Unpacking the Toxicological Risks of Sodium-Ion Batteries: Material Safety and Manufacturing Concerns

(Part 1 of the "Toxicological Considerations in the Growth of Sodium-Ion Batteries" Series)

Sodium-ion batteries (Na-ion) have emerged as a promising alternative to lithium-ion technology, offering cost-effective, abundant, and potentially safer energy storage solutions. With projections indicating a $5 billion market by 2030, companies like CATL, Natron Energy, and Faradion are rapidly advancing the commercialization of sodium-ion battery technology. For example, the spin-off from the Chinese Academy of Sciences, HiNa Battery Technology focuses on developing sodium-ion batteries using Na-Fe-Mn-Cu-based oxide cathodes and anthracite-based carbon anodes. In 2023, HiNa partnered with JAC Group to introduce the first electric vehicle powered by a sodium-ion battery, the Sehol E10X. They have also developed various cell formats with energy densities up to 155 Wh/kg and aim to increase this to 180-200 Wh/kg in the future. The prevailing narrative suggests that sodium-ion batteries are inherently safer than lithium-ion, primarily due to sodium’s lower reactivity and the absence of lithium’s supply chain concerns. Yet, this assumption overlooks a crucial aspect of safety—the potential toxicity of battery materials, manufacturing processes, and occupational exposure risks.  As production scales up, so do concerns about the toxicological impact of these batteries on human health and workplace safety.

With this, let's unpack the hidden toxicological challenges of sodium-ion battery components, including cathodes, anodes, and electrolytes, and highlight why worker safety and material handling protocols must be a top priority for the industry’s long-term success.

Although sodium itself is widely considered safe, other critical components of sodium-ion batteries introduce potential toxicological concerns. To ensure that this technology fulfills its promise of being a safer alternative, there is a need to look closely at the key battery materials.

First, cathodes play a vital role in a battery’s energy storage and performance, but the materials used in sodium-ion batteries raise concerns about worker exposure, environmental persistence, and long-term health risks. Many sodium-ion batteries use sodium-manganese oxide (NaMnO₂) or sodium-iron-phosphate (NaFePO₄) cathodes. Manganese toxicity is well-documented, particularly in industrial settings, with chronic exposure being linked to neurological disorders, including a condition known as “manganism,” which has symptoms similar to Parkinson’s disease. Iron-phosphate cathodes are considered more stable, but their mining and processing introduce environmental concerns that require a much deeper assessment.

These issues highlight a significant research gap and bear the question - Have sodium-ion cathodes been thoroughly evaluated for long-term worker and environmental safety? If not, regulatory scrutiny could increase as production ramps up, leading to delays, lawsuits, or bans on certain materials.

Secondly, electrolytes are crucial for conducting ions between the cathode and anode, but their chemical composition raises serious safety questions. Sodium-ion batteries use organic solvents and sodium salts to facilitate ion transport. Some formulations rely on fluorinated compounds, which have been implicated in the formation of toxic per- and polyfluoroalkyl substances (PFAS), also known as "forever chemicals.” If these electrolytes break down under high temperatures or accidental combustion, do they release hazardous byproducts, similar to hydrofluoric acid (HF) in lithium-ion batteries? Without comprehensive degradation studies, sodium-ion batteries could introduce new chemical exposure risks for workers handling these materials in battery factories.

Thirdly, anodes. Unlike lithium-ion batteries, which use graphite anodes, sodium-ion batteries often rely on hard carbon, titanium-based compounds, or other novel materials. Hard carbon anodes have shown promise in improving battery performance, but little is known about their inhalation or dermal toxicity risks. Titanium-based anodes could introduce inhalable particulate risks for factory workers, similar to titanium dioxide (TiO₂) nanoparticles, which are currently classified as a possible human carcinogen when inhaled. If these materials prove to be more hazardous than initially thought, manufacturers could face stringent workplace safety regulations and unexpected financial burdens related to compliance and liability.

Beyond the materials themselves, the manufacturing of sodium-ion batteries introduces new occupational exposure risks.

• Inhalation and Dermal Exposure Risks: As battery production expands, thousands of workers will be handling raw sodium-ion materials daily. Without strict safety protocols, chronic exposure to battery dust, metal oxides, and solvent fumes could result in respiratory issues (especially if manganese-based cathodes are widely used), skin sensitization or dermatitis (depending on the electrolyte formulation), and long-term neurotoxicity risks, particularly in facilities with inadequate ventilation and safety training.

• Chemical Handling and Fire Safety: While sodium-ion batteries are less prone to thermal runaway than lithium-ion, they still pose fire and chemical spill risks in factory settings. If sodium-ion electrolytes contain fluorinated chemicals, could factory fires release persistent toxic pollutants? Do we fully understand how sodium-ion battery materials behave under high temperatures or accidental mixing? These questions are critical for battery manufacturers to address now before safety incidents or regulatory mandates slow down production.

Given these potential hazards, the sodium-ion battery industry must get ahead of regulatory oversight by establishing robust safety guidelines today. Unlike lithium-ion batteries, which faced regulatory tightening only after workplace injuries and environmental contamination incidents, sodium-ion manufacturers can proactively set industry safety standards. Companies that invest in toxicology research and worker safety now will have a competitive advantage when future regulations inevitably demand safer handling practices and stricter exposure limits.

The sodium-ion battery industry is at a critical inflection point. While it is poised for rapid expansion, its long-term success hinges on how well it addresses toxicological and occupational safety concerns today. Rather than assuming sodium-ion batteries are inherently safe, manufacturers, policymakers, and researchers must:

• Conduct rigorous toxicity studies on cathode, anode, and electrolyte materials.

• Implement stringent workplace safety protocols to protect workers from chronic exposure risks.

• Develop safer battery formulations that minimize reliance on hazardous compounds.

By tackling these issues now, the sodium-ion battery industry can avoid the pitfalls that lithium-ion technology faced, ensuring a stronger, safer, and more sustainable future for next-generation energy storage.

Part 2 will explore the broader environmental question: Are sodium-ion batteries truly a green alternative? I’ll dive into mining concerns, battery waste disposal, fire risks, and long-term ecological impact—issues that must be addressed to ensure sodium-ion technology is not just a market success but an environmental one as well.