I09-Surface and Interface Structural Analysis
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Galo J.
Paez Fajardo
,
Daniela E.
Dogaru
,
Hrishit
Banerjee
,
Muhammad
Ans
,
Matthew J. W.
Ogley
,
Veronika
Majherova
,
Gerard
Bree
,
Innes
Mcclelland
,
Shohei
Hayashida
,
Pascal
Puphal
,
Masahiko
Isobe
,
Bernhard
Keimer
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Dave C.
Grinter
,
Pilar
Ferrer
,
Serena A.
Cussen
,
Matthias
Hepting
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33459, 35075, 36917, 30201]
Open Access
Abstract: Describing lithium-based battery positive electrodes based on different transition metal or oxygen-redox regimes can cause confusion in understanding metal–ligand hybridization, oxygen dimerization and degradation processes. Therefore, it is urgent to investigate the electronic structure of these materials and identify the role each cation and anion has in charge compensation at the subnanoscale. Here, using X-ray resonance photoemission spectroscopy, single-impurity Anderson models, spectral simulations and theoretical calculations, we examine redox mechanisms in positive electrodes during lithium-based battery operation. This approach reconciles the redox description of two positive electrode active materials—LiMn0.6Fe0.4PO4 and LiNiO2—in terms of varying degrees of charge transfer using the Zaanen–Sawatzky–Allen framework. In LiMn0.6Fe0.4PO4, the lack of strong hybridization indicates that the capacity results from the depopulation of metal 3d states, that is, conventional metal redox. However, in cells with LiNiO2-based positive electrodes, negative charge transfer dominates, and redox occurs through the formation and elimination of ligand-hole states. These results clarify the role of oxygen in Ni-rich systems and provide a framework to explain how the charge/discharge capacities are linked to oxygen-dominated states in highly covalent systems, without the need to consider oxygen dimerization.
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Jun 2026
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I11-High Resolution Powder Diffraction
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Heng
Wang
,
Rui
Wang
,
Christopher A.
O'Keefe
,
Erik
Bjorklund
,
Daniela
Proprentner
,
Joe C.
Stallard
,
Hwee Jien
Tan
,
Wesley M.
Dose
,
Louis F. J.
Piper
,
Robert S.
Weatherup
,
Angkur J. D.
Shaikeea
,
Clare P.
Grey
,
Michael
De Volder
Diamond Proposal Number(s):
[34243]
Open Access
Abstract: While electrochemical degradation mechanisms in lithium-ion batteries are well studied, the influence of mechanical factors remains poorly understood. Here we introduce a high-precision stack-pressure control and dilatometry tool to apply a uniform and constant stack pressure on electrodes independent of electrode swelling. By increasing stack pressure fourfold over typical initial values, we double the lifetime of graphite ‖ LiNi0.8Mn0.1Co0.1O2 cells, an industrially relevant battery chemistry, without altering active materials or electrolytes. This suggests that many lithium-ion batteries operate under sub-optimal stack-pressure conditions, leading to curtailed lifetimes. We demonstrate that different degradation mechanisms emerge outside the optimal pressure window: low stack pressure accelerates cathode cracking, whereas high pressure promotes lithium plating. Our findings highlight coupled mechanical–electrochemical degradation mechanisms and identify stack-pressure optimization as a practical solution for increasing cycling stability.
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Jun 2026
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Gaurav C.
Pandey
,
Ashok S.
Menon
,
Valeria
Calani San Miguel
,
José J.
Arroyo‐gómez
,
Harry
Gillions
,
Rebecca
Sellers
,
Matthew J. W.
Ogley
,
Eleni
Fiamegkou
,
Satish
Bolloju
,
Sahil
Tippireddy
,
Mirian
Garcia-Fernandez
,
Steven
Huband
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[38432]
Open Access
Abstract: The electrochemical performance of single-crystalline (SC) Ni-rich layered oxide cathodes is fundamentally limited by bulk Li+ diffusion within micrometre-sized particles. During high-voltage cycling—necessary for high-energy applications—intraparticle Li+ diffusion is further impeded by oxygen-loss-induced surface reconstruction from the layered phase to spinel/rock-salt structures. Therefore, to fully understand how bulk Li+ transport kinetics influences electrochemical degradation, it is necessary to establish the correlation between surface reconstruction and bulk delithiation during the anisotropic structural evolution (i.e., expansion of the layers followed by their contraction) of the cathode particles during long-term cycling. In this work, we accomplish this using multi-rate operando X-ray diffraction studies of SC Ni-rich layered oxide cathodes aged under different voltage windows in single-layer pouch full cells. We quantify how increased surface reconstruction leads to greater heterogeneity in bulk delithiation, thereby promoting phase separation and exacerbating electrochemical capacity fade. These results provide a direct mechanistic link between surface degradation and bulk delithiation in such cathodes and offer a framework for non-destructively probing kinetics-dependent degradation under practically relevant conditions to guide strategies for improved cycling stability.
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May 2026
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I09-Surface and Interface Structural Analysis
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Muhammad
Ans
,
Eleni
Fiamegkou
,
Ashok S.
