Cu-doped NaCu0.05Fe0.45Co0.5O2 as promising cathode material for Na-ion batteries: synthesis and characterization

In this work, Cu-doped NaFe 0.5 Co 0.5 O 2 was easily prepared by a one-step solid-state reaction and studied the effect of copper salt precursors including CuCl 2 and Cu(OAc) 2 on the structure and electrochemical properties. XRD patterns of the synthesized materials all exhibited diffraction peaks of O3-type layered oxide with high crystallinity and negligible impurity of halide compound. Using Cu(OAc) 2 precursor showed a well-defined voltage profile feature of NaFe 0.5 Co 0.5 O 2 material and a superior performance in sodium half-cell. Doped samples exhibited a capacity of 130 mAh g −1 which is higher than pristine NaFe 0.5 Co 0.5 O 2 and good capacity retention for 100 cycles. Ex situ XRD results indicated the complex phase transition above 4 V on the first charge, but the structure of the Cu-doped materials remained O3-type layered after the end of cycling. Additionally, Cu-doping effectively enhanced Na + diffusion coefficients also indicated using the cyclic voltammetry method.