A 6Li and 7Li MAS NMR study of the spinel-type manganese oxide LiMn2O4 and the rock salt-type manganese oxide Li2MnO3

Morgan, Keith R.; Collier, Susan; Burns, Gary R.; Ooi, Kenta

doi:10.1039/c39940001719

Cited by 49 publications

(70 citation statements)

References 13 publications

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“…The chargetransfer resistance obtained from the low-frequency relaxation loop also increases sharply with the ester additives in the course of cycling as a result of their reaction products contributing to enhanced cell resistance. 7 Li NMR analysis.-Wide-line (static) 7 Li NMR spectra for the six intercalated graphite samples are displayed in Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

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Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Smart

Ratnakumar

Surampudi

et al. 1999

J. Electrochem. Soc.

181

124

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Nonaqueous electrolyte solutions in current lithium-ion cells achieve stability toward the graphite anode (negative electrode) via the formation of passive surface films on the anode surface. These films are composed of reaction products resulting from electrolyte reduction and some reduced lithium. These films reportedly contain various lithium compounds, such as lithium carbonate (Li 2 CO 3 ), lithium oxide (Li 2 O), lithium hydroxide (LiOH), lithium alkoxides, lithium fluoride (LiF), as well as electrolyte salt reduction products that are still to be accurately characterized. 1 Relative amounts of these constituents are also equally uncertain. In addition to the expense of lithium for such surface films, termed solid electrolyte interphase (SEI), 2 a portion of lithium might be "trapped" in the anode material and is "kinetically inaccessible." Consequently, a differential exists between the intercalated lithium (charge capacity) and deintercalated lithium (discharge capacity), which is loosely termed irreversible capacity. This irreversible capacity depends not only on the rate of lithiation during the formation cycles and the temperature, but also on the extent of charge-discharge cycling, during which the surface film may grow. Irreversible capacity is typically estimated as the cumulative differential in the capacity after five cycles (one cycle in some reports), when the charge capacity/discharge capacity ratio approaches unity.It is difficult to separate the irreversible capacity into a component involving SEI formation and a component involving capacity loss due to kinetic effects, unless one of the components is estimated by a nonelectrochemical method. In this work, we attempted such a study on SEI formation on graphite in different electrolyte solutions using solid-state 7 Li nuclear magnetic resonance (NMR). Solid-state 7 Li NMR has been commonly used for qualitative detection and characterization of lithium intercalation in (and the SEI formation on) graphite and disordered carbons. 3-8 However, this technique has not been used extensively for quantitative determinations. In this work, the surface films were also examined ex situ by transmission electron microscopy (TEM) for elucidating the microstructure of film-covered graphite electrodes. These studies were further complemented by electrochemical impedance spectroscopy (EIS) measurements to understand the surface film characteristics of graphite anodes in different electrolytes.Improving low-temperature performance of lithium-ion cells remains a formidable technical challenge. The present investigation is an outgrowth of our previous studies 9 of novel electrolyte formulations for low-temperature performance. Similar efforts to improve the properties of electrolytes at low temperatures are being made elsewhere. 10-14 Our recent results have shown that a ternary mixture of alkyl carbonates, i.e., 1:1:1 (vol. %) of EC (ethylene carbonate):DEC (diethyl carbonate):DMC (dimethyl carbonate) with 1 M LiPF 6 exhibits favorable electrochemical characteris...

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Section: Resultsmentioning

confidence: 99%

“…Wide-line7 Li NMR spectra of (lithiated) cycled graphite electrodes in contact with electrolytes containing solvent mixtures of (1) EC ϩ DEC ϩ DMC, (2) EC ϩ DMC, (3) EC ϩ DEC, (4) EC ϩ DEC ϩ DMC ϩ MA, (5) EC ϩ DEC ϩ DMC ϩ EA, and (6) EC ϩ DMC ϩ DEC ϩ DME.…”

mentioning

confidence: 99%

Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Smart

Ratnakumar

Surampudi

et al. 1999

J. Electrochem. Soc.

181

124

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“…In particular, the 6,7 Li magic-angle spinning (MAS) NMR technique has been widely applied for the chemical structure characterization of the pristine and delithiated positive electrode materials, because it gives direct information about mobile Li + ions. 21 10 They suggested the existence of minor peaks other than that corresponding to a regular Li environment, and the relative intensities of the minor peaks are temperaturedependent. The sample with the P4 3 32 structure synthesized at 700°C seems to show a relatively narrow distribution with a least amount of minor peaks, while that with the Fd-3m structure calcined at lower and higher temperatures shows a much broader distribution.…”

