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3. Liquid exfoliation of solvent-stabilised black phosphorus: applications beyond electronics

Author

Hanlon, Damien, Backes, Claudia, Doherty, Evie, Cucinotta, Clotilde S., Berner, Nina C., Boland, Conor, Lee, Kangho, Lynch, Peter, Gholamvand, Zahra, Harvey, Andrew, Zhang, Saifeng, Wang, Kangpeng, Moynihan, Glenn, Pokle, Anuj, Ramasse, Quentin M., McEvoy, Niall, Blau, Werner J., Wang, Jun, Sanvito, Stefano, ORegan, David D., Duesberg, Georg S., Nicolosi, Valeria, and Coleman, Jonathan N.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Few layer black phosphorus is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of stability severely limits our ability to synthesise and process this material. Here we demonstrate that high-quality, few-layer black phosphorus nanosheets can be produced in large quantities by liquid phase exfoliation in the solvent N-cyclohexyl-2-pyrrolidone (CHP). We can control nanosheet dimensions and have developed metrics to estimate both nanosheet size and thickness spectroscopically. When exfoliated in CHP, the nanosheets are remarkably stable unless water is intentionally introduced. Computational studies show the degradation to occur by reaction with water molecules only at the nanosheet edge, leading to the removal of phosphorus atoms and the formation of phosphine and phosphorous acid. We demonstrate that liquid exfoliated black phosphorus nanosheets are potentially useful in a range of applications from optical switches to gas sensors to fillers for composite reinforcement., Comment: 6 figures

Published
2015
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4. Zn Redistribution and Volatility in ZnZrOx Catalysts for CO2 Hydrogenation

Author

Redekop, Evgeniy A., primary, Cordero-Lanzac, Tomas, additional, Salusso, Davide, additional, Pokle, Anuj, additional, Oien-Odegaard, Sigurd, additional, Sunding, Martin Fleissner, additional, Diplas, Spyros, additional, Negri, Chiara, additional, Borfecchia, Elisa, additional, Bordiga, Silvia, additional, and Olsbye, Unni, additional

Published
2023
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5. Manganese oxide nanosheets and a 2D hybrid of graphene-manganese oxide nanosheets synthesized by liquid-phase exfoliation

Author

Coelho, Joao, Mendoza-Sanchez, Beatriz, Pettersson, Henrik, Pokle, Anuj, McGuire, Eva K., Long, Edmund, McKeon, Lorcan, Bell, Alan P., and Nicolosi, Valeria

Subjects
Condensed Matter - Materials Science
Abstract

Manganese oxide nanosheets were synthesized using liquid phase exfoliation that achieved suspensions in isopropanol with concentrations of up to 0.45 mg/ml. A study of solubility parameters showed that the exfoliation was optimum in DMF followed by isopropanol and diethylene glycol. Isopropanol was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. The 2D hybrid was synthesized in isopropanol suspensions with concentrations of up to 0.5 mg/ml and demonstrated stability against reaggregation for up to six months. The coexfoliation was found to be an energetically favorable process in which both solutes, graphene and manganese oxide nanosheets, exfoliate with an improved yield as compared to the single solute exfoliation procedure. This work demonstrates the remarkable versatility of liquid phase exfoliation with respect to the synthesis of hybrids with tailored properties, and it provides proof of concept ground work for further future investigation and exploitation of hybrids made of two or more 2D nanomaterials that have key complementary properties for various technological applications.

Published
2014

11. Zn Redistribution and Volatility in ZnZrOxCatalysts for CO2Hydrogenation

Author

Redekop, Evgeniy A., Cordero-Lanzac, Tomas, Salusso, Davide, Pokle, Anuj, Oien-Odegaard, Sigurd, Sunding, Martin Fleissner, Diplas, Spyros, Negri, Chiara, Borfecchia, Elisa, Bordiga, Silvia, and Olsbye, Unni

