When developing batteries, engineers often experience thermal runaway issues. A comprehensive thermal management plan is essential to optimize performance, extend battery life, and prevent thermal runaway. Thermal management begins with a meticulous analysis of battery components to build intrinsically safer batteries. This article discusses the main thermal analysis methods used for battery design, along with their limitations and advancements.
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Why is Thermal Analysis of Batteries Important?
A battery's temperature range should be constantly checked, safeguarded, and maintained at an ideal level. If the external temperature is too low, the cell will not supply its maximum power and will have a shorter lifespan. If the external temperature gets too high, parasitic reactions occur, lowering efficiency and longevity. The battery may swell, spontaneously ignite, explode, or emit poisonous vapors.
There are three basic kinds of consumer-use batteries. These are alkaline batteries, nickel metal hydride (NIMH) batteries, and lithium-ion batteries. Each kind has its advantages and disadvantages. However, lithium-ion batteries are currently the industry standard for applications involving energy storage.
Lithium-ion batteries are extremely lightweight and have a high power density. These operational advantages have made them indispensable to the transportable energy sector. These two advantages also make them more susceptible to thermal runaway. Thermal runaway happens when a cell's self-heating exceeds the quantity of heat that can be extracted from it. This accumulated heat inside the battery causes the temperature to rise, increasing self-heating. Thermal runaway, if left uncontrolled, may result in the generation of hazardous gases, ignition, and explosions due to the fast increase in battery temperatures.
The paths of thermal runaways can be characterized by applying specialized testing methods and equipment. Incorporating safety, interoperability, and other advanced testing approaches early in the design process may have a substantial payoff in terms of shortening time-to-market and producing batteries and systems that are intrinsically safer.
Current Thermal Analysis Methods: Overview and Significance
Differential scanning calorimetry (DSC), laser flash analysis, and thermomechanical analysis (TMA) are current key technologies for investigating battery thermal stabilities, exothermic processes, and enthalpies.
The most often used thermal analysis technique is differential scanning calorimetry (DSC). It enables accurate measurement of thermal properties such as melting/crystallization temperatures, reactivity temperatures, glass transition temperatures, and cross-linking processes (curing). Differential scanning calorimetry may be used to investigate both electrodes and electrolytes. It can, for instance, be used to study the energy generated during an electrolyte-electrode reaction.
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Thermal conductivity and diffusivity are the most significant thermophysical characteristics for describing a material's or component's heat transport capabilities. In this respect, the laser flash approach offers a quick, adaptable, and precise means of measuring thermal diffusivity.
The physical characteristics of materials vary as a result of temperature. Geometric and structural changes, as well as variations in strength, elasticity, and endurance, may all occur due to a sudden temperature change. These variations are not consistent in a battery cell and might increase mechanical stress and impact material performance. To forecast deformation and strain in battery cells, the expansion/shrinkage behavior must be measured. Thermomechanical analysis (TMA) analyzes the dimensional changes of solids, liquids, or pasty substances as a function of temperature and/or time when subjected to a specific mechanical force.
Limitations of Presently Used Thermal Analysis Methods
Differential scanning calorimetry (DSC) is a common thermal analysis method using low-cost devices. As a result, it may be found in a variety of characterization labs. However, DSC has various limitations, such as the small sample size that can be evaluated. The dynamic aspect of the approach is also a disadvantage for some applications since it suggests a lack of equilibrium settings, whereas the characteristics to be determined are fundamentally equilibrium.
Laser flash analysis is an effective technique for evaluating the thermal conductivity of homogeneous solid materials. However, when applied to non-ideal substances, the approach is prone to significant inaccuracies. Second, heat may be transferred to the environment through different routes, causing significant temperature variations throughout the measured temperatures, making analysis more challenging.
Thermomechanical analysis (TMA) is a technique used to describe the physical characteristics of materials when force is exerted at certain temperatures and time intervals. Although this approach is great for determining coefficients of thermal expansion, it does have certain drawbacks. The maximal sample thickness for thermomechanical analysis, for instance, cannot exceed 1mm, a substantial limitation restricting the broad use of this crucial thermal analysis approach.
Advancements in The Field of Thermal Analysis Methods
Due to the significance of personal protection and vehicle maintenance, the focus has shifted to battery thermal safety concerns in recent years. The most recent developments in battery thermal management (BTM) are done to meet the anticipated safety problems.
Electrolytes are distinguished by their strong conductivity, excellent electrochemical stability, and performance at low temperatures. However, the thermal stability of the number of electrolyte solutions is limited even at mild temperatures, where side reactions might begin to reduce the lifespan and performance of cells. Differential scanning calorimetry (DSC) and thermogravimetric analysis may be used to assess thermal stability (TGA). Combining both techniques constitutes the simultaneous thermal analyzer (STA).
NETZSCH is a major producer of thermal analysis solutions for the design and improvement of lithium-ion batteries. NETZSCH's most recent STA 449 Jupiter® series combines configuration versatility and exceptional performance in a single instrument. In addition, replaceable plug-in DSC and TGA sensors and many furnaces provide exact thermoanalytical analyses.
The performance of electric cars is fully dependent on the performance of a power battery, particularly the temperature-sensitive lithium-ion (Li-ion) battery. In this respect, Li-ion battery temperature must be managed and kept within a predetermined range. A recent study published in the journal Renewable and Sustainable Energy Reviews has created passive thermal control for prismatic Li-ion battery modules operating under abusive conditions. This is because PCM-based hybrid thermal regulation with air/liquid/heat pipes can deliver higher thermal performance compared to active or passive thermal management alone.
More from AZoM: What Materials are Used to Make Electric Vehicle Batteries?
References and Further Reading
Mohammed, A. G. et al. (2022). Recent advancement and enhanced battery performance using phase change materials based hybrid battery thermal management for electric vehicles. Renewable and Sustainable Energy Reviews. Available at: https://doi.org/10.1016/j.rser.2021.111759
NETZSCH. (2021). Thermal Analysis and Rheology of Batteries. From https://analyzing-testing.netzsch.com/en-US
Niu, J. et al. (2021). Numerical analysis of battery thermal management system coupling with low-thermal-conductive phase change material and liquid cooling. Journal of Energy Storage. Available at: https://doi.org/10.1016/j.est.2021.102605
Olabi, A. et al. (2022). Battery thermal management systems: Recent progress and challenges. International Journal of Thermofluids. Available at: https://doi.org/10.1016/j.ijft.2022.100171
Ulrich, M., & Stumpf, C. (2022, March 21). Cutting-Edge Lithium-Ion Battery Development is Supported by Thermal Analysis Research. From TA Instruments: https://www.tainstruments.com/cutting-edge-lithium-ion-battery-development-is-supported-by-thermal-analysis-research/
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