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Understanding the current response at an electrode from suspended solid particles in an electrolyte is crucial for developing materials to be used in semi-solid electrodes for energy storage applications. Here, an analytical model is proposed to predict and understand the current response from non-disintegrable solid particles at a rotating disk electrode. The current is shown to be limited by a combination of ion diffusion within the solid particle and the mean residence time of the particle at the rotating disk electrode. This results in a relationship between current and angular frequency of$I\propto {\omega }^{3/4},$instead of the classical$I\propto {\omega }^{1/2}$predicted by Levich theory. Specifically, the current response of Li₄Ti₅O₁₂(LTO) microparticles suspended in a non-aqueous electrolyte of lithium hexafluorophosphate (LiPF₆) in ethylene carbonate: diethyl carbonate (EC:DEC) was determined experimentally and compared favorably with predictions from the proposed analytical model using fitting parameters consistent with the experimental conditions.

2D nanosheets have been widely explored as electrode materials owing to their extraordinarily high electrochemical activity and fast solid‐state diffusion. However, the scalable electrode fabrication based on this type of material usually suffers from severe performance losses due to restricted ion‐transport kinetics in a large thickness. Here, a novel strategy based on evaporation‐induced assembly to enable directional ion transport via forming vertically aligned nanosheets is reported. The orientational ordering is achieved by a rapid evaporation of mixed solvents during the electrode fabrication process. Compared with conventional drop‐cast electrodes, which exhibit a random arrangement of the nanosheets and obvious decrease of rate performance with increasing thickness, the electrode based on the vertically aligned nanosheets is able to retain the original high rate capability even at high mass loadings and electrode thickness. Combined electrochemical and structural characterization reveals the electrode composed of orientation‐controlled nanosheets to possess lower charge‐transfer resistances, leading to more complete phase transformation in the active material.

Nanostructured materials can exhibit phase change behavior that deviates from the macroscopic phase behavior. This is exemplified by the ambiguity for the equilibrium phases driving the first open‐circuit voltage (OCV) plateau for the lithiation of Fe₃O₄nanocrystals. Adding complexity, the relaxed state for Li_xFe₃O₄is observed to be a function of electrochemical discharge rate. The phases occurring on the first OCV plateau for the lithiation of Fe₃O₄nanocrystals have been investigated with density functional theory (DFT) through the evaluation of stable, or hypothesized metastable, reaction pathways. Hypotheses are evaluated through the systematic combined refinement with X‐ray absorption spectroscopy (XAS), X‐ray diffraction (XRD) measurements, neutron‐diffraction measurements, and the measured OCV on samples lithiated tox= 2.0, 3.0, and 4.0 in Li_xFe₃O₄. In contrast to the Li–Fe–O bulk phase thermodynamic pathway, Fe⁰is not observed as a product on the first OCV plateau for 10–45 nm nanocrystals. The phase most consistent with the systematic refinement is LiFe₃O₄, showing Li+Fe cation disorder. The observed equilibrium concentration for conversion to Fe⁰occurs atx= 4.0. These definitive phase identifications rely heavily on the systematic combined refinement approach, which is broadly applicable to other nano‐ and mesoscaled systems that have suffered from difficult or crystallite‐size‐dependent phase identification.