In the field of surface science, the design and optimization of the surface electrochemical active sites always is the hot research on catalyst and battery. Today and tomorrow's technologies call for effective high energy storage devices. Lithium-sulfur batteries hold promise for meeting these high energy needs. Lithium-sulfur (Li-S) batteries provide a high energy density, while being low cost and environmentally friendly. But there are still some challenges to be overcome before Li-S batteries can be widely used in practical applications. A team of researchers working in China and Canada has proposed an atomic terminated concept to design the facet via single-crystal architecture for Li-S batteries. Their concept harvests high-density/efficient surface active sites, where the chemical reaction takes place, to significantly boost the electrocatalyst performance of Li-S batteries.
The research team published their findings on May 31, 2022, in the journal Nano Research. (DOI 10.1007/s12274-022-4381-8)
Scientists have been working with Li-S batteries for several decades, in efforts to solve the hurdles that need to be overcome in order for these batteries to be more practically useful. The sluggish oxidation-reduction reactions (redox) of polysulfides results in high polarization and severe shuttle effect. Therefore, the electrochemical catalytic active sites on the surface are needed to tailor for enhancing the polysulfides conversion and performance of Li-S batteries.
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"Bluk phase of materials generally are easily to understand, oppositely the surface of materials are very puzzle and fascinating." said Weitao Zheng, scientist in film and energy field, Jilin University. During film filed, H-terminated diamond exhibits very unique surface electronic performance. Consequently, focusing on electrochemical filed, we urgently want to exploit this type structure-function relationship for Li-S battery by only altering surface matrix of one or two layered atoms.
"Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries, which are extremely dependent on the surface structure and chemical state," said Dong Wang, College of Chemistry and Chemical Engineering, Hunan University. Recently, scientists have studied single-atom concepts to unlock a route that maximizes the use of surface-active atoms. However, further increasing the density of active sites is still strictly limited by the inherent structure that single-atoms are only highly-dispersed on the substrate. By the way, facets optimization strategy has been widely studied due to its high-density active sites, where some challenges need to be overcome for the improvement of catalytic activity. Thus, the route to gain high-density/efficient surface active sites is always desired for Li-S battery.
The research team suggests that using a single-crystal architecture can provide solutions to some of these challenge with the Li-S batteries. In their study, they used the atomic high-rich Co3+-Se terminated (ACT) concept to create a high-performance matrix. They synthesized a single-crystal CoSe2 (scCS) wrapped by reduced graphene oxide using a simple hydrothermal process. This single-crystal architecture is effective in countering several of the challenges that Li-S batteries present. The single-crystal architecture in scCS can both suppress the shuttle effect and reduce polarization. This effectively boosts the lithium-ion migration and lowers the barrier of polysulfides.
Because of the unique single-crystal structure of CoSe2, the facets of scCS can be stacked by the obvious pure Co/Se atoms, in contrast with mixed terminated facet found in polycrystal CoSe2 samples. With the single-crystal architecture of CoSe2, the team sees the potential to easily achieve the large atomic density and highly effective surface active sites. Using their method, they achieved a high efficient surface-active sites concentration of more than 69 percent. The higher concentration of surface active sites provides superior electro-catalysis ability while easing the problem of polysulfide dissolution.
Looking ahead to future application, the research team sees potential for their work. They believe their new method might prove useful in areas beyond the Li-S batteries. "This surface lattice strategy with element terminated mode is a promising approach for designing electrocatalyst effect-based energy systems, not merely for Li-S batteries," said Xing Ou, School of Metallurgy and Environment, Central South University.
The research team members include Shujie Liu from Jilin University and Changchun University;
Xiaofei Liu, Xin Ge, Wei Zhang, Tingting Qin, Weitao Zheng from Jilin University; Manfang Chen, Dan Zhang from Xiangtan University; Dong Wang from Hunan University; Xiyang Wang from University of Waterloo; Chunhui Wang, Haozhe Qin, Xing Ou from Central South University; and Liang Qiao from Changchun University.
This work was funded by the National Natural Science Foundation of China and the Science and Technology Development Project of Jilin Province.
The paper is also available on SciOpen (https://www.sciopen.com/article/10.1007/s12274-022-4381-8) by Tsinghua University Press.
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About Nano Research
Nano Research is a peer-reviewed, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society. It offers readers an attractive mix of authoritative and comprehensive reviews and original cutting-edge research papers. After more than 10 years of development, it has become one of the most influential academic journals in the nano field. Rapid review to ensure quick publication is a key feature of Nano Research. In 2020 InCites Journal Citation Reports, Nano Research has an Impact Factor of 8.897 (8.696, 5 years), the total cites reached 23150, and the number of highly cited papers reached 129, ranked among the top 2.5% of over 9000 academic journals, ranking first in China's international academic journals.
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