Salt Template Assisted Controllable Preparation Of 3D Porous Lithium Metal Anodes Material And Their Energy Storage Mechanisms

Lithium has the lowest metal density(0.534g cm^-3),the most negative electrochemical potential（-3.04 V vs standard hydrogen electrode）and the extremely high theoretical specific capacity(3860 mAh g^-1),which is considered to be the most Ideal secondary battery anode material.However,the problem of dendrite growth and infinite volume expansion during the cycle of lithium metal anodes hinders its practical application.Dendritic growth is related to the non-uniformity of the solid electrolyte membrane（SEI）,the unevenness of charge distribution,and the non-uniformity of lithium ion flux.In addition,the large volume fluctuation of the lithium metal anode during the plating/stripping process destroys the stability of the SEI.These can cause a decrease in the coulombic efficiency of the battery and a safety hazard.Therefore,it is very important to achieve uniform deposition of lithium metal and to suppress volume change of lithium metal during cycle.In response to these problems,the mechanism of uniform deposition of lithium metal was studied by modifying the three-dimensional porous carbon current collector.Firstly,ZnO nanoparticles confined 3D porous carbon composite microspheres（3D ZnO@PCCMs）were prepared by chemical vapor deposition（CVD）using NaCl as a template.The optimal formation conditions and formation mechanism of the composite materials have been studied,and the reason for improving the electrochemical performance of the lithium metal anode has also been explored.the result shows that since ZnO can be infinite solubile in lithium metal to form a solid solution.It can reduce the interfacial energy between the lithium metal and the current collector and improve the lithiophilic of the current collector.In addition,this work utilizes ultra-thin carbon stabilized ZnO nucleation seeds.The uniformly distributed ZnO acts as an induced seed of lithium metal to achieve uniform deposition of lithium metal and no dendrite growth.In the Coulomb efficiency test,It can be fairly stable at98.5%for nearly 250 cycles at a current density of 1.0 mA cm^-2 under the areal capacity of 2.0 mAh cm^-2.In the symmetrical battery test,It could achieve very stable voltage profile with a ultralow overpotential of only 9 m V and an ultralong lifespan of 1000 h.Secondly,MoS₂ Anchored on 3D Graphene Networks composites（MoS₂@3DG）were prepared by chemical vapor deposition（CVD）using NaCl as a template.The optimal formation conditions and formation mechanism of the composite materials have been studied,and the reason for improving the electrochemical performance of the lithium metal anode has also been explored.the result shows that the high specific surface area of 3DG can reduce the local current density and facilitate the uniform deposition of lithium metal.The high-purity,high-crystalline MoS₂ nanosheet not only stabilizes the current collector structure,but also promotes the rapid transport of lithium ions and improves the lithiophilic of the current collector.At the same time,the rich pore structure can effectively store lithium and inhibit the volume fluctuation during the cycle.These indicate that the MoS₂@3DG can be used as a lithium metal deposition framework to achieve controlled deposition of high-capacity lithium metal.In the Coulomb efficiency test,It can fairly stable at 98.5%for nearly 400 cycles at a current density of 2.0 mA cm^-2 under the areal capacity of 2.0 mAh cm^-2.In the full battery test,the capacity of 125 mAh g^-1 can be achieved at a rate of 5C.