Synthesis and electrochemical properties of molybdenum doped Li[Ni(0.5+x)Mn(0.5-2x)Mo(x)]O2 cathode materials prepared by ultrasonic spray pyrolysis

Abstract

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. 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. In this work, Molybdenum doped layered Li[Ni(0.5+x)Mn(0.5-2x)Mox]O2 materials were synthesized by an ultrasonic spray pyrolysis method. Single phase of Li[Ni(0.5+x)Mn(0.5-2x)Mox]O2 could be prepared in 0≤x≤0.05 region. Structural and electrochemical properties of the Li[Ni(0.5+x)Mn(0.5-2x)Mox]O2 were characterized by means of X-ray diffraction, Rietveld refinements, and galvanostatic charge/discharge test. The discharge capacity increased linearly with the increase of molybdenum contents, x, and exhibited a high discharge capacity over 175 mAh/g between 2.8 and 4.4 V with a good capacity retention.