| Aqueous zinc-based energy storage system is considered as one of the most potential candidates to replace organic lithium-ion batteries.Zinc-based energy storage devices based on water system with zinc as anode electrode have competitive advantages such as high-power density,high security and wide source.Unfortunately,the further application of aqueous zinc-based energy storage devices is seriously hindered by the problems of dendrite growth and the side reaction of electrode in the process of charge and discharge due to the direct contact between electrolyte and electrode.Therefore,it is urgent to solve these problems to make up for energy storage devices.In this paper,we used sodium saccharin,polyamide and polypyrrole as protective layers to protect the zinc metal anode from the perspective of coating to reduce the dendrite growth and the side reaction of the electrode.The cycle life of zinc plating/stripping for zinc metal anode is prolonged and improved effectively.The innovation points of the paper are summarized as follows:1.In order to solve the dendrite growth problem at high current density,we take the saccharin sodium as the electrolyte additive as a molecular level coating modified zinc metal electrode,during the process of charge and discharge,there is competitive relationship between saccharin anionic and zinc ions.Thus,Zn2+were forced to uniform deposition in zinc metal inhibiting dendritic growth.The optimum adding amount was0.20 g/L in this electrolyte,the assembled zinc symmetric cells at high current density and high capacity(5 m A/cm2,8 m A h/cm2)can effectively inhibit the growth of zinc dendrite,realize the favorable transformation of by-products and exhibit a long zinc plating/stripping life of 3800 h.At the super current density of 20 m A/cm2 and 5 m A h/cm2,the cycle stability is more than 800 h.Assembled hybrid capacitor with activated carbon displays higher capability retention and coulomb efficiency at current densities of0.5 and 5 m A/cm2.The addition of saccharin sodium solved the problem of dendrite growth to a large extent,but the problem of by-products is still serious.2.In order to reduce the generation of by-products while solving the problems of dendrite growth and electrochemical hydrogen evolution.An artificial PA coating with a special ant nest structure containing trace amount of lithium trifluoromethyl sulfonate(LITFO)(PL)was fabricated by hydrogel phase transformation method.The coating can filter the Zn2+solvation water layer by layer through the special microporous structure,which significantly inhibits the dendrite growth,electrochemical hydrogen evolution and reduces the generation of by-products.PL@Zn anode assembled symmetric cells in the current densities of 0.5 and 0.25 m A/cm2,capacity of 0.25 m A h/cm2 both show excellent zinc plating/stripping cycle stability.Assembled hybrid capacitor with activated carbon shows excellent performance under the current density of 0.5 m A/cm2,after cycling for300 cycles,the coulomb efficiency is 99%,capacity retention near 60%.3.In the plane surface of zinc anode interface coating modification,still has the potential of dendrite growth,to solve this problem,we combined electrochemical polymerization and chemical etching method to construct three-dimensional hollow PPy foam,and realized the localized deposition of metal zinc inside of PPy foam,thanks to PPy three-dimensional,hollow structure and surface functional groups polarity hydrophilic,PPy@Zn as the anode assembled symmetrical cells in 10 m A/cm2,under 1m A h/cm2 show excellent cycle stability,the Coulomb efficiency of the hybrid capacitor assembled with activated carbon is close to 99%after 10,000 cycles at 1 m A/cm2.The results show that the special three-dimensional hollow structure coating constructed by us effectively prolongs the electrode life. |
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