70 results on '"Geaney, H."'
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2. The influence of carrier density and doping type on lithium insertion and extraction processes at silicon surfaces
- Author
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McSweeney, W., Lotty, O., Glynn, C., Geaney, H., Holmes, J.D., and O’Dwyer, C.
- Published
- 2014
- Full Text
- View/download PDF
3. A coupled electrochemomechanical model for the cycling of a Cu15Si4-hosted silicon nanowire
- Author
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Devine, K.M., primary, O’Kiely, D., additional, Vynnycky, M., additional, Silveri, F., additional, Tommasi, A., additional, Abinaya, S., additional, Geaney, H., additional, and Ryan, K.M., additional
- Published
- 2022
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4. Cu catalized CVD of SiNWs for lithium-ion batteries
- Author
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Rondino, F., MICHELA OTTAVIANI, Moreno, M., Rufoloni, A., Della Seta, L., Orsetti, V., Geaney, H., Stokes, K., Ryan, K. M., Prosini, P. P., Mauro Pasquali, and Santoni, A.
- Subjects
Cu-Catalyzed chemical vapor deposition: Li-ion batteries ,Si NWs - Published
- 2019
5. Fabrication of p-type porous GaN on silicon and epitaxial GaN
- Author
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Bilousov, O. V., Geaney, H., Carvajal, J. J., Zubialevich, V. Z., Parbrook, P. J., Díaz, F., Aguiló, M., O'Dwyer, C., Bilousov, O. V., Geaney, H., Carvajal, J. J., Zubialevich, V. Z., Parbrook, P. J., Díaz, F., Aguiló, M., and O'Dwyer, C.
- Abstract
Porous GaN layers are grown on silicon from gold or platinum catalyst seed layers, and self-catalyzed on epitaxial GaN films on sapphire. Using a Mg-based precursor, we demonstrate p-type doping of the porous GaN. Electrical measurements for p-type GaN on Si show Ohmic and Schottky behavior from gold and platinum seeded GaN, respectively. Ohmicity is attributed to the formation of a Ga2Au intermetallic. Porous p-type GaN was also achieved on epitaxial n-GaN on sapphire, and transport measurements confirm a p-n junction commensurate with a doping density of 1018 cm 3. Photoluminescence and cathodoluminescence confirm emission from Mg-acceptors in porous p-type GaN.
- Published
- 2017
6. (Invited) Fully Porous GaN p-n Junctions Fabricated by Chemical Vapor Deposition: A Green Technology towards More Efficient LEDs
- Author
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Carvajal, J. J., primary, Mena, J., additional, Bilousov, O., additional, Martinez, O., additional, Jimenez, J., additional, Zubialevich, V. Z., additional, Parbrook, P. J., additional, Geaney, H., additional, O'Dwyer, C., additional, Diaz, F., additional, and Aguilo, M., additional
- Published
- 2015
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7. Synthesis of silicon–germanium axial nanowire heterostructures in a solvent vapor growth system using indium and tin catalysts
- Author
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Mullane, E., primary, Geaney, H., additional, and Ryan, K. M., additional
- Published
- 2015
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8. Novel Solid-State Route to Nanostructured Tin, Zinc and Cerium Oxides as Potential Materials for Sensors
- Author
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Diaz, C., primary, Platoni, S., additional, Molina, A., additional, Valenzuela, M. L., additional, Geaney, H., additional, and O'Dwyer, C., additional
- Published
- 2014
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9. Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity
- Author
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Irish Government's Programme for Research in Third Level Institutions, ERC, SFI, IRC, McSweeney, W, Lotty, O, Mogili, Naga Vishnu V, Glynn, C, Geaney, H, Tanner, D.A, Holmes, J.D, O'Dwyer, C, Irish Government's Programme for Research in Third Level Institutions, ERC, SFI, IRC, McSweeney, W, Lotty, O, Mogili, Naga Vishnu V, Glynn, C, Geaney, H, Tanner, D.A, Holmes, J.D, and O'Dwyer, C
- Abstract
peer-reviewed, By using Si(100) with different dopant type (n(++)-type (As) or p-type (B)), we show how metal-assisted chemically etched (MACE) nanowires (NWs) can form with rough outer surfaces around a solid NW core for p-type NWs, and a unique, defined mesoporous structure for highly doped n-type NWs. We used high resolution electron microscopy techniques to define the characteristic roughening and mesoporous structure within the NWs and how such structures can form due to a judicious choice of carrier concentration and dopant type. The n-type NWs have a mesoporosity that is defined by equidistant pores in all directions, and the inter-pore distance is correlated to the effective depletion region width at the reduction potential of the catalyst at the silicon surface in a HF electrolyte. Clumping in n-type MACE Si NWs is also shown to be characteristic of mesoporous NWs when etched as high density NW layers, due to low rigidity (high porosity). Electrical transport investigations show that the etched nanowires exhibit tunable conductance changes, where the largest resistance increase is found for highly mesoporous n-type Si NWs, in spite of their very high electronic carrier concentration. This understanding can be adapted to any low-dimensional semiconducting system capable of selective etching through electroless, and possibly electrochemical, means. The process points to a method of multiscale nanostructuring NWs, from surface roughening of NWs with controllable lengths to defined mesoporosity formation, and may be applicable to applications where high surface area, electrical connectivity, tunable surface structure, and internal porosity are required. (C) 2013 AIP Publishing LLC., PUBLISHED
- Published
- 2013
10. Fabrication of p-type porous GaN on silicon and epitaxial GaN
- Author
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Bilousov, O. V., primary, Geaney, H., additional, Carvajal, J. J., additional, Zubialevich, V. Z., additional, Parbrook, P. J., additional, Giguère, A., additional, Drouin, D., additional, Díaz, F., additional, Aguiló, M., additional, and O'Dwyer, C., additional
- Published
- 2013
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11. Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity
- Author
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McSweeney, W., primary, Lotty, O., additional, Mogili, N. V. V., additional, Glynn, C., additional, Geaney, H., additional, Tanner, D., additional, Holmes, J. D., additional, and O'Dwyer, C., additional
- Published
- 2013
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12. Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte
- Author
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Hugh Geaney, Fathima Laffir, Dylan Storan, Killian Stokes, Tadhg Kennedy, Kevin M. Ryan, Giovanni Battista Appetecchi, Stefano Passerini, Guk-Tae Kim, SFI, ERC, EU, European Union (EU), IRC, Horizon 2020, Stokes, K., Kennedy, T., Kim, G. -T., Geaney, H., Storan, D., Laffir, F., Appetecchi, G. B., Passerini, S., and Ryan, K. M.
- Subjects
Materials science ,Bioengineering ,02 engineering and technology ,Electrolyte ,electrolyte ,Electrochemistry ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,ex-situ ,General Materials Science ,ionic liquid ,Mechanical Engineering ,xx-situ ,General Chemistry ,SEI ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Silicate ,Anode ,silicon nanowires ,chemistry ,Chemical engineering ,Ionic liquid ,Degradation (geology) ,Carbonate ,0210 nano-technology - Abstract
peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 10/07/2021 Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAhg-1) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13FSI-0.3PYR13TFSI) . We show using post-mortem SEM and TEM, a distinct difference in morphologies of the active material after cycling in the presence or absence of the additives. The difference in performance is shown by post-mortem XPS analysis to arise from a notable increase in irreversible silicate formation in the absence of the carbonate additives. The composition of the solid electrolyte interphase (SEI) formed at the active material surface was further analysed using XPS as a function of the IL components revealing that the SEI was primarily made up of N, F and S containing compounds from the degradation of the TFSI and FSI anions.
