Preparation of 4.7 V cathode material LiNi0.5Mn1.5O4 by an oxalic acid-pretreated solid-state method for lithium-ion secondary battery

LiNi0.5Mn1.5O4 as a 4.7 V cathode material is prepared through an oxalic acid-pretreated solid-state method. Oxalic acid is added to react with the mixture of LiOH center dot H2O, MnO2 and Ni(OH)(2). This chemical pretreatment results in a sufficient mixing of Li. Ni and Mn ions in the precursor, and therefore promotes the generation of pure LiNi0.5Mn1.5O4 in the following calcination even at a temperature as low as 500 degrees C. The material prepared at 750 degrees C has a highest crystallinity and a regular crystal shape with smoothly surface. Compared to traditional method, the LiNi0.5Mn1.5O4 synthesized by this novel method shows much better electrochemical performances with an initial discharging capacity of 136.9 mAh g(-1) and capacity retention of 93.4% after 300 cycles under 0.3C. And most importantly 97.2% of the total capacity displays at 4.7 V, which significantly favors the cell energy density. The novel preparation technique is also available to get high rate performance for LiNi0.5Mn1.5O4. The material synthesized at 900 degrees C has a capacity of 121.2 mAh g(-1) and stable cycling performance under 3C due to its lower polarization resistance. (C) 2012 Elsevier B.V. All rights reserved.