TY - CONF A1 - Wu, Shu-Han T1 - Exploring Sodium Ion Storage: Combining a MOF Derived Carbon Core with a Sieving Carbon Shell to Illuminate Adsorptive Site Influences N2 - Unlike lithium-ion batteries (LIBs) where crystalline graphite is commonly used as the negative electrode material, disordered carbons are regarded as more promising forsodium-ion batteries (SIBs). However, further advances towards better reversibility and higher specific capacity are still needed to match or even exceed the properties of graphite in LIBs. The main challenge is the complex and unpredictable Na+ storage mechanism in disordered carbons. [1] Method: Recently, Matsukawa et al. have reported that the reversibility of (de)sodiation processes of disordered carbons is better for ultra microporous carbons.[2] Ultra micropores are accessible only to Na+ ions and not to solvent molecules. Therefore, the ultra micopores can be used for Na-storage, however, do not significantly contribute to side reactions caused by solid-electrolyte interphase (SEI) formation, which reduces the related irreversible capacity loss. Building on this concept, the origins of specific capacity and irreversible losses were further explored by modifying the chemical composition of zeolitic imidazolate framework (ZIF-8) derived carbons, while maintaining comparable porosity. This involved adjusting the nitrogen content through temperature variation. Additionally, these ZIF-8 derived carbons were enhanced with a protective ion sieving carbon shell formed by chemical vapor deposition. This shell enables effective distinction between reversible and irreversible Na+ storage. Results: The tailor-made core-shell carbons with higher nitrogen content demonstrate greater capacity in the sloping region, but lower capacity in the plateau region of the voltage profile. In addition, they show reduced specific capacities compared to materials with lower nitrogen content. Lastly, it is important to highlight that the incorporation of sieving carbons results in a significant overall increase in capacity compared to materials without sieving carbons. The highest capacities were obtained for the core shell carbon pyrolyzed at 1000°C reaching reversible capacities of 381 +/- 4 mAh g–1 . Discussion: The nitrogen active sites in the as-synthesized materials facilitate the adsorption of Na+ ions, indicating that Na+ ions preferentially adhere to these active sites during the sodiation process. Moreover, the relatively low capacity observed in materials with higher nitrogen content may be attributed to their lower electrical conductivity. T2 - Batterieforum 2025 CY - Berlin, Germany DA - 21.01.2025 KW - Sodium-ion batteries KW - Hard carbon KW - Core-shell materials PY - 2025 AN - OPUS4-65131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han A1 - Appel, Paul Alexander T1 - DialySorb N2 - Lithium-ion batteries (LIBs) have been one of the greatest achievements in the field of energy storage of the last century. However, with the increasing demand for energy storage, battery technologies must be diversified according to their specific requirements in different applications. In terms of stationary energy storage and electric vehicles, sodium-ion batteries (SIBs) are considered to be the most attractive alternative to LIBs due to the uniformly high abundance and cost-effectiveness of raw materials, enabling large-scale and low-cost energy storage. Unlike LIBs where crystalline graphite is commonly used as the anode material, disordered carbons are regarded as more promising for SIBs. However, further advances towards better reversibility and higher specific capacity are still needed to match or exceed that of graphite in LIBs. The main challenge is the complex and unpredictable Na+ storage mechanism in disordered carbons, as they may have different properties depending on the precursors and carbonization conditions. [1] Recently, Matsukawa et al. have reported that the reversibility of (de)sodiation processes of disordered carbons is better for ultramicroporous carbons.[2] These pores are accessible only to Na+ ions and not to solvent molecules. Therefore, the (de)sodiation processes are protected from the side reactions caused by the solvent, which reduces the related irreversible capacity loss. With this idea, the origin of the specific capacity and irreversible losses will be further investigated by tailoring chemical composition (e.g., heteroatom doping) as well as pore structure of hard carbons used as anode materials in SIBs. For the synthesis scalable and industrially relevant processes will be used. The structure and morphology of the materials will be characterized by electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. In addition, different gas sorption techniques will be carried out to analyze the porosity, pore sizes and specific surface areas. The electrochemical performance of the prepared materials will be evaluated based on coin cells, three-electrode Swagelok cells, and pouch cells. Moreover, solid-state nuclear magnetic resonance spectroscopy will be performed to help understand the mechanism of Na+ storage. T2 - Electrochemistry 2022 (GDCh confernece) CY - Berlin, Germany