ABSTRACT
Gel polymer electrolyte (GPE) in quasi-solid state Zn-air battery (QSZAB) will release alkali during cycling, resulting in gradual dehydration of GPE, corrosion of Zn electrode, Zn dendrites growth, and therefore inferior performance. Here, hollow Sn microspheres are prepared on Zn substrate by the technique of colloidal self-assembly. The inner surfaces of hollow Sn microspheres are modified by 2-hydroxypropyl-ß-cyclodextrin (hollow Sn-inner HPßCD) to regulate the released alkali at GPE|anode interface. The hollow Sn-inner HPßCD can lessen the leakage of released alkali, make stored alkali diffuse back to GPE during the charging process, and mitigate the loss of soluble Zn(OH)4 2- to suppress Zn dendrites growth. Resultantly, GPE in QSZAB with hollow Sn-inner HPßCD exhibits a high retention capacity for alkaline solution. The cell also exhibits a long cyclic lifespan of 127 h due to the effective regulation of released alkali, which outperforms QSZAB without hollow Sn-inner HPßCD by 7.94 times. This work rivets the regulation of released alkali at GPE|anode interface, providing new insight to improve QSZABs' performance.
ABSTRACT
Metal single atoms show outstanding electrocatalytic activity owing to the abundant atomic reactive sites and superior stability. However, the preparation of single atoms suffers from inexorable metal aggregation which is harmful to electrocatalytic activity. Here, ionic covalent organic frameworks (iCOFs) are employed as the sacrificial precursor to mitigate the metal aggregation and subsequent formation of bulky particles. Molecular dynamics simulation shows that iCOFs can trap and confine more Co ions as compared to neutral COFs, resulting in the formation of a catalyst composed of Co single atoms and uniformly distributed Co nanoparticles (CoSA &CoNP-10 ). However, the neutral COFs derive a catalyst composed of Co atomic clusters and large Co nanoparticles (CoAC &CoNP-25 ). The CoSA &CoNP-10 catalyst exhibits higher oxygen bifunctional electrocatalytic activities than CoAC &CoNP-25 , coinciding with the density functional theory results. Taking the CoSA &CoNP-10 as the air cathode in Zn-air batteries (ZABs), the aqueous ZAB presents a high power density of 181 mW cm-2 , a specific capacity of 811 mAh g-1 as well as a long cycle life of 407 h at a current density of 10 mA cm-2 , while the quasi-solid state ZAB displays a power density of 179 mW cm-2 and the cycle life of 30 h.
