The Doping Effect on The Electrochemical Performance of LiNi0.305Mn0.33Co0.33M0.025O2 (M=Al, Y, Cr) for Lithium-ion Batteries

摘要

LiNi0.305Mn0.33Co0.33M0.025O2 (M=Al,Y,Cr) materials were synthesized via the sol-gel method.The structure and electrochemical properties were characterized by X-ray diffraction (XRD),scanning electron microscope (SEM),cyclic voltammetry (CV),electrochemical impedance spectroscopy (EIS) and charge/discharge tests.The materials were maintained the α-NaFeO2 type layered structure and the discharge capacity was also increased by doping.The Y- and Al- doping slightly decrease the initial discharge capacity of LiNi0.33Mn0.33Co0.33O2 while the Crdoping can increase the initial discharge capacity.The cycling performances are improved after doping.When cycled at 1.0C,about 99％,98.6％ and 97.1％ of their initial capacities can be retained after 40 cycles for Y-,Al- and Crdoped materials,respectively.Their rate capabilities are also better than that of the un-doped one.EIS measurement shows that the Y-doped electrode has the lowest resistance impedance value during cycling.