Preparation And Properties Of Non-carbon Based Oxygen Electrode For Secondary Lithium Oxygen Battery

Secondary lithium oxygen battery has attracted extensive attention owing to its high theoretical specific capacity(3860mAh g-1)and energy density(11425 Wh kg-1),which demonstrate promising application in electric vehicles,military aviation and other fields.Lithium air battery has been regarded as one of the best energy storage devices among the beyond-lithium-ion batteries.However,there are still a lot of hurdles before it achieves the practical application.The large charge and discharge overpotential lead to poor cycle life and rate performance.To enhance the catalytic activities of the oxygen electrode catalyst is the key to conquer those challenges.Additionally,the side reactions and the resulting insulation side products is another reason for the poor electrochemical performance of the lithium oxygen battery.In this work,a non-carbon based Ru/B4C catalyst was prepared by hydrothermal method,and its electro-catalytic activities were systematically studied.Ru/B4C catalyst can not only achieve high activities for oxygen reduction(ORR)and oxygen precipitation(OER)reactions but also demonstrate the effective decomposition of side products of Li2CO3 and LiOH.The charge tests of Li2CO3-and LiOH-preloaded cells indicate that Ru/B4C can completely decompose Li2CO3 and LiOH at 3.97V and 4.1V,respectively.Lithium oxygen batteries using RU/B4C oxygen electrode exhibits discharge capacity of 2951 mAh g-1 in the first discharge process at 0.05mA cm-2.Under the controlled capacity of 300mAh g-1 the battery can run for 40 discharge/charge cycles.The discharge voltage plateau is 2.8V during the first discharge and the ending voltage in the first charge is only 3.6V,indicating that Ru/B4C catalyst can significantly reduce the discharge and charge overpotential and alleviate the impact of side reactions incurred by the decomposition of electrolyte.Finally,the electrochemical performance of lithium oxygen battery using Ru/B4C oxygen electrode was also investigated in dried ambient air within the voltage range of 2.0V-4.37V and at the current density of 0.1mA cm-2,0.2mA cm-2,0.3mA cm-2 and 0.5mA cm-2,respectively.The corresponding capacity in the first discharge was 2260.9mAh g-1 1764.5mAh g-1,1309.1mAh g-1 and381.2mAh g-1,respectively.Under the limited capacity of 300mAh g-1 the lithium oxygen battery achieved 45 cycles,34 cycles and 22 cycles at 0.1mA cm-2,0.2mA cm-2 and 0.3mA cm-2,respectively.The results show that Ru/B4C is a very promising non-carbon based oxygen electrode material for secondary lithium oxygen batteries,especially for the use in ambient air.