Abstract

ZnO–ZrO2mixed oxide (ZnZrOx) catalysts are widely studied as selective catalysts for CO2hydrogenation into methanol at high-temperature conditions (300–350 °C) that are preferred for the subsequent in situzeolite-catalyzed conversion of methanol into hydrocarbons in a tandem process. Zn, a key ingredient of these mixed oxide catalysts, is known to volatilize from ZnO under high-temperature conditions, but little is known about Zn mobility and volatility in mixed oxides. Here, an array of ex situand in situcharacterization techniques (scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Infrared (IR)) was used to reveal that Zn2+species are mobile between the solid solution phase with ZrO2and segregated and/or embedded ZnO clusters. Upon reductive heat treatments, partially reversible ZnO cluster growth was observed above 250 °C and eventual Zn evaporation above 550 °C. Extensive Zn evaporation leads to catalyst deactivation and methanol selectivity decline in CO2hydrogenation. These findings extend the fundamental knowledge of Zn-containing mixed oxide catalysts and are highly relevant for the CO2-to-hydrocarbon process optimization.

Published
2023
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17. Operando Laboratory-based Multi-edge X-ray Absorption Near-Edge Spectroscopy of Solid Catalysts

Author

Sub Inorganic Chemistry and Catalysis, Sub ARC Chemical Building Blocks Cons., Faculteit Betawetenschappen, Inorganic Chemistry and Catalysis, Genz, Nina S, Kallio, Antti-Jussi, Oord, Ramon, Krumeich, Frank, Pokle, Anuj, Prytz, Øystein, Olsbye, Unni, Meirer, Florian, Huotari, Simo, Weckhuysen, Bert Marc, Sub Inorganic Chemistry and Catalysis, Sub ARC Chemical Building Blocks Cons., Faculteit Betawetenschappen, Inorganic Chemistry and Catalysis, Genz, Nina S, Kallio, Antti-Jussi, Oord, Ramon, Krumeich, Frank, Pokle, Anuj, Prytz, Øystein, Olsbye, Unni, Meirer, Florian, Huotari, Simo, and Weckhuysen, Bert Marc

Published
2022

18. Advanced Analytical Characterization of Interface Degradation in Ni-Rich NCM Cathode Co-Sintered with LATP Solid Electrolyte

Author

Malaki, Michael, primary, Pokle, Anuj, additional, Otto, Svenja-Katharina, additional, Henss, Anja, additional, Beaupain, Jean Philippe, additional, Beyer, Andreas, additional, Müller, Julian, additional, Butz, Benjamin, additional, Wätzig, Katja, additional, Kusnezoff, Mihails, additional, Janek, Jürgen, additional, and Volz, Kerstin, additional

Published
2022
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23. Reaction of Li1.3Al0.3Ti1.7(PO4)3 and LiNi0.6Co0.2Mn0.2O2 in Co-Sintered Composite Cathodes for Solid-State Batteries

Author

Beaupain, Jean Philippe, primary, Waetzig, Katja, additional, Otto, Svenja-Katharina, additional, Henss, Anja, additional, Janek, Jürgen, additional, Malaki, Michael, additional, Pokle, Anuj, additional, Müller, Julian, additional, Butz, Benjamin, additional, Volz, Kerstin, additional, Kusnezoff, Mihails, additional, and Michaelis, Alexander, additional

Published
2021
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27. Reaction of Li1.3Al0.3Ti1.7(PO4)3 and LiNi0.6Co0.2Mn0.2O2 in co-sintered composite cathodes for solid-state batteries

Author

Beaupain, Jean Philippe, Wätzig, Katja, Otto, Svenja-Katharina, Henss, Anja, Janek, Jürgen, Malaki, Michael, Pokle, Anuj, Müller, Julian, Butz, Benjamin, Volz, Kerstin, Kusnezoff, Mihails, Michaelis, Alexander, and Publica

Subjects
oxide electrolyte, composite cathode, element diffusion, all solid state battery, cosintering, NCM, decomposition reaction, LATP
Abstract

All solid-state batteries offer the possibility of increased safety at potentially higher energy densities compared to conventional lithium-ion batteries. In an all-ceramic oxide battery, the composite cathode consists of at least one ion-conducting solid electrolyte and an active material, which are typically densified by sintering. In this study, the reaction of the solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP) and the active material LiNi0.6Co0.2Mn0.2O2 (NCM622) is investigated by cosintering at temperatures between 550 and 650 °C. The characterization of the composites and the reaction layer is performed by optical dilatometry, X-ray diffractometry, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy, time-of-flight secondary ion mass spectrometry, as well as scanning transmission electron microscopy (STEM). Even at low sintering temperatures, elemental diffusion occurs between the two phases, which leads to the formation of secondary phases and decomposition reactions of the active material and the solid electrolyte. As a result, the densification of the composite is prevented and ion-conducting paths between individual particles cannot be formed. Based on the experimental results, a mechanism of the reactions in cosintered LATP and NCM622 oxide composite cathodes is suggested.

