Study On The Surface Modification Of Zinc Anode And Its Electrochemical Properties

Aqueous zinc-ion batteries have emerged as promising candidates for large-scale energy storage systems due to their inherent safety and competitive capacity.Directly employing metallic Zn foil as an anode significantly simplifies battery manufacturing and simultaneously broadens the operating voltage window of aqueous batteries.Nevertheless,serious issues,such as dendrite growth and side reactions occurring at the Zn/electrolyte interphase,make the Coulombic efficiency and lifespan of Zn metal electrodes far from satisfactory and impede the commercialization of zinc-ion batteries.Hence,ameliorating the interfacial issues of the zinc anode is imperative for zinc-ion batteries.In order to solve the above problems,two different modification layers were constructed on the zinc surface to stabilize the zinc anode using bonding with zinc atoms on the surface of the zinc foil.Firstly,using the CVD method to build a dense and uniform Zn Te protective layer on the surface of the zinc foil in situ.During the high-temperature tellurization process,the exposed main crystal plane of Zn is changed,thereby suppressing the occurrence of side reactions and uniform Zn²⁺flux and achieving controllable Zn growth orientation and dendrite-free Zn plating/stripping process.Due to the in-situ construction of the protective layer,the atomic bonding of Te and Zn enables Zn Te to exist firmly on the surface of the zinc foil.The dense Zn Te layer can avoid direct contact between the electrolyte and the electrode and slow the generation of hydrogen evolution and by-products.And the crystal plane of the zinc foil treated at high temperature is changed from the original（101）to the（002）crystal plane.It is well known that the（002）plane has a lower surface energy than the（101）plane,which can better inhibit hydrogen evolution and corrosion.Moreover,the atomic arrangement of the（002）crystal plane is symmetrical and the surface is smooth,which benefits the uniform deposition of Zn.Therefore,when the preferred crystal plane is（002）,the deposited Zn can be close to the parallel substrate to realize the orderly deposition of Zn.The Zn Te@Zn anode has achieved an excellent cycle performance of 1500 h at 1 m A cm^-2 with 1 m Ah cm^-2.The Zn Te@Zn symmetrical cell has cycled steadily for 370 hours at a current density of 20m A cm^-2.Additionally,the assembled Zn Te@Zn/Mn O₂full cells have outstanding capacity stability for 1000 cycles with a CE close to 100%.Subsequently,considering that the electrochemical stability of the zinc anode should be guaranteed under more stringent conditions,the high mechanical flexibility of the organic polymer was used to achieve a stable cycle under"double-high"conditions（high current densities and high deposition capacities）.Using a dip coating method to apply 1H,1H,2H,2H-perfluorooctyltriethoxysilane（PTES）to the surface of the zinc foil to form an ultra-thin,hydrophobic and homogeneous modification layer.After sufficient hydrolysis,the PTES layer is bonded to the zinc foil surface,thus stabilizing the presence of the hydrophobic modification layer on the zinc foil surface,effectively avoiding hydrogen evolution and side reactions and alleviating the problem of reduced CE.In addition,the C-F bond from the CF₃species in PTES acts as a Lewis alkaline site,effectively promoting the diffusion of Zn²⁺and lowering the deposition potential of Zn²⁺,resulting in faster kinetics during Zn nucleation and achieving uniform Zn deposition.The results show that the PTES@Zn anode has a stable cycle performance of over 3890 h and a cumulative deposition capacity of 9600 m Ah cm^-2 in a symmetrical cell.Even at a current density of 30 m A cm^-2 with a capacity of 10 m Ah cm^-2.The PTES@Zn anode also has an excellent rate performance with a stable cycle performance of more than 220 h.More importantly,the assembled PTES@Zn/Mn O₂full cell achieves performance well beyond that of the Zn/Mn O₂ cell.The PTES@Zn anode enables a long-cycling life of over 900 cycles at 1 A g^-1in full cells.The pouch cells pairing this novel anode and Mn O2 cathode maintain over 150 m Ah g^-1 capacity retention after 150 cycles.