In the quest for high performing battery technologies, conversion cathode materials often stand out for producing high energy densities. Combined with non-planar electrode geometries, such as 3D/2.5D battery architectures, conversion cathodes can achieve both high power and energy densities. However, electrochemical conversion processes are often mechanically abusive at the mesoscale, with significant changes in particle volumes leading to high stresses within the electrode. While previous studies have investigated mesoscale stress impacts for a variety of planar cathode materials, the added complication of non-planar electrode geometries complicates our previous understanding, particularly when the geometric features are on the same size as a mesoscale representative volume element.In this paper, we demonstrate a coupled electrochemical-mechanical model of a 2.5D pillar conversion cathode system. The mesoscale geometry is generated using discrete element models. The electrochemical model consists of species and electrical transport coupled by Butler-Volmer interfacial reaction kinetics. A moving mesh technique is implemented to track the conversion reaction front and separate reacted from unreacted materials. The impact of the electrochemical reaction leads to the generation of mechanical stresses within the electrode structure. We demonstrate how the mechanical response differs between planar and non-planar electrode geometries and explore the role of the geometric feature sizes on stress localization.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.