Supertransferred Hyperfine Fields at7Li:  Variable Temperature7Li NMR Studies of LiMn2O4-Based Spinels

Gee, Becky; Horne, Craig R.; Cairns, Elton J.; Reimer, Jeffrey A.

doi:10.1021/jp982301p

Cited by 77 publications

(119 citation statements)

References 33 publications

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“…Gee et al 41 have recently presented data based on NMR data that suggests an increase in covalent or metallic bonding may play a significant role in suppressing the Jahn-Teller distortion in LiMn 2 O 4 oxides. Covalency of a transition metal-oxygen bond typically increases as the lattice parameter shrinks.…”

Section: Discussionmentioning

confidence: 99%

Failure Mechanism and Improvement of the Elevated Temperature Cycling of LiMn[sub 2]O[sub 4] Compounds Through the Use of the LiAl[sub x]Mn[sub 2−x]O[sub 4−z]F[sub z] Solid Solution

Amatucci¹,

Pereira

Zheng³

et al. 2001

J. Electrochem. Soc.

216

117

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Physiochemical and electrochemical means were used to characterize the failure mechanisms of the lithium manganese oxide based solid solutions utilized as positive electrodes for Li batteries. Resultant data supports a theory in which the 22 and 55°C failure mechanisms are one in the same. The poor performance is exacerbated during cycling due to a mechanism linked to the symbiotic relationship between physical destruction induced by a surface Jahn-Teller distortion and the classic failure mechanisms presented for the chemical failure of the spinel at elevated temperature storage. Based on these findings, a spinel, LiAl x Mn 2Ϫx O 4Ϫz F z , was fabricated which exhibits enhanced stability at elevated temperature.During the past decade, rechargeable lithium batteries have undergone a period of intense commercialization due to their intrinsically superior energy density over other rechargeable battery technologies such as nickel metal hydride. The overwhelming majority of the cells utilize electrochemical couples consisting of negative electrodes of carbonaceous products, typically graphite, and positive electrodes of the layered LiCoO 2 . 1,2 Recent focus on larger rechargeable battery applications such as electric scooters, electric motorcycles, and electric cars has intensified the search for lower cost, safer, and less toxic cathode materials than LiCoO 2 . To address these issues, much research has focused recently on the development of LiMn 2 O 4 spinel based positive electrodes suitable for use in commercial Li-ion cells. [3][4][5] Unlike the layered LiCoO 2 , LiMn 2 O 4 crystallizes in the spinel Fd3m space group. Li ions occupy tetrahedral 8a sites while the manganese cations and oxygen anions occupy the octahedral 16d and 32e sites, respectively. Lithium ions exhibit relatively quick diffusion through a pathway consisting of 8a and 16c sites. 5 Early in its introduction as a positive electrode material, room-temperature cycling lifetime was poor. This problem was solved for the most part with the realization that monovalent, divalent, and trivalent metal substitution for the manganese cation ((Li) 8a ͓Me x Mn 2Ϫx ͔ 16d O 4 ) improved room-temperature cycling performance significantly. 6-12 The improvement was based on the increase of the manganese average oxidation state with the formation of these solid solutions.Nominal spinel of Li 1 Mn 2 O 4 has a composition consisting of 50% Mn 3ϩ and 50% Mn 4ϩ . High spin Mn 3ϩ is a Jahn-Teller cation. When additional Li ions are intercalated into the octahedral 16c sites of the Li 1 Mn 2 O 4 spinel (Li 1ϩx Mn 2 O 4 ), the average oxidation state of the manganese cations becomes lower than 3.5. This results in the onset of a cooperative Jahn-Teller distortion, increasing the c/a ratio by 16%. The presence of Li ions on the 16c sites also induces neighboring Li ions currently existing on the tetrahedral 8a sites to displace onto the 16c sites. The formation of Li 1ϩx Mn 2 O 4 is a twophase front reaction consisting of Li 1 Mn 2 O 4 and the Jahn-Teller distorted (F4 ...

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Section: Discussionmentioning

confidence: 99%

Failure Mechanism and Improvement of the Elevated Temperature Cycling of LiMn[sub 2]O[sub 4] Compounds Through the Use of the LiAl[sub x]Mn[sub 2−x]O[sub 4−z]F[sub z] Solid Solution

Amatucci¹,

Pereira

Zheng³

et al. 2001

J. Electrochem. Soc.

216

117

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“…1 However, muon spin relaxation (µSR) has been suggested recently as an alternative means of studying Li + transport in these circumstances. [2][3][4] In µSR experiments 100% spin polarized muons are implanted into materials where they thermalize, allowing the measurement of local magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Insight into lithium transport in lithium nitridometallate battery materials from muon spin relaxation

Powell

Stoeva

Lord

et al. 2013

Phys. Chem. Chem. Phys.

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A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk in a more open pathway for Li + diffusion. However, an optimal value of x is found with a ≈ 3.69 Å after which the concomitant contraction in layer spacing reduces the polarizability of the lattice framework.2

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“…The forgoing of the literatures survey indicates that the cerium phosphates can be used in different industrial and environmental applications such as a potential storage material for nuclear waste [7], a poison to automobile catalyst [8][9][10][11][12], and potential proton conduction membrane for the hydrogen fuel cell [13]. More recently, some studies were done to introduce cerium phosphate in the optical field [14,15].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and microstructure studies of nano-sized cerium phosphates

et al. 2010

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KEYWORDSCerium phosphate, CePO4, nanoparticles with hexagonal or monoclinic phase was synthesized by the reaction between Ce(SO4)2.4H2O and two different phosphate sources, H3PO4 and Na2HPO4. The obtained gel was dried and calcined at different temperatures (200, 400, and 800 о C). The effects of the precursor materials and the calcination temperatures on the produced phases were studied. Both X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to follow the changes in the phase structure for the produced samples. The thermal behaviour of the as prepared samples was studied by using differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA). The morphology, crystallinity and particle size of the produced samples as prepared and calcinated were characterized by transmission electron microscope (TEM). The analysis of TEM results indicated that CePO4 was prepared in nano-sized particles.Cerium phosphate Synthesis X-ray diffraction IR DSC/TGA TEM

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Supertransferred Hyperfine Fields at⁷Li: Variable Temperature⁷Li NMR Studies of LiMn₂O₄-Based Spinels

Cited by 77 publications

References 33 publications

Failure Mechanism and Improvement of the Elevated Temperature Cycling of LiMn[sub 2]O[sub 4] Compounds Through the Use of the LiAl[sub x]Mn[sub 2−x]O[sub 4−z]F[sub z] Solid Solution

Failure Mechanism and Improvement of the Elevated Temperature Cycling of LiMn[sub 2]O[sub 4] Compounds Through the Use of the LiAl[sub x]Mn[sub 2−x]O[sub 4−z]F[sub z] Solid Solution

Insight into lithium transport in lithium nitridometallate battery materials from muon spin relaxation

Synthesis and microstructure studies of nano-sized cerium phosphates

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