B18-Core EXAFS
I09-Surface and Interface Structural Analysis
|
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.
|
May 2025
|
|
B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I09-Surface and Interface Structural Analysis
|
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.
|
Feb 2025
|
|
B18-Core EXAFS
I21-Resonant Inelastic X-ray Scattering (RIXS)
|
Matthew
Ogley
,
Ashok S.
Menon
,
Beth J.
Johnston
,
Gaurav
Pandey
,
Innes
Mcclelland
,
Xiaoqun
Shi
,
Stefano
Agrestini
,
Veronica
Celorrio
,
Gabriel E.
Perez
,
Samuel G.
Booth
,
Jordi
Cabana
,
Serena A.
Cussen
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33292, 33173]
Open Access
Abstract: In layered lithium transition metal oxide cathodes, high-voltage operation is accompanied by the formation of oxygen dimers, which are widely used as an indicator of oxygen-redox activity. However, understanding the role that oxygen dimerization plays in facilitating charge compensation is still needed. Li2NiO3 (a 3d8L2-containing compound, where L is a ligand hole) is studied as a model system, where oxygen dimerization is shown to occur without cathode oxidation. Electrochemical cycling results in a net reduction of the cathode, accompanied by structural transformations, despite spectroscopic features of oxygen dimers arising at the top-of-charge. Here, oxygen dimerization is shown to coexist alongside a structurally transformed and electronically reduced cathode structure, thus highlighting that O dimerization is independent of bulk redox processes. This makes it clear that a thermodynamically derived transformation toward a reduced phase remains the only variable capable of generating O–O dimers in Li2NiO3.
|
Aug 2024
|
|
I09-Surface and Interface Structural Analysis
|
Galo J.
Paez Fajardo
,
Eleni
Fiamegkou
,
James A.
Gott
,
Heng
Wang
,
Israel
Temprano
,
Ieuan D.
Seymour
,
Matthew J. W.
Ogley
,
Ashok S.
Menon
,
Ifan E. L.
Stephens
,
Muhammad
Ans
,
Tien-Lin
Lee
,
Pardeep K.
Thakur
,
Wesley M.
Dose
,
Michaël F. L.
De Volder
,
Clare P.
Grey
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[30201]
Open Access
Abstract: Oxygen loss at high voltages in Ni-rich NMC//graphite Li-ion batteries promotes degradation, but increasing evidence from full cells reveals that the depth of discharge choice can further accelerate aging, i.e., synergistic degradation. In this Letter, we employ cycling protocols to examine the origin of the synergistic degradation for single crystal Ni-rich NMC//graphite pouch cells. In regimes where oxygen loss is not promoted (V < 4.3 V), a lower cutoff voltage does not affect capacity retention (after 100 cycles), despite significant graphite expansion occurring. In contrast, when NMC surface oxygen loss is induced (V > 4.3 V), deeper depth of discharge leads to pronounced faster aging. Using a combination of post-mortem analysis and density functional theory, we present a mechanistic description of surface phase densification and evolution as a function of voltage and cycling. The detrimental impact of this mechanism on lithium-ion kinetics is used to explain the observed cycling results.
|
Nov 2023
|
|
B18-Core EXAFS
I11-High Resolution Powder Diffraction
|
Diamond Proposal Number(s):
[25166, 14239]
Open Access
Abstract: A Mn2+-Li-Nb disordered rock-salt oxide cathode is prepared by a solid-state reaction under 5% H2/N2, and its electrochemical property shows a high voltage plateau at 4.8 V, with irreversible structural changes in the first cycle due to O redox processes; this is supported by powder X-ray diffraction and ex-situ laboratory Mn K-edge XANES data.
|
Oct 2023
|
|
I09-Surface and Interface Structural Analysis
|
Galo J.
Paez Fajardo
,
Meltiani
Belekoukia
,
Satish
Bolloju
,
Eleni
Fiamegkou
,
Ashok S.
Menon
,
Zachary
Ruff
,
Zonghao
Shen
,
Nickil
Shah
,
Erik
Bjorklund
,
Mateusz Jan
Zuba
,
Tien-Lin
Lee
,
Pardeep K.
Thakur
,
Robert S.
Weatherup
,
Ainara
Aguadero
,
Melanie J.
Loveridge
,
Clare
Grey
,
Louis F. J.
Piper
Open Access
Abstract: The capacity retention of commercially-sourced pouch cells with single crystal Al surface-doped Ni-rich cathodes (LiNi0.834Mn0.095Co0.071O2) is examined. The degradation-induced capacity fade becomes more pronounced as the upper-cut-off voltage (UCV) increases from 4.2 V to 4.3 V (vs. graphite) at a fixed cycling temperature (either 25 or 40 °C). However, cycles with 4.3 V UCV (slightly below the oxygen loss onset) show better capacity retention upon increasing the cycling temperature from 25 °C to 40 °C. Namely, after 500 cycles at 4.3 V UCV, cycling temperature at 40 °C retains 85.5% of the initial capacity while cycling at 25 °C shows 75.0% capacity retention. By employing a suite of electrochemical, X-ray spectroscopy and secondary ion mass spectrometry techniques, we attribute the temperature-induced improvement of the capacity retention at high UCV to the combined effects of Al surface-dopants, electrochemically resilient single crystal Ni-rich particles, and thermally-improved Li kinetics translating into better electrochemical performance. If cycling remains below the lattice oxygen loss onset, improved capacity retention in industrial cells should be achieved in single crystal Ni-rich cathodes with the appropriate choice of cycling parameter, particle quality, and particle surface dopants.
|
Sep 2023
|
|
I09-Surface and Interface Structural Analysis
I21-Resonant Inelastic X-ray Scattering (RIXS)
|
A. S.
Menon
,
B. J.
Johnston
,
S. G.
Booth
,
L.
