基于大倍率电流脉冲的动力锂离子电池阻抗模型优化

随着中国能源转型的推进,动力电池使用量逐年上升。随之而来的电池安全运行问题逐渐凸显。在保障电池稳定运行的电池管理系统(Battery management system,BMS)中,等效电路模型(Equivalent circuit model,ECM)是其工作的基础核心。而目前的电池管理系统模型主要为线性模型,且受限于计算量和芯片的计算能力,无法合理表达电池在极端工况下,如大功率等情况下的非线性特征。针对这一问题,本文从可用功率角度出发,对电池进行了不同倍率的脉冲放电实验,分析了不同倍率情况下电池内阻的非线性特征,改进了电池的等效电路模型,建立了高倍率条件下阻抗随电流的变化关系。实验结果表明改进后的等效电路模型的模型误差为1.74%,远小于旧模型的8%。研究成果比传统等效电路模型相比提高了精度,且计算量比P2D(Pseudotwo-dimensions,P2D)模型小,预期可以用于BMS中电池模型可用功率的在线仿真计算,避免动力电池过功率放电,提高电动自行车使用安全性。

基于功率变换器的电池阻抗在线测量

随着可再生能源的发展,储能系统正扮演着越来越重要的角色,作为一个由海量电池单体组成的庞大系统,锂离子电池系统的运行十分复杂。电池阻抗作为电池的重要参数之一,可以为电池管理系统提供关于电池状态的有用信息,帮助电池管理系统对锂离子电池性能进行监测和评估,电池阻抗参数与电池状态之间的对应关系提供了基于数据驱动,利用电化学阻抗谱进行电池管理的新思路。采用对升压电路施加占空比扰动的方法进行电池阻抗的在线测量,通过理论推导、仿真验证分析了该方法的可行性和合理性,最终基于搭建的电池阻抗在线测量系统,通过对待测信号进行采集与处理,得到了基于实验平台的电池阻抗在线测量结果。

HEV氢镍动力电池动态阻抗特性及其影响因素

氢镍动力电池作为混合动力汽车的主要动力源得到广泛应用,研究氢镍电池的动态阻抗特性及其影响因素为分析电池使用时的内部损耗及合理估算电池健康状态提供依据,并为研究混合动力汽车的电磁兼容问题打下基础。以混合动力汽车车载氢镍动力电池为例对电池的阻抗特性及其影响因素进行分段频域分析。分析了电池老化、电池充放电电流、荷电状态、电池内部溶液的扩散效应、电池电极极化效应、高频时电极集肤效应等因素对电池阻抗特性的影响方式及主要作用频率。在此基础上,建立了电池不同因素作用下的等效电路模型并进行了仿真验证。分析了动力电池作为EMI传播路径的干扰响应。

基于信号分解的电池交流阻抗测量方法

IEC-61960:2003规定电池交流阻抗测量方法是通过测量电池两端对1kHz±0.1kHz交流电流的响应电压来计算电池阻抗。相对传统采用正弦电流信号注入电池测量电池阻抗的方法,本文提出了一种注入开关脉冲激励电流的新方法测量电池阻抗。根据傅里叶变换原理,通过低通滤波分解出脉冲激励电流信号和脉冲响应电压信号的1kHz基波成分,从而计算出电池的交流阻抗。该方法电路实现简单,尤其适用于多点测量的电池自动化测试设备中。

基于在线阻抗测试技术的蓄电池维护与管理

阀控铅酸蓄电池的维护与故障预防,消耗了运维人员大量精力与费用。本文分析现行电池监测和维护方法存在的问题;分析了基于蓄电池阻抗测试的在线监测系统的有效性、经济性和不足,并结合相关的测试数据探讨利用蓄电池在线阻抗测试技术评价蓄电池容量的标准。对于该技术的经济性做了相关的评估。

纯电动汽车充电机输出阻抗特性

纯电动汽车充电机与汽车动力电池构成级联式供电系统。充电机的输出阻抗是随频率变化的函数,动力电池也在不同频率下表现出不同的阻抗特性。为了在充电过程中充电机与动力电池组成的系统能够稳定工作,必须保证充电机输出阻抗与电池输入阻抗的比值满足奈奎斯特稳定性判据。以纯电动汽车充电机的输出阻抗为研究对象,建立充电机动态线性小信号模型,通过仿真分析输出阻抗特性随直流工作点,输出滤波器等效串联电阻,控制环路特性的变化规律,并用实验证明了理论分析的正确性,为充电机输出输出阻抗的设计提供了依据。

