Effects of polyaniline coating of cryptomelane-type KMn₈O₁₆ on electrochemical performance for lithium-ion batteries

KMn₈O₁₆ nanorods were synthesized via a reflux method, and polyaniline-coated KMn₈O₁₆ nanorods were prepared via oxidative polymerization of aniline in acidic medium. The microstructures and morphologies of the KMn₈O₁₆ nanorods and PANI-coated KMn₈O₁₆ nanorods were characterized using powder X-ray diffraction, thermogravimetric analysis, Raman measurements, scanning electron microscopy, and transmission electron microscopy. The as-prepared KMn₈O₁₆ and PANI-coated KMn₈O₁₆ are all mainly composed of nanorods with a diameter around 5–20 nm and a length of around 100–300 nm. The electrochemical measurements demonstrated that the KMn₈O₁₆ nanorods as cathode material have both higher reversible capacity of 168 mAh g⁻¹ at 50 mA g⁻¹ current density and excellent cycling performance in lithium-ion batteries at room temperature over 100 cycles, in the range 1.5–4.2 V. PANI-coated KMn₈O₁₆, in addition to its excellent cyclability, presented a much higher reversible discharge capacity. The PANI-coated KMn₈O₁₆ composite could retain a discharge capacity of 183 mAh g⁻¹ after 100 cycles.