The thermal management system of a Lithium-ion battery consisting of phase-change material (PCM) is considered in this study. The batteries are covered by a large volume of PCM. A 18650 battery is used in this numerical investigation as a case study and all achievements are implemented on it. The battery thermal management system (BTMS) parameters during discharge-rest-charge-rest cycles are concerned to understand PCM behavior and battery resilience in the long run. The battery is placed adjacent to various PCMs and is charged and discharged at different rates. Results show that the paraffin wax has the worst performance, and hydrate salt and capric acid have the best performance. Furthermore, the use of polyethylene glycol as PCM improves the performance of the BTMS. Meanwhile, the composite of nano-graphite and PCM would increase a reasonable effect on the BTMS functionality.