Elaborate molecular design on cathodes is of great importance for rechargeable aqueous zinc-organic batteries' performance elevation. Herein, we design a novel orthoquinone-based covalent organic framework with an ordered channel structures (BT-PTO COF) cathode for an ultrahigh performance aqueous zinc-organic battery. The ordered channel structure facilitates ions transfer and makes the COF follow a redox pseudocapacitance mechanism. Thus, it delivers a high reversible capacity of 225 mAh g À 1 at 0.1 A g À 1 and an exceptional long-term cyclability (retention rate 98.0 % at 5 A g À 1 ( � 18 C) after 10 000 cycles). Moreover, a co-insertion mechanism with Zn 2 + first followed by two H + is uncovered for the first time. Significantly, this co-insertion behaviour evolves to more H + insertion routes at high current density and gives the COF ultra-fast kinetics thus it achieves unprecedented specific power of 184 kW kg À 1 (COF) and a high energy density of 92.4 Wh kg À 1 (COF) . Our work reports a superior organic material for zinc batteries and provides a design idea for future high-performance organic cathodes.
High‐capacity small organic materials are plagued by their high solubility. Here we proposed constructing hydrogen bond networks (HBN) via intermolecular hydrogen bonds to suppress the solubility of active material. The illustrated 2, 7‐ diamino‐4, 5, 9, 10‐tetraone (PTO‐NH2) molecule with intermolecular hydrogen (H) bond between O in −C=O and H in −NH2, which make PTO‐NH2 presents transverse two‐dimensional extension and longitudinal π–π stacking structure. In situ Fourier transform infrared spectroscopy (FTIR) has tracked the reversible evolution of H‐bonds, further confirming the existence of HBN structure can stabilize the intermediate 2‐electron reaction state. Therefore, PTO‐NH2 with HBN structure has higher active site utilization (95 %), better cycle stability and rate performance. This study uncovers the H‐bond effect and evolution during the electrochemical process and provides a strategy for materials design.
Elaborate molecular design on cathodes is of great importance for rechargeable aqueous zinc-organic batteries' performance elevation. Herein, we design a novel orthoquinone-based covalent organic framework with an ordered channel structures (BT-PTO COF) cathode for an ultrahigh performance aqueous zinc-organic battery. The ordered channel structure facilitates ions transfer and makes the COF follow a redox pseudocapacitance mechanism. Thus, it delivers a high reversible capacity of 225 mAh g À 1 at 0.1 A g À 1 and an exceptional long-term cyclability (retention rate 98.0 % at 5 A g À 1 ( � 18 C) after 10 000 cycles). Moreover, a co-insertion mechanism with Zn 2 + first followed by two H + is uncovered for the first time. Significantly, this co-insertion behaviour evolves to more H + insertion routes at high current density and gives the COF ultra-fast kinetics thus it achieves unprecedented specific power of 184 kW kg À 1 (COF) and a high energy density of 92.4 Wh kg À 1 (COF) . Our work reports a superior organic material for zinc batteries and provides a design idea for future high-performance organic cathodes.
Large‐scale energy storage with aqueous Zn batteries (AZBs) have bright future, but their practical application is impeded by H2 evolution reaction (HER), which results in poor stability of Zn–metal anodes. Here, using linear sweep voltammetry in dilute salt aqueous electrolytes, it is discovered that as the salt concentration decreases, HER is gradually suppressed, which is contrary to prior beliefs. Combining calculations and experiments, it is demonstrated that HER derives predominantly from the sum of Zn2+‐solvated water rather than the average amount of water in the Zn2+‐solvation structural unit or free water without interaction with Zn2+, which answers the puzzle from above. This result, which differs fundamentally from the previous understandings, sheds new light on the mysterious role of water chemistry in controlling HER and contributes to a more rational design of advanced electrolytes for AZBs.
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