Study On The Performance Of V₂CT_x In Zinc Anode Protection Of Aqueous Zinc-ion Batteries

In recent years,the demand for clean and sustainable energy has increased rapidly due to the aggravation of environmental pollution caused by excessive dependence on fossil fuels.Therefore,the development of efficient,stable and cheap energy storage devices is of great significance for the utilization of clean energy.Compared with organic solvents,even under extreme conditions or thermal runaway,aqueous electrolytes will not burn or explode,are safer,and aqueous electrolytes are inexpensive and easy to assemble.Therefore,the development of aqueous batteries has received widespread attention.Among the existing types of aqueous batteries,zinc-ion batteries have attracted widespread attention because of their high compatibility with aqueous electrolytes.MXene has attracted much attention in the field of energy storage because of its unique layered structure and high conductivity.In this paper,V₂CT_x is used as the main research object,and different preparation methods of materials are explored,and the research results are as follows:In this paper,V₂Al C is etched by hydrothermal method,and the results of infrared spectroscopy and Raman spectroscopy show that V₂CT_xsurface has surface functional groups such as-OH,-O,and-F,and XRD and SEM test results prove that the reaction temperature of 120°C and the reaction time of 18 hours are the best etching conditions.In order to explore the feasibility of MXene-V₂CT_x to protect zinc anodes,we started with zinc anode protection strategy-surface engineering.First,a single and uniform MXene layer is applied on the surface of the Zn negative electrode,and the electrochemical impedance spectrum shows that the interface resistance of the negative electrode is greatly reduced after coating MXene-V₂CT_x.The long-cycle performance of Zn and V₂CT_x@Zn symmetrical batteries under the condition of area specific capacity of 1 m Ah cm^-2 was studied by constant current charge and discharge test,and it was found that the voltage of pure zinc symmetrical batteries increased significantly after about 60 hours of constant current charge and discharge.After coating V₂CT_x,the battery can still work normally after 1000 hours of cycling,and the coating of MXene layer increases the cycle stability of the zinc sheet anode by more than ten times.The half-cell tested and assembled also found that V₂CT_x@Zn anode has excellent reversibility during deposition peeling.In the full battery,V₂CT_x@Zn-Mn O₂ provides a high initial capacity(228.3 m Ah g^-1),and the capacity can be maintained at 127.2m Ah g^-1 after 300 cycles at a current density of 1 A g^-1,however,the Zn-Mn O₂ battery has an initial capacity of only 197.3 m Ah g^-1,which drops to 96.1 m Ah g^-1 after 300cycles.Starting from the electrolyte additive of another zinc anode protection strategy,we use V₂CT_x as an electrolyte additive.The results of scanning electron microscopy showed that when the concentration of V₂CT_x additive was 0.10 mol/L,almost no lumpy dendrites appeared,which proved that V₂CT_x effectively inhibited the growth of dendrites.In order to explore the ion exchange between the electrode and the electrolyte,the test results of the water contact angle measuring instrument found that the contact angle between Zn SO₄ electrolyte and zinc sheet was as high as 100.9°,while the contact angle between Zn SO₄ electrolyte and zinc sheet added V₂CT_x was 66.6°.This indicates that after adding V₂CT_x to the electrolyte,the wettability of the interface between the electrode and the electrolyte is improved,which is conducive to the uniform deposition of zinc ions and the formation of a smooth electrolyte film on the surface of the electrode sheet.The specific capacity,coulombic efficiency,cycle life and rate performance were explored by cyclic voltammetry test and constant current charge and discharge test,and it was found that the battery using V₂CT_x@Zn SO₄ electrolyte had a lower nucleation barrier and a longer cycle life.