| The soft pack lithium-ion battery is widely used in the mobile electronic devices,especially for smart phone and tablet PC. The main content of this thesis is to studythe gas generation mechanism and impact of this soft pack lithium-ion battery in thefield application and to develop an accelerated testing method and model for theproduct reliability projection to shorten the product development cycle time.The high temperature storage, overcharge and overdischarge conditions all couldcause gas generation in the lithium-ion battery. The gas component was studied bythe GC-MS. The main results are the following:（1） The gas generation under hightemperature storage condition is major caused by the cathode and electrolyteoxidation reaction. The reaction production is CO2and the content is over80%.（2）The gas generation under overcharge condition is major caused by the cathode andelectrolyte oxidation reaction. The reaction product is CO2. The reaction becomesviolent when the overcharge voltage is over4.9V.（3） The gas generation underoverdischarge condition is major caused anode SEI decomposition. The reactionproducts are alkanes and alkenes gas. The reaction becomes violent when theovercharge voltage is under1.0V and CO2generation.The thickness expansion rate of the battery during testing and field application isone of the main reliability indexes. According to the mechanisms study results, that isthe reaction of cathode and electrolyte is the root cause of battery swollen under hightemperature storage. Apply the Kissinger method to estimate the activation energy ofthe DSC measurements and function. And take a different approach by using thestorage swollen time threshold to estimate the activation energy also. Base on abovestudy result to develop a mathematical reliability modeling for the producttemperature swollen projection. This model could be used for the productdevelopment validation and shorten the product development cycle time. |
PDF Full Text Request