Effects of Al and Co doping on the structural stability and high temperature cycling performance of LiNi0.5Mn1.5O4 spinel cathode materials

Abstract

The poor structural stability and capacity retention of the high-voltage spinel-type LiNi0.5Mn1.5O4 (LNMO) limits their further application. Herein, Al and Co were doped in LNMO materials for a more stable structure and capacity. The LNMO, LiNi0.45Al0.05Mn1.5O4 (LNAMO) and LiNi0.45Co0.05Mn1.5O4 (LNCMO) were synthesized by calcination at 900 °C for 8 h, which was called as solid-phase method and applied universally in industry. XRD, FT-IR and CV test results showed the synthesized samples have cation disordering Fd-3m space group structures. Moreover, the incorporation of Al and Co increased the cation disordering of LNMO, thereby increasing the transfer rate of Li+. The SEM results showed that the doped samples performed more regular and ortho-octahedral. The EDS elemental analysis confirmed the uniform distribution of each metal element in the samples. Moreover, the doped samples showed better electrochemical properties than undoped LNMO. The LNAMO and LNCMO samples were discharged with specific capacities of 116.3 mA·h·g−1 and 122.8 mA·h·g−1 at 1 C charge/discharge rate with good capacity retention of 95.8% and 94.8% after 200 cycles at room temperature, respectively. The capacity fading phenomenon of the doped samples at 50 °C and 1 C rate was significantly improved. Further, cations doping also enhanced the rate performance, especially for the LNCMO, the discharge specific capacity of 117.9 mA·h·g−1 can be obtained at a rate of 5 C.