Fast algorithm for calculating the surface concentration of spherical particles for lithium-ion battery simulations

Abstract The continued advancement of lithium ion batteries for transportation applications requires addressing two key challenges: increasing energy density and providing fast charging capabilities. The first of these challenges can be met in part through the use of thicker electrodes, which reduce the electrochemically inactive mass of the cell. However, implementation of thick electrodes inherently presents a trade-off with respect to fast charging capabilities. As thickness is increased, transport limitations exert greater influence on battery performance and reduce the ability of the battery to meet aggressive charge conditions. This trade-off can manifest over multiple length scales. At the particle-scale, interactions between solid diffusion and reaction kinetics influence the effective storage of lithium within the active material. At the electrode scale, diffusion limitations can lead to local variations in salt concentrations and electric potential. These short-range and long-range effects can combine to influence local current and heat generation. In the present work, a pseudo-2D lithium ion battery model is applied to understand how active material particle size, porosity, and electrode thickness impact local field variables, current, heat generation, and cell capacity within a single cell stack. COMSOL Multiphysics 5.2 is used to implement the pseudo-2D model of a lithium ion battery consisting of a graphite negative electrode, polymer separator, and lithium transition metal oxide positive electrode. Lithium hexafluorophosphate (LiPF6) in 1:1 ethylene carbonate (EC) and diethylene carbonate (DEC) was used as the electrolyte. The model was built assuming that the active particles are representative spherical particles. The governing equations and boundary conditions were set following the common Newman model. Cell response under varied combinations of charge and discharge cycling is assessed for rates of 1C and 5C. Aggressive charge and discharge conditions lead to locally elevated C-rates and attendant increases in local heat generation. These variations can be impacted in part by tailoring electrode structures. To this end, results for parametric studies of active material particle size, porosity, and electrode thickness are presented and discussed.

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An Interconnected Observer for Concurrent Estimation of Bulk and Surface Concentration in the Cathode and Anode of a Lithium-ion Battery

IEEE Transactions on Industrial Electronics ◽

10.1109/tie.2018.2793194 ◽

2018 ◽

Vol 65 (9) ◽

pp. 7311-7321 ◽

Cited By ~ 15

Author(s):

Anirudh Allam ◽

Simona Onori

Keyword(s):

Lithium Ion Battery ◽

Lithium Ion ◽

Surface Concentration ◽

Concurrent Estimation

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A Coupled Finite Volume Method for Particle Scale Electrochemical Modeling of Lithium-Ion Batteries

Volume 6A: Energy ◽

10.1115/imece2013-65774 ◽

2013 ◽

Cited By ~ 3

Author(s):

Bradley L. Trembacki ◽

Ajay Vadakkepatt ◽

Sanjay R. Mathur ◽

Jayathi Y. Murthy

Keyword(s):

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Finite Volume ◽

Electrostatic Potential ◽

Thermal Transport ◽

Effective Properties ◽

Porous Electrode ◽

Lithium Ion ◽

Spherical Particles ◽

Implicit Time

Lithium-ion batteries are commonly simulated using a volume-averaged formulation (porous electrode theory), using effective properties such as conductivity and diffusivity and assuming a simplified spherical geometry of the electrode particles. Microscopic scans show that the shape, size, and orientation of the particles is highly variable, which can significantly alter pathways for ionic, electronic, or thermal transport. Unlike a volume-averaged spherical formulation, a particle-scale simulation applied to a real electrode geometry is able to predict localized phenomena and enables the optimization of material morphology to maximize battery performance. The physical processes involved in lithium-ion battery simulations are electron, ion, mass, and thermal transport, and a particle-scale simulation yields the spatial variation of Li concentration, electrostatic potential, and temperature throughout time as the battery discharges. In this paper we develop a fully-coupled finite volume methodology for the simulation of the electrochemical equations in a lithium ion battery cell. An unstructured mesh of arbitrary convex polyhedral cells is used to mesh synthetic spherical particles and electrolyte. Second-order discrete conservation equations for Li ion transport and electrostatic potential are developed. Butler-Volmer kinetics are included at the electrode/electrolyte interface. A block-sparse unstructured linear system results from the discretization of the governing equations, and is solved using a BiCGSTAB solver with an algebraic multigrid pre-conditioner. A fully-implicit time stepping scheme is used to compute transients. Our methodology fully couples species, electrostatics, and Butler-Volmer kinetics in a stable and efficient computational algorithm. We demonstrate that it is more stable and takes less time to converge than a conventional sequential solution procedure.

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