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

Abstract Rh-doped LiNi 0.5 Mn 1.5 O 4 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 LiNi 0.5 Mn 1.5 O 4 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 LiNi 0.48 Rh 0.02 Mn 1.5 O 4 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 LiNi 0.5 Mn 1.5 O 4 , but also suppressed the destruction of electrolyte during cycling. The thermal stability of LiNi 0.5 Mn 1.5 O 4 was also enhanced by Rh-doping.