Pengaruh variasi Temperatur Sintering Pada Sintesis LiNi0.6Mn0.2Co0.2O2 (NMC 622) Terhadap Performa Elektrokimia Sebagai Katoda Baterai Ion Lithium = The Effect of Sintering Temperature Variation on LiNi0.6Mn0.2Co0.2O2 (NMC 622) Synthesis on Electrochemical Performance as a Cathode of Lithium Ion Battery