- Published
- 2020
13. Electrophoretic assisted fabrication of additive-free WS 2 nanosheet anodes for high energy density lithium-ion batteries.
- Author
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Pham XM, Patil NN, Abdul Ahad S, Kapuria N, Owusu KA, Geaney H, Singh S, and Ryan KM
- Abstract
2D WS
2 nanosheets (NSs) are gaining popularity in the domain of Li-ion batteries (LIBs) due to their unique structures, which can enable reversible insertion and extraction of alkali metal ions. While synthesis methods have mostly relied on the exfoliation of bulk materials or direct growth on substrates, here we report an alternative approach involving colloidal hot-injection synthesis of 2D WS2 in 2H and 1T' crystal phases followed by their electrophoretic deposition (EPD) on the current collector. The produced 2D WS2 NSs' films do not require any additional additives during deposition, which boosts the energy density of the additive-free LIBs produced. The 1T' and 2H NSs exhibit long-term stable cyclic performance at C/5 for 600 cycles. At a high cycling rate (1C), the 2H NSs outperform the 1T' NSs, delivering a 1st cycle reversible capacity of 513 mA h g-1 with capacity retention of 73% after 100 cycles (compared to 205 mA h g-1 , and 84 mA h g-1 respectively for NS-1T'). Post-cycling investigation confirms that there is no leaching or cracking of the active material on the surface of anodes after 100 cycles at C/5, which enables mechanical stability, and impressive battery performance of the WS2 NS electrodes.- Published
- 2024
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14. Enhancing Magnesium-Ion Storage in a Bi-Sn Anode through Dual-Phase Engineering.
- Author
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Rashad M, Ngoipala A, Vandichel M, and Geaney H
- Abstract
Magnesium-ion batteries (MIBs) are a "beyond Li-ion" technology that are hampered by Mg metal reactivity, which motivates the development of anode materials such as tin (Sn) with high theoretical capacity (903 mAh g
-1 ). However, pure Sn is inactive for Mg2+ storage. Herein, Mg alloying with Sn is enabled within dual-phase Bi-Sn anodes, where the optimal composition (Bi66.5 Sn33.5 ) outperformed single-phase Bi and Sn electrodes to deliver high specific capacity (462 mAh g-1 at 100 mA g-1 ), good cycle life (84% after 200 cycles), and significantly improved rate capability (403 mAh g-1 at 1000 mA g-1 ). Density functional theory (DFT) calculations revealed that Mg alloys first with Bi and the subsequent formation of the Mg3 Bi2 //Sn interfaces is energetically more favorable compared to the individual Mg3 Bi2 and Sn phases. Mg insertion into Sn is facilitated when Mg3 Bi2 is present. Moreover, dealloying Mg from Mg3 Bi2 :Mg2 Sn systems requires the creation of Mg vacancies and subsequent Mg diffusion. Mg vacancy creation is easier for Mg2 Sn compared to Mg3 Bi2 , while the latter has slightly lower activated Mg-diffusion pathways. The computational findings point toward easier magnesiation/demagnesiation for BiSn alloys over pure Bi or pure Sn, corroborating the superior Mg storage performance of Bi-Sn electrodes over the corresponding single-phase electrodes.- Published
- 2024
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15. Marine waste derived carbon materials for use as sulfur hosts for Lithium-Sulfur batteries.
- Author
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Forde R, Brandão ATSC, Bowman D, State S, Costa R, Enache LB, Enachescu M, Pereira CM, Ryan KM, Geaney H, and McNulty D
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- X-Ray Diffraction, Spectrum Analysis, Raman, Lithium chemistry, Sulfur chemistry, Electric Power Supplies, Carbon chemistry, Electrodes, Waste Products
- Abstract
Lithium-sulfur batteries are a promising alternative to lithium-ion batteries as they can potentially offer significantly increased capacities and energy densities. The ever-increasing global battery market demonstrates that there will be an ongoing demand for cost effective battery electrode materials. Materials derived from waste products can simultaneously address two of the greatest challenges of today, i.e., waste management and the requirement to develop sustainable materials. In this study, we detail the carbonisation of gelatin from blue shark and chitin from prawns, both of which are currently considered as waste biproducts of the seafood industry. The chemical and physical properties of the resulting carbons are compared through a correlation of results from structural characterisation techniques, including electron imaging, X-ray diffraction, Raman spectroscopy and nitrogen gas adsorption. We investigated the application of the resulting carbons as sulfur-hosting electrode materials for use in lithium-sulfur batteries. Through comprehensive electrochemical characterisation, we demonstrate that value added porous carbons, derived from marine waste are promising electrode materials for lithium-sulfur batteries. Both samples demonstrated impressive capacity retention when galvanostatically cycled at a rate of C/5 for 500 cycles. This study highlights the importance of looking towards waste products as sustainable feeds for battery material production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2024
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16. Binder-Free Anodes for Potassium-ion Batteries Comprising Antimony Nanoparticles on Carbon Nanotubes Obtained Using Electrophoretic Deposition.
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Pham XM, Abdul Ahad S, Patil NN, Zubair M, Mushtaq M, Gao H, Owusu KA, Kennedy T, Geaney H, Singh S, and Ryan KM
- Abstract
Antimony has a high theoretical capacity and suitable alloying/dealloying potentials to make it a future anode for potassium-ion batteries (PIBs); however, substantial volumetric changes, severe pulverization, and active mass delamination from the Cu foil during potassiation/depotassiation need to be overcome. Herein, we present the use of electrophoretic deposition (EPD) to fabricate binder-free electrodes consisting of Sb nanoparticles (NPs) embedded in interconnected multiwalled carbon nanotubes (MWCNTs). The anode architecture allows volume changes to be accommodated and prevents Sb delamination within the binder-free electrodes. The Sb mass ratio of the Sb/CNT nanocomposites was varied, with the optimized Sb/CNT nanocomposite delivering a high reversible capacity of 341.30 mA h g
-1 (∼90% of the initial charge capacity) after 300 cycles at C/5 and 185.69 mA h g-1 after 300 cycles at 1C. Postcycling investigations reveal that the stable performance is due to the unique Sb/CNT nanocomposite structure, which can be retained over extended cycling, protecting Sb NPs from volume changes and retaining the integrity of the electrode. Our findings not only suggest a facile fabrication method for high-performance alloy-based anodes in PIBs but also encourage the development of alloying-based anodes for next-generation PIBs.- Published
- 2024
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17. Revealing Seed-Mediated Structural Evolution of Copper-Silicide Nanostructures: Generating Structured Current Collectors for Rechargeable Batteries.
