Exploring the Peculiarities of LiFePO4 Hydrothermal Synthesis Using In Situ Calvet Calorimetry

Sharikov, F. Yu.; Drozhzhin, Oleg A.; Sumanov, Vasiliy D.; Баранов, А. Н.; Abakumov, Artem M.; Antipov, Evgeny V.

doi:10.1021/acs.cgd.7b01366

Cited by 11 publications

(10 citation statements)

References 21 publications

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“…17,18 The necessity of such studies is also preceded by the admirable electrochemical performance of olivine-type cathode materials (prepared by low-temperature methods such as hydrothermal processes) as well as by the significant amount of structural defects forming along these synthesis routes. 6,10,11,14 Lithium-rich (or lithium-excess) lithium iron phosphate (termed further as Li-rich LFP) as a novel generation of highperformance battery materials was introduced in a recent work of Park et al 17 It was shown that the presence of Li in Fe sites in Li 1+δ Fe 1−δ PO 4 (0 < δ < 0.05) decreases the first-order phase transition energy barrier, as well as Li + diffusion barriers along the [010] direction. 17,18 Besides this, the presence of Li − Fe defects energetically destabilizes the Fe + Li -related defects, thus improving Li + transport in the channels.…”

Section: ■ Introductionmentioning

confidence: 99%

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄

et al. 2019

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Li-rich lithium iron phosphate Li 1+δ Fe 1−δ PO 4 (Lirich LFP) prepared by the solvothermal method via the Li 3 PO 4 precursor demonstrates excellent electrochemical characteristics such as C-rate capability (140 mAh g −1 at 10 C charge for the Li 1.04 Fe 0.96 PO 4 /C material) and low voltage hysteresis between lithiation and delithiation (14 mV at C/300 rate for the same sample). Phase transformations and evolution of the Fe cations coordination environment during Li + (de)intercalation are studied in operando regime by means of synchrotron X-ray powder diffraction (SXPD) and 57 Fe Mossbauer spectroscopy (MS). The presence of a certain amount of Li + in the M2 position in the crystal structure of the as-prepared Li-rich LFPs leads to an additional component in the MS spectra corresponding to ferric ions in the M2 position with distorted second coordination sphere. Evolution of the MS spectra during charge/discharge reveals the clear relationship between the relative fraction of this component and the mechanism of Li + (de)intercalation. Extended single-phase regions with large Li + nonstoichiometry in the triphylite and heterosite phases of Li 1.04−x Fe 0.96 PO 4 observed by means of SXPD appear due to Li − Fe defects existing in the as-prepared Li-rich LFPs and acting as a "diluting" agent, which prevents two-phase transition. Increased thermodynamic stability of the intermediate Li 1+δ−x Fe 1−δ PO 4 solid solutions was also shown by DFT calculations. These features can be regarded as an additional merit of Li-rich LFPs, rendering them promising cathodes for high-power Li-ion batteries.

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Section: ■ Introductionmentioning

confidence: 99%

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄

et al. 2019

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Section: Na-bearing Triphylite-lithiophilite Structural Analogous and Their Derivatives As Promising Cathode Materialsmentioning

confidence: 96%

“…It was found that depending on the initial precursor concentration, the formation of this "antisite iron phosphate" and the reaction with Li + to produce the final LiFePO4 phase can take place as two consecutive stages or as merging of these two stages into one. The observed changes in the reaction mechanism result in profound difference in the unit cell parameters of the triphylite phase, particle morphology, and electrochemical properties of the obtained LiFePO4 samples [35]. According to [63], direct thermal oxidation of sarcopside, Fe3(PO4)2, above 450 °С, makes it possible to obtain heterosite, FePO4, according to the reaction Fe3(PO4)2 + ¾ O2 → 2 FePO4 + ½ Fe2O3, which leads to the extraction of iron from the sarcopside structure.…”

Section: Na-bearing Triphylite-lithiophilite Structural Analogous and Their Derivatives As Promising Cathode Materialsmentioning

confidence: 98%

“…It was found that Li-ion diffusion in LiFePO 4 is strongly anisotropic and occurs through a curved path along the {010} direction, and later on, Nishimura et al provided experimental evidence for this curved one-dimensional (1D) path for lithium motion [31][32][33]. These findings prompted the development of LiFePO 4 material with specific morphology, which was prepared by hydrothermal and solvothermal approaches [34,35].…”

Section: Lithiophilite−purpurite−niahite: Comparative Crystal Chemistry and Structure Transformationmentioning

confidence: 99%

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Mineral-Inspired Materials: Synthetic Phosphate Analogues for Battery Applications

