Surface modification of hollow microsphere Li 1.2 Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode by coating with CoAl 2 O 4

Li 1.2 Ni 1/3 Co 1/3 Mn 1/3 O 2 was synthesized as a cathode material for lithium-ion batteries and coated with various amounts of CoAl 2 O 4 (0–5 wt%) at high temperature. The effect of the surface modification on the structure and electrochemical performance of the cathode was evaluated. Microstructural analysis using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy revealed that the CoAl 2 O 4 coating did not affect the crystal structure of the electrode material and that the coating only appeared on the electrode surface. The effect of the CoAl 2 O 4 coating on the electrochemical performance was evaluated by examining charge-discharge cycles, rate performance, and electrochemical impedance. The cathodes coated with CoAl 2 O 4 exhibited improved discharge capacity and cyclic performance compared with those of the uncoated cathode. The electrode coated with 2.5 wt% CoAl 2 O 4 exhibited the highest discharge capacity (202.5 mAhg −1 vs. 185 mAhg −1 for the uncoated material) and highest capacity retention (84.8% for 50 cycles vs. 78.6% for the uncoated material).