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 D_Li values reported in literature span over several orders of magnitude. Therefore, through the case study of LiNi_1/3Mn_1/3Co_1/3O₂ cathode AM, new physical insights are provided to explain the dispersion of D_Li 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 D_Li. 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.