Energy lithium-based systems

The calcium-calcium chromate thermal cell has been established for many years. In the LiCl-KCl eutectic, the reaction product of this cell is a mixed lithium-calcium-chromium oxide. However,. this system cannot provide as high a specific capacity or energy density as the lithium-based systems described above. Furthermore, it suffers from parasitic chemical reactions which are exothermic and often uncontrolled. 

Figure 4 shows a comparison of practical energy density and specific energy of primary batteries. Two groups can be distinguished the zinc-based and lithium-based systems. 

Miniature applications have become more important in recent years with the general aeeeptance of the behind-the-ear hearing-aid and the advent of the electronic watch. High energy density per unit volume is the prime requirement for a battery in these products. The mercuric oxide-zinc, silver oxide-zinc, zinc-air and lithium-based systems appear to be likely contenders for this market. Although the last two types of battery have been produced in sizes suitable for miniature applications, they are not widely available in this format. These systems will therefore be discussed later in their usual cylindrical form, and the conclusions drawn then may explain the difficulties that have prevented their wide acceptance. 

The high volumetric energy densities reflect the high voltages of the lithium-based systems. One reason for some lack of acceptance in miniature applications is that although one lithium cell could be specified where it is necessary to use two mercury cells in series, a lithium button cell would have a capacity approximately one-hall that of the equivalent mercury cell, and the frequency of battery changing would in extreme cases be correspondingly increased. 

Fig. 7.1 Comparison of gravimetric and volumetric energy density of lithium secondary cells with aqueous electrolyte-based systems...

The method is based on the nearly complete cancellation between the target excitation energy and the binding energy of the attached electron for certain low-energy resonances. For a lithium-like system, a resonance can be formed in the following way ... 

The basic thermodynamic and electrochemical kinetic concepts involved in batteries and the parameters used to evaluate their performance are summarized in Section 2.2. The most widespread primary and rechargeable systems are described by highlighting the most recent advances in Section 2.3. Supercapacitors and fuel cells, whose importance in the field of energy conversion is growing, are also briefly treated in this section. The lithium-based rechargeable systems, the most advanced batteries with the highest performance, are discussed in detail in Section 2.4, with particular emphasis on the new materials on which these batteries are based. 

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