Structure of the Li4Ti5O12 anode during charge-discharge cycling

Pang, Wei Kong; Peterson, Vanessa K.; Sharma, Neeraj; Shiu, Je-Jang; Wu, She‐Huang

doi:10.1017/s0885715614001067

Cited by 14 publications

(9 citation statements)

References 15 publications

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“…During the first battery charge from OCV to 2.5 V vs LTO, the LTO 222 reflection intensity remained nearly unchanged while its position shifted to lower 2θ, indicating expansion. This response was followed by a monotonic increase in the reflection intensity alongside a shift in position to higher 2θ, indicating contraction, which continued until the end of lithiation (Figure a), consistent with Li + diffusion between the 8 a and 16 c sites occurring via the 32 e site, as previously observed. − …”

Section: Resultssupporting

confidence: 80%

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

et al. 2016

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The mechanism of capacity fade of the Li2MnO3·LiMO2 (M = Li, Ni, Co, Mn) composite positive electrode within a full cell was investigated using a combination of operando neutron powder diffraction and transmission X-ray microscopy methods, enabling the phase, crystallographic, and morphological evolution of the material during electrochemical cycling to be understood. The electrode was shown to initially consist of 73(1) wt % R3̅m LiMO2 with the remaining 27(1) wt % C2/m Li2MnO3 likely existing as an intergrowth. Cracking in the Li2MnO3·LiMO2 electrode particle under operando microscopy observation was revealed to be initiated by the solid-solution reaction of the LiMO2 phase on charge to 4.55 V vs Li(+)/Li and intensified during further charge to 4.7 V vs Li(+)/Li during the concurrent two-phase reaction of the LiMO2 phase, involving the largest lattice change of any phase, and oxygen evolution from the Li2MnO3 phase. Notably, significant healing of the generated cracks in the Li2MnO3·LiMO2 electrode particle occurred during subsequent lithiation on discharge, with this rehealing being principally associated with the solid-solution reaction of the LiMO2 phase. This work reveals that while it is the reduction of lattice size of electrode phases during charge that results in cracking of the Li2MnO3·LiMO2 electrode particle, with the extent of cracking correlated to the magnitude of the size change, crack healing is possible in the reverse solid-solution reaction occurring during discharge. Importantly, it is the phase separation during the two-phase reaction of the LiMO2 phase that prevents the complete healing of the electrode particle, leading to pulverization over extended cycling. This work points to the minimization of behavior leading to phase separation, such as two-phase and oxygen evolution, as a key strategy in preventing capacity fade of the electrode.

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Section: Resultssupporting

confidence: 80%

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

et al. 2016

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“…In the literature, particularly if we consider electrochemically prepared Li 4+ x Ti 5 O 12 , there is ongoing discussion about the question whether a solid-solution is formed during Li insertion or a so-called two-phase system is generated. ,,,− The latter means the formation of Li rich rock-salt type regions (Li 7 Ti 5 O 12 ) embedded or present in the grain boundary regions in Li poor spinel-type Li 4 Ti 5 O 12 . If we remember that Li 4 Ti 5 O 12 is a rather poor ionic (and electronic) conductor, the presence of better conducting and sufficiently large regions of Li 7 Ti 5 O 12 within a sample of the overall composition Li 4.1 Ti 5 O 12 should result in a 6 Li MAS NMR spectrum resembling that of Li 4 Ti 5 O 12 with a broad 8a NMR line and a narrower NMR line with a much smaller area fraction representing the Li 7 Ti 5 O 12 phase. , We have to keep in mind that the maximum Li ion diffusivity is found at x = 0.3... x = 1.0 while for larger values of x (e.g., x = 2) ion dynamics slows down once again. , …”

Section: Resultsmentioning

confidence: 99%

Discriminating the Mobile Ions from the Immobile Ones in Li_4+xTi₅O₁₂: ⁶Li NMR Reveals the Main Li⁺ Diffusion Pathway and Proposes a Refined Lithiation Mechanism

Schmidt

Wilkening

2016

J. Phys. Chem. C

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One of the most widely known anode materials with excellent cycling performance in lithium-ion batteries is zero-strain lithium titanate Li4Ti5O12 (LTO). This is based on the highly reversible insertion and deinsertion of Li ions varying the composition of Li4+x Ti5O12 from x = 0 to x = 3. The facile incorporation of Li is tightly connected with bulk Li ion dynamics. Although macroscopic electrochemical properties have been studied in great detail, bulk Li ion diffusion pathways have rarely been probed experimentally from an atomic scale point of view. Here, we evaluated 1D and 2D 6Li magic angle spinning (MAS) NMR spectra recorded as a function of x to make the local magnetic changes during Li insertion visible. This enabled us to directly show that rapid Li exchange involves the 8a and 16c sites, forming a 3D network throughout the LTO spinel structure. In contrast, considering the time scale set by our NMR experiments, the Li ions residing on the mixed occupied octahedral positions 16d are quite immobile. Under the MAS conditions applied, they definitely do not participate in rapid Li self-diffusion as evidenced by rather long site-specific longitudinal relaxation times as well as the absence of any NMR coalescence effects. Based on the NMR spectra, we propose a refined Li insertion mechanism which includes the initial formation of a highly conducting quasi solid solution characterized by rapid Li ion exchange.

