The phase transition of LiNiO2 has been studied by using impedance spectroscopy, DTA, and X-ray diffraction methods. At 720 degrees C the hexagonal phase changes in air to the cubic phase. The phase transition process is rather slow and partially reversible. A peculiar conductivity behavior was observed. From 324 degrees C the conductivity deviates from Arrhenius behavior and is temperature-invariant until 613 degrees C. Subsequently, it decreases rapidly with increase of the temperature. This phenomenon is related to the occupation of Ni2+ in Li+ positions. The optimal sintering temperature for LiNiO2 is suggested to be 700 degrees C.