Improvement of the electrochemical properties of LiNi0.5Mn1.5O4 by controlling the heating atmosphere during synthesis

The heating atmosphere for LiNi0.5Mn1.5O4 (LNMO) powder synthesis was controlled during part of the temperature elevation process to examine its effects. The heating profile was designed with two constant temperature steps, and various atmospheres were introduced during the first (low-temperature) section. The electrochemical performance of LNMO could be controlled by applying an inert or reducing atmosphere during the first heating step. Optimized performance could be obtained by flowing Ar during the first step at 800 degrees C, which showed simultaneous improvement of the rate performance, room- and high-temperature cyclabilities, discharge capacity, and proportion of the high-voltage discharge relative to conventional synthesis in an oxidizing condition. The underlying mechanism was investigated by a first-principles simulation, which indicated that an inert or reducing atmosphere during the heating period induced disordered arrangement of Ni and Mn while controlling the loss of discharge capacity caused by the formation of impurity phases. This study investigated the effect of conditions during the temperature elevation period of the synthesis while previous research generally focused on the post-heating processes. The method is proposed as a new effective way to control the electrochemical performance of LNMO.