Electronic structure variation of the surface and bulk of a LiNi0.5Mn1.5O4cathode as a function of state of charge: X-ray absorption spectroscopic study

Zhou, Jigang; Hong, Da; Wang, Jian; Hu, Yongfeng; Xie, Xiaohua; Fang, Hai‐Tao

doi:10.1039/c4cp01436g

Cited by 48 publications

(59 citation statements)

References 27 publications

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“…[45][46][47] It has also been reported that oxygen anions are involved in charge compensation through reversible charge redistribution between transition metal and oxygen in spinel 48 and layered oxides (e.g., NMC-333). 49 However, for the NMC-333 material, only the TEY mode was used to investigate the oxygen K-edge in that study, which only provided information about surface oxygen.…”

Section: Resultsmentioning

confidence: 99%

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

Tian

Nordlund

Xin

et al. 2018

J. Electrochem. Soc.

129

125

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Nickel-rich layered materials are emerging as cathodes of choice for next-generation high energy density lithium ion batteries intended for electric vehicles. This is because of their higher practical capacities compared to compositions with lower Ni content, as well as the potential for lower raw materials cost. The higher practical capacity of these materials comes at the expense of shorter cycle life, however, due to undesirable structure and chemical transformations, especially at particle surfaces. To understand these changes more fully, the charge compensation mechanism and bulk and surface structural changes of LiNi 0.6 Mn 0.2 Co 0.2 O 2 were probed using synchrotron techniques and electron energy loss spectroscopy in this study. In the bulk, both the crystal and electronic structure changes are reversible upon cycling to high voltages, whereas particle surfaces undergo significant reduction and structural reconstruction. While Ni is the major contributor to charge compensation, Co and O (through transition metal-oxygen hybridization) are also redox active. An important finding from depth-dependent transition metal L-edge and O K-edge X-ray spectroscopy is that oxygen redox activity exhibits depth-dependent characteristics. This likely drives the structural and chemical transformations observed at particle surfaces in Ni-rich materials. The need for lithium-ion batteries with higher energy density and lower cost than currently available, particularly for transport applications, has led to intensified interest in Ni-rich NMC (LiNi x Mn y Co z O 2 ; x+y+z≈1, where x>y) cathode materials.1-5 These materials deliver higher practical capacities in a typically used voltage range than NMCs with lower Ni content (e.g., LiNi 1/3 Mn 1/3 Co 1/3 O 2 or NMC-333), and most formulations contain less of the expensive Co component, reducing raw material costs. The increase in practical capacity roughly scales with the Ni content, but comes at the expense of cycle life and thermal stability at high states-of-charge (SOC). 6 To circumvent these problems, several different strategies have been utilized to improve cycling, particularly to higher potentials. These include partial substitution with Ti 7-9 or Zr, 10 engineering the micro-or nano-structure to reduce surface Ni content using metal segregation, 11 surface pillared structures, 12 and concentration gradients, 13 coating particle surfaces, 14 and development of electrolyte additives. 15,16 While all of these approaches have resulted in improvements, further understanding of the factors that lead to capacity fading is clearly needed in order to meet the stringent performance requirements of traction applications.The formation of a resistive cathode/electrolyte interphase (CEI), such as an electrolyte decomposition layer, has been observed during cycling of LiNi 0. 20 In the study of NMC-532, it was found that surface reconstruction to a rock salt phase dominates when high voltage (4.8 V) cutoffs are used due to oxygen loss under the highly oxidizing conditions, while ...

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Section: Resultsmentioning

confidence: 99%

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

Tian

Nordlund

Xin

et al. 2018

J. Electrochem. Soc.

129

125

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“…Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single-and/or multiple-level configurations. C ontrolled formation of 3D functional mesostructures is a topic of broad and increasing interest, particularly in the past decade (1)(2)(3)(4)(5)(6)(7)(8)(9). Uses of such structures have been envisioned in nearly every type of micro/ nanosystem technology, including biomedical devices (10)(11)(12), microelectromechanical components (13,14), photonics and optoelectronics (15)(16)(17), metamaterials (16,(18)(19)(20)(21), electronics (22,23), and energy storage (24, 25).…”

