Synthesis and Electrochemical Properties of Mo6+ doped Layered Li[Ni1/3+xCo1/3Mn1/3-2xMox]O2 Cathode Materials for Lithium Secondary Batteries

초록

Layered lithiated transition metal oxides such as LiCoO2, LiNiO2, and LiMnO2 are of great interest for use in the application of lithium rechargeable batteries as positive electrode materials [1,2]. The commercialized LiCoO2 still have disadvantages of high cost and toxicity. LiNiO2 and LiMnO2 have been extensively studied as possible alternatives to LiCoO2. However, LiNiO2 is well known that it is difficult to synthesize in its stoichiometric form and further, delithiated LixNiO2 has poor thermal stability. LiMnO2 was observed to undergo a phase transformation to a spinel-like phase during cycling due to a thermodynamic instablility of the layered structure, causing two voltage plateaus on 3 V and 4 V [3]. Recently, various attempts have been made to enhance the electrochemical performance of LiNiO2-LiCoO2-LiMnO2 solid solution [4,5]. Li[Ni1/3Co1/3Mn1/3]O2 has been suggested as an alternative to LiCoO2 because Ni, Co, and Mn can be substituted each other to form a solid solution of any percentage without disturbing the layer structure. Recently, we reported on the synthesis and electrochemical properties of Li[Ni1/3Co1/3Mn1/3]O2 powder prepared by an ultrasonic spray pyrolysis method [6]. The ultrasonic spray pyrolysis is an effective synthetic technique having advantages such as a good stoichiometric control, homogeneous precursor, short production time, and spherical morphology. In this work, we have attempted to synthesize Mo6+ ion doped Li[Ni1/3+xCo1/3Mn1/3-2xMox]O2 (x in 0-0.05) materials using MoO3 as a dopant.