Metal-doped Porous Carbon Nanofibers For The Construction Of Structural High-performance Lithium Metal Anode

With the growing development of modern electronic products,new energy vehicles and large-scale energy storage systems,people have raised higher requirements on the energy density and cycle life of secondary batteries.After more than three decades of development,lithium-ion batteries have almost reached a performance bottleneck and are unable to meet the soaring demand for high energy storage.Lithium metal anode is very attractive due to its low density(0.534 g cm^-3),lowest electrochemical potential（-3.04 V vs standard hydrogen electrode）and high theoretical specific capacity(3860mAh g^-1),and has long been considered as the"Holy Grail"of electrode materials for next-generation lithium batteries.However,a number of serious challenges have severely hampered the commercialized application of lithium metal batteries,such as the growth of lithium dendrites,inherent volume expansion,and low Coulombic efficiency.To solve the above problems in lithium metal batteries,researchers have pioneered several strategies to stabilize lithium metal anodes,including the development of artificial SEI films,the optimization of electrolyte composition,and the structural design of lithium metal anodes.Among them,the structural design of lithium metal anodes is an effective strategy to solve the problem of lithium dendrite growth and volume expansion.Therefore,starting from the structural design of lithium metal anodes,three different metal-doped porous carbon nanostructures were prepared by easy electrospinning technology and high-temperature heat treatment.The main research works are as follows:（1）The porous carbon nanofiber scaffold decorated with iron nanoparticles（PCNF-Fe）was designed using iron acetylacetonate（Fe（C₅H₇O₂）₃）,polyacrylonitrile（PAN）,and polymethyl methacrylate（PMMA）as raw materials,without the need for hazardous atmosphere,expensive catalyst deposition,and additional carbon sources.Notably,the obtained PCNF-Fe can serve as a lithium metal anode host with low lithium deposition overpotential as well as long cycle stability under various current densities.In this case,the host can remain stable after 220 cycles at a current density of 3mA cm^-2,and has a overpotential of only about 23 m V.The porous host structure can accommodate the inherent volume expansion during lithium plating/stripping as well as the transport of lithium ions,thereby improving cycling stability.Density functional theory（DFT）calculations show that carbon nanofibers decorated with Fe nanoparticles are more likely to absorb lithium atoms,resulting in more uniform lithium deposition.（2）The porous carbon nanofiber scaffold decorated with nickel nanoparticles（PCNF-Ni）was designed using nickel acetate tetrahydrate（NiC₄H₆O₄·4H₂O）,PAN,and PMMA as raw materials.The N-doped carbon fibers decorated with nickel nanoparticles can expose more active sites to trap lithium ions,thus improving their lithophilicity.In addition,the 3D porous conductive structure can alleviate the volume expansion variation,and can effectively decrease the local current density to inhibit the formation and generation of lithium dendrites.As a result,the PCNF-Ni host exhibits excellent electrochemical performance.DFT calculations show that carbon nanofibers decorated with nickel nanoparticles have stronger adsorption ability for lithium,resulting in more uniform plating.（3）The porous carbon nanofiber scaffold decorated with FeNi alloy nanoparticles（PCNF-FeNi）was designed using Fe（C₅H₇O₂）₃,NiC₄H₆O₄·4H₂O,PAN,and PMMA as raw materials.The porous structure and the incorporation of FeNi alloy can expose more active sites for lithium nucleation and effectively decrease the nucleation overpotential of lithium metal to guide the uniform deposition of lithium.The 3D structural porous host can provide a rich conductive network as well as a larger specific surface area,which can buffer the inherent volume expansion during cycling and efficiently reduce the local current density,regulating the growth of lithium metal without dendrite problems.The host can achieve stable cycling performance up to 220 cycles at a current density of 3 mA cm^-2,maintaining a low overvoltage.At a current density of 1 mA cm^-2and a deposition capacity of 1 mAh cm^-2,the Coulombic efficiency of the PCNF-FeNi electrode remains around 97%after 300 cycles.This paper can provide a low-cost and scalable strategy for designing 3D structural high-efficiency lithium metal anode hosts,and also provide a certain reference for the flexible design of other metal anodes.