High temperature X-ray diffractive study of spinel-type lithium manganese oxides

Abstract The thermal crystallization of spinel-type LiMn 2 O 4 phases from a stoichiometric mixture of Li 2 CO 3 and various manganese compounds has been investigated by means of a high temperature X-ray diffraction (HT-XRD) technique, and we obtained stoichiometric and oxygen-deficient LiMn 2 O 4 oxides from different manganese compounds evaluated from the discharge capacities at 3.2 V in Li cells. The thermal behaviors of the stoichiometric and oxygen-deficient spinels were investigated in the temperature range between 25 and 700 °C in air by HT-XRD. The cubic spinel-type phase was maintained without any phase transitions, and the unit cell reversibly expanded/contracted. Their linear thermal expansion coefficients were 1.1–1.2 × 10 − 5  K − 1 and were independent of the oxygen deficiency. Furthermore, HT-XRD proved that Li-rich spinel, Li 1.1 Mn 1.9 O 4 , thermally underwent reversible phase separation into Li 2 MnO 3 and spinel Li[Li x Mn 1 − x ]O 4 ( x  600 °C.