Mesoscale Effects in the Extraction of the Solid-State Lithium Diffusion Coefficient Values of Battery Active Materials: Physical Insights from 3D Modeling

During the screening of active materials (AMs) for lithium-ion batteries, the solid-state lithium diffusion coefficient (D-Li) is one of the most relevant descriptors used to evaluate the relevance of an AM candidate. However, for a given compound, the DLi values reported in literature span over several orders of magnitude. Therefore, through the case study of LiNi1/3Mn1/3Co1/3O2 cathode AM, new physical insights are provided to explain the dispersion of DLi values obtained through galvanostatic intermittent titration technique (GITT). For the first time, a 3D electrochemical model (accounting for the carbon-binder domain) fed with experimental inputs is capable of highlighting the limitations of the most widely used equation for deriving DLi. Through our model, we show that these limitations arise from the influence of the carbon-binder domain location throughout the electrode and the non-homogeneous AM phasedistribution and particle size.