Zhang
,
K.
Kress
,
B. E.
Murdock
,
G.
Paez Fajardo
,
N. N.
Anthonisamy
,
N.
Tapia-Ruiz
,
S.
Agrestini
,
M.
Garcia-Fernandez
,
K.
Zhou
,
P. K.
Thakur
,
T. L.
Lee
,
A. J.
Nedoma
,
S. A.
Cussen
,
L. F. J.
Piper
Diamond Proposal Number(s):
[29104, 29113]
Open Access
Abstract: The desire to increase the energy density of stoichiometric layered
Li
TM
O
2
(TM = 3d transition metal) cathode materials has promoted investigation into their properties at high states of charge. Although there is increasing evidence for pronounced oxygen participation in the charge compensation mechanism, questions remain whether this is true
O
-redox, as observed in
Li
-excess cathodes. Through a high-resolution
O
K-edge resonant inelastic x-ray spectroscopy (RIXS) study of the
Mn
-free
Ni
-rich layered oxide
Li
Ni
0.98
W
0.02
O
2
, we demonstrate that the same oxidized oxygen environment exists in both
Li
-excess and non-
Li
-excess systems. The observation of identical RIXS loss features in both classes of compounds is remarkable given the differences in their crystallographic structure and delithiation pathways. This lack of a specific structural motif reveals the importance of electron correlation in the charge compensation mechanism for these systems and indicates how a better description of charge compensation in layered oxides is required to understand anionic redox for energy storage.
|
Mar 2023
|
|
I11-High Resolution Powder Diffraction
|
Ashok S.
Menon
,
Seda
Ulusoy
,
Dickson O.
Ojwang
,
Lars
Riekehr
,
Christophe
Didier
,
Vanessa K.
Peterson
,
German
Salazar-Alvarez
,
Peter
Svedlindh
,
Kristina
Edström
,
Cesar Pay
Gomez
,
William R.
Brant
Diamond Proposal Number(s):
[21804]
Open Access
Abstract: Li- and Mn-rich layered oxides show significant promise as electrode materials for future Li-ion batteries. However, an accurate description of its crystallography remains elusive, with both single-phase solid solution and multiphase structures being proposed for high performing materials such as Li1.2Mn0.54Ni0.13Co0.13O2. Herein, we report the synthesis of single- and multiphase variants of this material through sol–gel and solid-state methods, respectively, and demonstrate that its crystallography is a direct consequence of the synthetic route and not necessarily an inherent property of the composition, as previously argued. This was accomplished via complementary techniques that probe the bulk and local structure followed by in situ methods to map the synthetic progression. As the electrochemical performance and anionic redox behavior are often rationalized on the basis of the presumed crystal structure, clarifying the structural ambiguities is an important step toward harnessing its potential as an electrode material.
|
Feb 2021
|
|
I09-Surface and Interface Structural Analysis
|
Diamond Proposal Number(s):
[23159]
Open Access
Abstract: The coupling of nickel‐rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes with high‐capacity silicon–graphite (Si–Gr) anodes is one promising route to further increase the energy density of lithium‐ion batteries. Practically, however, the cycle life of such cells is seriously hindered due to continuous electrolyte degradation on the surfaces of both electrodes. In this study, tris(trimethylsilyl) phosphite (TMSPi) is introduced as an electrolyte additive to improve the electrochemical performance of the NMC811/Si–Gr full cells through formation of protective surface layers at the electrode/electrolyte interfaces. This is thought to prevent the surface fluorination of the active materials and enhance interfacial stability. Notably, TMSPi is shown to significantly reduce the overpotential and operando X‐ray diffraction (XRD) confirms that an irreversible “two‐phase” transition reaction caused by the formed adventitious Li2CO3 layer on the surface of NMC811 can transfer to a solid‐solution reaction mechanism with TMSPi‐added electrolyte. Moreover, influences of TMSPi on the cathode electrolyte interphase (CEI) on the NMC811 and solid electrolyte interphase (SEI) on the Si–Gr are systematically investigated by electron microscopy and synchrotron‐based X‐ray photoelectron spectroscopy which allows for the nondestructive depth‐profiling analysis of chemical compositions and oxidation states close to the electrode surfaces.
|
Jun 2020
|
|
I11-High Resolution Powder Diffraction
|
Diamond Proposal Number(s):
[19093]
Abstract: With the potential of delivering reversible capacities of up to 300 mAh/g, Li-rich transition metal oxides hold great promise as cathode materials for future Li-ion batteries. However, a cohesive synthesis-structure-electrochemistry relationship is still lacking for these materials, which impedes progress in the field. This work investigates how and why different synthesis routes, specifically solid-state and modified Pechini sol-gel methods, affect the properties of Li2MnO3, a compositionally simple member of this material system. Through a comprehensive investigation of the syn-thesis mechanism along with crystallographic, morphological and electrochemical characterization, the effects of different synthesis routes were found to predominantly influence the degree of stacking faults and particle morphology. That is, the modified Pechini method produced isotropic spherical particles with approx. 57% faulting and the solid state samples possessed heterogeneous morphology with approx. 43% faulting probability. Inevitably, these differences lead to variations in electrochemical performance. This study accentuates the importance of understanding how syn-thesis affects the electrochemistry of these materials, which is critical considering the crystallographic and electrochemical complexities of the class of materials more generally. The methodology employed here is extendable to studying synthesis-property relationships of other compositionally complex Li-rich layered oxide systems.
|
Jan 2020
|
|
