By Muhammad OsamaReviewed by Lexie CornerApr 10 2025A recent study in Nature Energy introduced a new method for improving safety screening in rechargeable lithium-ion batteries. Researchers developed lab-scale cylindrical pouch-type cells designed for Accelerating Rate Calorimetry (ARC) testing.
They focused on addressing the challenges of thermal runaway, improving the understanding of battery behavior under stress, and supporting the development of safer, high-energy-density energy storage systems.
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Background: Addressing Thermal Runaway Risks
Lithium-ion batteries are essential to a wide range of modern technologies, from smartphones to electric vehicles. As demand for higher energy capacity increases, ensuring battery safety becomes increasingly important. One of the most serious risks is thermal runaway, where heat generated by internal exothermic reactions exceeds the battery’s ability to dissipate it, potentially leading to fires or explosions.
Traditional safety testing tools like ARC typically require full-size battery cells with large ampere-hour capacities. These tests are expensive and resource-intensive, which makes them impractical for early-stage safety screening during battery development. As a result, there's a growing need for more efficient, lab-friendly testing methods that still deliver accurate safety assessments.
Developing Lab-Scale Cylindrical Pouch-Type Cells
The authors designed and developed small cylindrical pouch-type lithium-ion cells, each with a capacity of approximately 21 mAh and around 0.1 g of cathode active material, to enable full-cell-level ARC tests on a laboratory scale. Their compact size allows full-cell-level thermal safety analysis while minimizing material usage.
The ARC tests measured self-heating behavior and provided quantitative data on the onset of thermal runaway. The battery configuration included LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes, graphite anodes, and a 1 mol/L LiPF6 electrolyte in a mixture of ethylene carbonate and dimethyl carbonate. The cells were engineered to favor heat accumulation and restrict dissipation, enhancing the sensitivity of thermal runaway detection.
To quantify safety performance, the researchers introduced the Thermal Runaway Factor (TRF)—a new metric defined as the ratio of heat accumulation to heat dissipation. TRF is based on parameters such as battery energy, component mass, and specific heat capacity. It offers a framework to evaluate how different battery designs affect thermal behavior.
The team also used complementary techniques, such as Differential Scanning Calorimetry (DSC), Gas Chromatography-Mass Spectrometry (GC-MS), and X-ray Diffraction (XRD), to analyze material stability at high temperatures.
Key Findings: Understanding Battery Behavior Through TRF
The outcomes indicated that TRF is a key indicator for predicting the safety of lithium-ion batteries. The authors observed a strong correlation between TRF and other safety factors, including self-heating rates, identifying a self-heating rate exceeding 60 °C/min as the threshold for thermal runaway.
Compared to coin and monolayer-pouch-type batteries, the cylindrical pouch-type cells exhibited TRF values more than ten times higher, enabling the detection of thermal runaway events at lower external temperatures. Oxygen release from charged cathode materials triggers runaway around 220 °C.
The study also demonstrated that battery design significantly affects TRF. Increasing the aspect ratio (height/diameter) reduced TRF and delayed the onset of thermal runaway, highlighting the potential for safety improvements through structural optimization.
Furthermore, TRF was more effective in predicting thermal risks than traditional safety metrics, such as volumetric and gravimetric energy densities. These results support using TRF as a practical tool for screening battery designs and materials.
Practical Implications: A New Way to Evaluate Battery Safety
This research has significant implications for the battery industry. Using TRF as a key safety metric, manufacturers can evaluate new materials and designs early in development, minimizing dependence on full-scale prototypes.
This approach streamlines the design and testing process, saving time and resources while providing deeper insights into thermal runaway behavior. As regulatory demands tighten and the need for high-performance batteries grows, accurately predicting safety risks becomes increasingly critical, especially for electric vehicles.
Integrating TRF into safety evaluations helps establish more reliable protocols, ensuring the safety and performance of lithium-ion batteries across various applications.
The study lays the groundwork for developing high-energy-density batteries without compromising safety. It redefines screening methods and adopts TRF as a design parameter to support faster innovation in battery technology. It also contributes to a global shift toward safer, more sustainable energy storage solutions.
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Conclusion: Future Directions in Battery Research
This study demonstrated that TRF is an effective safety metric for identifying thermal runaway risks in lithium-ion batteries, even at the lab scale. It enables early screening and supports the development of safer battery materials without relying on full-scale prototypes.
As demand increases for high-energy-density batteries in electric vehicles, consumer electronics, and renewable energy systems, balancing performance with safety is becoming more important. The TRF methodology offers a valuable tool for improving safety standards and guiding material optimization.
Future work should explore its applicability across different battery chemistries and integrate it with other testing approaches. These efforts will help shape safer, more sustainable energy storage technologies.
Journal Reference
Ko, S., Otsuka, H., Kimura, S. et al. Rapid safety screening realized by accelerating rate calorimetry with lab-scale small batteries. Nat Energy (2025). DOI: 10.1038/s41560-025-01751-7, https://www.nature.com/articles/s41560-025-01751-7
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