In this article, a novel composite phase change materials based thermal management system coupled with air cooling was proposed in order to sustain the temperature rise and distribution within desirable ranges of the lithium-ion battery utilized in a hybrid power train. A combined experimental and numerical study was conducted to investigate the effects of air flow rate and phase change material liquid fraction on the thermal behavior of the integrated thermal management system. Comparisons between the integrated system and an air cooling system were implemented under different air flow rates and ambient temperatures. Furthermore, thermal characteristics of both systems during charge-discharge cycles were numerically simulated. The results showed that the cooling effect of the integrated system was obviously better than that of the air cooling system. The variation of the air flow rate and ambient temperature had negligible impact on the heat dissipation of the phase change cooling. After the fully melt of phase change material, the battery temperature did not rise rapidly due to the auxiliary cooling of the cooling air. During 4C charge-discharge cycles, the temperature rise of the battery pack could be effectively restrained by the air cooling at a flow rate exceeding 300 m3/h. While for the integrated system, good thermal management could be achieved with only 100 m3/h of air flow rate. Especially for the operation mode, i.e., phase change material cooling during the discharge and coupled phase change material and air cooling during the charge, the integrated system could control the maximum temperature of the battery pack below 49.2 oC and reach up to six charge-discharge cycles under no additional battery power consumption.