Published
2021

30. Visualization of Light Elements using 4D STEM: The Layered‐to‐Rock Salt Phase Transition in LiNiO2 Cathode Material

Author

Ahmed, Shamail, Bianchini, Matteo, Pokle, Anuj, Munde, Manveer Singh, Hartmann, Pascal, Brezesinski, Torsten, Beyer, Andreas, Janek, Jürgen, and Volz, Kerstin

Subjects
Technology, ddc:600
Abstract

The layered oxide LiNiO2 (LNO) has been extensively investigated as a cathode active material for lithium‐ion batteries. Despite LNO's high gravimetric capacity, instability issues hinder its commercialization. It suffers from capacity loss during electrochemical cycling and is difficult to synthesize without defects. This is related to poor structural stability, leading to decomposition into the parent rock‐salt‐type oxide. In order to understand such phase transformations and to develop measures to inhibit them, the development of techniques able to image all atoms is crucial. In this study, the use of a fast, pixelated detector and 4D imaging in scanning transmission electron microscopy are explored to tackle this challenge. Selecting specific angular regions in the diffraction patterns and calculating virtual annular bright‐field images significantly enhances the contrast of the lithium atoms, such that all atoms are visible even in realistic samples. The developed technique is applied to image the layered‐to‐rock salt phase transition region. The data show that in this region, nickel atoms are in tetrahedral positions and the oxygen atoms are asymmetrically distributed. Taken together, the results shed light on the phase transformation mechanism at the atomic scale and can guide future research toward stabilizing LNO.

Published
2020

31. Tracing Low Amounts of Mg in the Doped Cathode Active Material LiNiO2.

Author

Weber, Daniel, Jing Lin, Pokle, Anuj, Volz, Kerstin, Janek, Jürgen, Brezesinski, Torsten, and Bianchini, Matteo

Subjects
PHASE transitions, ENERGY density, THERMAL instability, ELECTROCHEMICAL electrodes, UNIT cell, CATHODES
Abstract

The resurgence of electromobility drives the need for high energy density cathode materials. LiNiO2 (LNO) meets this demand, based on its high specific capacity in a narrow voltage range and without relying on scare elements. Yet, it has been plagued by various issues, such as poor cycling performance and thermal instability. Adding dopants, such as widely available Mg2+, is a common strategy to balance cycling performance and energy density. Most prior studies focused on large Mg content ranges and were based on laboratory X-ray diffraction. Hence, the influence of Mg2+ addition on the crystal structure remains ambiguous, especially when small amounts are used (< 5 mol%; particularly interesting for industrial applications). Here, we present a systematic study of LiNi1-yMgyO2 (0 ≤ y ≤ 0.05) investigated by high-resolution synchrotron-based X-ray diffraction combined with elemental analysis, electron microscopy and electrochemical testing. The synthetic route relies on the addition of 10 nm Mg(OH)2 nanoparticles prior to the final calcination, as well as on co-precipitation. It is found that Mg2+ mostly occupies the Ni site until saturating at ~1.7%, then the Li site becomes preferred. This trend in the site occupancies influences the lattice parameters, oxygen coordinate within the unit cell and Ni-O bond distances. Doping also modifies the electrochemical behavior as a cathode material, stabilizing the capacity retention during cycling but sacrificing specific discharge capacity. Laboratory-based operando X-ray diffraction reveals that the increase in capacity retention is due to the suppression of the H2-H3 phase transition and interlayer distance collapse already in 3% Mg-doped LNO. The combination of structural and electrochemical characterization of doped LNO provides useful insights into the structural chemistry of the Mg2+ dopant and can serve as a starting point to understand Mg as a component in multiple dopant strategies for cathode material design and application. [ABSTRACT FROM AUTHOR]

