Research On Anode Interface Engineering And Electrochemical Performance Of Lithium Metal Batteries

Lithium metal（LM）is considered as an ideal anode material for lithium-ion batteries（LIBs）due to its high theoretical specific capacity(3860 m Ah g^-1)and ultra-low redox potential（-3.04 V vs.standard hydrogen electrode）.However,LM is characterized by high activity,low surface energy,low surface diffusion coefficient and"host-less"properties,which result in poor electrochemical and mechanical stability.As a result,the repeated plating/stripping of LM during the charge/discharge process of the battery leads to infinite volume expansion and dendrite growth,which may lead to short circuit and safety problems in severe cases,thus greatly hindering the commercialization of lithium metal batteries（LMBs）.The solid electrolyte interface layer（SEI）,as an intermediate phase at the LM/electrolyte interface,is important for the stabilization of LM and has attracted extensive research by scholars in recent years.Therefore,for the interfacial stability of LM anode and its connection with SEI,this paper focuses on both anode current collector and electrolyte engineering to enhance the electrochemical performance of LMBs.Meanwhile,the mechanism of the effect of interfacial engineering on LM stability enhancement is revealed.The specific research contents are as follows.（1）Rapid synthesis of 3D lithiophilic current collectors and their application in LMBs.LM host materials with oxide loading on nickel foam（NF）were successfully synthesized using a fast combustion strategy.Enhancing the lithiophilic property of nickel foam provides additional space for LM deposition and induces uniform LM deposition.The results show that an appropriate amount of lithiophilic material loading is required to achieve efficient LM plating/stripping behavior,while too much or too little lithiophilic material loading will lead to poor mechanical stability of the current collector and poor chemical stability of the SEI.Therefore,a stable Li₂O-rich SEI phase derived based on Co-2@NF,which obtained a stable cycle of 210 cylcles in half-cell,maintained a coulombic efficiency of 97.1%.The symmetric-cell possesses an ultra-low overpotential of 13 m V and an ultra-long lifetime of 2400 h at 0.5m A cm^-2,1 m Ah cm^-2.Meanwhile,the composite anode Co-2@NF@Li was matched with different loadings of lithium iron phosphate（LFP）cathode to obtain super high capacity retention.This study not only proposes a method to stabilize the LM anode,but also provides insights into the interfacial chemistry.（2）Study of Li⁺transport behavior in organic/inorganic composite gel electrolytes and its effect on the interfacial properties of electrodes.Pentaerythritol tetraacrylate（PETEA）was used as a gel electrolyte substrate,and the LM/electrolyte interfacial stability was improved by introducing fumed silica（Si O₂）as a filler in the gel electrolyte.Among them,PETEA possesses a rich polymer porous skeleton structure,which facilitates the transport of Li⁺and provides high mechanical properties to block the growth of dendrites.Si O₂ has a large polarity and optimizes the solvation structure of Li⁺,which induces the generation of anion aggregates（AGGs）and accelerates the reaction kinetics of Li⁺.Therefore,composite gel electrolyte（PS-0.5）based LFP full-cells derived Li F-rich interfacial layers on both sides of the anode/cathode electrode.This study systematically explores the Li⁺solvation structure in the gel electrolyte system and provides a unique perspective on the interfacial engineering of LMBs.（3）Preparation of gel electrolytes with strong electronegative groups and its performance study on high-voltage LMBs.In order to further improve the performance of PETEA-based gel electrolytes,the Terephthalonitrile（DCB）monomer containing strong electronegative cyanide was introduced into the gel polymer electrolyte substrate as additives,which effectively regulated the local electronic environment of the gel electrolyte,boosted oxidative decomposition voltage of electrolyte,and optimized the Li⁺transport performance.The gel electrolyte（PDGPE）is not only suitable for LFP full-cells in ether system,but also achieves long cycle performance of high-voltage Li||LMNO full-cells based on its optimization of the interfacial structure of the anode/cathode of LMBs,and its capacity is maintained at 92.5%after 120 cycles.This study provides an elucidation of the interfacial influence mechanism of PETEA-based gel electrolytes in high-voltage LMBs and provides insight into the further development of high specific energy LMBs.