Design And Electrochemical Research Of Zinc Anode Interface For Aqueous Zinc-ion Battery

With the development of society,the depletion of non-renewable energy resources and the serious problem of air pollution have garnered significant attention.The development of renewable energy sources such as wind and solar power has become a primary strategy to address these issues.However,the intermittent and fluctuating nature of such energy sources,influenced by environmental factors,hinders substantial development.Therefore,there is an urgent need for a reliable energy storage system to store and release energy when needed.Aqueous zinc-ion batteries,due to their excellent energy storage characteristics and resource advantages,have become the most extensively researched negative electrode materials for such batteries.Consequently,they emerge as ideal candidates for both small-scale and large-scale stationary grid storage.In weakly acidic electrolytes（p H=4-6）,metallic zinc undergoes spontaneous corrosion by the electrolyte,resulting in continuous evolution of hydrogen gas,which leads to irreversible loss of zinc metal and expansion of the battery volume.Concurrently,the evolution of hydrogen gas is accompanied by the accumulation of hydroxide ions,and the reaction with zinc sulfate electrolyte generates insulating by-products such as zinc hydroxysulfate,causing an increase in the internal resistance of the battery and an elevation of polarization voltage,resulting in sluggish kinetics.On the other hand,due to the uneven distribution of electric field at the interface and untimely replenishment of zinc ions,uneven deposition of metallic zinc occurs,leading to the formation of zinc dendrites that can pierce the separator and cause short circuits in the battery.All these issues impact the cycling stability and lifespan of the battery.This study addresses key scientific challenges such as hydrogen evolution,corrosion,by-products,and zinc dendrite formation at the zinc metal negative electrode.Four different functional organic-inorganic artificial protective layers were prepared,including organic component to prevent corrosion of the electrode by active water,accelerate the desolvation process of zinc ions at the interface,and a composite of different functional properties of zincophilic inorganic layer to collectively promote uniform deposition of zinc ions.A detailed analysis was conducted on the mechanisms of different organic-inorganic artificial interface protective layers for promoting uniform zinc deposition,effectively inhibiting interface corrosion and by-product generation.Finally,symmetrical cells,asymmetrical cells and full cells were assembled using the synthesized interface protective layers to verify the overall enhancement of the performance of cells.The practical potential of the artificial interface protective layers was evaluated by controlling high depth of discharge（DOD）and low N:P ratios in batteries.The main research achievements of this thesis are as follows:（1）Zincophilic hydrophobic nanofilm regulates interface solvation structure:We developed organic-inorganic interfacial nanofilm as a protective layer for the metallic zinc anode.The uniformly distributed zincophilic functional groups(O^2-groups)in the inorganic layer participated in and altered the solvation structure of hydrated zinc ions Zn（H₂O）₆²⁺,suppressing the deprotonation of solvated water,inhibiting H₂evolution and widening the electrochemical window of electrolyte.The nanofilm also induced a uniform zinc ion flux,promoting uniform zinc deposition on interface.Additionally,hydrophobic alkyl chains in the nanofilm effectively inhibited solvent water corrosion for zinc metal.The zinc anode was protected by nanofilm,achieving stable electrochemical cycling life.With a depth of discharge（DOD）of up to 67%,the nanofilm demonstrated a long cycling life of 300 hours.（2）Hydrophobic zinc ion conductor membrane accelerates zinc ion transport dynamics:We use a hydrophobic surfactant as a soft template to induce La F₃ to grow into organic-inorganic nanofilm at the water-air interface.The hydrophobic surfactant perfluorooctanoic acid shielded the electrode surface from chemical corrosion by water,inhibiting the slow H₂ evolution The bottom La F₃ layer had stronger binding energy and fast ion transport dynamics for zinc ions.Therefore,the protective layer provided a uniform and continuous zinc ion flux required in rapid current changes and facilitated rapid interface zinc ion replenishment.As a result,corresponding symmetric cells and half-cells cycled for over 4000 hours at 5 m A cm^-2 and 1 m Ah cm^-2 current density and capacity,demonstrating stable long-term cycling life of over 6000 cycles.（3）Interface negative charge density gradient protection layer induces uniform zinc ion deposition:A controllable thickness 2 D organic-inorganic hybrid heterostructure was constructed as a protective layer for the metallic zinc anode.The Si W₁₂O₄^4-polyoxometalate uniformly distributed between the layers underwent reduction(W⁶⁺reduced to W⁵⁺),imparting a negative density gradient characteristic to the protective layer.This property accelerates zinc ion deposition,maintaining a uniform zinc deposition.Simultaneously,exposed hydrophobic alkyl chains（DODA⁺）at the air interface accelerate zinc ion de-solvation and protect against water corrosion.Due to these advantages,the two-dimensional organic-inorganic hybrid interface protection layer exhibits high reversibility for zinc ion deposition and stripping.Cycling3700 times at 2 m A cm^-2 resulted in an average Coulombic efficiency of 99.97%.The full cell under high zinc utilization conditions exhibited stable cycling for hundreds of cycles.（4）Interface protective layer based on multiple hydrogen bonds optimizes zinc metal battery performance:We introduced multiple hydrogen bonds into polyoxometalate complex by organic modification and constructed an organic-inorganic interface protective layer on metallic Zn anode.However,maintaining the stability of the protective layer under repeated zinc ion deposition and stripping was challenging.To address this problem,a polyoxometalate cluster complex with multiple hydrogen bonds was constructed as an interface coating for the zinc metal electrode.The interaction of multiple hydrogen bond networks andπ-πstacking between molecules enhanced the stability of the structure,leading to improved cyclic performance.Cycling for 3500 hours at 5 m A cm^-2 and stable cycling for 1400 hours in the restorative experiment were achieved.In summary,this thesis designed and prepared four zinc electrode/electrolyte interface protective layers with different functional characteristics,which improved the electrochemical performance of zinc ions batteries.The structure of hydrophobic zincophilic,zinc ion conductor film,the mechanisms of uniform zinc ion deposition of based on polyoxometalate complexes as protective layer were theoretically and experimentally verified,as well as the effect on the electrochemical performance of zinc electrode.This work provides valuable insights for the design and preparation of efficient electrode/electrolyte interface protection layers.