Abstract: Based on high temperature thermal runaway process of lithium ion battery pack, thermal parameters variation characteristics during the thermal runway were analyzed. Selecting the temperatures of 50 ℃ and 100 ℃, taking paraffin-expanded graphite-activated carbon and PEG1500-methyl cellulose as two levels of phase change materials(PCM), the grading inhibition method to prevent the high temperature thermal runaway of the lithium ion battery was put forward. Curved aluminum honeycomb board was used as the carrier. Under normal temperature and pressure, the effectiveness of phase change materials was tested by external short circuit of three lithium-ion batteries in parallel. The maximum temperature difference is 446 ℃ compared with the batteries without two-stage phase change materials. The validity of the two-stage phase change material is verified.

Key words: lithium-ion battery pack, thermal runaway, phase change materials, grading inhibition