锂离子电池加速循环测试研究_韩江浩.pdf

第 12 卷 第 1 期2023 年 1 月Vol.12 No.1Jan.2023储能科学与技术Energy Storage Science and Technology锂离子电池加速循环测试研究韩江浩，王晓丹，李奇松，李慧芳，王睿，许刚（天津力神电池股份有限公司，天津 300384）摘要：以圆型21700 4.8 Ah电池为测试样本，采用零和脉冲法进行加速循环测试研究。以所筛选的10%SOC作为最优的荷电态测试区间，对3种不同正负极材料组成的实验电池进行7天的加速循环测试，以基准电池参数为对比，综合多种参数对电池循环性能优劣进行分析评价。通过对电池加速循环前后的容量保持率分析，即可获得与常规循环测试一致的测评结果：负极二元化电池的放电容量保持率最高，为99.75%，其次是基准方案电池，为99.43%，而正极二元化电池的放电容量保持率最低，为96.33%。此外，通过对电池在加速循环过程中的直流内阻和极化电压增长率的分析，正极二元化电池的增长率远高于其他两种电池。进一步通过对电池瞬时及弛豫阻抗的拆解分析，可知导致正极二元化电池循环较差的原因主要是其正极及负极上均发生了大量的副反应，由于界面膜增厚及沉积物增多导致固相扩散阻抗增大，因此弛豫阻抗增长率达40%。通过对循环后电池进行EIS测试及正负极的物性分析发现，正极二元化电池的扩散阻抗显著较高，且其正极二次颗粒碎裂程度较高，此结果可初步解释正极二元化电池在加速循环中因正极碎裂引发副反应导致固相扩散阻抗增长率较高的现象。该加速循环测试方法以实际循环制式为依据，不引入额外的温度及倍率等应力影响因素，通过对各种测试参数的综合分析，达到定性判断实验电池循环性能优劣的目的，不仅可以大大缩短电池循环测评周期，同时可以为电池循环衰减原因分析提供依据。关键词：锂离子电池；零和脉冲；加速循环；弛豫阻抗；直流内阻；极化电压doi：10.19799/ki.2095-4239.2022.0448 中图分类号：TM 911 文献标志码：A 文章编号：2095-4239（2023）01-255-08Research on accelerated cycle test of lithium-ion batteriesHAN Jianghao,WANG Xiaodan,LI Qisong,LI Huifang,WANG Rui,XU Gang(Tianjin Lishen Battery Joint-Stock Co.,Ltd.,Tianjin 300384,China)Abstract:The zero-sum pulse method was used to perform the accelerated cycle tests on the cylindrical 21700 battery with a nominal capacity of 4.8 Ah.The experimental batteries,composed of three positive and negative materials,were evaluated in an accelerated cycle for 7 days,with 10%SOC chosen as the best test interval.In comparison with the test findings of the reference battery,the cycle performance of the battery was investigated and evaluated by incorporating different characteristics.The assessment result was similar with the traditional cycle test when the capacity retention rate of the battery was compared before and after the accelerated cycle.The negative binary battery had the greatest discharge capacity retention rate of 99.75%,followed by the reference battery with 99.43%,while the positive binary battery had the lowest discharge capacity retention rate of 96.33%.Additionally,according to the examination of the DC internal resistance and polarization voltage growth rate of the battery during the accelerated cycle,the growth rate of the positive binary battery was significantly larger than that of the other two types of 储能测试与评价收稿日期：2022-08-10；修改稿日期：2022-08-19。第一作者：韩江浩（1995），男，本科，助理工程师，研究方向为锂离子电池分析技术，E-mail：；通讯作者：李慧芳，高级工程师（正高级），研究方向为锂离子电池及材料分析技术，E-mail：。