DA - 27.09.2022 KW - Na-ion Battery PY - 2022 AN - OPUS4-62013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han T1 - Sodium Storage Mechanisms and Performance Improvement of Synthetic Hard Carbon Materials N2 - Hard carbons (HCs) are promising anodes for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, their broader use is limited by an incomplete understanding of sodium storage mechanisms. Internal porosity is key to high capacity, but tuning its chemical functionality remains challenging. In this study, we designed core–shell carbon materials featuring closed pores and tailored surface chemistry to distinguish reversible sodium storage from irreversible capacity losses associated with solid electrolyte interphase (SEI) formation. Our results reveal that external porosity can be clearly converted into internal porosity, leading to enhanced sodium storage performance, with capacities exceeding those of lithium in graphite. T2 - Advanced Automotive Battery Conference (AABC) 2025 CY - Mainz, Germany DA - 23.06.2025 KW - Sodium-ion batteries KW - Hard carbon KW - Core-shell materials PY - 2025 AN - OPUS4-65133 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han T1 - Revealing the Impact of Nitrogen Sites on the Sodium Storage Mechanism in Carbon Electrodes N2 - Unlike lithium-ion batteries (LIBs), where crystalline graphite is commonly used as the negative electrode material, disordered carbons are regarded as more promising for sodium-ion batteries (SIBs). However, further advances towards better reversibility and higher specific capacity are still needed to match or even exceed the properties of graphite in LIBs. The main challenge is the complex and unpredictable Na-storage mechanism in disordered carbons. Recently, Matsukawa et al. have reported that the reversibility of (de)sodiation processes of ultra microporous carbons is higher compared to carbon materials with larger pore sizes.[2] Ultra micropores are accessible only to Na+-ions and not to solvent molecules. Therefore, ultra micropores can be used for Na-storage, however, do not significantly contribute to side reactions caused by solid-electrolyte interphase (SEI) formation, which reduces the related irreversible capacity loss. Building on this concept, the origins of specific capacity and irreversible losses were further explored in the current work by modifying the chemical composition of zeolitic imidazolate framework (ZIF-8) derived carbons, while maintaining comparable porosity. This involved adjusting the nitrogen content as well as the types of nitrogen sites through temperature variation. Subsequently, these ZIF-8 derived carbons were modified with a protective ion-sieving carbon shell formed by chemical vapor deposition (CVD). This synthesis methodology enables effective distinction between reversible Na-storage and irreversible processes, e.g., SEI-formation. The former and later are mainly dictated by the properties of the ZIF-derived carbon core and the CVD based shell, respectively. The structure and morphology of the materials were characterized by electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. In addition, different gas sorption techniques were carried out to analyze the porosity, pore sizes and specific surface areas. The electrochemical performance of the prepared materials was evaluated in coin cells vs. Na-metal. The results of the tailor-made core-shell carbons reveal that a higher nitrogen content leads to a greater capacity in the sloping region, but to a lower capacity in the plateau region of the voltage profile. In addition, the overall capacity is higher for materials with lower nitrogen content. Lastly, it is important to highlight that the incorporation of ion-sieving carbon shell results in a significant overall increase in capacity compared to materials without a carbon shell. The highest reversible capacities (i.e., 381 +/- 4 mAh g–1) were obtained for the core-shell carbon comprising a ZIF-derived core pyrolyzed at 1000°C. Apparently, the N-sites in the as-synthesized materials facilitate the adsorption of Na+ ions, indicating that Na+ ions preferentially adhere to these active sites during the sodiation process. It is worth noting that these results were observed while minimizing side reactions, making them more reliable and providing conclusive evidence for the long-debated Na-storage mechanism. Moreover, the lower capacity observed in materials with higher nitrogen content may be attributed to a lower electrical conductivity. T2 - Advanced Battery Power Conference 2025 CY - Aachen, Germany DA - 02.04.2025 KW - Sodium-ion batteries KW - Hard carbon KW - Core-shell materials PY - 2025 AN - OPUS4-65132 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han T1 - Synthetic Carbon Anodes for SIBs N2 - Hard carbon (HC) is currently one of the most promising anode materials for sodium-ion batteries (SIBs). However, the Na storage mechanism remains controversial, leaving the theoretical limits carbon anodes unclear. To deconvolute the specific capacity from irreversible capacity losses resulting from the formation of solid electrolyte interphase (SEI), core-shell carbon materials with tailored pore