Application And Research Of Ethylene Glycol Dimethyl Ether In Surface Modification Of Zn Anode Of Aqueous Zn Ion Batteries

A bottleneck period in pursuing development for lithium-ion battery aroused a surging interest in seeking rechargeable battery with aqueous electrolytes due to its ntrinsically safe,environment-friendly and high ionic conductivity.Among these rechargeable batteries with aqueous electrolytes,zinc ion battery（ZIB）has attracted much attention because of its high theoretical capacity(820 m Ah g^–1 and 5854 m Ah cm^–3,respectively),low cost,non-toxicity,low redox potential（–0.762 V vs.SHE）and natural abundance.Although Zn anode has overwhelming advantages,it also has the following drawbacks.First,dissolved O₂ and free water in aqueous electrolytes will cause serious side reactions（such as hydrogen evolution and corrosion reactions）on the anode.Second,the uneven distribution of Zn²⁺flux and side effects will lead to uncontrolled dendrite growth of Zn anode,resulting in low Coulomb efficiency（CE）and poor cycle stability of aqueous zinc ion batteries（AZIBs）.These two challenges limit the practical application of AZIBs.In this paper,a simple and low-cost strategy was used to build an interface protective layer on the Zn anode to alleviate dendrite growth and side reactions.The effect of the interface protection layer on the Zn anode and the electrochemical performance of the assembled AZIBs are investigated.The improved performance of AZIBs further proved the feasibility of this strategy.The main research contents are as follows:（1）Modification of Zn anode by ethylene glycol dimethyl ether（DME）.The Zn@DME anode with a certain thickness of protective layer was prepared by a higher efficiency and lower cost way of dripping DME using pipette.The results of X-ray photoelectron spectroscopy（XPS）and depths etching show that the interface layer is mainly composed of Zn O.In addition,the Zn@DME anodes with less dendrites and by-products show that they can effectively prevent the direct contact between the electrode and electrolyte,thus alleviating the dendrite growth and side reactions during the process of charging/discharging.Therefore,when they are applied as the anodes of AZIBs,Zn@DME/Zn@DME symmetrical cells have excellent cycling stability of 480 h compared with the bare Zn anodes at 1 m A cm^–2,1 m Ah cm^–2.Moreover,Zn@DME anodes also exhibit stable CE（more than 110 h）and better rate/cycling performance,further verifying that modifying Zn anode by DME is an effective strategy.（2）Modification and electrochemical performance of Zn anode by bismuth trifluoromethane sulfonate（Bi（CF₃SO₃）₃）/DME solution.In order to solve the problems of dendritic growth,hydrogen evolution and corrosion side reactions on Zn anode,Bi（CF₃SO₃）₃/DME is utilized to prepare bismuth-based protective layer on Zn anode by in-situ chemical replacement reaction,enhancing interfacial adhesion and mechanical stability.The prepared bismuth-based protective layer can not only control the nucleation site of Zn²⁺,but also promote Maxwell-Wagner polarization to be favorable,resulting in uniform Zn stripping/plating.In addition,the effective mitigation of corrosion reaction and the reduction of by-products limit the growth of Zn dendrites.Thanks to the above advantages,the symmetrical cells with modified Zn as anode show excellent cycle stability at different current densities with fixed areal capacity of 1 m Ah cm^–2.Compared with the pristine Zn anodes,modified Zn-Ti half-cells have higher CE（91%）.At the same time,the modified Zn/NH₄V₄O₁₀ full-cells exhibit higher charging/discharging specific capacity,excellent rate(158 m Ah g^–1 specific capacity at10 A g^–1)and cycling performance(maintaining 195 m Ah g^–1 specific capacity after cycling 500 times at 5 A g^–1).