A passive thermal management system for a lithium-ion battery by employing phase change material as the heat transfer source to manage lithium-ion battery temperature increase was developed. Lithium-ion battery temperature rise is caused by electrochemical reactions. If the lithium-ion battery temperature is not properly controlled, then it will cause a shortening of its lifespan, faster capacity reduction, or even in severe cases, might cause lithium-ion battery explosion. For commercial big-energy applications, a proper lithium-ion battery thermal management allows us to overcome problems related to heat production and improves significantly the performance of the lithium-ion battery. In this investigation behavior of a phase change material was analyzed. The phase change material was used as a medium for the thermal management of a lithium-ion battery cell. A three dimensional numerical model for the lithium-ion battery thermal management system according to phase change material was accomplished by using Ansys Fluent.