Polyaniline Nanocoating on the Surface of Layered Li[Li_0.2Co_0.1Mn_0.7]O₂ Nanodisks and Enhanced Cyclability as a Cathode Electrode for Rechargeable Lithium-Ion Battery

The surfaces of layer-structured Li[Li 0.2 Co 0.1 Mn 0.7 ]O 2 nanodisks were nanocoated with polyaniline and examined by SEM and TEM studies, via the chemical oxidative polymerization of aniline in an acid medium for 10 min—Mn 4+ ions in the pristine lithium manganese oxides acted as oxidants. During this reaction, the crystal structure of the pristine nanodisks was retained, and the XRD patterns showed no evidence of H + exchange with the Li + located between the manganese oxide layers. The nanocoated polyaniline was in the low molecular weight of base states, and the majority (∼70%) was complexed with Li[Li 0.2 Co 0.1 Mn 0.7 ]O 2 nanodisks, as shown by UV−vis and FT-IR spectroscopic analysis. By application of nanocoated polyaniline nanodisks as the cathode material, the discharge capacity was improved by about 15%. Furthermore, the cyclability was enhanced with almost no change in discharge capacity being detected at extended cycle numbers, while that of pristine nanodisks showed a tendency to continually decrease as the number of cycles increased. Results from the present study suggest that a well-controlled polyaniline nanocoating, particularly formed with the aid of pristine metal oxides as oxidants for polymerization, can act as a potential buffer layer between electrodes and electrolytes, which makes this a promising method for the reducing/protection of continuous structural distortion that occurs during extended charge−discharge cycling.