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Mingyuan
Ye
,
Ziqi
Zhao
,
Liying
Liu
,
Li
Shao
,
Li
Liu
,
Xiaorui
Hao
,
Jiaqi
Lv
,
Peng-Fei
Wang
,
Yu-Han
Zhang
,
Fa-Nian
Shi
,
Yuhan
Wu
Abstract: In this work, Cu1.04Mn0.96O2 nanosheets were synthesized via a simple hydrothermal method, and their electrochemical lithium storage properties and reaction mechanisms were investigated. The nanosheet structure effectively promotes electron transfer and shortens the transport path. Additionally, the partial substitution of Cu for Mn decreases the Jahn-Teller distortion of the MnO6 octahedron. Employing as an anode for Li-ion batteries, the specific capacity reached 610.91 mAh g−1 after 100 cycles at a current density of 100 mA g−1.
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Oct 2024
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: Solid-state electrolytes (SEs) hold the potential to overcome challenges that hinder the commercialization of lithium-sulfur batteries. However, their limited ionic conductivity makes lithium (Li) ion transport a critical bottleneck in accessing the superior capacity of sulfur. In this study, we investigate high-entropy Cl,Br-co-doped sulfide argyrodites as SEs in Li-sulfur (S) all-solid-state batteries (ASSBs).
exhibits an ionic conductivity of 6.9 mS
at room temperature with an activation energy of 0.28 eV, thanks to its high configurational entropy. The electrolyte with suitable cathodic stability and high ionic conductivity allows S composite cathodes to deliver an areal capacity over 6 mAh
when cycled with Li-In anodes. The reduced porosity of the SE separator and the formation of a passivating interphase with metallic Li enable Li-S ASSBs to cycle without short circuits, achieving an S utilization of over 75% at 0.1 C.
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Oct 2024
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[35312]
Abstract: The electro-chemo-mechanic phenomena that play a crucial role in the stability of halide solid electrolytes with Li metal at the interface are unknown. Moreover, in a halide SE, the central M atom is known to dictate its reactivity with Li metal. To understand this chemical composition-dependent reactivity of halide SE, we have taken three halide solid electrolytes, namely Li3InCl6, Li2ZrCl6, and Li3YCl6. Here, we use operando X-ray photoelectron spectroscopy during Li plating to understand the reaction kinetics leading to the interphase evolution and interphase composition. The interphase evolution in symmetric cells was further monitored by operando electrochemical impedance spectroscopy and operando pressure measurements, showing the complex intertwining of molar volume change, void formation, and interphase growth. The as-grown interphase was visualized by focused ion beam scanning electron microscopy. The chemical reactivity was confirmed by bond strength calculations using operando synchrotron X-ray diffraction. We confirm volume changes due to molar volume mismatch leading to different microstructures of interphases for the three-halide solid electrolytes, which are correlated to the impedance growth during electrochemistry by operando impedance measurements, showing molar volume change has a drastic effect on the reactivity.
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Oct 2024
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[33024]
Open Access
Abstract: Intrinsic self-healing chemistries based on dynamic bonds have been shown to solve many issues in advanced applications, not the least batteries. Herein, we investigate the interactions within a polymer system containing dynamic covalent bonds as cross-linkers and their role when they are used as binders in silicon electrodes. We introduce 1,4-benzenediboronic acid (BDBA) as a cross-linking agent forming boronic ester groups and sodium tetraborate (borax) forming borate ester bonds with poly(vinyl alcohol) (PVA). Silicon electrodes with the cross-linked binders show improved electrochemical performance with a capacity of 1500 mA h g–1 after 200 cycles compared to PVA alone featuring 1000 mA h g–1. In contrast, another hydroxyl-containing polymer, carboxymethyl cellulose, able to form the same cross-linking functionalities, showed poorer performance with the addition of BDBA. The choice of polymer and cross-linker not only impacted the cell performance but also the electrode fabrication and morphology. The presence of cross-linkers decreased the electrode cracking of the pristine and cycled electrodes while having little effect on the solid electrolyte interphase composition. Hence, the properties of the polymeric binder system as a whole and the electrode manufacturing process have a significant impact on the cell performance. Solid-state NMR is shown to be a powerful technique to investigate the interaction between the different components and to confirm the formation of boronic ester bonds via the hydroxyl groups of PVA. Furthermore, the presence of silicon particles changes the chemical environment of the boron in BDBA favoring the formation of borate species, which are not present with PVA only, indicating interactions between BDBA and the silicon particles. Hence, PVA in combination with the boron-based cross-linkers, BDBA and borax, provide higher capacity and cycling stability than PVA alone, showing a promising approach to overcome the challenges of silicon anodes using binders with dynamic covalent bonds.
