ENGINEERING TECHNOLOGY

New high-sulfur lithium-sulfur cathode material! This is achieved through interfacial doping and graphene layer network protection


January 5, 2023,Nano Research Energy (https://www.sciopen.com/journal/2790-8119) Young Editorial Board Member, Associate Professor Liu Mingkai, Jiangsu Normal UniversityPublished under the title “High Sulfur Loading and Shuttle Inhibition of Advanced Sulfur Cathode Enabled by Graphene Network Skin and N, P, F Doped Mesoporous Carbon Interfaces for Ultra-stable Lithium Sulfur.” Battery”.

With the rapid development of society and technology, people’s requirements for energy and power density of energy equipment are getting higher and higher. Lithium-sulfur batteries haveUltra-high theoretical energy densityandSpecific capacity, considered one of the promising candidates for the next generation of batteries.Lithium-sulfur batteriesIt is a kind of lithium battery, which is a lithium battery with sulfur element as the positive electrode of the battery and metal lithium as the negative electrode. Elemental sulfur has abundant reserves in the earth, and has the characteristics of low price and environmental friendliness. Lithium-sulfur batteries using sulfur as the cathode material have a higher material specific capacity and a higher theoretical specific energy of the battery, respectively 1675 mAh/g and 2600 Wh/kg, much higher than the capacity of commercially widely used lithium cobalt oxide batteries (<150 mAh/g)。 Unlike the insertion reaction in commercial lithium-ion batteries, elemental sulfur can achieve this high theoretical capacity through a unique conversion reaction. However, the practical application of lithium-sulfur batteries has been hindered by some key technologies. Specifically, (i)Lithium polysulfide (LiPS)It is easily soluble in the electrolyte and diffuses to the anode side, which will lead to rapid capacity attenuation and cause the problem of coulomb inefficiency; (ii)Insulating properties of activated sulfurIts intermediate products Li2S/Li2S2, which bind to lithium ions, are not conductive, which hinders the rapid transport of electrons and further leads to the low utilization rate of active substances. (iii)Huge volume expansion of sulfur (about 80%)This causes the expansion and contraction of the positive electrode structure, causing the collapse of the sulfur cathode. Therefore, the development of one can increase the active sulfur content and at the same time canConstrain lithium polysulfide shuttleandA cathode material that limits the expansion of active sulfurIt is a key technology to realize the large-scale application of high specific energy lithium-sulfur batteries.

Figure 1. Schematic diagram of the construction of high-load sulfur G-NPFMC-S active film material.

In response to the above problems,Associate Professor Liu Mingkai’s research groupDeveloped oneIndependently self-supporting graphene-nitrogen (N), phosphorus (P) and fluorine (F) co-doped mesoporous carbon-sulfur (G-NPFMC-S) filmsIt is used as a binder-free cathode material for lithium-sulfur batteries. The mesoporous carbon (MC) prepared in this paper has a very high specific surface area (921 m2 g-1), the pore size distribution is uniform, for15 nmAround. The graphene network inserted in the G-NPFMC-S cathode can effectively improve its conductivity while limiting the shuttle of polysulfide lithium. This was achieved because graphene-NPFMC (G-NPFMC) composites have a good porous structure86 %High load capacity of active sulfur. When used as the cathode of lithium-sulfur batteries, this independent self-supporting G-NPFMC-S film achieves a high specific capacity (1356 mAh g-1), good rate performance, and up to500 timesof long-cycle stability, with a minimum capacity decay rate per cycle only0.025%。 These excellent results can be attributed to the structural features present inside the G-NPFMC-S film, as the highly porous NPFMC can be sulfur-loadedProvide sufficient storage spaceAt the same time, N, P, F doped carbon interfaces and inserted graphene networks help passChemosorption and physical barrier effects hinder the shuttle of lithium polysulfide。 This unique structure realizes the high load of active sulfur and restricts the shuttle of polysulfur lithium, providing an effective path for the development of lithium-sulfur batteries.

Paper Information:

https://doi.org/10.26599/NRE.2023.9120049

Liu H, Liu F, Qu Z, et al. High sulfur loading and shuttle inhibition of advanced sulfur cathode enabled by graphene network skin and N, P, F-doped mesoporous carbon interfaces for ultra-stable lithium sulfur battery. Nano Research Energy, 2023, https://doi.org/10.26599/NRE.2023.9120049

Nano Research Energy is a companion journal of Nano Research, (ISSN: 2791-0091; e-ISSN: 2790-8119; Official Website: https://www.sciopen.com/journal/2790-8119Founded in March 2022, Professor Qu Liangti of Tsinghua University and Professor Chunyi Zhi of City University of Hong Kong serve as editors-in-chief.Nano Research EnergyIt is an international multidisciplinary and English-based open access journal, focusing on the cutting-edge research and application of nanomaterials and nanoscience and technology in new energy-related fields, benchmarking against top international energy journals, and committed to publishing high-level original research and review papers, which has been selected2022 China Science and Technology Journals Excellence Action Plan – High Starting Point New Journal Project。 APC fees will be waived until 2023, and teachers are welcome to submit their papers. To submit, please contact: NanoResearchEnergy@tup.tsinghua.edu.cn

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