The Impact of Microstructure Variation on Lithium-Ion Battery Charging Capability
Authors: Teel Hunter , Garrick Taylor R. , Sepe Mitchell , Lopata Joseph Steven , Srinivasan Srikant , Wang Fengkun , Zeng Yangbing , Shimpalee Sirivatch 
Published: December 2024

As electrification of the automotive industry progresses, there is an increasing consumer desire to reduce charge times and increase power and energy density of electric vehicles1. However, fast charge rates induce large gradients across the electrochemical components of these battery electrodes and can lead to adverse impacts2 at the active material and electrode level. Particularly at high states of charge, local anode potentials can drop significantly below the equilibrium potential3, and due to the proximity of the graphite equilibrium potential4,5 to 0V vs metallic Li at high states of lithiation, a risk that the anode potential drops below 0.0 V vs lithium metal exists, which can drive lithium plating on the active material2, reducing the electrochemically active surface area, impacting performance and heat generation6, and impacting lithium salt concentration present in the electrolyte.

By using electrochemical simulations, the onset of lithium plating can be predicted and used to set charging guidelines to reduce the risk of lithium plating. The pseudo-two-dimensional (P2D) model7–9 is a popular modeling method for capturing this behavior. With many effective media assumptions present translated to an average continuum impact, the P2D model can simulate rapid charge and capture a global equivalent onset of lithium plating for the anode. However, the P2D model lacks the ability to resolve any localized behaviors across the individual components due to local non-uniformities, as variation in the through plane direction only represents an average value across a slice of the full domain. Lopata10 developed a three-dimensional microstructure based (3DMS) modeling method, we employ here to simulate rapid charge events and capture what occurs locally across the electrochemical components while broadly agreeing with the established P2D’s model results.

With the 3DMS model, we are able to better predict the onset of local lithium plating and can use this knowledge to design more conservative charging conditions to delay the onset of lithium plating and improve the performance of these electrochemical systems. In this work, several similar microstructures are evaluated to determine the variation of the lithium plating onset time during fast charge operation. A small normal distribution for particle sizes are explored to drive variation in performance and are compared to a uniform particle size structure.

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