Published
2022
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38. Self‐Assembly of Atomically Thin Chiral Copper Heterostructures Templated by Black Phosphorus

Author

Nerl, Hannah C., primary, Pokle, Anuj, additional, Jones, Lewys, additional, Müller‐Caspary, Knut, additional, van den Bos, Karel H. W., additional, Downing, Clive, additional, McCarthy, Eoin K., additional, Gauquelin, Nicolas, additional, Ramasse, Quentin M., additional, Lobato, Ivan, additional, Daly, Dermot, additional, Idrobo, Juan Carlos, additional, Van Aert, Sandra, additional, Van Tendeloo, Gustaaf, additional, Sanvito, Stefano, additional, Coleman, Jonathan N., additional, Cucinotta, Clotilde S., additional, and Nicolosi, Valeria, additional

Published
2019
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39. Reaction of Li1.3Al0.3Ti1.7(PO4)3and LiNi0.6Co0.2Mn0.2O2in Co-Sintered Composite Cathodes for Solid-State Batteries

Author

Beaupain, Jean Philippe, Waetzig, Katja, Otto, Svenja-Katharina, Henss, Anja, Janek, Jürgen, Malaki, Michael, Pokle, Anuj, Müller, Julian, Butz, Benjamin, Volz, Kerstin, Kusnezoff, Mihails, and Michaelis, Alexander

Abstract

All solid-state batteries offer the possibility of increased safety at potentially higher energy densities compared to conventional lithium-ion batteries. In an all-ceramic oxide battery, the composite cathode consists of at least one ion-conducting solid electrolyte and an active material, which are typically densified by sintering. In this study, the reaction of the solid electrolyte Li1.3Al0.3Ti1.7(PO4)3(LATP) and the active material LiNi0.6Co0.2Mn0.2O2(NCM622) is investigated by cosintering at temperatures between 550 and 650 °C. The characterization of the composites and the reaction layer is performed by optical dilatometry, X-ray diffractometry, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy, time-of-flight secondary ion mass spectrometry, as well as scanning transmission electron microscopy (STEM). Even at low sintering temperatures, elemental diffusion occurs between the two phases, which leads to the formation of secondary phases and decomposition reactions of the active material and the solid electrolyte. As a result, the densification of the composite is prevented and ion-conducting paths between individual particles cannot be formed. Based on the experimental results, a mechanism of the reactions in cosintered LATP and NCM622 oxide composite cathodes is suggested.

Published
2021
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40. Synthesis and Postprocessing of Single-Crystalline LiNi0.8Co0.15Al0.05O2for Solid-State Lithium-Ion Batteries with High Capacity and Long Cycling Stability

Author

Fantin, Roberto, Trevisanello, Enrico, Ruess, Raffael, Pokle, Anuj, Conforto, Gioele, Richter, Felix H., Volz, Kerstin, and Janek, Jürgen

Abstract

The application of nickel-rich LiNixCoyAlzO2(NCA) cathode materials in solid-state lithium-ion batteries (SSBs) promises significant improvements in energy density, stability, and safety over traditional lithium-ion batteries with liquid electrolytes. However, low active mass utilization and strong capacity fading associated with degradation of the cathode often limit SSB applicability. The use of single-crystalline cathode active materials (CAMs) instead of spherical polycrystalline materials optimized for performance in lithium-ion batteries recently emerged as a promising approach in the field of SSBs to overcome this issue. In this work, single-crystalline LiNi0.8Co0.15Al0.05O2(SC-NCA) is investigated as cathode active material for SSBs. It is shown that appropriate postprocessing of as-synthesized materials, which consists of washing steps with either water or ethanol followed by postannealing at different temperatures, is key to achieve high-performance cathodes. X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy are employed to characterize the effect of postprocessing on structure and morphology. The postprocessing procedure was tailored to mitigate detrimental side reactions that result in structural damage of the SC-NCA, while retaining the beneficial effects of deagglomeration and control of surface impurities. Washing with ethanol and subsequent postannealing at 750 °C allowed us to obtain SC-NCA materials that perform well in SSB cells with Li6PS5Cl as solid electrolyte, enabling a high initial discharge capacity of 174 mAh g–1, good rate performance, and high capacity retention (94% after 200 cycles) at 25 °C.