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Oct 2024
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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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B18-Core EXAFS
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Diamond Proposal Number(s):
[11874]
Open Access
Abstract: Li-rich garnet solid electrolytes are promising candidates for all-solid-state batteries, permitting increased energy densities, compatibility with Li-metal anodes and improved safety by replacing flammable organic-based liquid electrolytes. Li-stuffed garnets typically require aliovalent doping to stabilise the highly ionic conductive Ia3 @#x0305;d cubic phase. The role of dopants and their location within the garnet framework can greatly affect the conduction properties of these garnets, yet their impact on structure and resulting ion transport are not fully understood. Here, we evaluate the effect of aliovalent doping with Al3+, Ga3+ and Zn2+ in the Li6BaLa2Ta2O12 (LBLTO) garnet material. A combination of PXRD and XAS reveal a linear cell parameter contraction with increasing doping noted and preference of the 24d Li+ sites for Al3+ and Zn2+ dopants, with Ga3+ occupying both the 24d and 48g Li+ sites. Macroscopic ionic conductivity analyses by EIS demonstrate an enhancement of the transport properties where addition of small amounts of Al3+ decrease the activation energy to Li+ diffusion to 0.35(4) eV. A detrimental effect on ionic conductivities is observed when introducing the dopants onto Li+ pathways and upon decreasing Li+ concentration. Insights into this behaviour are gleaned from microscopic diffusion studies by muon spin relaxation (µ+SR) spectroscopy, which reveal a low activation energy barrier for Li+ diffusion of 0.16(1) eV and a diffusion coefficient comparable to those of the Li7La3Zr2O12 (LLZO) benchmark garnet materials.
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Oct 2024
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B18-Core EXAFS
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Ajay Piriya
Vijaya Kumar Saroja
,
Yupei
Han
,
Charlie A. F.
Nason
,
Gopinathan
Sankar
,
Pan
He
,
Yi
Lu
,
Henry R.
Tinker
,
Andrew
Stewart
,
Veronica
Celorrio
,
Min
Zhou
,
Jiayan
Luo
,
Yang
Xu
Diamond Proposal Number(s):
[30102]
Open Access
Abstract: MoS2 is regarded as one of the most promising potassium-ion battery (PIB) anodes. Despite the great progress to enhance its electrochemical performance, understanding of the electrochemical mechanism to store K-ions in MoS2 remains unclear. This work reports that the K storage process in MoS2 follows a complex reaction pathway involving the conversion reactions of Mo and S, showing both cationic redox activity of Mo and anionic redox activity of S. The presence of dual redox activity, characterized in-depth through synchrotron X-ray absorption, X-ray photoelectron, Raman, and UV–vis spectroscopies, reveals that the irreversible Mo oxidation during the depotassiation process directs the reaction pathway toward S oxidation, which leads to the occurrence of K–S electrochemistry in the (de)potassiation process. Moreover, the dual reaction pathway can be adjusted by controlling the discharge depth at different cycling stages of MoS2, realizing a long-term stable cycle life of MoS2 as a PIB anode.
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Oct 2024
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I10-Beamline for Advanced Dichroism - scattering
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Lijin
An
,
Ruomu
Zhang
,
Prvanin N.
Didwal
,
Michael W.
Fraser
,
Leanne A. H.
Jones
,
Conor M. E.
Phelan
,
Namrata
Ramesh
,
Grant
Harris
,
Robert S.
Weatherup
,
Jack E. N.
