Directly Hybridizing The Molten Lithium And Carbon Nanotubes As Dendritic-free Anodes For Lithium-metal Batteries

Lithium（Li）metal is the most promising for energy storage systems in the next-generation due to its high theoretical specific capacity and low potential.However,its practical application is still hindered by the serious safety issues for the growth of dendritic.Using carbon nanomaterials as conductive matrix for optimizing structure of Li electrodes is a promising method to solve the problem.However,the carbon nanomaterials including carbon nanotubes（CNTs）cannot be wetted by molten Li.This is the most difficult problem to construct Li/carbon hybrid anode.This study proposed a dendrite-free Li/CNTs hybrid,which is fabricated by direct coating molten Li on CNTs for the first time.The favorable thermodynamic and kinetic conditions are the powerful force to drive the rapid lift upwards and infusion of molten Li into CNTs network.The direct hybridization of molten Li with CNTs can disperse current density effectively.Hence,Li⁺are deposited uniformly which inhibits the formation of dendritic Li and ensures the security of Li-metal batteries.（1）Carbon nanotubes sponge macrofilm（CSMF）/Li-metal hybrid has been prepared directly through thermal infusion.The large contact angle was shown when the molten Li droplet was placed on the surface of CSMF.The results indicated that molten Li has poor infiltration to the CNTs.In this study,a“sandwich”structure of CSMFⅠ-Li-CSMFⅡwas placed under the appropriate temperature conditions.Liquid Li can be soaked into the CSMF along CNTs bundles directly.By testing the temperatures each interfaces of CSMF,the thermodynamic trend was discussed.There was a negative Gibbs free energy for molten Li in the upper CSMF due to undercooling.The driving force comes from the pressure difference generated by the pressure change in CSMF.It happened that the solidification and growth of molten Li along the CNTs bundles to achieve infiltration.The Li/CNTs hybrid（Li CSMF）was finally obtained.（2）The symmetric batteries with Li CSMF as anodes were not only stable at the common current density of 2 m A cm^-2,but also could maintain stable with over-potential below 50 m V even at an ultra-high current density of 40 m A cm^-2 for 2000 cycles.It also indicated the Li CSMF hybrid could disperse current density effectively.The Li CSMF base battery also could realize stable coulombic efficiency through cycling Li/Cu half-cell at a high current density of 10 m A cm^-2 for 300 cycles.With different cycle number and stripping/plating capacity,it displayed flat surface of Li CSMF anode while large number of dendrites can be found in Li foil.It showed that the uneven deposition/stripping of Li⁺led to the growth of dendritic Li.While Li CSMF hybrids can inhibite the formation of dendritic Li and dead Li owing to the Li⁺uniformly stripping and deposition on CNTs.Finally,the distribution of the current density and Li morphology evolution in the interface of the electrode are also performed by COMSOL Multiphysics.