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Sankaran A, Kapuria N, Beloshapkin S, Ahad SA, Singh S, Geaney H, and Ryan KM
- Abstract
Metal silicide thin films and nanostructures typically employed in electronics have recently gained significant attention in battery technology, where they are used as active or inactive materials. However, unlike thin films, the science behind the evolution of silicide nanostructures, especially 1D nanowires (NWs), is a key missing aspect. Cu
x Siy nanostructures synthesized by solvent vapor growth technique are studied as a model system to gain insights into metal silicide formation. The temperature-dependent phase evolution of Cux Siy structures proceeds from Cu>Cu0.83 Si0.17 >Cu5 Si>Cu15 Si4 . The role of Cu diffusion kinetics on the morphological progression of Cu silicides is studied, revealing that the growth of 1D metal silicide NWs proceeds through an in situ formed, Cu seed-mediated, self-catalytic process. The different Cux Siy morphologies synthesized are utilized as structured current collectors for K-ion battery anodes. Sb deposited by thermal evaporation upon Cu15 Si4 tripod NWs and cube architectures exhibit reversible alloying capacities of 477.3 and 477.6 mAh g-1 at a C/5 rate. Furthermore, Sb deposited Cu15 Si4 tripod NWs anode tested in Li-ion and Na-ion batteries demonstrate reversible capacities of ≈518 and 495 mAh g-1 ., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)- Published
- 2024
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18. Real-Time TEM Observation of the Role of Defects on Nickel Silicide Propagation in Silicon Nanowires.
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Adegoke TE, Bekarevich R, Geaney H, Belochapkine S, Bangert U, and Ryan KM
- Abstract
Metal silicides have received significant attention due to their high process compatibility, low resistivity, and structural stability. In nanowire (NW) form, they have been widely prepared using metal diffusion into preformed Si NWs, enabling compositionally controlled high-quality metal silicide nanostructures. However, unlocking the full potential of metal silicide NWs for next-generation nanodevices requires an increased level of mechanistic understanding of this diffusion-driven transformation. Herein, using in situ transmission electron microscopy (TEM), we investigated the defect-controlled silicide formation dynamics in one-dimensional NWs. A solution-based synthetic route was developed to form Si NWs anchored to Ni NW stems as an optimal platform for in situ TEM studies of metal silicide formation. Multiple in situ annealing experiments led to Ni diffusion from the Ni NW stem into the Si NW, forming a nickel silicide. We observed the dynamics of Ni propagation in straight and kinked Si NWs, with some regions of the NWs acting as Ni sinks. In NWs with high defect distribution, we obtained direct evidence of nonuniform Ni diffusion and silicide retardation. The findings of this study provide insights into metal diffusion and silicide formation in complex NW structures, which are crucial from fundamental and application perspectives.
- Published
- 2024
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19. Binder-free germanium nanoparticle decorated multi-wall carbon nanotube anodes prepared via two-step electrophoretic deposition for high capacity Li-ion batteries.
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Pham XM, Abdul Ahad S, Patil NN, Geaney H, Singh S, and Ryan KM
- Abstract
Germanium (Ge) has a high theoretical specific capacity (1384 mA h g
-1 ) and fast lithium-ion diffusivity, which makes it an attractive anode material for lithium-ion batteries (LIBs). However, large volume changes during lithiation can lead to poor capacity retention and rate capability. Here, electrophoretic deposition (EPD) is used as a facile strategy to prepare Ge nanoparticle carbon-nanotube (Ge/CNT) electrodes. The Ge and CNT mass ratio in the Ge/CNT nanocomposites can be controlled by varying the deposition time, voltage, and concentration of the Ge NP dispersion in the EPD process. The optimized Ge/CNT nanocomposite exhibited long-term cyclic stability, with a capacity of 819 mA h g-1 after 1000 cycles at C/5 and a reversible capacity of 686 mA h g-1 after 350 cycles (with a minuscule capacity loss of 0.07% per cycle) at 1C. The Ge/CNT nanocomposite electrodes delivered dramatically improved cycling stability compared to control Ge nanoparticles. This can be attributed to the synergistic effects of implanting Ge into a 3D interconnected CNT network which acts as a buffer layer to accommodate the volume expansion of Ge NPs during lithiation/delithiation, limiting cracking and/or crumbling, to retain the integrity of the Ge/CNT nanocomposite electrodes.- Published
- 2024
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20. Si Nanowires: From Model System to Practical Li-Ion Anode Material and Beyond.
- Author
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Ahad SA, Kennedy T, and Geaney H
- Abstract
Nanowire (NW)-based anodes for Li-ion batteries (LIBs) have been under investigation for more than a decade, with their unique one-dimensional (1D) morphologies and ability to transform into interconnected active material networks offering potential for enhanced cycling stability with high capacity. This is particularly true for silicon (Si)-based anodes, where issues related to large volumetric expansion can be partially mitigated and the cycle life can be enhanced. In this Perspective, we highlight the trajectory of Si NWs from a model system to practical Li-ion battery anode material and future prospects for extension to beyond Li-ion batteries. The study examines key research areas related to Si NW-based anodes, including state-of-the-art (SoA) characterization approaches followed by practical anode design considerations, including NW composite anode formation and upscaling/full-cell considerations. An outlook on the practical prospects of NW-based anodes and some future directions for study are detailed., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)
- Published
- 2024
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21. Cobalt Oxide 2D Nanosheets Formed at a Polarized Liquid|Liquid Interface toward High-Performance Li-Ion and Na-Ion Battery Anodes.
- Author
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Konkena B, Kalapu C, Kaur H, Holzinger A, Geaney H, Nicolosi V, Scanlon MD, and Coleman JN
- Abstract
Cobalt oxide (Co
3 O4 )-based nanostructures have the potential as low-cost materials for lithium-ion (Li-ion) and sodium-ion (Na-ion) battery anodes with a theoretical capacity of 890 mAh/g. Here, we demonstrate a novel method for the production of Co3 O4 nanoplatelets. This involves the growth of flower-like cobalt oxyhydroxide (CoOOH) nanostructures at a polarized liquid|liquid interface, followed by conversion to flower-like Co3 O4 via calcination. Finally, sonication is used to break up the flower-like Co3 O4 nanostructures into two-dimensional (2D) nanoplatelets with lateral sizes of 20-100 nm. Nanoplatelets of Co3 O4 can be easily mixed with carbon nanotubes to create nanocomposite anodes, which can be used for Li-ion and Na-ion battery anodes without any additional binder or conductive additive. The resultant electrodes display impressive low-rate capacities (at 125 mA/g) of 1108 and 1083 mAh/g, for Li-ion and Na-ion anodes, respectively, and stable cycling ability over >200 cycles. Detailed quantitative rate analysis clearly shows that Li-ion-storing anodes charge roughly five times faster than Na-ion-storing anodes.- Published
- 2023
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22. Solution processable Si/Ge heterostructure NWs enabling anode mass reduction for practical full-cell Li-ion batteries.
