Enhanced Li-storage performance of In-doped Li1.21[Mn0.54Ni0.125Co0.125]O2 as Li- and Mn-rich cathode materials for lithium-ion batteries

Lithium manganese-rich nickel-manganese-cobalt oxides (LMR-NMCs) are promising candidates for cathodes in Li-ion batteries (LIBs) due to their high voltage (exceeding 4.5 V vs. Li (Li+)(-1)) and capacity (similar to 250 mAh g(-1)). However, LMR-NMCs become involved in an irreversible structural change from the layer form to the spinel-type form after a short-term lithium deintercalation (charging) and intercalation (discharging) process. In this study, the Li-1.21[Mn0.54-xNi0.125Co0.125]InxO2 (x = 0, 0.01, 0.015, and 0.02) cathode materials were prepared via a sol-gel approach to overcome the phase transformation of pristine structure with In-doping. The structural, chemical, and thermal properties of the indium replacement with manganese within the prepared Li-1.21[Mn0.54-xNi0.125Co0.125]InxO2 were examined with tools such as X-ray diffraction, field-emission scanning electron microscopy, thermogravimetric analysis/differential thermal analysis, transmission electron microscopy, surface area analysis, and a Fourier-transformed infrared spectrophotometer. The electrochemical and Li-storage performances of the fabricated electrodes with the change of molar ratio of indium as an elemental dopant concerning specific capacity and cycling stability at different rate of charge/discharge were examined. The cyclic stabilities and specific charge/discharge capacities of the doped and undoped mesoporous LMR-NMCs with different amounts of indium determine the appropriate amount of indium is for x = 0.015 with the high charge/discharge capacities and improved cycling stability performance (large discharge capacity of 297.2 mAh g(-1) at the 0.1 C with 98.5% capacity retention after 50 cycles and high discharge capacity of 222 mAh g(-1) at high rate of 1 C). Interpretation of this improvement for the electrode prepared with x = 0.015 of indium can be due to more regular expanded crystallite sites, leading to improved insertion/deinsertion of lithium-ion in high rate of charge-discharge and also retain the crystal structure during cycles compared to the other fabricated electrodes.