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Insights from the BattCave

Detecting and Addressing Lithium Plating in Lithium-Ion Battery Cells

High resolution ultrasound images of large-format battery cells, with and without Li plating.
High resolution ultrasound images of large-format battery cells, with and without Li plating.

Lithium-ion batteries (LIBs) have revolutionized the electrical transportation industry, powering electric vehicles (EVs), trains, ships and aircraft. As the demand for higher energy density batteries increases, the detection of lithium plating has become a universal challenge. In this blog post, Titan will explore:

  • the impact of deploying cells with lithium plating in EV (Electric Vehicle) batteries

  • the traditional methods used for diagnosis and the difficulties associated with detection

  • the causes of lithium plating in gigafactories

  • Corrective actions that can be taken

We will also highlight why ultrasound inspection is a valuable diagnostic tool for detecting lithium plating. Impact of Cells with Lithium Plating in EV Batteries If cells with irreversible lithium plating are deployed in EV batteries (and plenty of examples of this exist), several adverse effects can be observed. First, capacity loss occurs due to the reduced availability of active lithium ions for reversible reactions, resulting in decreased energy storage capability. The presence of lithium plating also increases the internal resistance of the battery, leading to diminished power delivery and reduced overall performance. Moreover, lithium plating can cause safety hazards. Lithium plating may deposit in the form of dendrites which may penetrate the separator and create moderate, or severe, internal short circuits. These short circuits can result in thermal runaway, leading to battery fires or explosions. Increasingly, inbound inspection teams are looking for reassurance that Li plating is not present. Traditional Methods for Diagnosing Lithium Plating Detecting lithium plating can be challenging. It occurs internally and is not visually apparent, making it difficult to identify during routine quality control processes. The methods employed for diagnosing lithium plating range from destructive to non-destructive techniques. Destructive methods include:

  • scanning electron microscopy (SEM)

  • nuclear magnetic resonance (NMR)

  • X-ray photoelectron spectroscopy (XPS)

These are often only made possible through teardowns. While these methods provide direct evidence of lithium plating, they may cause permanent damage to the cells. They are expensive, time consuming or are not suitable for in-line application. Non-destructive methods such as neutron diffraction, local deformation analysis, and ultrasonic diagnostics, such as Titan’s IonSight technology, have been developed as low-cost and in-situ detection methods. Ultrasonic inspection has gained prominence due to its ability to reveal the inhomogeneities inside battery cells without causing damage. By analyzing the acoustic signals and inspecting the inner structure of the cells, ultrasonic inspection can effectively detect the presence of lithium plating and provide critical information for quality control. Causes of Lithium Plating In Lithium Cell Factories Unoptimized process steps, or defective cell components, may cause the occurrence of lithium plating. Examples include:

  • Electrolyte soaking time

  • Inhomogeneous wettability

  • separator wrinkles

  • collapsed pores

However, it is during the cell formation process step where lithium plating will likely begin to form. The protocol plays a crucial role in creating a stable solid electrolyte interface (SEI) layer and minimizing active lithium loss, electrolyte depletion, and capacity fade throughout the battery's lifespan. Cell formation is not only the most expensive step, but also a repetitive process that often becomes a bottleneck. Process engineers strive to reduce the formation time to increase production rate and make efficient use of cyclers. However, faster formation can lead to issues such as lithium plating on cells with manufacturing defects. Using High Resolution Ultrasonic Inspection To Diagnose Lithium Plating High resolution ultrasound inspection offers several advantages as a diagnostic tool for lithium plating. It is a non-destructive technique that allows for in-situ, in-line and real-time detection of inhomogeneities inside battery cells. With coverage across the whole cell, and the power to see wetting inhomogeneity, separator issues, wrinkles, residual gas, debris and inactive zones, it points out many of the defects that may aggravate occurrences of lithium plating (see above). Ultrasound inspection provides valuable information about density variations within layers of a lithium cell. These density variations are an important hint about the formation of lithium plating. By incorporating high resolution ultrasonic inspection equipment into quality control processes, manufacturers can proactively identify lithium plating, take corrective actions to prevent its negative impact on battery performance and avoid flawed cells leaving the factory. Conclusion: Detecting and addressing lithium plating in large and small format battery cells is crucial for ensuring the performance, cycle life, and safety of battery packs. Traditional diagnostic methods, while providing direct evidence, often cause damage to the cells. In contrast, non-destructive techniques, such as Titan’s IonSight high resolution ultrasound inspection, offer a practical solution by enabling in-line detection without compromising the integrity of the cells. Ultrasound scanning systems are scalable and versatile. By understanding the causes of lithium plating and implementing corrective actions, manufacturers can enhance the quality and reliability of battery cells, and optimize formation throughput, contributing to the advancement of sustainable electric vehicle technology, at an affordable cost. About Titan Advanced Energy Solutions: Titan Advanced Energy Solutions, a trail blazer in non-destructive lithium-ion battery cell inspection technology, applies high resolution / high sensitivity ultrasound technology to detect a range of imperfections including lithium plating, separator issues, wetting, wrinkles, debris, residual gas, delamination, dry zones, and not fully activated zones. This groundbreaking innovation uncovers hidden defects that elude conventional electrical inspection methods, providing real-time, in-line detection of critical issues pre-formation, post-formation, end of line or during inbound inspection. Our headquarters in Salem, MA serves as the epicenter of innovation, driving advancements that shape the future of lithium-ion battery manufacturing and deployment.

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