Improved electrochemical performance of LiNi0.5−xRhxMn1.5O4 cathode materials for 5 V lithium ion batteries via Rh-doping

Rh-doped LiNi0.5Mn1.5O4 has been prepared for the first time as the 5 V cathode materials of lithium ion batteries. The samples were characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma analysis and electrochemical measurements. The results indicated that the rate capability and cycling stability of LiNi0.5Mn1.5O4 at 25 and 55 °C was effectively improved by doping with 2 mol% Rh. At a 3000 mA g−1 (20 °C) charge/discharge rate, the LiNi0.48Rh0.02Mn1.5O4 sample still delivered an initial discharge capacity of 92.4 mAh g−1 at 25 °C. Furthermore, it maintained 83.6% of its initial capacity after 300 cycles under a 150 mA g−1 current rate (1 °C) at 55 °C. These improvements were principally attributed to Rh-substitution, which not only enhanced the electronic conductivity and lithium ion diffusion ability of LiNi0.5Mn1.5O4, but also suppressed the destruction of electrolyte during cycling. The thermal stability of LiNi0.5Mn1.5O4 was also enhanced by Rh-doping.