Understanding the Structural Transformations of Aluminum Foil Anodes during Electrochemical De(alloying) for Sustainable Lithium-ion Batteries

University Of Texas At Austin, Austin TX

Investigators

Abstract

Lithium-ion batteries will play an essential role in the transition to a sustainable economy by enabling the adoption of electric vehicles and renewable energy sources. However, as Lithium-ion batteries production grows rapidly, there are serious supply chain risks associated with the use of critical minerals (e.g., nickel, cobalt, graphite), which may restrict domestic production. Meanwhile, continuous improvements to lithium-ion battery performance – particularly energy density – are needed to meet the demands of commercial and military applications. To that end, it is imperative to develop battery anodes with higher lithium-storage capacity and lower cost than traditional graphite anodes. One promising, yet largely unexplored, alternative to graphite is aluminum (Al) foil, which can increase battery energy density by up to 40%, while improving safety, fast charging capability, and cost. However, research on Al foil anodes is in its infancy, and the fundamental mechanisms underlying the structural transformations of Al foil anodes during electrochemical (de)alloying must be uncovered to improve their poor cycle life. The fundamental research project will fill this knowledge gap through an interdisciplinary research approach that integrates materials science and electrochemical engineering. The project team will work with a local public school and the Ysleta Del Sur Pueblo reservation students and provide outreach on topics of the importance of clean energy technologies and opportunities in STEM careers. Aluminum foil anodes undergo fundamental changes in microstructure during battery formation (i.e., the first cycle), which largely control the electrochemical performance in subsequent cycles. It is hypothesized that the same mechanochemical processes, which cause dramatic structural changes during formation, when repeated continuously, are responsible for the rapid capacity loss during cycling. The goal of this research project is to understand: (i) how the structure and composition of the pristine Al foil anode, along with the kinetics of nucleation, phase transition, and solid-state diffusion, control the structural transformations during formation, and (ii) how the foil microstructure resulting from formation, and its evolution during cycling, control the failure modes of diffusional trapping and mechanical degradation. The dynamic electrochemical kinetics of these processes will be evaluated simultaneously with cycle life by conducting operando impedance spectroscopy in lithium iron phosphate full cells. An extensive suite of materials characterization techniques will be employed at various stages during formation and extended cycling to understand the mechanisms of structural transformation and identify the associated failure modes. These techniques will be used to interrogate Al foil anodes with diverse composition and microstructure, ranging from pure Al to nanocomposite foils. The structural transformations during formation will be correlated to operando kinetic measurements to establish quantitative relationships between initial foil structure/composition, electrochemical processing conditions, and the resulting foil microstructure. Finally, by correlating the microstructure after formation to the measured cycle life, and identifying the root causes of failure with advanced post-mortem materials characterization techniques, comprehensive processing-structure-performance relationships will be established to guide rational design of Al foil anodes with improved cycle life. This novel strategy of using the battery formation process as the final step of electrode manufacturing enables control of the microstructure through electrochemical engineering, which will lead to a paradigm shift in the research efforts to develop Al foil anodes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.