A pyrometallurgical process of metal recycling from waste lithium-ion batteries (LIB) has been developed. Basic process is that Co, Ni oxides which are from cathode materials of LIB and Cu which is from anode current collector are smelted and are reduced to metal, and the metal is refined in a next hydrometallurgical process. Since Al and Li contained in LIB are distributed to slag as oxides in the melting process, it is important to know the influence of these elements on the melting temperature of slag in determining the operating conditions. Therefore, the effects on the slag melting temperature when these elements and the amount of flux are changed are investigated and compared with the calculation results in FactSage (thermodynamic calculation software). In addition, based on the obtained melting temperature, waste LIB and flux were mixed and melted, and it was confirmed whether the metal and slag could be separated.