Crystal and magnetic structures of electrochemically delithiated Li1−xCoPO4 phases

Ehrenberg, Helmut; Bramnik, Natalia N.; Senyshyn, Anatoliy; Fueß, H.

doi:10.1016/j.solidstatesciences.2008.04.017

Cited by 94 publications

(96 citation statements)

References 18 publications

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“…These two plateaus were already proposed as two two-phase reactions of LiCoPO 4 /Li 0.6 CoPO 4 and Li 0.6 CoPO 4 /CoPO 4 . 38 It was seen that the initial charge capacity was slightly higher than the theoretically expected value. The excess capacity may be related to the electrolyte decomposition, as previously reported in many papers, and but its amount was not remarkable.…”

Section: Resultsmentioning

confidence: 83%

“…23 However, this LiFePO 4 cathode is not suitable to attain the highenergy density batteries described above, because its voltage is insufficiently high. Many studies have been carried out on other olivine compounds such as LiMnPO 4 [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] and its utilization enables us to attain highenergy density batteries. Many strategies for the LiCoPO 4 cathode, similar to those of the LiFePO 4 cathode, have been proposed, because they present common problems that hinder their practical application: particle fining, [39][40][41] carbon coating of the particle surface, [42][43][44][45][46] and the cation substitution.…”

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confidence: 99%

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Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Hanafusa

Oka

Nakamura

2014

J. Electrochem. Soc.

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Li-deficient olivine compounds, Li 1-x Co 1-x Fe x PO 4 (x < 0.15), were prepared by calcination of the sol-gel derived precursors in ambient atmosphere. They were almost single phase at x < 0.10 but some impurity phases were found at x > 0.10. The lattice parameters changed continuously with an increase in the Fe substitution. Their variation in the range of x < 0.10 roughly obeyed Vergard's law. From the 57 Fe Mössbauer spectrum at room temperature, it was shown that the introduced Fe took a trivalent highspin state in the olivine lattice. The temperature-dependent magnetic susceptibility exhibited that the Fe incorporation enhanced the antiferromagnetic ordering: the Neel temperature shifted higher. Furthermore, the electrochemical performances, such as cycling stability and rate capability, were improved significantly with an appropriate substitution (about 10%) with Fe 3+ . Consequently, the Fe 3+ incorporated compounds with Li deficiency as the charge compensation are thought to be good candidates as high-voltage cathode material, which may enhance the energy density of Li ion battery.

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Section: Resultsmentioning

confidence: 83%

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confidence: 99%

Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Hanafusa

Oka

Nakamura

2014

J. Electrochem. Soc.

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“…23,37 However, no clear explanation for the intermediate Li x CoPO 4 phase appearance has been presented, and the phase is suggested to be at least metastable. 35 In literature, many studies report two oxidation peaks/charge plateaus for LiCoPO 4 , 19,21,23-25,27,33,38 consistent with the reaction mechanism of two two-phase reactions, but some results indicate a one-step process. 18,[28][29][30] However, the two-step mechanism seems to be less apparent during reduction/discharge.…”

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confidence: 86%

“…34 Furthermore, the fully-delithiated CoPO 4 phase is unstable in air and undergoes amorphization. 21 Unlike the one-step, two-phase reaction mechanism of LiFePO 4 , the delithiation/lithiation reaction of LiCoPO 4 proceeds in two steps, consisting of two two-phase regions, LiCoPO 4 ↔Li x CoPO 4 and Li x CoPO 4 ↔CoPO 4 , 21 the intermediate phase composition being found at x = 0.7 21,35 or x = 2/3, 23 although x = 0.2 -0.45 has been suggested as well. 36 Possibly a narrow single-phase solid-solution region exists in the beginning of lithium extraction/end of lithium insertion.…”

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confidence: 99%

Electrochemical Performance and Delithiation/Lithiation Characteristics of Mixed LiFe_1-_yM_yPO₄(M= Co, Ni) Electrode Materials

