Enhanced Electrochemical Performance of Li-Rich Layered Cathode Materials by Combined Cr Doping and LiAlO2 Coating

A Li-rich layered cathode material Li1.2Ni0.2Mn0.6O2 with enhanced electrochemical performance has been fabricated by combining the Cr doping and LiAlO2 coating. The structural characterization shows the perfect layered crystal structure. The 3 wt % LiAlO2-coated Li1.2Ni0.16Mn0.56Cr0.08O2 shows the highest discharge specific capacity and the best cycling stability among different coating levels. The first discharge specific capacity is enhanced from 230.4 mAhg(-1) to 268.8 mAhg(-1). The capacity retention ratio is improved from 92.7% to 97.3% after 100 cycles. The spinel phase is suppressed effectively in the 3 wt % LiAlO2-coated Li1.2Ni0.16Mn0.56Cr0.08O2. The midpoint voltage value of Li1.2Ni0.2Mn0.6O2 after 100 cycles is enhanced from 2.746 to 3.128 V with Cr doping and LiAlO2 coating. The lower R-ct (charge transfer resistance) and higher D-Li(+) (ion diffusion coefficient) of 3 wt % LiAlO2-coated Li1.2Ni0.16Mn0.56Cr0.08O2 contribute to the excellent rate capability. The results suggest that ion doping combined with fast ion conductor coating is an effective way to enhance the electrochemical properties of the Li-rich layered cathode materials.