Lithium-air(Li-air)batteries have recently received much attention due to their extremely high theoretical energy densities.The significantly larger theoretical energy density of Li-air batteries is due to the use of a pure lithium metal anode and the fact that the cathode oxidant,oxygen,is stored externally since it can be readily obtained from the surrounding air.However,before Li-air batteries can be realized as high-performance,commercially viable products there are still numerous scientific and technical challenges that must be overcome,from designing the cathode structure,to optimizing the electrolyte compositions and elucidating the complex chemical reactions that occur during charge and discharge.The scientific obstacles that are related to the performance of Li-air batteries open up an exciting opportunity for researchers from many different backgrounds to utilize their unique knowledge and skills to bridge the knowledge gaps that exist in current research projects.This review article is a summary of the most significant developments and challenges of practical Li-air batteries and the current understanding of their chemistry.
Lei-Lei ZhangZhong-Li WangDan XuXin-Bo ZhangLi-Min Wang
Lithium-air(Li-air) batteries have attracted worldwide attention due to their high energy density(11140 Wh kg-1) comparable to gasoline.In this work,we have synthesized the α-MnO2 hollow clews via a simple method and characterized them by X-ray diffraction and scanning electron microscope.Interestingly,cycle performance of Li-air batteries is improved greatly when using the α-MnO2 hollow clews as the catalyst.The first discharge capacity is 596 mAh g-1,and the charge capacity is 590 mAh g-1 at the current density of 0.1 mA cm-2 between 2.0 and 4.2 V using the Vulcan XC-72 as the carbon material.Additionally,by re-assembling new batteries with the used lithium foil,separators and cathode separately,we find that the cathode is the key role to end the Li-air battery life.
Supercapacitors（SCs） have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and promising material due to its large theoretical specific surface area,high electrical conductivity,good mechanical properties and chemical stability.Herein,we report an effective strategy for elaborately constructing rationally functionalized self-standing graphene（SG） obtained from giant graphene oxide（GGO） paper followed by an ultrarapid thermal-processing.This treatment results in both the exfoliation of graphene sheets and the reduction of GGO by elimination of oxygencontaining groups.The as-prepared SG electrode materials without additive and conducting agent provide an excellent combination of the electrical double layer capacitor（EDLC） and pseudocapacitor（PC） functions and exhibit superior electrochemical performance,including high specific capacitance,good rate capability and excellent cycling stability when investigated in three-electrode electrochemical cells.
