Improvement the electrochemical performance of Cr doped layered-spinel composite cathode material Li _1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 with Li₄Ti ₅O₁₂ coating

The Cr doped layered-spinel composite cathode material Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 was synthesized and coated with different content of Li₄Ti₅O₁₂ by a sol–gel method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effect of Li₄Ti₅O₁₂ coatings on the electrochemical performance of the pristine material was evaluated from charge/discharge cycles, rate performance, and electrochemical impedance spectroscopy (EIS). The XRD results show that the lattice crystal and the content of spinel phase have been increased in the Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 materials after Li₄Ti₅O₁₂ coating. The results from TEM and selected area electron diffraction (SAED) indicate that the Li₄Ti₅O₁₂ coating assumes a spinel structure on the Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3. The discharge capacities, cycling and rate performances of the Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 materials in the first cycle are improved with the addition of Li₄Ti₅O₁₂. Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 coated with 3 wt% Li₄Ti₅O₁₂ shows the highest discharge capacity (271.7 mA h g⁻¹), highest capacity retention (99.4% for 100 cycles), and best rate capability (132 mA h g⁻¹ at 10 C). EIS result indicates that the resistance of Li_1.1Ni_0.235Mn_0.735Cr_0.03O_2.3 electrode decreases with the addition of Li₄Ti₅O₁₂. The enhanced electrochemical performance can be ascribed to the increased spinel content, lower resistance and the enhanced lithium-ion diffusion kinetics.