基于二阶段放电容量试验的磷酸铁锂动力电池Peukert模型及机理分析

仝猛^*,a,b邵静玥^a,卢兰光^a,黄海燕^a,李哲^a, 邓隆阳^a, 王瑛^a,王斌^a,林庆峰^c,赵伟^b, 高子渝^b,焦生杰^b, 欧阳明高^a

a清华大学汽车工程系b 长安大学工程机械学院/汽车学院 c北京航空航天大学交通科学与工程学院

摘要：传统Peukert方程(PE1)，反映的是放电倍率与可用容量的关系，此可用容量对应于单一阶段恒流放电所能放出的电量，因此存在不能区分电流倍率对于电荷损耗及剩余容量影响的问题。对此，拟采用二阶段恒流放电试验及改型的Peukert方程分离这两种因素。分别建立第一阶段放出的电量（可用电量）、第二阶段放出的电量（剩余容量）、二阶段放出电量之和（最大可用电量）的Peukert形式的方程，分析与Peukert乘幂关系的吻合程度以及Peukert模型背后起主导作用的机理。其中，最大可用容量Peukert模型(PE3)，反映了电流倍率与电荷损耗的关系。剩余容量Peukert形式的模型(PE2)则反映了电流对于浓度梯度和扩散的影响。

试验的磷酸铁锂电池，最大可用容量与倍率在对数域的曲线，存在分叉、非线性现象，反映了可用容量、内阻等内在特性受温度、电流影响而增大或波动的特点。对应到其Peukert系数，变化范围为1.01~1.06，远小于镍镉、铅酸电池，说明了其电量损失较小、大电流对损耗的影响也较小，故Peukert模型比较合适此类电池的电量估计。

关键词：磷酸铁锂电池 颇克特模型 二阶段放电 安时积分法 放电倍率修正 剩余电量 荷电状态

中图分类号：

Experiment and Analysis on the Peukert Equation of Lithium Iron Phosphate Battery Based on Two Stage Discharge Method

Meng Tong^*,a,b, Jingyue Shao ^a,Languang Lu ^a,Haiyan Huang ^a, Zhe Li ^a, Longyang Deng ^a, Ying Wang ^a, Bin Wang ^a, Qingfeng Lin ^c, Wei Zhao ^a, Ziyu gao ^a, Shengjie Jiao ^a, Minggao Ouyang ^a

a. Department of Automotive Engineering, Tsinghua University, Beijing, China; b. Department of Construction Mechanical, Chang An University, Xi’an, China; c. School of Transportation Science & Engineering, BeiHang University

Abstract: Peukert equation reveals the correlation between C-rate and available capacity at the discharge rate, but it confuse two mechanism, charge loss in discharge process and residual capacity at the end of the discharge process. This paper presents a two stage constant current discharge test on a Lithium Iron Phosphate battery and revised Peukert equations to separate the influences of the two mechanisms.

Peukert equation of the first stage available capacity (PE1) is just the original Peukert equation, Peukert equation of the second stage available capacity (residual capacity) (PE2) reveals the relation between C-rate and residual capacity, Peukert equation of maximum available capacity (sum of the two stages) (PE3) reveals the relation between C-rate and charge loss.

PE2 fits data best, which means that diffusion is the dominant effect behind the Peukert equation. PE3 fits data worst, with trends of diverging, raising at large C-rate under the trend of Peukert equation. These phenomenons are in accordance with the current and temperature effects on SEI layers and diffusion, and on available capacity, internal resistance, and potential finally. So the Peukert coefficient of the LFP battery varies between 1.01~1.06. Anyway, the Peukert coefficient is very small compared to Lead-acid and NiMH batteries, disclose its small charge loss and small influence of C-rate on the loss.

Keywords: Lithium iron phosphate battery    Peukert Equation   two stage discharge   Coulombic counting   C-rate  Remaining capacity   State of Charge (SOC)

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