(554b) Advances in Mesoscale Modeling of Lithium-Ion Battery Cathodes

Lithium-ion battery electrodes (cathodes and anodes) mechanically degrade throughout battery cycling, degrading the performance of the entire battery. This mechanical degradation is driven by stresses that arise from electrochemical lithiation-induced swelling of the constituent active material particles coupled with the presence of polymeric binder materials and macroscale mechanical confinement. These phenomena inherently occur at the mesoscale (capturing hundreds of particles), where highly aspherical particles are packed into a bi-continuous percolated network that yields the macroscale behaviors that battery designers care about. Processes for manufacturing these electrodes can have a significant impact on battery performance.

In this talk we use mesoscale simulations to study the coupled electrochemical-mechanical response of lithium-ion cathodes. Mesoscale geometries are generated directly from image-based tomographic reconstruction data to capture the complexities of the electrode mesostructure. Verification of the numerical techniques and requirements for domain size and mesh resolution are shown. A variety of simulations that capture coupled electrochemical and mechanical effects are performed, including prediction of effective properties (electrical conductivity, tortuosity, mechanical moduli) and fully-coupled electrochemical-mechanical simulations of electrode charge and discharge at various rates. Two materials are studied; Lithium Cobalt Oxide (LCO) and Lithium Nickel Cobalt Manganese Oxide (NMC/NCM). The role of the conductive polymeric binder (polyvinylidene fluoride [PVDF] and carbon black [CB]) on electrical transport and the production of mechanical stresses is also explored.

Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.