ESS Partners with Alsym Energy to Deliver 8.5 GWh of Non-Lithium Battery Energy Storage Solutions

Key Terms

sodium-ion technical

A sodium-ion is a positively charged sodium atom that moves between electrodes to store and release electrical energy in sodium-ion batteries, functioning much like a lightweight marble shuttled back and forth to hold charge. It matters to investors because batteries that use sodium instead of scarce lithium can cut raw-material costs and ease supply constraints, potentially lowering manufacturing expenses and reshaping markets for electric vehicles and grid storage, albeit often with trade-offs in energy density.

thermal runaway technical

Thermal runaway is an uncontrolled, accelerating rise in temperature inside batteries, chemical systems, or equipment where heat being produced exceeds the system’s ability to shed it, often leading to fire, explosion, or permanent damage. Investors care because it creates safety recalls, regulatory scrutiny, liability and production stoppages that can sharply hurt a company’s finances and reputation — like a small spark that rapidly becomes a larger, costly disaster.

battery energy storage system technical

A battery energy storage system is a device that stores electricity for later use, much like a rechargeable battery for a phone or laptop. It allows energy generated during times of low demand or from renewable sources to be saved and released when needed, helping to balance supply and demand. For investors, it represents a way to support reliable energy flow and capitalize on the increasing demand for flexible, clean power solutions.

round trip efficiency technical

Round trip efficiency is the percentage of energy you get back from a storage system compared with the energy you put into it, after accounting for losses during charging, storing and discharging. For investors, higher round trip efficiency means more usable output for the same input cost—think of it like a rechargeable battery that keeps more of the power you charge, which boosts revenue potential, lowers operating costs and improves the value of energy storage assets.

hvac technical

HVAC stands for heating, ventilation and air conditioning — the systems that control temperature, airflow and indoor air quality in buildings. Investors care because HVAC drives operating costs, energy use, tenant comfort and regulatory compliance; like the engine and insulation of a building, efficient modern systems can lower bills, reduce repair and replacement spending, and preserve property value, while outdated units can create unexpected expenses and vacancy risk.

physics-informed ai technical

AI models that are trained not just on data but also on established physical laws and constraints, so their outputs must obey known behavior (like conservation of energy or fluid flow). For investors, this means more trustworthy and data-efficient forecasts, faster model development, and lower technical risk for companies using these models in engineering, energy, or scientific products — akin to teaching a student both facts and the rules that govern them.

ipps technical

Acronym for the Inpatient Prospective Payment System, the U.S. Medicare program that pays hospitals a set amount for each patient stay based on the diagnosis rather than reimbursing every individual service. Think of it as a flat fee for a hotel stay rather than charging separately for every meal and service. It matters to investors because changes to these rates or rules directly affect hospital revenue, profit margins, and cash flow, influencing healthcare stocks and valuations.

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Next Generation Sodium-ion Battery Solution Enables ESS Transition to a Full-Service BESS Platform Provider for Expanded Applications

Partnership Enables ESS to Enter the Short and Medium Duration Energy Storage Segment

WILSONVILLE, Ore. & MALDEN, Mass.--(BUSINESS WIRE)-- ESS Tech, Inc. (NYSE: GWH) ("ESS" or the "Company"), a leading manufacturer of sustainable, long‑duration energy storage systems (“LDES”), today announced the signing of a letter of intent for a strategic partnership with Alsym Energy, a pioneer in non-flammable, high-performance sodium-ion batteries, to add 8.5 GWh of sodium‑ion cells and modules to its portfolio.

This next‑generation battery solution is designed to address use cases traditionally served by lithium‑ion systems - and those where lithium cannot go - but without the inherent thermal run-away risks associated with lithium chemistries.

This partnership marks ESS’s entry into the short‑ and medium‑duration BESS (“Battery Energy Storage System”) segment, a market historically dominated by lithium-ion. It meaningfully expands the Company’s addressable market beyond its established position in long-duration storage. The Alsym sodium-ion technology virtually eliminates thermal runaway risk and lowers total cost of ownership. In addition, the solution does not require complex HVAC systems, demonstrates high round trip efficiency, employs fast charge and discharge capabilities and offers a simpler, safer deployment profile for customers seeking superior stationary storage solutions.

“Sodium-ion and iron flow are complementary technologies,” said Drew Buckley, Chief Executive Officer of ESS. “Alsym's sodium-ion Na-Series is an ideal solution for ESS’s short- and medium-duration applications where high power, fast cycling, and rapid response are paramount. ESS's existing Energy Base® iron flow platform is engineered for the 8–24 hour long-duration segment, where deep daily cycling, 25-year asset life, and zero capacity degradation deliver the lowest levelized cost of storage. 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.”

Randall Selesky, Chief Commercial Officer at ESS, added, “This partnership represents a major milestone in our strategy to become a full-spectrum, non-lithium solutions provider for the entire energy storage market with safer, more sustainable technologies. By combining Alsym’s high performance, non-flammable sodium‑ion technology with ESS’ systems expertise and Energy Base® long‑duration solutions, we are giving customers a clear pathway beyond lithium‑ion — without compromising performance or economics.

