Improvement the electrochemical performance of Cr doped layered-spinel composite cathode material Li 1.1Ni0.235Mn0.735Cr0.03O2.3 with Li4Ti 5O12 coating
The Cr doped layered-spinel composite cathode material Li1.1Ni0.235Mn0.735Cr0.03O2.3 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 Li1.1Ni0.235Mn0.735Cr0.03O2.3 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 Li1.1Ni0.235Mn0.735Cr0.03O2.3. The discharge capacities, cycling and rate performances of the Li1.1Ni0.235Mn0.735Cr0.03O2.3 materials in the first cycle are improved with the addition of Li4Ti5O12. Li1.1Ni0.235Mn0.735Cr0.03O2.3 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 Li1.1Ni0.235Mn0.735Cr0.03O2.3 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.