinc-bromine electrolyte formulations, published in 2024, though the intellectual property landscape in aqueous batteries is crowded. U.S.-based Eos Energy secured a $303.5 million conditional loan guarantee from the Department of Energy in February 2024 for its own zinc-hybrid cells. Eos published third-party fire test results in June showing no thermal runaway, no sustained combustion, and no cell-to-cell propagation.
Australian firms Redflow and Gelion also field zinc-bromine systems for stationary storage. Academic literature generally credits the chemistry with cost advantages and inherent safety but notes persistent technical headaches: zinc dendrite formation that can short cells, bromine migration across separators, and energy density that lags lithium-ion by a meaningful margin.
Eighteen People, Big Ambitions
Lee co-founded COSMOS LAB in 2021 with Jo In-Seong after stints at the Korea Institute of Energy Research. He holds degrees in bio and chemical engineering from KAIST, the elite technical university that has seeded much of Korea's recent wave of deep-tech startups. The company counts 18 employees as of June, according to startup database THE VC.
Early backing came from FuturePlay in a 2021 seed round, followed by a Pre-A1 in 2022 from Korea Institute of Science and Technology Holdings, Korea Credit Guarantee Fund, and MYSC. The Bell reported that last year's Pre-A2 funds were earmarked to push pilot output to megawatt-hour-class cell volumes, a necessary stepping stone before SoftBank's gigawatt-hour ambitions become feasible.
Lee has framed the manufacturing push as Korea's "first attempt at a next-generation mass-production process" for batteries, aiming to "design and produce a completely new and competitive battery product." It's the sort of language that reflects both genuine technical optimism and the pressure to carve out differentiation in a sector where Chinese manufacturers dominate cost curves and Western startups chase performance specs.
SoftBank has designated Korean integrator DeltaX to pair COSMOS LAB's cells into full battery systems. The production timeline targets fiscal 2028 for initial output, with SoftBank's AI data centers as anchor customers before potential expansion into grid, industrial, and residential markets.
Whether water-based batteries will claim a meaningful share of the storage market remains an open question. But for now, COSMOS LAB has a manufacturing partner with deep pockets, a use case with genuine safety requirements, and just enough runway to find out.
