Manganese Oxide Composite Material Synthesis And Characterization Of

In this dissertation,α-MnO₂ spheres, polyaniline (PANI)/α-MnO₂ composites and spinel LiMn₂O₄ microspheres have been successfully synthesized, respectively. Their electrochemical properties have been characterized, accordingly. The details are presented as follows:Firstly, Chrysanthemum-like and sphericalα-MnO₂ particles were synthesized via a chemical co-precipitation method under acidic conditions. SEM study indicates that the as-synthesizedα-MnO₂ spheres are uniform, with diameters ranging from 3 to 6μm. It is found that the mild reaction condition facilitates the formation ofα-MnO₂ spheres. The formation mechanism of theα-MnO₂ spheres was discussed based on the experimental results.Secondly, with the as-preparedα-MnO₂ spheres as the oxidant, polyaniline (PANI) was in situ coated on the surface of MnO₂ by oxidative polymerization of aniline in H₂SO₄ medium. The structural and morphological characterization have been carried out through IR spectrum, scanning electronmicroscope, X-ray diffraction and so on, while electrochemical properties of electrode materials have been evalued using cyclicvoltammetry and galvanostatic charge-discharge studies. Electrochemical studies show that The obtained PANI/α-MnO₂ composite at room temperature exhibit fine electrochemical properties in 1M Na₂SO₄ aqueous electrolyte solution. The maximum specific capacitance of the PANI/α-MnO₂ composite prepared with a mass ratio of starting aniline toα-MnO₂ of 1:10 is 75.10 F/g, while 0.78 and 42.14 F/g for PANI andα-MnO₂, respectively. Furthermore, above 77% of the initial specific capacitance for the PANI/α-MnO₂ composite can be maintained after 500 cycles, while only 62% forα-MnO₂.Thirdly, spinel LiMn₂O₄ product was synthesized by high temperature solid-state reaction with the pre-obtainedα-MnO₂ spheres as precursors. SEM images indicate that the obtained LiMn₂O₄ particles are microspheres with diameters of 5-10μm and the size distribution is uniform. Charge-discharge tests show that the received LiMn₂O₄ product exhibits a charge-discharge capacity of 105.1 and 99.8 mAh/g at a 0.1 C rate. After 30 cycles, the as-synthesized LiMn₂O₄ maintains 96.4% of its initial capacity.