Lithium, insertion compounds

Recently, lithium-ion inserted compounds have been investigated as new anodes. These compounds have the possibility of... 

As discussed below, there are problems with morphological changes and passivation reactions at lithium metal negative electrodes in secondary cells, which reduce cycle life and the practical energy density of the system, and may in some circumstances introduce safety hazards. A more recent development involves the replacement of the lithium metal anode by another insertion compound, say C Dm. In this cell, the electrochemical process at the negative side, rather than lithium plating and... 

Soudan, P., Pereira-Ramos, J.P, Farcy, J., Gregoire, G., and Baffler, N. 2000. Sol-gel chromium-vanadium mixed oxides as lithium insertion compounds. Solid State Ionics 135, 291-295. 

Insertion compounds of lithium (which is small and diffuses quickly in many hosts) can be prepared by reaction with n-butyl lithium. For example ... 

The last few years have witnessed a high level of activity pertaining to the research and development of all-solid, thin-film polymer electrolyte batteries most of these use lithium as the active anode material, polymer-based matrices as solid electrolytes, and insertion compounds as active cathode materials. High-performance prototypes of such batteries stand currently under research, whose trends are expected to include the development of amorphous polymers with very low glass-transition temperatures, mixed polymer electrolytes, and fast-ion conductors in which the cationic transport number approaches unity. 

In other cases, crystal lattice decomposition occurs under cathodic insertion of lithium, and the cathodic process becomes irreversible. In this case, the product of the cathodic reaction is a mixture of a lithium compound (oxide, chalcogenide) with a reduced form, particularly, directly with a metal. It is such processes that occur when iron sulfide or copper oxide are used ... 

The effect does not seem to be related to thermodynamic barriers since the electrochemical insertion of lithium into common intercalation compounds, such as LiVaOs or VeOn, is an easily reversible process. In fact, electrochemical and spectroscopical studies carried out in liquid electrolytes have clearly demonstrated that these intercalation compounds can easily and repeatedly accept Li" ions without undergoing significant structure alterations. It has to be pointed out, however, that these studies have been carried out at low temperatures. Recent investigations performed at elevated temperatures (i.e. around 120°C) have indicated a crystalline to amorphous... 

Originally, this referred specifically to layered structures that can undergo insertion of ions or molecules between the van der Waals gaps, but is now commonly used for any structure that undergoes topotactic insertion reactions. For Li-ion battery materials, it refers specifically to compounds that undergo reductive insertion of lithium ions, such as graphite (used as an anode) or LiCo02 (used as a cathode). 

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