| Lithium metal is deemed as an ideal anode material for next generation lithium ion batteries（LIBs）due to its high theoretical capacity(3,860 m Ah g-1)and lowest electrochemical potential（-3.04 V vs.the standard hydrogen electrode）.However,uncontrolled lithium dendrite formation during electrochemical deposition leads to a low Coulombic efficiency and serious safety issues,dragging metallic lithium anodes out of practical application.One of the promising strategies to suppress lithium dendrite issues is employing a three-dimensional host with admirable conductivity and large specific surface area.Herein,a vertical graphene nanosheet grown on carbon cloth（VG/CC）synthesized is adopted as the Li deposition host and the morphology and structure of which are characterized.A half-cell is assembled where the prepared materials and lithium foil are used as the working and counter electrode to describe in detail the insertion and extraction of Li+during lithium plating/stripping.At the same time,electrochemical tests are carried out at various current densities.The specific experimental contents are as follows:Firstly,vertical graphene nanosheets are grown on the carbon cloth by plasma-enhanced chemical vapor deposition（PECVD）as Li host.Three-dimensional VG/CC with a large surface area can provide abundant active nucleation sites and effectively reduce the current density,leading to homogeneous Li deposition to overcome dendrite issue.At the same time,carbon cloth exhibits excellent flexibility and high electrical conductivity in spaces.Especially,it can maintain complete three-dimensional structure after a long-term cycle and the growth space is limited to the network structure which effectively relieves the volume expansion during repeated charge and discharge.The plating/stripping process is carried out at a fixed capacity of 1 m Ah cm-2 and a current density of 1 m A cm-2.Lithium metal is uniformly deposited inside the pores of VG,with a flat surface without dendrite.When the lithium is stripped,the structure of VG is exposed again,indicating good reversibility.When the capacity is 1 m Ah cm-2 and the current density is 1 m A cm-2and 2 m A cm-2,respectively,the Coulombic efficiency can be stabilized at 99%.Moreover,the Coulombic efficiency can reach 97%at a current density of 1 m A cm-2with the capacity of 2 m Ah cm-2 over 100 cycles.In addition,the Li@VG/CC anode exhibits a dendrite-free morphology after long cycle and superior electrochemical performance than that of planar Cu current collector.It delivers a small voltage hysteresis of 90.9 m V at a high current density of 10 m A cm-2.In order to explore the practical application,a full battery composed of Li@VG/CC as the anode and Li Co O2（LCO）as the cathode exhibits a capacity of 133 m Ah g-1 at 0.2 C.In addition,a layer of gold nanoparticles are deposited on graphene nanosheets（Au-VG/CC）by thermal evaporation on VG/CC to further improve the electrochemical performance of lithium metal anodes.According to the different of lithium metal heterogeneous nucleation overpotential,the smaller the overpotential,the lithium metal is deposited more uniformly.Gold nanoparticles can effectively reduce the nucleation overpotential of lithium metal,guide the uniform deposition of lithium metal,and reduce the formation of dendrites.The Au-VG/CC surface exhibits smooth and flat deposit morphology during lithium plating/stripping,without the growth of lithium dendrites.It delivers a small voltage hysteresis 67.2 m V at a high current density of 5 m A cm-2 with the capacity of 5 m Ah cm-2 and stably cycle over200 hours.Our results show that a three-dimensional carbon-based lithium metal anode can achieve a controllable dendrite-free morphology.This all-carbon-based nanostructure host has great potential for next-generation lithium metal batteries. |
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