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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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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[26551]
Open Access
Abstract: For sodium-ion batteries, two pressing issues concerning electrolytes are flammability and compatibility with hard carbon anode materials. Non-flammable electrolytes that are sufficiently stable against hard carbon have—to the authors’ knowledge—previously only been obtained by either the use of high salt concentrations or additives. Herein, the authors present a simple, fluorine-free, and flame-retardant electrolyte which is compatible with hard carbon: 0.38 m sodium bis(oxalato)borate (NaBOB) in triethyl phosphate (TEP). A variety of techniques are employed to characterize the physical properties of the electrolyte, and to evaluate the electrochemical performance in full-cell sodium-ion batteries. The results reveal that the conductivity is sufficient for battery operation, no significant self-discharge occurs, and a satisfactory passivation is enabled by the electrolyte. In fact, a mean discharge capacity of 107 ± 4 mAh g−1 is achieved at the 1005th cycle, using Prussian white cathodes and hard carbon anodes. Hence, the studied electrolyte is a promising candidate for use in sodium-ion batteries.
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Oct 2021
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I09-Surface and Interface Structural Analysis
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Andrew J.
Naylor
,
Eszter
Makkos
,
Julia
Maibach
,
Niccolo
Guerrini
,
Adam
Sobkowiak
,
Erik
Bjorklund
,
Juan G.
Lozano
,
Ashok
Sreekumar Menon
,
Reza
Younesi
,
Matthew R.
Roberts
,
Kristina
Edström
,
M. Saiful
Islam
,
Peter G.
Bruce
Diamond Proposal Number(s):
[14733, 16629]
Open Access
Abstract: Lithium-rich materials, such as Li1.2Ni0.2Mn0.6O2, exhibit capacities not limited by transition metal redox, through the reversible oxidation of oxide anions. Here we offer detailed insight into the degree of oxygen redox as a function of depth within the material as it is charged and cycled. Energy-tuned photoelectron spectroscopy is used as a powerful, yet highly sensitive technique to probe electronic states of oxygen and transition metals from the top few nanometers at the near-surface through to the bulk of the particles. Two discrete oxygen species are identified, On- and O2-, where n<2, confirming our previous model that oxidation generates localised hole states on O upon charging. This is in contrast to the oxygen redox inactive high voltage spinel LiNi0.5Mn1.5O4, for which no On- species is detected. The depth profile results demonstrate a concentration gradient exists for On- from the surface through to the bulk, indicating a preferential surface oxidation of the layered oxide particles. This is highly consistent with the already well-established core-shell model for such materials. Ab initio calculations reaffirm the electronic structure differences observed experimentally between the surface and bulk, while modelling of delithiated structures shows good agreement between experimental and calculated binding energies for On-.
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Sep 2019
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I11-High Resolution Powder Diffraction
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Eun Jeong
Kim
,
Philip A.
Maughan
,
Euan N.
Bassey
,
Raphaële J.
Clément
,
Le Anh
Ma
,
Laurent C.
Duda
,
Divya
Sehrawat
,
Reza
Younesi
,
Neeraj
Sharma
,
Clare P.
Grey
,
Robert
Armstrong
Diamond Proposal Number(s):
[26699]
Open Access
Abstract: Activation of oxygen redox represents a promising strategy to enhance the energy density of positive electrode materials in both lithium and sodium-ion batteries. However, the large voltage hysteresis associated with oxidation of oxygen anions during the first charge represents a significant challenge. Here, P3-type Na0.67Li0.2Mn0.8O2 is reinvestigated and a ribbon superlattice is identified for the first time in P3-type materials. The ribbon superstructure is maintained over cycling with very minor unit cell volume changes in the bulk while Li ions migrate reversibly between the transition metal and Na layers at the atomic scale. In addition, a range of spectroscopic techniques reveal that a strongly hybridized Mn 3d–O 2p favors ligand-to-metal charge transfer, also described as a reductive coupling mechanism, to stabilize reversible oxygen redox. By preparing materials under three different synthetic conditions, the degree of ordering between Li and Mn is varied. The sample with the maximum cation ordering delivers the largest capacity regardless of the voltage windows applied. These findings highlight the importance of cationic ordering in the transition metal layers, which can be tuned by synthetic control to enhance anionic redox and hence energy density in rechargeable batteries.
