Battery Characterisation and Modelling for improved battery management
This work package addresses the fundamental issues of the battery electrochemical processes, from chemical, electrical, mechanical and thermal perspectives and comprises of the following four sub tasks:
Task 1.1 – Battery state of charge and health prediction
Technical challenge – In any V2G scenario there is likely to be a situation in which batteries of widely varying SoC and SoH are likely to be connected to electrical grids. Voltage monitoring or Coulomb‐counting may give unreliable information about SoC and SoH and as batteries age their impedance changes (both internal resistance and interfacial capacitance effects at electrodes). Determination of the impedance spectrum over a wide range of frequency and fitting the data to a standard equivalent circuit would provide all of the information necessary information but is impractical. In order for V2G to work effectively batteries need to communicate this information to the grid and it is important to understand whether V2G applications may artificially age batteries.
Task 1.2 – Battery thermal analysis and management
Technical Challenge ‐ A Li‐ion cell generates heat during both charge and discharge and can lead to overheating under stressful conditions such as rapid charge/discharge in high ambient temperatures. If the cells are not thermally managed, a thermal runaway process can propagate potentially leading to catastrophic cell/vehicle damage. Therefore, accurate prediction of the thermal behaviour of the battery cell (and crucially the battery pack) is essential for coordinated V2G operation.
Task 1.3 ‐ Characterisation & Modelling of Chemical Processes
Technical Challenge – The aging behaviour of Li‐ion cells and batteries remains an area of major scientific study, and this task aims to investigate these degradation effects from their fundamental processes on the electrodes, separators, electrolyte and battery behaviour (e.g. intercalation, separator electrolyte interface etc), including mechanical, electrical, chemical and thermal influences and their influence on battery characteristics. Through the study of battery materials, separators, irreversible reaction mechanisms, the variation and characteristics of battery performance will be revealed thus establishing the relationship between the battery characteristics and its internal parameters. Some of the significant issues to be studied are: positive electrode dissolution; negative electrode surface SEI films; mechanism of battery gassing (even during storage/standby); formation and prevention of Lithium dendrite.
Task 1.4 ‐ Battery Testing
Technical Challenge – The concept of employing V2G relies on aggregation of many EV battery packs at widely varying SoC and SoH at any instant, hence the modelling and testing of such as system MUST consider both cell and module/pack effects.These tests, typically monitored charge/discharge tests under controlled thermal and mechanical conditions, must also include post‐mortem tests on any failed, or failing, cells/packs, in order to inform the base research and modelling activities.