Study On Carbon Nanocoils @ Carbon Nanotubes For Lithium Metal Anode Host

Lithium metal is considered as one of the most potential anode materials of the next-generation lithium batteries due to its high specific capacity and low electrochemical potential.However,the volume expansion of the hostless 2D lithium sheet anode during charging and discharging,and the growth of lithium dendrites are key issues affecting battery performance and safety.3D carbon-based materials are the key structural materials to solve the above problems owing to their light weight,stable electrochemical properties,good electrical conductivity and high specific surface area.Typical representatives are carbon nanotubes（CNTs）and graphene-based 3D structures,however,their severe agglomeration and stacking problems limit their advantages.Therefore,in this paper,spiral carbon nanocoils（CNCs）with excellent dispersion are inserted into CNT clusters to form 3D CNC@CNT structure,thus solving the agglomeration problem of CNTs and enabling it to give full play to the advantages of high specific surface area.At the same time,the insertion of CNCs can ensure the high porosity of the structure,provide fast transport paths and sufficient deposition space for lithium ions,improve the deposition behavior of lithium,and inhibit the formation of lithium dendrites.In addition,the super-elastic property of CNC can alleviate the volume expansion of the electrode after many cycles.The details are as follows:In this study,CNT and CNC were homogeneously mixed,and then porous CNC@CNT film was fabricated by a simple vacuum filtration process.The introduction of CNC increased the specific surface area of CNT from 154.8 m² g^-1 to 258 m² g^-1,which significantly improves the specific surface area of the electrode.Meanwhile,the existence of spiral central pore in CNC makes the 3D structure with high porosity of 65%,which enables faster ion diffusion behavior of lithium ions in CNC@CNT electrode and provides abundant deposition space.The electrode achieves flat and uniform lithium deposition at a current density of 0.5 mA cm^-2without dendrite formation.Moreover,the CNC of super-elastomer enables the whole electrode structure to release part of the stress during cycling,and the volume expansion is only 10.7%after 50 cycles of lithium deposition/stripping process,which ensures the stability of the electrode structure.The good lithophilicity of this electrode allowed the half-cell to exhibit a low overpotential of 11.8 m V at 0.5 m A cm^-2 and an average coulombic efficiency of 97.3%after nearly 200 long cycles.The full battery fabricated with CNC@CNT electrode delivered a specific capacity of142.12 m Ah g^-1 at 0.5C,the good dynamic behavior of lithium ion in the electrode structure made it play a good electrochemical performance better than CNT and copper foil electrode at different high rates,showing small cell polarization.It can still have a high capacity retention rate of 96.8%after 100 long-time cycle tests at 1C rate,and the electrode structure has good stability.