B18-Core EXAFS
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Abstract: The recent report of P2–Na2/3Mg0.28Mn0.72O2 (P2-NMM) demonstrated the possibility of utilizing the oxygen redox couple in a layered oxide cathode without the need for alkali ions or vacancies in the transition metal layer. In this work, we report the synthesis of a new P2-type compound, Na2/3Mg1/4Mn7/12Co1/6O2 (P2-NMMC), which exhibits reversible specific capacities as high as 173 mAh g−1 and an improvement of the first cycle voltage hysteresis over P2-NMM. The material was characterised using a combination of ex-situ and operando techniques including X-ray diffraction (XRD), differential electrochemical mass spectrometry (DEMS) and X-ray spectroscopy (XAS) to identify potential sources for this improvement.
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Sep 2021
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Nuria
Tapia-Ruiz
,
A. Robert
Armstrong
,
Hande
Alptekin
,
Marco A.
Amores
,
Heather
Au
,
Jerry
Barker
,
Rebecca
Boston
,
William R
Brant
,
Jake M.
Brittain
,
Yue
Chen
,
Manish
Chhowalla
,
Yong-Seok
Choi
,
Sara I. R.
Costa
,
Maria
Crespo Ribadeneyra
,
Serena A
Cussen
,
Edmund J.
Cussen
,
William I. F.
David
,
Aamod V
Desai
,
Stewart A. M.
Dickson
,
Emmanuel I.
Eweka
,
Juan D.
Forero-Saboya
,
Clare
Grey
,
John M.
Griffin
,
Peter
Gross
,
Xiao
Hua
,
John T. S.
Irvine
,
Patrik
Johansson
,
Martin O.
Jones
,
Martin
Karlsmo
,
Emma
Kendrick
,
Eunjeong
Kim
,
Oleg V
Kolosov
,
Zhuangnan
Li
,
Stijn F L
Mertens
,
Ronnie
Mogensen
,
Laure
Monconduit
,
Russell E
Morris
,
Andrew J.
Naylor
,
Shahin
Nikman
,
Christopher A
O’keefe
,
Darren M. C.
Ould
,
Robert G.
Palgrave
,
Philippe
Poizot
,
Alexandre
Ponrouch
,
Stéven
Renault
,
Emily M.
Reynolds
,
Ashish
Rudola
,
Ruth
Sayers
,
David O.
Scanlon
,
S.
Sen
,
Valerie R.
Seymour
,
Begoña
Silván
,
Moulay Tahar
Sougrati
,
Lorenzo
Stievano
,
Grant S.
Stone
,
Chris I.
Thomas
,
Maria-Magdalena
Titirici
,
Jincheng
Tong
,
Thomas J.
Wood
,
Dominic S
Wright
,
Reza
Younesi
Open Access
Abstract: Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.
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Jul 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[14926]
Open Access
Abstract: Li–N–H materials, particularly lithium amide and lithium imide, have been explored for use in a variety of energy storage applications in recent years. Compositional variation within the parent lithium imide, anti-fluorite crystal structure has been related to both its facile storage of hydrogen and impressive catalytic performance for the decomposition of ammonia. Here, we explore the controlled solid-state synthesis of Li–N–H solid-solution anti-fluorite structures ranging from amide-dominated (Li4/3(NH2)2/3(NH)1/3 or Li1.333NH1.667) through lithium imide to majority incorporation of lithium nitride–hydride (Li3.167(NH)0.416N0.584H0.584 or Li3.167NH). Formation of these solid solutions is demonstrated to cause significant changes to the thermal stability and ammonia reactivity of the samples, highlighting the potential use of compositional variation to control the properties of the material in gas storage and catalytic applications.
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Jul 2021
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I09-Surface and Interface Structural Analysis
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Nicholas H.
Bashian
,
Mateusz
Zuba
,
Ahamed
Irshad
,
Shona M.
Becwar
,
Julija
Vinckeviciute
,
Warda
Rahim
,
Kent J.
Griffith
,
Eric T.
