TiO2 코팅을 통한 Li[Ni0.82Co0.14Al0.04]O2 양극 활물질의 고전압 특성에 관한 연구

Abstract

Titanium dioxide (TiO2) coated layered Li[Ni0.82Co0.14Al0.04]O2 materials are synthesized using a facile dry coating route. The structural and electrochemical properties of pristine and TiO2 coated electrodes are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), galvanostatic charge/discharge tests, electrochemical impedance spectra (EIS), differential capacity (dQ/dV) and differential scanning calorimetry (DSC). The results indicate that the Li[Ni0.82Co0.14Al0.04]O2 particles are partially covered with a TiO2 layer (about 30 nm thick) after 1 wt.% TiO2 surface modification. The coated electrode shows the enhanced initial coulombic efficiency of 94.3% compared to 90.7% for the uncoated electrode. Moreover, the coated electrode exhibits higher capacity retentions, which exhibits capacity retention of 84.5% after 100 cycles compared with 74.6% for the pristine one. Furthermore, the TiO2 coated electrode delivers a superior high rate capacity of 169.3 mAh/g at 5C rate, higher than 146.0 mAh/g for the uncoated electrode. The remarkably improved cycling stability and high rate capacity of the TiO2 coated electrode comes from the presence of a stable and thin TiO2 coating layer which effectively reduces the damage of electrode structure and suppresses the increase of impedance during cycling by preventing direct contact of electrode and electrolyte.