Ba‐doping to Improve the Cycling Stability of LiNi0.5Mn0.5O2 Cathode Materials for Batteries Operating at High Voltage

Abstract LiNi 0.5− x Ba x Mn 0.5 O 2 ( x= 0, 0.03, 0.05, 0.08) samples were prepared by using a combination of co‐precipitation and solid‐state methods. All of the cathode materials were analyzed by inductively coupled plasma mass spectrometry (ICP‐MS), X‐ray diffraction (XRD), Rietveld refinement, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results of them show that we have successfully prepared the target materials, and Ba‐doping can keep the structure stable and lower Li/Ni cation mixing. In addition, Ba‐doping does not change the structure, the chemical states, or the morphology of LiNi 0.5 Mn 0.5 O 2 . The electrochemical properties of the samples were explored systematically by rate performance and charge–discharge tests at room temperature and high temperature. The performances of the cathode materials indicate that 5 mol % Ba‐doping of LiNi 0.5 Mn 0.5 O 2 can improve the capacity retention at 0.2 C by approximately 41 % and 13 %, at room temperature and 60 °C, respectively. in the range between 2.5 and 4.8 V. In addition, the 5 mol % Ba‐doped material shows better rate performances than that of the un‐doped material, especially at higher current densities. Cyclic voltammetry (CV) and electrochemical impedance spectroscope (EIS) tests were used to analyze the reason for the improved electrochemical properties, which may be attributed to lower Li/Ni cation mixing, higher structural stability, lower polarization, and lower charge transfer resistance.