Enhanced Electrochemical Performances of Ni Doped Cr8O21 Cathode Materials for Lithium-ion Batteries

Cathode materials, nickel doped Cr8O21, were synthesized by a solid-state method. The effects of Ni doping on the electrochemical performances of Cr8O21 were investigated. The experimental results show that the discharge capacities of the samples depend on the nickel contents, which increases firstly and then decreases with increasing Ni contents. Optimized Ni0.5Cr7.5O21 delivers a first capacity up to 392.6 mAh·g−1 at 0.1 C. In addition, Ni doped sample also demonstrates enhanced cycling stability and rate capability compared with that of the bare Cr8O21. At 1 C, an initial discharge capacity of 348.7 mAh·g−1 was achieved for Ni0.5Cr7.5O21, much higher than 271.4 mAh·g−1 of the un-doped sample, with an increase of more than 28%. Electrochemical impedance spectroscopy results confirm that Ni doping reduces the growth of interface resistance and charge transfer resistance, which is conducive to the electrochemical kinetic behaviors during charge-discharge.