Jalkanen

Karppinen

2015

J. Electrochem. Soc.

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Solid solutions of LiFe 1-y M y PO 4 /C (M = Co, Ni) within the whole substitution range (0 ≤ y ≤ 1) are systematically investigated as safe high-voltage positive electrode materials for Li-ion battery. Especially the similarities and differences between the Co-and Ni-substitution schemes are highlighted. With increasing substitution level y, the orthorhombic unit cell shrinks and the Li + -ion diffusion channel area decreases, more rapidly for the smaller-sized Ni substituent. While the Co 2+ /Co 3+ redox couple shows reversible electrochemical activity, only an initial, partial delithiation is achieved for the Ni 2+ /Ni 3+ couple at all y. However, both substitution schemes similarly affect the Fe 2+ /Fe 3+ redox couple by increasing its potential and enhancing the kinetics. Particularly, a mutual influence of Fe and Co/Ni on the delithation/lithiation characteristics is proposed: ex situ XRD analysis shows signs of a phase-composition change in the Fe 2+ /Fe 3+ region for higher y, and correspondingly, a changed Co 2+ /Co 3+ redox mechanism for lower y is indicated by cyclic voltammetry. We suggest that this behavior is related to a substitution-induced decrease in the volume change between the lithiated and delithiated phases. For the Co-substitution scheme, a composition around y ≈ 0.5 seems optimal for combining a high energy density and a kinetically beneficial, diffusional single-phase delithiation/lithiation mechanism. Li-ion batteries have been traditionally used for small, portable consumer electronics, but their utilization in large-scale applications is rapidly growing. As the size of the battery packs is increasing, the matters of safety, cost, and cycle-life become more crucial. In addition, for applications in transportation, high energy and power densities are demanded. Olivine-structured metal phosphates LiMPO 4 (M = Fe, Mn, Co, Ni) are an interesting material family to replace the layered metal oxides LiMO 2 as the positive electrode.1-4 Their safety owing to their intrinsic structural stability is very tempting for large-scale batteries. The orthorhombic olivine structure (space group Pnma) is composed of LiO 6 and MO 6 octahedra and PO 4 tetrahedra, such that Li + -ion diffusion during lithiation/delithiation takes place only in one dimension, along the b axis. 3,5The iron-based olivine LiFePO 4 is already commercially used in Li-ion batteries; it shows a theoretical capacity of 170 mAh g −1 , high safety and cycle stability, and is in addition cheap and environmentally friendly.1 The delithiation/lithiation (charge/discharge) reaction proceeds as a two-phase reaction with a varying LiFePO 4 /FePO 4 ratio, which brings about a kinetic limitation due to the single Fe valence (Fe 2+ or Fe 3+ ) in the two end-phases, resulting in low carrier density. 1,6 Additionally, the two-phase reaction pathway is restricted by nucleation and growth, when compared to a diffusional single-phase solidsolution mechanism. 7 However, narrow single-phase solid-solution regions are suggested to exist at room-tem...

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“…However, after the refinement the occupancy factors of Li at 4a and Co at 4c tend to 1 (within the experimental error). For LiCoPO 4 On the basis of the Rietveld refinement of neutron and Xray powder diffraction, Ehrenberg et al [31] reported a Li deficiency at 4a site (92 % occupancy) for LiCoPO 4 obtained by the citric-assisted Pechini method at 600°C. We have also tested a Li deficiency at 4a, but the refinement results rejected this possibility: for LiCoPO 4 annealed at 450°C R b is 4.06 for 4a site occupancy of 0.980 Ϯ 0.020; for LiCoPO 4 annealed at 500°C R b is 3.53 for 4a site occupancy of 1.010 Ϯ 0.010; for LiCoPO 4 annealed at 600°C R b is 5.39 for 4a site occupancy of 1.020 Ϯ 0.020.…”

Section: Resultsmentioning

confidence: 99%

Ordered Olivine‐Type Lithium–Cobalt and Lithium–Nickel Phosphates Prepared by a New Precursor Method

2010

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Keywords: Lithium / Cobalt / Nickel / Organic-inorganic hybrid composites / X-ray diffraction Single phases of olivine-type LiCoPO 4 and LiNiPO 4 were synthesized by thermal treatment of homogeneous lithiummetal-phosphate-formate precursors obtained by freeze drying of aqueous solutions of the corresponding metal formates and LiH 2 PO 4 . The structure, thermal behavior, and morphology of the precursors were studied by IR spectroscopy, DTA, and SEM. Cobalt and nickel phosphate-formate precursors have a composition LiMH x (PO 4 )(HCOO) x ·yH 2 O, where the formate and phosphate groups are mainly deprotonated. For the Co precursor the formate and phosphates ions are randomly coordinated to both Co and Li cations, whereas for the Ni precursor there is a preferential coordina-

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Crystal and magnetic structures of electrochemically delithiated Li1−xCoPO4 phases

Cited by 94 publications

References 18 publications

Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Electrochemical Performance and Delithiation/Lithiation Characteristics of Mixed LiFe_1-_yM_yPO₄(M= Co, Ni) Electrode Materials

Ordered Olivine‐Type Lithium–Cobalt and Lithium–Nickel Phosphates Prepared by a New Precursor Method

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Crystal and magnetic structures of electrochemically delithiated Li1−xCoPO4 phases

Cited by 94 publications

References 18 publications

Electrochemical and Magnetic Studies of Li-Deficient Li1-xCo1-xFexPO4Olivine Cathode Compounds

Electrochemical and Magnetic Studies of Li-Deficient Li1-xCo1-xFexPO4Olivine Cathode Compounds

Electrochemical Performance and Delithiation/Lithiation Characteristics of Mixed LiFe1-yMyPO4(M= Co, Ni) Electrode Materials

Ordered Olivine‐Type Lithium–Cobalt and Lithium–Nickel Phosphates Prepared by a New Precursor Method

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Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Electrochemical and Magnetic Studies of Li-Deficient Li_1-xCo_1-xFe_xPO₄Olivine Cathode Compounds

Electrochemical Performance and Delithiation/Lithiation Characteristics of Mixed LiFe_1-_yM_yPO₄(M= Co, Ni) Electrode Materials