A New Concept of an Air-Electrode Catalyst for Li2O2 Decomposition Using MnO2 Nanosheets on Rechargeable Li-O-2 Batteries

摘要

To improve the charge/discharge properties of a rechargeable Li-O-2 battery (LAB), we synthesized a new air-electrode catalyst composed of MnO2 nanosheets (Mn-NSs) and Ketjen Black (KB), i.e., a KB-comp. Mn-NS catalyst. The composite catalyst was synthesized by electrostatically restacking the nanomaterials in a colloidal solution with Li+ and its electro-catalytic activity as an air-electrode for a LAB test cell was evaluated. The KB-comp. Mn-NS catalyst exhibited excellent performance, especially for oxidation of Li2O2 deposited on the surface of the air-electrode during the charging process, which led to enhanced reversibility of the Li2O2 deposition/decomposition reaction during the discharging/charge cycles. Evidence of these reactions was investigated and confirmed by X-ray diffraction analysis and scanning electron microscopy-energy dispersive X-ray spectroscopy. The Li2O2 was deposited and decomposed more homogeneously at the air-electrode with the KB-comp. Mn-NS catalyst than that with only KB. Consequently, the composite catalyst significantly reduced the overpotential and improved the cycleability up to the 27th cycle, even at 0.40 mA. (C) 2017 Elsevier Ltd. All rights reserved.