适应高电流倍率工况的锂离子电池等效电路模型

等效电路模型(equivalent circuit model,ECM)是电池模型的主要类型之一,对电池特性分析和状态估计非常重要。然而,当前广泛使用的基于阻容(RC)结构的电池ECM无法应对复杂多变场景。例如,传统ECM无法反映电池极化电压在高电流倍率下的特殊现象,即传统ECM不能准确表征电池在高电流倍率下的阻抗特性。针对这一问题,本团队在不同SOC下进行了电池峰值电流实验,通过实验数据分析了电池在峰值电流下的极化电压和阻抗特性。然后,引入负电阻电容环节拟合实验结果,对传统ECM进行改进以充分体现高电流倍率下的电池极化现象。通过比较传统RC环节与负电阻电容环节特性,提出了基于阻抗特性曲线拐点的参数分离方法,其计算量小,模型求解便捷。最后,对分离参数后的模型进行验证,结果表明所提ECM及参数获取方法能够较好地模拟高电流倍率下电池的极化电压变化,进而更加准确地表征电池电压特性,模型输出与实验结果误差小于0.05 V。所提ECM相比于传统的RC模型精确度得到了极大提升,且不依赖于复杂的电化学模型,维持了模型的简单结构。

Freeze/Thaw循环下CCM电化学性能研究

采用循环伏安法(CV)、电化学阻抗谱测试(EIS)、单电池交流阻抗测试(AC impedance)3种电化学性能表征和研究方法,研究了质子交换膜燃料电池在Freeze/Thaw(F/T)循环下的电化学性能变化,对比研究了单电池热除水和不除水处理对CCM(catalyst coated membrane)电化学性能的影响,分析了F/T循环后电池在高、低电流密度下性能衰减的潜在原因。研究表明,多次F/T循环后CCM的电化学活性表面积减少;单电池除水预处理方式不同,CCM的电化学活性表面积减少程度不同,热除水少于不除水;电化学活性面积减少对电池在低电流密度下的性能影响较大,而CCM/扩散层接触电阻则对电池在高电流密度下的影响较大。

Ionic Conduction and Fuel Cell Performance of Ba0.98Ce0.8Tm0.2O3-α Ceramic

The perovskite-type oxide solid solution Ba0.98Ce0.8Tm0.2O3-α was prepared by high temperature solid-state reaction and its single phase character was confirmed by X-ray diffraction. The conduction property of the sample was investigated by alternating current impedance spectroscopy and gas concentration cell methods under different gases atmospheres in the temperature range of 500-900 ℃. The performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured. In wet hydrogen, the sample is a pure protonic conductor with the protonic transport number of 1 in the range of 500-600 ℃, a mixed conductor of proton and electron with the protonic transport number of 0.945-0.933 above 600 ℃. In wet air, the sample is a mixed conductor of proton, oxide ion, and electronic hole. The protonic transport numbers are 0.010-0.021, and the oxide ionic transport numbers are 0.471-0.382. In hydrogen-air fuel cell, the sample is a mixed conductor of proton, oxide ion and electron, the ionic transport numbers are 0.942 0.885. The fuel cell using Ba0.98Ce0.8Tm0.2O3-α as solid electrolyte can work stably. At 900 ℃, the maximum power output density is 110,2 mW/cm2, which is higher than that of our previous cell using Ba0.98Ce0.8Tm0.2O3-α （x〈≤1, RE=Y, Eu, Ho） as solid electrolyte.

2017 EMC Europe国际学术研讨会——提名文章(二)

由于电动汽车和混合动力汽车动力总成的电气化，对车辆的电磁兼容性（EMC）产生了巨大的挑战。所用的电力电子部件产生的宽带干扰可能会影响车辆内12V系统的部件。为了应对这些挑战，牵引系统要完全的屏蔽且与车身隔离。对于车辆部件，CISPR25的现行版本增加了一个附录，该附录包括了动力总成部件、新的测量布置和修订后的限值，标准中给出的几乎所有的布置，需要使用直流电源给位于屏蔽室内的受试装置（DUT）供电。由于实际牵引电池容量有限，试验时不得不使用电网供电。本文研制了一种模拟电动车辆牵引电池的无源阻抗网络。首先测量了360V混合电池包的阻抗。基于这些测量，给出了表示电池阻抗及其特征值和谐振点的等效电路。使用此等效电路，设计无源阻抗网络用于高压牵引系统部件的EMI试验。最后，使用电动车辆牵引系统环路布置中集成在硬件中的牵引系统部件验证了此无源网络。

