The use of thick electrodes in Li-ion batteries has received widespread interest in recent year as a promising way for energy densisty enhancement and cost reduction, but it faces the instrinsic challenge of slow transport kinetics due to the increased ion diffusion distance between cathode and anode. It is thus important to carefully optimize the microstructure of thick electrodes to improve their rate performance for specific applications. Here we report an efficient computational approach to predict and optimize the performance of thick electrodes as an alternative to the pseudo-2D simulation technique, which is the de-facto modeling method for battery design at the cell-level. We derived an analytical model for predicting the charge/dicharge capacity of the battery cells based on the observations that a pseudo-steady state of ion transport in electrolyte is typically established in thick electrodes during discharge/charge process. As shown in Figure 1a, the model provides predictions on the depth of discharge of battery cells within a range of discharge rate and cell configuration that are in very good agreement with the psedudo-2D battery simulations, but only consumes a negligible amount of computational cost. As a demonstration of its utility, the model is used to efficiently predict the dependence of a cell's specific energy on the cathode porosity and thickness given a required specific power and identify the optimal parameter values (Figure 1b). Our method makes it feasible to design and optimize non-uniform electrode structures that involves a large number of parameters in the design space.

Figure 1 (a) Comparison of depth of discharge (DoD) predicted by pseudo-2D simulation and our analytical model for various electrode thickness in half or full cell configurations. (b) Contour plot of cell-level specific energy of a full cell as a function of cathode porosity and thickness at a given power density. The thick line represents the maximal specific energy at different cathode thicknesses.