(544e) A Multiscale Electro-Chemical Model for Simulating Dendrite Formation in Lithium-Ion Batteries

The growing market demand for Lithium-ion batteries (LIBs) with a high energy density has given an impetus to a plethora of studies investigating the utilization of Lithium anode, which is considered as the ‘Holy-Grail’ anode due to its high energy density (∼ 3860 mAh/g) as compared to traditional graphite anodes (∼ 372 mAh/g) [1]. However, commercial application of Li metal anode has not been possible because it is plagued by irregular Li deposition, which causes dendrite formation and results in poor cycling efficiency, capacity fade, and in extreme cases, short-circuiting of batteries [2]. Previous studies show that dendrite formation is majorly affected by microscopic battery parameters [1] (i.e., mechano-chemical properties of the SEI species), and macroscopic operating conditions (i.e., cell voltage, current density, and Li-ion concentration) [3]. However, the complex interaction between these two types of factors (i.e., macroscopic and microscopic) has not been adequately addressed in the literature.

Inspired by this, we have constructed a multiscale model that combines a high-fidelity kMC simulation with an electrochemical continuum model, which in this case is a modified form of the single-particle model (SPM) [4]. Specifically, the kMC model employs a series of microscopic events like the desolvation of Li-ions from the electrolyte, their diffusion in the SEI,¹[6] and finally the electrodeposition of Li-ions on the anode to simulate the microscopic dendrite formation phenomenon [5],[6]. The electrochemical model considers Fickian diffusion of Li-ions in the electrolyte region to trace the spatio-temporal evolution of , and then couples this with various equations to determine cell voltage and the state of charge (SOC). The proposed multiscale model is simulated for varying current densities at different values of initial Li-ion concentration to investigate its effect on microscopic dendrite formation (quantified using roughness), and the temporal evolution of various macroscopic variables. Furthermore, the simulation results for dendrite growth and SOC (which is a measure of the charging status of LIBs) are successfully validated with experimental results from the literature.

Overall, the proposed multiscale electrochemical model can (a) generate the evolution of macroscopic variables such as current density, Li-ion concentration, cell voltage, and SOC, (b) explain their effect on the microscopic spatio-temporal evolution of dendrites (kMC model), and (c) be extended to simulate multiple charge-discharge cycles to help devise effective dendrite mitigation strategies in future studies.

Literature Cited:

1. Qin X, Shao M, Balbuena PB. Elucidating mechanisms of Li plating on Li anodes of lithium-based batteries. Electrochemica Acta. 2018 Sep 10; 284:485-94.
2. Wen J, Yu Y, Chen C. A review on lithium-ion batteries safety issues: existing problems and possible solutions. Materials Express. 2012 Sep 1;2(3):197-212.
3. Hao F, Verma A, Mukherjee PP. Mechanistic insight into dendrite–SEI interactions for lithium metal electrodes. Journal of Materials Chemistry A. 2018;6(40):19664-71.
4. Zhang D, Popov BN, White RE. Modeling lithium intercalation of a single spinel particle under potentiodynamic control. Journal of the Electrochemical Society. 2000 Mar 1;147(3):831.
5. Sitapure N, Lee H, Ospina‐Acevedo F, Balbuena PB, Hwang S, Kwon JS. A computational approach to characterize formation of a passivation layer in lithium metal anodes. AIChE Journal. 2021 Jan; 67(1): e17073.
6. Angarita-Gomez S, Balbuena PB. Insights into lithium ion deposition on lithium metal surfaces. Physical Chemistry Chemical Physics. 2020;22(37):21369-82.