锂离子电池电化学降阶模型性能对比

Comparative study of reduced-order electrochemical models of the lithium-ion battery

可靠而高效的锂离子电池模型是电池管理系统状态估计与故障诊断的基础.采用偏微分方程描述的准二维(P2D)机理模型的参数多,虽然模型准确性高,但计算费时,需降阶处理才能更好地应用在车载电池管理系统.为此,基于相同模型参数,建立锂离子电池的P2D模型及其降阶模型——单粒子模型(SPM)和集总粒子模型(LPM),对三种电化学机理模型电池端电压的计算精度和时间进行对比研究.结合多孔电极模型和浓溶液理论,基于电池均匀电流密度的假设条件,按照电极固相和液相体积比重新分配电流密度,推导了由液相锂离子浓度分布差异所导致的液相浓差过电压和欧姆内阻,补偿LPM的电压误差.采用恒流放电、脉冲放电和动态电应力测试(DST)工况对比分析优化的LPM,P2D模型和SPM的电学性能.结果表明:优化的LPM不仅能够以更少的参数大幅降低模型计算时间,而且能够保证模型电压的计算精度.

A reliable and efficient lithium-ion battery model is the basis of state estimation and fault diagnosis in the battery management system(BMS).The pseudo-two-dimensional(P2D)mechanism model represented by using partial differential equations has many parameters and high accuracy,but its calculation is time-consuming.The model order should be reduced for the on-board BMS.Here in this work,by using the same model parameters,the P2D model and the order-reduced models including the single particle model(SPM)and the lumped particle model(LPM)are built and their voltage accuracies and operation time are compared with each other.Based on the porous electrode model,the concentrated solution theory,and the assumption of uniform current of the battery,the current density is redistributed by the volume ratio of the solid phase to the liquid phase of the electrode.Furthermore,the overpotential and ohmic resistance caused by the lithium-ion concentration distribution in the liquid phase is deduced to offset the battery voltage bias under a large discharge rate.An unconstrained convex optimization method is established to optimize the concentration difference overpotential of the liquid phase of the P2D model battery,the optimized results of which are used to compensate for the LPM voltage.Under the conditions of the constant current discharge(CCD)of 0.1C-4C at the ambient temperature,pulse discharge and dynamic stress test(DST),the electrical performance and the operation time of both the LPM and the SPM are compared to those of the P2D model.Some results are validated and given by the model simulation.Firstly,the accuracy of LPM is over 30%higher than those of the SPM at the CCD rates of 0.1 C,0.5 C and 1 C,and about 30%worse than those of the SPM at the CCD rates of 2 C,3 C,and 4 C.Secondly,the optimized LPM can produce a voltage in good approximation to the voltage of the P2D model with an absolute relative error of the model voltage below 1.5%whether it is caused by the CCD or the DST.Thirdly,the optimized LPM can run efficiently and the needed calculation time cuts down by 85%and 65%for the P2D and the SPM,respectively.For the real-time applications of lithium-ion batteries,the proposed compensation method by adding the overpotential in the liquid phase can make the LPM produce reliable voltage with shorter operation time than either the SPM or the P2D model.