Over the last decade, in situ and in operando isothermal microcalorimetry (IMC) has emerged as the preferred approach for assessing heat transport during lithium-ion battery cycling.
Legacy approaches for cycling a cell to failure previously took many months; new diagnostic techniques can predict long-term behavior in a couple of weeks. One developing diagnostic method is to measure a battery's parasitic heat during cycling.
Krause et al. (2012) described a method for separating parasitic heat events from total heat generation, and thereby quantifying parasitic processes.1 Parasitic response information can then be used to:
- Evaluate cell quality
- Help formulate active materials
- Assess the impact of additives
- Investigate the creation and growth of the solid electrolyte interphase (SEI)
- Contribute to cycle and calendar life prediction models
The following research examples use the TA Instruments TAM (Thermally Activity Monitor) microcalorimeter to assess battery parasitic reactions to new materials, formulations, and processing processes.
Enhancing New Battery Formulations by Understanding Parasitic Reactions
L. J. Krause et al. (2012) from 3M and the Jeff Dahn group at Dalhousie University investigated the effects of various graphite types and electrode formulations on cell performance.1
They were early innovators who used the TAM III to measure parasitic energy and connect it with the loss of active lithium, or coulombic efficiency, "confirming the source of the parasitic energy as the heat of reaction occurring between the lithiated electrodes and the electrolyte."1
Their strategy worked well for researching new material sets and forecasting cell longevity. Previous studies found that eliminating ethylene carbonate (EC) from electrolytes in graphite lithium-ion pouch cells boosted cycle life and longevity at high voltages.
S. L. Glazier et al. (2017) at Dalhousie University examined the performance of EC-free electrolytes by monitoring parasitic heat flow during high-voltage operation using a TAM III microcalorimeter and a battery cycler.2
The scientists evaluated the parasitic reaction's duration and voltage dependence to better understand the battery's complicated internal reactions. From this, they discovered that EC-free electrolytes "yielded higher parasitic heat flow at lower voltages but performed better than EC-containing electrolytes above 4.3 V."2
The EC-free electrolytes recovered faster from high-voltage exposure, resulting in decreased parasitic heat flow.
Their findings demonstrate that EC-free electrolytes deliver outstanding high-performance operation, and further study can help improve their performance at low potentials, leading to a more successful battery electrolyte formulation.
Image Credit: Nana_studio/Shutterstock.com
Evaluating New Battery Materials with Heat Flow Measurements in High Voltage
Another study from Glazier et al. (2017) examined natural and manufactured graphite cells by evaluating parasitic heat flows and capacity retention. Their TAM III worked well for "understanding the voltage and time dependence of parasitic reactions in high voltage lithium ion pouch cells."3
They used IMC to explore parasitic reactions in a low voltage range to probe the electrolyte's reaction in the negative electrode, and then tested in a high voltage range to probe the oxidized positive/negative interaction.
The results show that natural and artificial graphite electrodes with proper electrolyte additive loading generate equivalent levels of parasitic heat, with artificial graphite producing the least. Insufficient electrolyte additive loading led to increased parasitic heat flow and significantly poorer electrochemical performance in the high-voltage band.
Long-term cycling behavior indicated that natural graphite cells experienced a faster rate of capacity loss than artificial graphite cells.
The group proposes that with insufficient electrolyte loading, the SEI layer is thin and ineffective at withstanding the mechanical expansion of natural graphite particles during lithiation, resulting in irreversible expansion and faster capacity fade as new SEI forms on the exposed surfaces.
Developing Baselines for Optimizing High-Ni NMC Cathodes
C. D. Quilty et al. (2022) investigated new lithium-ion battery materials in cells with nickel-rich lithium nickel manganese cobalt oxide (NMC) cathodes.4
NMC has a high energy density but suffers from rapid potential capacity fade; hence, its capacity should be carefully managed. To maximize the lifetime and capacity of NMC batteries, capacity-fading mechanisms must be measured using a variety of methods, including operando IMC experiments.
