Modeling the Impact of Additional Electrolyte on Lithium-Ion Convection Cell Performance
Authors: Weiss Trent A. , Gao Weiran , Drake Javit , Brushett Fikile R. 
Published: December 2024

Addressing growing energy demands while balancing sustainability imperatives, environmental stewardship, and economic viability stands as a paramount global challenge. Electrochemical technologies, particularly lithium-ion batteries (LIBs), are pivotal in achieving deep decarbonization by facilitating the deployment of electric vehicles and ensuring the reliable delivery of renewable electricity. However, current LIBs fall short of the rigorous requirements for widespread adoption in these critical sectors, as well as in emerging areas such as long-haul trucking and electric vertical takeoff and landing vehicles (eVTOLs).1,2 Breakthroughs in the science and engineering of LIBs are imperative to produce devices capable of delivering high performance without sacrificing safety and cost.

In addition to traditional materials-focused approaches, the development of new battery cell architectures, including the integration of electrolyte flow, presents a promising avenue for advancing performance. Prior mathematical modeling has shown forced electrolyte convection can significantly improve heat and mass transfer within LIBs, enabling operation under conditions that challenge conventional formats (e.g., high-rate charge/discharge).3,4 However, to exclude convoluting secondary effects, these studies simplify balance-of-plant systems which, in turn, may not fully describe practical operation. Specifically, these simulations use large electrolyte tanks which buffer against bulk concentration and temperature changes, aiding in the fundamental analyses. Notably, scaling under these conditions could potentially lead to cost-prohibitive and thus impractical systems.5

In this presentation, we investigate the impact of additional electrolyte volume on the complex interplay between electrochemical performance enhancements, fluid dynamic losses, and economic incentives in a convection cell. Through physics-based electrochemical modeling, we demonstrate that electrolyte convection alone can alleviate mass transport limitations even under extreme discharge rates, obviating the need for added electrolyte. In contrast, we find that extra electrolyte is necessary as a heat sink to mitigate cell temperature rise. We extend these results to practical operating conditions, where we conduct a preliminary system-level energy analysis to evaluate the energetic penalties associated with scaling this new architecture. Our findings suggest there exists a narrow added electrolyte range that effectively reduces thermal transport limitations without significantly increasing the system weight and volume. We also construct an accompanying technoeconomic framework to estimate the associated cost tradeoffs, illustrating the disparity between energy-optimized and cost-optimized designs. Ultimately, this work represents an initial exploration into practical design and operation considerations for convection batteries, laying the groundwork for future application-specific investigations.

References:

(1) Fleming, K. L.; Brown, A. L.; Fulton, L.; Miller, M. Curr. Sustain. Energy Rep.
2021, 8 (3), 180–188.

(2) Dixit, M.; Bisht, A.; Essehli, R.; Amin, R.; Kweon, C.-B. M.; Belharouak, I. ACS Energy Lett.
2024, 9 (3), 934–940.

(3) Gao, W.; Orella, M. J.; Carney, T. J.; Román-Leshkov, Y.; Drake, J.; Brushett, F. R. J. Electrochem. Soc.
2020, 167 (14), 140551.

(4) Gao, W.; Drake, J.; Brushett, F. R. J. Electrochem. Soc.
2023, 170 (9), 090508.

(5) Schmuch, R.; Wagner, R.; Hörpel, G.; Placke, T.; Winter, M. Nat. Energy
2018, 3 (4), 267–278.