Investigations on the electrochemical behaviors of hexaazatriphenylene derivative as high-performance electrode for 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.

Design and synthesis of п-conjugated aromatic heterocyclic materials with dual active sites and ultra-high rate performance for aqueous zinc-organic batteries

Acid anhydride cathode materials garner considerable interest for aqueous zinc ion batteries (AZIBs) due to ideal specific capacity and structural diversity, however, serious solubility leads to capacity degradation. Herein, 1,4,5,8-naphthalene tetracarboxylic acid dianhydride - 2,3-diamino phenothiazine (NTDP) featuring multiple active sites (6 with CN and 2 with CO) and large π-conjugated backbone, was designed and synthesized utilizing solid-phase method. The smallest energy gap (ΔE) and the lowest LUMO levels (against monomers) induced by multiple active sites and п-conjugated backbone with high aromaticity, NTDP exhibited excellent specific capacity (307.5 mA h g-1 under 0.05 A/g), ultrahigh rate performance (194.9 mA h g-1 under 20 A/g) and impressive cycling stability (190.0 mA h g-1 over 9000 cycles with a capacity retention of 91.2 % at 15 A/g). The reversible Zn2+ insertion/removal mechanism on multiple active centers (CO and CN) was proposed through XPS, FT-IR, and Raman. The specific capacity of the NTDP//zinc flexible cell was 112.6 mA h g-1 at 3 A/g under various folding angles (45°, 90°, 135°, and 180° bends), suggesting its practical potential for flexible devices. This work will offer opportunities for the rational design of battery structures.

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

Organic materials with multiple active sites and flexible structural designs are becoming popular for use in aqueous zinc-ion batteries (AZIBs). However, their applicability is limited due to the low specific capacity and poor cycle stability originating from the introduction of inactive units and high solubility. Herein, three organic molecules with tunable redox properties were synthesized using anhydride (PMDA, 1,2,4,5-benzenetetracarboxylic anhydride-1,2-diaminoanthraquinone, NTCDA, 1,4,5,8-naphthalenetetracarboxylic dianhydride-1,2-diaminoanthraquinone, and PTCDA, 3,4,9,10-perylenetetracarboxylic dianhydride-1,2-diaminoanthraquinone, referred to as PM12, NT12, and PT12) in the solid-phase method. Density functional theory (DFT) simulations and experiments identified that NT12 exhibits superior electrochemical performance compared with PM12 and PT12 because of the low energy gap and large aromatic conjugated structure. They demonstrated specific capacities of 106.7, 192.9, and 124.9 mA h g-1 at 0.05 A g-1, respectively. Especially, NT12 displayed excellent initial specific capacity (85.4 mA h g-1 at 1 A g-1) and remarkable capacity retention (64.1% for 3000 cycles) due to dual active centers (C═N and C═O). The all-NT12 full-cell also had excellent performance (127.1 mA h g-1 under 1 A g-1 and 80.6% over 200 cycles). The organic compounds synthesized in this work have potential applications of AZIBs, highlighting the importance of molecular design to develop the next generation of advanced materials.

Electrochemical Performance and Mechanism of Bimetallic Organic Framework for Advanced Aqueous Zn Ion Batteries

Widespread interest has been generated by aqueous zinc batteries (AZIBs), which have excellent theoretical capacities (820 mA h g-1), a low redox potential (-0.76 V vs SHE of Zn metal), and high security. Suitable cathodes for constructing high performance AZIBs are of great signification. Metal-organic frameworks (MOFs) with adjustable structure via metals and organic units show great potential in AZIBs. In this work, ZnMn-Squaric acid (ZnMn-SQ) was synthesized using squaric acid through coprecipitation and served as the cathode for AZIBs. The ZnMn-SQ electrode demonstrated a high capacity of 489.1 mA h g-1 at 0.2 A g-1. Meanwhile, ZnMn-SQ can obtain 80.7 mA h g-1 after 1300 cycles, showing an outstanding long cycle life. More importantly, ex situ characterizations of XRD, XPS, and FT-IR revealed that ZnMn-SQ undergoes a structural transformation from the initial ZnMn-SQ framework to manganese oxide accompanied by Zn-SQ and then reduced to MnOOH, ZnMn2O4, and Zn4SO4(OH)6·5H2O (ZHS) in subsequent cycles. In addition, a modified zinc anode using cubic porous Zn-SQ-3d was used to construct ZnMn-SQ // Zn-SQ-3d@Zn(Zn-SQ-3d-coated Zn) high performance AZIBs, the capacity of which reaches 171.3 mA h g-1 at 1 A g-1 after 660 cycles. This work provided chances for constructing high-performance zinc ion batteries using MOF compounds.