Design Of Structured Anode For Lithium Metal Battery And Its Electrochemical Performance

Driven by the rapid development of electric vehicles,high-energy-density rechargeable batteries have received increasing attention and are being widely pursued.In the past,lithium-ion batteries have been used in many electronic products such as mobile phones and computers.However,for electric vehicles,the energy density of currently commercially available batteries is 200Wh/kg,which is far from the requirements of endurance.Therefore,it is necessary to develop batteries with higher energy density.Among all available anode materials,lithium（Li）metal is widely considered as ideal anode due to its extremely high theoretical specific capacity（3860m A hg-1）and low reduction potential（-3.04 V compared to a standard hydrogen electrode）.However,there are still many problems in the practical application of lithium metal anodes.First,the uneven deposition of lithium can lead to the formation of lithium dendrites,which can cause internal short circuits and potential safety hazards.In addition,lithium metal also undergoes a series of complex reactions with the electrolyte to form an unstable SEI film,causing the battery internal resistance to increase,forming"dead lithium",and greatly reducing the coulombic efficiency of the battery.At the same time,the"hostless"nature of lithium metal anodes can lead to infinite volume changes during repeated lithium plating/stripping processes.The construction of structured lithium anode can guide the uniform plating/stripping of lithium,buffer the volume expansion of lithium,and reduce the formation of unstable SEI film.Thus,the formation of lithium dendrites and dead lithium are avoided,and the safety performance and service life of the battery are improved.Based on this research idea,the following research works are mainly carried out in this article.（1）In this paper,the interconnected and closed hollow graphene spheres with an internal load of lithiophilic Li_4.4Sn nanoparticles(Li_4.4Sn/SG)was prepared to improve Li deposition behavior.Both the density functional theory calculations and experimental studies indicate that Li_4.4Sn has higher binding energy and lower nucleation overpotential toward Li than graphene,thus guiding the deposition of Li metal inside the hollow graphene spheres to avoid the generation of uncontrolled Li dendrites and formation of solid electrolyte interface（SEI）on the fresh Li surface.Furthermore,the surface of the non-tip graphene spheres can greatly avoid the uneven distribution of charge caused by the tip effect,so as to continuously guide the uniform deposition of Li on the surface of the spheres after the spheres are completely filled with Li,thus achieving a dense Li metal layer free of dendrites.In consequence,the Li_4.4Sn/SG electrode exhibits a long lifespan up to 1000 hours and an exceptionally low overpotential（<18 m V）.It is believed that the design of the closed hollow spherical structure with lithiophilic nanoparticle seeds inside is a promising strategy to construct high performance Li metal anodes for lithium batteries.（2）Due to the uneven nucleation process,lithium dendrites will be formed during the plating/stripping process.In this work,atomic layer deposition（ALD）technology was successfully applied to construct a stable and thin layer of Zn O coating on the surface of Cu Foam to enhance the lithiophilic of the composite lithium anode.The lithiophilic Zn O nanoparticles can guide Li to nucleate/grow uniformly along the surface of the three-dimensional skeleton,inhibit the formation of Li dendrites,and the porous structure of the rich copper foam can effectively suppress the volume expansion during long cycle.The Li-Zn alloy formed after the initial discharge can greatly reduce the nucleation barrier of Lithium.Benefiting from these advantages,a high and stable coulombic efficiency（98%）was obtained in 150 turns,with an ultra-low nucleation barrier of 10 m V at 1 m A cm^-2.Moreover,the Zn O/CF-Li composite anode can work for more than 300 turns even at 5 m A cm^-2.The full battery uses Li Fe PO₄ as the positive electrode with enhanced cycling stability（100 cycles at 0.2C）and rate performance（140 m Ah g-1 capacity at 2 C）,showing the potential superiority of three-dimensional lithiophilic porous material as a high-performance lithium metal anode framework...