Lithium research activity

The synthesis and structural study of the stable P-heterocylic carbene 49 and related structures (e.g., structures 48 and 52 see Figure 3) have attracted some recent research activity <2005AGE1700, 2002JA2506, 2006AGE2598, 2006AGE7447>. The synthesis of the stable P-heterocylic carbene 49 was accomplished in two steps (1) a formal [3+2] cycloaddition of the readily available phosphaalkene 123 with acetonitrile in the presence of silver triflate afforded salt 124, and (2) the isolated and recrystallized salt 124 was deprotonated by lithium hexamethyldisilazide in tetrahydrofuran (THF) to afford carbene 49 as relatively stable light-yellow crystals (Scheme 10) <2005AGE1700>. 

Despite the good electrochemical characteristics and simplicity of preparation, Li Co02 is very expensive and highly toxic. These drawbacks have stimulated wide research activity targeted toward the development of alternate cathode materials for lithium-ion batteries. In this regard, hthium nickel oxide (LiJSIi02) could be more attractive due to its lower cost and toxicity. 

In this respect, this chapter details the fundamentals and most important advances in the research activities on lithium intercalation into and deintercalation from transition metals oxides and carbonaceous materials, especially from thermodynamic and kinetic points of view, including methodological overviews. The thermodynamics of lithium intercalation/deintercalation is first introduced with respect to a lattice gas model with various approximations, after which the kinetics of lithium intercalation/deintercalation are described in terms of a cell-impedance-controlled model. Finally, some experimental methods which have been widely used to explore the thermodynamics and kinetics of lithium intercalation/deintercalation are briefly overviewed. 

Shortly following the widespread commercialization of lithium-ion hatteries as power sources in portable electronic devices, nanotechnology came to the forefront of research and development in materials science. Nanostmctured materials, which have dimensions on the order of 100 nm or less, have unique properties that are often significantly different from their hulk (or micronscale) counterparts. Because of these unique properties, the use of nanomaterials in lithium-ion battery electrodes offers the potential for improved performance in terms of charge-storage capacity, rate capability, and cycle life. The increasing capabilities for synthesis of electrode materials as nanoparticles, nanocrystallites, or nanocomposites has resulted in an explosion of research activity in this area and, in several cases, commercialization of batteries containing nanostructured electrodes. 

Through intense research activities, we have been able to establish the first advanced lithium-ion battery system for EVs since 1995, which combined thermal design and cell control, as well tts a sophisticated cell design. 

In practice, it is the difficulty of obtaining the expected properties which has led to the intensity of the research activity. Many of the problems arise because of the extreme reactivity of lithium metal. It must be handled in the absence of moisture, oxygen and, perhaps, even nitrogen and is stable only in certain media. Hence, the study as well as the manufacture of lithium batteries requires the development of special techniques. In fact, in many lithium battery electrolytes the metal is clearly thermodynamically unstable and the lithium remains in the stored battery only because of films formed on its surface. Hence, it is the properties of these surface films which largely determine battery performance. It has been found that in several diverse media, films are formed that protect the metal on open circuit but still allow anodic dissolution at a reasonable rate (and even recharge of the electrode, i.e. deposition of lithium). There is no doubt, however, that the presence of the films degrade battery performance to some extent. Certainly, the film properties cannot be predicted and, hence, the search for battery electrolytes has been largely empirical. 

In the countries engaged in research in this field, the consequences of this have already become apparent. In Japan, MITl did not renew a 10 year research fund, thereby forcing private companies to bear the entire financial responsibility for ICP research in industry and at the universities. In the United States too, continuity of finance for research would seem to be a subject of much uncertainty. The present situation in Germany is no different. A number of leading companies that had spent more than 10 years researching in the field of conductive polymers have mostly cut back their research activities or even discontinued them. Even the development of batteries based on PAni, PPy, or lithium-ICP composites has been stopped entirely in Europe and the United States. Attempts at commercialization in Japan proved a failure. 

One criterion for the anode material is that the chemical potential of lithium in the anode host should be close to that of lithium metal. Carbonaceous materials are therefore good candidates for replacing metallic lithium because of their low cost, low potential versus lithium, and wonderful cycling performance. Practical cells with LiCoOj and carbon electrodes are now commercially available. Finding the best carbon for the anode material in the lithium-ion battery remains an active research topic. 

Apart from the work toward practical lithium batteries, two new areas of theoretical electrochemistry research were initiated in this context. The first is the mechanism of passivation of highly active metals (such as lithium) in solutions involving organic solvents and strong inorganic oxidizers (such as thionyl chloride). The creation of lithium power sources has only been possible because of the specific character of lithium passivation. The second area is the thermodynamics, mechanism, and kinetics of electrochemical incorporation (intercalation and deintercalation) of various ions into matrix structures of various solid compounds. In most lithium power sources, such processes occur at the positive electrode, but in some of them they occur at the negative electrode as well. 

Several independent laboratories have now demonstrated that both lithium and valproate (VPA) exert complex, isozyme-specific effects on the PKC (protein kinase C) signaling cascade (reviewed in [3, 5, 11-13]). Not surprisingly, considerable research has recently attempted to identify changes in the activity of transcription factors known to be regulated (at least in part) by the PKC signaling pathway - in particular the activator protein 1 (AP-1) family of transcription factors. In the CNS, the genes that are regulated by AP-1 include those for various neuropeptides, neurotrophins, receptors, transcription factors, enzymes involved in neurotransmitter synthesis, and proteins that bind to cytoskeletal elements [14]. 

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