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组成部分，电气化，特别是在乘用汽车中，是更可持续的交通解决方案的关键。目前，大多数电池测试使用非常“干净”的DC测试电流来执行，而在真实的世界情况下，存在由功率逆变器的切换以及电机特性引入的大量噪声。这些交流分量具有不同的频率，从长远来看，了解它们如何影响电池的性能至关重要，目前的文献对此提出了不同的意见。为了研究锂离子电池对涟漪电流的反应，该项目旨在进行实验，将各种类型的涟漪应用于各种锂离子电池，并使用电化学建模来为实验设计提供决策信息。此外，如果这种建模提供了与实验最终发现的结果不同的结果，它将有助于突出该模型的局限性，并有助于未来改进该模型的工作。然后将进行实验阶段，改变所选变量（例如波形、频率、细胞化学、细胞格式等）。同时在执行循环后表征之前同时记录所选择的指示符（例如，EIS、容量/功率衰减）。预计该表征将包括各种扫描和解剖，以便确定具体的降解类型。这将有助于该项目的最终目标，即在电化学理论中寻求对实验结果的解释。这是至关重要的，因为涟漪电流可能会增强或强调特定类型的退化，因此意味着消除这种退化的方法，并且对锂离子电池工作的任何进一步理解都是对文献的有价值的补充。这项工作不仅将增加锂离子电池的知识库，而且该项目还将寻求利用发现的结果，为电池管理系统的设计提供最佳实践，例如去除电源滤波器或修改开关频率。因此，这项工作不仅有可能通过减少退化来提高电池寿命，而且还可能影响电力电子子系统的设计方式。电池管理系统性能的这种潜在简化或改进表明与AVL和UKRI的相关性是显著的。

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.