Alignment Design in Consideration with Tertiary Current Distribution of Thick Electrodes

Abstract

With the increasing demands of lithium-ion batteries in electric vehicles (EVs) and energy storage systems (ESSs), high energy density and extreme fast-charging (XFC) characteristics are required. The easiest way to design high-energy-density cells is to make thick electrodes by minimizing separators and current collectors and maximizing active compounds, but for thicker electrodes, the kinetic losses increased with C-rate, and cycle stability deteriorated. On the sidewall of an electrode, there exists a current difference due to the current distribution by the location. This effect gets maximized in case of the thick electrode because there is a non-uniformity of the kinetics through the electrode thickness direction due to the difference of ionic and electronic conductivity within the pores of the electrode. Besides, different alignment margin of cathode and anode causes another current distribution on the sidewall.

In this study, pouch full cells with different alignment margin of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode and graphite anode are considered to investigate the difference of the current distribution. N/P ratio is set under 1 to induce complete intercalation of lithium-ion from the cathode into graphite anode so that distinguish the capacity from lithium-ion intercalation and lithium plating onto the surface of an anode. Through the calculation of the current distribution of the edge of the thick electrode, the optimal alignment design of the anode is suggested. There exists the optimal alignment margin of anode and cathode with respect to the dimension of the electrode and the current density (C-rate) applied into the electrode.