Disclosed is a lithium secondary battery with high stability and excellent performance, and its manufacturing method. The lithium secondary battery includes a positive electrode including a positive electrode active material, a conductive material and a binding material and a negative electrode including a negative electrode active material and a binding material, and PTC powder is contained in at least one of the positive electrode and the negative electrode. If the battery is overheated due to overcharge, the PTC powder contained in the positive electrode and/or the negative electrode abruptly increases electric resistance to break electric current, thereby preventing further increase of temperature and resultantly preventing fire or explosion. In addition, the conductive material is contained separately from the PTC powder, performance of the battery is not deteriorated in the normal operation.