Mcclure
,
Joseph K.
Papp
,
Bryan D.
Mccloskey
,
David O.
Scanlon
,
Bradley F.
Chmelka
,
Anton
Van Der Ven
,
Sri R.
Narayan
,
Louis F. J.
Piper
,
Brent
Melot
Diamond Proposal Number(s):
[22250]
Abstract: We report on the electrochemical fluorination of the A-site vacant perovskite ReO3 using high-temperature solid-state cells as well as room-temperature liquid electrolytes. Using galvanostatic oxidation and electrochemical impedance spectroscopy, we find that ReO3 can be oxidized by approximately 0.5 equiv of electrons when in contact with fluoride-rich electrolytes. Results from our density functional theory calculations clearly rule out the most intuitive mechanism for charge compensation, whereby F-ions would simply insert onto the A-site of the perovskite structure. Operando X-ray diffraction, neutron total scattering measurements, X-ray spectroscopy, and solid-state 19F NMR with magic-angle spinning were, therefore, used to explore the mechanism by which fluoride ions react with the ReO3 electrode during oxidation. Taken together, our results indicate that a complex structural transformation occurs following fluorination to stabilize the resulting material. While we find that this process of fluorinating ReO3 appears to be only partially reversible, this work demonstrates a practical electrolyte and cell design that can be used to evaluate the mobility of small anions like fluoride that is robust at room temperature and opens new opportunities for exploring the electrochemical fluorination of many new materials.
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Jul 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[12746]
Abstract: Carbon-supported Pt-based nanoparticles are important electrocatalysts for energy conversion reactions such as the oxygen reduction reaction (ORR). Although this reaction has been extensively studied, the influence of factors such as the particle size and interparticle distance of the nanoparticle-based or nanosized electrocatalysts on the ORR activity and durability are not yet fully understood and often intertwined. This lack of understanding is mostly based on the limitation in the synthetic approaches of the electrocatalysts, which usually do not allow an independent variation of the particle size and interparticle distance. In the presented work, we succeeded to disentangle both factors using a “colloidal toolbox” approach and have demonstrated an effect of the interparticle distance on the electronic properties of the nanoparticle via operando electrochemical X-ray absorption spectroscopy (XAS).
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Jun 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[15151]
Abstract: Pt-Sn bimetallic catalysts, especially Pt-Sn alloys, are considered highly CO-tolerant and are thus candidates for reformate derived hydrogen oxidation and for direct oxidation of fuel cell molecules. However, it remains unclear if this CO-tolerance originates from Sn in the Pt-Sn alloy or whether SnO 2 , present as a separate phase, also contributes. In this work, a carbon-supported Pt-SnO 2 was carefully synthesized to avoid the formation of Pt-Sn alloy phases. The resulting structure was analysed by scanning transmission electron microscopy (STEM) and detailed X-ray absorption spectroscopy (XAS). CO oxidation voltammograms of the Pt-SnO 2 /C and other SnO 2 -modified Pt surfaces unambiguously suggest that a bifunctional mechanism is indeed operative at such Pt-SnO 2 catalysts for stable CO oxidation at low overpotentials. The results from these studies suggest that the bifunctional mechanism can be attributed to the co-catalysis role of SnO 2 , in which the surface hydroxide of SnO 2 (Sn-OH) reacts with CO adsorbed on Pt surface (Pt-CO ads ) and regenerates via a Sn II /Sn IV reversible redox couple (-0.2–0.3 V vs. reversible hydrogen electrode).
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Jun 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[25651]
Open Access
Abstract: In this paper, we demonstrate a novel synthetic route to assemble reduced graphene oxide (rGO) uniformly coated on BiSI composite and investigate its potential as the active electrode material for supercapacitors. In this strategy, graphene oxide (GO) was not a simple physical mixture with the BiSI material but bismuth cations were uniformly anchored on the surface of GO by chemical bonding during material growth and the size of GO can determine the final size of rGO coated BiSI composite. The galvanostatic charge–discharge measurement results show that the BiSI–rGO electrode has a maximum specific capacity of 234 C g−1 at the current density of 1 A g−1 and excellent capacity retention of 92.4% after 2000 cycles. In situ XANES and EXAFS were employed to study the electrochemical oxidation and reduction processes of the bismuth-based material with rGO coating and investigate the origins of the structural stabilities. The results show that our novel rGO coating route can not only significantly increase the capacity but also improve cycling stability.
