| Aqueous zinc-ion batteries(ZIBs)are synergistically integrated products with inherent safety and high energy density,and are considered as an ideal energy storage system for largescale and portable/wearable electronics.In recent years,although rapid progress has been made in the development of high-performance cathode materials and the exploration of the corresponding storage mechanism,the anode problems such as dendrite growth and side reactions have greatly shortened the battery lifespan.Based on the factors influencing the reversible performance and the optimization strategy for the protection of zinc anode,this paper aims to design and develop a novel,inexpensive,high-performance,highly reversible zinc anode to improve the stability of zinc-ion batteries.The functionally oriented optimization strategy for the Zn anode interface provides fundamental theoretical guidance and feasible alternatives for the construction of highly reversible Zn anodes in the future.The main innovative results are as follows:1.A three-dimensional nano-porous channel tin(Sn)layer-protected zinc anode was constructed by in-situ substitution reaction,and the Sn protective layers with optimal adhesion and stability was achieved by adjusting the reaction time.Through multi-scale visualization research techniques such as Micro X-ray computed tomography(Micro-CT)and in-situ optical microscopy,the dendrite growth of zinc during the deposition process was carefully observed and analyzed,and it was found that the metal Sn protective layer can significantly alleviate the dendrite growth to promote the uniform deposition of zinc on the surface.Electrochemical tests show that the metal Sn protective layer is closely related to the adsorption of Zn2+,which inhibits the surface diffusion of Zn2+and avoids the accumulation of charges.Density functional theory calculations confirm that the stronger adsorption of Zn atoms on the Sn surface promotes tighter bonding between Zn and Sn,restricts the diffusion of Zn and alleviates the formation of Zn dendrites.Benefiting from this special nanochannel structure and stable artificial metal Sn protective layer,the Zn//Zn symmetric cell based on Sn-Zn anode exhibits over 800 hours of cycling stability at a current density of 1 mA cm-2 and small voltage hysteresis(about 28 mV).Compared with bare Zn anode,this cycle life is increased by nearly 6 times.In addition,the NaV3O8 1.5H2O//Zn full cell based on Sn-Zn anode also maintains good cycling stability and nearly 100%Coulombic efficiency at a current density of 1 A g-1.2.Mesoporous molecular sieves with uniform pore size were prepared by hydrothermal method,and physically coupled with Zn foil to construct a stable molecular sieve-zinc anode,which provided ordered channels for local high-concentration electrolytes.Different highconcentration solvation structures at the interface can be achieved by adjusting the pore size of molecular sieves,and the optimal pore size is the mesoporous MCM41 channel.It was confirmed by Raman spectroscopy that Zn2+ions can form a unique coordination environment in our designed pores,which is conducive to the formation of a locally concentrated electrolyte,thereby preventing active H2O molecules from direct contact with metal zinc,inhibiting HER,corrosion and by-product.Multiphysics COMSOL simulations show that the molecular sieve protective layer can effectively reduce the local electric field strength and induce a re-uniform distribution of the electrolyte concentration,so that Zn2+ions are uniformly deposited,and finally a uniform surface is formed.Benefiting from this,the MCM41-Zn anode exhibits excellent cycling stability(1 mA cm-2,1800 h;5 mA cm-2,2200 h)and high coulombic efficiency at different current densities.In addition,the CaV3O8·nH2O(CVO)//MCM41-Zn full cell also exhibited a high capacity of 274.2 mAh g-1,long cycle life and high capacity retention(1000 cycles at a current density of 4 A g-1,no capacity fading),significantly better than CVO//bare Zn full cells.This work provides a strong basis for the design of local highconcentration electrolyte interfaces,which will inspire more porous materials for the protection of zinc anodes and provide a prospective route toward the stabilization of Zn metal anodes for high-performance ZIBs and other aqueous battery systems.3.A cost-effective electrolyte was achieved by adding threonine(TH)to the ZnSO4 electrolyte.By adjusting the added amino acid content,it was found that ultra-trace(10 mM)TH can significantly improve the stability of zinc anode.Scanning electron microscopy and insitu optical microscopy were used to compare and analyze the deposition morphologies of Zn in different electrolytes.The presence of additives can significantly alleviate the growth of dendrites and promote the uniform deposition of Zn on the surface.NMR,Raman spectroscopy and Fourier transform infrared spectroscopy studies indicate that TH molecules are regulated by breaking the coordination between the H2O and Zn2+ ions in the sheath and forming a strong bond between the SO42-and Zn2+ions.The solvated structure facilitates the transfer of Zn2+ions and weakens the energy barrier during de-solvation.Fluorescent and theoretical calculations confirmed that TH molecules can adsorb on the surface of Zn anode and occupy the initial hydrogen production sites,increasing the overpotential of HER,thereby suppressing hydrogen production.In addition,the adsorption of TH molecules amplifies the planar steric effect,effectively limiting the two-dimensional surface diffusion of Zn2+ ions,effectively limiting the tip effect,inhibiting the growth of Zn dendrites,and promoting the formation of uniform Zn.Therefore,the Zn//Zn symmetric battery assembled with 3 M ZnSO4 and 10 mM TH additive electrolyte exhibited stable cycling performance over 580 h at 1 mA cm-2 and 1 mAh cm-2.Thus,compared with the Zn//CVO full cell assembled using pure 3 M ZnSO4 electrolyte,the full cell with the addition of TH additive exhibits better stability,rate capability and capacity retention performance.Importantly,the low-cost additive strategy can be extended to other amino acid molecules such as glycine,serine and glutamic acid4.Carbon cloth modified with oxygen-containing functional groups were prepared by an electrochemical anodization method as a current collector for metal zinc plating/stripping.Theoretical calculations confirmed that three oxygen-containing functional groups(-C= O,COOH,-COH)on the carbon cloth exhibited stronger zincophilicity,so that these sites could serve as initial nucleation sites,and guide uniform Zn deposition and alleviate dendrite growth during repeated process.Therefore,the EACC@Zn symmetric cell can stably cycle for 350 h under the condition of 1 mA cm-2-1 mAh cm-2,the Coulombic efficiency can reach 95%,and the polarization voltage is only 84 mV.In addition,it exhibits excellent stability and rate performance.More importantly,the flexible quasi-solid ZIBs assembled with PAM/Zn(SO4)2 gel electrolyte exhibited excellent mechanical flexibility and bending resistance,showing their superior scalability and potential applications in wearable electronics. |
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