Novel Composite Air Electrode for Lithium-Air Battery
Lee, Shu Han
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The motivation of this research is to fabricate a novel composite electrode which contains an electrically conductive substrate, a catalyst layer, and a conductive polymer (cp) layer sandwiched between the substrate and the catalyst layer. The oxygen reduction activity of the novel composite electrode is studied and evaluated. The novel composite electrode is capable of enhancing the sluggish oxygen reduction reaction (ORR) in a nonaqueous Li-air battery. A systematic approach has been applied to this study by first demonstrating the feasibility of depositing a conductive polypyrrole (PPy) layer on a two-dimensional (2D) conductive substrate and the viability of depositing a Ag catalyst layer on top of the PPy layer. The ORR activity of each layer was evaluated in a three-electrode electrochemical cell using cyclic voltammetry. The ORR experiment results indicate the composite electrode exhibited enhanced ORR activity over the carbonaceous material used in a conventional air cathode. Quantification methods for the cp layer and the catalyst layer have been developed. The contribution of each individual component toward the activity of the composite electrode has been assessed. A three-dimensional (3D) composite electrode has been fabricated successfully by the preparation methods used in the preparation of 2D composite electrodes, yielding composite electrodes with ~4x the oxygen reduction capacity of their planar counterpart. The effects of water amount on the nonaqueous ORR mechanism have been investigated, and the results provide quantitative understandings of the nonaqueous ORR upon water addition, indicated by the reductive currents on various types of electrode materials. Improvements of oxygen reduction activity at the novel composite air electrode will increase the current capability and the power output of the metal air battery, facilitating future development of small, lightweight, and long-life power sources.