Improved electrochemical performance of LiNi0.5Mn1.5O4 as cathode of lithium ion battery by Co and Cr co-doping

Three samples, LiNi 0.5 Mn 1.5 O 4 , LiNi 0.4 Mn 1.4 Co 0.2 O 4 , and LiNi 0.4 Mn 1.4 Cr 0.15 Co 0.05 O 4 , were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi 0.4 Mn 1.4 Cr 0.15 Co 0.05 O 4 exhibits an improved performance compared with the Co-doped sample LiNi 0.4 Mn 1.4 Co 0.2 O 4 and the undoped sample LiNi 0.5 Mn 1.5 O 4 , especially at elevated temperature. At 25 °C, the discharge capacity of LiNi 0.4 Mn 1.4 Cr 0.15 Co 0.05 O 4 is 130 mAh g −1 at 0.1 C and 103 mAh g −1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g −1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi 0.4 Mn 1.4 Co 0.2 O 4 and LiNi 0.475 Mn 1.475 Co 0.05 O 4 , the co-doped sample LiNi 0.4 Mn 1.4 Cr 0.15 Co 0.05 O 4 , with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi 0.5 Mn 1.5 O 4 by the co-doping was discussed.