Transport in Lithium Ion Batteries: Reconciling Impedance and Structural Analysis

Abstract

Diffusion simulations, electrochemical impedance spectroscopy, and fractal-based random walk analysis can give different values for ion transport in porous media. Comparing results from these different techniques can be used to understand the impact of electrolyte selection, ion–surface interactions, and specific structural features on rate performance of electrochemical devices so that the microstructure and chemistry can be systematically optimized.

Analysis of Charge Carrier Transport Toward Optimized Cathode Composites for All‐Solid‐State Li−S Batteries

“…Figure 3 shows the MacMullin numbers N M , representing the degree of reduction in the effective transport compared to σ 0 , which visualize the strong dependence on the conducting volume fraction. While the ionic transport in porous electrodes and separators in lithium‐ion batteries with liquid electrolytes is typically described by N M in the range of 5–20, [73,78,79,83] the N M values for both ion and electron transport found in this work are significantly higher, indicating tortuous and obstructed transport. Here, values of 17–220 are found for the ionic MacMullin numbers and 70–4 ⋅ 10 5 for the electronic MacMullin numbers.…”

“…The analysis of the effective transport properties of battery separators and electrodes clearly led to a deeper understanding of the underlying bottlenecks. Electrochemical and microscopic techniques, in combination with modeling of cathode composites, are established methods to characterize the influence of both ionic and electronic transport properties on the cell performance [76–86] . For example, the particle size of the active materials has been shown to impact the overall cell performance significantly, paving the way for optimization strategies [68,70,72] …”

“…Electrochemical and microscopic techniques, in combination with modeling of cathode composites, are established methods to characterize the influence of both ionic and electronic transport properties on the cell performance. [76][77][78][79][80][81][82][83][84][85][86] For example, the particle size of the active materials has been shown to impact the overall cell performance significantly, paving the way for optimization strategies. [68,70,72] In the case of all-solid-state LiÀ S cells, detailed studies and quantitative analysis of the effective transport properties in cathode composites were rarely reported.…”

Topological and network analysis of lithium ion battery components: the importance of pore space connectivity for cell operation

“…Similarly, other morphological and topological parameters are helpful when assessing surface interactions and effects. 31,35,41 Among such parameters are other Minkowski functionals, which correspond to a microstructure's surface area and curvature (described in detail in Sections 2 and 3 in the ESI †). Finally, lithium ion battery separators are just one example of a component in energy and environmental systems that can benefit from the topological and network analysis presented here.…”

The electrode tortuosity factor: why the conventional tortuosity factor is not well suited for quantifying transport in porous Li-ion battery electrodes and what to use instead

“…In this work, we use the standard definition for the tortuosity factor, τ, as stated in the following equation 11,12 :…”