On the testing methods of simulating a cell internal short circuit for lithium ion batteries

It is well known that overcharging of cylindrical and prismatic lithium ion batteries used in portable electronic equipment can cause catastrophic failure of battery cells. However, investigations into the root cause of some battery failures have conclusively ruled out overcharging or other external cell stimuli, leaving an internal cell fault as the only remaining possible cause of failure. The lithium ion battery industry has employed a nail test to simulate internal short circuit events for studying cell responses to internal failures. This paper addresses the shortcomings of the nail test method and proposes a modified crush test method that will more closely simulate massive internal cell short circuit failures and allow better assessment of the cell response in the event of such failures. This test may also provide further insight into the appropriate level of charge to select for cells to be shipped. Test results for cell tests at different charge levels using this method are also presented.