Menon
,
Gaurav C.
Pandey
,
Gaolo J.
Paez Fajardo
,
Harry
Gillions
,
Paolo
Melgari
,
Calum
Clenahan
,
Satish
Bolloju
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Serena A.
Cussen
,
Beth I. J.
Johnston
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[38340]
Open Access
Abstract: Lithium nickel oxide (LNO) cathodes offer high capacity for high-energy-density applications but suffer rapid degradation above 4.2 V due to surface and bulk instabilities. Here, we apply an ultrathin aluminum oxide coating using powder atomic layer deposition to improve surface stability. Pouch cell testing shows that coated LNO delivers improved cycling behavior, retaining 91.2% capacity after 100 cycles at C/3. Operando X-ray diffraction reveals that after aging, coated LNO undergoes a less kinetically hindered delithiation, indicating that the surface coating further provides a surface-to-bulk stabilization effect. Postmortem surface sensitive spectroscopy confirms that the aluminum oxide layer (1) scavenges hydrofluoric acid and (2) suppresses surface reconstruction, reducing impedance growth and improving the surface integrity. Overall, the results demonstrate that ultrathin aluminum oxide coatings effectively mitigate interfacial degradation and enhance bulk electrochemical kinetics, providing an effective and scalable approach toward improving the long-term performance of ultra-Ni-rich cathodes.
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Mar 2026
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[38563]
Open Access
Abstract: The development of diverse battery chemistries demands advanced diagnostic techniques to study them. Neutron diffraction, which is sensitive to light elements and capable of distinguishing transition metals with similar electronic configurations, is well-suited to probe crystallographic transformations in battery materials and their degradation pathways. Yet its use has been limited by compromised data quality, low time resolution, and the absence of resource-efficient, reproducible, benchmarked electrochemical cells. Here, using the high-resolution cold-neutron diffractometer WISH, we demonstrate operando neutron diffraction studies of standard laboratory-scale single-layer pouch cells without build modifications, electrolyte deuteration, or isotope enrichment of the electrodes, under practical cycling conditions. This expands the battery diagnostic toolkit beyond X-rays and enables academic exploration of both established and emerging technologies, especially lithium–metal, anode-less, and lithium–sulfur batteries.
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Mar 2026
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I15-1-X-ray Pair Distribution Function (XPDF)
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Zixuan
Li
,
Rui
Qi
,
Yi
Yuan
,
Lechen
Yang
,
Lijiang
Song
,
Ashok S.
Menon
,
Louis F. J.
Piper
,
Didier
Wermeille
,
Paul
Thompson
,
Robert A.
House
,
Peter G.
Bruce
,
Alex W.
Robertson
Open Access
Abstract: Aqueous zinc-ion batteries (ZIBs) suffer from sustained capacity loss at the zinc metal anode due to side reactions with the electrolyte, even under idle conditions. The concept of an anode-free ZIB would address this degradation by eliminating the metal anode source. A key requirement for such systems is a cathode that contains zinc in its pristine state and supports initial charging. Here, we report the synthesis and characterization of cation-disordered rocksalt (DRX) ZnMnO2, a new cathode material suitable for anode-free ZIBs. ZnMnO2 meets the essential criteria for anode-free operation of natively containing Zn in the pristine state, enabling an initial charge, as well as offering high initial charge capacity (312.8 mAh g−1), and discharge voltage (1.36 V). We show that the dominant energy storage mechanism involves Mn dissolution and redeposition, with a smaller contribution arising from reversible Zn intercalation into a spinel phase that forms in situ during cycling. We further demonstrate the versatility of DRX cathodes by extending the concept to ZnFeO2. These findings establish DRX materials as a promising platform for the development of cathodes suitable for anode-free ZIBs.
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Oct 2025
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B18-Core EXAFS
I09-Surface and Interface Structural Analysis
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Muhammad
Ans
,
Gaurav C.
Pandey
,
Innes
Mcclelland
,
Naresh
Gollapally
,
Harry
Gillions
,
Beth I. J.
Johnston
,
Matthew J. W.
Ogley
,
James A.
Gott
,
Eleni
Fiamegkou
,
Veronica
Celorrio
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Serena A.
Cussen
,
Ashok S.
Menon
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[30104, 33553]
Open Access
Abstract: Single-crystalline LiNiO2 (SC-LNO), a high-energy-density Li-ion cathode material, suffers from poor long-term electrochemical performance when cycled above 4.2 V (vs Li+/Li). In this study, this degradation is evaluated using SC-LNO–graphite pouch cells electrochemically aged within a stressful voltage window (2.5–4.4 V) using a constant-current constant-voltage (CC-CV) protocol. Notable capacity fade is observed after one hundred cycles at C/3 rate, in addition to an increase in the overall electrochemical cell impedance. Operando X-ray diffraction data reveal that, despite no significant long-range bulk structural changes, (de-)lithiation of the aged SC-LNO becomes kinetically hindered after 100 cycles. Aging-induced changes in the short-range structure and charge compensation are evaluated through a multi-model quantitative analysis of the operando X-ray absorption spectroscopy data. While the electrochemical aging does not result in particle cracking, soft X-ray absorption spectroscopy data revealed the reconstruction of the cathode surface to a dense rock salt-like layer after long-term cycling, which acts as a kinetic trap for Li+ diffusion. Therefore, even under stressful conditions, it is the surface reconstruction that dominates the overall cathode degradation by reducing the Li+ mobility and leading to the capacity fade. Cathode surface engineering will therefore be key to improving the long-term electrochemical performance of SC-LNO cathodes.
