Facile and scalable fabrication of K+-doped Li1.2Ni0.2Co0.08Mn0.52O2 cathode with ultra high capacity and enhanced cycling stability for lithium ion batteries
Abstract Lithium rich layered cathode materials have attracted widespread attention due to their high capacity over commercial cathode materials (LiCoO2, LiFePO4 and LiMn2O4) but suffered from capacity fade, low coulombic efficiency and poor rate capability. Here we present a K+-doped lithium-rich cathode material using a simple and scalable co-precipitation method. Compared with the pristine one, the K+-doped sample exhibits an extremely high discharge capacity (280.4 mAh g−1 at 0.5 C) and excellent cycling stability (93.4% capacity retention after 200 cycles). Meanwhile, the initial coulombic efficiency rises from 76.4% to 80.7% after K+ doping. X-ray diffraction (XRD) and scanning electron microscope (SEM) show that K+-doped sample has more well-defined layered structure and enlarged Li layers that can facilitate Li+ diffusion in crystal lattice. Kinetic properties of Li-rich cathode have been investigated by electrochemical impedance spectroscopy (EIS) measurements, and the results show that the charge transfer activation energy (53.5 kJ mol−1) is much smaller than the lithium diffusion activation energy (122.5 kJ mol−1), suggesting that electrochemical process dynamics of the lithium rich oxide electrode is controlled by the solid-state ionic diffusion.