The Study Of Distrotion Of Polymer Lithium Ion Battery

The charge and discharge processes of lithium ion battery include insertion andextraction of lithium ion in graphite cathode materials. The lattice parameters ofgraphite crystal will change and cause the thickness variation of negativeelectrode.the stress force come from negative electrode swelling will make the celldistorted. When the cell distorted, the thickness of the cell will increase and theperformance of cycle test will become poor.The purpose of this article isto study the thickness of negative electrodeswelling，the separator characteristic and hot shrink, the gap between positiveelectrode and negative electrode in different stage, and the distortion effect on cellperformance.Making a pattern design in positive electrode surface and making a small islandmethod can be used to increase the gap between the positive electrode and negativeelectrode in bare cell and create a space for negative electrode swelling.It candiminish the cell distortion.We studied a clamp baking method to improve cell distortion. when the cell is100%SOC(full charging), after the clamp baking, we find the distortion disappeareafter cycle testing,we do DOE to optimize the clamp baking contiditons.The separator will be shrinkat eveluated temperature. Heat treatment makes theseparator shrink before the winding, so that it can reduce the separator shrinkinginside the cell anddiminish the cell distortion.To optimize the auto-winding machine tension condition and winding speed andtominimize the wave of separator tension in winding process is important and ofapplication value.