- Author
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Adegoke TE, Abdul Ahad S, Bangert U, Geaney H, and Ryan KM
- Abstract
Here, we report the solution phase synthesis of axial heterostructure Si and Ge (hSG) nanowires (NWs). The NWs were grown in a high boiling point solvent from a low-cost Sn powder to achieve a powder form product which represents an attractive route from lab-scale to commercial application. Slurry processed anodes of the NWs were investigated in half-cell ( versus Li-foil) and full-cell ( versus NMC811) configurations of a lithium ion battery (LIB). The hSG NW anodes yielded capacities of 1040 mA h g
-1 after 150 cycles which corresponds to a 2.8 times increase compared to a standard graphite (372 mA h g-1 ) anode. Given the impressive specific and areal capacities of the hSG anodes, a full-cell test against a high areal capacity NMC811 cathode was examined. In full-cell configuration, use of the hSG anode resulted in a massive anode mass reduction of 50.7% compared to a standard graphite anode. The structural evolution of the hSG NW anodes into an alloyed SiGe porous mesh network was also investigated using STEM, EDX and Raman spectroscopy as a function of cycle number to fully elucidate the lithiation/delithiation mechanism of the promising anode material., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2023
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23. Colloidal synthesis of the mixed ionic-electronic conducting NaSbS 2 nanocrystals.
- Author
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Zubair M, Ahad SA, Amiinu IS, Lebedev VA, Mishra M, Geaney H, Singh S, and Ryan KM
- Abstract
Solution-based synthesis of mixed ionic and electronic conductors (MIECs) has enabled the development of novel inorganic materials with implications for a wide range of energy storage applications. However, many technologically relevant MIECs contain toxic elements (Pb) or are prepared by using traditional high-temperature solid-state synthesis. Here, we provide a simple, low-temperature and size-tunable (50-90 nm) colloidal hot injection approach for the synthesis of NaSbS
2 based MIECs using widely available and non-toxic precursors. Key synthetic parameters (cationic precursor, reaction temperature, and ligand) are examined to regulate the shape and size of the NaSbS2 nanocrystals (NCs). FTIR studies revealed that ligands with carboxylate functionality are coordinated to the surface of the synthesized NaSbS2 NCs. The synthesized NaSbS2 nanocrystals have electronic and ionic conductivities of 3.31 × 10-10 (e- ) and 1.9 × 10-5 (Na+ ) S cm-1 respectively, which are competitive with the ionic and electrical conductivities of perovskite materials generated by solid-state reactions. This research gives a mechanistic understanding and post-synthetic evaluation of parameters influencing the formation of sodium antimony chalcogenides materials.- Published
- 2023
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24. Cu Current Collector with Binder-Free Lithiophilic Nanowire Coating for High Energy Density Lithium Metal Batteries.
- Author
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Abdul Ahad S, Adegoke TE, Ryan KM, and Geaney H
- Abstract
Despite significant efforts to fabricate high energy density (ED) lithium (Li) metal anodes, problems such as dendrite formation and the need for excess Li (leading to low N/P ratios) have hampered Li metal battery (LMB) development. Here, the use of germanium (Ge) nanowires (NWs) directly grown on copper (Cu) substrates (Cu-Ge) to induce lithiophilicity and subsequently guide Li ions for uniform Li metal deposition/stripping during electrochemical cycling is reported. The NW morphology along with the formation of the Li
15 Ge4 phase promotes uniform Li-ion flux and fast charge kinetic, resulting in the Cu-Ge substrate demonstrating low nucleation overpotentials of 10 mV (four times lower than planar Cu) and high Columbic efficiency (CE) efficiency during Li plating/stripping. Within a full-cell configuration, the Cu-Ge@Li - NMC cell delivered a 63.6% weight reduction at the anode level compared to a standard graphite-based anode, with impressive capacity retention and average CE of over 86.5% and 99.2% respectively. The Cu-Ge anodes are also paired with high specific capacity sulfur (S) cathodes, further demonstrating the benefits of developing surface-modified lithiophilic Cu current collectors, which can easily be integrated at the industrial scale., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)- Published
- 2023
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25. Lithiophilic Nanowire Guided Li Deposition in Li Metal Batteries.
- Author
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Abdul Ahad S, Bhattacharya S, Kilian S, Ottaviani M, Ryan KM, Kennedy T, Thompson D, and Geaney H
- Abstract
Lithium (Li) metal batteries (LMBs) provide superior energy densities far beyond current Li-ion batteries (LIBs) but practical applications are hindered by uncontrolled dendrite formation and the build-up of dead Li in "hostless" Li metal anodes. To circumvent these issues, we created a 3D framework of a carbon paper (CP) substrate decorated with lithiophilic nanowires (silicon (Si), germanium (Ge), and SiGe alloy NWs) that provides a robust host for efficient stripping/plating of Li metal. The lithiophilic Li
22 Si5 , Li22 (Si0.5 Ge0.5 )5, and Li22 Ge5 formed during rapid Li melt infiltration prevented the formation of dead Li and dendrites. Li22 Ge5 /Li covered CP hosts delivered the best performance, with the lowest overpotentials of 40 mV (three times lower than pristine Li) when cycled at 1 mA cm-2 /1 mAh cm-2 for 1000 h and at 3 mA cm-2 /3 mAh cm-2 for 500 h. Ex situ analysis confirmed the ability of the lithiophilic Li22 Ge5 decorated samples to facilitate uniform Li deposition. When paired with sulfur, LiFePO4, and NMC811 cathodes, the CP-LiGe/Li anodes delivered 200 cycles with 82%, 93%, and 90% capacity retention, respectively. The discovery of the highly stable, lithiophilic NW decorated CP hosts is a promising route toward stable cycling LMBs and provides a new design motif for hosted Li metal anodes., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)- Published
- 2023
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26. Multipod Bi(Cu 2-x S) n Nanocrystals formed by Dynamic Cation-Ligand Complexation and Their Use as Anodes for Potassium-Ion Batteries.
- Author
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Kapuria N, Imtiaz S, Sankaran A, Geaney H, Kennedy T, Singh S, and Ryan KM
- Subjects
- Ligands, Cations, Electrodes, Potassium, Nanoparticles
- Abstract
We report the formation of an intermediate lamellar Cu-thiolate complex, and tuning its relative stability using alkylphosphonic acids are crucial to enabling controlled heteronucleation to form Bi(Cu
2- x S)n heterostructures with a tunable number of Cu2- x S stems on a Bi core. The denticity of the phosphonic acid group, concentration, and chain length of alkylphosphonic acids are critical factors determining the stability of the Cu-thiolate complex. Increasing the stability of the Cu-thiolate results in single Cu2- x S stem formation, and decreased stability of the Cu-thiolate complex increases the degree of heteronucleation to form multiple Cu2- x S stems on the Bi core. Spatially separated multiple Cu2- x S stems transform into a support network to hold a fragmented Bi core when used as an anode in a K-ion battery, leading to a more stable cycling performance showing a specific capacity of ∼170 mAh·g-1 after 200 cycles compared to ∼111 mAh·g-1 for Bi-Cu2- x S single-stem heterostructures.- Published
- 2022
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27. Dense Silicon Nanowire Networks Grown on a Stainless-Steel Fiber Cloth: A Flexible and Robust Anode for Lithium-Ion Batteries.
