Short-circuit and overcharge behaviour of some lithium ion batteries

We have monitored the electrical and thermal short-circuit and overcharge behaviour of several lithium ion battery cell types by modern X-ray tomography methods both in- and ex-situ. Morphological changes and damages thus can be directly correlated with the observed current, voltage and temperature characteristics. In the case of 26650-type cells, we have observed destruction of the metal containers during both short-circuit and overcharge experiments, however, the safety relief valves stayed intact. The metal container of the 18650-type cell with identical chemical components was not destroyed but the saftey valve had opened. In both cases, all of the corrosive electrolyte was released. The containment of other lithium ion battery types from a number of different manufacturers did not show any destructive changes. When the short-circuit experiments were repeated with short intervals allowing the battery cells to cool down to room temperature, no destruction was observed and the cells stayed mechanically and electrochemically intact. Our findings suggest that no correlations between chemical constitution of the cathode material or electrolyte with occurring damages exist, however, the degree of damage seems to depend strongly from cell design and materials used in the containment. It is therefore necessary and strongly recommended to determine the short-circuit and overcharge behaviour of every single lithium ion battery type in detail prior to its technical application.