Oxides with Spinel Structure

Many of these oxides have been studied and share common features [22] illustrated in Fig. 10.10. The first discharge reaction may involve Li intercalation into the lattice (single-phase reaction) (Fig. 10.10), followed by crystal structure destruction (amorphization), and finally formation of the respective nanosized metal particles via a two-phase reaction. These three steps correspond to the regions labeled a, b, c, respectively in Fig. 10.10a. 

The theoretical capacity of C03O4 according to the conversion reaction is 890 mAh g and has thus attracted attention. In addition, this is the most stable 

Materials Current density (mA g ) Initial charge capacity (mAh g ) Initial coulombic efficiency (%) References 

The successful synthesis of porous Mu203 is recent. In 2011, two kinds of precursor morphologies, oval-shaped and straw-sheaf-shaped, have been selectively prepared by hydrothermal treatment of different functional polyol molecules (oval-shape 

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Also, other metal oxide coatings are possible, for example, electrochemically deposited manganese dioxide. Moreover, further electrocatalytically active oxides are research objectives, for example, oxides with spinel structure such as CoMu204 [36]. 

Ottonello G. (1986). Energetics of multiple oxides with spinel structure. Phys. Chem. Minerals., 13 79-90. 

Blasse, G. (1964). Crystal chemistry and some magnetic properties of mixed oxides with spinel structure. Philips Research Reports, Suppl. 3, 1-139. 

Verwey, E. J. W. Heilmann, E. L. (1947). Physical properties and cation arrangements of oxides with spinel structure. Journal of Chemical Physics, 15, 174-80. 

In this section, we have chosen to present the two alternatives to layered oxides currently commercialized (1) the manganese oxides with spinel structure that make a less expensive alternative to batteries requiring a limited lifespan and (2) the olivine LiFeP04 which by its development at the nanoscale overthrew all the concepts that had previously been established and thus opened the way to an entire field of research into new polyanionic materials with poor electronic conducting properties. 

E.J.W. Verwey, E.L. Heilmann, Physical properties and cation arrangement of oxides with spinel structures 1 cation arrangement in spinels. J. Chem. Phys. 15, 174—180 (1947)... 

As it can be seen in Fig.l, the dependence of the effective molar volume of oxides on the a/b ratio shows linear character in the composition range 0.5ions with the same charge (2+, 3+) but also in the case of oxides showing deviation from the stoichiometry, for many oxide phases (Magneli phases) with ions in different oxidation states and, as in the case of Fei.yO or M3O4 oxides with spinel structure, when metal ions have different coordination number, 4 or 6 (tetrahedral or octahedral). 

Wakihara M (2005) Lithium manganese oxides with spinel structure and their cathode properties for lithium ion battery. Electrochem 73 328-335... 

Ternary Metal Oxides with Spinel Structure... 

Different materials in which a Li alloying-dealloying element is added to a conversion of transition metal oxide have been investigated, hoping that the addition of the two effects would improve the electrochemical properties. The most promising materials entering this category are oxides with spinel structure. 

Kaolinite is transformed into X-ray amorphous state when activated in air. According to authors [14,15], amorphization involves the destruction of bonds between tetrahedral and octahedral layers inside the package, till the decomposition into amorphous aluminium and silicon oxides. Other researchers [ 16,17] consider that amorphized kaolinite conserves the initial ordering of the positions of silicon atoms while disordering of the structure is due to the rupture of A1 - OH, Si - O - A1 bonds and the formation of molecular water. Endothermic effect of the dehydration of activated kaolinite is shifted to lower temperatures while intensive exo-effect with a maximum at 980°C still conserves. When mechanically activated kaolinite annealed at 1(X)0°C, only mullite (3Al20j-2Si0j) and X-ray amorphous SiOj are observed. In this case, the phase with spinel structure which is formed under thermal treatment of non-activated kaolinite is not observed thus, mechanical activation leads to the formation of other phases. 

The formation ofthe spinel consists of two steps. Firstly, the hydroxide formed in co-precipitation occurs dehydration reaction to form oxides, then tire oxides was calcined to form copper ferrite with spinel structure. If the calcinations temperature is not high enough or tlie time is not long enough, the phase transformation could not be finished. Therefore, only the temperature exceeds 800°C, it is possible to form homogenous spinel type CuFe2O4 furthermore, the longer calcinations process is beneficial to the formation of pure spinel type ferrites. 

If without additives, a carrier such as A3 consists of a mixture of 8-, 0-, and a-aluminas between 900° and 1000°C. The presence of the metal oxides, introduced by impregnation, effectively maintains a cubic type structure at a calcining temperature of 900°-1000°C. With alumina, these oxides form spinel-structured compounds which are more or less well crystallized. Because of the insertion of alumina, the lattice parameter of these compounds is expanded with respect to that of the stoichiometric spinel. The properties of the carrier are thus maintained up to a temperature which depends on the considered mixed oxide. At this temperature—about 1000 °C with magnesium aluminate and 900°C with zinc and copper aluminates—the stoichiometric spinel recrystallizes while a-alumina is rejected (6). The carrier then suddenly loses its mechanical and structural properties. None of the mentioned additives could improve the stability of the Cl carrier above 1000°C. 

Similarly, magnesium indium oxide is regarded as a potential semiconductor with spinel structure. Most importantly, spinel does not swell, change dimensions, or amorphize upon high... 

A. Kalendova, D. Vesely, P. Kalenda, Pigments with Ti —Zn, Sr, Mg -based on mixed metal oxides with spinel andperovskite structures for organic coatings, Pigm. Resin Technol. 36 (2007)... 

Unlike cobalt and nickel, manganese does not form a stable, pure LiMn02 phase and forms the spinel structure instead, named after the mineral of spinel (Table 1.3) with the composition of Lio.5Mn02, conunonly expressed as LiMn204. Manganese-based cathode materials are attractive mainly due to their low cost compared to cobalt and nickel. A wide variety of the hthiated manganese oxides with multiple structures and compositions (Li Mn 0 ratios) exist and many of these compounds can reversibly intercalate lithium, but amongst these materials, spinel materials and the layered derivatives are the most mature, to the point of commercial availability. Spinel-stractured materials will be discussed separately in the next part of this chapter. 

The wet chemical synthesis of precursor materials for ferrites with spinel structure by coprecipitation of metal chlorides and subsequent calcinations yields finegrained powders with a homogeneous distribution of the constituent oxides, for example ... 

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