Design And Preparation Of Electrode Materials For Aqueous Zinc Secondary Batteries And Their Performances

With the massive consumption of fossil energy and excessive emission of greenhouse gases,environmental problems are becoming more and more serious,and the global demand for sustainable energy and high-quality energy storage devices is increasing.Currently,secondary batteries as a common energy storage device play an important role in daily production and life.Among them,lithium-ion batteries have become the most widely used energy storage devices because of their high operating voltage,high energy density,and long cycle life.However,the application of lithium-ion batteries in large energy storage devices is limited by the insecurity of organic electrolytes and the scarcity of lithium resources,so aqueous metal-ion batteries are gradually entering the vision of researchers.Among them,compared with lithium and other metals,zinc has the advantages of large volume capacity(5851 m Ah cm^-3),abundant storage capacity,and high safety,and shows good electrochemical activity in aqueous electrolytes,so aqueous zinc ion batteries are considered a kind of high-quality energy storage devices with great potential.However,in practical applications,there are still many problems in aqueous zinc ion batteries.On the one hand,zinc metal cathodes suffer from zinc dendrites growth,surface passivation,hydrogen precipitation,etc.On the other hand,cathode materials also face problems such as poor stability,easy dissolution,poor electrical conductivity,slow ion diffusion,and easy phase change in structure.Therefore,the preparation of electrode materials with high electrochemical performance is necessary for the further development of high-performance aqueous Zn-ion batteries.To solve the above problems,this paper proposes improvement strategies for anode and cathode in terms of surface modification and structure design:（1）Preparation of highly stable carbon-coated zinc metal anode and its performance:Amorphous carbon was coated on the surface of zinc foil using magnetron sputtering technology for surface modification of zinc negative electrode.The amorphous carbon coating has good uniformity,good bonding,and good denseness,which avoids direct contact between the electrolyte and the zinc foil and hinders the corrosion of the electrolyte on the zinc substrate,thus effectively eliminating the occurrence of side reactions.In addition,the characterization results show that the coating can effectively induce the uniform deposition of zinc ions and thus inhibit the formation of zinc dendrites.The Zn/C-0.8//Zn/C-0.8 symmetric cell composed of amorphous carbon-coated Zn cathode showed a low corrosion current of 5.94μA,which was much lower than that of 96.07μA for bare Zn foil.The Zn/C-0.8//Zn/C-0.8 symmetric cell with amorphous carbon-coated Zn cathode could cycle stably for 780 h at 1 m A cm^-2/1 m Ah cm^-2 with an overpotential of 0.04 V,demonstrating excellent cycling stability.This exhibits excellent cycling stability.The asymmetric capacitor with Zn/C-0.8 as the negative electrode and porous carbon as the positive electrode exhibited a discharge specific capacity of 58.7 m Ah g^-1 after 1500 cycles at 1 A g^-1,with a capacity retention rate of 75%and a coulomb efficiency of about 100%,showing a better capacitance capacity and longer cycle stability than the capacitor with pure Zn foil as the negative electrode.（2）Preparation of amorphous vanadium oxide and its zinc storage performance:Amorphous V₂O₅（AVO）was successfully prepared by etching V₂O₅·1.6H₂O with phosphine and used as an aqueous zinc secondary battery cathode.AVO retains the thin and folded nanosheet structure of V₂O₅·1.6H₂O,which allows it to provide a sufficiently large contact area between the electrode material and the electrolyte to shorten the ion transfer distance,which facilitates the achievement of high capacity and high multiplicity performance.The nano-voids etched on the surface of the nanosheets can increase the active sites and effectively improve the ion transport for fast reaction kinetics.In addition,the amorphous structure not only provides more exposed ion channels to accelerate fast charge transfer at the electrode/electrolyte interface,further promoting rapid ion embedding,but also provides excellent chemical stability.Using AVO as the cathode material for aqueous zinc ion batteries,the AVO electrode exhibits superior zinc ion storage capacity,with a discharge specific capacity of up to 425.6 m Ah g^-1 at a current density of 0.1 A g^-1;at a high current density of 10 A g^-1 its discharge specific capacity is also higher than the unetched V₂O₅·1.6H₂O,the specific capacity and rate performance of AVO are significantly improved.The AVO exhibits 92%capacity retention after 1000 cycles at a current density of 2 A g^-1,demonstrating excellent cycling stability.