Study On Mxene And Its Derivatives-based Interface Protective Layer For Zinc Anode Of Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries are potential candidates for large-scale energy storage technology due to their high safety,low cost and simple assembly process.With abundant natural reserves,high theoretical specific capacity and low redox potential,zinc metal is a promising anode material for aqueous zinc ion batteries.However,Zn metal anode materials also suffer from the formation and growth of Zn dendrites and side reactions such as corrosion and hydrogen precipitation during the Zn deposition/dissolution,which affect their stability and reversibility and limit their practical applications.In this paper,three artificial interfacial layers,TiO₂@C,Ti Se₂@TiO₂@C and copper-modified Ti₃C₂Cl₂ MXene,based on MXene and its derivatives,were constructed on the surface of zinc anode using the scraping method to suppress zinc dendrites and interfacial side reactions and improve the electrochemical performance of zinc anode.The main studies are as follows:（1）TiO₂@C composites were prepared by calcining Ti₃C₂T_x MXene under CO₂atmosphere and constructed as an artificial interfacial layer for zinc anode.The TiO₂particles were embedded between the carbon sheet layers,and the TiO₂ particles could provide a large number of zinophilic sites and Zn ion transport channels,while the carbon sheet layers could homogenize the interfacial electric field,which together achieved high Zn ion flux and uniform charge distribution,thus inhibiting the growth of Zn dendrites.This interfacial layer has a contact angle of 93°with the 2M Zn SO₄electrolyte and exhibits hydrophobicity,which is conducive to the removal of water molecules from the solvent shell of hydrated zinc ions and thus inhibits the occurrence of side reactions at the zinc anode/electrolyte interface.The TiO₂@C interfacial layer modified zinc electrode TiO₂@C-Zn assembled symmetric battery can be stably cycled for more than 800 h at 5 m A cm^-2,1 m Ah cm^-2 The TiO₂@C-Zn||Cu half-battery can perform 700 Zn deposition/dissolution cycles at 10 m A cm^-2 with an average Coulomb efficiency of 99.5%.In addition,TiO₂@C-Zn The entire battery assembled by matching the negative electrode with Na V₃O₈·1.5H₂O positive electrode material also exhibits good cycle stability,indicating that TiO₂@C The practicality of the artificial interface layer.（2）Ternary composites of Ti Se₂@TiO₂@C were prepared by mixing Ti₃C₂T_xMXene with selenium powder and calcined at high temperature in an inert atmosphere,in which TiO₂ particles are embedded in the lamellar structure of Ti Se₂ and carbon,exhibiting zinc-loving and hydrophobic characteristics.This composite was coated on the surface of zinc anode to construct an artificial interfacial layer,in which the carbon lamellae can provide a conductive network and uniform interfacial electric field;the TiO₂ particles can provide zinc-loving sites and induce the rapid transport of zinc ions in the interfacial layer;the Ti Se₂ lamellae can further improve the zinc-loving property of the interfacial layer and promote the high flux transport of zinc ions,and have higher conductivity and lower hydrophilicity.Therefore,the Ti Se₂@TiO₂@C artificial interfacial layer can effectively induce the uniform deposition of zinc and inhibit the growth of zinc dendrites,and its contact angle with the electrolyte is 108°,forming a hydrophobic interface,which is conducive to slowing down the interfacial side reactions such as corrosion and hydrogen precipitation.After optimization of the preparation temperature,the symmetrical battery assembled with zinc anode modified by Ti Se₂@TiO₂@C interfacial layer material prepared by calcination at 600°C has a cycle life of more than 1000 h at 2 m A cm^-2,1 m Ah cm^-2,and the assembled Zn||Cu half-battery has cycled more than 800 cycles at 10 m A cm^-2,1 m Ah cm^-2 discharge conditions.times with an average Coulomb efficiency of 99.5%,illustrating the performance advantages of MXene derived selenides as an artificial interface layer for Zn anode.（3）Copper-modified Ti₃C₂Cl₂ MXene（Cu-MXene）containing only a single type of end group-Cl was prepared by a simple one-step molten salt etching method with both zincophilicity and hydrophobicity.It was directly coated on the surface of zinc foil as an artificial interface layer for zinc anode.The single-Cl end group makes it hydrophobic and has a contact angle of 110°with the 2M Zn SO₄ electrolyte,which is beneficial to inhibit the occurrence of side reactions such as hydrogen precipitation and corrosion at the zinc anode/electrolyte interface.In addition,Ti₃C₂Cl₂ MXene has high electrical conductivity and high zincophilicity,and the introduction of Cu atoms further enhances the adsorption of zinc ions at the interfacial layer,enabling uniform and stable dendrite free zinc deposition at the Cu-MXene interfacial layer.symmetric batteries assembled with Cu-MXene-Zn electrodes（Cu-MXene-Zn）modified by the Cu-MXene interfacial layer show a high degree of stability at 10 m A cm^-2 and 1 m Ah cm^-2,The Cu-Mxene-Zn half-battery at 10 m A cm^-2 showed a cycle life of more than 1000 h and a polarization potential below 120 m V.At a high deposition capacity of 10 m Ah cm^-2,Cu-Mxene-Zn could still be stably cycled for more than 130 h,while the bare zinc electrode failed after 22 h.The Cu-Mxene-Zn||Cu half-battery at 10 m A cm^-2 could perform 1100 cycles of Zn deposition/dissolution at 10 m A cm^-2 with an average Coulomb efficiency of more than 99.6%.In addition,the Cu-Mxene-Zn|Na V₃O₈·1.5H₂O full battery assembled with the matched Na V₃O₈·1.5H₂O cathode material can be stably cycled for 1000 cycles at a high current density of 4 A g^-1.Therefore,the Cu-MXene artificial interface layer has obvious effects in both inhibiting Zn dendrite growth and suppressing interfacial side reactions,effectively improving the stability and reversibility of the Zn anode,and is expected to be a general strategy for metal electrode protection in other aqueous battery systems.