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Technology

A model of electrochemical kinetics and flow was developed to identify operating conditions and rheological behavior that maximizes electrochemical performance. This model was applied to three active materials, two solid state lithium-ion compounds (LiFePO­4 and LiCoO2) and one redox solution (VO2+/VO2+). From this model, precisely tuned flow volumes, large yield stresses, large Navier slip coefficients, and two-phase-like active-materials were seen to produce the greatest electrochemical efficiencies. Ideally, plug-flow is achieved, which maximizes energetic efficiency and capacity over cycling because there is no residual charged material. However, since plug-flow in most cases is unobtainable, the following conditions were determined to maximize efficiency and capacity: (β - Navier Slip Coefficient, w - channel width, µp - plastic viscosity, τo - yield stress, and ῡ - mean axial velocity component) β > w/µp, τo > 100µpῡ/w, and an aliquot factor, pump volume compared to volume between the current collector and separator, between 0.5-0.75. Adhering to these a conditions, a discharge energy (as a percentage of the theoretical value) and an energetic efficiency >95% was observed.