3D Architected Battery Electrodes for Exploring Battery Kinetics from Nano to Millimeter

The ability to design a particular geometry of porous electrodes at multiple length scales in a lithium-ion battery can significantly and positively influence battery performance because it enables control over kinetics and trajectories of ion and electron transport. None of the existing methods of engineering electrode structure is capable of creating 3D architected electrodes designed with independent and flexible form-factors at multiscale that are also resilient against cell packaging pressure. In addition, battery kinetics coupled at multiscale from ion transport in an electrolyte to solid electrolyte interphase (SEI) growth has only been studied by numerical simulations, but has never been experimentally explored. In this thesis, we demonstrate an additive manufacturing technique to engineer porous electrode structure in 3D and explore battery kinetics at multiscale. First, we develop 3D architected carbon electrodes, whose structural factors are independently controlled and whose dimensions span microns to centimeters, using digital light processing and pyrolysis. These free-standing lattice electrodes are disordered graphitic carbon composed of several stacked graphitic layers that are mechanically robust. Galvanostatic cycling using these architected carbon electrodes showed sloping capacity, typically observed in pyrolyzed carbon electrodes. We discuss the modified rate performance of the 3D architected carbon electrodes in the framework of ion transport kinetics in the electrode vs. electrolyte and overpotential, enabled by controlling structural factors of battery electrodes, including porosity, surface morphology, electrode thickness, and beam diameter, whose length scales range from nano to millimeter. We then explore battery kinetics associated with SEI using deterministic, mechanically resilient, and thick 3D architected carbon electrodes, which allow us to study the formation, structure-resistance relationship, and position-dependent growth of SEI by combining the newly developed in operando DC-based technique and post-characterization using secondary ion mass spectroscopy. The amount of Li in SEI agrees with capacity losses, and the amount of F in SEI showed a strong linear correlation with SEI resistance evolutions. The position-dependent SEI growth was experimentally explored; the Li amount in SEI along the electrode thickness agrees with the simulation results in prior work, but the F amount in SEI showed the opposite tendency, suggesting modeling of multilayer SEI is necessary to predict precisely battery aging especially for thick electrodes. Our work demonstrates the use of 3D architected electrodes as a model system to explore multiscale kinetics in Li-ion batteries.