Insertion material/compound

Insertion (intercalation) compounds. Insertion compounds are defined as products of a reversible reaction of suitable crystalline host materials with guest molecules (ions). Guests are introduced into the host lattice, whose structure is virtually intact except for a possible increase of some lattice constants. This reaction is called topotactic. A special case of topotactic insertion is reaction with host crystals possessing stacked layered structure. In this case, we speak about intercalation (from the Latin verb intercalare, used originally for inserting an extra month, mensis intercalarius, into the calendar). 

In other cases, this method yields a virtual oxidation number which only corresponds to a mean value, though it is still useful for writing redox half-reactions. A simple example is given by the iron oxide Fe304, which contains Fe " and Fe " ions in its crystal lattice, but which can be formally considered as an iron oxide with an iron oxidation number equal to -1-8/3. This is also the case with numerous compounds used in batterieswhich are called insertion materials, such as LixMn02, HxWOs, and UXV2O5, etc. Their oxidation numbers still remain a subject of discussion today. 

There has been growing interest in the field of supercapacitors due to their possible applications in medical devices, electrical vehicles, memory protection of computer electronics, and cellular communication devices. Their specific energies are generally greater than those of electrolytic capacitors and their specific power levels are higher than those of batteries. Supercapacitors can be divided into redox supercapacitors and electrical double layer capacitors (EDLCs). The former uses electroactive materials such as insertion-type compounds or conducting polymers as the electrode, while the latter uses carbon or other similar materials as the blocking electrode. 

Materials which undergo optical (colour) changes when exposed to a current or when immersed in an electric field are called electrochromic materials (ECMs). Although an electrochromic effect may be shown by a variety of materials, the most studied ECMs are ion insertion inorganic compounds and organic conducting polymers. 

There are quite some insertion materials. Here it is classified based on their elements and includes oxides, carbonaceous materials, multiatom anion compounds, inverse spinels, sulfides, nitrides, silicon, and tin alloys [1]. Here the main topic will be related to lithium insertion. For the other kinds of insertion compounds such as sodium, potassium, sulfate, and the like, please refer to other references [2]. 

Pure metals and metal compounds (metal oxides, intermetallic compounds) which are capable of forming alloys with lithium constitute another category of electrode materials versus the insertion materials seen previously. They are used for the negative electrode in lithium-ion batteries because their redox potential versus lithium is less than 2 V. They are cited in the following four sections ... 

Thiophenes of type 31 (X-Y = CH) were generated via Lawesson s reagent-mediated cyclization of 1,4-dicarbonyl compounds 30 under microwave irradiation in the absence of solvent [37]. The reaction was carried by mixing the two solid reagents in a glass tube inserted inside a household microwave apparatus and irradiating until the evolution of H2S ceased. An interesting application of this method is the preparation of liquid crystals and other ferro- and antiferroelectric material such as compound 33 (Scheme 10). 

Bruce PG, Irvine ITS (2001) Insertion Compounds. In Encyclopedia of Materials Science and Technology, Elsevier Science Ltd Oxford ISBN 0-08-0431526, pp. 4115-4121 SchoUhom R (1980) Reversible topotactic redox reactions of solids by electron/ion transfer. Angew Chem Int Ed Engl 19 983-1003... 

The thermodynamic properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries, as it may provide a considerably higher energy density than the commonly used lead-acid and nickel-cadmium systems, while in contrast to Pb and Cd, magnesium is inexpensive, environmentally friendly, and safe to handle. However, the development of Mg-ion batteries has so far been limited by the kinetics of Mg " " diffusion and the lack of suitable electrolytes. Actually, in spite of an expected general similarity between the processes of Li and Mg ion insertion into inorganic host materials, most of the compounds that exhibit fast and reversible Li ion insertion perform very poorly in Mg " ions. Hence, there... 

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