As an advanced battery thermal management method, phase change material (PCM) cooling technology is highly desirable but remains significant challenges, considering the instability of the PCM module, including PCM leakage, volume changes and inhomogeneity of the whole module during the repeated melting/solidifying processes. Herein, we develop a kind of nanosilica (NS)-enhanced composite PCM (CPCM-NS) with outstanding anti-leakage and anti-volume-change performances for power battery thermal management. The NS presents numerous nanoscale pores ranging from 30 to 100 nm, which can adsorb liquid phase paraffin (PA) intensively, thus preventing the migration and leakage of liquid PA, increasing the homogeneity and reliving the volume change phenomenon of the module to a great extent. As a result, these enhanced properties of CPCM-NS endow the obtained battery module with much better cooling efficiency and durability. For instance, the maximum temperatures of CPCM-NS with 5.5 wt% of NS are 1.6, 2.4, 4.5, 5.3 and 5.9 degrees C lower than those of CPCM without NS at the 1st, 2nd, 4th, 6th and 8th cycle charge/discharge cycle, respectively, and this temperature difference remains stable at 6.22 +/- 0.05 degrees C during the subsequent cycles.