Surface modification of LiNi0.5Mn1.5O4 by ZrP2O7 and ZrO2 for lithium-ion batteries

Abstract The spinel LiNi 0.5 Mn 1.5 O 4 has been surface modified separately with 1.0 wt.% ZrO 2 and ZrP 2 O 7 for the purpose of improving its cycle performance as a cathode in a 5-V lithium-ion cell. Although the modifications did not change the crystallographic structure of the surface-modified samples, they exhibited better cyclability at elevated temperature (55 °C) compared with pristine LiNi 0.5 Mn 1.5 O 4 . The material that was surface modified with ZrO 2 gave the best cycling performance, only 4% loss of capacity after 150 cycles at 55 °C. Electrochemical impedance spectroscopy demonstrated that the improved performance of the ZrO 2 -surface-modified LiNi 0.5 Mn 1.5 O 4 is due to a small decrease in the charge transfer resistance, indicating limited surface reactivity during cycling. Differential scanning calorimetry showed that the ZrO 2 -modified LiNi 0.5 Mn 1.5 O 4 exhibits lower heat generation and higher onset reaction temperature compared to the pristine material. The excellent cycling and safety performance of the ZrO 2 -modified LiNi 0.5 Mn 1.5 O 4 electrode was found to be due to the protective effect of homogeneous ZrO 2 nano-particles that form on the LiNi 0.5 Mn 1.5 O 4 , as shown by transmission electron microscopy.