Cathode Material For Secondary Batteries Research Articles

Electronic conductivity of vanadium-tellurite glass-ceramics

In this paper, we investigate the electronic conductivity of 2TeO2–V2O5 glass-ceramics with crystallinity ranging from 0 to 100wt.%, i.e., from entirely amorphous to completely crystalline. The glass is prepared by the melt quenching technique, and the crystal is prepared by subsequent heat treatment thereof. Glass-ceramics are prepared by mixing glass and crystal powder, followed by a sintering procedure. Activation energies for electronic conduction in the glass and in the crystal are determined by fitting the Mott–Austin equation to the electronic conductivity data obtained by impedance spectroscopy. We find similar activation energies for both glass and crystal, implying that they have similar conduction mechanisms, i.e., thermally activated hopping. The electronic conductivity of 2TeO2–V2O5 glass is about one order of magnitude higher than that of the corresponding crystal, and a percolation phenomenon occurs at a glass fraction of 61wt.%, increasing from a lower conductivity in the crystal to a higher conductivity in the glass. We explain the behavior of electronic conduction in the 2TeO2–V2O5 glass-ceramics by considering constriction effects between particles as well as percolation theory. This work implies that, based on its electronic conductivity, vitreous 2TeO2–V2O5 is more suitable as a cathode material in secondary batteries compared to a 2TeO2–V2O5 glass-ceramic.

Synthesis and characterization of H2V3O8 nanorods for electrochemical devices

Vanadium oxide hydrate (H2V3O8) nanorods to be used as cathode material in secondary batteries were synthesized using a hydrothermal method without templates and reducing agents. The obtained pristine product was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Cyclic voltammetry and charge/discharge studies were conducted to examine the electrochemical performance of cathodes made of these vanadium oxide hydrate nanorods. The specific capacity of the vanadium oxide hydrate nanorods is 292 mAh/g, the columbic efficiency is about 95%. The calculated capacities are 42.8 F/g at 5 mV/s and 39.2 F/g at 10 mV/s scan rate.

Preparation of Li[Ni 1/3Co 1/3Mn 1/3]O 2 powders for cathode material in secondary battery by solid-state method

Employing Li 2CO 3, NiO, Co 3O 4, and MnCO 3 powders as starting materials, Li[Ni 1/3Co 1/3Mn 1/3] O 2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the synthesis process. After successive heat treatments at 650 and 950 °C, the prepared powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy, and transmission electron microscopy. The powders prepared by adding salt (NaCl) as grinding aid exhibit a clear R ▪ m layer structure. The powders by other grinding aids like heptane show some impurity peaks in the XRD pattern. The former powders show a uniform particle size distribution of less than 1 μm average size while the latter shows a wide distribution ranging from 1 to 10 μm. Energy dispersive X-ray (EDX) analysiss show that the ratio of Ni, Co, and Mn content in the powder is approximately 1/3, 1/3, and 1/3, respecively. The EDX data indicate no incorporation of sodium or chlorine into the powders. Charge-discharge tests gave an initial discharge capacity of 160 mAh·g −1 for the powders with NaCl addition while 70 mAh·g −1 for the powders with heptane.

Syntheses of LiCoO 2 for cathode materials of secondary batteries from reflux reactions at 130–200 °C

Low temperature syntheses of LiCoO 2 cathode materials for Li-secondary battery applications were studied in aqueous solutions by hydrothermal and reflux reactions. By controlling the oxidation potential of the reaction environments, we could synthesize phase pure LiCoO 2 directly from Co(OH) 2 at as low as 130 °C, contrary to the reported hydrothermal reactions at 200–220 °C starting with CoOOH. Having high pH over 15 and an O 2 flow induced the oxidation reaction of the divalent cobalt in Co(OH) 2. The products so obtained have well-crystallized high temperature form of LiCoO 2 with the layered structure as proved by powder X-ray diffraction (XRD) and the Raman spectroscopy data. The particles have a uniform size distribution around 100 nm with well-developed crystallite morphology.

Synthesis and properties of LiNiO 2 as cathode material for secondary batteries

The optimum preparation condition and electrochemical properties of LiNiO 2 as the cathode material for lithium secondary batteries were investigated. LiNiO 2 samples were prepared from Li(OH) 2·H 2O and Ni(OH) 2 in the range from 500 to 900 °C. The compound prepared in an oxygen atmosphere at 700 °C exhibited the highest discharge capacity of 200 mAh/g in the voltage range from 3.0 to 4.3 V. The structure and charge-transfer resistance of the Li 1− x NiO 2 compound were examined at each state-of-charge by X-ray diffractometry and a.c. impedance spectroscopy. The charge-transfer resistances were low in the range of 0.15< x<0.75, which was related to the expansion of the interlayer distance between NiO 2 layers.

Ac complex impedance, dc resistivity, 7Li and 23Na NMR studies of the layered Li(Na) xMo 2O 4 system

Layered lithium molybdates of formula Li x Mo 2O 4 have been shown earlier to be promising cathode materials for secondary batteries. Nevertheless, a better understanding of the evolution of their transport properties as a function of Li composition and water intercalation is still required. This paper reviews the recent progress towards this understanding. ac and dc measurements have been used to describe the transport properties of the following compositions: Li 1.3Mo 2O 4, Li 2Mo 2O 4, Li 0.5(H 2O) 1.3Mo 2O 4. A combined analysis of the Arrhenius plots of conductivity and NMR spectra for the above samples suggests only one type of atomic site, between the MoO 2 layers, for the Li ions, in agreement with the results obtained by X-ray crystallographic studies. A similar study of the corresponding sodium phases: Na 0.5mo 2O 4, Na 0.9Mo 2O 4, Na 1.3Mo 2O 4 and Na 0.4(H 2O) 1.2 Mo 2O 4, is also presented.

Lithium Insertion in V 3Nb9 O 29. A Wadsley‐Roth Type Phase

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ChemInform Abstract: NON‐STOICHIOMETRIC MOLYBDENUM OXIDES AS CATHODES FOR LITHIUM CELLS. PART III. ELLS BASED ON MO18O52

AbstractMo18O52, das bis zu 1.2 Li /Mo in seine Schichtstruktur vom MoO3‐Typ einbauen kann, eignet sich gut als Primärkathode in Li‐Zellen, in denen es hohe spezifische Kapazitäten bei hohen Stromdichten liefert.

Non-stoichiometric molybdenum oxides as cathodes for lithium cells: Part III. cells based on Mo 18O 52

The non-stoichiometric Mo 18O 52 oxide, based on the MoO 3 structure, was tested as a cathode material in both primary and secondary Li cells. It may intercalate reversibly in its layered structure up to 1.2 Li/Mo (at 0.5–1.0 mA cm −2), so forming ternary phases. In the solid matrix Li + ion diffusion is relatively fast ( D≈10 −9 cm 2 s −1) and gives rise to a structure in which Li + is tetrahedrally coordinated by oxygen. This oxide shows a high rate capability and can also act as a cathode material for secondary batteries in the low-rate range. The resemblance to the parent oxide MoO 3 is obviously marked but differences were found with regard to the effect of additives and to the recharge efficiency, due to some structural differences.