“Zero” Porosity High Loading NMC622 Positive Electrodes for Li-Ion Batteries

LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) is a widely used positive electrode material for lithium-ion batteries, including electric vehicles. In this work, we investigated the effects of porosity, ranging from “zero” to the typical 35%, on the electrochemical behavior of high-loading NMC622 electrodes. Although it is well known that the energy density of the electrode increases with increasing areal capacity and decreasing porosity, NMC-positive electrodes with exceedingly low porosity (e.g., near zero) and high loading (e.g., 4 mAh cm⁻²) have not been investigated. Here, we report an intriguing observation that the “zero porosity” NMC electrode can have higher capacity at low C-rates, and the volumetric energy density significantly increases to 1739 Wh l⁻¹ compared to 805 Wh l⁻¹ of conventional electrodes of 35% porosity. We performed cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to help understand this observation. This work provides new insights into the effects of porosity on the electrochemical behavior of high-loading positive electrodes.