Engineering hierarchical pore network for Li-ion battery electrodes

At higher charging and discharging rates, Li+ diffusion in the electrodes of lithium batteries is severely restricted, resulting in a significant decrease in battery performance. To reduce the diffusion limitations, engineering pore structure of electrodes can be an efficient approach. In this work, a LiCoO2 cathode is taken as a model electrode, the hierarchical pore network of the cathode with low-tortuosity pores is engineered with the aid of a two-dimensional model. The low-tortuosity pores act as "highways" for the transport of Li+, and their porosity and diameter are optimized to achieve the maximum energy density at high discharge rates. The optimal porosity of low-tortuosity pores is highly dependent on the diameter of low-tortuosity pores, and a diameter of low-tortuosity pores less than 10 μm is preferable. The preferable hierarchically structured electrode can be 45.9%-91.4% higher in energy density when the electrode thickness is 200 μm and the total porosity is 0.36. Besides, optimizing hierarchically structured electrodes is unnecessary when the diffusion limitation of Li+ is weak (e.g., electrode thickness ≤50 μm and total porosity ≥0.48). This work should provide some guidance to engineer the hierarchical pore network for high-performance Li-ion battery electrodes. © 2021, Editorial Board of CIESC Journal. All right reserved.