Solvothermal synthesis of electroactive lithium iron tavorites and structure of Li2FePO4F

Ellis, Brian L.; Ramesh, T. N.; Rowan-Weetaluktuk, W. N.; Ryan, D. H.; Nazar, Linda F.

doi:10.1039/c2jm15273h

Cited by 53 publications

(76 citation statements)

References 33 publications

(55 reference statements)

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“…The Tavorite-type LiFePO 4 F exhibits a complex single phase regime followed by a two-phase plateau at 2.75 V on electrochemical lithium insertion, as reported by Ellis et al [78]. The monoclinic LiFeSO 4 F has a triplite like structure in which Li + /Fe 2+ is fully mixing, and two-phase reaction mechanism is verified by a flat plateau of about 3.9 V. As reported by Dong et al [79].…”

Section: Other Two-phase Li-intercalation Compoundssupporting

confidence: 51%

Two-phase transition of Li-intercalation compounds in Li-ion batteries

2014

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Among all electrode materials, olivine LiFePO 4 and spinel Li 4 Ti 5 O 12 are well-known for their two-phase structure, characterized by a flat voltage plateau. The phase transition in olivine LiFePO 4 may be modeled in single particle and many-particle systems at room temperature, based on the thermodynamic phase diagram which is easily affected by coherency strain and the size effect. Some metastable and transient phases in the phase diagram can also be detected during non-equilibrium electrochemical processes. In comparison to olivine LiFePO 4 , spinel Li 4 Ti 5 O 12 possesses a 'zero strain' property and performs Li-site switching during the phase transition, which lead to a different phase structure. Here, the phase transitions of olivine LiFePO 4 and spinel Li 4 Ti 5 O 12 are systematically reviewed, and the concepts discussed may be extended to other two-phase Li-intercalation compounds in Li-ion batteries.

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Section: Other Two-phase Li-intercalation Compoundssupporting

confidence: 51%

Two-phase transition of Li-intercalation compounds in Li-ion batteries

2014

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“…It also differs from LiFePO 4 OH where only LiFePO 4 OH is seen in the diffraction pattern on partial reduction as the fully reduced phase (Li 2 FePO 4 OH) is amorphous. 19 Clearly, tavorite Li 1.5 FePO 4 F 0.6 (OH) 0.4 is single phase owing to the OH − /F − anionic disorder. Full reduction to Li 2 FePO 4 F 0.6 (OH) 0.4 shows further shift of the peaks to higher d-spacings.…”

Section: Chemistry Of Materialsmentioning

confidence: 99%

“…In the case of LiFePO 4 F, complete F − substitution gives rise to the lowest unit cell volume of 173.67 Å 3 , 5 as compared to 174.84 Å 3 for LiFePO 4 OH. 19 The unit cell volume of LiFePO 4 (OH) 0.4 F 0.6 (174.31 Å 3 ) is intermediate between that of LiFePO 4 OH and LiFePO 4 F, as expected for the mixed OH/F compound.…”

mentioning

confidence: 90%

Anion-Induced Solid Solution Electrochemical Behavior in Iron Tavorite Phosphates

Ellis

Nazar

2012

Chem. Mater.