- Author
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Imtiaz S, Amiinu IS, Storan D, Kapuria N, Geaney H, Kennedy T, and Ryan KM
- Abstract
Silicon nanowires (Si NWs) are a promising anode material for lithium-ion batteries (LIBs) due to their high specific capacity. Achieving adequate mass loadings for binder-free Si NWs is restricted by low surface area, mechanically unstable and poorly conductive current collectors (CCs), as well as complicated/expensive fabrication routes. Herein, a tunable mass loading and dense Si NW growth on a conductive, flexible, fire-resistant, and mechanically robust interwoven stainless-steel fiber cloth (SSFC) using a simple glassware setup is reported. The SSFC CC facilitates dense growth of Si NWs where its open structure allows a buffer space for expansion/contraction during Li-cycling. The Si NWs@SSFC anode displays a stable performance for 500 cycles with an average Coulombic efficiency of >99.5%. Galvanostatic cycling of the Si NWs@SSFC anode with a mass loading of 1.32 mg cm
-2 achieves a stable areal capacity of ≈2 mAh cm-2 at 0.2 C after 200 cycles. Si NWs@SSFC anodes with different mass loadings are characterized before and after cycling by scanning and transmission electron microscopy to examine the effects of Li-cycling on the morphology. Notably, this approach allows the large-scale fabrication of robust and flexible binder-free Si NWs@SSFC architectures, making it viable for practical applications in high energy density LIBs., (© 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH.)- Published
- 2021
- Full Text
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28. Temperature induced diameter variation of silicon nanowires via a liquid-solid phase transition in the Zn seed.
- Author
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Kilian S, Adegoke TE, Ahad SA, Geaney H, Kennedy T, and Ryan KM
- Subjects
- Catalysis, Phase Transition, Temperature, Nanowires chemistry, Silicon chemistry, Zinc chemistry
- Abstract
Herein, we demonstrate the ability of Zn to catalyze the growth of Si nanowires via reaction temperature determined, vapour-liquid-solid (VLS) or vapour-solid-solid (VSS) growth mechanisms. This is the first reported use of a type B catalyst to grow Si nanowires via the VSS mechanism to our knowledge whereby the highly faceted Zn seeds resulted in an increased NW diameter. This was used to induce diameter variations along the axial length of individual nanowires by transitioning between VLS and VSS growth.
- Published
- 2021
- Full Text
- View/download PDF
29. A Nanowire Nest Structure Comprising Copper Silicide and Silicon Nanowires for Lithium-Ion Battery Anodes with High Areal Loading.
- Author
-
Collins GA, Kilian S, Geaney H, and Ryan KM
- Abstract
High loading (>1.6 mg cm
-2 ) of Si nanowires (NWs) is achieved by seeding the growth from a dense array of Cu15 Si4 NWs using tin seeds. A one-pot synthetic approach involves the direct growth of CuSi NWs on Cu foil that acts as a textured surface for Sn adhesion and Si NW nucleation. The high achievable Si NW loading is enabled by the high surface area of CuSi NWs and bolstered by secondary growth of Si NWs as branches from both Si and CuSi NW stems, forming a dense Si active layer, interconnected with an electrically conducting CuSi array (denoted Si/CuSi). When employed as Li-ion battery anodes, the Si/CuSi nest structure demonstrates impressive rate performance, reaching 4.1 mAh cm-2 at C/20, 3.1 mAh cm-2 at C/5, and 0.8 mAh cm-2 at 6C. Also, Si/CuSi shows remarkable long-term stability, delivering a stable areal capacity of 2.2 mAh cm-2 after 300 cycles. Overall, complete anode fabrication is achieved within a single reaction by employing an inexpensive Sn powder approach., (© 2021 The Authors. Small published by Wiley-VCH GmbH.)- Published
- 2021
- Full Text
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30. Direct Growth of Si, Ge, and Si-Ge Heterostructure Nanowires Using Electroplated Zn: An Inexpensive Seeding Technique for Li-Ion Alloying Anodes.
- Author
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Kilian S, McCarthy K, Stokes K, Adegoke TE, Conroy M, Amiinu IS, Geaney H, Kennedy T, and Ryan KM
- Abstract
A scalable and cost-effective process is used to electroplate metallic Zn seeds on stainless steel substrates. Si and Ge nanowires (NWs) are subsequently grown by placing the electroplated substrates in the solution phase of a refluxing organic solvent at temperatures >430 °C and injecting the respective liquid precursors. The native oxide layer formed on reactive metals such as Zn can obstruct NW growth and is removed in situ by injecting the reducing agent LiBH
4 . The findings show that the use of Zn as a catalyst produces defect-rich Si NWs that can be extended to the synthesis of Si-Ge axial heterostructure NWs with an atomically abrupt Si-Ge interface. As an anode material, the as grown Zn seeded Si NWs yield an initial discharge capacity of 1772 mAh g-1 and a high capacity retention of 85% after 100 cycles with the active participation of both Si and Zn during cycling. Notably, the Zn seeds actively participate in the Li-cycling activities by incorporating into the Si NWs body via a Li-assisted welding process, resulting in restructuring the NWs into a highly porous network structure that maintains a stable cycling performance., (© 2021 Wiley-VCH GmbH.)- Published
- 2021
- Full Text
- View/download PDF
31. Alloying Germanium Nanowire Anodes Dramatically Outperform Graphite Anodes in Full-Cell Chemistries over a Wide Temperature Range.
- Author
-
Collins GA, McNamara K, Kilian S, Geaney H, and Ryan KM
- Abstract
The electrochemical performance of Ge, an alloying anode in the form of directly grown nanowires (NWs), in Li-ion full cells (vs LiCoO
2 ) was analyzed over a wide temperature range (-40 to 40 °C). LiCoO2 ||Ge cells in a standard electrolyte exhibited specific capacities 30× and 50× those of LiCoO2 ||C cells at -20 and -40 °C, respectively. We further show that propylene carbonate addition further improved the low-temperature performance of LiCoO2 ||Ge cells, achieving a specific capacity of 1091 mA h g-1 after 400 cycles when charged/discharged at -20 °C. At 40 °C, an additive mixture of ethyl methyl carbonate and lithium bis(oxalato)borate stabilized the capacity fade from 0.22 to 0.07% cycle-1 . Similar electrolyte additives in LiCoO2 ||C cells did not allow for any gains in performance. Interestingly, the capacity retention of LiCoO2 ||Ge improved at low temperatures due to delayed amorphization of crystalline NWs, suppressing complete lithiation and high-order Li15 Ge4 phase formation. The results show that alloying anodes in suitably configured electrolytes can deliver high performance at the extremes of temperature ranges where electric vehicles operate, conditions that are currently not viable for commercial batteries without energy-inefficient temperature regulation., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)- Published
- 2021
- Full Text
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32. Colloidal WSe 2 nanocrystals as anodes for lithium-ion batteries.
