Improved cyclic stability of LiNi0.8Co0.1Mn0.1O2 via Ti substitution with a cut-off potential of 4.5 V

To improve the cyclic stability of LiNi0.8Co0.1Mn0.1O2 cycled between 2.8 and 4.5 V vs. Li/Li+, titanium was incorporated into LiNi0.8Co0.1Mn0.1O2 at various molar concentrations of 1, 2, 3 and 5% during the synthesis. The XRD, EDS and XPS analyses indicated that the titanium ions were effectively incorporated into the lattice of ternary oxides by occupying the transitional metal positions. Among the investigated molar concentrations, 2% Ti-substituted LiNi0.8Co0.1Mn0.1O2 exhibited the best multifaceted performances with a relatively high capacity (205.7 mA h g−1 at 0.1 C), good rate capability (178.2 mA h g−1 at 1 C, 155.3 mA h g−1 at 5 C) and acceptable cyclic stability (86.9% at the 200th). The post-mortem analysis indicated that Ti substitution alleviates cracking from secondary particles to primary ones. This behavior is most likely due to the decreased ratio of volumetric deformation (i.e., 4.82% for the 2% Ti-substituted sample, which is 19.8% lower than that of the pristine one). Our results demonstrate that mechanical properties may play a crucial role in its long cyclability for use as a high-capacity ternary cathode.