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Dec 2021
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[18974]
Abstract: Potassium-ion (K-ion) batteries potentially offer numerous advantages over conventional lithium-ion batteries as a result of the high natural abundance of potassium and its lower positive charge density, compared with lithium. This introduces the possibility of using K-ion in fast charging applications, in which cost effectiveness is also a major factor. Unlike for sodium-ion batteries, graphite can be used as an anode in K-ion cells, for which an extensive supply chain, electrode manufacturing infrastructure, and knowledge already exists. However, the performance of graphite anodes in K-ion cells does not meet expectations, with rapid capacity fading and poor first cycle irreversible capacities often reported. Here we investigate the formation and composition of the solid electrolyte interphase (SEI) as well as K+ insertion in graphite anodes in K-ion batteries. Through the use of energy-tuned synchrotron-based X-ray photoelectron spectroscopy, we make a detailed analysis at three probing depths up to ~50 nm of graphite anodes cycled to various potentials on the first discharge-charge cycle. Extensive SEI formation from a KPF6/DEC:EC electrolyte system is found to occur at low potentials during the insertion of potassium into graphite. During the subsequent removal of potassium from the structure, the thick SEI is partially stripped from the electrode, demonstrating that the SEI layer is unstable and contributes to a significant proportion of the capacity on both discharge and charge. With this in mind, further work is required to develop an electrolyte system with stable SEI layer formation on graphite in order to advance K-ion battery technology.
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Nov 2019
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[36213]
Open Access
Abstract: Five different electrolyte salts, namely NaBF4, NaClO4, NaDFOB, NaFSI and NaPF6, were evaluated in non-flammable triethyl phosphate (TEP) based electrolyte solutions in sodium-ion full-cells using high-mass loading Prussian white and hard carbon electrodes. Their impact on the viscosity, ionic conductivity and solvation structure was analyzed, revealing that NaFSI-based electrolytes exhibited a stronger interaction with TEP and less ion-pairing than the other salts, resulting in the highest ionic conductivity at a concentration of 0.8 m (mol/kg). Galvanostatic cycling experiments showed that none of the electrolyte salts dissolved in TEP forms an efficient passivation layer. However, adding 1 wt.% vinylene carbonate (VC) significantly improved cycling performance for the cells with NaBF4, NaDFOB or NaFSI, but not with NaClO4 or NaPF6. Additionally, NaFSI in TEP with 1 wt.% VC electrolyte solution showed minimal gas evolution during the formation cycling (< 8 mbar). In a 1 Ah multilayer pouch cell, 0.8 m NaFSI in TEP with 1 wt.% VC showed promising results with 88% capacity retention after 200 cycles. X-ray photoelectron spectroscopy analysis revealed that the addition of VC results in the formation of a thin SEI and minimized TEP decomposition on hard carbon, especially for 0.8 m NaFSI TEP with 1 wt.% VC.
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Oct 2024
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I11-High Resolution Powder Diffraction
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Abstract: LiBH4–Ca(BH4)2 composites were prepared by ball milling. Their crystal structures and phase composition were investigated using synchrotron X-ray diffraction and Rietveld refinement, and their ionic conductivity was measured using impedance spectroscopy. The materials were found to form a physical mixture. The composites were composed of α-Ca(BH4)2, γ-Ca(BH4)2 and orthorhombic LiBH4, and the relative phase quantities of the Ca(BH4)2 polymorphs varied significantly with LiBH4 content. The formation of small amounts of orthorhombic CaH2 and cubic CaH2 in a CaF2-like structure was observed upon heat treatment. Concurrent formation of elemental boron may also occur. The ionic conductivity of the composites was measured using impedance spectroscopy, and was found to be lower than that of ball milled LiBH4. Electronic band structure calculations indicate that cubic CaH2 with hydrogen defects is electronically conducting. Its formation along with the possible precipitation of boron therefore has an effect on the measured conductivity of the LiBH4–Ca(BH4)2 composites and may increase the risk of an internal short-circuit in the cells.
