Observing Lithium Dendrites in Real-time With Battery Imaging
Researchers investigate dendrite formation in lithium metal batteries during cycling and uncover their behavior.
Lithium metal has gained popularity recently as an anode material in batteries due to its high theoretical specific capacity, which means it can store more energy per unit of weight than other anode materials. This high specific capacity enables lithium metal to improve battery density and performance.
Lithium-ion batteries. Image used courtesy of Adobe Stock
When used as an anode, lithium metal forms a stable solid-electrolyte interphase (SEI) layer on its surface that protects it from reacting with the electrolyte and provides a stable interface for the movement of lithium ions. This enhances the battery's cycling stability, which means it can be charged and discharged repeatedly without losing capacity or degrading quickly.
Moreover, using lithium metal as an anode can also lead to a higher voltage and energy density in batteries. Due to higher voltage, more energy can be extracted from the battery before needing a recharge, while higher energy density means more energy storage in a smaller space. This property is particularly important for electric vehicles and portable electronics, where weight and volume are critical factors.
Lithium Anode Dendrite Formation
However, lithium metal has some drawbacks as an anode material. One of the main issues is dendrite formation, which are lithium metal whiskers that can grow and penetrate through the SEI layer, causing short circuits and safety hazards. The dendrites can lead to thermal runaways and even explosions, especially when the battery is overcharged or overheated. Therefore, developing effective dendrite suppression strategies is critical for commercial lithium metal anodes in batteries.
To come up with such strategies, studying dendrite formation is crucial. High-resolution battery imaging techniques, such as X-ray computed tomography (CT) and scanning electron microscopy (SEM), allow researchers to track the growth and movement of dendrites in real-time.
In addition to providing insights into dendrite formation, battery imaging can help researchers optimize battery design and performance. By analyzing the battery's internal structure, researchers can identify areas where dendrite growth is most likely to occur and design mitigation strategies to prevent it. Moreover, battery imaging can reveal how other factors, such as electrolyte composition and temperature, affect dendrite formation and battery performance.
Observing Lithium Dendrites in Real-time
A team of researchers from Chalmers University of Technology, Sweden, focuses on studying what exactly happens to the lithium metal in a cell during cycling. In an experiment conducted at the Swiss Light Source outside Zurich in Switzerland, they analyzed the lithium deposits in real time. The researchers prepared a specially designed battery cell for this experiment and visualized it using X-ray tomographic microscopy. They observed the formation of needle-like structures in their first attempt.
Illustration of the experimental setup. Image used courtesy of Chalmers University of Technology
The minimized diameter of the cell and high flux synchrotron X-ray beam allowed researchers to quantitatively track the spatial distribution of deposited lithium and its behavior and capture the formation of dead lithium during plating and stripping. They aim to test this technique on other battery concepts at the Swedish MAX IV lab, a national research facility for advanced X-ray experiments.
The team also plans to develop this method to take faster measurements at a higher resolution to observe dendrites early in the deposition process. Their study will provide insights into using lithium metal batteries on a large scale.