Sodium ion battery negative new strategy: coal macromolecular structure regulation, hard carbon material performance is not bad!

First Author: ZHAO Guangxin

Correspondent: Li Xiaoming *, Dong Liang *, Chen Chengmeng *

SETTING: China University of Mining and Technology, Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences

research background

Coal is not only the main energy source of our country, but also a kind of natural carbon-based heterogeneous organic polymer material, which is the high-quality precursor of sodium ion battery hard carbon negative electrode. However, the complex molecular structure of coal leads to the uncontrollability of its oxidation and structural evolution, which hinders the design of high-performance hard carbon anode materials. Through the regulation strategy of coal macromolecular structure, this paper reveals the influence of the molecular structure characteristics of coal maceral on its oxidation reactivity, and the structure-activity relationship between its cross-linking structure and coal-derived hard carbon structure. At the same time, the oxygen adsorption behavior of different coal molecules during the heating process was revealed by the simulation of molecular mechanics and Monte Carlo method. The research team found that coal macromolecules with more aliphatic structures showed higher oxidation reactivity, resulting in a more disordered carbon layer structure and the formation of more ultramicropores. The study shows that the specific capacity of vitrinite-rich coal-derived hard carbon reaches 330.2 mAh/g, which is much higher than the specific capacity of 260 mAh/g coal-derived hard carbon rich in inertinite. This study provides ideas for the preparation of high-capacity coal-derived hard carbon, and provides theoretical guidance for the study of other thermochemical systems.

Introduction to Article

Recently, Professor Dong Liang, academician team of Zhao Yuemin from China University of Mining and Technology, in cooperation with researcher team of Chen Chengmeng from Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, published a research article entitled "Conversion of aliphatic structure-rich coal maceral into high-capacity hard carbons for sodium-ion batteries" in the Materials of Energy Storage, an internationally renowned journal. This research paper innovatively studied the influence of different molecular structures of coal on its oxidation reactivity, and the structure-activity relationship between its cross-linking structure and coal-derived hard carbon structure, which proved that the coal macerals with rich aliphatic structure are more conducive to the storage of sodium ions after pre-oxidation. The relevant paper was published in EnSM, with Zhao Guangxuan of China University of Mining and Technology as the first author and Chen Chengmeng, Li Xiaoming and Dong Liang as co-corresponding authors.

Main points of this paper

Point 1: According to the molecular structure characteristics, the coal molecular model is established.

Coal macerals were separated by density gradient centrifugation, and pre-oxidation and carbonization were carried out to prepare coal-derived hard carbon. According to the results of XRD, 13C CP/MAS NMR and TG/DTG test, it is confirmed that the molecular structures of different microcomponents are quite different, and the vitrinite has more aliphatic structures than the idler group. In order to further clarify the influence of molecular structure on oxidation reactivity, molecular models of different coal macerals were established. The simulation and measurement results were corrected by 13C CP/MAS NMR, and the plane model of coal macerals was completed. In order to obtain a global * small energy model, annealing simulation is carried out to optimize the whole potential energy.

Key point two: coal macerals with different molecular structures have different oxidation reactivity

By ex-situ FTIR, 13C CP/MAS NMR and XPS analysis, it is confirmed that the coal enhances the degree of crosslinking of the carbon precursor during the oxidation process, making the planar structure three-dimensional, while the vitrinite rich in aliphatic structure has a higher proportion of crosslinking groups. The adsorption capacity of oxygen molecules was calculated by Monte Carlo method, and it was found that vitrinite was more favorable for the adsorption of oxygen molecules. The above results show that vitrinite containing more aliphatic is more conducive to the introduction of oxygen molecules and the formation of cross-linked structure.

Point three: further reveals the oxidation mechanism of coal

The microscopic reaction path of low temperature oxidation of coal was visually observed by in situ free radical test. From room temperature to 200 ℃, the aliphatic structure is oxidized to produce a large number of benzoquinone free radicals, forming independent molecules centered on each aromatic nucleus. From 200 ℃ to 300 ℃, the free radicals begin to combine and generate oxygen-containing functional groups. This trend can be reflected in the ex-situ FTIR, and this stage is dominated by the generation of oxygen-containing functional groups.

Point four: coal derived hard carbon electrochemical performance evaluation

Thanks to the enhanced cross-linking structure and abundant ultramicropores, the reversible capacity of the rich aliphatic coal-derived hard carbon is 330.2 mAh/g and the ICE is 89.7 at 20 mA/g. At a current density of 100mA/g, the capacity retention of the PCBC125 after 300 cycles was as high as 96.0%, showing good long cycle stability.

