Magnesium-doped Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode with high rate capability and improved cyclic stability

Mg-doped Li[Li0.2Mn0.54-x/3Ni0.13-x/3Co0.13-x/3Mgx]O-2 (x=0, 0.005, 0.007, 0.01, and 0.02) cathode materials have been synthesized by mixing Mn0.54Ni0.13Co0.13(CO3)(0.8) precursor, Li2CO3, and MgO, followed by high-temperature solid-state method. X-ray diffraction (XRD) results show that Mg-doped samples have enlarged interlayer distance and orderly layered structure. Scanning electron microscope (SEM) results indicate that all the samples have similar morphologies. Electrochemical tests indicate that Mg doping facilitates the activation of Li2MnO3 phase and suppresses the transformation from layered to spinel-like phase. Mg-doped samples possess improved cyclic and rate performance. The Li[Li0.2Mn0.54-x/3Ni0.13-x/3Co0.13-x/3Mgx]O-2 (x=0.01) sample delivers a capacity retention of 92.07% compared with 75.25% of the undoped one after 200cycles at 250mAg(-1) and exhibits the discharge capacity of 198.56mAhg(-1) at 500mAg(-1). The reasons for the improved electrochemical performance are the enlarged interslab spacing and the enhanced structural stability.