A Coupled Optimization-oriented Reduced-order Aging Model for Graphite-LiFePO4 Li-ion Batteries under Dynamic Micorgrid Conditions

Accurate battery energy storage system (BESS) state of health estimation is important to microgrid optimization and energy management. This paper presents a coupled optimization-oriented reduced-order aging model for BESS under microgrid operating conditions. Three dominant physical degradation reactions, namely solid electrolyte interface growth, loss of active material and lithium plating are derived from the single particle model, where the three side reactions are coupled with each other. Five accelerated aging experiments are designed and conducted with various charging-rate and state of charge range to approximate the microgrid conditions. The proposed aging model is calibrated against the experimental data while an excellent fitting result is realized with most of relative errors less than 1%, indicating the accuracy of the reduced-order aging model. The contribution of the three side reactions on total capacity loss is consistent with the incremental capacity analysis, which proves the physical validity of the proposed model.