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C athode materials for lithium ion batteries which exhibit solid solution properties over a wide lithium compositional range have been sought after for decades. Solid solution behavior is exhibited in several oxide-based positive electrode materials, Li 1−x MO 2 , where it is typically attributed to delocalized and/or weakly correlated ion and electron transport, coupled with a small volume difference between the redox end members. 1,2 Its existence implies an absence of any phase boundary impediment during redox cycling and is associated with good carrier mobility. The existence of a single phase extraction/insertion mechanism allows for additional practical benefits. Chiefly, the resultant sloping voltage curve permits facile monitoring of the state of charge of the battery, as compared with materials which exhibit two-phase behavior and display a constant voltage over a range of compositions: classic examples of these are members of the lithium metal polyanion family such as LiFePO 4 , which has a flat voltage profile near 3.5 V vs Li/Li + . 3,4 With the advent of LiFePO 4 , polyanionic materials have been a major focus of research for reasons of high safety, low cost, and environmental impact. Other positive electrode materials under study include fluorophosphates such as LiFePO 4 F, 5,6 LiVPO 4 F, 7 and Na 2 FePO 4 F. 8 More recently, sulfates such as LiFeSO 4 F 9,10 and FeSO 4 (OH) 11 have emerged.While Na 2 FePO 4 F/Li exhibits solid-solution behavior as a result of Na/Li cation disorder, 12 it is something of an exception. Solid solutions previously reported for polyanionic lithium ion battery systems have mostly been limited to aliovalent cation substitution generated in situ via redox transitions. These include substitution of Mn 2+ in Li(Fe,Mn)-PO 4 in a disordered state which is maintained during the Fe 2+/3+ phase transition in LiFePO 4 and gives rise to apparent solid solution behavior on the lower voltage plateau in the electrochemical profile. 13 Aliovalent cation distributions have been demonstrated to drive solution solution behavior in Li 3−x V 2 (PO 4 ) 3 where cation valent disorder dominates on discharge: in contrast, that same valence order on charge drives single phase behavior. 14 Solid solutions have also been observed in elevated temperature regimes of Li 1−x FePO 4 , characterized by coalescence of the two end-members and rapid electronhopping. 15 Particle size effects have also been suggested to induce solid solution behavior. In LiFePO 4 , particles less than 100 nm in diameter were shown to have a smaller miscibility gap than bulk particles. 4,16 These findings have prompted us to explore the next generation of cathode materials that might exhibit more attractive features with fewer inherent limitations. In the search for structural frameworks that overcome the 1-D ion conductivity challenge of olivine, 17 we explored the tavorite family of compounds: LiMPO 4 (OH) x F 1−x (M = V, Mn, Fe, Al). It has been shown previously that anionic solid solutions LiAlPO 4 (OH) x F 1−x , which sp...

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“…It was presumed that this compound has a Ni 2+ /Ni 3+ redox couple above 5 V, because it did not show any electrochemical activity below 5 V, similar to that of other nickel phosphates such as LiNiPO 4 [74] and Li 2 NiPO 4 F [75]. Substitutional solid solutions such as Na 2 (Fe 1−x Mn x PO 4 )F (0 < x < 0.2) [76], Na 2 (Fe 1−x Co x )PO 4 F (0 < x < 1) and Na 2 (Fe 1−x Mg x )PO 4 F (x < 0.15) have also been prepared [77], but all presented minimal reversibility. Electrochemical performances of substituted samples decreased when the substitutional content was increased.…”

Section: Sodium Metal Fluorophosphatesmentioning

confidence: 99%

Electrode Materials for Sodium-Ion Batteries: Considerations on Crystal Structures and Sodium Storage Mechanisms

Wang

Shanmukaraj

et al. 2018

Electrochem. Energ. Rev.

258

122

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Sodium-ion batteries have been emerging as attractive technologies for large-scale electrical energy storage and conversion, owing to the natural abundance and low cost of sodium resources. However, the development of sodium-ion batteries faces tremendous challenges, which is mainly due to the difficulty to identify appropriate cathode materials and anode materials. In this review, the research progresses on cathode and anode materials for sodium-ion batteries are comprehensively reviewed. We focus on the structural considerations for cathode materials and sodium storage mechanisms for anode materials. With the worldwide effort, high-performance sodium-ion batteries will be fully developed for practical applications.

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Solvothermal synthesis of electroactive lithium iron tavorites and structure of Li2FePO4F

Cited by 53 publications

References 33 publications

Two-phase transition of Li-intercalation compounds in Li-ion batteries

Two-phase transition of Li-intercalation compounds in Li-ion batteries

Anion-Induced Solid Solution Electrochemical Behavior in Iron Tavorite Phosphates

Electrode Materials for Sodium-Ion Batteries: Considerations on Crystal Structures and Sodium Storage Mechanisms

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