The distribution of relaxation times method (DRT) has been widely used to quantify the numbers and characterize the properties of the physico-chemical processes inside the Li-ion battery (LIB).
This illustration suggests that lithium-ion diffusion takes place by a cooperative interstitialcy or knock-on type mechanism in which the migrating interstitial Li-ion displaces the Li in the V layer into a neighbouring interstitial position in the alkali-metal layer.
When lithium inserts into or extracts from the active materials, the electrochemical reaction causes stress, and the DIS further assists the Li diffusion. The process that the stress and diffusion are strongly associated with each other is called mechanical–electrochemical coupling.
Based on the von Mises' theory of plasticity, Bower found the DIS was an important driving force for Li diffusion in lithium-ion batteries. [ 21] When lithium inserts into or extracts from the active materials, the electrochemical reaction causes stress, and the DIS further assists the Li diffusion.
An extended lithium-ion battery model is proposed, which simplifies the solid-liquid diffusion process compared with the full-order pseudo two-dimensional (P2D) model, in order to reduce computational complexity and enhance modeling speed. To simplify the model, the three-parameter method is utilized to simplify the solid-phase diffusion process.
Two physical processes determine the concentration of liquid lithium ions in the positive and negative regions: the first process is the diffusion motion based on concentration difference (Fick's law), and the other one is the motion of solid lithium ions in the positive and negative regions.
In order to simplify the liquid-phase diffusion process, Luo et al. 16 approximated the concentration of lithium ions in the liquid phase of the battery, using an exponential fitting to approximate the distribution of lithium ions in the positive and negative polar regions.
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