Synergistic effect of Mg and Y co-dopants on enhancement of electrochemical properties of LiNi0.5Mn1.5O4 spinel

The LiNi0.5–xMgxMn1.48Y0.02O4 (x = 0.005, 0.01, 0.03) and LiNi0.5Mn1.5O4 (LNMO) cathode materials were synthesized successfully through a citric acid aided route. The relationship between material characteristics (structure and morphology) and electrochemical properties of LNMO cathode materials was investigated. It was found that synergistic effect of co-doped magnesium and yttrium ions resulted in marked enhancement of electrochemical properties of LNMO cathode. SEM observation showed that Mg-Y co-doped samples possessed spinel structure with truncated octahedron morphology. After co-doping Mg and Y, the XRD and TEM analyses showed that lattice parameters for LNMO samples were improved, thus improving the rate and cycling property. XPS results of Mg-Y co-doped spinel LiNi0.5Mn1.5O4 indicated the presence of Mg2+ and Y3+ in the spinel lattice. Notably, LiNi0.49Mg0.01Mn1.48Y0.02O4 exhibited both optimal cycling stability and rate performance. LiNi0.49Mg0.01Mn1.48Y0.02O4 sample retained specific capacity of 131 mAh g−1 after 100 cycles at high current density of 1 C with superior retention of 98.49% and the specific capacity reached 118 mAh g−1 at 5 C. While undoped sample only retained 107 mAh g−1 after 100 cycles at 1 C with lower retention of 94.69% and its specific capacity was 84 mAh g−1 at 5 C.