Preparation Of Gel Electrolyte And Metal Nitrogen Doped Carbon Composites And Performance Of Solid Zinc-air Battery

Solid-state zinc-air batteries are considered to be highly promising power batteries because of their higher theoretical energy density,low cost,environment-friendly and safe.However,the slow oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)of air electrodes and the solid electrolytes with poor performance are the main factors limiting their development.Finding high performance solid electrolytes and highly electrochemically active dual-function catalysts is the key to solving the problem.In this paper,a solid electrolyte was synthesized at first,and a solid zinc-air battery model was designed and built.Then,a transition metal nitrogen-doped carbon composite was prepared,and its ORR/OER catalytic performance was studied.Finally,it was tested in a solid-state zinc-air battery.The gel electrolyte(PAA)was prepared in acrylic acid,KOH solution,zinc oxide,crosslinking agent and polymerization initiator.The gel electrolyte has good flexibility,water lock and a certain mechanical strength.the ionic conductivity reaches 8.6×10-2 S/cm.The solid-zinc air battery is constructed with zinc sheet,gel and catalyst-laden hydrophobic carbon paper.The battery is wrapped with a gas permeable tape to suppress the loss of moisture in the gel and prolong the battery life.Two batteries are connected in series to allow the LED lamp to operate normally for about 5 hours.Using different MOFs materials(ZIF-67,HKUST-1)as precursors,the transition metal nitrogen-doped carbon composite(Co-Cu/NC and Co-Cu/NC-air)was prepared by different calcination methods.In the 0.1 M KOH electrolyte,the ORR performance of the cobalt-based catalyst is generally good,especially the half-wave potential of Co-Cu(1:0)/NC is 0.825 V(vs.RHE).In the battery discharge test at 2.5 mA,the initial discharge platform of the battery exceeded 1.3 V and the total discharge lasted for 35 hours.The bimetallic composite catalyst exhibits better OER performance.Therefore,Co-Cu(1:1)/NC has excellent ORR and OER catalytic activity.So it is an excellent dual-function electrocatalyst.The battery made with Co-Cu(1:1)/NC was stably operated for 265 cycles in a 5 minute discharge/charge test,and the initial battery efficiency was as high as 70.7%.A series of Co-Ni/NC materials were prepared by high temperature calcination with different proportions of transition metal elements cobalt and nickel.Material characterization shows that these catalysts are nitrogen-doped carbon composites containing metal elements,metal compounds or metal oxides.Electrochemical display of cobalt element enhances the ORR performance of the catalyst,and nickel promotes the OER kinetics of the catalyst.Therefore,Co-Ni(1:1)/NC has the best bifunctional electrocatalytic activity.The capacity of battery made with Co-Ni(1:1)/NC is 142.1 mA h at the current density of 5 mA.And it can work stably for 300 cycle in the 5 minute discharge/charge test,which is more than three times that of precious metal catalysts.