X-Ray Diagnostics of Battery Materials

NREL researchers use state-of-the-art X-ray diagnostic capabilities as a nondestructive method to examine the composition and architecture of battery materials.

The lithium-ion (Li-ion) batteries favored for energy storage in electric vehicles (EVs), stationary applications, and personal devices are dynamic and systems of perpetually evolving composition and architectures. As Li-ion batteries degrade over time, numerous contributing factors cause unfavorable reactions and morphological transformation. To improve the energy density of batteries, extend their operating life, or make them safer, it is critical to understand how and why such dynamic processes occur and contribute to the performance and safety of batteries.

X-ray diagnostic techniques offer a way to examine properties of Li-ion battery materials, such as their crystal structure, chemical composition, and 3D architectures. Being nondestructive, X-rays can probe changes as they occur in real time without significantly interfering with the system. This provides a powerful tool for understanding the materials that we work with and guiding the design of next-generation Li-ion batteries.

Capabilities

NREL has a suite of advanced X-ray diagnostic capabilities, including X-ray computed tomography (CT), X-ray diffraction (XRD), X-ray fluorescence (XRF), and X-ray spectroscopy  systems. Researchers at NREL have developed novel in-situ environments for this equipment to facilitate imaging during mechanical, electrochemical, or thermal changes within the material of interest. In addition, researchers established software tools to process, visualize, and quantify material properties for X-ray data including machine-learning segmentation methods and bespoke software packages for quantifying transport properties of porous materials.

Advancements in Battery Research

Identifying the Optimal Architecture of Battery Electrodes

Using X-ray nano-CT, NREL built a comprehensive electrode microstructure library where researchers can compare calendared and uncalendered battery electrode samples that have or have not artificially generated conductive carbon and binder within the pore phase. Researchers around the world can use this databank to access realistic architectures for modeling or analysis.

Quantifying Limitations of Battery Electrodes During Fast Charging and Discharging

Researchers at NREL have used synchrotron XRD and XRD-CT to quantify gradients in lithiation and degradation throughout the depth of electrodes during fast charging and within individual electrode particles while they degrade. Applying world-leading synchrotron X-ray capabilities, this work shed new insight in the magnitude of chemical heterogeneities within battery electrodes during their lifetime and how such heterogeneities unfavorably affect the performance of batteries.

Understanding the Failure Mechanisms of Li-ion Batteries During Thermal Runaway

Thermal runaway of Li-ion batteries, during which batteries transform from intact to destroyed, occurs within seconds. Researchers at NREL used high-speed synchrotron X-ray radiography to understand the failure mechanisms of Li-ion batteries in a range of mechanical to thermal abuse scenarios. NREL has compiled an open-source Battery Failure Databank with hundreds of high-speed radiography videos of battery failure alongside their thermal responses during catastrophic failure. This data bank provides researchers and engineers around the world with insight to help guide the design of safer and battery systems.

Publications

For more publications related to battery development and energy storage systems, view the electrochemical energy storage publications.

Resolving the Discrepancy in Tortuosity Factor Estimation for Li-ion Battery Electrodes Through Micro-Macro Modeling and Experiment, Journal of The Electrochemical Society (2018)

Quantitative Microstructure Characterization of a NMC Electrode, ECS Transactions (2017)

Spatial Quantification of Dynamic Inter and Intra Particle Crystallographic Heterogeneities Within Lithium Ion Electrodes, Nature Communications (2020)

Spatial Dynamics of Lithiation and Lithium Plating During High-Rate Operation of Graphite Electrodes, Energy Environmental Science (2020)

Modelling and Experiments To Identify High-Risk Failure Scenarios for Testing the Safety of Lithium-Ion Cells, Journal of Power Sources (2019)

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