Regulation of two-dimensional nanomaterials: New driving force for lithium-ion batteries
Li-ion batteries (LIBs) are attractive as the major energy storage devices due to their higher specific energy density, lower self-discharge, and lower memory effect. Among the components of batteries, electrode materials play a key role in enhancing electrochemical properties. Thus, the development of advanced electrode materials for high-performance LIBs has been the major objective in the related research fields.
Two-dimensional (2D) nanomaterials, including graphene, transition metal oxide (TMO) nanosheets, transition metal dichalcogenide (TMD) nanosheets, etc., are composed of one or several monolayers of atoms (or unit cells). They have been paid much attention in recent years, due to their outstanding physical and chemical properties in contrast to their bulk counterparts. The integration of 2D nanomaterials with energy storage devices could provide promising opportunities to overcome the major challenges driven by ever-growing global energy demands. Unfortunately, the direct use of these sheet-like materials has met with numerous challenges, such as serious self-agglomerating tendency, relatively low conductivity and the obvious volume changes over repeated charging-discharging cycles.
In a new review paper published in National Science Review, scientists from Australia at Queensland University of Technology and University of Wollongong summarized recent progress on the strategies for enhancing the lithium storage performance of 2D nanomaterials. These strategies for manipulating the structures and properties are expected to meet the major challenges for advanced nanomaterials in energy storage applications. Co-authors Jun Mei, Yuanwen Zhang, Ting Liao, Ziqi Sun and Shi Xue Dou classified these strategies into three primary strategies, including hybridization with conductive materials, surface/edge functionalization, and structural optimization.
"The strategy of hybridization is the most common and widely studied one for TMOs/TMDs-based nanocomposites, in which some conductive nanostructures, e.g. nano-carbon, carbon nanotubes (CNTs), graphene, organic polymers, metallic nanoparticles, etc., are introduced to hybridize with TMO/TMD nanosheets to improve the overall conductivity and accommodate the volume expansion of metal oxide or sulfide nanomaterials during the repeated charging/discharging cycles." they state.
"The second strategy is edge/surface functionalization, which can be achieved by atom/ion doping or defect engineering at the edges or on the surfaces of the 2D nanomaterials. The implantation of heteroatoms or ions into 2D nanomaterials helps to modulate the electronic structure, the surface chemical reactivity, or the interlayer spacing of the 2D nanomaterials, and further enhances the lithium ions storage capacity," they add. "The third strategy of structure optimization is often realized by controlling some structural parameters during fabrication, such as thickness, size, pores, or surface morphology, which have significant impacts on the structure-dependent properties and the electrochemical performance, and are beneficial for alleviating the inevitable self-restacking and exposing more active sites."
The scientists believe "these effective strategies for improving the lithium storage of 2D nanomaterials will be good reference points for scientists and researchers in the related fields of materials, chemistry, and nanotechnology, who are looking forward to developing superior next-generation rechargeable batteries".
See the article: Jun Mei, Yuanwen Zhang, Ting Liao, Ziqi Sun and Shi Xue Dou
Strategies for improving the lithium storage performance of 2D nanomaterials
Natl Sci Rev (July 2017)
The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.
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