Article Link

Conversion of aliphatic structure-rich coal maceral into high-capacity hard carbons for sodium-ion batteries

https://doi.org/10.1016/j.ensm.2024.103282

Introduction to the Corresponding Author

Introduction to Researcher Chen Chengmeng: Born in 1985, from Zoucheng, Shandong, Ph.D., researcher, deputy director of the Key Laboratory of Carbon Materials, Chinese Academy of Sciences, and project leader of the 709 group of Shanxi Institute of Coal and Chemistry, Chinese Academy of Sciences. He is also a distinguished director of the China Particle Society, deputy secretary-general of the China Super Capacitor Industry Alliance, member of the Academic Committee of the Key Laboratory of Coal Processing and * Clean Utilization of the Ministry of Education, director of the China Graphene Industry Technology Innovation Strategic Alliance, expert of the International Electrotechnical Commission (IEC/TC113) and the National Standards Commission Nano Standards Committee (SAC/TC279), editorial board of China Chemical Express, youth editorial board of China Journal of Chemical Engineering and Journal of Particles. He graduated from China University of Mining and Technology in 2006 and received a doctor's degree from Shanxi Coal Chemical Industry, Chinese Academy of Sciences in 2012. He studied in Fritz Haber Institute of German Ma Pu Institute from 2010 to 2011. Mainly engaged in the research of advanced carbon materials and energy storage devices, undertaking more than 60 projects such as national key research and development plan projects, national natural science foundation projects, JKW foundation strengthening key projects, Shanxi Province science and technology major special projects, and horizontal cooperation between international and domestic enterprises. He has published 110 papers as a writer or correspondent, cited more than 10000 times, h factor 57, authorized 50 patents, published 1 English monograph, and presided over the formulation of 7 international and national standards.

Won the IEC1906 Award (2022), the Young Scientist Award of the Chinese Academy of Sciences (2023), the First Prize of Shanxi Natural Science (2019), and the First Prize of China's Industry-University-Research Cooperation Innovation Achievement (2019). He was selected into the "MIT Science and Technology Review" in China "35 people under the age of 35" (2017), Shanxi Province academic and technological leader (2020), and was funded by the National Natural Science Outstanding Youth Fund (2019).

Brief introduction of Professor Dong Liang: Head of Mineral Processing Engineering Discipline of China University of Mining and Technology, engaged in the research of gas-solid fluidized dry separation and coal-based carbon material construction. Presided over the National Natural Science Foundation of China, Jiangsu Province Natural Science Foundation and other provincial and ministerial level projects above 6. As the main completion person, he won 1 second prize for national scientific and technological progress, 1 special prize for scientific and technological progress of the Ministry of Education, 1 first prize, and 2 first prizes for science and technology of China's coal industry. The first author/corresponding author is Chem. Eng. Sci. More than 30 SCI papers have been published in journals such as Chem. Eng. J., and more than 10 invention patents have been authorized in China, the United States, Japan, and Canada. Hou Debang Chemical Science and Technology Youth Award, Coal Youth Science and Technology Award, National Youth Post Expert, etc.

Senior engineer Li Xiaoming: Senior engineer of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, engaged in the research and engineering technology development of coal-based energy storage carbon materials, multi-phase dispersion of carbon materials and powder engineering technology development. He has presided over three provincial and ministerial projects and four projects entrusted by enterprises. He has published 34 SCI papers, applied for 37 patents, 1 software work and participated in the drafting of 2 national standards. Won the first prize of China's industry-university-research cooperation and innovation achievements, the second prize of China Chemical Industry Association for technological invention, etc.

Introduction of the research group

The Advanced Carbon Materials and Devices Research Group (709 Group) was established in July 2012. After more than 10 years of development, it has grown from 2 people to a multi-disciplinary youth team of more than 70 people, including 20 scientific research backbones and 15 engineers., 44 graduate students, 10 senior titles. A high-standard laboratory covering an area of 330 m2 and a pilot line of 2000 m2 have been built to realize 6S management. The team focuses on the field of carbon-based new materials and new energy industry, and is oriented to the large-scale production and application demonstration of advanced carbon materials such as graphene, capacitor carbon, energy storage anode, etc., and is committed to the research of common key scientific issues, high-tech development and industrialization. It has made outstanding contributions to the development of my country's advanced carbon material industry. Approved "Graphene Energy Storage Technology Research Shanxi Province Science and Technology Innovation Team", "Shanxi Province Graphene Technology Engineering Research Center", "Shanxi Province Energy Storage Carbon Materials Innovation Center Pilot (Cultivation)", "Shanxi Province Advanced Electrochemical Energy Storage Materials Engineering Application Research Center". In 2020, the team won the title of "Shanxi Youth May 4th Award.