2020

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For successful development of novel rechargeable batteries, considerable efforts should be devoted to identifying suitable cathode materials that will ensure a proper level of energy output, structural stability, and affordable cost. Among various compounds explored as electrode materials, structural analogues of minerals–natural stable inorganic solids–occupy a prominent place. The largest number of varieties of phosphate minerals occurs in rare metal granite pegmatites, and many of which contain transition metals as essential components. Transition metal phosphates are promising candidates for exploration as cathode materials due to a perfect combination of easily scalable synthesis, moderate-to-high voltage operation, thermal/chemical stability, and environmental safety. However, impurities usually presented in natural objects, and often inappropriate sample morphologies, do not permit the use of minerals as battery electrode materials. Nevertheless, the minerals of different classes, especially phosphates, are considered as prototypes for developing novel materials for battery applications. The crystal chemical peculiarities of the phosphate representatives that are most relevant in this aspect and the electrochemical characteristics of their synthetic analogues are discussed here.

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“…Recently, we demonstrated that the electrochemical capacity of the hydrothermally prepared LiFePO 4 drastically depends on the initial solution concentration. 35 To detect possible structural changes accompanying this dependence, we have performed Rietveld structure refinement from powder X-ray diffraction data of the samples prepared with various solution concentrations (see Table 1). The refinement of the occupancy factors for the M1, M2 and P positions have been performed with the full occupancy of the O1, O2 and O3 positions.…”

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confidence: 99%

“Hydrotriphylites” Li1-xFe1+x(PO4)1-y(OH)4y as Cathode Materials for Li-ion Batteries

Sumanov¹,

Aksyonov²,

Drozhzhin³

et al. 2019

Preprint

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Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) materials enabling the Li-ion battery technology for stationary energy storage applications, which are important for broad implementation of the renewable energy sources. Despite the apparent simplicity of its crystal structure and chemical composition, LiFePO4 is prone to off-stoichiometry and demonstrates rich defect chemistry owing to variations in the cation content and iron oxidation state, and to the redistribution of the cations and vacancies over two crystallographically distinct octahedral sites. The importance of the defects stems from their impact on the electrochemical performance, particularly on limiting the capacity and rate capability through blocking the Li ion diffusion along the channels of the olivine-type LiFePO4 structure. Up to now the polyanionic (i.e. phosphate) sublattice has been considered idle on this playground. Here, we demonstrate that under hydrothermal conditions up to 16% of the phosphate groups can be replaced with hydroxyl groups yielding the Li1-xFe1+x(PO4)1-y(OH)4y solid solutions, which we term “hydrotriphylites”. This substitution has tremendous effect on the chemical composition and crystal structure of the lithium iron phosphate causing abundant population of the Li-ion diffusion channels with the iron cations and off-center Li displacements due to their tighter bonding to oxygens. These perturbations trigger the formation of an acentric structure and increase the activation barriers for the Li-ion diffusion. The “hydrotriphylite”-type substitution also affects the magnetic properties by progressively lowering the Néel temperature. The off-stoichiometry caused by this substitution critically depends on the overall concentration of the precursors and reducing agent in the hydrothermal solutions, placing it among the most important parameters to control the chemical composition and defect concentration of the LiFePO4-based cathodes.

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Exploring the Peculiarities of LiFePO₄ Hydrothermal Synthesis Using In Situ Calvet Calorimetry

Cited by 11 publications

References 21 publications

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄

Mineral-Inspired Materials: Synthetic Phosphate Analogues for Battery Applications

“Hydrotriphylites” Li1-xFe1+x(PO4)1-y(OH)4y as Cathode Materials for Li-ion Batteries

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Exploring the Peculiarities of LiFePO4 Hydrothermal Synthesis Using In Situ Calvet Calorimetry

Cited by 11 publications

References 21 publications

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li1+δFe1−δPO4

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li1+δFe1−δPO4

Mineral-Inspired Materials: Synthetic Phosphate Analogues for Battery Applications

“Hydrotriphylites” Li1-xFe1+x(PO4)1-y(OH)4y as Cathode Materials for Li-ion Batteries

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Exploring the Peculiarities of LiFePO₄ Hydrothermal Synthesis Using In Situ Calvet Calorimetry

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄

Exploring the Origin of the Superior Electrochemical Performance of Hydrothermally Prepared Li-Rich Lithium Iron Phosphate Li_1+δFe_1−δPO₄