To find and understand the influence DC ripple current has on lithium-ion cells in automotive applications

电池可能是电动汽车最关键的部件，电气化，特别是乘用车的电气化，是更可持续的交通解决方案的关键。目前，大多数电池测试是使用非常“干净”的直流测试电流进行的，而在实际情况下，电源逆变器的切换以及电机特性会引入大量的噪声。这些交流分量具有不同的频率，了解它们如何长期影响电池的性能是至关重要的，目前的文献对此提出了不同的观点。为了描述锂离子电池对波纹电流的反应，该项目旨在进行实验，将各种类型的波纹应用于各种锂离子电池，并使用电化学模型为实验设计提供决策依据。此外，如果该模型提供的结果与最终的实验结果不同，它将有助于突出该模型的局限性，并有助于今后为改进该模型所做的任何工作。然后进行实验阶段，改变所选择的变量(例如，波形、频率、电池化学、电池格式等)。同时在执行循环后表征之前同时记录选定的指标(例如，EIS、容量/功率衰减)。这一特征预计将包括各种扫描和解剖，以便可以确定特定类型的降解。这将有助于该项目的最终目标，即寻求对电化学理论中的实验结果的解释。这一点至关重要，因为波纹电流可能会增强或强调特定类型的降解，因此暗示了消除这种退化的方法，而且对锂离子电池工作原理的任何进一步了解都是对文献的宝贵补充。这项工作不仅将增加锂离子知识库，而且该项目还将寻求利用所发现的结果，为电池管理系统设计的最佳实践提供参考，例如移除电源过滤器或修改开关频率。因此，这项工作不仅有可能通过减少退化来延长电池寿命，而且还可能影响电力电子子系统的设计方式。这种电池管理系统性能的潜在简化或改进表明，与AVL和UKRI的相关性都是显著的。

The battery cell is probably the most critical component of an EV and electrification, especially in passenger cars is key to more sustainable transport solutions. Currently, most battery testing is performed using very "clean" DC test currents whereas in real world situations there is significant amounts of noise introduced by the switching of power inverters as well as motor characteristics. These AC components are of various frequencies, and it is crucial to understand how they affect the performance of the battery in the long run, for which current literature offers differing opinions. To characterise how Li-ion cells react to ripple current, the project aims to conduct experiments applying various types of ripple to various lithium-ion cells with electrochemical modelling used to inform decisions on the design of experiment. Additionally, if this modelling provides different results to those eventually found experimentally, it will serve to highlight the limitations of that model and aid any future work done to improve the model. The experimental stage will then be conducted, varying the chosen variables (e.g. waveform, frequency, cell chemistry, cell format etc.) whilst concurrently recording chosen indicators (e.g. EIS, capacity/power fade) before performing post-cycling characterization. This characterisation is expected to include various scanning and dissection, so as the specific type of degradation can be determined. This will aid in the final objective of the project which will be to seek an explanation for the experimental results in electrochemical theory. This is crucial as the ripple current may enhance or emphasise specific type of degradations and so imply methods to negate this deterioration, and any further understanding of the working of lithium-ion cells is a valuable addition to literature. This work will not only add to the lithium-ion knowledge base, but the project will also look to exploit the results found to inform best practice in the design of battery management systems, such as removal of power filters or modifications of switching frequencies. Hence this work has the potential to not only improve battery lifetime by reducing degradation, but also impact the way power electronic subsystems are designed. This potential simplification or improvement of performance of battery management systems shows the relevance to both AVL and UKRI is significant.