Section: Introductionmentioning

confidence: 98%

Delithiation/Lithiation Behavior of LiNi_0.5Mn_1.5O₄ Studied by In Situ and Ex Situ ^6,7Li NMR Spectroscopy

et al. 2015

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Delithiation and lithiation behaviors of ordered spinel LiNi 0.5 Mn 1.5 O 4 and disordered spinel LiNi 0.4 Mn 1.6 O 4 were investigated by using in situ (in operando) 7 Li NMR and ex situ 6 Li MAS NMR spectroscopy. The in situ 7 Li monitoring of the ordered spinel revealed a clear appearance and subsequent disappearance of a new signal from the welldefined phase Li 0.5 Ni 0.5 Mn 1.5 O 4 , suggesting the two-phase reaction processes among Li 1.0 Ni 0.5 Mn 1.5 O 4 , Li 0.5 Ni 0.5 Mn 1.5 O 4 , and Li 0.0 Ni 0.5 Mn 1.5 O 4 . Also, for the disordered spinel, Li 0.5 Ni 0.4 Mn 1.6 O 4 was identified with a broad distribution in Li environment. High-resolution 6 Li MAS NMR spectra were also acquired for the delithiated and lithiated samples to understand the detailed local structure around Li ions. We suggested that the nominal Li-free phase Li 0.0 Ni 0.5 Mn 1.5 O 4 can accommodate a small amount of Li ions in its structure. The tetragonal phases Li 2.0 Ni 0.5 Mn 1.5 O 4 and Li 2.0 Ni 0.4 Mn 1.6 O 4 , which occurred when the cell was discharged down to 2.0 V, were very different in the Li environment from each other. It is found that 6,7 Li NMR is highly sensitive not only to the Ni/Mn ordering in LiNi 0.5 Mn 1.5 O 4 but also to the valence changes of Ni and Mn on charge−discharge process.

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“…The isotropic signals, as determined by the variation of the spinning frequency (not shown), are indicated by vertical bars. The pure spinel (x = 0) shows a hyperfine shifted main signal at 501 ppm (site 8a), [21] and two very minor populations at 536 and 573 ppm, which have been assigned to Li at the Mn 16d and the interstitial 16c sites in a non-perfect stoichiometry by Verhoeven et al [22]. The compositions x = 0.1 and 0.3 contain, according to the XRD data, spinel as the main phase and admixtures of lithium manganate Li 2 MnO 3 .…”

Section: Resultsmentioning

confidence: 99%

Formation of stable phases of the Li–Mn–Co oxide system at 800 °C under ambient oxygen pressure

Shpak

Swamy

Dittmer

et al. 2015

J Solid State Electrochem

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The synthesis method of lithiated d-metal oxides using molten formate mixtures as precursors has been developed and the isothermal (800°C) cross section of pseudo ternary Li-Mn-Co oxide system under ambient oxygen pressure has been investigated by XRD, 7 Li NMR, and galvanostatic electrochemical methods. Special attention has been paid to the compositions inside the quadrangle restricted by solid solutions LiCoO 2 -LiCo 0.85 Mn 0.15 O 2 with the layered structure of α-NaFeO 2 and solid solutions LiMn 2 O 4 -LiMnCoO 4 with the structure of spinel. It was found that, depending on the composition, three types of equilibrium phases could be formed: spinels Li[Li,Mn,Co] 2 O 4 with a part of Li atoms in octahedral sites, cation-deficit layered compounds Li 1 − δ [Co,Mn]O 2 , and Li 2 MnO 3 . Areas of (co)existence of these phases were plotted on the composition plane of the pseudo-ternary Li-Mn-Co system. Electrochemical properties of the compositions inside the quadrangle LiCoO 2 -LiCo 0.85 Mn 0.15 O 2 -LiMn 2 O 4 -LiMnCoO 4 are determined by the content and average oxidation number of Mn atoms, which is higher than in the normal spinels Li[Mn, Co] 2 O 4 . Thus, the specific capacities of the polyphase compositions are lower in comparison with the binary solid solutions Li[Mn,Co] 2 O 4 or pure LiCoO 2 .

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A 6Li and 7Li MAS NMR study of the spinel-type manganese oxide LiMn2O4 and the rock salt-type manganese oxide Li2MnO3

Abstract: 6Li and 7Li MAS NMR spectroscopy is used t o identify distinct lithium sites in t w o paramagnetic manganese oxides: spinel-type LiMn204 and rock salt-type Li2Mn03.

Cited by 49 publications

References 13 publications

Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Delithiation/Lithiation Behavior of LiNi_0.5Mn_1.5O₄ Studied by In Situ and Ex Situ ^6,7Li NMR Spectroscopy

Formation of stable phases of the Li–Mn–Co oxide system at 800 °C under ambient oxygen pressure

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A 6Li and 7Li MAS NMR study of the spinel-type manganese oxide LiMn2O4 and the rock salt-type manganese oxide Li2MnO3

Abstract: 6Li and 7Li MAS NMR spectroscopy is used t o identify distinct lithium sites in t w o paramagnetic manganese oxides: spinel-type LiMn204 and rock salt-type Li2Mn03.

Cited by 49 publications

References 13 publications

Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Irreversible Capacities of Graphite in Low‐Temperature Electrolytes for Lithium‐Ion Batteries

Delithiation/Lithiation Behavior of LiNi0.5Mn1.5O4 Studied by In Situ and Ex Situ 6,7Li NMR Spectroscopy

Formation of stable phases of the Li–Mn–Co oxide system at 800 °C under ambient oxygen pressure

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Delithiation/Lithiation Behavior of LiNi_0.5Mn_1.5O₄ Studied by In Situ and Ex Situ ^6,7Li NMR Spectroscopy