摘要：

Along with the popularization of the lithium-ion battery (LIB), much more attention is attracted to its problem of thermal runaway. This paper proposes a simple but novel method to investigate the gas generation throughout the process of thermal runaway. The novelty from the previous study lies in that the battery cells without the cap are used as the test samples. The naked battery offers a key to decouple the pressure caused by the vapor of electrolyte and that of the gases generated in the chemical reaction. This study makes up the knowledge gap of measuring internal pressure before the venting behavior and provides a more accurate method to describe the gas generation of thermal runaway. Three 100% state of charge LIBs with the cathode of LiNi0·8Co0·1Mn0·1O2 are used as tested samples to illustrate the application of this method. Two important results are withdrawn from the samples’ test: (I) the relationship between temperature increasing rate and gas generation rate is not linear until battery temperature approaches the uncontrollable temperature; (II) the partial pressure of gas generated due to the redox reactions bears the major responsibility for the safety valve opening.