Abstract
With the increased application of batteries in powering electric vehicles as well as potential contributions to utility-scale storage, there remains a need to identify and develop efficient and sustainable active materials for use in lithium (Li)- and sodium (Na)-ion batteries. Organic cathode materials provide a desirable alternative to inorganic counterparts, which often come with harmful environmental impact and supply chain uncertainties. Organic materials afford a sustainable route to active electrodes that also enable fine-tuning of electrochemical potentials through structural design. Here, we report a bis-anthraquinone-functionalized s-indacene-1,3,5,7(2H,6H)-tetraone (BAQIT) synthesized using a facile and inexpensive route as a high-capacity cathode material for use in Li- and Na-ion batteries. BAQIT provides multiple binding sites for Li- and Na-ions, while maintaining low solubility in commercial organic electrolytes. Electrochemical Li-ion cells demonstrate excellent stability with discharge capacities above 190 mAh g–1 after 300 cycles at a 0.1C rate. The material also displayed excellent high-rate performance with a reversible capacity of 142 mAh g–1 achieved at a 10C rate. This material affords high power capabilities superior to current state-of-the-art organic cathode materials, with values reaching 5.09 kW kg–1. The Na-ion performance was also evaluated, exhibiting reversible capacities of 130 mAh g–1 after 90 cycles at a 0.1C rate. This work offers a structural design to encourage versatile, high-power, and long cycle-life electrochemical energy-storage materials.
Highlights
There is an increasing demand for energy-storage solutions that deliver the required energy and power densities for an application and provide more versatile, lighter, environmentally sustainable, and economically viable approaches.[1−6] Lithium-ion (Li-ion) batteries deliver high energy and power densities, making them the preferred technology for portable electronics and electric vehicles.[7−12] Relying typically on inorganic intercalation-type cathodes,[13−16] theoretical energy densities are limited by the number of redox-active sites available, and capacities are typically on the order of ∼200 mAh g−1
In order to prove the low solubility of BAQIT, we have checked the solubility of BAQIT in dimethoxyethane (DME) and a mixture of ethylene carbonate (EC) with dimethylcarbonate (DMC) and compared it with anthraquinone (AQ) and the core indacene tetraone (IT)
Six carbonyl groups are involved in the redox reaction in the studied potential range of 1.5−3.5 V, with the first of the redox peaks representing the reduction of the four carbonyl groups of the anthraquinone units, while the second redox peak represents the reduction of the two carbonyl groups of the core moiety.[42]
Summary
There is an increasing demand for energy-storage solutions that deliver the required energy and power densities for an application and provide more versatile, lighter, environmentally sustainable, and economically viable approaches.[1−6] Lithium-ion (Li-ion) batteries deliver high energy and power densities, making them the preferred technology for portable electronics and electric vehicles.[7−12] Relying typically on inorganic intercalation-type cathodes,[13−16] theoretical energy densities are limited by the number of redox-active sites available, and capacities are typically on the order of ∼200 mAh g−1. Organic materials present an enticing prospect where a tunable molecular structure and high structural diversity affords advantages over inorganic counterparts.[22−31] Organic cathode materials may comprise a range of materials, including small molecules, polymers, and covalent organic frameworks.[32,33] Electrochemical performance can be fine-tuned through judicious choice of functional groups that contain light elements and potential group I binding sites, allowing for high energy density and flexibility. We demonstrate that by attaching two anthraquinone units to the central s-indacene-1,3,5,7(2H,6H)-tetraone core, a large elongated planar structure is formed. This affords several Liand Na-ion binding sites while simultaneously ensuring its intractability in common liquid electrolytes, which is desirable for mitigating dissolution issues during cycling. Article investigated the sequential binding mechanism of Li+ and Na+ ions and subsequent structural transformation of BAQIT using density functional theory (DFT) calculations and elucidated its promising cycling performance in Li- and Na-ion half-cells
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