Two-dimensional carbon networks
Graphdiyne as a functional lithium-ion storage material

Date:
June 18, 2020
Source:
Wiley
Summary:
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. Researchers now describe its simple bottom-up synthesis
from tailor-made precursor molecules.



FULL STORY ========================================================================== 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. In the journal Angewandte Chemie, 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.


========================================================================== Story Source: Materials provided by Wiley. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Chipeng Xie, Xiuli Hu, Zhaoyong Guan, Xiaodong Li, Fuhua Zhao, Yuwei
Song, Yuan Li, Xiaofang Li, Ning Wang, Changshui Huang. Tuning the
Properties of Graphdiyne by Introducing Electron‐Withdrawing/
Donating Groups. Angewandte Chemie International Edition, 2020;
DOI: 10.1002/anie.202004454 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200618102412.htm

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