Stoichiometrically driven disorder and local diffusion in NMC cathodes

Ashton, Thomas E.; Baker, Peter J.; Sotelo-Vázquez, Carlos; Footer, Charles; Kojima, Kenji; Matsukawa, T.; Kamiyama, Takashi; Darr, Jawwad A.

doi:10.1039/d1ta01639c

Cited by 14 publications

(17 citation statements)

References 49 publications

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“…At OCV, with close to full Li occupancy in the cathode, D Li is at its lowest due to the difficulty of Li + ion diffusion to a vacant site (Figure c). The value of D Li found before cycling of ∼3.4 × 10 –11 cm 2 s –1 compares well to that found by a previous μSR study of NMC811 (reported as 2.9 × 10 –11 cm 2 s –1 ) …”

Section: Resultssupporting

confidence: 90%

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy

et al. 2023

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Ni-rich layered oxide cathode materials such as LiNi0.8Mn0.1Co0.1O2 (NMC811) are widely tipped as the next-generation cathodes for lithium-ion batteries. The NMC class offers high capacities but suffers an irreversible first cycle capacity loss, a result of slow Li+ diffusion kinetics at a low state of charge. Understanding the origin of these kinetic hindrances to Li+ mobility inside the cathode is vital to negate the first cycle capacity loss in future materials design. Here, we report on the development of operando muon spectroscopy (μSR) to probe the Å-length scale Li+ ion diffusion in NMC811 during its first cycle and how this can be compared to electrochemical impedance spectroscopy (EIS) and the galvanostatic intermittent titration technique (GITT). Volume-averaged muon implantation enables measurements that are largely unaffected by interface/surface effects, thus providing a specific characterization of the fundamental bulk properties to complement surface-dominated electrochemical methods. First cycle measurements show that the bulk Li+ mobility is less affected than the surface Li+ mobility at full depth of discharge, indicating that sluggish surface diffusion is the likely cause of first cycle irreversible capacity loss. Additionally, we demonstrate that trends in the nuclear field distribution width of the implanted muons during cycling correlate with those observed in differential capacity, suggesting the sensitivity of this μSR parameter to structural changes during cycling.

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Section: Resultssupporting

confidence: 90%

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy

et al. 2023

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“…Note that for LCO, velocities cannot be extracted during lithiation as it is beyond our time resolution (100 s). These values sit at the lower end of those reported previously in the literature (1 nm s -1 to 50 nm s -1 ) 24,[59][60][61][62][63][64] . However, in this work, the transport velocities reported are through individual polycrystalline particles i.e.…”

Section: Surface-to-core Transportsupporting

confidence: 50%

Three-dimensional operando optical imaging of single particle and electrolyte heterogeneities inside Li-ion batteries

Pandya

Valzania

Dorchies

et al. 2022

Preprint

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Understanding (de)lithiation heterogeneities in battery materials is key to ensuring optimal electrochemical performance and developing better energy storage devices. However, this remains challenging due to the complex three dimensional morphology of microscopic electrode particles, the involvement of both solid and liquid phase reactants, and range of relevant timescales (seconds to hours). Here, we overcome this problem and demonstrate the use of bench-top laser scanning confocal microscopy for simultaneous three-dimensional operando measurement of lithium ion dynamics in single particles, and the electrolyte, in batteries. We examine two technologically important cathode materials that are known to suffer from intercalation heterogeneities: LixCoO2 and LixNi0.8Mn0.1Co0.1O2. The single-particle surface-to-core transport velocity of Li-phase fronts, and volume changes – as well as their inter-particle heterogeneity – are captured as a function of C-rate, and benchmarked to previous ensemble measurements. Additionally, we visualise heterogeneities in the bulk and at the surface of particles during cycling, and image the formation of spatially non-uniform concentration gradients within the liquid electrolyte. Importantly, the conditions under which optical imaging can be performed inside absorbing and multiply scattering materials such as battery intercalation compounds are outlined.

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“…Above this temperature, a brief period of increasing 003 R /104 R was observed, but was followed by a subsequent decrease, indicating a return to a more disordered state. At no point did the 003 R /104 R ratio approach the typical value of 1.3 reported for completely site‐ordered LiNi 0.8 Mn 0.1 Co 0.1 O 2 [ 31 ] and observed by ex situ XRD (Figure S1a, Supporting Information) for powders held at 750 °C for 10 h. This low 003 R /104 R indicates a certain amount of disorder (i.e., Ni in the Li layer), and is partially due to the absence of the typical extended hold at the final calcination temperature.…”

Section: Resultsmentioning

confidence: 99%

“…Co and Mn were only included in the 3b positions. [9,31] Domain sizes were modeled using Lorentzian peak broadening not accounted for by instrumental broadening. Example comparisons of calculated and observed diffraction patterns are shown in Figure S11, Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