Effects of sodium substitution on properties of LiMn_2O_4 cathode for lithium ion batteries

Na-doped Li1.05Mn2O4 cathodes were synthesized using a sol-gel process.The samples were characterized by X-ray diffractometry(XRD),cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and charge-discharge measurements. The results show that all the samples exhibit the same cubic spinel phase structure without impurity.The lattice constant and unit cell volume decrease with increasing the sodium dopant amount.As the molar ratio of sodium to manganese(x=n(Na)/n(Mn))increases from 0 to 0.03,the initial discharge capacity of the Li1.05Mn2O4 cathodes decreases from 119.2 to 107.9 mA·h/g,and the discharge capability at large current rate and the storage performance decline dramatically,while cycling performance at room temperature and 55℃are improved.The CV and EIS studies indicate that reversibility of Li1.05Mn2O4 cathodes decreases and the electrochemical impedance increases with increasing the sodium dopant amount.

H_2O/CO_2 co-electrolysis in solid oxide electrolysis cells

A solid oxide electrolysis cell(SOEC) is an environmental-friendly device which can convert electric energy into chemical energy with high efficiency. In this paper,the progress on structure and operational principle of an SOEC for co-electrolyzing H2O and CO2to generate syngas was reviewed. The recent development of high temperature H2O/CO2co-electrolysis from solid oxide single electrolysis cell was introduced. Also investigated was H2O/CO2co-electrolysis research using hydrogen electrode-supported nickel(Ni)-yttria-stabilized zirconia(YSZ)/YSZ/Sr-doped LaMnO3(LSM)-YSZ cells in our group. With 50 % H2O,15.6 % H2and 34.4 % CO2inlet gas to Ni- YSZ electrode,polarization curves(I- U curves) and electrochemical impedance spectra(EIS) were measured at 800 ℃ and 900 ℃. Long-term durability of electrolysis was carried out with the same inlet gas at 900 ℃ and 0.2 A/cm2. In addition,the improvement of structure and development of novel materials for increasing the electrolysis efficiency of SOECs were put forward as well.

Uniform AlF_3 thin layer to improve rate capability of LiNi_(1/3)Co_(1/3) Mn_(1/3)O_2 material for Li-ion batteries

LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.

基于电化学阻抗谱的磷酸铁锂动力电池电路模型研究

基于电化学阻抗谱特性,对Randles等效电路模型引入复参数电感元件、复参数电容元件和常相位元件,建立磷酸铁锂电池的等效电路修正模型,通过对实测阻抗谱的拟合以及模拟退火算法,辨识修正模型中的参数。拟合结果表明,修正模型相比Randles等效电路模型精度提高近4%,能够更好地模拟电池伏安动态特性,为电池模型在电池管理系统上的进一步应用提供理论基础。

Mixed Conduction in BaCe0.8Pr0.2O3-α Ceramic

BaCe0.8Pr0.2O3-α ceramic was synthesized by high temperature solid-state reaction. The structural characteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3-α were measured, and the electrical conduction behavior of the material was investigated in different gases in the temperature range of 500-900℃. The results indicate that the material was of a single perovskite-type orthorhombic phase. From 500℃ to 900 ℃, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere （oxygen, air or nitrogen）

Synthesis and electrochemical performance of Li_3V_2(PO_4)_3 by optimized sol-gel synthesis routine

Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li3Va（PO4）3 as cathode materials for lithium-ion batteries and morphology of Li3V2（PO4）3 were characterized by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li3V2（PO4）3 with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li3V2（PO4）3 are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li3V2（PO4）3 synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.

Effect of Additives on the Performance of Lead Acid Batteries

Effect of titanium dioxide （TiO2） and carbon additives in the respective positive and negative material properties and the influence on the performance of the battery were investigated. The electrode samples were characterized by BET （Brunauer Emmett Teller）, XRD （X-ray diffractometer）, SEM （scanning electron microscopy） and EIS （electrochemical impedance spectroscopy） to understand the surface area, phase, structure, morphology and electrical conductivity of the respective electrode material. The surface area was obtained as 2.312 m2＂g＂l and 0.892 m2＂g＂1, respectively for 12% of activated carbon in the expander of negative and 0.70% of TiO2 （Titanium dioxide） in the PAM （positive active material）. The structural analysis reveals an increase in the tetrabasic lead sulfate and also evidenced by well grown crystals in the PAM with the TiO2, respectively obtained by XRD and SEM techniques. The impedance spectra analysis shows an increase of electrical conductivity of negative active mass with temperature. The battery results showing two fold enhancements in the charge acceptance were attributed to the high surface area activated carbon in the NAM （negative active material）. The materials properties of electrodes and their influence on the battery performance were discussed.

