Effects of fluorination on the structure, magnetic and electrochemical properties of the P2-type NaxCoO2 powder
TL;DR: In this article, the effects of fluorination on the crystal structure, magnetic, and electrochemical properties of the P2-type NaxCoO2 powder were investigated for the first time.
About: This article is published in Journal of Alloys and Compounds.The article was published on 2019-02-05 and is currently open access. It has received 15 citations till now. The article focuses on the topics: Rietveld refinement & Fluorine.
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28,685 citations
TL;DR: In this paper, the structural, magnetic, transport, and electronic properties of LaCoO3 with Sr/Nb cosubstitution were studied using X-ray and neutron diffraction, dc-and ac-magnetiza...
Abstract: We study the structural, magnetic, transport, and electronic properties of LaCoO3 with Sr/Nb cosubstitution, i.e., La(1–2x)Sr2xCo(1–x)NbxO3 using X-ray and neutron diffraction, dc- and ac-magnetiza...
20 citations
TL;DR: In this paper, a review of the recent advances in sample digestion methods, especially on open-vessel acid digestion, microwave digestion, alkali fusion, high-pressure asher, and sample preparation methods for laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis, is presented.
20 citations
TL;DR: In this paper, the authors used molybdenum doping strategy to synthesize P2-type Na0.59Co0.20Mn 0.77Mo0.03O2 material with a hexagonal layer structure as the cathode of sodium-ion batteries through a solid-state reaction route.
Abstract: Layered P2-type Mn-based material is considered as one of the most promising cathode materials for sodium-ion batteries, but its unsatisfactory cyclic performance is one of the problems that need to be overcome. Here, we used molybdenum doping strategy to synthesize P2-type Na0.59Co0.20Mn0.77Mo0.03O2 material with a hexagonal layer structure as the cathode of sodium-ion batteries through a solid-state reaction route. The maximum discharge capacity of the Mo-doped cathode is 131.9 mAh g−1 with the capacity retention rate of 91.51% after 100 cycles at 0.1 C (1 C = 156 mAh g−1). Optimized Mo doping effectively decreases the charge transfer resistance and the interface resistance of the Na0.59Co0.20Mn0.80O2 cathode at open circuit and after 100 cycles, respectively, and the growth trends of the charge transfer resistance and the interface resistance are obviously slowed down, which is proved that the cycling stability of the pristine cathode is significantly improved by Mo doping. The main reasons are as follows: (1) Mo doping expands the a-axis and shortens the TM–O bond, which enhances the structural stability of the P2-type oxide; (2) Mo doping increases the crystallinity of the pristine and decreases the degree of cation disorder in the P2-type oxide; (3) the bond energy of Mo–O is stronger than that of Mn–O and Co–O, resulting in a more stable structure of the material. The results provide a meaningful reference for improving the cycle stability and kinetic performance of P2-type cathode materials for sodium-ion batteries.
12 citations
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TL;DR: In this paper, two distinct phases of Na x CoO 2 in the large Na-doping region (x ⩾ 0.75 ) were observed: a pure phase H 2 and a mixed-phase H 2 + H 3.
Abstract: We observe two distinct phases of Na x CoO 2 in the large Na-doping region ( x ⩾ 0.75 ), a pure phase H 2 , and a mixed phase H 2 + H 3 . The H 2 phase is characterized by a steep increase of the Peltier conductivity α defined as J = α ( - ∇ T ) , where J the thermoelectric current driven by the temperature gradient - ∇ T . The mixed-phase state H 2 + H 3 exhibits an unusual layered phase separation with conducting layers existing in parallel with insulating ones. At the critical doping x p ∼ 0.85 , the figure-of-merit Z at 80 K is 40 times larger than that of the as-grown sample ( x ∼ 0.7 ). The Hall coefficient and magnetoresistance are also reported.
18 citations
TL;DR: In this article, LiCoMnO4-yFy (y = 0, 0.05 and 0.1) compounds were synthesized by a two-step solid-state reaction at 800°C.
18 citations
TL;DR: In this article, the effects of partial substitution of Bi for Na and/or Mn for Co on the thermoelectric properties of polycrystalline Na 0.81 CoO 2 have been systematically investigated.
15 citations
TL;DR: In this paper, a new low-temperature fluorination procedure involving HF vapors from NH 4 HF 2 was proposed, which is capable of both fluorinating and fluorine doping.
Abstract: The compounds Sr 2 CuO 2 F 2+ x , Sr 2 CuO 2 Cl 2 :F, YBa 2 Cu 3 O 7 :F, YBa 2 Cu 4 O 8 :F have been synthesized by a new, low temperature fluorination procedure involving HF vapors from NH 4 HF 2 . We find the new approach is safer than using F 2 gas and is capable of both fluorinating and fluorine doping. We find a superconducting signature in several compounds of the series Sr 2 CuO 2 F 2+ x but find no evidence that the fluorinated phase is responsible for the superconductivity. There is evidence that the doping with fluorine of the Sr 2 CuO 2 Cl 2 crystal ( T N = 257 K) suppresses the antiferromagnetic ordering. YBa 2 Cu 3 O 7 :F and YBa 2 Cu 4 O 8 :F show no change in T c and a decrease in the Meissner and shielding fractions relative to the undoped samples. We report the results of our X-ray powder diffraction, thermogravimetric, 19 F NMR, and magnetization analyses of these compounds.
8 citations
"Effects of fluorination on the stru..." refers methods in this paper
...Another approach was also tested: the fluorination of the previously synthesized NaxCoO2 with NH4HF2 as a fluorination agent – a method standardly used for the fluorination of Sr2CuO3 [28] and rare-earth oxides [29,30]....
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...[28] B.N. Wani, L.L. Miller, B.J. Suh, F. Borsa, Fluorination of Sr2CuO3 and high temperature superconducting oxides, Phys....
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TL;DR: In this article, measurements of the magnetic susceptibility χ (T ) and 23 Na nuclear magnetic resonance (NMR) on polycrystalline samples of Na07CoO2 were reported.
Abstract: We report on measurements of the magnetic susceptibility χ ( T ) and 23 Na nuclear magnetic resonance (NMR) on polycrystalline samples of Na07CoO2 The χ ( T ) data suggest that for T > 75 K , the Co ions adopt an effective configuration of Co 34 + The temperature evolution of 2D exchange 23 Na -NMR spectra and of the 23 Na spin-lattice relaxation time T 1 reveal significant anomalies between 230 and 300 K These features provide evidence for a crossover phenomenon or a phase transition and suggest that, upon decreasing temperature, a dramatic change occurs in the Co 3d–electron spin dynamics, starting just below 300 K and being completed at 230 K This phenomenom may involve a partial charge ordering within the Co subsystem
5 citations