Swallow
,
Peixi
Cong
,
Andrey
Poletayev
,
Erik
Bjorklund
,
Christophe J.
Sahle
,
Pilar
Ferrer
,
David C.
Grinter
,
Peter
Bencok
,
Shusaku
Hayama
,
Saiful
Islam
,
Robert
House
,
Peter D.
Nellist
,
Robert J.
Green
,
Rebecca J.
Nicholls
Diamond Proposal Number(s):
[33283, 33062, 32010]
Open Access
Abstract: Ni-rich layered oxide cathodes can deliver higher energy density batteries, but uncertainties remain over their charge compensation mechanisms and the degradation processes that limit cycle life. Trapped molecular O2 has been identified within LiNiO2 at high states of charge, as seen for Li-rich cathodes where excess capacity is associated with reversible O-redox. Here we show that bulk redox in LiNiO2 occurs by Ni-O rehybridization, lowering the electron density on O sites, but importantly without the involvement of molecular O2. Instead, trapped O2 is related to degradation at surfaces in contact with the electrolyte, and is accompanied by Ni reduction. O2 is removed on discharge, but excess Ni2+ persists forming a reduced surface layer, associated with impeded Li transport. This implicates the instability of delithiated LiNiO2 in contact with the electrolyte in surface degradation through O2 formation and Ni reduction, highlighting the importance of surface stabilisation strategies in suppressing LNO degradation.
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Sep 2024
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B18-Core EXAFS
I10-Beamline for Advanced Dichroism - scattering
I11-High Resolution Powder Diffraction
|
Diamond Proposal Number(s):
[34243]
Open Access
Abstract: The increased capacity offered by oxygen-redox active cathode materials for rechargeable lithium- and sodium-ion batteries (LIBs and NIBs, respectively) offers a pathway to the next generation of high-gravimetric-capacity cathodes for use in devices, transportation and on the grid. Many of these materials, however, are plagued with voltage fade, voltage hysteresis and O2 loss, the origins of which can be traced back to changes in their electronic and chemical structures on cycling. Developing a detailed understanding of these changes is critical to mitigating these cathodes’ poor performance. In this work, we present an analysis of the redox mechanism of P2–Na0.67[Mg0.28Mn0.72]O2, a layered NIB cathode whose high capacity has previously been attributed to trapped O2 molecules. We examine a variety of charge compensation scenarios, calculate their corresponding densities of states and spectroscopic properties, and systematically compare the results to experimental data: 25Mg and 17O nuclear magnetic resonance (NMR) spectroscopy, operando X-band and ex situ high-frequency electron paramagnetic resonance (EPR), ex situ magnetometry, and O and Mn K-edge X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Near Edge Spectroscopy (XANES). Via a process of elimination, we suggest that the mechanism for O redox in this material is dominated by a process that involves the formation of strongly antiferromagnetic, delocalized Mn–O states which form after Mg2+ migration at high voltages. Our results primarily rely on noninvasive techniques that are vital to understanding the electronic structure of metastable cycled cathode samples.
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Sep 2024
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[30357]
Open Access
Abstract: 1,1,1-trifluoroethyl methyl carbonate (FEMC) is a popular non-flammable solvent for lithium-ion battery electrolytes, although its high irreversible capacity means it can only be used with film-forming additives like fluoroethylene carbonate (FEC). This work studies the origin of the high irreversible capacity of FEMC-containing cells. Scanning electron microscopy and Raman spectroscopy of graphite anodes after charging and discharging in an FEMC electrolyte show evidence of significant physical and chemical graphite degradation, likely caused by solvent co-intercalation, which is probably responsible for a large portion of the capacity loss. X-ray photoelectron spectroscopy analysis of the anodes shows very low graphite signals, a sign of graphite degradation, formation of a thick solid electrolyte interphase (SEI), or both. When a small amount of FEC is added to FEMC, co-intercalation does not occur. FEC reduction occurs at a higher potential versus Li/Li+ than FEMC co-intercalation. It also forms a significantly different and thinner SEI containing more carbon, less fluorine, and no apparent FEMC decomposition products.
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Sep 2024
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