锂离子电池的精确建模和状态估计对于电动汽车电池管理系统非常重要,准二维(P2D)电化学模型由于计算复杂,难以直接应用于电池管理的参数在线估计和实时控制中.本文基于多孔电极理论和浓度理论,提出一种考虑锂离子液相动力学的简化准二维(SP2D)模型.忽略锂离子孔壁流量沿电极厚度方向的变化求解SP2D模型所描述的锂离子电池锂浓度分布,基于锂离子电池电化学平均动力学行为求解固相和液相电势变化,推导出电池电压计算的简化表达式;采用恒流、脉冲以及城市循环工况放电电流对比分析了严格P2D模型与SP2D模型的终端电压和浓度分布.结果表明:SP2D模型在保持较高计算精度的同时,可显著提高计算效率.%It is very important to accurately model Li-ion battery and estimate the corresponding parameters that can be used for battery management system (BMS) of electric vehicles (EVs). However, the rigorous pseudo-two-dimensional (P2D) model of Li-ion battery is too complicated to be adopted directly to online state estimation and real-time control of stage-of-charge in BMS applications. To solve this problem, in this study we present a simplified pseudo-two-dimensional (SP2D) model by the electrolyte dynamic behaviors of electrochemical battery model, which is based on the porous electrode theory and concentration theory. First, the classical concentration equations of Li-ion battery P2D model are investigated and introduced, based on which, the approximated method of describing the concentration distributions of Li-ion battery described by the SP2D model is given by ignoring the variation of Li-ion wall flux density across the electrode thickness; then, the Li-ion battery terminal output voltage, the solid phase concentration and potential diffusion, the electrolyte concentration and potential distribution can be calculated based on the averaged electrochemical dynamic behaviors of Li-ion battery. Moreover, by employing some concentration assumptions: 1) the solid-phase lithium concentration in each electrode is constant in spatial coordinate x, and uniform in time; 2) the exchange current density can be approximated by its averaged value; 3) the total amount of lithium in the electrolyte and in the solid phase is conserved; with the averaged dynamics of SP2D model, the simplified calculation expression for Li-ion battery terminal voltage is derived. Finally, a case study of Sony NMC 18650 Li-ion battery is conducted, and the simulated comparisons among the battery voltages at different-C-rate galvanostatic discharges, and the related electrolyte concentration of Li-ion at 1 C-rate are conducted. Moreover, the proposed SP2D model is used to predict the battery voltage and electrolyte concentration distribution with respect to the P2D model under hybrid pulse power characterization condition and urban dynamometer driving schedule condition, and the corresponding test data are used to verify the accuracy of the SP2D model. It is observed that the simulated data of SP2D model are in good accord with those of the P2D model and test curve under these two operation conditions, which further validates the effectiveness of the proposed electrochemical model of Li-ion battery. Accordingly, the proposed SP2D model in this paper can be used to estimate real-time state information in advanced battery management system applications, and can improve the calculation efficiency significantly and still hold higher accuracy simultaneously than that from the P2D model.
展开▼
