The useful question is what changes for users, developers or buyers, and whether the announcement stays industry context or becomes something people can actually use.

Form Energy announced on December 12, 2024, that its iron-air battery system completed UL9540A safety testing, meeting the industry’s highest safety standards without flame or thermal event propagation. The tests simulated fault and abuse conditions known to trigger thermal runaway in lithium-ion batteries, including extreme scenarios like continuous overcharging and short-circuit failures. Across all simulations, the cells remained stable with no uncontrolled heating, dendrite formation, or fire, demonstrating robust safety design. The results eliminate the need for additional module or system-level testing, underscoring the technology’s inherent safety.

Matthew Paiss, Technical Advisor at Pacific Northwest National Laboratory, stated that UL9540A cell-level testing represents a critical safety benchmark, and chemistries passing without thermal runaway signify a significant safety advantage. Form Energy’s iron-air cells were subjected to multiple short-circuit failure modes during charging and discharging, yet maintained stability under all conditions. The company emphasized that the testing exceeded standard lithium-ion protocols to evaluate potential failure modes unique to iron-air technology. These outcomes validate the system’s compliance with stringent safety requirements.

William Woodford, Co-founder and CTO of Form Energy, highlighted the milestone as a testament to the team’s innovation in developing a multi-day energy storage solution with exceptional safety performance. The iron-air system operates on reversible rusting, using iron, water, and air, and avoids heavy or rare-earth metals. Approximately 80% of components are sourced domestically in the United States, aligning with sustainability goals. The technology is designed for inter-day energy storage, contrasting with lithium-ion’s intraday applications, and delivers low-cost, clean electricity when needed.

The UL9540A test results confirm that Form Energy’s iron-air batteries can be deployed without fireproof barriers, simplifying installation and reducing costs compared to lithium-ion systems. This distinction further differentiates iron-air technology from conventional solutions, reinforcing Form Energy’s mission to provide safe, reliable, and sustainable energy storage. The milestone marks a significant step forward in advancing grid security and resiliency with a technology built from abundant, low-cost materials.