“…Subsequent heating above 500 °C showed moderate increases in the 003 R /104 R ratio to a maximum of ≈0.8, higher than the sample without pre-conversion but still below the expected value of ≈1.3. [31] The overall reaction progress was evaluated from the in situ XRD data by fitting well-separated peaks from each phase with Gaussian curves. While whole-pattern fitting is often the preferred method for tracking phase fractions, the overlap between partially ordered rock salt intermediate and partially disordered LiNi 0.8 Mn 0.1 Co 0.1 O 2 phases introduced a high level of covariance in the refined parameters.…”

Section: Experimental Characterizationmentioning

confidence: 99%

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The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High‐Nickel NMC Cathodes

Wolfman

Wang

García

et al. 2022

Advanced Energy Materials

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both thermally and electrochemically. [2][3][4] Cathodes with high nickel content (y > 0.8) are also more difficult to synthesize, requiring oxygenrich calcination conditions, and are more prone to lithium/transition-metal siteexchange. [5][6][7][8][9] Thermal parameters play a critical role in the morphology of the final cathode, which strongly affects its rate performance and cyclability. Advanced understanding of the underlying chemistry during synthesis is necessary to enable Ni-rich cathodes to operate closer to their theoretical performance limits.Preparation of Ni-rich LiNi y Mn z Co 1−y−z O 2 cathode material is a two-stage process, first involving the co-precipitation of a Ni 0.8 Mn 0.1 Co 0.1 (OH) 2 species followed by calcination of the resultant precursor with a lithium salt, typically LiOH•H 2 O. Calcination, which requires prolonged times at temperatures up to 750-900 °C in pure oxygen condition for Ni-rich cathodes, is the most energy intensive step. [10] During this process, water is lost from Ni y Mn z Co 1−y−z (OH) 2 , and lithium and oxygen enter the structure forming the final LiNi y Mn z Co 1−y−z O 2 cathode. The details of this transformation are not fully understood. While both the hydroxide precursor and final LiNi y Mn z Co 1−y−z O 2 cathode share a layered structure, prior research has implicated an intermediate cubic structure resembling rock salt, [11] recently confirmed using in situ powder X-ray diffraction (XRD). [12,13] These phases share an oxygen sub-lattice, and so the mechanism has been ascribed to a topotactic transformation involving extensive cation ordering. [14,15] In addition, several competing processes occur at high temperatures, where cation mixing and particle growth have been shown to depend on calcination temperature and hold time. [16] The final cathode performance is closely tied to the morphology of the constituent particles. [17] LiNi 0.8 Mn 0.1 Co 0.1 O 2 often has a hierarchical structure consisting of large (≈10 μm) agglomerates of small (≈100 nm) single crystal primary particles. Secondary particle size is largely controlled by coprecipitation conditions, whereas primary particles are affected by thermal parameters during calcination.Smaller particles (<100 nm) result in higher rate capability, [18][19][20][21] attributed to increased surface area and shorter Nanoscale morphology has a direct impact on the performance of materials for electrochemical energy storage. Despite this importance, little is known about the evolution of primary particle morphology nor its effect on chemical pathways during synthesis. In this study, operando characterization is combined with atomic-scale and continuum simulations to clarify the relationship between morphology of cathode primary particles and their lithiation during calcination of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC-811). This combined approach reveals a key role for surface oxygen adsorption in facilitating the lithiation reaction by promoting metal diffusion and oxidation, and simultaneously providing surface sites for ...

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Stoichiometrically driven disorder and local diffusion in NMC cathodes

Abstract: Major structural differences in lithium nickel manganese cobalt oxides (NMC) prepared under identical conditions have been uncovered using neutron powder diffraction. Sample NMC-622 was obtained as a single R3 ̅m...

Cited by 14 publications

References 49 publications

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy

Three-dimensional operando optical imaging of single particle and electrolyte heterogeneities inside Li-ion batteries

The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High‐Nickel NMC Cathodes

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Stoichiometrically driven disorder and local diffusion in NMC cathodes

Abstract: Major structural differences in lithium nickel manganese cobalt oxides (NMC) prepared under identical conditions have been uncovered using neutron powder diffraction. Sample NMC-622 was obtained as a single R3 ̅m...

Cited by 14 publications

References 49 publications

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi0.8Mn0.1Co0.1O2 (NMC811) Cathodes Using Operando Muon Spectroscopy

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi0.8Mn0.1Co0.1O2 (NMC811) Cathodes Using Operando Muon Spectroscopy

Three-dimensional operando optical imaging of single particle and electrolyte heterogeneities inside Li-ion batteries

The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High‐Nickel NMC Cathodes

Contact Info

Product

Resources

About

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy

Direct Observation of Dynamic Lithium Diffusion Behavior in Nickel-Rich, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) Cathodes Using Operando Muon Spectroscopy