Nickel oxide lithium doped

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

Fig. 27. Differential heats versus coverage for the successive adsorptions, at 30°C, of carbon monoxide (A), oxygen(B), and, again, carbon monoxide (C) on the surface of lithium-doped nickel oxide. Reprinted from (54) with permission J. Chim. Phys.

The analysis of the thermograms recorded during the interaction of the successive doses of the different reactants in the sequence may also yield very relevant informations. Through the use of different techniques, it has been shown, for instance, that the different steps of the mechanism of the CO oxidation, at room temperature, at the surface of pure [TNJiO (200)3 19, 82) or lithium-doped 54) nickel oxide, may be written ... 

Nickel oxide, NiO, is doped with lithium oxide, Li20, to form Li Ni, xO with the sodium chloride structure, (a) Derive the form of the Heikes equation for the variation of Seebeck coefficient, a, with the degree of doping, x. The following table gives values of a versus log[(l-x)/x] for this material, (b) Are the current carriers holes or electrons (c) Estimate the value of the constant term k/e. 

As in the previous chapter, most work has been carried out on oxides, and these figure prominently here. As the literature on oxides alone is not only vast but is also rapidly increasing, this chapter focuses upon a number of representative structure types to explain the broad principles upon which the defect chemistry depends. However, despite considerable research, the defect chemistry and physics of doped crystals is still open to considerable uncertainty, and even well-investigated simple oxides such as lithium-doped nickel oxide, Li Nij- O, appear to have more complex defect structures than thought some years ago. 

Despite the many investigations of the defect chemistry of lithium-oxide-doped nickel oxide, the real nature of the defect structure still remains uncertain. For many years the holes were regarded as being localized on Ni2+ ions to form Ni3+, written Mi - ... 

Acceptor doping, as in lithium oxide doping of nickel oxide, produces p-type thermistors. The situation in nickel-oxide-doped Mn304 is similar but slightly more complex. This oxide has a distorted spinel structure (Supplementary Material SI), with Mn2+ occupying tetrahedral sites and Mn3+ occupying octahedral sites in the crystal, to give a formula Mn2+[Mn3+]204, where the square parentheses enclose the ions in octahedral sites. The dopant Ni2+ ions preferentially occupy... 

Acceptor doping, as in lithium oxide doping of nickel oxide, leads to the production of holes and produces p-typc thermistors ... 

Molten Carbonate Fuel Cell The electrolyte in the MCFC is a mixture of lithium/potassium or lithium/sodium carbonates, retained in a ceramic matrix of lithium aluminate. The carbonate salts melt at about 773 K (932°F), allowing the cell to be operated in the 873 to 973 K (1112 to 1292°F) range. Platinum is no longer needed as an electrocatalyst because the reactions are fast at these temperatures. The anode in MCFCs is porous nickel metal with a few percent of chromium or aluminum to improve the mechanical properties. The cathode material is hthium-doped nickel oxide. 

Finally, Al (/= 5/2) and Co NMR spectroscopy have been used to probe AP+ in Al-doped lithium cobalt oxides and lithium nickel oxides. A Al chemical shift of 62.5 ppm was observed for the environment Al(OCo)e for an AP+ ion in the transition-metal layers, surrounded by six Co + ions. Somewhat surprisingly, this is in the typical chemical shift range expected for tetrahedral environments (ca. 60—80 ppm), but no evidence for occupancy of the tetrahedral site was obtained from X-ray diffraction and IR studies on the same materials. Substitution of the Co + by AF+ in the first cation coordination shell leads to an additive chemical shift decrease of ca. 7 ppm, and the shift of the environment A1(0A1)6 (20 ppm) seen in spectra of materials with higher A1 content is closer to that expected for octahedral Al. The spectra are consistent with a continuous solid solution involving octahedral sites randomly occupied by Al and Co. It is possible that the unusual Al shifts seen for this compound are related to the Van-Vleck susceptibility of this compound. 

To diminish electrode pore flooding, McHenry and Winnick [106] studied new membrane formulations which included borosilicate glass and zeolites. These showed improved electrolyte retention and polarization behavior as compared with MgO-based membranes. The reduction in flooding allowed the cell to handle three times the current for the same applied overpotential. The same authors [107] also found that Lao,8Sro.2Co03 electrodes reacted with the molten pyrosulfate electrolyte. Lithium-doped nickel oxide replacement electrodes, however, were not degraded. 

