Yttrium modified Ni-rich LiNi0.8Co0.1Mn0.1O2 with enhanced electrochemical performance as high energy density cathode material at 4.5 V high voltage

This work adopts an effective method to stabilize the structure of Ni-rich LiNi0.8Co0.1Mn0.1O2 with yttrium modifying. The results of XRD, EDS, HR-TEM and XPS tests verify that the yttrium modified materials integrate surface nanoscale LiYO2 coating and inner gradient Y3+ doping. TGA and DSC tests confirm that yttrium modification can promote the thermal stability of LiNi0.8Co0.1Mn0.1O2 cathode material. The results of galvanostatic charge-discharge tests suggest that the 2 mol% yttrium modified sample can exhibit a superior cycling performance with initial discharge capacity of 189.4 mAh g−1 and outstanding capacity retention of 98.4% after 100 cycles at 2.8-4.5 V, which presents obvious enhancement compared with the 83.5% capacity retention of pristine sample. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests indicate that 2 mol % yttrium modifying significantly enhances the diffusion of Li+ ions (DLi+) and notably decreases the electrochemical polarization of electrodes. The surface Li-ion conductor LiYO2 coating layer as a surface protector inhibits the side reaction and the gradient Y3+ doping supports the crystal structure, which can show synergistic effect in enhancing the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode material.