Preparation Of Carbon Cloth-based Flexible Electrode Materials And Their Zinc Storage Performance

In recent years,with the rise of electric vehicles,portable and wearable electronic products,batteries have developed towards high energy density,long life and excellent flexibility.Lithium-ion batteries are widely used due to their high energy density.However,harsh production conditions,expensive production costs,and flammable organic electrolytes have restricted their further development.At this time,aqueous zinc-ion batteries are considered by domestic and foreign researchers as the most promising candidate for the next generation of energy storage batteries due to their low cost,high safety,and abundant zinc resources.However,the drawbacks of low working voltage,zinc dendrites and electrode flexibility of aqueous zinc-ion batteries still need to be solved urgently.Therefore,this study takes aqueous zinc-ion batteries as the research object,and uses carbon cloth as a flexible substrate and active materials to construct flexible electrode materials to achieve high working voltage,long-life,and flexible aqueous zinc-ion batteries.The main research works and results are as follows:(1)In view of the low voltage problem of water-based zinc-ion batteries,metal ion doping is used to reduce the oxygen evolution/hydrogen evolution reaction activity of the cathode/anode to broaden the battery voltage window.Commercial carbon cloth is pretreated by chemical oxidation to obtain activated carbon cloth(ACC)as a flexible electrode substrate.Then,a facile electrochemical method is employed to prepare Na_0.25Mn O₂@activated carbon cloth(Na_0.25Mn O₂@ACC)cathode and Zn@K⁺-inserted activated carbon cloth(Zn@K-ACC)anode for zinc-ion battery.Benefiting from the phase evolution from Mn₃O₄ to Na_0.25Mn O₂ by simultaneous Na⁺insertion and Mn O₂ conversion during electrochemical treatment,the potential range for Na_0.25Mn O₂@ACC cathode can be extended to 0-1.3 V.Analogously,flexible Zn@K-ACC anode with high electrochemical performance can also be prepared by pre-inserting K⁺.The Na_0.25Mn O₂@ACC||Zn@K-ACC battery delivers a high operating voltage plateau of 1.60 V,a large energy density of 504.49 Wh kg^-1 at a power density of 1.54 k W kg^-1 as well as an excellent cyclic stability over 2000 cycles with 91.8%capacity retention at a current density of 2.0 A g^-1.(2)In order to solve the problem of poor reversible cycle performance of zinc ion batteries caused by zinc dendrites,a lightweight 3D flexible Zn plating/stripping scaffold,Cu nanosheets grown on activated carbon cloth(Cu nanosheets@ACC),is prepared by a electrochemical deposition technology.Compared with activated carbon cloth(ACC),Cu nanosheets@ACC current collector delivers higher special surface area and conductivity.Besides,Cu nanosheets layer not only can provide numerous,uniformly distributed Zn deposition sites but also can significantly decrease Zn nucleation overpotential.As a consequence,Zn@Cu nanosheets@ACC(Zn grown on Cu nanosheets@ACC)anode delivers a highly reversible Zn plating/stripping behavior with satisfactory cyclic stability rather than uncontrollable Zn dendrites growth.Moreover,a zinc ion battery based on the Zn@Cu nanosheets@ACC anode and Mn O₂@ACC(Mn O₂ grown on ACC)cathode presents high average coulombic efficiency(97.9%)and excellent cycling stability(94.8%)over 1000 cycles at 1 A g^-1 as well as satisfactory mechanical properties.(3)To suppress the growth of zinc dendrites and improve the cycle stability of aqueous zinc-ion batteries,a dendrite-free zinc composite anode(HGDY@Zn@ACC)was polymerized in situ on the surface of Zn@ACC through alkynyl coupling reaction using 1,3,5-triacetylenebenzene as monomer,Zn@ACC as flexible substrate,and Cu Br₂ as catalyst to obtain a graphene protective layer on Zn@ACC.The study found that when the monomer content is 10 mg,a uniform nanoporous HGDY film can be formed on the surface of Zn@ACC to form a dendrite-free flexible anode(HGDY@Zn@ACC-10).At this time,the HGDY layer can significantly increase the specific surface area(175.42 m² g^-1)of the composite zinc anode,the lowest Zn nucleation overpotential,and great conductivity.Moreover,a Zn||Mn O₂ flexible battery was assembled using HGDY@Zn@ACC-10 as anode and Mn O₂@ACC as cathode,which shows an excellent reversible cycle performance.Specifically,the capacity retention of the as-assembled battery was 86.3%after3000 cycles,and the coulombic efficiency was 91.0%at a current density of 1 A g^-1.