Effects of electrode microstructure and Li2O2 growth on Li-air battery performance

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The lithium (Li)-air battery, with its high usable energy density, is a promising battery solution for electric vehicles and renewable energy storage. However, current Li-air technology suffers from low round-trip efficiency and energy capacity. The cathode microstructure and the formation of the discharge product (lithium peroxide, Li2O2) can have a significant influence on the performance of the battery. The project seeks to examine the impact of the electrode's material structure and the understanding of the evolution of Li2O2 formation on Li-air cell performance via an integrated project that combines theoretical modeling and experiments. The development of cost-effective, long lasting, and high energy-density batteries is a crucial step towards the electrification of the nation's light-duty vehicle transportation fleet. While the development of battery materials is an active research area, the design of electrode material's structure has been mainly based on empirical knowledge within industry. The structure-property-performance pathway developed here will provide a baseline understanding of how and why the electrode architecture leads to premature battery failure and will enable virtual design of novel electrode structures for improved performance. This project involves two engineering disciplines and departments and builds an exciting collaboration to enable an integrated research program on Li-air electrode design that provides diverse training and mentoring opportunities for students. The project will enable new course materials and laboratory demonstrations for the Nanomanufacturing for Energy and Transport Phenomena courses that the PIs teach. In addition, the PIs will continue to actively mentor undergraduate researchers and recruit women and under-represented minority students in STEM into their research groups. The community outreach will be extended to Philadelphia inner-city K-12 teachers and students through the Philly Science Festival and the Drexel GK-12/REU programs.The goal of this project is to develop a closely integrated program that includes novel electrode fabrication, high fidelity multi-scale modeling, post-mortem and in-situ characterization, electrochemical testing, and high-performance computing to probe the effects of electrode microstructure and Li2O2 growth morphology on cell performance. The project combines the expertise of PI Sun on multi-scale modeling of transport phenomena and Co-PI Kalra on fabrication of novel nanomaterials for electrochemical energy storage. Combining the pore-scale transport resolved model with the phase-field model for Li2O2 growth, the multi-scale modeling approach accounts for rate-dependent Li2O2 morphology and morphology-dependent properties and is capable of simulating the coupled growth, transport, and electrochemistry based on 3D real electrode microstructures. The integrated experimental program provides geometry/property inputs to the model and directly validates the model predictions for both the Li2O2 morphology at the nanoscale and the battery performance at the cell level. The validated model combined with graphics processing unit (GPU)-enabled computing will be used to perform large-scale, dynamic simulations over many cycles to discover knowledge pathways from structural design of porous electrode to cell performance assessment.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.