structure and defined surface functionalities are synthesized. Meanwhile, these synthetic designer carbons could achieve more competitive capacities for use as better anodes for SIBs. T2 - Adlershofer Forschungsforum (AFF) CY - Berlin, Germany DA - 11.11.2024 KW - Na-ion Battery PY - 2024 AN - OPUS4-61998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han T1 - Mole sieving, artificial cathode electrolyte interphase enables stable cycling of room temperature sodium sulfur cells N2 - Porous carbon particles derived from zeolitic imidazolate framework (ZIF-8) were used as a matrix to improve the electrode conductivity and buffer the volume change of sulfur (S). In addition, the porous carbon particles were coated with an additional ion-sieving tailor-made covalent organic framework (COF) shell, which can be regarded as an artificial cathode electrolyte interphase (CEI). The introduced shell can avoid polysulfides from dissolving in the ether-based electrolyte, thus, preventing the shuttling of polysulfides. The as-synthesized sulfur-infiltrated core-shell cathode delivers a reversible capacity of 975 mAh gS–1 (@C/33) and a reasonable rate capability. T2 - 5th International Sodium Battery Symposium, SBS-5 CY - Berlin, Germany DA - 23.09.2024 KW - NaS Battery PY - 2024 AN - OPUS4-61992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Appel, Paul Alexander A1 - Prinz, Carsten A1 - Low, Jian Liang A1 - Asres, Nahom Enkubahri A1 - Wu, Shu-Han A1 - Freytag, Annica A1 - Krug von Nidda, Jonas A1 - de Sousa Amadeu, Nader A1 - Fellinger, Tim-Patrick T1 - Kern–Schale: Versiegelung nanoporöser Partikel mit semipermeablen Kohlenstoffschichten befreit Hartkohlenstoffanoden von ihrem Dilemma N2 - In der vorliegenden Arbeit wird eine Kern-Schale-Strategie vorgestellt, die das grundlegende Problem gängiger nichtgraphitischer Hartkohlenstoff-Anoden adressiert: Hohe reversible Kapazitäten gehen bislang typischerweise mit erheblichen irreversiblen Verlusten in den ersten Zyklen einher. Analog zu Graphit, das sowohl Lithiumspeicherung als auch die Abtrennung von Elektrolytlösungsmitteln in einer homogenen Struktur vereint, zeigen wir, dass sich diese beiden Funktionen auch in nichtgraphitischen Kohlenstoffen gezielt in einer heterogenen Architektur kombinieren lassen. Hochporöse Aktivkohlen werden durch kinetisch kontrollierte Gasphasenabscheidung mit einer dünnen Schicht nichtgraphitischen Kohlenstoffs überzogen, sodass eine funktionale Kern-Schale-Struktur entsteht. Gasadsorptionsmessungen an Kern-, Schalen-, Kern-Schale- und mechanisch beschädigte Kern-Schale-Partikeln, bestätigen, dass die Porosität des Kerns erhalten bleibt und die Schale semipermeabel ist. Die Sorption von Diethylcarbonat wird als geeignetere Methode im Vergleich zu N2- oder CO2-Sorptionsmessungen eingeführt, um die irreversiblen Verluste des ersten Zyklus mit der tatsächlichen Flüssig-Fest-Grenzfläche von Kohlenstoffanoden zu verknüpfen. Die funktionalen Kern-Schale-Partikel zeigen eine stark reduzierte Aufnahme von Diethylcarbonat, was hohe reversible Kapazitäten bei deutlich geringeren Erstzyklusverlusten ermöglicht. Bei einer reversiblen Kapazität von 400 ± 24 mAh g−1 und einer initialen Coulombeffizienz von 82 ± 2% zeigt sich, dass die dreistufige Natriumspeicherung in der gezielt entwickelten Kern-Schale-Architektur den größeren Ionenradius von Natrium gegenüber Lithium (372 mAh g−1 in Graphit) kompensieren kann. Die entwickelten Kern-Schale-Anoden erreichen damit ein Leistungsniveau, das für eine kommerzielle Anwendung vielversprechend ist. KW - Kern-Schale-Struktur KW - Natriumionenbatterie KW - Hartkohlenstoffanode KW - Diethylcarbonatdampfsorption KW - Aktivkohle PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655354 DO - https://doi.org/10.1002/ange.202519457 SN - 1521-3757 N1 - Es gibt eine parallele Sprachausgabe (englisch), ein Link befindet sich im Feld zugehöriger Identifikator - There is a parallel language edition (English), a link is in the field related identifier SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim AN - OPUS4-65535 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wu, Shu-Han T1 - MOF-derived Synthetic Carbon Anode Materials for Sodium-Ion Batteries N2 - Metal-organic frameworks (MOFs), particularly the zeolitic imidazolate framework (ZIF) family, are attractive precursors for advanced energy-storage materials. Upon pyrolysis, ZIFs can be transformed into electrically conductive carbon materials while preserving their original particle morphology, which is crucial for achieving high-performance sodium-ion battery anodes. Despite these advantages, large-scale implementation remains challenging due to the need for synthesis routes that balance performance, cost, and sustainability. The present study addresses these challenges by developing environmentally benign and economically feasible strategies for the scalable production of ZIF-8-derived carbon anodes suitable for industrial applications. T2 - Batterieforum Deutschland 2026 CY - Berlin, Germany DA - 20.01.2026 KW - Sodium-ion battery KW - Negative electrode KW - Metalorganic frameworks PY - 2026 AN - OPUS4-65644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -