Anhydride-Based Compound with Tunable Redox Properties as Advanced Organic Cathodes for High-Performance Aqueous Zinc-Ion Batteries

DNA-inspired design of organic electrode materials for high-performance aqueous Zn-ion batteries

Inspired by the DNA structure, we design and synthesize a novel, fully conjugated small organic molecule (HAT-NQ) through the modular assembly of benzene rings, pyrazine, 1,4-dihydropyrazine, and 1,4-benzoquinone. Leveraging the synergistic effect of these building blocks, HAT-NQ exhibits exceptional electrochemical performance in aqueous Zn-ion batteries.

A new polymer with rich carbonyl delocalized π-conjugated structure for high-performance aqueous zinc ion batteries

The development of sustainable and clean energy has become a top priority, driven by global carbon peaking and carbon neutrality targets. Organics are widely used in aqueous zinc ion batteries (AZIBs) due to their environmental friendliness, high structural designability, and safety. However, organic materials often face some challenges, including high solubility, low specific capacity, and unclear mechanism, which hinder its further applications. In this paper, two new conjugated organic polymers were synthesized as cathodes for AZIBs by molecular structure design. Notably, the introduction of new actives (C = O) in (poly-(tetraamino-p-benzoquinone-alt-2,5-dihydroxy-1,4-benzoquinone, DHTA) along with the extension of the π-π conjugated structure to form polymers is conducive to the improvement of the specific capacity and reversibility of AZIBs compared to (poly-(1,2,4,5-tetraaminobenzene-alt-2,5-dihydroxy-1,4-benzoquinone, DHPH). The DHTA cathode delivers high initial specific capacity of 282.5 mAh/g at a current of 0.05 A/g and excellent rate performance (56.8 mAh/g at 5 A/g). The excellent rate performance and long cycle life of the as synthesized DHTA can be attributed to the low solubility, extended π-conjugated structure and enhanced electronic conductivity, which result from the polymerization with the introduction of carbonyl groups into organic skeleton. Moreover, the mechanism of Zn2+ storage in DHTA is also explored by various ex-situ characterization techniques and density-functional theory (DFT) calculations. In each repeating unit, DHTA can store two Zn2+ while transferring four electrons to form a stable O⋯Zn⋯N coordination. This work provides a molecular engineering strategy for organic materials, revealing their potential application in zinc ion batteries.

Imide Polymers with Bipolar-Type Redox-Active Centers for High-Performance Aqueous Zinc Ion Battery Cathodes and Electrochromic Materials

Aqueous zinc-ion batteries (AZIBs) have attracted interest for their low cost and environmental friendliness. Two bipolar organic materials with different degrees of conjugation, pPMQT and pNTQT, were rationally designed and synthesized as cathode candidates for AZIBs based on 4,4'-diaminotriphenylamine (TPA), 2,7-diaminoanthraquinone (AQ), and two anhydrides. This molecular design features an increased conjugation and electron cloud density, thereby improving charge transport kinetics, specific capacity, and cycling stability. In comparison with pPMQ and pNTQ (n-type), pPMQT and pNTQT demonstrate better electrochemical characteristics. In this work, pNTQT shows outstanding performance. It exhibits an initial capacity of 349.79 mAh g-1 at 0.1 A g-1 and retains a specific capacity of 190.25 mAh g-1 (87.6%) after 5000 cycles at 5 A g-1. In comparison, pNTQ demonstrates a specific capacity of only 207.55 mAh g-1 at 0.1 A g-1, and after 5000 cycles at 5 A g-1, its capacity retention rate is only 81.2%. At the same time, both pPMQT and pNTQT polymer films demonstrate attractive electrochromic (EC) properties, displaying reversible color transitions from yellow to dark blue in the UV-visible spectrum. This work lays the foundation for the further development of triphenylamine-based polyimide materials for application in AZIBs and electrochromism.

Using -NH and -OH rich organic cathodes to explore proton transport in aqueous zinc-ion batteries

An organic cathode material for zinc-ion batteries shows a reliable proton transport mechanism. It uses a pyrazine ring as the energy storage unit and H+ as the shuttle ion, enabling high functionality utilization with rapid redox kinetics.

A carbonyl-rich conjugated organic compound for aqueous rechargeable Na+ storage with wide voltage window workability

Organic compounds have become an important electrode material for aqueous electrochemical energy storage. However, organic electrodes still face poor performance in aqueous batteries due to insufficient electrochemical activity. In this work, a novel conjugated quinone compound containing a rich carbonyl group was designed. The quinone compound was synthesized by a simple dehydration reaction of pyrene-4,5,9,10-tetrone (PTO) and 1,2-diaminoanthraquinone (1,2-AQ); it contains 4 pyrazines (CN) from AQ and 4 carbonyl groups (CO), as well as a large number of active sites and the excellent conductivity brought by its conjugated structure ensures the high theoretical capacity of PTO-AQ. In the context of aqueous sodium ion batteries (ASIBs), the electrode material known as PTO-AQ exhibits a notable reversible discharge capacity of 117.9 mAh/g when subjected to a current density of 1 A/g; impressively, it maintained a capacity retention rate of 74.3 % even after undergoing 500 charge and discharge cycles, a performance significantly surpassing that of pristine PTO and AQ. Notably, PTO-AQ exhibits a wide operating voltage range (-1.0-0.5 V) and a cycle life of up to 10,000 cycles. In situ Raman and ex situ measurements were used to analyze the structural changes of PTO-AQ during charge and discharge and the energy storage mechanism in NaAC. The effective promotion of Na+ storage brought by a rich carbonyl group was obtained. The structural energy level and electrostatic potential of PTO-AQ were calculated, and the active center distribution of PTO-AQ was obtained. This work serves as a guide for designing high-performance aqueous organic electrode materials that operate across a wide voltage range while also explaining their energy storage mechanism.