Preparation And Performance Research Of High Efficient Cathode Catalyst For Lithium-Oxygen Batteries

With the rise of new energy electric vehicles,people’s demand for energy density of secondary batteries increases greatly.Lithium-oxygen batteries have attracted wide attention because of its extremely high theoretical energy density.However,there are also two major challenges in the lithium-oxygen battery system,that is,the high overpotential and many side reactions.These two aspects will interact with each other,resulting in poor electrochemical performance of lithium oxygen battery,such as low energy efficiency,poor cycle performance,low actual capacity and poor rate capability and so on-Therefore,in order to improve the performance of lithium-oxygen battery,it is particularly important to research and develop efficient new catalysts.In this paper,considering the key problems of the current lithium-oxygen battery system,we explored several solid/liquid catalysts with high performance.The results are listed as follows:1、Nano-spherical nickel sulfide(NiS)grown in-situ on porous carbon foil as the oxygen electrode of lithium-oxygen battery.The electrochemical performance of lithium-oxygen battery has been effectively improved by the electrochemical performance tests.The result showed that the ORR/OER overpotential of the battery with NiS catalysts decreased from 1.28 V to 0.61 V and the capacity increased from 7.49 mAh/cm2 to 8.49 mAh/cm2 with the current density of 0.05 mA/cm2 and the cut off capacity of 1 mAh/cm2.When the current density and the cut off capacity were set to 0.1 mA/cm2 and 0.5 mA/cm2 respectively,the cycle numbers increased from 23 to 52.2、Iodosobenzene(PhIO)was introduced as a liquid phase catalyst for lithium-oxygen battery.And the electrochemical performance has been effectively improved by the electrochemical performance tests.When the current density and the cut off capacity were set to 100 mA/g and 1000 mAh/g respectively,the charge overpotential reduced 460 mV by the PhIO catalyst and the cycle numbers increased from 7 to 42.By exploring the catalytic mechanism,we found that PhIO could promote the rapid transformation of LiO2 into Li2O2,which limited the generation of superoxide related side reactions in the charging and discharging process of the battery,thus contributed to the improvement of the electrochemical performance of the battery.3、Tetraphenyl cyclopentadienone(TPCP)was also introduced as a liquid phase Redox mediators(RM)of lithium-oxygen battery.We found that TPCP could effectively improve the discharge capacity and the rate capability of the battery by the electrochemical performance test.By exploring the catalytic mechanism,we found that TPCP participated in the discharge process with the form of redox intermediates,and the discharge depth of the battery was improved by promoting the growth of solution phase of discharge products,which resulted in the high capacity and high rate capability lithium-oxygen battery.