“Unlike lithium‑ion batteries and many other sodium-ion batteries, Alsym’s Na-Series batteries are non‑combustible and thermally stable, reducing system complexity, improving safety, and lowering total cost of ownership by reducing the need for extensive fire suppression and HVAC infrastructure. Alsym’s Na-Series has been developed using a proprietary, physics-informed AI platform for battery development that dramatically shortens the time to bring innovation to the market. The batteries utilize non-foreign entity of concern (“FEOC”) sourced materials and provide integrators and OEMs with a safe, cost-effective, supply-secure battery solution,” Selesky concluded.

Mukesh Chatter, Chief Executive Officer for Alsym Energy, commented, “ESS is a leading innovator in stationary storage, and we are very pleased to be partnering with them. As demand grows, it is increasingly clear that the industry needs solutions beyond lithium-ion to meet the speed and scale projections. By combining high performance, inherent safety, and supply chain resilience, Alsym’s Na-Series delivers that capability and ESS brings deep experience delivering grid-scale systems that maximize the value of renewable energy. Together, we are enabling a better path forward for energy storage.”

With the combined sodium-ion and iron-flow platform, ESS is positioned to support utilities, IPPs, data centers, and C&I customers seeking American-made, flexible, and future‑proof energy storage solutions across a wide range of applications.

About ESS Tech, Inc.

ESS (NYSE: GWH) is the leading manufacturer of long-duration iron flow energy storage solutions. ESS was established in 2011 with a mission to accelerate decarbonization safely and sustainably through longer lasting energy storage. Using easy-to-source iron, salt, and water, ESS iron flow technology enables energy security, reliability and resilience. We build flexible storage solutions that allow our customers to meet increasing energy demand without power disruptions and maximize the value potential of excess energy. For more information visit www.essinc.com.

About Alsym Energy

Alsym Energy is enabling a safer, scalable energy future by rethinking battery chemistry. The company's flagship Na-Series are non-flammable, high-performance, low cost sodium-ion batteries made with earth abundant materials. They are designed using a proprietary, physics-informed AI platform that enables the discovery of materials and commercially viable chemistries 10x faster than traditional, trial and error experiment-only methods. By combining DeepTech expertise in batteries with physics-informed AI, the platform is a closed-loop system that accelerates the entire battery development process, from ideation to manufacturing. Alysm’s Na-Series technology eliminates thermal runaway and allows energy storage to be deployed safely, and at scale, anywhere energy storage is needed — from data centers and industrial facilities to residential buildings, commercial real estate, mining, military installations or utility grids. Its wide operating temperature range avoids the need for HVAC systems for safety or performance, and fast charge and discharge rates allow multiple cycles per day, creating a powerful economic model for energy storage systems. Alsym Na-Series: A better battery for energy storage.

To learn more, visit: alsym.com

Forward-Looking Statements

This communication contains forward-looking statements (including within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, and Section 27A of the Securities Act of 1933, as amended) concerning the Company and other matters that involve substantial risks and uncertainties. These statements may discuss the management team’s goals, beliefs, hopes, intentions and expectations as to future plans, trends, events, results of operations and financial condition, or otherwise, based on current beliefs of the management of the Company, as well as assumptions made by, and information currently available to, the Company’s management. These forward-looking statements can be identified by the use of forward-looking terminology, including the words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “will,” “would,” or, in each case, their negative or other variations or comparable terminology may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements, which are subject to risks, uncertainties and assumptions about us, may include our anticipated growth strategies and anticipated trends in our business. Examples of forward-looking statements include, among others, statements pertaining to market opportunities for ESS’ products, pace of commercial activity, ESS product development and manufacturing, and relationships with strategic partners and customers. These forward-looking statements are based on ESS’ current expectations and beliefs concerning future developments and their potential effects on ESS. Many factors could cause actual future events to differ materially from the forward-looking statements in this communication. There can be no assurance that the future developments affecting ESS will be those that we have anticipated. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond ESS control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements, which include, but are not limited to, barriers we face in our attempts to produce our energy storage products; our products being in the early stage of commercialization and aspects of our technology not having been fully field tested; our inability to develop our business and effectively commercialize our energy storage products; our dependence on third-party suppliers; delays in our manufacturing operations; and other risks and uncertainties described more fully in the section titled “Risk Factors” in the Company’s Quarterly Report on Form 10-K filed on March 5, 2026, and the Company’s other filings with the U.S. Securities and Exchange Commission. Except as required by law, ESS is not undertaking any obligation to update or revise any forward-looking statements whether as a result of new information, future events or otherwise.

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Company 
investors@essinc.com

Investor Relations 
Chris Tyson 
Executive Vice President 
MZ Group - MZ North America 
Phone: (949) 491-8235 
GWH@mzgroup.us
www.mzgroup.us

Source: ESS, Inc.