RESUMO
Covalent organic framework (COF) materials, known for their robust porous character, sustainability, and abundance, have great potential as cathodes for aqueous Zn-ion batteries (ZIBs). However, their application is hindered by low reversible capacity and discharge voltage. Herein, a donor-acceptor configuration COF (NT-COF) is utilized as the cathode for ZIBs. The cell exhibits a high discharge voltage plateau of ≈1.4 V and a discharge capacity of 214 mAh g-1 at 0.2 A g-1 when utilizing the Mn2+ electrolyte additive in the ZnSO4 electrolyte. A synergistic combination mechanism is proposed, involving the deposition/dissolution reactions of Zn4SO4(OH)6·4H2O and the co-(de)insertion reactions of H+ and SO4 2- in NT-COF. Meanwhile, the NT-COF with a donor-acceptor configuration facilitates efficient generation and separation of electron-hole pairs upon light exposure, thereby enhancing electrochemical reactions within the battery. This leads to a reduction in charging voltage and internal overvoltage, ultimately minimizing electricity consumption. Under ambient weather conditions, the cell exhibits an average discharge capacity of 430 mAh g-1 on sunny days and maintains consistent cycling stability for a duration of 200 cycles (≈19 days) at 0.2 A g-1. This research inspires the advancement of Zn-organic batteries for high-energy-density aqueous electrochemical energy storage systems or photo-electrochemical batteries.
RESUMO
Covalent organic frameworks (COFs) are considered as promising candidate organic electrode materials for lithium-ion batteries (LIBs) because of their relatively high capacity, ordered nanopores, and limited solubility in electrolyte. However, the practical capacity of COF materials is mainly affected by their low electronic/ionic conductivity and the deep-buried active sites inside the COFs. Here, we synthesize an iodine doped ß-ketoenamine-linked COF (2,6-diaminoanthraquinone and 1,3,5-triformylphloroglucinol, denoted as COF-I) by a facile one-pot solvothermal reaction. The introduction of iodine can make the COF more lithiophilic inside and exhibit high intrinsic ion/electron transport, ensuring more accessible active sites of the COFs. Consequently, when used as the cathode of LIBs, COF-I demonstrates a high initial discharge capacity of 140 mA h g-1 at 0.2 A g-1, and excellent cycling stability with 92% capacity retention after 1000 cycles. Furthermore, a reversible capacity of 95 mA h g-1 at 1.0 A g-1 is also achieved after 300 cycles. Our study provides a facile way to develop high-performance COF electrode materials for LIB applications.
RESUMO
Li-organic batteries (LOBs) are promising advanced battery systems because of their unique advantages in capacity, cost, and sustainability. However, the shuttling effect of soluble organic redox intermediates and the intrinsic dissolution of small-molecular electrodes have hindered the practical application of these cells, especially under high operating temperatures. Herein, a cross-linked membrane with abundant negative charge for high-temperature LOBs is prepared via electrospinning of poly(vinyl alcohol) containing halloysite nanotubes (HNTs). The translocation of negatively charged organic intermediates can be suppressed by the electronic repulsion and the cross-linked network while the positively charged Li+ are maintained, which is attributed to the intrinsic electronegativity of HNTs and their well-organized and homogeneous distribution in the PVA matrix. A battery using a PVA/HNT composite separator (EPH-10) and an anthraquinone (AQ) cathode exhibits a high initial discharge capacity of 231.6 mAh g-1 and an excellent cycling performance (91.4% capacity retention, 300 cycles) at 25 °C. Even at high temperatures (60 and 80 °C), its capacity retention is more than 89.2 and 80.4% after 100 cycles, respectively. Our approach demonstrates the potential of the EPH-10 composite membrane as a separator for high-temperature LOB applications.
