Intercalation conversion reaction

The electrode materials currently being used in lithium ion batteries are based on lithium intercalation/de-intercalation reactions. Such reactions are inherently tied to crystallographic considerations. The insertion of high concentrations of lithium ions is usually limited to one lithium atom per host atom because hthium concentrations above this level result in phase transformations that may lead to the formation of irreversible phases. Recently, however, another approach has been devised in which the material is not constrained by intercalation and instead accomplishes energy storage through a process based on conversion reactions. 

Pseudocapacitance in normally purely intercalation materials has only been observed in extremely high surface area materials with nanoscale diffusion lengths. In conversion reactions, the nanodimensional size of the metal particles is instrumental in making the reactions highly reversible. 

Cabana, J., Monconduit, L., Larcher, D., and Palacin, M. R, (2010]. Beyond intercalation-based Li-ion batteries The state of the art and challenges of electrode materials reacting through conversion reactions, 4dv. Mater., 22, pp. E170-E192. 

I = 7/2-1—> 5/2-F). The materials that can be studied, thanks to the Mossbauer effect of the above-mentioned nuclei, are also varied. Both cathode and anode materials can be examined. Moreover, the electrochemical reactions in which they are involved may vary from intercalation to conversion and/or alloying. Table 28.1 shows some examples. Fe MS provides useful information in the study of insertion cathodes, such as olivine LiFeP04, as well as layered solids structurally related to LiCo02. Fe MS is also useful to analyze anodes consisting of binary or ternary oxides for conversion reactions, or tin intermetallics that react with lithium by alloying processes. In the latter case, a multiisotope approach can be developed, due to the Mossbauer effect of both Fe and Sn nuclei. 

Furthermore, it should be noticed that phase-field modeling is an elegant approach in which parameters can in principle be estimated from first principles calculations, such as the inter-phase energies in conversion reactions (e.g., CoO/Co°, Co°/Li20) (Fig. 9) [22, 23]. It has to be underlined that until now phase-field modeling has been mainly used for the simulation of intercalation reactions in LIBs (e.g., Bazant et al. work [24, 25]) and of the reactions of the solid electrolyte interphase formation [26]. 

But not only intercalation materials were characterized by XANES mapping, a recent study by Wang et al. shows an in situ study of the conversion reaction in CuO [52]. They capture both the evolution of morphology as well as the phase distribution at selected voltages revealing a core shell lithiation-delithiation mechanism. 

Electrochemical intercalation and conversion reactions have been investigated in the quest to discover practical cathodes for secondary magnesium batteries. Magnesium intercalation cathodes in particular are attractive due to the potential for a 2-electron reduction at the metal center with insertion of a single ion with size similar to univalent Li". As with Mg anodes, the electrolyte chemistry also plays a substantial role in the behavior of candidate cathode materials. A comprehensive survey of Mg battery cathode technology can be found in the review by Muldoon et al. [34] this chapter summarizes key discoveries in this field. 

Several MOFs have also been used in innovative ways to form Li-ion battery anodes that store Li+ either via the intercalation or via the conversion-reaction mechanism. The group of Tarascon reported an initial specific capacity of 300 mAh g for a LiLterephthalate MOF in 1M LiPFg carbonate electrolytes. Perhaps even more important, the reaction between the lithiated Li -terephthalate MOF and electrolyte was three times less exothermic than that for LiCg, thereby affording a distinct safety improvement. Next, a Li -pyridinedicarboxylate MOF showed reversible Li extraction/insertion with a specific capacity of 160 mAh g at a rate of C/5. A first... 

Lasri K, Dahbi M, Liivat A, Branded D, Edstrdm K, Saadoime I (2013) Intercalation and conversion reactions in Nio sTiOP04/C Li-ion battery anode materials. J Power Some 229 265-271... 

Trade et al. [56] used cationic bis(oxazoHne)-Cu(II) complexes, intercalated into lamellar clays by electrostatic interactions, as catalysts for C - C bond formation reactions. Interestingly, the heterogeneous catalysts led to higher conversions and selectivities than their homogeneous coimterparts. 

Oxygen-free reactions of psoralens, when in close proximity to the target, proceed via the first excited states in which the 3,4-and the 4, 5 7r-bonds of the pyrone and furan moieties, respectively, can undergo C4-cyclization reactions with, e.g., unsaturated bonds of lipids, or the C5=C6 double bonds of thymine in DNA. In reactions with DNA the psoralen is believed to intercalate with DNA in the dark. Subsequent irradiation at 400 nm usually leads to furan-side 4, 5 -monoadduct formation, whereas irradiation at 350 nm increases the formation of crosslinks in which the furan and pyrone rings form C4 cycloadducts to thymines on opposite strands [95], Subsequent irradiation of the 4, 5 -monoadducts at 350 nm leads to formation of crosslinks and conversion into pyrone-side 3,4-monoadducts. Shorter wave-... 

The kinetics of intercalation have been followed by FTIR and QCM gravimetry. For example, the frequency change of a QCM with a 20-layer CdAr film (exposed to H2S) was followed as a function of immersion time in a CdCl2 solution (Fig. 3.5.5) (46). The percent conversion [calculated from mass of film on QCM and stoichiometry in Eq. (3) reaches 100% within about 100 min immersion. In contrast, time-resolved FTIR spectra of CdBe/H2S and HgBe/H2S films immersed into Cd2+ and Hg2+ solutions, respectively, indicated that the intercalation of metal ions into the LB film of BeH takes 24-48 h to complete (21). The kinetics of the sulfidation reaction [Eq. (4) are discussed in a later section. 

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