Classification of Lithium Alloy Systems

Lithium reacts with numerous metals M (M = Mg, Ca, Al, Si, Ge, Sn, Pb, As, Sb, Bi, Pt, Ag, Au, Zn, Cd, Hg, etc.) at room temperature if the metal is polarized to adequate potentials in organic electrol de containing lithium ions. The cell reaction of so-called lithium alloys can be expressed according to the following equation  

Cycle performance of typical conventional lithium alloy electrode (A) Potential profile ofSi at initial charge/dischai e process, (B) Capacity retention during cycling for Si and C electrodes. 

There seems to be a limit to improve the cycle performance by only adjusting the alloy composition and their structures. The idea or breakthrough to control the swelling of these alloy systems and improve their cycle performance is given in the later part of the chapter. 

Lithium can react with metals and intermetallic compounds, for example, binary systems in various ways. 4,i35,i36 

In this reaction, inactive element M is extruded from intermetallic compound during the first charging process, leading to a finely dispersed complex matrix structure. Lithium reacts with finely dispersed nanoparticle M thereafter. In this case, though the cycle performance can be improved to some extent, the volume change of the lithium-active element M is not easily relieved. Examples are FeSi and NiSi.  

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