Study Of Interface Stabilization And Electrochemical Mechanism Of Zinc Electrode In Aqueous Batteries

Energy storage systems with high-security and high-performance are of great significance for the development of strategic emerging industries such as new energy resources and smart grids.Rechargeable aqueous zinc batteries based on metallic zinc anodes with rich resources and high specific capacity possess plenty of advantages of high safety,high specific energy,and low cost,which are considered as one of the current research hotspots due to their application prospect of large-scale energy storage.However,the current zinc anode has serious corrosion and dendrite problems,affecting the electrochemical performance of zinc-based batteries.Zinc ions usually nucleate on the high-concentration local interface area and lead to low surface energy of the zinc nucleus area,which induces inhomogeneous deposition of zinc ions and nucleation accumulation and accelerates dendrite growth,thus resulting in battery capacity degradation or even short circuit.Therefore,it is the key and difficult point to enhance the interfacial stability for improving the electrochemical performance of zinc-based batteries.This article focuses on the influence mechanism of the interface between zinc electrode and electrolyte on the electrochemical deposition-dissolution of zinc ions,as well as the stabilization design of the electrode-electrolyte interface through multiple methods,including zinc electrode interface modification,electrode structure control,and electrolyte functionalization design.Moreover,an artificial SEI film on the zinc electrode interface has been constructed to induce uniform deposition of zinc ions and improve the stability of the zinc electrode-electrolyte interface,thereby effectively solving the problems of poor circulation and low efficiency in the amplification process,as well as laying a foundation for further promoting its industrialization.The main research contents of this paper are listed as follows:（1）Introduction of the inorganic inert interface layer of the zinc electrode.A kind of Al₂O₃ inorganic inert passivation layer with controllable thickness and porous structure is prepared by casting method.On the one hand,the obtained inert electrode interface can partly avoid direct contact between the electrode and free water molecules and hinder corrosion side reactions.On the other hand,the porous structure can not only homogenize the interfacial electric field and induce Zn²⁺to deposit on the surface of metallic zinc anode with a lower potential,but also accumulate a dendritic intermediate layer between the inert interface layer and the zinc anode from bottom to top,which effectively avoids the surface dendrite growth.The XRD phase analysis of the Al₂O₃/Zn electrode surface after charge-discharge cycles shows that almost no by-product of Zn₄SO₄（OH）₆·5H₂O has been produced.A symmetrical battery has been assembled based on Al₂O₃/Zn,of which the overpotential after a 500-hour charge-discharge cycle is only 77.5 m V at a current density of 1 m A cm^-2 and a capacity density of 1 m Ah cm^-2.The full battery assembled with lithium manganate positive electrode has a coulomb efficiency of 99.85%after 600 cycles of charge and discharge at a rate of 0.5C.（2）Design of zinc ion/electron dual functional modification layer.A modified layer of carbon fiber micron film（CFMF）is sprayed on the zinc surface.The modified layer with high specific surface area and high conductivity can homogenize the current density near the electrode and inhibit the growth of dendrites.The specific surface area of CFMF is 3.3735 m² g^-1,and the I_D/I_G in the Raman spectrum is as high as 1.53.The initial coulombic efficiency of the asymmetric battery after CFMF interface modification is 85.2%.Furthermore,the coulombic efficiency is as high as 98.4%after100 dissolution/deposition reactions.The symmetrical battery assembled by CFMF/Zn has been characterized systematically.The voltage curve remains stable during charging and discharging processes,and the overpotential pressure difference is only about 13m V after cycling for 2500 hours at a current density of 1 m A cm^-2 and a capacity density of 1 m Ah cm^-2.The electrode morphology characterization after cycling also shows that the bifunctional modified layer can drive the zinc ions and electrons flux to diffuse uniformly and quickly to the surface of the zinc anode,which greatly alleviates the dendrite growth.In addition,the full battery based on CFMF/Zn has been assembled and exhibited low polarization,good rate performance along with durable cycle stability.（3）Construction of a three-dimensional zinc electrode with a network structure.A three-dimensional porous zinc anode（3D Zn P/CF）has been prepared by tuning conductive carbon fiber network and active zinc powder.The porous structure and conductive network of this new type of zinc anode can provide sufficient ion deposition space and rapid ion/electron transfer,thereby exhibiting controllable Zn²⁺dissolution/deposition behavior and retarding dendrite growth.The contact angle of the electrolyte of the Zn P/CF electrode initially reaches 67.0^°and decreases to almost0 after 3 s,indicating that the electrolyte completely enters the electrode,which is conducive to the ion diffusion within electrode materials and reducing the charge transfer resistance.By the in situ recording and observation of the zinc ion deposition process with an optical microscope,it is proved that there was no obvious visible dendrite growth on the surface of the Zn P/CF electrode.The 3D Zn P/CF symmetrical battery exhibits a very small overpotential of 25.1 m V and an ultra-long cycle stability over 3000 h at a current density of 1 m A cm^-2 and a capacity density of 1 m Ah cm^-2,as well as higher rate performance than that of currently reported literature.In addition,a full battery has been assembled based on manganese oxide materials,which achieves a high capacity retention ratio of 93.2%after 7000 charge-discharge cycles at 0.1 A g^-1and high coulombic efficiency up to 99.36%.（4）Development of a unique electrolyte complexing additive with synergistic effect.A uniform and stable new electrolyte（BE/Zn SO₄）is proposed based on Zn SO₄solution complexed with Bi₂（SO₄）₃ under the action of chelating agent EDTA-2Na.BE/Zn SO₄ electrolyte contains high hydrogen evolution overpotential Bi³⁺,which can not only widen the electrochemical window of the electrolyte and inhibit the occurrence of hydrogen evolution reaction,but also exert the"base effect".Bi³⁺ions deposit on the protrusions of the electrode before Zn²⁺,which homogenizes the surface electric field to improve the uniformity of Zn²⁺dissolution/deposition,significantly inhibiting the growth of dendrites and improving the stability of the zinc electrode.The corrosion current of BE/Zn SO₄ is only 1.317×10^-6 A cm^-2,which is reduced by two orders of magnitude.Meanwhile,the corrosion potential is positively shifted by 5.3 m V,and the overall voltage window is expanded to 2.5 V.An asymmetric battery is assembled by using BE/Zn SO₄ as the electrolyte,and the coulombic efficiency during the first dissolution/deposition is increased to 91.6%.The BE/Zn SO₄ symmetrical battery can circulate stably for 700 h at 5 m A cm^-2 and 5 m Ah cm^-2.The full battery based on BE/Zn SO₄ electrolyte exhibits higher discharge capacity and long cycle life.