| The growing energy demand and serious environmental pollution promote the use of primary energy from fossil fuels to renewable clean energy.Whether it is mobile applications or fixed energy storage applications,batteries are the best solution to meet the growing demand for energy storage.Zinc-based flow battery has the advantages of low cost,easy maintenance,safety,non-toxic,long service life and so on,showing a good application prospect.However,due to the limitation of low ion solubility,the energy density of zinc-based flow battery is low;the zinc metal electrode has the problems of deformation and dead zinc during the long term charge and discharge cycles,and the area capacity is usually less than 80 mAh/cm2,which seriously restricts the commercial application of zinc-based flow battery.In order to solve the problems of low energy density,low area capacity,deformation and dead zinc on the negative of zinc-based flow battery,zinc slurry was developed to replace the traditional zinc ion electrolyte,the performance of zinc slurry was evaluated systematically.The main conclusions are as follows:(1)Developed zinc slurry formula.When the mass ratio of Zn particles,nano ZnO particles,thickener and 4 M KOH solution is 2.5:3.1:1:18.5,the homogeneity and fluidity of the prepared slurry are better.A new method of layer by layer assembly of current collector and zinc slurry was developed.The prepared zinc slurry and porous thin carbon felt were overlaid layer by layer to build a three-dimensional interconnected electron ion transport network.The breakthrough of 100 mAh/cm2 high area capacity of negative was achieved.At the current density of 10 mA/cm2,coulomb efficiency is more than 92%,voltage efficiency is more than 87%and energy efficiency is more than 77%.The battery runs stably for more than 1400 h without degradation.(2)In order to achieve the multi-level confinement coating of the active components of the slurry,the ZnO@C with nano pore carbon shell was prepared by the two steps method of dopamine polymerization coating on the nano ZnO particles surface and temperature-programmed calcination.SEM,TEM,XPS,XRD and other characterizations proved that the nano ZnO particles were completely and uniformly coated by the carbon shell.The carbon shell has 0.4-0.7 nm micropores,which inhibits the outward diffusion of zincate ions and allows hydroxide ions to diffuse freely.The developed ZnO@C slurry has good electrochemical reversibility,the redox peak potential difference is only 0.3 V;it runs stably for more than 1100 h at current densities of 10 mA/cm2 and 15 mA/cm2.SEM and EDS characterization shows nano ZnO particles is still confined and dispersed inside the carbon shell,showing good cycle stability. |
