Experimental and mechanism research of gradient structured LiNi0.8Co0.1Mn0.1O2 cathode material for Li-ion batteries

NCM811 precursor with concentration gradients is prepared by adjusting the feeding method of MnSO4 center dot H2O in the co-precipitation method. X-ray diffraction patterns show that the precursors have good crystal structure of beta-Ni(OH)(2). Energy dispersive X-ray spectroscopy shows that the precursor sample performs relatively gentle concentration gradient distributions and scanning electron microscope presents that the precursor delivers a good sphericity and concentrated particle size distribution. The prepared NCM811 material also has good crystal structure and gentle concentration gradient distributions. Electrochemical tests show that it exhibits a better cycle performance of 98.0% capacity retention after 200 cycles at the current density of 1C, which is obviously better than the intrinsic material (87.5%). X-ray diffraction patterns presents unchanged crystal structure and transmission electron microscopy presents clear lattice fringes after 200 cycles. In contrast, part of crystal structure of the intrinsic material transforms into NiO2 phase and Ni in Li layer occupying is very serious after 200th cycles and its lattice fringes are distorted with irregular direction. All of these results exhibit that the side reactions between nickel ions and the electrolyte can be effectively suppressed through the design of gradient structure, so it can improve the structural stability and cycle stability.