Lithium ion batteries usually use graphite-based carbon materials as negative electrode materials. According to foreign media reports, scientists are studying the applicability of a new type of two-dimensional carbon network, namely carbon nanofiber membrane graphite diacetylene, in battery applications.
Graphdiyne is as flat and thin as graphene (graphene is monoatomic graphite), but the porosity is higher and the electronic properties can be adjusted. According to the researchers, this material can be prepared using specially prepared precursor molecules and a simple bottom-up synthesis method.
In lithium-ion batteries, carbon materials are the most common anode materials. During the battery cycle, benefiting from the layered structure of the carbon material, lithium ions can enter and exit the interlayer space, and such materials have a highly conductive two-dimensional hexagonal lattice, which can form a stable porous network and effectively penetrate the electrolyte . However, most of the carbon materials are prepared from polymer carbon materials through a top-down synthesis method. Therefore, it is difficult to fine-tune the structure and electrochemical performance.
Graphdiyne is a mixed two-dimensional network composed of hexagonal carbon rings connected by two acetylene units. Graphdiyne is considered to be a nanofiber network membrane that can be used to separate isotopes or helium. However, due to its unique electronic properties and network structure, it is suitable for electrochemical applications. Changshui Huang of the Chinese Academy of Sciences and colleagues studied the lithium storage capacity and electrochemical performance of graphidiyne derivatives regulated by specific electrons.
Scientists synthesized graphidiyne derivatives in a bottom-up manner by adding precursor molecules to copper foil, in which copper foil self-organized to form ordered layered nanostructures. Using functional monomers with interesting electronic properties, the functional graphadiyne prepared has unique electrochemical and morphological properties. According to reports, among these functional groups, those with electron-withdrawing effect can reduce the band gap of graphite diacetylene and improve the electrical conductivity. The cyano group is particularly effective. When used as a negative electrode material, graphidiene adjusted by cyano group shows excellent lithium storage capacity, and can maintain stable performance after thousands of cycles.
In contrast, the researchers found that by adjusting the graphidiyne through a large number of methyl functional groups, the functional group can provide electrons to the graphidiene network, making the interlayer spacing larger, resulting in unstable material structure. In this case, the anode material can only withstand a few charge and discharge cycles. The researchers also compared the two modified graphite diacetylene materials with an "empty" material in which only hydrogen occupies functional group positions.
The researchers said that the modified graphite diyne can be prepared by a bottom-up method. This strategy is also very suitable for the construction of functional two-dimensional carbon material structures for batteries, capacitors and other electrocatalytic devices. (Elisha)
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