Synthesis of sub-micron LiNi0.5Mn1.5O4 with uniform size distribution by oleylamine-assisted solid-state method

Abstract

Sub-micron LiNi0.5Mn1.5O4 (LNMO) with uniform size distribution is synthesized by oleylamine-assisted solid-state method (oley-ss-method). Different from the traditional solid-state method (ss-method), the size distribution of LNMO sample prepared by oley-ss-method is more uniform and the particle size is smaller. Oleylamine inhibits the formation of large particles and refines the particle size of the sample during synthesis. For comparative analysis, the LNMO material without oleylamine is simultaneously synthesized by ss-method and both products are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and electrochemical tests, respectively. XRD patterns show that the LNMO samples with a good crystalline spinel structure are successfully synthesized using ss-method and the impurities of LixNi1−xO are reduced in the presence of oleylamine. SEM shows that the particle size and size distribution of LNMO sample modified by oleylamine has been significantly reduced, and large-sized particles decreased. The FTIR indicated that the LNMO sample assisted by oleylamine belongs to the Fd3m space group, not P4332. Compared with the unmodified LNMO, the electrochemical performance of the oleylamine-modified LNMO sample is significantly enhanced, and the specific capacity of 97.4 mA h g−1 is still maintained after 700 cycles at a discharge rate of 5 C.