Preparation and characterization of macroporous LiNi_1/3Co _1/3Mn_1/3O₂ using carbon sphere as template

Macroporous LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials were synthesized by sol-gel method with carbon spheres as the pore tuning template. The phase structure, morphology and pore nature were analyzed by X-ray diffraction, field-emission scanning electron microscopy and BET measurements. The electrochemical properties were investigated by employing cyclic voltammetry, constant current charge-discharge test, and electrochemical impedance techniques. Well developed layered structures were obtained, and removal of the carbon sphere during the calcination process led to plenty of macropores in the product, compared to the pristine dense sample without using any template. The XRD pattern showed that the structure of porous LiNi _1/3Co_1/3Mn_1/3O₂ was not affected by using the template, as which could be fully indexed to the layered structure of the a-NaFeO₂ phase with crystalline size smaller than that of the pristine one. In contrast to the pristine dense sample, the templated macroporous LiNi_1/3Co_1/3Mn_1/3O₂ showed improved discharge capacity and rate capability. The specific discharge capacity of the macroporous and pristine LiNi_1/3Co _1/3Mn_1/3O₂ materials are around 189 and 155 mAh g^-1 respectively at 20 mA g^-1, and better cycling capacity retention was observed for the porous sample. The electrochemical impedance studies indicated the possible underlying mechanisms of the performance differences between the porous and pristine dense materials. These investigations indicate that the templated macroporous LiNi_1/3Co _1/3Mn_1/3O₂ might be a promising cathode material for lithium-ion battery applications.