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“…In the asassembled battery (Figure 6a), the LTO 222 reflection exhibits the largest change of 0.04(2)°, and revealing an initial shift to smaller angles as a consequence of lithium occupation at the 32e site during initial lithiation as shown previously. 9,33,34 In terms of LTO structure, the overall change in the positional parameter (x = y = z) of the oxygen atom is the same between the as-assembled and cycled batteries (Figure S5) As the latter lattice is only slightly smaller than the former, 36,37 the separation of these phases (< 0.04°) is not possible at the resolution of the data (FWHM ~ 0.8°). Therefore, the LTO phase transition is modelled as a single-phase (solid-solution reaction) after Wagemaker et al, 38 the details of which are presented in Table S1.…”

Section: Resultsmentioning

confidence: 94%

“…By comparison, there is a relatively-large change in intensity of this reflection, consistent with the changing population of lithium at the 16c crystallographic site. 33,34 The structural behaviour of the positive electrode are captured in the NPD data by changes in the LNMO 222 reflection intensity and position, with this analysis being complicated by its overlap with the Al 111 reflection. Both the intensity and position of the LNMO 222 reflection change significantly during the NPD experiment for both batteries.…”

Section: Resultsmentioning

confidence: 99%

Crystallographic origin of cycle decay of the high-voltage LiNi_0.5Mn_1.5O₄ spinel lithium-ion battery electrode

Pang

Liu

et al. 2016

Phys. Chem. Chem. Phys.

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Electronic Supplementary Information (ESI) available: X-ray and neutron powder diffraction data of LNMO powders used to make the electrodes for the 18650 batteries ( Figure S1); charge-discharge history of cycled battery ( Figure S2); Rietveld refinement profile using NPD data of the as-assembled battery ( Figure S3); results of single-peak fitting of the LNMO 222 reflection in the NPD data ( Figure S4); the variation of the oxygen positional parameter of the LTO phase ( Figure S5); crystal structure of the LTO and LNMO powders used in the sequential refinement (Table S1) High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is considered a potential high-power-density positive electrode for lithium-ion batteries, however, it suffers from capacity decay after extended charge-discharge cycling, severely hindering commercial application. Capacity fade is thought to occur through the significant volume change of the LNMO electrode occurring on cycling, and in this work we use operando neutron powder diffraction to compare the structural evolution of the LNMO electrode in an as-assembled 18650-type battery containing a Li4Ti5O12 negative electrode with that in an identical battery following 1000 cycles at high-current. We reveal that the capacity reduction in the battery post cycling is directly proportional to the reduction in the maximum change of the LNMO lattice parameter during its evolution. This is correlated to a corresponding reduction in the MnO6 octahedral distortion in the spinel structure in the cycled battery. Further, we find that the rate of lattice evolution, which reflects the rate of lithium insertion and removal, is ~ 9 and ~ 10% slower in the cycled than in the as-assembled battery during the Ni 2+ /Ni 3+ and Ni 3+ /Ni 4+ transitions, respectively.

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Structure of the Li₄Ti₅O₁₂ anode during charge-discharge cycling

Cited by 14 publications

References 15 publications

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

Discriminating the Mobile Ions from the Immobile Ones in Li_4+xTi₅O₁₂: ⁶Li NMR Reveals the Main Li⁺ Diffusion Pathway and Proposes a Refined Lithiation Mechanism

Crystallographic origin of cycle decay of the high-voltage LiNi_0.5Mn_1.5O₄ spinel lithium-ion battery electrode

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Structure of the Li4Ti5O12 anode during charge-discharge cycling

Cited by 14 publications

References 15 publications

The Origin of Capacity Fade in the Li2MnO3·LiMO2 (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

The Origin of Capacity Fade in the Li2MnO3·LiMO2 (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

Discriminating the Mobile Ions from the Immobile Ones in Li4+xTi5O12: 6Li NMR Reveals the Main Li+ Diffusion Pathway and Proposes a Refined Lithiation Mechanism

Crystallographic origin of cycle decay of the high-voltage LiNi0.5Mn1.5O4 spinel lithium-ion battery electrode

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Structure of the Li₄Ti₅O₁₂ anode during charge-discharge cycling

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

The Origin of Capacity Fade in the Li₂MnO₃·LiMO₂ (M = Li, Ni, Co, Mn) Microsphere Positive Electrode: An Operando Neutron Diffraction and Transmission X-ray Microscopy Study

Discriminating the Mobile Ions from the Immobile Ones in Li_4+xTi₅O₁₂: ⁶Li NMR Reveals the Main Li⁺ Diffusion Pathway and Proposes a Refined Lithiation Mechanism

Crystallographic origin of cycle decay of the high-voltage LiNi_0.5Mn_1.5O₄ spinel lithium-ion battery electrode