Insertion Electrode Materials

Winter M, Besenhard JO, Spahr ME, Novak P. Insertion electrode materials for rechargeable lithium batteries. Adv Mater 1998 10 725-763. 

There are two main kinds of rechargeable battery based on lithium chemistry the lithium-metal and the lithium-ion battery. In both the positive electrode is a lithium insertion material the negative in the former is lithium metal and in the latter it is a lithium insertion host. The reason for the application in lithium batteries of insertion electrode materials, which are electronic and ionic conductive solid matrixes (inorganic and carbon-based), is that electrochemical insertion reactions are intrinsically simple and highly reversible. 

This section will provide a general description of the lithium-metal battery, especially with regard to the problems arising from the use of lithium metal, and introduce the lithium-polymer batteries as a reliable solution to problems deriving from the use of the lithium-metal electrode. The lithium-ion battery will then be taken up and particular emphasis will be given to the insertion electrode materials used in both the lithium-metal and the lithium-ion batteries. 

Table 4. The most investigated positive insertion electrode materials.

Higher OCV values can be attained with lithium alloys (Figure 16), which are under study as negative insertion electrode materials for their high specific capacity... 

Spahr, M.E., Novak, R, Scheifele, W., Haas, O., and Nesper, R., Characterization of layered hthium nickel manganese oxides synthesized by a novel oxidative coprecipitation method and their electrochemical performance as lithium insertion electrode materials, J. Electrochem. Soc., 145, 1113, 1998. 

C. Wang, A. J. Appleby, and F. E. Little [2001] Comparison of the Electrochemical Impedance Spectroscopy Characteristics of Insertion Electrode Materials Used in Secondary Metal Hybride and Lithium-Ion Electrodes,... 

The incremental capacity of an insertion electrode material used in ambient temperature batteries can be estimated from voltage spectroscopy measurements which can help to the determination of phase diagram of the insertion compotmd [1], In the first section, we examine the various aspects of electrochemical lithium insertion into a number of electrode materials. The experimental techniques of solid-state electrochemistry are presented in the second section. Voltage spectroscopy and phase diagram during Li intercalation into cathode materials are investigated. Finally, the experimental determination of the diffusion coefficient of ions in solid materials is investigated. 

Whereas in many metals with relatively simple and isotropic crystal structures the parameter / has values between 0.5 and 1, it can have much more extreme values in materials in which the mobile species move through much less isotropic structures with 1-D or two-dimensional (2-D) channels, as is often the case with insertion reaction electrode materials. As a result, radiotracer experiments can provide misleading information about self-diffusion kinetics in such cases. 

Beginning in the early 1980s [20, 21] metallic lithium was replaced by lithium insertion materials having a lower standard redox potential than the positive insertion electrode this resulted in a "Li-ion" or "rocking-chair" cell with both negative and positive electrodes capable of reversible lithium insertion (see recommended papers and review papers [7, 10, 22-28]). Various insertion materials have been proposed for the anode of rechargeable lithium batteries,... 

From a thermodynamic point of view, apart from charge density and specific charge, the redox potential of lithium insertion into/removal from the electrode materials has to be considered also. For instance, the redox potential of many Li alloys is between -0.3 and -1.0 V vs. Li/Li+, whereas it is only -0.1 V vs. 

Given the importance of particle size to rate capabilities in Li+ batteries, preparation of nanostructures of Li+ insertion material for possible use as electrodes in Li+ batteries seemed like an obvious extension of our work on nanomaterials. The fact that these nanostructures can be prepared as high-density ensembles that protrude from a surface like the bristles of a brush (Fig, 2A) seemed particularly useful for this proposed application because the substrate surface could then act as a current collector for the nanostructured battery electrode material. 

The subscript Pt is inserted to remind us that the electrons come from a conductive electrode. Platinum (Pt) is usually an excellent choice of electrode, while other common electrode materials are gold, mercury and glassy carbon (GC). 

While XAS techniques focus on direct characterizations of the host electrode structure, nuclear magnetic resonance (NMR) spectroscopy is used to probe local chemical environments via the interactions of insertion cations that are NMR-active nuclei, for example lithium-6 or -7, within the insertion electrode. As with XAS, NMR techniques are element specific (and nuclear specific) and do not require any long-range structural order in the host material for analysis. Solid-state NMR methods are now routinely employed to characterize the various chemical components of Li ion batteries metal oxide cathodes, Li ion-conducting electrolytes, and carbonaceous anodes.Coupled to controlled electrochemical in-sertion/deinsertion of the NMR-active cations, the... 

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