Coupled Electrochemical-Thermal Simulations and Validation of Minichannel Cold-Plate Water-Cooled Prismatic 20 Ah LiFePO4 Battery

This paper discusses the quantitative validation carried out on a prismatic 20 Ah LiFePO4 battery sandwiched between two minichannel cold-plates with distributed flow having a single U-turn. A two-way coupled electrochemical-thermal simulations are performed at different discharge rates (1–4 C) and coolant inlet temperatures (15–35 °C). The predicted battery voltage response at room temperature (22 °C) and the performance of the Battery Thermal Management System (BTMS) in terms of the battery surface temperatures (maximum temperature, Tmax and temperature difference, ΔT) have been analyzed. Additionally, temperature variation at ten different locations on the battery surface is studied during the discharge process. The predicted temperatures are compared with the measured data and found to be in close agreement. Differences between the predicted and measured temperatures are attributed to the assumption of uniform heat generation by the Li-ion model (P2D), the accuracy of electrochemical property input data, and the accuracy of the measuring tools used. Overall, it is suggested that the Li-ion model can be used to design the efficient BTMS at the cell level.

Thermodynamic Analysis and Experimental Investigation of Al and F Removal from Sulfuric Acid Leachate of Spent LiFePO4 Battery Powder

The co-precipitation thermodynamics of the Li+–Fe2+/Fe3+–Al3+–F−–SO42−–PO43−–H2O system at 298 K is studied, aiming to understand the precipitation characteristics. Based on the principle of simultaneous equilibrium and the mass action law, the missing Ksp values of AlF3 and FeF3 were estimated. The results of thermodynamic calculation demonstrate that Al3+ and F− in the sulfuric acid leachate could be preferentially precipitated in the form of AlPO4 and FeF3 by the precise adjustment of the final pH value. Only a small amount of P and Fe was lost by the precipitation of Fe3(PO4)2·8H2O, FePO4, and Fe(OH)3 during the purification process. Controlling the oxidation of ferrous ions effectively is of critical significance for the loss reduction of P and Fe. Precipitation experiments at different pH value indicated that the concentration of Al3+ and F− in the leachate decreased as the final pH value rose from 3.05 to 3.90. When the final pH value was around 3.75, aluminum and fluoride ion impurities could be deeply purified, and the loss rate of phosphate ions and iron ions could be reduced as much as possible. Relevant research results can provide theoretical guidance for the purification of leachate in the wet recycling process of lithium-ion batteries.