ESS Tech, Inc. (American energy technology company) has signed a letter of intent with Alsym Energy (Massachusetts-based battery technology company) to incorporate 8.5 gigawatt-hours of sodium-ion cells and modules into its product portfolio, a move the companies say will position ESS as a full-spectrum non-lithium battery energy storage provider capable of serving customers across short, medium, and long-duration storage applications.

The agreement pairs ESS's existing iron flow technology with Alsym Energy's sodium-ion Na-Series batteries, which the companies describe as non-flammable, thermally stable, and built using materials sourced outside of foreign entity of concern designations.

The partnership marks ESS's first formal entry into the short- and medium-duration battery energy storage system segment, a market the company acknowledged has historically been dominated by lithium-ion chemistries.

Expanding Beyond Long-Duration Iron Flow

ESS, headquartered in Wilsonville, Oregon, has built its commercial identity around long-duration iron flow batteries, with its Energy Base platform designed for the eight-to-24-hour storage segment.

The company's iron flow systems use iron, salt, and water as core materials and are engineered for 25-year operational lifespans with zero capacity degradation, according to ESS.

The addition of Alsym's sodium-ion technology is intended to extend that offering into applications requiring high power output, fast charge and discharge cycles, and rapid grid response.

ESS Chief Executive Officer Drew Buckley described the two chemistries as complementary rather than competing, saying the Na-Series is suited to short- and medium-duration use cases where power density and cycling speed are the primary requirements, while iron flow remains optimized for extended daily cycling.

"Together, the two chemistries form a unified, non-lithium platform that enables ESS to meet customers' full storage needs from a single trusted provider, whether the application calls for firming renewables over a few hours, shifting energy across a full day, or pairing both within a single project to optimize economics across the full duration curve," Buckley said in the announcement.

Sodium-Ion Technology and Safety Claims

Alsym Energy, based in Malden, Massachusetts, has positioned its Na-Series batteries around what the company describes as inherent thermal safety characteristics that differentiate them from both lithium-ion and many other sodium-ion products on the market.

The batteries are described as non-combustible and thermally stable, which Alsym and ESS say reduces the need for extensive fire suppression infrastructure and complex HVAC systems at deployment sites.

ESS Chief Commercial Officer Randall Selesky highlighted the safety profile as central to the commercial proposition. He said the reduction in fire suppression and HVAC requirements lowers the total cost of ownership for customers and simplifies the overall system integration process.

Selesky also noted that the Na-Series batteries are developed using what Alsym calls a physics-informed AI platform, which the company says shortens development timelines and accelerates the introduction of new chemistries to market.

Alsym describes its AI-based development approach as a closed-loop system that integrates materials discovery with commercially viable chemistry identification at speeds it claims are ten times faster than traditional experimental methods.

The Na-Series batteries use earth-abundant materials and are produced outside supply chains linked to foreign entities of concern, a supply chain attribute that has become increasingly relevant for project developers and integrators seeking to meet domestic content and procurement requirements.

Market Positioning and Customer Targets

With the combined platform, ESS said it is targeting utilities, independent power producers, data centers, and commercial and industrial customers looking for energy storage solutions that do not rely on lithium-ion chemistry.

The company framed the partnership as enabling customers to access both short-duration and long-duration storage from a single provider, including the ability to co-locate both technologies within a single project.

Alsym Chief Executive Officer Mukesh Chatter said the scale of demand projections in the energy storage market has made it increasingly clear that lithium-ion alone cannot satisfy the industry's needs.

He described the combination of safety, performance, and supply chain resilience in the Na-Series as the capability the market requires, and pointed to ESS's grid-scale systems experience as the integration foundation needed to deliver that technology at scale.

The 8.5 GWh volume commitment outlined in the letter of intent represents a significant addition to ESS's addressable market. The company's current Energy Base iron flow platform serves the long-duration segment, and the sodium-ion agreement opens commercial access to shorter-duration applications that ESS had not previously addressed with its own product line.

Strategic Context

The announcement comes as the broader energy storage industry faces ongoing scrutiny over lithium-ion battery safety, supply chain dependencies, and the concentration of lithium processing capacity in countries subject to FEOC restrictions.

Both ESS and Alsym framed their partnership explicitly in terms of offering an alternative pathway to project developers and system integrators who are seeking to reduce exposure to those risks.

ESS, which trades on the New York Stock Exchange under the ticker GWH, was founded in 2011. Alsym Energy describes itself as a pioneer in non-flammable battery technology and says its development platform combines deep materials science expertise with AI-driven discovery tools to bring new battery chemistries to commercial readiness.

Powering Smarter Decisions Across the Global Utilities Landscape

When capital investment in utilities infrastructure spans continents and timelines stretch across decades, the cost of incomplete intelligence is simply too high to ignore. Organizations operating across markets worldwide need more than fragmented data — they need a single, reliable source of truth that keeps pace with an industry in constant motion.

The Global Project Tracking (GPT) platform by Blackridge Research was built precisely for this challenge, aggregating utilities project data from markets worldwide into one continuously updated environment.

Whether you are monitoring grid modernization initiatives, water treatment expansions, or large-scale energy transition projects, the platform delivers the depth and breadth your strategic planning demands.

From early-stage pipeline opportunities to fully completed developments, every phase of a project's lifecycle is covered — giving utilities professionals, investors, and contractors the visibility they need to act with confidence and precision.

• Upcoming Projects

• Tender Notices

• Contract Awards

• Projects Under Construction

• Completed Projects

Discover how the Global Project Tracking (GPT) platform by Blackridge Research can sharpen your competitive edge across markets worldwide — Book a Free Demo with our team today and explore the full scope of utilities intelligence available to you.