- Author
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Zhou P, Collins G, Hens Z, Ryan KM, Geaney H, and Singh S
- Abstract
Transition metal dichalcogenides (TMDs) are gaining increasing interest in the field of lithium ion batteries due to their unique structure. However, previous preparation methods have mainly focused on their growth from substrates or by exfoliation of the bulk materials. Considering colloidal synthesis has many advantages including precision control of morphology and crystal phases, there is significant scope for exploring this avenue for active material formation. Therefore, in this work, we explore the applicability of colloidal TMDs using WSe
2 nanocrystals for Li ion battery anodes. By employing colloidal hot-injection protocol, we first synthesize 2D nanosheets in 2H and 1T' crystal phases. After detailed structural and surface characterization, we investigate the performance of these nanosheets as anode materials. We found that 2H nanosheets outperformed 1T' nanosheets exhibiting a higher specific capacity of 498 mA h g-1 with an overall capacity retention of 83.28%. Furthermore, to explore the role of morphology on battery performance, 3D interconnected nanoflowers in 2H crystal phase were also investigated as an anode material. It is worth noting that a specific capacity of 982 mA h g-1 was exhibited after 100 cycles by these nanoflowers. The anode materials were characterized prior to cycling and after 1, 25, and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material.- Published
- 2020
- Full Text
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33. Influence of Carbonate-Based Additives on the Electrochemical Performance of Si NW Anodes Cycled in an Ionic Liquid Electrolyte.
- Author
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Stokes K, Kennedy T, Kim GT, Geaney H, Storan D, Laffir F, Appetecchi GB, Passerini S, and Ryan KM
- Abstract
Addition of electrolyte additives (ethylene or vinylene carbonate) is shown to dramatically improve the cycling stability and capacity retention (1600 mAh g
-1 ) of Si nanowires (NWs) in a safe ionic liquid (IL) electrolyte (0.1LiTFSI-0.6PYR13 FSI-0.3PYR13 TFSI). We show, using postmortem SEM and TEM, a distinct difference in morphologies of the active material after cycling in the presence or absence of the additives. The difference in performance is shown by postmortem XPS analysis to arise from a notable increase in irreversible silicate formation in the absence of the carbonate additives. The composition of the solid electrolyte interphase (SEI) formed at the active material surface was further analyzed using XPS as a function of the IL components revealing that the SEI was primarily made up of N-, F-, and S-containing compounds from the degradation of the TFSI and FSI anions.- Published
- 2020
- Full Text
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34. Copper Silicide Nanowires as Hosts for Amorphous Si Deposition as a Route to Produce High Capacity Lithium-Ion Battery Anodes.
- Author
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Stokes K, Geaney H, Sheehan M, Borsa D, and Ryan KM
- Abstract
Herein, copper silicide (Cu
15 Si4 ) nanowires (NWs) grown in high densities from a metallic Cu substrate are utilized as nanostructured hosts for amorphous silicon (aSi) deposition. The conductive Cu15 Si4 NW scaffolds offer an increased surface area, versus planar substrates, and enable the preparation of high capacity Li-ion anodes consisting of a nanostructured active material. The formation method involves a two-step process, where Cu15 Si4 nanowires are synthesized from a Cu substrate via a solvent vapor growth (SVG) approach followed by the plasma-enhanced chemical vapor deposition (PECVD) of aSi. These binder-free anodes are investigated in half-cell (versus Li-foil) and full-cell (versus LCO) configurations with discharge capacities greater than 2000 mAh/g retained after 200 cycles (half-cell) and reversible capacities of 1870 mAh/g exhibited after 100 cycles (full-cell). A noteworthy rate capability is also attained where capacities of up to 1367 mAh/g and 1520 mAh/g are exhibited at 5C in half-cell and full-cell configurations, respectively, highlighting the active material's promise for fast charging and high power applications. The anode material is characterized prior to cycling and after 1, 25, and 100 charge/discharge cycles, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to track the effects of cycling on the material.- Published
- 2019
- Full Text
- View/download PDF
35. Bio-derived Carbon Nanofibres from Lignin as High-Performance Li-Ion Anode Materials.
- Author
-
Culebras M, Geaney H, Beaucamp A, Upadhyaya P, Dalton E, Ryan KM, and Collins MN
- Abstract
Development of cost-effective and increasingly efficient sustainable materials for energy-storage devices, such Li-ion batteries, is of crucial future importance. Herein, the preparation of carbon nanofibres from biopolymer blends of lignin (byproduct from the paper and pulp industry) and polylactic acid (PLA) or a thermoplastic elastomeric polyurethane (TPU) is described. SEM analysis shows the evolving microstructural morphology after each processing step (electrospinning, stabilisation and carbonisation). Importantly, it is possible to tailor the nanofibre porosity by utilising miscibility/immiscibility rules between lignin and the polymer additive (PLA/TPU). PLA blends (immiscible) generate porous structures whereas miscible lignin/TPU blends are solid when carbonised. Electrodes produced from 50 % PLA blends have capacity values of 611 mAh g
-1 after 500 charge/discharge cycles, the highest reported to date for sustainable electrodes for Li-ion batteries. Thus, this work will promote the development of lignocellulose waste materials as high-performance energy-storage materials., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2019
- Full Text
- View/download PDF
36. Enhancing the performance of germanium nanowire anodes for Li-ion batteries by direct growth on textured copper.
- Author
-
Geaney H, Bree G, Stokes K, Collins GA, Aminu IS, Kennedy T, and Ryan KM
- Abstract
Herein, textured Cu foil is presented as an attractive current collector substrate for directly grown Ge nanowire (NW) anodes. Compared to planar stainless steel (SS) current collectors, textured Cu led to an increase in achievable mass loading, removal of the requirement for a catalyst deposition step, improved adhesion of the active material and dramatically enhanced capacity retention. When SS and textured Cu foil based anodes with similar areal loadings (∼1.4 mA h cm-2) were compared, the capacity after 250 cycles for textured Cu was 2.7 times higher than the SS anode, illustrating the key role of the current collector.
- Published
- 2019
- Full Text
- View/download PDF
37. Tunable Core-Shell Nanowire Active Material for High Capacity Li-Ion Battery Anodes Comprised of PECVD Deposited aSi on Directly Grown Ge Nanowires.
- Author
-
Stokes K, Boonen W, Geaney H, Kennedy T, Borsa D, and Ryan KM
- Abstract
Herein, we report the formation of core@shell nanowires (NWs) comprised of crystalline germanium NW cores with amorphous silicon shells (Ge@aSi) and their performance as a high capacity Li-ion battery anode material. The Ge NWs were synthesized directly from the current collector in a solvent vapor growth (SVG) system and used as hosts for the deposition of the Si shells via a plasma-enhanced chemical vapor deposition (PECVD) process utilizing an expanding thermal plasma (ETP) source. The secondary deposition allows for the preparation of Ge@aSi core@shell structures with tunable Ge/Si ratios (2:1 and 1:1) and superior gravimetric and areal capacities, relative to pure Ge. The binder-free anodes exhibited discharge capacities of up to 2066 mAh/g and retained capacities of 1455 mAh/g after 150 cycles (for the 1:1 ratio). The 2:1 ratio showed a minimal ∼5% fade in capacity between the 20th and 150th cycles. Ex situ microscopy revealed a complete restructuring of the active material to an interconnected Si
1- x Gex morphology due to repeated lithiation and delithiation. In full-cell testing, a prelithiation step counteracted first cycle Li consumption and resulted in a 2-fold improvement to the capacity of the prelithiated cell versus the unconditioned full-cells. Remarkable rate capability was also delivered where capacities of 750 mAh/g were observed at a rate of 10 C.- Published
