Modifications Of Electrochemical Interface And Deposition Pattern For Energy-denese Metal Anodes

Battery is one of key energy storage techniques to realize carbon neutrality,and it can collect,store and converse the intermittently supplied clean energy(solar energy,wind energy,tidal energy).Energy-dense metal batteries based on anodic depositing/stripping mechanism can break the energy density bottleneck of state-of-art lithium-ion batteries based on ion intercalation/deintercalation mechanism,which has attracted significant attention from academia,industry and governments.However,the scientific challenges like uneven metal deposits induced battery short-circuits,serious interfacial side reactions,large expansion of anodes,have long plagued the development of metal batteries.This thesis focused on modifications of electrochemical interface and deposition pattern on the anode sides.We studied the effects of interfacial mass transfer,composition of anodic interphase,electrolyte solvation structure and metal deposition mechanism on the performance of energy-dense metal based batteries.The first part of this thesis studied lithium metal anodes from "microscopic mechanism-interconnected relationship-electrochemical performance enhancement"aspects,including the second chapter to the fifth chapter.The failure mechanism of Limetal anodes is a consequence induced by multiple mechanisms,including:interfacial inhomogeneous mass transport of Li+and anion,uncontrollable interfacial side reactions and solid electrolyte interphase(SEI)formation,poor reversibility of Li-metal depositing/stripping and so on.To resolve the above scientific challenges,the research contents in this part include:1.The second chapter solves Li-metal dendrite growths caused by ion concentration gradients under high current densities.During Li-metal deposition process,quaternized polyethylene terephthalate interphase with lithiophilic and anionphilic sites can effectively uniform the cation and anion fluxes at the electrochemical interface,enabling stable Li-metal deposition under high current densities.2.The third chapter explores the effects of interfacial chemical stability on the electrochemical performance of Li-metal anodes.According to the frontier molecular orbital theory,introduction of trifluoromethyl functional groups with strong electron-withdrawing ability to the organic interphase can precisely tune the LUMO energy level(-0.14 eV)and improve the anti-reduction ability and chemical stability against Li-metal anodes.Under the protection of highly stable organic interphases,Li/S battery can cycle more than 300 cycles at a high current density of 3.345 mA cm-2.4.The fifth chapter reveals the relationship between SEI composition,nanostructure and anodic reversibility.Cryo-TEM demonstrated that SEI with high proportion of inorganic nanocrystals can promote grain coarsening of Li-metal deposits.Temperature-dependent electrochemical impedance spectroscopy showed that SEI with fast ion transport properties can cause the growth of large sized Li-metal deposits.Li-metal deposits with low tortuosity and large grain size can maintain the bulk electronic conduction pathways during the stripping process,and improve the anodic metal depositing/stripping reversibility.The second part of this thesis applies the modifications of grain size and deposition morphology to multivalent metal anodes,including the sixth chapter.Metal anodes based on multivalent redox chemistry(such as Zn/Zn2+,Mg/Mg2+,Al/Al3+,etc.)exhibit high theoretical specific capacity and abundant raw material supplies,which is a promising path for have great large-scale and low-cost electricity storage.Similar to Li metal anodes,uneven metal deposition,poor anodic metal reversibility also plague the development of multivalent metal batteries.Multivalent ions have large ionic radius and high charge density,which means it is difficult to design artificial SEI similar to Li-metal anode studies.To resolve the above scientific challenges,the research contents in this part include:5.The sixth chapter proposes a dynamic interphase strategy to facilitate the ordered assembly/disassembly of metal deposits under deep cycling conditions.Two-dimensional graphitized carbon nitride nanosheets with high crystallographic matching with zinc metal can be preferentially adsorbed on(0002)zn facets during the deposition process,intercalated between the aligned zinc platelets,and induce densely packed layered zinc deposits.Under practical test conditions(20 μm thin zinc metal anode,6.3 mAh cm-2 high mass loading cathode),cycling lifespan of the full battery can reach 400 cycles.This dynamic interphase strategy has a wide range of applications,it can also induce densely assembled Mg and Al metal deposition and significantly improve the Coulombic efficiency.In conclusion,this thesis studies the energy-dense metal based batteries enabled by tuning the electrochemical interface and deposition pattern.We try to solve the scientific challenges in metal anodes from interface mass transfer,solvation structure,anode interface chemistry and grain/deposits morphology.This thesis provides a brand-new route for the development of practical,deep cycling and energy-dense metal based batteries.