A Redox-Active 2-D Covalent Organic Framework as a Cathode in an Aqueous Mixed-Ion Electrolyte Zn-Ion Battery: Experimental and Theoretical Investigations

Venkatesha, A and Gomes, R and Nair, AS and Mukherjee, S and Bagchi, B and Bhattacharyya, AJ (2022) A Redox-Active 2-D Covalent Organic Framework as a Cathode in an Aqueous Mixed-Ion Electrolyte Zn-Ion Battery: Experimental and Theoretical Investigations. In: ACS Sustainable Chemistry and Engineering, 10 (19). pp. 6205-6216.

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Abstract

We demonstrate here a simple alternative strategy of developing a stable and long-lived aqueous Zn-ion battery. The battery comprises a redox-active anthraquinone-based covalent organic framework (COF) and a graphene oxide composite (COF-GOPH) as the cathode, zinc metal as the anode, and a mixed-ion electrolyte with varying proportions of zinc and lithium ions. This cell configuration contrasts with those of conventional organic batteries with aqueous electrolytes having a single type of cation. Our findings convincingly show that an optimal Li+ to Zn2+ ion ratio is beneficial for Zn2+-ion diffusion into the COF. The energy storage mechanism is found to be due to the Zn2+-ion intercalation/deintercalation into the COF with simultaneous reversible redox activity of the framework carbonyl and imine moieties. Additionally, a theoretical analysis of the radial distribution function reveals the preferential insertion of Zn2+-ions along with its partial solvation shell into the framework, leading to an optimal coordination of Zn2+ with oxygen and nitrogen moieties of the COF network. On the other hand, the Li+ ions preferentially reside in solution. Irrespective of the electrolyte composition, the composite electrode COF-GOPH performs better than the COF. The best battery performance is obtained with the COF-GOPH in the presence of 0.5 M ZnSO4 and 0.5 M Li2SO4 electrolyte. The cell shows excellent cyclability and superior capacity with 82 retention even after 500 cycles (from the second cycle onwards). Our studies also reveal a Li+-ion-assisted pseudocapacitance mechanism that is partially responsible for the enhancement in the electrochemical performance in the mixed-ion electrolytes. © 2021 American Chemical Society.

Item Type:	Journal Article
Publication:	ACS Sustainable Chemistry and Engineering
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to the American Chemical Society.
Keywords:	Cathodes; Distribution functions; Graphene; Ions; Ketones; Lithium compounds; Lithium-ion batteries; Redox reactions; Solvation; Zinc; Zinc compounds, Aqueous zn-ion battery; Covalent organic frameworks; Ion batteries; Li +; Mixed-ion; Mixed-ion electrolyte; Organic electrodes; Potential mean forces; Radial distribution functions; Zn 2+; Zn ions; Zn2+/li+solvation, Electrolytes
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	29 May 2022 07:27
Last Modified:	29 May 2022 07:27
URI:	https://eprints.iisc.ac.in/id/eprint/72759

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