Design Of Honetcomb-like Hierarchically Porous Transition Metal,n-codoped Carbon Material And Its Application In Aqueous Zinc-based Batteries

Zn-Air and Zn-ion batteries,as high-efficient,low-cost and environmental-friendly storage technologies,have attracted intensive attention.In the case of Zn-Air batteries,the sluggish kinetic of ORR,as well as the scarce reserves,high-cost and poor-durability of optimal precious metal catalysts(such as Pt-based catalysts),has seriously hindered its performance and application.Specific to the Zn ion battery,the primary problems of the dendrites formation and side reactions(Zn corrosion and hydrogen evolution reaction)during charging and discharging process,would limit the coulombic efficiency and cycle stability of the batteries.In response to the above problems,the specific research contents are as follows:(1)Facing the needs of zinc-air batteries,upon carbonization of the lyophilized precursor mixture at high temperatures and removal of the template,we fabricate the honeycomb-like hierarchically porous Fe,Zn,N-codoped carbon material(FeZnN-C).We choose NaCl as the template agent,ZnCl2 as the activation agent,dicyandiamide and glucose as the carbon/nitrogen-containing precursor compounds and FeCl3·6H2O as the source of metal.By optimizing preparation conditions(amounts of ZnCl2 and FeCl3·6H2O,calcination temperature),the catalyst with the best ORR performance was screened out.The morphology,element valence,chemical environment characterization and ORR performance of N-C,FeN-C,ZnN-C,FeZnN-C were carried out to explain the effect of the addition of ZnCl2 for the microstructure of the material,and the relationship between structure and activity.Due to the hierarchically porous structure,relatively high N content,especially high percentage(8.44%)of effective N(pyridinic N,graphitic N and M-N)and large BET specific surface area(1455.2 m2/g),FeZnN-C exhibits excellent ORR performance(E1/2=0.901 V vs.RHE,jL=-6.04 mA/cm2,H2O2%=1.25%and n=3.97).This work assembles the zinc-air battery,which shows superior performance(specific capacity=785 mAh/gZn,peak power density=257 mW/cm2,discharging potential=1.36 V@10 mA/cm2).(2)Facing the demand of zinc-ion batteries for non-dendritic zinc anode materials,the honeycomb-like hierarchically porous Zn,N-codoped carbon material(ZnN-C650),which is utilized as a substrate to guide a uniform and dendrite-free Zn deposition by galvanostatic electrodeposition as the anode of zinc-ion batteries(Zn/ZnN-C650),is prepared by similar ZnCl2-assisted NaCl template method(without FeCl3·6H2O).The prepared Zn/ZnN-C650 has a large specific surface area,abundant Zn,N-codoped nucleation sites and hierarchically porous structure,which increases the contact area with the electrolytes and contributes to the Zn2+concentration distribution in the electrolytes near the anode and homogeneous electric field distribution.The prepared Zn/ZnN-C650 was assembled into a symmetrical coin cell,which exhibited stable and low overpotential(35 mV)and a long-life span(600 h)at 0.5 mA/cm2-0.5 mAh/cm2,superior to the symmetrical coin cell assembled by commercial Zn plate.