Understanding Ageing in Li-ion Cells: an Enabler for Effective Grid Interaction Strategies

Due to the large upfront expenditure of a battery pack, usage lifetime optimisation is an important objective both for battery pack design and control system. In this work we aim to review the physical and chemical ageing mechanisms, the impact on cell performance and the factors that accelerate them. This knowledge is essential both for the battery pack design and the battery management system, and the way in which they can minimise the effects of cell ageing through controlling factors such as temperature, current and Voltage limits in an intelligent approach. This work is also the first step towards the design of an advanced cell ageing model that can be used to inform both the design of battery packs but also the battery management system. This can then be used to assess the ageing impact of usage from both vehicle and energy storage applications, in particular vehicle-to-grid interactions, ‘powerwall’ type applications and large scale energy storage. Our study was confined to Li-ion cell chemistries bounded to ageing under normal cycling conditions. As a result, we did not investigate abuse conditions such as impact and short circuiting.