Design And Electrochemical Performance Of 3D Current Collector Host Material For Lithium Metal Anode

Lithium metal batteries（LMBs）have the advantages of high energy density and simple processing technology,and are considered to be the key technology to further improve the energy density of energy storage,reduce the weight of equipment,and solve the range anxiety of electric vehicles.However,the volume of lithium metal anodes changes greatly during the charge and discharge process,resulting in continuous consumption of electrolyte,which in turn affects the cycle life.The uneven deposition/stripping of lithium metal can easily lead to the formation and growth of lithium dendrites and the formation of"dead lithium"（electrically inert lithium）.Lithium dendrites piercing the separator can also cause safety problems such as thermal runaway and explosion,which seriously restrict the practical application of LMBs.The three-dimensional structure design or the construction of the lithiophilic layer can effectively suppress the volume change and lithium dendrites.Based on this,starting from the nickel foam（NF）current collector,this thesis explores the methods to improve the uniformity and reaction kinetics of lithium metal deposition/stripping through two strategies of structural design and construction of porous lithiophilic layer.It provides a reference for the design of high-safety and long-life lithium metal batteries.The specific content is as follows:A nanosheet array with a porous surface structure（PNA@NF）was designed and fabricated as a negative current collector material for LMBs.The results show that the constructed porous Ni arrays improve the reversibility of lithium deposition and stripping.The assembled half-cells can be cycled stably for more than 300 cycles at0.5 m A cm^-2,and have an average Coulombic efficiency（CE）of more than 98%.Tests show that the reason for its performance improvement may be that the continuous distribution of pores on the surface can effectively increase the specific surface area of the array structure,make Li⁺evenly distributed on the negative electrode surface and reduce the surface current density,thereby inducing uniform lithium deposition.Therefore,the negative electrode has smaller volume change,higher lithium storage capacity and more stable interface properties during cycling.However,due to the inherent poor lithiophilicity of metal Ni itself,PNA@NF still leads to intensive nucleation of lithium during cycling,leading to a decrease in cycle performance.In order to solve the inherent poor lithiophilicity of PNA@NF materials,a porous Ni Zn lithiophilic alloy layer（P-Ni Zn@NF）was fabricated on the surface of NF to be used as the anode current collector of LMBs.The results show that the current collector exhibits a more uniform lithium deposition morphology.Benefiting from the lithiophilic layer,the fabricated symmetric battery exhibits low overpotential（～15 m V）and ultra-long cycle life（over 2500 h）.The full cell assembled with Li Fe PO₄（LFP）cathode exhibits excellent CE（99.98%after 600 cycles）and high capacity retention（86%）.Tests show that the reason for its improved performance may be that the lithium-friendly Ni Zn alloy effectively reduces the overpotential of lithium deposition and alleviates the side reaction between the lithium anode and the electrolyte.The uniformly distributed pore structure can effectively reduce the local current density on the electrode surface and play a role in regulating the Li⁺flux,which solves the uniform lithium deposition/stripping of the electrode throughout the charging and discharging process.