Lithium-ion batteries (LIBs) are used in a wide range of applications, including portable electronics, electric vehicles, and grid-scale energy storage. The material composition of the electrodes and electrolyte play a critical role in determining LIB performance. In the cathode, a lithium-containing active material known as LiNi0.8Mn0.1Co0.1O2 (NMC-811) has attracted growing interest to its high specific capacity, high energy density, and reduced cobalt content. However, at high voltages NMC-811 reacts with the liquid electrolyte to form a cathode-electrolyte interphase (CEI) on the surface of the particles. If the CEI is unstable, it can lead to performance degradation as cycling continues. The mechanism of CEI formation remains unclear but is influenced by the NMC-811 particle morphology, cathode structure, voltage, and current density. To better understand these relationships, we are using 3D printing methods to fabricate three-dimensional (3D) NMC-811 cathodes for more fundamental CEI macro-scale characterization work. By producing 3D cathodes with controlled variations in porosity and internal cell pressure, this study investigates how these factors impact, CEI formation, current density profiles and overall NMC-811 cathode performance. My contribution to this research is focused on developing fabrication procedures for the 3D cathode structures, characterizing the cathode structures with optical profilometry and scanning electron microscopy (SEM) imaging, and analyzing the electrochemical behavior of CEI formation during cycling with incremental capacity (IC or dQ/dV) analysis. By using 3D printing techniques to support electrochemical characterization, this research aims to provide insight into the contributing factors of CEI formation in NMC-811 cathodes for LIBs. This work was supported in part by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy (DOE) through the Cathode–Electrolyte Interphase (CEI) Consortium.