2023 年第 12 卷储能科学与技术batteries.Further examination of the batterys instantaneous and relaxation impedance revealed that a considerable number of side reactions had happened on both the positive and negative electrodes,which was the main reason for the positive binary batterys poor cycle.The solid phase diffusion impedance increased due to the interface films thickening and the growth of the deposits.Consequently,the relaxation impedance growth rate reached 40%.Through the EIS test and physical property analysis of the positive and negative electrodes of the battery after cycling,it was revealed that the diffusion impedance of the positive binary battery was noticeably higher,and the cracking degree of the secondary particles of the positive electrode was higher.This finding offers a basic explanation for the phenomenon whereby the positive electrode cracking side reaction causes the positive binary batterys solid diffusion impedance to increase quickly during accelerated cycling.The accelerated cycle test method is based on the real cycle operating parameters without adding extraneous variables like temperature and rate.Through comprehensive analysis of numerous test parameters,the objective of qualitatively evaluating the cycle performance of experimental batteries can be accomplished,which can not only considerably minimize the cycle test length but also offer reference data for the investigation of battery cycle failure.Keywords:Li-ion batteries;zero-sum pulse;accelerated cycle;relaxation impedance;DC internal resistance;polarization voltage在锂离子电池体系及产品开发过程中，作为电池关键性能指标的循环寿命测试耗时非常长，消费类电池可能需要四个月左右，动力电池则可能需要8个月以上，且如果电池设计发生了变化，就需要进行重复测试，漫长的评测过程大大拖延了整个体系及产品开发进度。同时由于评测周期长造成的测试资源投入高及能耗大的问题，间接性导致体系及产品开发成本增大。加速寿命试验是在不改变失效机理的基础上，通过寻找电池寿命与加速应力条件之间的对应关系1-3，利用高加速应力条件水平下的寿命特征去外推评估正常应力水平条件下的寿命特征的试验方法，可以缩短试验周期，提高效率，降低耗损。研究3-5表明，环境温度对电池循环性能的影响最大，因此温度可作为有效的加速因子，通过提升温度加快电池容量衰减进行循环性能的加速评价。但必须注意的是，当温度过高时会导致电池正常老化机理改变，从而导致加速测试失效。Guan 等6针对 1.15 Ah 的 LiCoO2/MCMB 方型电池，研究了不同温度(25、35 和45)对循环性能的影响，结果表明，随温度升高，电池循环衰减加剧，尤其是当温度达到45 时，电池容量快速下降，主要是由于较高的温度加速了正极表面膜的形成，导致正极容量衰减，进而导致全电池的容量衰减加速。吴正国等7为了探寻加速老化合适的温度应力区间，以2.85 Ah的NCA/graphite圆型18650电池为研究对象，设计了3个温度区间进行循环实验。结果表明：在3080 范围内，电池老化速率随温度的升高先降低、再升高。在常温(3056)区域，电池老化速率随温度升高而降低，电池存在析锂现象；在高温(6880)区域，电池电极出现活性物质脱落现象，导致锂离子电池容量的衰减；而在中高温(5668)区域，通过活化能计算判断电池老化机理为固体电解质界面膜的生长。丁鹏飞等8对三元锂电池的研究表明，相比于单一温度加速因子，采用温度-放电倍率耦合的加速循环方式，能够有效缩短电池寿命测试时间。Gao等9通过对LiCoO2/graphite圆型18650电池的循环寿命试验，揭示了不同充电倍率和截止电压对电池衰减机理的影响。结果表明，充电电流和截止电压均存在临界值，一旦超过临界值，就会引发电池衰减机理的改变。卢立丽等10针对LiFePO4动力电池，设计了以充电倍率、放电倍率、环境测试温度以及多因素耦合为测试条件的加速循环实验，结果表明，充、放电256第 1 期韩江浩等：锂离子电池加速循环测试研究倍率加速寿命能力随着电池温度的升高而提高。综上所述，不同的电池体系，不同的加速因子及其应力范围，都会对锂离子电池的衰减机理产生不同的影