Phase change materials (PCM) cooling has been considered as the most potential alternative to traditional battery thermal management (BTM) technology, but significant challenges remain: PCM leakage, poor mechanical properties and low surface heat transfer capability between PCM and the external environment. Here, we develop a BTM technology based on the ternary composite materials of expanded graphite (EG), paraffin (PA) and low-density polyethylene (LDPE) coupled with low fins. The as-doped LDPE framework can not only enhance the mechanical molding property but also prevent PA leakage to a great extent. Coupling with low fins endows the entire BTM system with high surface heat transfer capability. For instance, the as-prepared LDPE/EG/PA composite PCM shows much better mechanical properties and cooling effect in comparison to EG/PA composite and air cooling, respectively. After coupling with low fins, the as-constructed PCM-based battery module presents excellent heat dissipation performance, keeping the battery pack working under the safety temperature of 50°C and temperature difference of 5°C for lithium-ion power batteries, even at an extremely high discharge rate of 3.5C.