A New Insight into the Simulation of Blended Electrodes

Abstract

State-of-the-art lithium ion batteries often use blended electrodes to enhance performance. Many electric vehicles are using a mix of Lithium Manganese Nickel Cobalt oxide (NMC) and Lithium Manganese oxide (LMO) as positive electrodes and most newer batteries are using a mix of Silicon oxide (SiOx) and graphite (G) as negative electrodes. The blended nature of the electrodes is complicating electrode modeling and the diagnosability of cell degradation. Relatively few modeling studies are considering blended electrodes and those that do often assume that both components of the electrodes are subject to the same current.HNEI previously investigated the current distribution in blended electrodes by testing different materials in parallel to mimic the blending. We used a custom experimental set-up to test material couples with distinct (LFP+LMO), fully overlapping (NMC+NCA) and partially overlapping (G+SiOx and NMC+LMO) electrochemical responses. Results indicated that the constant current hypothesis for simulating blends might only be valid for materials whose electrochemical behaviors are separate or completely overlapping. In such cases, the current on each component of the blend is either equal to that of the applied current if the electrochemical active ranges are separated or pondered if the active ranges overlap. If the electrochemical behaviors do not fully overlap, the constant current hypothesis appears invalid. This work will present the mechanistic modeling results associated with these complex current distributions and showcase that a constant current approach, like the one used previously, might not be the most accurate.