Design And Preparation Of Rechargeable Zn-air Battery Energy Storage Device Based On Bifunctional Nano-electric Catalyst

In this paper,the design and preparation of rechargeable Zn-air battery energy storage device based on bifunctional nano-electric catalyst are studied,and the following two tasks are done:(1)The exploitation of cost-effective,high-active and robust non-precious-metal bifunctional oxygen electrocatalysts for both oxygen reduction reaction(ORR)and oxygen revolution reaction(OER)is the key to promote application of regenerative fuel cells and metal-air batteries.Co9S8 is considered to be a promising non-precious-metal bifunctional oxygen electrocatalysts.However,the electrocatalytic performance of cobalt sulfide-based nanocatalysts is still far from satisfactory because of the poor conductivity,insufficient exposed active sites,and aggregation-prone during continuous work.Herein,based on the inspiration from honeycomb in nature,we designedly synthesized Co9S8/N,S-codoped honeycomb-structured porous carbon(Co9S8/NSC)in-situ composites via a simple method.Benefiting from the unique honeycombed hybrid structure composed of monodisperse Co9S8 nanoparticles in-situ embedded within the three-dimensional interconnected network carbon matrix with high conductivity,which not only facilitates the electron transport and charge transfer across the interface,but also exposure of active sites and rapid transport of ORR/OER-related species,the obtained Co9S8/NSC in-situ composites exhibit a high stability and activity in both ORR in terms of more positive half-wave potential(0.88V)than that(0.86 V)of commercial 20%Pt/C and OER in terms of a small overpotential(0.41V at 10 mA cm-2)approaching to that of commercial IrO2(0.39 V)in alkaline electrolytes.Thus,as expected,the further assembled rechargeable Zn-air batteries based on the bifunctional electrocatalysts exhibit a small discharge/charge overpotential with a high voltaic efficiency of 54.4%,and a long-term cycling stability over 80 h.(2)The rapid development of wearable microelectronics spurs a pressing need for compatible micro-power sources with high energy density and safety.However,current state-of-the-art compact energy storage systems such as micro-supercapacitors(MSCs)and flexible lithium-ion batteries(LIBs)remain far from satisfactory because of insufficient energy density or poor safety.Herein,planar all-solid-state rechargeable micro-Zn-air batteries(PAR-ZABs)are developed with highly-active N-doped core-shell structured Fe/Fe3C@C nanorod-clusters as bifunctional electrocatalysts deposited on interdigital carbon cloth for air cathode,interdigital Zn-foil as metal anode,and well-designed poly(acrylamide-co-acrylic acid)alkaline gel as incombustible solid-state electrolyte.As anticipated,the resultant PAR-ZABs exhibit a competitive areal energy density(12.76 mWh cm"2)and specific energy density(832 Wh kg-1)comparable to MSCs/LIBs,and higher open-circuit-voltage(1.43 V),larger specific capacity(736 mAh g-1),and better cycling stability(120 cycies/40 h at 5 mA cm-2)over most currently reported all-solid-state ZABs based on conventional polyvinyl alcohol alkaline gel electrolyte.More importantly,the employed more rational in-plane electrode configuration gurantees good integration capability,ensuring the enhancement of output voltage/current in practical application with arbitrary group of the PAR-ZABs in series/parallel interconnection.In addition,benefiting from the excellent mechanical properties of solid polymer electrolyte,the PAR-ZABs acquire additionally excellent flexibility,performing steadily under bending deformation in both concave and convex shapes.Most notably,the excellent flexibility combined with intrinsic safety of hydrogel electrolyte endow the PAR-ZABs outstanding wearability.Eventually,a smart watch powered by integrated PAR-ZABs watchband is demonstrated,showing great potential for on-chip flexible energy storage in wearable applications.