Section: Batteriesmentioning

confidence: 99%

“…Uses of such structures have been envisioned in nearly every type of micro/ nanosystem technology, including biomedical devices (10)(11)(12), microelectromechanical components (13,14), photonics and optoelectronics (15)(16)(17), metamaterials (16,(18)(19)(20)(21), electronics (22,23), and energy storage (24, 25). Although volumetric optical exposures (4,6,19), fluidic self-assembly (3,26,27), residual stress-induced bending (1,13,21,(28)(29)(30)(31), and templated growth (7,8,32) can be used to realize certain classes of structures in certain types of materials, techniques that rely on rastering of fluid nozzles or focused beams of light provide the greatest versatility in design (5,6). The applicability of these latter methods, however, only extends directly to materials that can be formulated as inks or patterned by exposure to light or other energy sources, and indirectly to those that can be depo-sited onto or into sacrificial 3D structures formed with these materials (5,6,18,19).…”

Section: Batteriesmentioning

confidence: 99%

“…We thank M. C. Croft for helpful discussions and Y. Belyavina for assistance with the conceptual schematics shown inFig. 1.Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling Sheng Xu, 1 * Zheng Yan, 1 * Kyung-In Jang, 1 Wen Huang, 2 Haoran Fu,3,4 Jeonghyun Kim,1,5 Zijun Wei, 1 Matthew Flavin, 1 Joselle McCracken, 6 Renhan Wang, 1 Adina Badea, 6 Yuhao Liu, 1 Dongqing Xiao, 6 Guoyan Zhou, 3,7 Jungwoo Lee, 1,5 Ha Uk Chung, 1 Huanyu Cheng, 1,3 Wen Ren, 6 Anthony Banks, 1 Xiuling Li, 2 Ungyu Paik, 5 Ralph G. Nuzzo, 1,6 Yonggang Huang, 3 † Yihui Zhang, 3,8 † John A. Rogers 1,2,6,9 †…”

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confidence: 99%

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In situ visualization of Li/Ag ₂ VP ₂ O ₈ batteries revealing rate-dependent discharge mechanism

Kirshenbaum

Bock

Lee

et al. 2015

Science

107

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The functional capacity of a battery is observed to decrease, often quite dramatically, as discharge rate demands increase. These capacity losses have been attributed to limited ion access and low electrical conductivity, resulting in incomplete electrode use. A strategy to improve electronic conductivity is the design of bimetallic materials that generate a silver matrix in situ during cathode reduction. Ex situ x-ray absorption spectroscopy coupled with in situ energy-dispersive x-ray diffraction measurements on intact lithium/silver vanadium diphosphate (Li/Ag2VP2O8) electrochemical cells demonstrate that the metal center preferentially reduced and its location in the bimetallic cathode are rate-dependent, affecting cell impedance. This work illustrates that spatial imaging as a function of discharge rate can provide needed insights toward improving realizable capacity of bimetallic cathode systems.

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“…18 While these investigations often average over many particles (bulk measurements) and large areas, our studies utilize spatially resolved Xray fluorescence spectrometry (micro-XRF) to visualize changes in the stoichiometry and morphology throughout the electrode. Chemical and structural heterogeneities in electrodes are critical factors for aging and degradation of active battery materials causing, e.g., localized heat generation and overcharge or overdischarge.…”

Section: ■ Introductionmentioning

confidence: 99%

Correlation between Chemical and Morphological Heterogeneities in LiNi_0.5Mn_1.5O₄ Spinel Composite Electrodes for Lithium-Ion Batteries Determined by Micro-X-ray Fluorescence Analysis

