Preparation And Electrochemical Stability Of Copper-based Modification Layer Of Lithium Metal Anode

The swift progression of science and technology,coupled with the increasing needs of people’s daily life,has highlighted the significance of advanced lithium battery systems featuring high energy density.Lithium（Li）metal has long been regarded as the most promising anode material for next-generation rechargeable batteries due to its low redox potential and superior theoretical capacity.However,the high nucleation barrier of Li on Cu current collectors has presented a challenge in achieving Li nucleation with high coverage.In addition,the uneven Li deposition/stripping can lead to the formation of"Li dendrites"and"dead Li",resulting in poor cyclic stability the Li metal anode.The inadequate cyclic stability has hindered its practical application.To address this issue,a new method involving the in-situ synthesis of a lithiophilic modification layer on a Cu foam current collector has been proposed to enhance the electrochemical stability of Li anodes.The introduction of a modification layer reduces the local current density during Li deposition and the Li nucleation barrier,leading to a high coverage of Li nucleation.Additionally,the Li⁺diffusion behavior between electrode/electrolyte interfaces can be rationally regulated,resulting in uniform Li deposition/stripping reaction.As a result,an enhanced cyclic stability of the Li metal anode can be achieved.Theoretical and experimental efforts have been exerted to discover the electrochemical lithiation behaviors and products of the as-prepared lithiophilic modification layer,as well as its regulation mechanism for Li deposition.Ultimately,a highly stable Li anode with a long lifespan can be realized.A method of in situ preparation of a Cu-based Prussian blue analogue（CuFePBA）film on Cu foam was proposed,and the mechanism of regulating Li deposition and stabilizing Li anode was revealed.The resulting CuFePBA film exhibits a unique honeycomb-like nanostructure that reduces the local current density and homogenizes the electric field distribution,and guides the uniform deposition of Li.The crystal structure of CuFePBA also allows for Li⁺insertion,which provides chemical lithiophilic properties and reduces the Li nucleation barrier,thereby improving the Li nucleation coverage.Oxygen doping was introduced into the CuFePBA film by annealing under air,which further reduce the Li nucleation barrier.In a Li//Cu half cell,the Li anode based on the oxygen-doped CuFePBA film was able to undergo stable Li plating/stripping cycles for 700 hours（350 cycles）at a current density of 1m A/cm² and a cyclic capacity of 1 m Ah/cm²,with an average Coulomb efficiency（CE）of 98.2%.Besides,the cyclic lifespan of the Li//Li symmetrical cell（10m Ah/cm²）under the same cycling conditions was found to be more than 1800 hours（900 cycles）.Utilizing the strong lithiophilic effect of oxygen,a new strategy involving the use of a nanocrystalline（NC）-Cu₂O lithiophilic modification layer to enhance the solid electrolyte interface（SEI）was designed,which regulates Li deposition reaction and enhances the cyclic stability of Li anode.Based on the reaction mechanism of Cu₂O and Li,it was hypothesized that the NC-Cu₂O film could be converted to a derived SEI.This hypothesis was verified through the characterization of the electrochemical lithiation products of the NC-Cu₂O film and the Li⁺mass transportation overpotential of the Li anode.The NC-Cu₂O film was found to be easily lithiated,forming an amorphous Li₂O/NC-Cu composite layer that can participate in the SEI structure.In comparison to the organic-rich SEI with low Young’s modulus formed from electrolyte decomposition,the Li₂O derived from the NC-Cu₂O film exhibits a higher Young’s modulus and mechanical strength,as well as a lower Li⁺diffusion impedance,which can inhibit the formation of Li dendrites.As a result,the Li metal anode based on the NC-Cu₂O film was able to undergo stable Li plating/stripping cycles for 500 hours（250 cycles）at 1 m A/cm² and 1 m Ah/cm² in a Li//Cu half cell,with an average Coulomb efficiency of 99.1%.The cyclic lifespan of the Li//Li symmetrical cell（10 m Ah/cm²）under the same cycling conditions was found to be more than 3000 hours（1500 cycles）Due to the undesired Li deposition morphology stability under large capacity conditions,a strategy involving converting microcrystalline（MC）-Cu₂O lithiophilic modification layer into an intermediate lithiation phase to enhance Li adsorption.The MC-Cu₂O film,prepared by thermal oxidation method,has a long Li⁺diffusion path and limited lithiation degrees,and it can be converted into intermediate lithiation phase of Li Cu O.First-principles calculation results indicate that the Li Cu O phase possesses a strong Li adsorption effect,significantly reducing the Li nucleation barrier.Electrochemical measurements also show that the lithiation product of MC-Cu₂O film exhibits conversion Li storage activity at positive potential,with a high capacity of around 0.6 m Ah/cm² and excellent reversibility.Therefore,the cyclic stability of the composite Li anode can be enhanced through cooperative Li storage.As a result,the obtained composite Li anode was able to undergo stable Li plating/stripping cycles for 1600 hours（800 cycles）at 1 m A/cm² and 1 m Ah/cm² in a Li//Cu half cell,with an average Coulomb efficiency of 99.28%.In order to further enhance the stability of the Li anode during large capacity and high rates,a strategy was proposed to stabilize the stability of the Li anode by introducing“solid solution/conversion”reaction to regulate the Li deposition reaction mechanism.The Ag/MC-Cu₂O composite lithiophilic modification layer was constructed by evaporation of nano-Ag coating on MC-Cu₂O films.The nano-Ag film in the composite lithiophilic modification layer can lead to a Li Ag single-phase solution reaction,thereby reducing the stress and structural change of the Li anode during charging and discharging.The Li Ag solid solution reaction can also eliminate the Li nucleation barrier and maintain a more uniform and compact surface morphology in the Li anode.Electrochemical kinetics analysis shows that the Ag/MC-Cu₂O significantly reduced the Li⁺diffusion mass transfer impedance and charge transfer impedance as well as relevant activation energy,providing a basis for the stability of the Li anode at charging/discharging with large capacity and high rates.The resulting composite Li anode was able to cycle stably under high volume/high rate test conditions of 5 m A/cm² and 5 m Ah/cm²,with an average Coulomb efficiency of 98.6%.In a Li//Li symmetrical cell,the cyclic lifespan of the composite Li anode（10 m Ah/cm²）at 1 m A/cm² and 1 m Ah/cm² was found to be more than 3600 hours（1800 cycles）.