| With the rapid development of the society, the current battery can not fulfill the requirement of many high-energy electronic devices, especially the electric vehicles. Lithium–air battery has attracted worldwide attention due to its extremely high theoretical energy densities (5200Wh/kg including oxygen). In the category of lithium-air battery, the aprotic system has attracted a great deal of attention.However, there are many factors, including the large overpotential, the impact of water molecule and carbon dioxide, which limit the development of the battery. In order to promote industrial production, the as-made battery was tested in the air.Therefore, we first made a waterproof membrane, through which oxygen can pass, while keeping out environmental contaminants (water molecule and carbon dioxide) to reduce the side reaction. The optimal hydrothermal time and temperature were determined by analyzing its the effect on the structural morphology and catalytic properties of α-MnO2nanowires. Pore clogging of the air eletrode is the main factor of the capacity loss in lithium–air batteries by analyzing experimental data, so the matching relationship of α-MnO2nanowires and Super P and graphite were investigated, and a structure model of air electrode has been established in the following. In addition, the effect of the battery structure and discharge condition were also the factors of the battery performance. And intensive research efforts have been devoted to improve the synthetic method of α-MnO2.XRD, SEM, nitrogen adsorption-desorption and LSV results indicated that α-MnO2nanowires with desired catalytic performance has been successfully synthesized under180oC,12h and the BET surface area in this experiment was found to be66.4603m2/g.The prepared cell was split into positive electrode, negative electrode, glass fiber separator and PP separator at the end of discharge, and then assembled into four groups of new cell. The results of the discharge curves and EIS confirmed that the performance of the battery has been limited by positive elecrode due to the blocking of the reacting sites. Graphite and Super P were used as conductive agent with proper particle size compared to α-MnO2. By adjusting the ratio of MnO2and carbon materials, the size of the obtained poprous air eletrode is from micropore to macropore. The initial discharge capacity is3272.3mAh/g in Super P system with more micropore and mesopore, while it is only200.0mAh/g in graphite system with more macropore. The batteries with porous cathode casting a mixture of MnO2, graphite and Super P in quality ratio9:12:6:5can deliver capacities of649.5mAh/g and775.4mAh/g in the initial and second discharge. The battery with16.2mm diameter cathode has the longest discharge time lasting5241min, which revealed that the active material of the cathode is fully utiilzed. The initial discharge capacity of the cell with double holes is slightly higher than that of the cell with single hole, but the impedance is larger than that of the cell with single hole, which is harmful for the cycling performance. Limiting the discharge capacity to259.7mAh/g,8cycles can be obtained, and the discharge voltage of the battery is about2.4V. α-MnO2composite catalyst with5%Fe3+significantly reduced agglomeration and improved catalytic performance than α-MnO2nanowire.Micropore and mesopore provided reaction sites for the reaction, while the macropore provided transmission channel for the Li+and oxygen. Based on this, a structure model of air electrode has been established. |
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