Published
2021
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41. Visualization of Light Elements using 4D STEM: The Layered‐to‐Rock Salt Phase Transition in LiNiO2 Cathode Material.

Author

Ahmed, Shamail, Bianchini, Matteo, Pokle, Anuj, Munde, Manveer Singh, Hartmann, Pascal, Brezesinski, Torsten, Beyer, Andreas, Janek, Jürgen, and Volz, Kerstin

Subjects
LIGHT elements, SCANNING transmission electron microscopy, PHASE transitions, CATHODES, DIFFRACTION patterns
Abstract

The layered oxide LiNiO2 (LNO) has been extensively investigated as a cathode active material for lithium‐ion batteries. Despite LNO's high gravimetric capacity, instability issues hinder its commercialization. It suffers from capacity loss during electrochemical cycling and is difficult to synthesize without defects. This is related to poor structural stability, leading to decomposition into the parent rock‐salt‐type oxide. In order to understand such phase transformations and to develop measures to inhibit them, the development of techniques able to image all atoms is crucial. In this study, the use of a fast, pixelated detector and 4D imaging in scanning transmission electron microscopy are explored to tackle this challenge. Selecting specific angular regions in the diffraction patterns and calculating virtual annular bright‐field images significantly enhances the contrast of the lithium atoms, such that all atoms are visible even in realistic samples. The developed technique is applied to image the layered‐to‐rock salt phase transition region. The data show that in this region, nickel atoms are in tetrahedral positions and the oxygen atoms are asymmetrically distributed. Taken together, the results shed light on the phase transformation mechanism at the atomic scale and can guide future research toward stabilizing LNO. [ABSTRACT FROM AUTHOR]

Published
2020
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45. In SituMonitoring of Thermally Induced Effects in Nickel-Rich Layered Oxide Cathode Materials at the Atomic Level

Author

Pokle, Anuj, Ahmed, Shamail, Schweidler, Simon, Bianchini, Matteo, Brezesinski, Torsten, Beyer, Andreas, Janek, Jürgen, and Volz, Kerstin

Abstract

The thermal stability of cathode active materials (CAMs) is of major importance for the safety of lithium-ion batteries (LIBs). A thorough understanding of how commercially viable layered oxide CAMs behave at the atomic length scale upon heating is indispensable for the further development of LIBs. Here, structural changes of Li(Ni0.85Co0.15Mn0.05)O2(NCM851005) at elevated temperatures are studied by in situaberration-corrected scanning transmission electron microscopy (AC-STEM). Heating NCM851005 inside the microscope under vacuum conditions enables us to observe phase transitions and other structural changes at high spatial resolutions. This has been primarily possible by establishing low-dose electron beam conditions in STEM. Specific focus is put on the evolution of inherent nanopore defects found in the primary grains, which are believed to play an important role in LIB degradation. The onset temperature of structural changes is found to be ∼175 °C, resulting in phase transformation from a layered to a rock-salt-like structure, especially at the internal interfaces, and increasing intragrain inhomogeneity. The reducing environment and heat application lead to the formation and subsequent densification of {003}- and {014}-type facets. In the light of these results, postsynthesis electrode drying processes applied under reducing environment and heat, for example, in the preparation of solid-state batteries, should be re-examined carefully.

Published
2020
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50. Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics

Author

Hanlon, Damien, primary, Backes, Claudia, additional, Doherty, Evie, additional, Cucinotta, Clotilde S., additional, Berner, Nina C., additional, Boland, Conor, additional, Lee, Kangho, additional, Harvey, Andrew, additional, Lynch, Peter, additional, Gholamvand, Zahra, additional, Zhang, Saifeng, additional, Wang, Kangpeng, additional, Moynihan, Glenn, additional, Pokle, Anuj, additional, Ramasse, Quentin M., additional, McEvoy, Niall, additional, Blau, Werner J., additional, Wang, Jun, additional, Abellan, Gonzalo, additional, Hauke, Frank, additional, Hirsch, Andreas, additional, Sanvito, Stefano, additional, O’Regan, David D., additional, Duesberg, Georg S., additional, Nicolosi, Valeria, additional, and Coleman, Jonathan N., additional

Published
2015
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