Enhanced cyclic performance of MgF2-coated Li[Ni0.2Li0.2Mn0.6]O2 nanoparticle cathodes in full lithium ion cells

In this study, the cyclic performances of pristine and MgF2-coated Li[Ni0.2Li0.2Mn0.6]O-2 nanoparticle electrodes were compared and characterized. The electrochemical performance of a full lithium ion cell with Li[Ni0.2Li0.2Mn0.6]O-2 as the cathode and carbon as the anode was tested and the carbon anode was analyzed after cycling, using SEM, EDS, and XPS. The cyclic performance of full cells was found to be inferior to that of half cells, which may be attributed to the damage caused to the carbon anode due to dissolution of transition metals from the cathode. The surface of the carbon anode cycled with the pristine Li[Ni0.2Li0.2Mn0.6]O-2 cathode was found to be contaminated with Mn and Ni, whereas the carbon anode cycled with the MgF2-coated Li[Ni0.2Li0.2Mn0.6]O-2 cathode contained a much smaller amount of transition metals. This indicates that the MgF2 coating on the cathode effectively suppressed the dissolution of transition metals from Li[Ni0.2Li0.2Mn0.6]O-2, resulting in a better cyclic performance of the MgF2-coated Li[Ni0.2Li0.2Mn0.6]O-2 electrode compared to the pristine electrode. The MgF2 coating was also effective in decreasing the impedance of lithium ion cells before and after cycling.