Transition metal disulfide/graphene nanocomposites for Na-ion batteries: design and electronic interactions
Final Report Abstract
The aim of the project was to study the physical processes occurring during sodium ion intercalation in heterostructures of transition metal disulfides (TMD) and graphene. The implementation plan included developing synthesis methods for TMD/graphene composites, characterizing their morphology, structure and electronic properties, and studying their electrochemical performance and stability. Throughout the project, methods were developed for producing TMD film and polycrystalline compounds, both pure and niobium-doped. Materials based on MoS₂ with heteroatom doping and graphene sandwich structures were extensively studied, along with synthesized WS₂ and VS₂, revealing that rhenium alloying did not significantly affect WS₂'s electrochemical properties, while pure, oxygen-free VS₂ samples could not be obtained for further investigation. TMD samples obtained by CVD, ampoule, hydrothermal and thermobaric methods were systematically studied using various techniques such as electron microscopy, X-ray diffraction, Raman scattering, NMR spectroscopy and X-ray photoelectron spectroscopy using synchrotron radiation (BESSY II, HZB Berlin). In situ experiments were performed to study the interaction of alkali metals with MoS2, revealing key changes in the electronic structure of TMDs during niobium doping and lithium/sodium deposition. An important finding was the penetration of lithium ions through graphene layers to the MoS2 substrate in graphene/MoS2 sandwich structures. The highest specific capacity in lithium-ion and sodium-ion batteries was observed for MoS2 and WS2 anodes with 10% niobium content. The project faced several unforeseen challenges, which made it necessary to restructure the project into a purely German project in summer 2022. As transition metal disulphide samples were therefore no longer available, a natural mineral, rectorite from South Africa, was used as a substitute to investigate its potential as an environmentally friendly and cost-effective electrode material. The study showed that Mg2+ exchanged rectorite exhibited unique ionic conductivity and hydration properties, making it a promising material for future applications. Additionally, a new NMR cell, allowing in situ monitoring of electrochemical processes, was developed and successfully tested. Findings from the project contributed to understanding the conversion of CO2 into multicarbon products like ethanol.
Publications
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Chemical energy conversion processes investigated by NMR. Invited talk at the Renewable Energy Conference 2023, Paris, France, 23-25.10.2023
A. Vyalikh
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Investigation of the structural and electrical conductivity properties in pure and cation exchanged rectorite. Applied Clay Science, 245, 107116.
Vyalikh, Anastasia; Atanasova, Maria T.; Focke, Walter W.; Makarova, Anna A.; Krajnc, Andraz & Mali, Gregor
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Detection of electrocatalytical and -chemical processes by means of in situ flow NMR spectroscopy. Electrochemistry Communications, 163, 107736.
Vyalikh, Anastasia; Münchgesang, Wolfram & Velasco-Vélez, Juan-Jesús
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Exploring the role of nuclear magnetic resonance (NMR) spectroscopy in the study of biorelevant nanocomposites and electrochemical reactions. Invited Talk at DIPC, Donostia / San Sebastián, Spain, 03.05.2024
A. Vyalikh