Electrochemical impedance spectra of CdSe quantume dots sensitized nanocrystalline TiO_2 solar cells

Quantum dots sensitized nanocrystalline Tit2 solar cells （QDSSCs） are promising third-generation pbotovoltalc devices. In comparison with conventional dye-sensitized solar cells （DSSCs）, the efficiency of QDSSCs is still very low （about 3%）. In this paper, the electrochemical impedance spectroscopy technology has been adopted to investigate the quasi-Fermi level and the cartier dynamics of the colloidal CdSe QDs sensitized Tit2 eletrode with S2-/Sf redox electrolytes and the series resistance of the QDSSCs. In comparison with the conventional DSSCs with I^-3/Г as redox electrolytes, the energy difference between the conduction band edge and the quasi-Fermi levels of the Tit2 films （or the Fermi levels of the redox electrolytes） in QDSSCs has been decreased by about 0.3 V, resulting in the decrease of Voc by this value. The increases of the electrolyte dif- fussion resistance and the charge transfer resistance between Pt counter electrodes and S2-/Sx redox electrolytes were attributed to the decrease of the fill factors. However, the electron lifetime and electron diffussion length for QDSSCs are longer than those for DSSCs due to the retardation of the electron recombination by the adsorbed cysteine at the surfaces of the TiO2 films. It is indicated that electron recombination at the TiO2/electrolyte interface is not the main reason for the lower Jsc of the colloidal QDs sensitized QDSSCs. Improving light harvesting efficiency and photoelectron injection efficiency should be considered in the future for such kind of QDSSCs.

Universal lithiophilic interfacial layers towards dendrite-free lithium anodes for solid-state lithium-metal batteries

Solid-state lithium-metal-batteries(SSLMBs)using garnet Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)as the solid electrolyte are expected to conquer the safety concerns of high energy Li batteries with organic liquid electrolytes owing to its nonflammable nature and good mechanical strength.However,the poor interfacial contact between the Li anode and LLZTO greatly restrains the practical applications of the electrolyte,because large polarization,dendritic Li formation and penetration can occur at the interfaces.Here,an effective method is proposed to improve the wettability of the LLZTO toward lithium and reduce the interfacial resistance by engineering universal lithiophilic interfacial layers.Thanks to the in-situ formed lithiophilic and ionic conductive Co/Li_(2)O interlayers,the symmetric Li/CoO-LLZTO/Li batteries present much smaller overpotential,ultra-low areal specific resistance(ASR,12.3 X cm^(2)),high critical current density(CCD,1.1 mA cm^(-2)),and outstanding cycling performance(1696 h at a current density of 0.3 mA cm^(-2))at 25℃.Besides,the solid-state Li/CoO-LLZTO/LFP cells deliver an excellent electrochemical performance with a high coulombic efficiency of~100%and a long cycling time over 185 times.Surprisingly,the high-voltage(4.6 V)solid state Li/CoO-LLZTO/Li_(1.4)Mn_(0.6)Ni_(0.2)Co_(0.2)O_(2.4)(LMNC622)batteries can also realize an ultra-high specific capacity(232.5 mAh g-1)under 0.1 C at 25℃.This work paves an effective way for practical applications of the dendrite-free SSLMBs.

Synergetic effects of blended materials for Lithium-ion batteries

LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2, LiMn_2O_4 and LiCoO_2 are paired to make the blended materials for the cathode of lithium-ion batteries. The factors impacting on the characteristics of blended materials are studied using constant current charge/discharge measurement and electrochemical impedance spectroscopy. The results show that the three pairs of blended materials exhibit very different synergetic effects in high C-rate discharging. The mechanism of particle synergetic effect has a physical root on the compensating material property of blending components, which fundamentally correlates with their similarity and difference in crystalline and electronic structures. The AC impedance show the obvious changes that alternate the high C-rate performance, due to reduced particle impedance in blended materials. The pairs of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2-LiMn_2O and LiCoO_2-LiMn_2O_4 present obvious increases in high C-rate reversible capacities than does the pair LiCoO_2-LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2.