ESS Tech sodium-ion batteries are set to expand the company’s energy storage portfolio in the United States. ESS Tech plans to add 8.5 GWh of U.S.-made sodium-ion cells and modules through a letter of intent with Alsym Energy. As a result, the company will move beyond long-duration storage and target short- and medium-duration storage with a broader non-lithium offering.
Moreover, this step keeps the company close to its original strategy while opening new market opportunities. ESS Tech has built its reputation in long-duration storage. Now, it wants to serve more project types with alternative battery chemistries that support safety, cost control, and strong performance.
ESS Tech sodium-ion batteries will expand the product portfolio
ESS Tech signed a letter of intent for a strategic partnership with Massachusetts-based Alsym Energy. Under this plan, ESS Tech expects to add 8.5 GWh of sodium-ion cells and modules to its portfolio. This volume marks a major expansion for the company and signals a clear push into additional storage durations.
In particular, the new sodium-ion products will help ESS Tech serve short- and medium-duration storage applications. These segments have long attracted Lithium-ion systems. However, ESS Tech now aims to offer customers a non-lithium option made in the United States. Therefore, the company can address a wider set of energy storage needs across commercial, industrial, and grid-related use cases.
Furthermore, the partnership aligns with growing demand for battery systems built with diverse supply chains and alternative materials. By adding sodium-ion technology, ESS Tech can position itself as a provider of storage solutions across multiple duration ranges. That wider reach could strengthen its role in a fast-growing energy storage market.
Why ESS Tech sodium-ion batteries matter for U.S. energy storage
Alsym Energy officially introduced its Na-Series in October 2025. The company describes the products as non-flammable and non-toxic. In addition, Alsym says the batteries use materials that are not sourced from foreign entities of concern, often referred to as FEOC. This feature may appeal to buyers that want supply chain confidence and stronger domestic sourcing options.
Just as importantly, Alsym positions the Na-Series to support a lower levelized cost of storage, or LCOS. That metric matters because developers and utilities track total storage value over time. Lower LCOS can improve project economics and support broader deployment. Consequently, ESS Tech’s planned portfolio addition could attract customers looking for safe, cost-conscious, and U.S.-made storage products.
The U.S. energy storage sector continues to grow as power markets add more renewable energy. Solar and wind projects often need flexible storage to shift electricity and stabilize output. For that reason, battery systems that cover short, medium, and long durations can play an important role. ESS Tech appears to recognize this trend and is adjusting its product lineup to match it.
ESS Tech sodium-ion batteries support a broader non-lithium strategy
ESS Tech has focused primarily on long-duration storage. With this planned addition, the company can build a broader non-lithium storage platform. That strategy may help ESS Tech serve customers that need different discharge durations from a single supplier. It also creates room for more tailored system design.
For example, some projects need shorter bursts of storage for grid balancing or peak shaving. Others need medium-duration support for renewable integration or load shifting. Meanwhile, long-duration systems remain important for deeper energy shifting. By adding sodium-ion products, ESS Tech can better match its solutions to these varied requirements.
Additionally, the emphasis on non-lithium chemistries helps ESS Tech stand out in a crowded storage market. Rather than follow the same path as many competitors, the company is broadening its offer with alternative technologies. This move supports differentiation while keeping the focus on practical customer needs.
Key figures behind the ESS Tech sodium-ion batteries plan
8.5 GWh of sodium-ion cells and modules are expected to join ESS Tech’s portfolio.
Alsym Energy introduced its Na-Series in October 2025.
The products target short- and medium-duration storage segments.
ESS Tech will continue building a broader non-lithium storage offering.
Alsym says the batteries are non-flammable, non-toxic, and designed for lower LCOS.
What comes next for ESS Tech sodium-ion batteries
Although the current agreement is a letter of intent, it outlines a clear direction. ESS Tech wants to pair its long-duration expertise with sodium-ion products for shorter duration use cases. If the partnership moves forward as planned, the company could significantly expand its addressable market.
Overall, ESS Tech’s decision to add 8.5 GWh of U.S.-made sodium-ion batteries highlights a practical shift in strategy. The company is not moving away from long-duration storage. Instead, it is building on that base with more options for customers. As a result, ESS Tech can strengthen its position in U.S. energy storage with a larger, more flexible, and more diversified portfolio.
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