Jun 18, 2020 | |
Graphdiyne as a functional lithium-ion storage material(Nanowerk News) Lithium-ion batteries usually contain graphitic carbons as anode materials. Scientists have investigated the carbonic nanoweb graphdiyne as a novel two-dimensional carbon network for its suitability in battery applications. Graphdiyne is as flat and thin as graphene, which is the one-atomic-layer-thin version of graphite, but it has a higher porosity and adjustable electronic properties. |
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In the journal Angewandte Chemie ("Tuning the Properties of Graphdiyne by Introducing Electron-Withdrawing/Donating Groups"), researchers describe its simple bottom-up synthesis from tailor-made precursor molecules. | |
Carbon materials are the most common anode materials in lithium-ion batteries. Their layered structure allows lithium ions to travel in and out of the spaces between layers during battery cycling, they have a highly conductive two-dimensional hexagonal crystal lattice, and they form a stable, porous network for efficient electrolyte penetration. | |
However, the fine-tuning of the structural and electrochemical properties is difficult as these carbon materials are mostly prepared from polymeric carbon matter in a top-down synthesis. | |
Graphdiyne is a hybrid two-dimensional network made of hexagonal carbon rings bridged by two acetylene units (the "diyne" in the name). Graphdiyne has been suggested as a nanoweb membrane for the separation of isotopes or helium. | |
However, its distinct electronic properties and web-like structure also make graphdiyne suitable for electrochemical applications. Changshui Huang from the Chinese Academy of Sciences, Beijing, and colleagues have investigated the lithium-storage capabilities and electrochemical properties of tailor-made, electronically adjusted graphdiyne derivatives. | |
The scientists synthesized the graphdiyne derivatives in a bottom-up strategy by adding precursor molecules on a copper foil, which self-organized to form ordered layered nanostructures. Using monomers containing functional groups with interesting electronic properties, the authors prepared functional graphdiynes with distinct electrochemical and morphological properties. | |
Among these functional groups, those exerting electron-withdrawing effects reduced the band gap of graphdiyne and increased its conductivity, the authors reported. The cyano group was especially effective and, when used as an anodic material, the cyano-modified graphdiyne demonstrated excellent lithium-storage capacity and was stable for thousands of cycles, as the authors reported. | |
In contrast, when graphdiyne was modified with bulky functional groups (methyl groups) that donate electrons to the graphdiyne network, the authors observed a larger layer spacing, which made the material structure unstable so that the anode only survived a few charge and discharge cycles. | |
The authors also compared both modified graphdiyne materials to an "empty" version where only hydrogen occupied the position of the functional groups in the network. | |
The authors conclude that modified graphdiyne can be prepared by a bottom-up strategy, which is also best suited to build functional two-dimensional carbon material architectures for batteries, capacitors, and other electrocatalytic devices. |
Source: Wiley | |
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