Examenspresentation av Erik Gingsjö & Poshith Harish

Examinator: Torbjörn Thiringer
Opponent: Rajath Manjunath
Conducted at Volvo group GTT supervised by Niladri Roy Chowdhury

Abstract
In this thesis, the swelling behaviour of a Prismatic Lithium-ion cell is investigated. Initial experiments were done for 0% to 100% state-of-charge for both charge and discharge at various charging-rates from 0.05C to 1.2C. The maximal pressure change showed an increase with charging-rates up to 0.5C for both charge and discharge, with a reverse trend observed at higher charging-rates.
An equivalent circuit with a single resistance was used to model the pressure behaviour at charge, where the resistance can be understood as the resistance of the cell casing to expand. The resistances were shown to exhibit a clear trend for charging rate as well as state-of-charge, with their values becoming bigger with both increasing charging rate and state-of-charge up to 0.5C. The model was tested for 0.3C with the absolute error decreasing rapidly to around 1% after 5% to 100% state-of-charge. Lastly, data from other papers with similar pressure change experiments were used to validate the model. One with experiments at comparable charging-rates as used in this thesis and another at charging-rates above 1C. For the former, the resulting resistance values showed similar trends as our data. For the latter however, the resistance values instead decreased with both state-of-charge and increasing charging-rate, assumed to be due to lithium plating at higher state-of-charge at the higher charging-rates as well as due to thermal effects.

Welcome!
Erik, Poshith and Torbjörn