Submitted by Pooja Pandey on Thu, 17/08/2023 - 16:00
Scientists at the University of Cambridge, in collaboration with colleagues at the CNRS in Paris and Boston College (USA), reveal the hidden dynamics of Li-ion batteries by pushing optical imaging techniques to visualise the intricate processes inside lithium-ion batteries during operation. Li-ion batteries, commonly used in consumer electronics, electric vehicles, and other applications, store and release energy through the movement of lithium ions between two reservoirs. Understanding these processes is crucial for improving battery efficiency and discovering new materials.
It was a big surprise to observe that the battery electrolytes, the liquids shuttling Li-ions around the battery, can emit light under multi-photon excitation. The intensity of this light was proportional to the lithium-ion concentration in the electrolyte, providing a useful tool to visualise electrolyte polarisation gradients. Raj Pandya
Over the last two decades optical microscopy has become an increasingly popular technique for imaging inside batteries, but it has limitations. It only allows 2D visualisation and imaging of the solid phase of batteries, leaving the complex liquid environment unexplored.
To overcome these challenges, the researchers adapted laser-scanning confocal microscopy, a technique often used in life sciences, and combined it with near-infrared light excitation, multiphoton spectroscopy, and computational imaging methods.
“This innovative approach enabled us to observe particles up to 10 microns deep inside the battery electrodes in 3D,” shared Raj Pandya, first author and Research Associate at the Cavendish Laboratory. “By ‘watching’ the particles inside the battery as it cycled, we discovered valuable insights. This allowed us to observe how particles changed volume, the speed at which ions moved through them, and what occurred at different depth surfaces within the particles.”
The researchers could also monitor the build-up of polarisation concentration gradients in the liquid surrounding battery particles and how these gradients changed with the cycling rate.
The study, published in Nature Nanotechnology, showcases the method's effectiveness in simultaneously imaging both solid and liquid phases inside operating batteries, a challenging task until now.
“It was a big surprise to observe that the battery electrolytes, the liquids shuttling Li-ions around the battery, can emit light under multi-photon excitation. The intensity of this light was proportional to the lithium-ion concentration in the electrolyte, providing a useful tool to visualise electrolyte polarisation gradients,” added Pandya.
The research not only establishes a robust framework for optical imaging of batteries and other electrochemical systems but also opens possibilities for academic and industrial labs developing new battery materials to better characterise their electrodes in real-time.
Despite this progress, the researchers acknowledge that there is still room for improvement. They aim to push the technique further by visualising deeper into batteries with higher chemical selectivity and spatial resolution. Their ultimate goal is to develop imaging methods capable of capturing processes occurring on extremely fast timescales with nanometric resolution.
This breakthrough brings us closer to being able to characterise in detail, at the lab-scale, the inner workings of batteries, an important stepping-stone in the discovery of new materials for high-capacity, fast-charging energy storage technologies that the modern world will rely on. As the researchers continue to push the boundaries of this imaging approach, the future of battery research looks promising.
Reference:
Pandya, R., Valzania, L., Dorchies, F. et al., 'Three-dimensional operando optical imaging of particle and electrolyte heterogeneities inside Li-ion batteries.' Nat. Nanotechnol. (2023). DOI: 10.1038/s41565-023-01466-4
Image:
Confocal optical microscope. Credit: Dr. Raj Pandya