X-ray diffraction
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Mar 2014
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B18-Core EXAFS
|
Diamond Proposal Number(s):
[14239]
Abstract: Increasing dependence on rechargeable batteries for energy storage calls for the improvement of energy density of batteries. Toward this goal, introduction of positive electrode materials with high voltage and/or high capacity is in high demand. The use of oxygen chemistry in lithium and sodium layered oxides has been of interest to achieve high capacity. Nevertheless, a complete understanding of oxygen-based redox processes remains elusive especially in sodium ion batteries. Herein, a novel P3-type Na0.67Ni0.2Mn0.8O2, synthesized at low temperature, exhibits oxygen redox activity in high potentials. Characterization using a range of spectroscopic techniques reveals the anionic redox activity is stabilized by the reduction of Ni, because of the strong Ni 3d–O 2p hybridization states created during charge. This observation suggests that different route of oxygen redox processes occur in P3 structure materials, which can lead to the exploration of oxygen redox chemistry for further development in rechargeable batteries.
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Jan 2020
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[17901]
Abstract: Sodium ion batteries based on Prussian blue analogues (PBAs) are ideal for large scale energy storage applications due to the ability to meet the huge volumes and low costs required. For Na2-xFe[Fe(CN)6]1-y.zH2O realising its commercial potential means fine control of the concentration of sodium, Fe(CN)6 vacancies and water content. To date, there is a huge variation in the literature of composition leading to variable electrochemical performance. In this work, we break down the synthesis of Prussian blue analogous (PBAs) into three steps for controlling the sodium, vacancy and water content via an inexpen-sive, scalable synthesis method. We produce rhombohedral Prussian white Na1.88(5)Fe[Fe(CN)6].0.18(9)H2O with an initial capacity of 158 mAhg-1 retaining 90% capacity after 50 cycles. Subsequent characterisation revealed that the increased polarisation on the 3 V plateau is coincident with a phase transition and reduced utilisation of the high spin Fe(III)/Fe(II) redox couple. This reveals a clear target for subsequent improvements of the material to boost long term cycling stability. These results will be of great interest for the myriad of applications PBAs are suited towards such as catalysis, magnetism, electrochromics and gas sorption.
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Aug 2019
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[23159]
Open Access
Abstract: With emerging interest in sodium‐ion battery (SIB) technology due to its cost effectiveness and high earth abundance of sodium, the search for an optimised SIB system becomes more and more crucial. It is well known that the formation of a stable solid electrolyte interphase (SEI) at the anode in Na‐based systems is a challenge due to the higher solubility of the SEI components compared to in the lithium‐ion battery case. Our knowledge about the formation and dissolution of the SEI in SIBs is so far based on limited experimental data. The aim of the present research is therefore to enhance the understanding of the behaviour of the SEI in SIBs and shed more light on the influence of the electrolyte chemistry on the dissolution of the SEI. By conducting electrochemical tests including extended open circuit pauses, we study the SEI dissolution in different time domains. With this, it is possible to determine the extent of self‐discharge due to SEI dissolution during a specific time. Instead of using a conventional separator, β‐alumina is employed as a Na‐conductive membrane to avoid crosstalk between the working electrode and Na‐metal counter electrode. The SEI composition is monitored using synchrotron‐based soft X‐ray photoelectron spectroscopy (SOXPES). The electrochemical and XPS results show that the SEIs formed in the studied electrolyte systems have different stabilities. The relative capacity loss after a 50‐hour pause in the tested electrolyte systems can be up to 30%. Among three carbonate‐based solvent systems, NaPF 6 in ethylene carbonate: diethyl carbonate exhibits the most stable SEI. The addition of electrolyte additives improves the SEI stability in PC. The electrolyte is saturated with typical SEI species, NaF and Na 2 CO 3 , in order to oppose the dissolution of the SEI. Furthermore, the solubilities of the latter additives in the different solvent systems are determined by inductively coupled plasma – optical emission spectrometry.
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Nov 2020
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