- 2019
- Full Text
- View/download PDF
38. Linear heterostructured Ni 2 Si/Si nanowires with abrupt interfaces synthesised in solution.
- Author
-
Sheehan M, Ramasse QM, Geaney H, and Ryan KM
- Abstract
Herein, we report a novel approach to form axial heterostructure nanowires composed of linearly distinct Ni silicide (Ni2Si) and Si segments via a one-pot solution synthesis method. Initially, Si nanowires are grown using Au seeds deposited on a Ni substrate with the Si delivery in the solution phase using a liquid phenylsilane precursor. Ni silicide then forms axially along the wires through progressive Ni diffusion from the growth substrate, with a distinct transition between the silicide and pure Si segments. The interfacial abruptness and chemical composition of the heterostructure nanowires was analysed through transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy, aberration corrected scanning transmission electron microscopy and atomically resolved electron energy loss spectroscopy. The method represents a versatile approach for the formation of complex axial NW heterostructures and could be extended to other metal silicide or analogous metal germanide systems.
- Published
- 2018
- Full Text
- View/download PDF
39. Axial Si-Ge Heterostructure Nanowires as Lithium-Ion Battery Anodes.
- Author
-
Stokes K, Flynn G, Geaney H, Bree G, and Ryan KM
- Abstract
Here, we report the application of axially heterostructured nanowires consisting of alternating segments of silicon and germanium with a tin seed as lithium-ion battery anodes. During repeated lithiation and delithiation, the heterostructures completely rearrange into a porous network of homogeneously alloyed Si
1- x Gex ligaments. The transformation was characterized through ex situ TEM, STEM, and Raman spectroscopy. Electrochemical analysis was conducted on the heterostructure nanowires with discharge capacities in excess of 1180 mAh/g for 400 cycles (C/5) and capacities of up to 613 mAh/g exhibited at a rate of 10 C.- Published
- 2018
- Full Text
- View/download PDF
40. Investigation into the Selenization Mechanisms of Wurtzite CZTS Nanorods.
- Author
-
Bree G, Coughlan C, Geaney H, and Ryan KM
- Abstract
Here, we report the first detailed investigation into the selenization mechanism of thin films of wurtzite copper zinc tin sulfide (CZTS) nanorods (NRs), giving particular emphasis to the role of the long-chain organic ligands surrounding each NR. During selenization, the NRs undergo a selenium-mediated phase change from wurtzite to kesterite, concurrent with the replacement of sulfur with selenium in the lattice and in situ grain growth, along with the recrystallization of larger copper zinc tin selenide kesterite grains on top of the existing film. By utilizing a facile ligand removal technique, we demonstrate that the formation of a large-grain overlayer is achievable without the presence of ligands. In addition, we demonstrate an elegant ligand-exchange-based method for controlling the thickness of the fine-grain layer. This report emphasizes the key role played by ligands in determining the structural evolution of CZTS nanocrystal films during selenization, necessitating the identification of optimal ligand chemistries and processing conditions for desirable grain growth.
- Published
- 2018
- Full Text
- View/download PDF
41. Direct Synthesis of Alloyed Si 1-x Ge x Nanowires for Performance-Tunable Lithium Ion Battery Anodes.
- Author
-
Stokes K, Geaney H, Flynn G, Sheehan M, Kennedy T, and Ryan KM
- Abstract
Here we report the formation of high capacity Li-ion battery anodes from Si
1-x Gex alloy nanowire arrays that are grown directly on stainless steel current collectors, in a single-step synthesis. The direct formation of these Si1-x Gex nanowires (ranging from Si0.20 Ge0.80 to Si0.67 Ge0.33 ) represents a simple and efficient processing route for the production of Li-ion battery anodes possessing the benefits of both Si (high capacity) and Ge (improved rate performance and capacity retention). The nanowires were characterized through SEM, TEM, XRD and ex situ HRSEM/HRTEM. Electrochemical analysis was conducted on these nanowires, in half-cell configurations, with capacities of up to 1360 mAh/g (Si0.67 Ge0.33 ) sustained after 250 cycles and in full cells, against a commercial cathode, where capacities up to 1364 mAh/g (Si0.67 Ge0.33 ) were retained after 100 cycles.- Published
- 2017
- Full Text
- View/download PDF
42. Behavior of Germanium and Silicon Nanowire Anodes with Ionic Liquid Electrolytes.
- Author
-
Kim GT, Kennedy T, Brandon M, Geaney H, Ryan KM, Passerini S, and Appetecchi GB
- Abstract
The electrochemical behavior of binder-free, germanium and silicon nanowires as high-capacity anode materials for lithium-ion battery systems is investigated in an ionic liquid electrolyte. Cyclic voltammetry, cycling tests, and impedance spectroscopy reveal a highly reversible lithium alloying/dealloying process, as well as promising compatibility between the Ge and Si materials and the electrolyte components. Reversible capacities of 1400 and 2200 mA h g
-1 are delivered by the Ge and Si anodes, respectively, matching the values exhibited in conventional organic solutions. Furthermore, impressive extended cycling performance is obtained in comparison to previous research on Li alloying anodes in ionic liquids, with capacity retention overcoming 50% for Si after 500 cycles and 67% for Ge after 1000 cycles, at a current rate of 0.5C. This stable long-term cycling arises due to the ability of the electrolyte formulation to promote the transformation of the nanowires into durable porous network structures of Ge or Si nanoligaments, which can withstand the extreme volume changes associated with lithiation/delithiation. Remarkable capacity is exhibited also by composite Ge and Si nanowire electrodes. Preliminary tests with lithium cobalt oxide cathodes clearly demonstrate the feasibility of Ge and Si nanowires in full batteries.- Published
- 2017
- Full Text
- View/download PDF
43. Carbon-Coated Honeycomb Ni-Mn-Co-O Inverse Opal: A High Capacity Ternary Transition Metal Oxide Anode for Li-ion Batteries.
- Author
-
McNulty D, Geaney H, and O'Dwyer C
- Abstract
We present the formation of a carbon-coated honeycomb ternary Ni-Mn-Co-O inverse opal as a conversion mode anode material for Li-ion battery applications. In order to obtain high capacity via conversion mode reactions, a single phase crystalline honeycombed IO structure of Ni-Mn-Co-O material was first formed. This Ni-Mn-Co-O IO converts via reversible redox reactions and Li
2 O formation to a 3D structured matrix assembly of nanoparticles of three (MnO, CoO and NiO) oxides, that facilitates efficient reactions with Li. A carbon coating maintains the structure without clogging the open-worked IO pore morphology for electrolyte penetration and mass transport of products during cycling. The highly porous IO was compared in a Li-ion half-cell to nanoparticles of the same material and showed significant improvement in specific capacity and capacity retention. Further optimization of the system was investigated by incorporating a vinylene carbonate additive into the electrolyte solution which boosted performance, offering promising high-rate performance and good capacity retention over extended cycling. The analysis confirms the possibility of creating a ternary transition metal oxide material with binder free accessible open-worked structure to allow three conversion mode oxides to efficiently cycle as an anode material for Li-ion battery applications., Competing Interests: The authors declare no competing financial interests.- Published
- 2017
- Full Text
- View/download PDF
44. Influence of Binders and Solvents on Stability of Ru/RuO x Nanoparticles on ITO Nanocrystals as Li-O 2 Battery Cathodes.
