Organic Cathode for Aqueous Zn-Ion Batteries: Taming a Unique Phase Evolution toward Stable Electrochemical Cycling

Abstract

Aqueous zinc batteries are highly attractive for large-scale storage applications owing to their inherent safety, low-cost, and durability. Yet, their advancement is hindered by a dearth of positive host materials (cathode) due to sluggish diffusion of Zn 2+ inside solid inorganic frameworks. Here, we report a novel organic host, tetrachloro-1,4-benzoquinone (also called: p-Chloranil), which due to its inherently soft crystal structure can provide reversible and efficient Zn 2+ storage. It delivers a high capacity of ≥200 mAh g-1 with a very small voltage polarization of 50 mV in a flat plateau around 1.1 V, which equate to an attractive specific energy of > 200 Wh kg-1 at an unparalleled energy efficiency (~95%). As unraveled by density functional theory (DFT) calculations, the molecular columns in p-Chloranil undergo a twisted rotation to accommodate Zn 2+ , thus restricting the volume change (-2.7%) during cycling. In-depth characterizations using operando X-ray

Covalent–Organic Frameworks: Advanced Organic Electrode Materials for Rechargeable Batteries

“…Recently, some organic molecular materials have been investigated in AZBs. [ 136,137 ] Assembled by the intermolecular van der Waals forces, organic materials imposed a modest Coulombic repulsion for the Zn 2+ migration. To ensure a facilitated entry of Zn 2+ , molecular reorientation is permitted in the soft lattice structure under the electrochemical environment, which is a critical mechanism to accommodate various ions.…”

“…To ensure a facilitated entry of Zn 2+ , molecular reorientation is permitted in the soft lattice structure under the electrochemical environment, which is a critical mechanism to accommodate various ions. [ 137 ] To fill the gap of polymeric materials, hydroquinone‐linked β‐ketoenamine COF (HqTp) is employed as a cathode to accommodate the electrophilic Zn 2+ ions for the first time ( Figure 16 a). [ 138 ] The crystalline honeycomb porous structure presents a migration pathway for Zn 2+ ions.…”

Recent Progress in Multivalent Metal (Mg, Zn, Ca, and Al) and Metal‐Ion Rechargeable Batteries with Organic Materials as Promising Electrodes

“…In the pursuit of high‐performance organic materials, carbonyl‐containing compounds (e.g., redox‐active quinones, anhydrides, and imides) have recently attracted intensive research interest . Carbonyl compounds could be easily designed with multielectron redox characteristics, and they have been demonstrated to show high structural stability through either the coordination method to accommodate alkali monovalent metal ions or the intermolecular interaction to accommodate multivalent metal ions . Advantages of carbonyl compounds including fast redox capability, good structural stability, and high storage endow organic batteries with outstanding performance .…”

“…SEM characterization of p ‐chloranil electrode at the e) pristine, f) discharged, and g) charged states. Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…Since most of organic electrode materials, particularly polymers, are in their amorphous states and do not show good crystallinity, the structural change of organic crystals upon Zn 2+ insertion becomes a challenging topic. Recently, the phase transformation of an organic crystal tetrachloro‐1,4‐benzoquinone ( p ‐chloranil) 28 was investigated . Pristine p ‐chloranil 28 initially formed a film (Figure e) by coating onto the mesoporous carbon additives through a nanoconfinement strategy, which could afford improved electrochemical performance.…”