| Description | Lithium Batteries: From an Idea to Domination of
Portable Storage In 1967, solid materials were found that had ion transport behavior comparable to that ions in liquid solutions. This allowed the dream that alkali-metal based rechargeable batteries could be realized. Such batteries could use mixed conducting materials, i.e. where both ions and electrons are mobile and where non-stoichiometry is the norm (= no Dalton’s Law) as in the tungsten bronzes NaxWO3, or the layered sulfides, LixTiS2, where 0≤x≤1. These alkali ions could be readily intercalated into the lattices, with initial interest being in their optical, catalytic and superconducting behavior. However, in 1972 it was discovered that significant energy was released when K ions were intercalated into TaS2, and it was proposed that this could be harnessed in a battery. These intercalation reactions have been the basis of all rechargeable lithium batteries since their inception. However, commercial cells still attain only 25% of their theoretical energy densities (volumetric or gravimetric). The dominant NMCA cathodes can now attain over 200 Wh/kg commercially at the cell level, and the Battery500 consortium has attained around 350 Wh/kg in full cells, out of a theoretical 1000 Wh/kg. The challenges to achieving higher levels are many; these will be discussed. |
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