Application Of Organic Molecules Based On Thiophene Groups In Constructing High-performance Anode Of Aqueous Zinc-ion Batteries

With the increasing depletion of traditional fossil energy and the increasing demand for energy,the development and utilization of new energy storage batteries is imminent.As a new type of battery with cost advantage,performance advantage,safety and environmental protection,aqueous zinc-ions battery is a strong competitor to replace lithium-ion batteries to occupy the commercial market.Zinc metal is the preferred material of zinc-ions battery anode due to its abundant reserves,low redox potential,high mass specific capacity and volume specific capacity.However,zinc anodes often face problems in practical applications,such as zinc-dendrites,hydrogen evolution reactions,side reactions and electrode surface corrosion,which directly affect the coulomb efficiency and cycle life of the batteries.At present,there are a variety of improvement strategies for zinc anodes.Among of them,Electrode interface modification can also be called artificial interface layer modification,which is one of the most widely used solutions because of its strong operability,simplicity and convenience.Organic materials often have flexibility and toughness,which can accommodate the volume change of electrodes.Meanwhile,their rich groups provide more active sites,which is conducive to regulating zinc intercalation/deintercalation.Based on these,we used organic molecular materials with thiophene groups to construct artificial interface layers to modify the zinc anode,and explored their influence on battery performance and their intrinsic working mechanism,and the research conclusions are as follows:Firstly,TTP artificial interface layer was constructed with 7-tert-butyl-1,3,5,9-tetrathiophenepyrene（hereinafter referred to as TTP）.TTP@Zn symmetrical cells have excellent cycle stability,rate performance and high current tolerance,which stably cycled close to 1000 h with the polarization voltage is only 51 m V at 0.885 m A cm^-2.Zn//TTP@Ti half-cells show low degree of polarization and stable coulombic efficiency,maintaining a coulombic efficiency of approximately 98.4%over up to 350 cycles at1.77 m A cm^-2.In addition,TTP-modified cells also show excellent corrosion resistance,and the problems of the spread of zinc-dendrites,by-products and hydrogen evolution reactions have been significantly alleviated.Subsequently,it is proved that TTP is zinc-philic as the artificial interface layer.The electronegativity at S atom of TTP is higher,where it is more likely to attract Zn²⁺.Meanwhile,there is an interaction between S and Zn,and the TTP artificial interface layer reduced the desolvation activation energy of zinc ions.It was shown that the Zn-S interaction promoted the kinetics of zinc ion deposition and favored uniform zinc deposition.The long cycle stability of the TTP@Zn//V₂O₅ full cells are greatly improved,which can provide high specific capacity and stable cycling at 5 A g^-1,and can still maintain a capacity retention of 99.98%after 6500 cycles.The polarization degree and impedance are reduced,indicating the application feasibility of TTP artificial interface layer.Finally,theα-sixthiophene（hereinafter referred to as ST）composed of six thiophene groups was used to construct the ST artificial interface layer.ST@Zn symmetrical cells show excellent long-cycle stability and rate performance,stably cycling of more than 1700 h with polarization voltage of only 67.1 m V at the current density of 1 m A cm^-2.Zn///ST@Ti half-cells have low polarization,maintaining a coulombic efficiency of approximately 98.75%over 400 cycles,demonstrating the reversibility of zinc deintercalation.The ST@Zn and ST@Ti surface after cycling showed flat morphology,which proved that zinc could be uniformly deposited on the surface of both Zn and Ti foil.XRD pattern proved that the by-products during the cycle process were effectively inhibited.The number of zinc-ions transfers in ST-modified electrodes is increased,indicating that it is beneficial to improve reaction kinetics.Through the experimental exploration of the performance of ST artificial interface layer and the present of Zn-S interaction signal in XPS spectra,it is further verified that the S atom in the thiophene group can promote desolvation and regulate zinc-ions flux.