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May 2025
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[25166, 14239]
Open Access
Abstract: The high natural abundance and low toxicity of iron oxides provide a strong motivation to develop iron-based lithium-ion battery cathode materials. T-LiFeO2 adopts a cation-ordered wurtzite structure consisting of apex-linked LiO4 and FeO4 tetrahedra. Chemical or electrochemical lithium extraction rapidly converts T-LiFeO2 to the spinel LiFe5O8 and leads to poor energy storage performance. We have investigated the role of Al and Ga substitution on the stability of T-LiFeO2. Partial substitution of Fe by Al leads to the formation of cation-disordered solid solutions. In contrast, neutron diffraction data reveal that the Ga-substituted phase LiFe0.5Ga0.5O2 adopts an Fe/Ga cation-ordered structure. Chemical delithiation of LiFe1–xMxO2 phases reveals that 25% Al or 50% Ga substitution stabilizes the T-LiFe1–xMxO2 phases with respect to spinel conversion. The delithiated phases show no evidence of cation migration or oxygen loss. However, Fe-XANES, O-XAS, and O-RIXS data indicate that lithium extraction does not proceed via simple oxidation of Fe3+ to Fe4+ but rather via an anion redox process involving the formation of localized “FeIV–O” centers. Electrochemical data indicate that the formation of FeIV–O centers is irreversible, and so these oxidized species accumulate with continued electrochemical cycling, leading to a rapid decline in energy storage capacity. The electrochemical behavior of LiFe0.5Al0.5O2 and LiFe0.5Ga0.5O2 is discussed in terms of their crystal chemistry to account for the differing electrochemical performance of the Al- and Ga-substituted materials.
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Apr 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I09-Surface and Interface Structural Analysis
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Nickil
Shah
,
Galo J.
Paez Fajardo
,
Hrishit
Banerjee
,
Gaurav C.
Pandey
,
Ashok S.
Menon
,
Muhammad
Ans
,
Veronika
Majherova
,
Gerard
Bree
,
Satish
Bolloju
,
David .
Grinter
,
Pilar
Ferrer
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Melanie
Loveridge
,
Andrew J.
Morris
,
Clare P.
Grey
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[30201, 33459]
Open Access
Abstract: In Ni-rich layered oxide cathodes, cycling above the oxygen-loss threshold voltage (∼4.3 V vs Li+/Li) promotes structural transformations at the cathode surface. These transformations can result in various thermodynamically favorable rocksalt-like (RSL) structures (NiO, NiOx, and/or LiyNizO) that have different Li+ transport properties. Elucidating the precise phase type in the RSL can help determine design strategies to improve Li+ kinetics and identify design rules to suppress capacity fade in Ni-rich cathodes. This study utilizes surface-sensitive X-ray absorption spectroscopy in combination with first-principles simulations and distinguishes the layered oxide spectroscopic features from those of surface-reduced layers of pure NiO and LixNi1–xO. The transport of lithium ions through this oxygen-loss-induced surface-reconstructed layer is studied with operando X-ray diffraction in a pouch cell as a function of cycling aging and constant voltage protocols.
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Feb 2025
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B18-Core EXAFS
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Matthew J. W.
Ogley
,
Ashok S.
Menon
,
Gaurav C.
Pandey
,
Galo J.
Paez Fajardo
,
Beth J.
Johnston
,
Innes
Mcclelland
,
Veronika
Majherova
,
Steven
Huband
,
Debashis
Tripathy
,
Israel
Temprano
,
Stefano
Agrestini
,
Veronica
Celorrio
,
Gabriel E.
Perez
,
Samuel G.
Booth
,
Clare P.
Grey
,
Serena A.
Cussen
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33292, 33173]
Open Access
Abstract: This study refutes the commonly used ionic-bonding model that demarcates transition metal (TM) and oxygen redox using an archetypal Ni-rich layered oxide cathode, LiNi0.8Mn0.1Co0.1O2. Here, charge compensation during delithiation occurs without formal (ionic) Ni oxidation. Instead, oxygen-dominated states control the redox process, facilitated by strong TM-O hybridization, forming bulk-stable 3d8L and 3d8L2 electronic states, where L is a ligand hole. Bulk O–O dimers are observed with O K-edge resonant inelastic X-ray scattering but, critically, without the long-range TM migration or void formation observed in Li-rich layered oxides. Above 4.34 V vs. Li+/Li, the cathode loses O, forming a resistive surface rock-salt layer that causes capacity fade. This highlights the importance of cathode engineering when attempting to achieve higher energy densities with layered oxide cathodes, especially in those where O dominates the charge compensation mechanism.
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Oct 2024
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