et al. 2015

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The high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel is a promising material for high-energy battery applications, despite problems of capacity fade. This is due in part to transition metal leaching that produces chemical and morphological inhomogeneities. Using fast micro-X-ray fluorescence spectroscopy to scan the sample at medium spatial resolution (500 nm) over millimeter ranges, effects of cycling rate and state-of-charge on the elemental distribution (Ni and Mn) for LiNi 0.5 Mn 1.5 O 4 /carbon composite electrodes in LNMO/Li cells are visualized. Charge distribution is imaged by mapping the Ni oxidation state by acquisition of a stack of elemental maps in the vicinity of the Ni K edge. Our results show significant effects on morphology and elemental distribution, such as formation of elemental hot-spots and material erosion, becoming more pronounced at higher cycling rates. In nickel hot-spots, we observed hampered oxidation of nickel during charging. ■ INTRODUCTIONThe high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel is a promising material for high-energy battery applications because of its high operation potential of ∼4.7 V versus Li + /Li 0 . However, this high potential lies outside the thermodynamic window of stability for conventional electrolyte solutions used in Li-ion batteries, and therefore presents a critical hurdle toward application. 1 As one result, oxidation of the electrolyte by the active material produces passivating products, causing reduced cycle life and capacity fade of the material. 2−4 Furthermore, Mn-containing phases such as the LiMn 2 O 4 spinel and also the LiNi 0.5 Mn 1.5 O 4 spinel are known to be susceptible to leaching of Mn 2+ and Ni 2+ to the electrolyte, 5 possibly as a consequence of the parasitic reactions with the electrolyte, 6,7 thereby causing elemental inhomogeneities in the electrodes. Formation of hydrofluoric acid, caused by trace amounts of water in the electrolyte, is regarded as one origin for this cathode corrosion. 8,9 The effect on capacity fade is especially pronounced in LNMO/graphite full cells, because of the detrimental contribution of the deposited 3d metals on the anode impacting the solid-electrolyte-interphase (SEI) growth on its surface. 2,10−13 The interplay between Ni and Mn cations leads to complex ordering effects, formation of secondary rock-salt structures, variable Mn 3+ content, and oxygen vacancies that all significantly influence electrochemical performance and are determined by the synthesis conditions. 6,14−16 Detailed investigations of the composition−structure relationship in LNMO spinel showed systematic deviations from the theoretical stoichiometry involving an excess of Mn. To compensate for the formation of excess Mn 3+ , formation of a rock-salt-type structure with a lower Mn/Ni ratio was observed. 17 A systematic study by Choi and Manthiram 5 on manganese dissolution into the electrolyte revealed a correlation with the Mn oxidation state, with samples containing initially more Mn 3+ being prone to the disproportionation reaction...

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Electronic structure variation of the surface and bulk of a LiNi_0.5Mn_1.5O₄cathode as a function of state of charge: X-ray absorption spectroscopic study

Cited by 48 publications

References 27 publications

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

In situ visualization of Li/Ag ₂ VP ₂ O ₈ batteries revealing rate-dependent discharge mechanism

Correlation between Chemical and Morphological Heterogeneities in LiNi_0.5Mn_1.5O₄ Spinel Composite Electrodes for Lithium-Ion Batteries Determined by Micro-X-ray Fluorescence Analysis

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Electronic structure variation of the surface and bulk of a LiNi0.5Mn1.5O4cathode as a function of state of charge: X-ray absorption spectroscopic study

Cited by 48 publications

References 27 publications

Depth-Dependent Redox Behavior of LiNi0.6Mn0.2Co0.2O2

Depth-Dependent Redox Behavior of LiNi0.6Mn0.2Co0.2O2

In situ visualization of Li/Ag 2 VP 2 O 8 batteries revealing rate-dependent discharge mechanism

Correlation between Chemical and Morphological Heterogeneities in LiNi0.5Mn1.5O4 Spinel Composite Electrodes for Lithium-Ion Batteries Determined by Micro-X-ray Fluorescence Analysis

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Electronic structure variation of the surface and bulk of a LiNi_0.5Mn_1.5O₄cathode as a function of state of charge: X-ray absorption spectroscopic study

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

Depth-Dependent Redox Behavior of LiNi_0.6Mn_0.2Co_0.2O₂

In situ visualization of Li/Ag ₂ VP ₂ O ₈ batteries revealing rate-dependent discharge mechanism

Correlation between Chemical and Morphological Heterogeneities in LiNi_0.5Mn_1.5O₄ Spinel Composite Electrodes for Lithium-Ion Batteries Determined by Micro-X-ray Fluorescence Analysis