The Dawn of Safer Sodium-Ion Batteries: A CAS Milestone
In a landmark achievement for energy storage technology, researchers from the Chinese Academy of Sciences (CAS) have published a pioneering paper in Nature Energy detailing the world's first successful blockage of thermal runaway in ampere-hour (Ah)-level sodium-ion (Na-ion) batteries. This breakthrough addresses one of the most critical barriers to commercializing Na-ion batteries for large-scale applications like grid storage and electric vehicles (EVs). Thermal runaway—a chain reaction of heat buildup, gas generation, and potential fires or explosions—has long plagued battery safety, but the CAS team's polymerizable non-flammable electrolyte (PNE) eliminates it entirely, even under extreme abuse conditions.
The study, led by Yong-Sheng Hu and colleagues at the Institute of Physics, CAS, demonstrates that their innovative electrolyte not only prevents flammability but also forms a protective cross-linked barrier when heated, halting destructive interactions between electrodes. This positions China at the forefront of next-generation battery research, leveraging the abundance and low cost of sodium to challenge lithium-ion (Li-ion) dominance.
Why Sodium-Ion Batteries Matter: Abundance Meets Performance
Sodium-ion batteries represent a promising alternative to Li-ion technology. Sodium is the sixth most abundant element in Earth's crust, vastly more plentiful than lithium, which faces supply chain vulnerabilities and price volatility. Na-ion batteries offer comparable energy density—around 160-180 Wh/kg in recent prototypes—while operating effectively at low temperatures and with faster charging capabilities.
However, safety has been a sticking point. While inherently less prone to thermal runaway than high-nickel Li-ion cells due to stable cathode materials like layered oxides (e.g., NaxNi1/3Fe1/3Mn1/3O2), scaling to Ah-level packs revealed risks from gas evolution and short circuits. The CAS innovation resolves this, achieving zero thermal runaway up to 300°C in full cells.
Unpacking the Polymerizable Non-Flammable Electrolyte
The core of the breakthrough is the PNE, designed with a synergistic anion-cation solvation effect using solvents like triethyl phosphate. Under normal conditions, it ensures high ionic conductivity and stable solid electrolyte interphase (SEI) layers on anodes (hard carbon) and cathodes. When temperatures rise—say, from overcharge or penetration—the electrolyte polymerizes rapidly, creating a solid cross-linked network.
This barrier impedes ion transport between electrodes, suppresses side reactions, and blocks reductive gas generation, which fuels propagation in traditional electrolytes. Cryo-transmission electron microscopy (cryo-TEM) and in-situ infrared spectroscopy confirmed the uniform polymerization, while X-ray photoelectron spectroscopy (XPS) showed enhanced interfacial stability.
Step-by-step, the process works as follows:
- Heat triggers monomer activation (above 150°C).
- Radical polymerization forms a gel-like matrix.
- Cross-linking densifies into an insulating shield, isolating failure sites.
Rigorous Testing Validates Unprecedented Safety
The team assembled Ah-level cylindrical and pouch cells, subjecting them to accelerated rate calorimetry (ARC) up to 300°C—no thermal runaway occurred, unlike conventional Na-ion cells that vent gases and ignite around 200°C. Nail penetration tests, a gold standard for abuse tolerance, produced no smoke, fire, or explosion, with surface temperatures peaking below 100°C.
Thermogravimetric-differential scanning calorimetry-mass spectrometry (TG-DSC-MS) revealed minimal gas evolution (e.g., <1% H2), contrasting with carbonates that release flammable hydrocarbons. This data underscores the PNE's dual role: non-flammable base plus active self-protection.
The Research Team: CAS's Elite at the Helm
Corresponding authors Yong-Sheng Hu and Liquan Chen, both professors at CAS Institute of Physics, spearheaded the effort. Huairou Division, CAS, provided advanced facilities, while University of Chinese Academy of Sciences (UCAS) students like Haibo Wang and Xubin Wang contributed key experiments. Collaborators from Jilin University and HiNa Battery Technology Co. Ltd. bridged academia-industry gaps.
CAS's Key Laboratory for Renewable Energy has long championed Na-ion R&D, with prior works on cathodes and anodes. This paper builds on their ecosystem, training PhD candidates in condensed matter physics and electrochemistry—a boon for China's higher education in materials science.
China's Sodium-Ion Ecosystem: From Lab to Factory
China dominates Na-ion innovation, with over 90% of global patents. HiNa Battery, a CAS spin-off, shipped 9 GWh in 2025 and targets hundreds of GWh by 2028, powering JAC trucks with 20% range gains in cold weather. CATL plans 50 GWh capacity soon.
Policies like the 14th Five-Year Plan prioritize Na-ion for grid storage, where safety trumps density. Projections: China's Na-ion market hits $9.25B by 2033 (CAGR 22%), driven by EV and renewables integration.China Sodium-Ion Battery Market Report
Universities like Tsinghua and Fudan complement CAS, fostering talent amid 12.7M STEM grads yearly.
Safety Edge Over Lithium-Ion: Data-Driven Comparison
Na-ion's onset temperature for TR is ~100°C higher than NMC Li-ion, with less oxygen release from cathodes. CAS PNE pushes this further: zero propagation vs. Li-ion's chain reactions. Studies show Na-ion gas production 50% lower, reducing pack-level risks.
| Metric | Na-ion (CAS PNE) | Li-ion (NMC) |
|---|---|---|
| TR Onset (°C) | >300 | ~200 |
| Nail Test Outcome | No fire | Fire/explosion |
| Gas Evolution (%) | <1 | 10-20 |
| Cost ($/kWh) | ~50 | ~100 |
Path to Commercialization: HiNa and Beyond
HiNa's 2026 conference unveiled cells at 175 Wh/kg, matching LFP Li-ion costs by 2027. Integration in commercial trucks validates lab-to-market. Challenges remain: anode optimization for 200+ Wh/kg. CAS-UCAS pipeline ensures R&D continuity.
Broader Impacts: Grid Stability and Green Transition
Safe Na-ion packs enable massive grid storage, stabilizing renewables amid China's 1.2 TW solar/wind capacity. Reduced fire risks cut insurance costs 30%, accelerating adoption. For EVs, cold-weather performance suits northern provinces.
Stakeholders praise: Industry eyes 10% market share by 2030; academics highlight UCAS training boost.
Photo by Clark's Designs on Unsplash
Future Horizons: Scaling and Global Collaboration
Next: PWh-level packs, hybrid Na-Li systems. CAS plans international ties, sharing via Belt and Road. This paper cements China's higher ed role in sustainable tech, inspiring students in electrochemistry programs.
Actionable insights: Researchers—focus interfacial engineering; policymakers—fund Na-ion hubs; educators—integrate into curricula.