Study of electrochemical performances of multi-doped spinel Li_1.1Mn_1.85Co_0.075Ni_0.075O₄ at 4.3 and 5 V

Li_1.1Mn_{2 - 2x}Co_xNi_xO₄ (x = 0, 0.075) spinel powders were successfully synthesized using a liquid stirred tank reactor method. The electrochemical performances of the undoped and doped spinels at 4.3 and 5 V were investigated by X-ray diffraction, field-emission scanning electron microscopy, and electrochemical impedance spectroscopy. The capacity of Li_1.1Mn_{2 - 2x}Co_xNi_xO₄ could be divided into two parts, with 4.3 V as the dividing line in the 3-5 V charge-discharge range. Low capacity and good cyclic performance were obtained when cycled in the 3-4.3 V range for the multi-doped Li_1.1Mn_{2 - 2x}Co_xNi_xO₄ spinel. In comparison with multi-doped spinel at 4.3 V, the results of the cyclic performance worsened at 5 V because the structure underwent further shrinkage, the charge transfer resistance rose and the electrolyte decomposed.