Intercalation into metal oxides

The cubane cluster organometallic sulfides ( / -C5H4Me)4M4S4 (M = Mo, Fe) have been intercalated into metal oxide hosts, M0O3 or FeOCl, to produce bronzes which are electrically conducting along the crystal axis but are non-conductive in the interlayer direction [372]. 

As a specific example, Li can be intercalated into several oxides with the rutile structure (Murphy, DiSalvo, Caricles and Waszczak, 1978). In Li,jMo02, the structure changes from monoclinic to octahedral and back to monoclinic as x goes from 0 to 1 (Dahn and McKinnon, 1985). In both monoclinic structures. Mo atoms are shifted to form Mo-Mo pairs along the chains (Cox, Cava, McWhan and Murphy, 1982), and these pairs disappear in the octahedral structure at intermediate x (Dahn and McKinnon, 1985). The rutile LijtW02 has been considered as a replacement for metallic Li in electrochemical cells (Murphy et al, 1978). 

In order to improve the textural properties of particle-clay nanohybrids, bulky organic cations are intercalated as a kind of template into particle-intercalated clays before stabilization procedures. Intercalation of the organic cations results in the removal of some of the intercalated nanoparticles and/or in their rearrangement. Subsequent calcination leads to formation of additional pore space that is highly correlated to the geometry and size of the templates. This technique allows fine tuning of textural properties in the preparation of particle-clay nanohybrids. The clay nanohybrids intercalated with metals, oxides, and complexes have a broad range of applications. In particular, metal oxide particle-pillared clays have excellent potentials as catalysts, catalyst supports, selective adsorbents, etc. " ... 

A typical rechargeable battery based on this idea has been constructed. It uses the [Ni(TTL)]a, polymer as the anode, poly-2-vinyl-pyridine-iodine (P2VP (x/2)l2) (68) complex as the cathode, and aqueous KI solution as the electrolyte solution (Equation 13). In the discharging process, electrons flow from the anode [Ni(TTL)]a to the cathode P2VP (x/2)l2 through the load circuit the iodide (or polyiodide) ions formed at the cathode then enter the electrolyte while an equivalent amount of iodide ions from the electrolyte solution intercalate into the oxidized metal tetrathiolene polymer (anode). The electrolyte concentration is therefore conserved. Upon recharging with an opposite... 

Ion intercalation into nickel oxide is often performed in aqueous media. On immersion of nickel oxide into an alkaline solution, such as aqueous KOH, a spontaneous chemical conversion of NiO into a hydrous metal oxide phase Ni(OH)2 proceeds [25]. Hydrous NiO resembles V2O5 in respect to the two-dimensional layered host structure. The Ni(II)/Ni(III) couple responsible for the reversible color change on electrochemical cycling has been identified as the nickel hydroxide/oxy-hydroxide phases [25, 26]... 

For a number of reasons the TiS2 battery was not widely exploited commercially, but similar batteries based upon intercalation into transition-metal oxides LiJCTO2, where T is a 3d transition metal such as Ni, Co, or Mn (or a solid solution of these metals, LiJt.T1 yTj,02) are widely available. The first of these, the Sony cell, introduced in 1991, employs LixCo02 as the cathode and the intercalation of Li into graphite as the anode, to form LivC6. 

A number of transition metal oxides can also be intercalated by lithium. One of the best known examples is VsOi3. The VgOu structure, shown in Fig. 11.19, consists of alternate double and single layers of V2OS ribbons. The layers are connected by vertex sharing of octahedral sites, and this leads to a relatively open framework structure (Wilhelmi, Waltersson and Kihlburg, 1971). Insertion of lithium into the oxide matrix... 

The conversion of the mixed metal oxides into LDHs has been variously referred to as regeneration, reconstruction, restoration, rehydration or the calcination-rehydration process , structural memory effect or simply memory effect . This method is usually employed when large guests are intercalated. It also avoids the competitive intercalation of inorganic anions arising from the metal salts. The procedure is more complicated than coprecipitation or ion-exchange methods, however, and amorphous phases are often produced simultaneously. 

Figure 1. Schematic description of a (lithium ion) rocking-chair cell that employs graphitic carbon as anode and transition metal oxide as cathode. The undergoing electrochemical process is lithium ion deintercalation from the graphene structure of the anode and simultaneous intercalation into the layered structure of the metal oxide cathode. For the cell, this process is discharge, since the reaction is spontaneous.

Are the mechanisms described here applicable to cells operating in nonaque-ous environments It is conceivable that the sequence described by Eqs. (12)-( 14) occurs under certain conditions. The more complex sequence involving coupled electron and cation transfer probably does not. Although Li+ (the electrolyte cation most often used in Gratzel-type cells) is known to intercalate into high-area metal oxide semiconductors [49,90,108-111], the rate is probably too slow to be coupled to injection and back ET in the same way that aqueous proton uptake and release are coupled to these processes. The ability to use water itself as a proton source means that solution-phase diffusional limitations on proton uptake are absent. Alkali metal ion uptake from nonaqueous solutions, on the other hand, clearly is subject to diffusional limitations. 

Batteries. Many 7t-conjugated polymers can be reversibly oxidized or reduced. This has led to interest in these materials for charge-storage batteries, since polymers are lightweight compared to metallic electrodes and liquid electrolytes. Research on polymer batteries has focused on the use of polymers as both the electrode and electrolyte. Typical polymer electrolytes are formed from complexes between metal-ion salts and polar polymers such as poly(ethyleneoxide). The conductivity is low at room temperature due to the low mobility of cations through the polymer-matrix, and the batteries work more efficiendy when heated above the glass-transition temperature of the polymer. Advances in the development of polymer electrolytes have included polymers poly(ethylene oxide) intercalated into layered silicates (96). These solid-phase electrolytes exhibit significantly improved conductance at room temperature. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

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