Virtual unrolling of spirally-wound lithium-ion cells for correlative degradation studies and predictive fault detection

Abstract

A spirally-wound LG 18650 MJ1 lithium-ion battery was imaged in 3D before and after 1061 cycles using X-ray computed tomography. The battery's capacity had faded to 79% of its initial value and some of that fade was attributed to delamination in the innermost region of the ‘jelly-roll’ structure. A method for virtually unrolling the jelly-roll and analysing it in different coordinates is presented. The method allows efficient comparison of the position and shape of the electrodes at different times and highlights imperfections present in the jelly-roll before cycling which were shown to nucleate the delamination of the electrode.