Quilty et al. used their TAM IV to get a thorough understanding of battery deterioration by taking real-time heat readings during (de)lithiation. They stated that IMC aided their investigation as a "powerful, non-destructive tool to capture the instantaneous heat flow released from a cycling battery with ultrahigh precision."4
They discovered that higher rates of capacity fading at higher voltages could be caused by increased thermal energy loss or decreased electrochemical efficiency. Their findings establish a benchmark for optimizing future NMC cathodes.
Evaluating Prelithiation Impact for New Lithium-Ion Battery Processing Techniques
Prelithiation is a new way of forming lithium-ion batteries that involves adding active lithium content prior to battery cell operation.
This compensates for lithium loss during the formation cycle, resulting in high energy density and improved cycle performance if done appropriately. However, the potentially detrimental effects of prelithiation are still being investigated.
Linghong Zhang et al. (2022) used a TAM III to evaluate both the prelithiation process and the resulting parasitic responses.5
Prelithiated cells experienced more parasitic reactions in the first cycles, but after three cycles, "similar heat signals from parasitic events were observed for the prelithiation cells and the control cells, indicating stabilization and the possibility of no long-term side effects from prelithiation."5
This was the first demonstration to use isothermal microcalorimetry to evaluate prelithiation, and the results are promising. The authors conclude that "in operando isothermal microcalorimetry is a powerful tool to characterize the prelithiation application for lithium-ion batteries."5
Future research can continue to optimize prelithiation, with a focus on monitoring the effects of prelithiation additives for safe cell formation on a larger scale.
The Technology Behind the Research
All five of the research papers mentioned above used the TAM Microcalorimeter, a cutting-edge analysis tool that evaluates the thermal behavior of samples under controlled temperature circumstances.
Many of the studies combined the TAM with a potentiostat or battery cycler, allowing them to detect heat flow during battery operation and obtain solid results.
The new Battery Cycler Microcalorimeter solution is designed with this application in mind, combining the TAM IV Microcalorimeter with the BioLogic VSP-300 Potentiostat to form a single integrated system. Researchers and scientists at all levels can now measure in operando battery heat flow using seamless system control and data analytics.
Acknowledgments
Produced using materials originally authored by Hang Lau, Morgan Ulrich, Jeremy May, and Julienne Regele.
References and Further Reading
- Krause, L.J., Jensen, L.D. and Dahn, J.R. (2012). Measurement of Parasitic Reactions in Li Ion Cells by Electrochemical Calorimetry. Journal of The Electrochemical Society, 159(7), pp.A937-A943. DOI:10.1149/2.021207jes. https://iopscience.iop.org/article/10.1149/2.021207jes
- Glazier, S.L., et al. (2017). Measuring the Parasitic Heat Flow of Lithium Ion Pouch Cells Containing EC-Free Electrolytes. Journal of The Electrochemical Society, 164(4), pp.A567-A573. DOI:10.1149/2.0331704jes. https://iopscience.iop.org/article/10.1149/2.0331704jes.
- Glazier, S.L., et al. (2017). An Analysis of Artificial and Natural Graphite in Lithium Ion Pouch Cells Using Ultra-High Precision Coulometry, Isothermal Microcalorimetry, Gas Evolution, Long Term Cycling and Pressure Measurements. Journal of The Electrochemical Society, 164(14), pp.A3545-A3555. DOI:10.1149/2.0421714jes. https://iopscience.iop.org/article/10.1149/2.0421714jes
- Quilty, C.D., et al. (2022). Multimodal electrochemistry coupled microcalorimetric and X-ray probing of the capacity fade mechanisms of Nickel rich NMC – progress and outlook. Phys. Chem. Chem. Phys., 24(19), pp.11471–11485. DOI:10.1039/d1cp05254c. https://pubs.rsc.org/cp/article-abstract/24/19/11471/722836/Multimodal-electrochemistry-coupled?redirectedFrom=fulltext.
- Zhang, L., et al. (2022). Isothermal Microcalorimetry Evaluation of In Situ Prelithiation in Lithium-ion Batteries. Journal of The Electrochemical Society, 169(11), p.110546. DOI:10.1149/1945-7111/aca366. https://iopscience.iop.org/article/10.1149/1945-7111/aca366.
This information has been sourced, reviewed, and adapted from materials provided by TA Instruments.
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