Energy Storage
We are using X-ray characterization under realistic operating conditions to understand more completely how rechargeable batteries, such as Li-ion, function and fail. Using different imaging, spectroscopy, and scattering techniques we can probe batteries from the mm down to Å length scales. Depending on the technique and the questions we want to explore, we can probe full cells in either pouch or cylindrical geometries, half cells, and model cell geometries.
Visualize damage from fast charging at multiple length scales
Fast charging batteries are critical to the widespread adoption of electric vehicles to compete with refueling times of combustion-based vehicles. In the near term, adapting current commercial battery technologies to perform better under fast charging conditions through engineering optimizations will greatly expedite the process while exploratory fast-charging electrode materials are being pursued. To do so, the degradation modes in Li-ion batteries need to be completely explored to understand fast charging limits while maintaining a high energy density and a long cycle life. While lithium plating on graphite still remains a challenge, cathode degradation also plays a key role in battery performance. We used nano- and micro-X-ray computed tomography to characterize the mechanical degradation of cathodes cycled at different rates. Higher charging rates and increased cycling caused the cathode particles to fracture and pulverize, driving cathode capacity fade and contributes to the decrease in overall cell performance.
Primary reference: Molleigh Preefer, Tanvir R. Tanim, Samuel S. Welborn, David N. Agyeman-Budu, Alison R. Dunlop, Stephen E. Trask, Eric J. Dufek, Andrew N. Jansen, Johanna Nelson Weker, "The Evolution of LiNi0.5Mn0.3Co0.2O2 Particle Damage from Fast Charging in Optimized, Full Li-Ion Cells", Journal of Physical Chemistry C, 126 (50) 21196 (2022).
Engineering alloying anodes that don't fracture
Increasing the power density of reusable batteries will allow electric vehicles to travel farther and cell phones and portable electronics to be used longer on a single charge. Scientists are interested in using higher power density lithium alloy materials as the battery anode instead of the commonly used graphite. Although these materials have higher power density, their capacity degrades quickly after a few recharging cycles. This is due to fractures caused by large increases in material volume when charged. Using operando X-ray microscopy we studied how bismuth enrichment causes fracture suppression. Bi-enriched SnSb alloy material form a liquid-like phase between the grain boundaries. X-ray microscopy revealed that this liquid-like phase can reduce the stress caused by volume change during charging by allowing the grains to slide by each other more easily through multiple thermodynamic mechanisms.
Primary reference: Qizhang Yan, Shu-Tin Ko, Andrew Dawson, David Agyeman-Budu, Grace Whang, Yumin Zhao, Mingde Qin, Bruce S. Dunn, Johanna Nelson Weker, Sarah H. Tolbert, Jian Luo, "Thermodynamics-driven interfacial engineering of alloy-type anode materials" Cell Reports Physcial Science, 3 (1) 100694 (2022).
Imaging battery heterogeneity using transmission X-ray microscopy
The use of synchrotron radiation-based characterization techniques, such as transmission X-ray microscopy combined with chemical analysis by X-ray absorption near-edge structure (TXM-XANES) at SSRL's BL 6-2, provides a holistic perspective on multiple battery materials. BL 6-2 serves as a hub of innovation, offering cutting-edge methods and techniques that delve deep into the crucial field of energy storage, facilitating a fundamental understanding of the intricate processes involved in such systems. For example, extensive studies have been conducted on LiNiO2-based cathodes for integration into Li-ion batteries. Here, a rational compositional design is critical for the utilization of LiNiO2-based cathodes with more than 90% nickel, which presents them as promising candidates as cathode material for the next generation of energy storage devices. A significant challenge, however, is the rational compositional design of high-nickel cathodes with precise compositions, especially when incorporating small amounts of dopants (<10%). This is due to the fact that critical elements such as cobalt and manganese are not well understood. A study at BL 6-2 systematically investigates electrochemical properties by varying charge energy density cut-offs. Using TXM measurements and TXM-XANES analysis, we are exploring the chemical and morphological properties of LiNiO2, LiNi0.95Co0.05O2, and LiNi0.95Mn0.05O2 cathodes at different states of charge. This study provides important insights into the design of high-energy, high-nickel cathodes and enhances our understanding of how to overcome the challenges of cobalt removal in these systems.
Public Lecture—X-rays Reveal Secret Life of Batteries
