Lithium-ion batteries are the prevailing choice for electric vehicles, but their raw materials are expensive, and their supply chains can be unreliable. An alternative solution is sodium-ion batteries, which can potentially address some of these challenges.
Researchers used transmission electron microscopy (left) and X-Ray techniques (right) to observe the defects that led to failure in sodium-ion battery cathodes. Eliminating these defects will allow these batteries to last longer. Image Credit: Argonne National Laboratory
However, these batteries exhibit a rapid decline in performance with repeated charging and discharging cycles, presenting a significant hurdle for their commercial adoption.
In a recent study, researchers employed a combination of electron microscopy and X-Ray scattering techniques to identify the root cause of this performance decline: defects introduced during the production of the cathode material. This newfound understanding will empower researchers to design improved cathodes, ultimately leading to longer-lasting sodium-ion batteries and facilitating their broader use in the market.
The Impact
Leveraging the findings of this study, battery developers could potentially craft cathodes for sodium-ion batteries that are nearly defect-free. Such innovations have the potential to result in lower-cost batteries compared to current lithium-based ones, coupled with extended lifespans.
This technology could pave the way for more economical electric vehicles offering increased driving ranges and quicker charging times. Additionally, reduced battery expenses may translate to decreased costs for energy storage within the electric grid.
Summary
This research, conducted by a collaborative team from Argonne National Laboratory, the University of Wisconsin-Milwaukee, and Stanford University, hinged on integrating various experimental techniques. The study involved the investigation of newly synthesized cathode materials using research tools at two Department of Energy (DOE) Office of Science user facilities: high-energy X-Ray beams at the Advanced Photon Source and the analytical capabilities of the Center for Nanoscale Materials.
The synthesis process entails a gradual heating of the cathode materials followed by rapid cooling. By employing transmission electron microscopy and surface X-Ray diffraction to observe this material throughout the process in situ, scientists deduced that defects emerge during the cooling phase.
These defects are responsible for the cathode particles cracking and a subsequent performance decline, which is exacerbated when cathodes are charged rapidly or at elevated temperatures. Ultimately, this can lead to a "structural earthquake" within the cathode, resulting in catastrophic battery failure.
Equipped with this understanding, battery developers can modify the synthesis conditions for batteries and effectively manage defects within sodium-ion battery cathodes. This research capitalizes on the combined capabilities of both user facilities to obtain real-time insights into material transformations during controllable changes in the sample environment.
These insights underscore the critical significance of eradicating these defects to guarantee the sustained and stable cycling of sodium-ion batteries at higher voltage levels.
Funding
This research received funding from the DOE Vehicle Technologies Office and was conducted at two DOE Office of Science user facilities: the Advanced Photon Source and the Center for Nanoscale Materials.
Journal Reference:
Xu, G.-L., et al. (2022). Native lattice strain induced structural earthquake in sodium layered oxide cathodes. Nature Communications. doi.org/10.1038/s41467-022-28052-x.