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Jun 2021
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B18-Core EXAFS
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Jamie W.
Gittins
,
Chloe J.
Balhatchet
,
Yuan
Chen
,
Cheng
Liu
,
David G.
Madden
,
Sylvia
Britto
,
Matthias J.
Golomb
,
Aron
Walsh
,
David
Fairen-Jimenez
,
Sian E.
Dutton
,
Alexander C.
Forse
Diamond Proposal Number(s):
[14239]
Open Access
Abstract: Two-dimensional electrically conductive metal–organic frameworks (MOFs) have emerged as promising model electrodes for use in electric double-layer capacitors (EDLCs). However, a number of fundamental questions about the behaviour of this class of materials in EDLCs remain unanswered, including the effect of the identity of the metal node and organic linker molecule on capacitive performance, and the limitations of current conductive MOFs in these devices relative to traditional activated carbon electrode materials. Herein, we address both these questions via a detailed study of the capacitive performance of the framework Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with an acetonitrile-based electrolyte, finding a specific capacitance of 110–114 F g−1 at current densities of 0.04–0.05 A g−1 and a modest rate capability. By directly comparing its performance with the previously reported analogue, Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene), we illustrate that capacitive performance is largely independent of the identity of the metal node and organic linker molecule in these nearly isostructural MOFs. Importantly, this result suggests that EDLC performance in general is uniquely defined by the 3D structure of the electrodes and the electrolyte, a significant finding not demonstrated using traditional electrode materials. Finally, we probe the limitations of Cu3(HHTP)2 in EDLCs, finding a limited stable double-layer voltage window of 1 V and only a modest capacitance retention of 81% over 30 000 cycles, both significantly lower than state-of-the-art porous carbons. These important insights will aid the design of future conductive MOFs with greater EDLC performances.
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Jun 2021
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B18-Core EXAFS
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Diamond Proposal Number(s):
[24303]
Open Access
Abstract: P2-layered sodium-ion battery (NIB) cathodes are a promising class of Na-ion electrode materials with high Na+ mobility and relatively high capacities. In this work, we report the structural changes that take place in P2–Na0.67[Mg0.28Mn0.72]O2. Using ex situ X-ray diffraction, Mn K-edge extended X-ray absorption fine structure, and 23Na NMR spectroscopy, we identify the bulk phase changes along the first electrochemical charge–discharge cycle—including the formation of a high-voltage “Z phase”, an intergrowth of the OP4 and O2 phases. Our ab initio transition state searches reveal that reversible Mg2+ migration in the Z phase is both kinetically and thermodynamically favorable at high voltages. We propose that Mg2+ migration is a significant contributor to the observed voltage hysteresis in Na0.67[Mg0.28Mn0.72]O2 and identify qualitative changes in the Na+ ion mobility.
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Jun 2021
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Open Access
Abstract: Lithium ion battery technology is the state-of-the-art rechargeable energy storage technology for electric vehicles, stationary energy storage and personal electronics. However, a wide variety of degradation effects still contribute to performance limitations. The metallic copper and aluminium current collectors in a lithium ion battery can be subject to dissolution or other reactions with the electrolytes. Corrosion of these metal foils is significantly detrimental to the overall performance of a lithium ion battery, however the mechanisms of this degradation are poorly understood. This review summarises the key effects contributing to metal current collector degradation in lithium ion batteries as well as introduces relevant corrosion and lithium ion battery principles. By developing the understanding of these complex chemistries, lithium ion battery degradation can be mitigated, enabling safer operation and longer lifetimes.
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Jun 2021
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