Published in Nature Communications, 2024
A. Weng*, Omar Y. Ahmed*, Gabriel Ehrlich, Anna Stefanopoulou (* : equal contribution)
We find that U.S. vehicle assembly plants that have fully transitioned from gas engine to electric vehicle assembly have required higher labor intensity. It suggests that more, not fewer, workers are needed for electric vehicle assembly.
Published in Journal of Dynamic Systems, Measurement, and Control, 2024
A. Weng, Hamidreza Movahedi, Clement Wong, Jason B. Siegel, Anna Stefanopoulou
We propose an analytical framework describing how initial capacity and resistance variability in parallel-connected battery cells may inflict additional variability or reduce variability while the cells age. Using this framework, we demonstrate that current imbalance can cause convergent degradation trajectories, consistent with previous reports. However, we also demonstrate that different degradation assumptions, such as those associated with SOC imbalance, may cause divergent degradation. We finally highlight the role of different cell chemistries, including different OCV function nonlinearities, on system behavior, and derive analytical bounds on the SOC imbalance using Lyapunov analysis.
Published in Joule (Commentary), 2024
A. Weng, Eric Dufek, Anna Stefanopoulou
We highlight the central role that the battery management system (BMS) plays in enabling battery passports to predict remaining useful life (RUL). With an accurate BMS, battery passports can help boost consumer confidence in the used electric vehicle market. With an accurate, physics-based BMS, repurposers can evaluate second-life application feasibility and fulfill the promise of a circular battery economy.
Published in Journal of the Electrochemical Society, 2023
A. Weng, Everardo Olide, Iaroslav Kovalchuk, Jason B. Siegel, Anna Stefanopoulou
This work bridges the gap between electrochemical descriptions of SEI growth and applications toward improving industrial battery manufacturing process control where battery formation is an essential but time-consuming final step. We envision that the formation model can be used to predict the impact of formation protocols and electrolyte systems on SEI passivation and resulting battery lifetime.
Published in Frontiers in Energy Research, 2023
A. Weng, Jason B. Siegel, Anna Stefanopoulou
We present a method for collecting and analyzing full cell near-equilibrium voltage curves for end-of-line manufacturing process control. The method builds on existing literature on differential voltage analysis (DVA or dV/dQ) by expanding the method formalism through the lens of reproducibility, interpretability, and automation. Our model revisions introduce several new derived metrics relevant to manufacturing process control, including lithium consumed during formation and the practical negative-to-positive ratio, which complement standard metrics such as positive and negative electrode capacities. To facilitate method reproducibility, we reformulate the model to account for the “inaccessible lithium problem” which quantifies the numerical differences between modeled versus true values for electrode capacities and stoichiometries. We finally outline key data collection considerations, including C-rate and charging direction for both full cell and half cell datasets, which may impact method reproducibility. This work highlights the opportunities for leveraging voltage-based electrochemical metrics for online battery manufacturing process control.
Published in Joule, 2021
A. Weng, Peyman Mohtat, Peter M. Attia, Valentin Sulzer, Suhak Lee, Greg Less, Anna Stefanopoulou
We identify a scalable method for predicting the effect of new formation protocols on cycle life. The method is obtained directly at the end of the manufacturing line and can be deployed immediately in mass production settings to improve diagnostics of new formation protocols.
A. Weng, J. B. Siegel, G. Less, A. Stefanopoulou. “Closed-loop battery manufacturing process control via end-of-line diagnostic features,” U.S. Patent App. 18/673,707, 2024/06/14
A. Stefanopoulou, I. Kovalchuk, V. Tran, J. B. Siegel, E. Olide, A. Weng. “Battery Formation Diagnostics Using Real-Time Expansion,” US Patent App. 63/469,269, 2023/05/09
A. Stefanopoulou, A. Weng, P. Mohtat, P. M. Attia, V. Sulzer, S. Lee, G. Less. “Early-Life Diagnostics For Fast Battery Formation Protocols And Their Impacts To Long-Term Aging,” US Patent App. 17/859,390, 2023/01/26