Operando probing ion and electron transport in porous electrodes

Utilization of thick and densified electrodes can efficiently increase battery energy density, which is critical for electrical transportation. However, the penalty from ion and electron transport significantly reduces the usable capacity of the electrode and limites the cell level energy density. Mechanistic understanding thus is required to improve electrode design. At present, no experimental method is capable of fully characterizing the kinetic processes, especially ion and electron transport, in porous electrode during dynamic charge and discharge. Here we for the first time measure the potential drops for ion and electron transport in a thick porous electrode during charge/discharge with pulse current cessation in a modified three-electrode cell. Our measurement suggests that capacity loss of a thick electrode at a high rate is highly related to both ion and electron transport potential drops. The potential drops caused by ion and electron transport disintegrates the chemical potential of the active materials in the electrode, thus stop or delay lithiation process of the active materials in the porous electrolde. Electrode capacity with phase transformation materials showed higher sensitivities to ion and electron transport potential drops compared to solid solution materials due to different chemical potential profiles upon lithiation.