- Author
-
Vankova S, Francia C, Amici J, Zeng J, Bodoardo S, Penazzi N, Collins G, Geaney H, and O'Dwyer C
- Subjects
- Catalysis, Electrochemistry, Electrodes, Oxidation-Reduction, Ruthenium Compounds chemistry, Electric Power Supplies, Lithium chemistry, Metal Nanoparticles chemistry, Oxygen chemistry, Ruthenium chemistry, Solvents chemistry, Tin Compounds chemistry
- Abstract
Fundamental research on Li-O
2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li-O2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1-2 nm oxygen evolution reaction (OER) catalyst Ru/RuOx nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li-O2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuOx nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuOx /ITO nanocrystalline materials in DMSO provide efficient Li2 O2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuOx NPs remain effective OER catalysts for Li2 O2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO-EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuOx /ITO materials in Li-O2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5-0.8 V., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
- Full Text
- View/download PDF
45. Growing Oxide Nanowires and Nanowire Networks by Solid State Contact Diffusion into Solution-Processed Thin Films.
- Author
-
Glynn C, McNulty D, Geaney H, and O'Dwyer C
- Abstract
New techniques to directly grow metal oxide nanowire networks without the need for initial nanoparticle seed deposition or postsynthesis nanowire casting will bridge the gap between bottom-up formation and top-down processing for many electronic, photonic, energy storage, and conversion technologies. Whether etched top-down, or grown from catalyst nanoparticles bottom-up, nanowire growth relies on heterogeneous material seeds. Converting surface oxide films, ubiquitous in the microelectronics industry, to nanowires and nanowire networks by the incorporation of extra species through interdiffusion can provide an alternative deposition method. It is shown that solution-processed thin films of oxides can be converted and recrystallized into nanowires and networks of nanowires by solid-state interdiffusion of ionic species from a mechanically contacted donor substrate. NaVO
3 nanowire networks on smooth Si/SiO2 and granular fluorine-doped tin oxide surfaces can be formed by low-temperature annealing of a Na diffusion species-containing donor glass to a solution-processed V2 O5 thin film, where recrystallization drives nanowire growth according to the crystal habit of the new oxide phase. This technique illustrates a new method for the direct formation of complex metal oxide nanowires on technologically relevant substrates, from smooth semiconductors, to transparent conducting materials and interdigitated device structures., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2016
- Full Text
- View/download PDF
46. 2D and 3D photonic crystal materials for photocatalysis and electrochemical energy storage and conversion.
- Author
-
Collins G, Armstrong E, McNulty D, O'Hanlon S, Geaney H, and O'Dwyer C
- Abstract
This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic-photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided.
- Published
- 2016
- Full Text
- View/download PDF
47. Electrodeposited Structurally Stable V2O5 Inverse Opal Networks as High Performance Thin Film Lithium Batteries.
- Author
-
Armstrong E, McNulty D, Geaney H, and O'Dwyer C
- Abstract
High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.
- Published
- 2015
- Full Text
- View/download PDF
48. Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films.
- Author
-
Glynn C, Creedon D, Geaney H, Armstrong E, Collins T, Morris MA, and O'Dwyer C
- Abstract
Solution processed metal oxide thin films are important for modern optoelectronic devices ranging from thin film transistors to photovoltaics and for functional optical coatings. Solution processed techniques such as dip-coating, allow thin films to be rapidly deposited over a large range of surfaces including curved, flexible or plastic substrates without extensive processing of comparative vapour or physical deposition methods. To increase the effectiveness and versatility of dip-coated thin films, alterations to commonly used precursors can be made that facilitate controlled thin film deposition. The effects of polymer assisted deposition and changes in solvent-alkoxide dilution on the morphology, structure, optoelectronic properties and crystallinity of vanadium pentoxide thin films was studied using a dip-coating method using a substrate withdrawal speed within the fast-rate draining regime. The formation of sub-100 nm thin films could be achieved rapidly from dilute alkoxide based precursor solutions with high optical transmission in the visible, linked to the phase and film structure. The effects of the polymer addition was shown to change the crystallized vanadium pentoxide thin films from a granular surface structure to a polycrystalline structure composed of a high density of smaller in-plane grains, resulting in a uniform surface morphology with lower thickness and roughness.
- Published
- 2015
- Full Text
- View/download PDF
49. Electrochemical investigation of the role of MnO2 nanorod catalysts in water containing and anhydrous electrolytes for Li-O2 battery applications.
- Author
-
Geaney H and O'Dwyer C
- Abstract
The electrochemical behaviour of MnO2 nanorod and Super P carbon based Li-O2 battery cathodes in water-containing sulfolane and anhydrous DMSO electrolytes are shown to be linked to specific discharge product formation. During discharge, large layered spherical agglomerates of LiOH were characteristically formed on the MnO2 cathodes while smaller, toroidal, spherical Li2O2 particles and films were formed on the Super P cathodes. In an anhydrous DMSO based electrolyte the LiOH structures were also found on cathodes discharged in the anhydrous electrolyte, suggesting that MnO2 initiates electrochemical decomposition of the DMSO electrolyte to form LiOH via H2O reactions with Li2O2. The LiOH crystals are uniquely formed on MnO2, and segregated to this phase even in mixed oxide-carbon cathodes. In contrast, no Li2O2 toroids were noted on Super P cathodes discharged in the DMSO based electrolytes. Instead, the morphology varied from smaller sheets (at high discharge current) to much larger agglomerates (at low discharge currents). In mixed carbon-MnO2 nanorod cathodes, the use of PVDF initiates H2O formation that affects discharge products and an overall mechanism governing phase formation at MnO2 in sulfolane and anhydrous DMSO with and without PVDF binder is presented. This work highlights the importance of careful consideration of electrolyte-cathode material-discharge product interactions in the search for more stable Li-O2 systems.
- Published
- 2015
- Full Text
- View/download PDF
50. A rapid, solvent-free protocol for the synthesis of germanium nanowire lithium-ion anodes with a long cycle life and high rate capability.
- Author
-
Mullane E, Kennedy T, Geaney H, and Ryan KM
- Abstract
A rapid synthetic protocol for the formation of high-performance Ge nanowire-based Li-ion battery anodes is reported. The nanowires are formed in high density by the solvent-free liquid deposition of a Ge precursor directly onto a heated stainless steel substrate under inert conditions. The novel growth system exploits the in situ formation of discrete Cu3Ge catalyst seeds from 1 nm thermally evaporated Cu layers. As the nanowires were grown from a suitable current collector, the electrodes could be used directly without binders in lithium-ion half cells. Electrochemical testing showed remarkable capacity retention with 866 mAh/g achieved after 1900 charge/discharge cycles and a Coulombic efficiency of 99.7%. The nanowire-based anodes also showed high-rate stability with discharge capacities of 800 mAh/g when cycled at a rate of 10C.
- Published
- 2014
- Full Text
- View/download PDF
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