Intercalation reversible

Further, tungsten oxysulfide films, WOyS, have shown promising behavior as positive electrodes in microbatteries, unlike WS2 that is not suitable as cathode in lithium cells. Using amorphous thin films of WO1.05S2 and WO1.35S2.2 in the cell Li/LiAsFe, 1 M ethyl-methyl sulfone (EMS)/W03,Sz, Martin-Litas et al. [80] obtained current densities up to 37 xA cm between 1.6 and 3 V. In these cathode materials, 0.6 and 0.8 lithium per formula unit, respectively, could be intercalated and de-intercalated reversibly. 

When carbon electrodes are used, Li may be inserted/intercalated reversibly into the carbon at potentials as high as 1 V versus Li/Li+ (after the formation of surface films). In the case of disordered carbons, insertion may occur at even higher potentials. In the case of graphite (as described in the next section), the onset for lithium intercalation is around 0.3 V versus (Li/Li+). With glassy carbon, there is no considerable lithium insertion, and hence this electrode behavior depends solely on the solvent and anion used and their cathodic stability [28],... 

Morcrette et al. (2002) XAS Various other Nb phosphate oxide LiCo oxide Intercalation, reversibility + + n.a. Lithium batteries... 

Other types of insertion electrodes of interest — Graphitic carbons can also insert anions at high potentials (e.g., PFg ion potentials of >4 V vs. Li/Li+, from polar aprotic LiPF6 solutions). There are reports on Mg-insertion electrodes. For instance, Mo6 X8 chevrel phases (X = S, Se) intercalate reversibly with magnesium ions (2 ions per formula). Mg ions can be inserted to VOx compounds and to cubic TiS2. 

Another report by Koch [486] describes a rechargeable aluminum battery based on AlCls/A-ethylpyridinium bromide or AlCls/A-etiiyl-A-methyl imidazol-ium chloride melts and a TiS2 cathode. It has been reported that A1 can intercalate reversibly into a number of sulfides, including TiS2, FeSs and TaS2. 

Phospho-olivines as lithium intercalation materials were reported early in 1997. Unfortunately, researchers did not pay much attention to them because olivine phosphates with low electronic conductivity did not allow most of the lithium ions to intercalate/de-intercalate reversibly. This low reversibility could lead to low capacity, particularly at high current densities. Under the strong driving force of safety requirements when lithium ion batteries are used commercially for both portable devices and EV/HEV applications, olivine phosphate cathode materials, especially LiFeP04, have been revisited globally by researchers since the beginning of the 2F century. Attractive features are... 

Apoptotic intercalator reversal of P-gp (245,334) mediated drug resistance Inhibition of CYPlAl, detoxification by (326)... 

Zirconium monochloride reacts with sodium ethoxide to form additional adducts which hydrolyze in water. The monochloride does not react with benzene in a Friedel-Crafts reaction, and does not enter into intercalation reactions similar to those of zirconium disulfide. Both monohaUdes add hydrogen reversibly up to a limiting composition of ZrXH (131). 

In the lithium-ion approach, the metallic lithium anode is replaced by a lithium intercalation material. Then, tw O intercalation compound hosts, with high reversibility, are used as electrodes. The structures of the two electrode hosts are not significantly altered as the cell is cycled. Therefore the surface area of both elecftodes can be kept small and constant. In a practical cell, the surface area of the powders used to make up the elecftodes is nomrally in the 1 m /g range and does not increase with cycle number [4]. This means the safety problems of AA and larger size cells can be solved. 

The reversible intercalation of various oxoacids under oxidizing conditions leads to lamellar graphite salts some of which have been known for over a century and are now particularly well characterized structurally. For example, the formation of the blue, first-stage compound with cone H2SO4 can be expressed by the idealized equation... 

In redox flow batteries such as Zn/Cl2 and Zn/Br2, carbon plays a major role in the positive electrode where reactions involving Cl2 and Br2 occur. In these types of batteries, graphite is used as the bipolar separator, and a thin layer of high-surface-area carbon serves as an electrocatalyst. Two potential problems with carbon in redox flow batteries are (i) slow oxidation of carbon and (ii) intercalation of halogen molecules, particularly Br2 in graphite electrodes. The reversible redox potentials for the Cl2 and Br2 reactions [Eq. (8) and... 

It was also shown in 1983 [11] that lithium can be reversibly inserted into graphite at room temperatures when a polymeric electrolyte is used. Prior experiments with liquid electrolytes were unsuccessful due to co-intercalation of species from the organic electrolytes that were used at that time. This problem has been subsequently solved by the use of other electrolytes. 

The quality and quantity of sites which are capable of reversible lithium accommodation depend in a complex manner on the crystallinity, the texture, the (mi-cro)structure, and the (micro)morphology of the carbonaceous host material [7, 19, 22, 40-57]. The type of carbon determines the current/potential characteristics of the electrochemical intercalation reaction and also potential side-reactions. Carbonaceous materials suitable for lithium intercalation are commercially available in many types and qualities [19, 43, 58-61], Many exotic carbons have been specially synthesized on a laboratory scale by pyrolysis of various precursors, e.g., carbons with a remarkably high lithium storage capacity (see Secs. 

Because of the variety of available carbons, a classification is inevitable. Most carbonaceous materials which are capable of reversible lithium intercalation can be classified roughly as graphitic and non-graphitic (disordered). 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

Using dilatometry in parallel with cyclic voltammetry (CV) measurements in lmolL 1 LiC104 EC-l,2-dimethoxy-ethane (DME), Besenhard et al. [87] found that over the voltage range of about 0.8-0.3 V (vs. Li/Li+), the HOPG crystal expands by up to 150 percent. Some of this expansion seems to be reversible, as up to 50 percent contraction due to partial deintercalation of solvated lithium cations was observed on the return step of the CV. It was concluded [87] that film formation occurs via chemical reduction of a solvated graphite intercalation compound (GIC) and that the permselective film (SEI) in fact penetrates into the bulk of the HOPG. It is important to repeat the tests conducted by Besenhard et al. [87] in other EC-based electrolytes in order to determine the severity of this phenomenon. 

Numerous intercalation reactions are known in which one reactant enters the lattice of the other. Such behaviour is conveniently illustrated by reference to two recent studies. Lithium undergoes a low temperature (298 K) topochemical reversible reaction with transition metal compounds (e.g. TiS2, NbSe3) [1211] in which the host lattice structure may be partially retained (e.g. in Li TiS2, LijNbSe3). The reaction [1212]... 

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