Study On Dendrite Inhibition Mechanism And Battery Performance Of Laponite On Aqueous Zinc Anode

Lithium-ion batteries have provided many conveniences to our lives since their commercialization.However,the high cost of lithium and the toxicity and safety issues caused by organic electrolytes limit its application in large-scale energy storage.Aqueous rechargeable batteries based on nonflammable electrolytes have recently received considerable attention.Among them,the anode of aqueous zinc-ion battery（AZIB）has the characteristics of high specific capacity(5855 m Ah cm^-3)and low redox potential（-0.762 V vs standard hydrogen electrode）.Compared with other metal anodes（such as calcium,Magnesium,aluminum,etc.）,the metal zinc anodes have stronger intercalation and extraction kinetics,which stand out in aqueous battery systems.However,severe hydrogen evolution,corrosion reactions,and uncontrolled dendrite growth still occur in Zn metal anodes,resulting in low Coulombic efficiency and short cycle life.Therefore,there is an urgent need for feasible strategies to address the existing problems of Zn anodes.Surface modification and separator design can change the properties of the Zn-electrolyte contact interface,thereby alleviating the dendrite and side reaction problems of Zn anode.However,materials for surface modification and separator design are still lacking,and the dendrite suppression mechanism is still unclear.Therefore,it is necessary and extremely challenging to develop suitable materials for stabilizing Zn anodes and revealing its dendrite inhibition mechanism.Based on the above analysis,this thesis uses zinc-based laponite as the modified material for surface modification and separator design,and systematically discusses the influence of zinc-based laponite on the regulation of Zn plating and stripping behavior,and further clarifies its inhibition mechanisms of Zn dendrites and side reactions.The main research contents are as follows:（1）Using zinc-based laponite（Zn-LT）as the surface modification layer of the zinc anode can effectively regulate the deposition/stripping behavior of zinc ions and suppress the side reaction problem of the zinc anode.The Zn-LT protective layer has selective permeability to Zn²⁺,and the negatively charged interlayer channels in the protective layer can allow Zn²⁺to pass through quickly and repel SO₄^2-anions,so as to achieve uniform distribution of zinc ion flow and reduce by-product formation.In addition,the Zn-LT protective layer has a desolvation function.Since the binding energy of Zn-LT to Zn²⁺is higher than that of H₂O to Zn²⁺,the Zn-LT protective layer can destroy the solvation structure of[Zn（H₂O）₆]²⁺to reduce the number of free water at the zinc-electrolyte interface,thus suppressing the HER and corrosion of Zn anode.The results show that the Zn-LT@Zn symmetric battery has a cycle life of more than 830 h at a current density of 10 m A cm^-2.（2）A scalable rolling method was developed to directly roll the Zn-LT protective layer onto the zinc foil to obtain a robust protective layer with strong bonding to the Zn substrate.This method can achieve rapid and large-scale preparation of Zn-LT@Zn anode,and avoid the use of hydrophobic PVDF binder.Due to the cation-selective permeability and desolvation effect of the Zn-LT protective layer,the cycle life of the rolled Zn-LT@Zn anode reaches 1000h at a current density of 5 m A cm^-2.In addition,the Zn||MnO₂ full battery test shows that the introduction of Zn-LT protective layer by rolling technology can effectively improve the electrochemical performance of the full battery system,which verifies the application potential of Zn-LT and rolling technology in zinc-based batteries.（3）Using Zn-LAP modified glass fiber separator（GF）,the deposition behavior of zinc ions was effectively adjusted to achieve dendrite-free zinc deposition.The introduction of Zn-LAP endowed the GF separator with ion self-concentration and pumping function,and avoided the appearance of concentration gradient at the Zn deposition interface by prolonging the Sand’s time,thereby realizing the planar Zn deposition.At the same time,the reason for the planar deposition of zinc ions was kinetically explained by DFT calculations.The symmetric cell with the modified separator exhibits lower voltage polarization and long cycle life of up to 500 h at a high current density of 20 m A cm^-2.