Properties of doped oxides are summarized in Table X. The fraction of added lithium ions which is not extracted from the dehydrated solid by boiling water is considered as dissolved into the lattice of nickel oxide (80). It appears that the maximum solubility of lithium in nickel oxide is 2 at. % Li in these experiments (Table X). Because of the low temperature of firing (250°), lithium ions are most probably located in the surface layers of the oxide lattice. The amount of dissolved gallium ions is not known. 

Surface areas of pure or doped nickel oxides are not very different (Table X). It seems, however, that incorporation of lithium increases slightly the surface area of the solid and that incorporation of gallium ions has the opposite effect. 

The stoichiometric compositions of pure and doped nickel oxides were determined by chemical analysis (30). As presented in Section II, the difference 2[Ni3+] — [Ni ) is evaluated and results are expressed in at.% Oexc if the difference is positive or in at.% Niexc if the difference is negative. Chemical analyses (30) and magnetic measurements (33) have shown that pure nickel oxide prepared under vacuum at 250° contains a small excess of metallic nickel (Table X). The surprising result is that oxides containing up to 4 at.% Li (total) or 1.5 at.% Li (actually dissolved) present a stoichiometric composition which is similar to that of pure NiO(250°) (Table X). Nickel oxide containing 9.5 at.% Li (total) presents an excess of oxygen (0.052 at.% Oexc) which is small, however, compared to the amount of lithium ions actually incorporated in the lattice (1.95 at.% Li) (Table X). 

When pure and doped nickel oxides, prepared in vacuo, are heated in oxygen at 250°, their electrical conductivity increases and their color changes from yellowish green or green to black (77). Increase of electrical conductivity is associated with the increase of the number of Ni + ions resulting from the oxygen sorption. The electrical conductivity of the lithium-doped sample [NiO(10 Li)(250°)] is larger (0250° = 1-86 x IO-2... 

Fio. 29. Differential heats of adsorption of carbon monoxide on lithium-doped nickel oxide [NiO(10 Li)(250°)] at 30°. 

Adsorption of carbon monoxide at 30° decreases the electrical conductivity of lithium-doped nickel oxide [NiO(10 Li)(250°)] which has been precovered by oxygen, at the same temperature from 1.8 x 10- to 6.2 X 10-12 ohm- cm-1. Formation of neutral species during this interaction is thus observed on all samples. Thermochemical cycles 1, 2 (Table XIII) and 3 (Table XIV) yield, however, ambiguous results in the case of NiO(10 Li)(250°). It appears from cycle 3 (Table XIV) that the intermediate formation of COs-(ads) ions is possible but the direct formation of adsorbed carbon dioxide is also probable from cycle 1 (Table XIII). Cycle 2, on the other hand, testing the formation of gaseous carbon dioxide, is balanced neither for low nor for intermediate surface coverages, although carbon dioxide is found in the cold trap after the adsorption of carbon monoxide (1.5 cm /gm). 

Interaction between oxygen and carbon monoxide preadsorbed on NiO(10 Li)(250°) produces C03-(ads) ions, as in the case of all other samples. Thermochemical cycles 4 and 5 (Table XV) show, moreover, that the subsequent conversion of the complex ions by carbon monoxide yields carbon dioxide which remains partially adsorbed. Reaction mechanism II is therefore also probable on lithium-doped nickel oxides. 

On the surface of the lithium-doped nickel oxide, formation of carbon dioxide results from the conversion of COs lads) ions by carbon monoxide. Two surface interactions from mechanisms II and III may produce these complex ions. 

Ganesan, P. Colon, H. Haran, B. White, R. Popov, N.B. Study of cobalt-doped lithium-nickel oxides as cathodes for MCFC. J. Power Sources 2002, 111 (1), 109-120. 

The cathode consists of lithiated nickel oxide. Nickel oxide is a p-type semiconductor, having a rather low conductivity. When doped with lithium oxide, its conductivity increases tens of times, owing to a partial change of Ni + to Ni + ions. The lithiation is accomplished by treating the porous nickel electrode with a lithium hydroxide solution in the presence of air oxygen. The compound produced has a composition given as Lij +Nii j( Nijj +0. This lithiation of nickel oxide was first applied in 1960 by Bacon in his alkaline fuel cell. 

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