| With the widely application of all kinds of portable electronic products and the rapid development of hybrid electric vehicles,the efficiency of energy storage devices is required to be much higher.However,due to the impact of cathod and anode materials,lithium ion battery has been unable to meet the commercial needs.Nowadays,lithium-air battery is attracting much more attention,due to its high theoretical energy density and environmental protection.However,if we want to achieve commercial production,there would be a long distance.There are many existing problems that hinder its commercial development,such as large overpotential,low cycling life,poor rate performance,security risks and so on.Therefore,in order to solve these problems,a large number of researchers have been focusing on cathod and anode materials,as well as electrolyte study.There are the following aspects:the protection of lithium metal anode,electrolyte stability,structural characteristics of cathode matrix material and the use of catalysts.In this paper,we concentrate our efforts on the non-aqueous battery system and research on carbon materials with special structure.We use XRD,SEM,TEM and other methods to test its characterization,and study the electrochemical properties of lithium-air battery by charge-discharge test and electrochemical workstation.Firstly,we used carbon nanotubes(CNTs),graphene nanosheet(GNSs)as the cathode material of lithium-air battery,respectively.Experimental results showed that the behavior of GNSs was superior to CNTs,in terms of the first charge-discharge performance and cycling performance.At a current density of 500 mA g-1,the initial charge and discharge capacity was up to 9114 mAh g-1 and 13184 mAh g-1,respectively.When limited the capacity of 1000 mAh g-1,it lasted for 20 cycles without the capacity decay.At a current density of 200 mA g-1,the initial discharge capacity was up to 15638 mAh g-1.While the current density increased to 1000 mA g-1,the initial discharge capacity discreased to 8170 mAh g-1.With the increase of the current density,the discharge capacity was gradually reduced,and the discharge platform appeared the same trend.Therefore,the overpotential was corresponding increased and polarization was aggravated.Ruthenium nanoparticles were loaded on the GNSs via solution method.Then the obtained ruthenium/graphene(Ru/GNSs)composite material was used for the cathode of lithium-air batteries.At a current density of 500 mA g-1,the initial charge and discharge capacity was up to 13136 mAh g-1 and 13578 mAh g-1,respectively.When limited the capacity of 1000 mAh g-1,it lasted for 30 cycles without the capacity decay.The results demonstrated that Ru/GNSs composite significantly increased the catalytic activity of redox reactions,and improved the performance of the electrochemical reaction,compared with the pure graphene.Urea formaldehyde resin microspheres were prepared by precipitation polymerization with urea and formaldehyde.Then the carbonization and activation were carried out to prepare the porous carbon microspheres,which were used as the cathode of lithium-air batteries.We explored its morphology structure with different ratio of urea and formaldehyde,and the concentration of curing agent.When the ratio of urea and formaldehyde was 1:0.8 and the concentration of the curing agent was 0.5 M,we could get carbon microspheres with high sphericity,good monodispersity and relatively uniform particle size.Through the measurement of specific surface area and pore size analysis,the specific surface area of carbon microspheres was 498 m2 g-1,and the total pore volume was 1.9 cm3 g-1.After activating this group carbon microspheres,we get porous activated carbon microspheres,with the specific surface area increasing to 827 m2 g-1.At a current density of 100 mA g-1,the initial charge and discharge capacity was up to 2017 mAh g-1 and 2075 mAh g-1 respectively.When limited the capacity of 500 mAh g-1,it lasted for 15 cycles without the capacity decay. |
PDF Full Text Request