| The rapidly increased demand for highly performing energy storage devices for energy storage and electric vehicles etc.,have driven the development of the energy storage systems with develop low-cost,environmental friendliness and high energy density.Recently,lithium-air battery attracted much attention due to its high theoretical energy density of 11,400 Wh kg-1,which is significantly higher than that of commercial Li-ion battery.However,Li-air batteries with lithium metal as anode usually undergo serious safety hazards in practical application.Generally,the high reactivity of Li anode toward liquid electrolytes causes uncontrollable dendrites growth,recurrent solid electrolyte interphase（SEI）formation and relatively infinite volume change,leading to very poor cycling performance and lifespan,which hinders the practical application of Li-air battery.Therefore,in order to effectively solve the above problems,this paper explores the high energy density Li-air battery from the three-dimensional Li matrix structure design and the infusion strategy of molten Li.The main research results are as follows:（1）Li metal anode faces uncontrollable dendrite growth and volume change during the process of repeated plating/stripping,resulting in the continuous formation/rupture of solid electrolyte interphase（SEI）,low coulomb efficiency,capacity attenuation,and ultimately leads to the risk of short circuit and even explosion of Li-air battery.Therefore,N,P co-doping carbon nanofibers（NPC）coated carbon cloth（NPC-CC）is successfully prepared through electro-polymerization and subsequent carbonization.The as-prepared NPC-CC is modified with Mn O2nanosheet by electrodeposition and further react with molten Li to construct Li-based Mn coated NPC-CC（Li-Mn@NPC-CC）for the first time.Moreover,we also have applied experiment and theoretical calculation/simulation to clarify the liphophilic mechanism of the Li-Mn@NPC-CC electrode:the synergy between NPC and Mn-based species significantly facilitates the reaction rate of molten Li with Mn O2@NPC-CC framework and also effectively improves liphophilicity of Li-Mn@NPC-CC to inhibits dendrite/pulverization over cycles by guiding even Li deposition and stable SEI generation.Additionally,the porous/stable carbon matrix with good conductivity not only effectively buffers electrode dimension variation to improve the structural stability over infusion and subsequent cycling processes,but also provides abundant space to store Li and accelerate ion/electron transfer during battery operation.Hence,symmetrical cells based on Li-Mn@NPC-CC electrodes have long cycle life and low voltage.When Li-Mn@NPC-CC electrode is further coupled with air cathode,the corresponding full cells also display outstanding cycling performances than the corresponding bare Li-based batteries.（2）It is found that Au clusters（CAu）can effectively induce the orientation of Li during the stripping/deposition process.Therefore,a kind of Au cluster-based nanoparticles（CAu-CC）was successfully prepared on carbon cloth and used as a pre-storage matrix（Li@CAu-CC）for Li metal composite anode.Due to the lipophilicity of CAu,Li wettability of CC can be significantly improved to ensure the rapid infusion of molten Li.In particular,the CAu-CC abates the dendritic formation and volume variation due to its lithiophilic property,three-dimensional（3-D）structure,and excellent conductivity guiding the Li-ion deposition and stripping uniformly during cycling.These results show that Li@CAu-CC composite anode has good electrochemical performance,low overpotential,long cycle life and high coulomb efficiency.When paired with air or hard carbon（HC）cathodes,the Li@CAu-CC battery exhibits high specific capacity,excellent cycle stability and rate performance.（3）Moreover,due to the open structure of Li–air batteries,the commercial liquid organic electrolytes easily lead to severe leakage/volatilization issues and also cannot effectively protect Li anode.Therefore,The obtained Au/NNS-NF and Li@Au/NNS-NF are applied as cathode and anode for quasi-symmetric Li–air batteries respectively,in which poly（methyl methacrylate）based composite is used as electrolyte.The highly porous,lithiophilic and stable skeleton of Li@Au/NNS-NF anode greatly inhibit huge electrode variation and also promote the uniform Li deposition to reduce Li dendrites during cycling.Hence,Li@Au/NNS-NF based symmetric battery exhibits stable discharge/charge curves with very low overpotentials of～20 m V over long-term cycling（2200 h）at 1 m A cm-2.Conductive and porous of the Au/NNS-NF cathode not only provide enough space to store discharge product and promote transfer of electron/ion and O2for revesible cathode reaction,but also obviously reduce side reaction in Li–air batteries due to its uniform Au coating.Moreover,the PMMA-based electrolyte has the high ionic conductivity(0.89 m S cm-1),good anti-leakage/stability and excellent protective effect for anodes.As a result,the quasi-symmetric Au/NNS-NF-based Li–air battery using PMMA-based polymer electrolyte shows super-high discharge capacity at 500 m A g-1and also can achieve long cycling life（150 cycles）with low voltage polarization of<2 V.More interestingly,the corresponding quasi-symmetric Li–air soft-package cells show the good electrochemical performances and also power a series of electronic devices,implying their potential application. |
