Design,Synthesis And Performance Of Carbon Nanofiber-Based Current Collector For Lithium Metal Anodes

Lithium metal has become a research hotspot because of its high theoretical specific capacity(3860 mA h g^-1)and low electrochemical potential?-3.04 V vs SHE?,and is considered to be the most promising anode material for next-generation rechargeable batteries.However,the problems of reaction between highly active metallic Li and electrolyte,infinite volume change during cycling,Li dendrite generation and growth and their related poor cycling coulombic efficiency,stability and safety issues have greatly hindered the practical application of Li metal anode.Recently,progresses have been made through the modifications of electrolyte,separator,Li metal anode itself and the current collector.In this article,modifications on current collector were applied to enhance the performance of Li metal anode:?1?Using polyacrylonitrile as the raw material,a light weight and high nitrogen-doping 3D conductive carbon nanofiber matrix?NCNF?was prepared by electrospinning,pre-oxidation and thermal treatment.A light weight matrix could maintain the high specific capacity nature of Li metal anode.High specific surface area and 3D structure were helpful to lower the local current density and accommodate the volume changes during cycling,maintaining the structural integrity.High nitrogen-doping guaranteed sufficient low nucleation overpotential sites on the large surface of the NCNF.When applied as current collector,it exhibited lower polarization and reduced nucleation overpotential and mass transfer overpotential,suppressing the generation and growth of Li dendrites.Excellent cycling stability with a high coulombic efficiency over 98%for more than 250 cycles was achieved.Moreover,when paired with LiFePO₄ to assemble full cell,the NCNF exhibited reduced voltage polarization and high capacity retention of 82.4%after 300 cycles,demonstrating its feasibility as the anode.The influence of nitrogen-doping content was also investigated.A low nitrogen-doping sample was prepared and although it had larger specific surface area and superior electrical conductivity which were beneficial for dendrite-free morphology,the low nitrogen-doping made it unable to provide sufficient low nucleation overpotential sites on the large surface.The deposited Li metal was unevenly distributed on the surface of the low nitrogen-doping carbon framework,promoting the reaction between metallic Li and electrolyte and generation of‘dead Li'during stripping process,causing a low coulombic efficiency.?2?Using polyacrylonitrile and metal organic framework ZIF-8 as the raw material,hollow particle-based nitrogen-doped carbon nanofibers?HPNCNF?was fabricated.High nitrogen-doping guaranteed the lithiophilic nature of HPNCNF.Its hollow particle-based structure could improve the electric field distribution and Li⁺flux near the surface of the HPNCNF.Combined with its advantages of large surface area and 3D structure,it could help regulate the Li deposition behavior,suppressing the generation and growth of Li dendrites.When used as current collector,it exhibited excellent cycling stability with a high coulombic efficiency over 95% for 280 cycles.