Alloying:

• Alloying - insertion of Li into the crystal structure of the electrodes
• Dealloying - extraction of Li
• The lithium ions are added to the reactant phase, the reaction can be described as:

                                          Li + xM ⇔ LiMx 

• The reactant M can be an element or a compound.
• Depending on whether or not a phase transformation takes place, these reactions can be further divided into two types as 

                               (1) solid-solution reaction and

                               (2) addition reaction.

• In a solid-solution reaction, no phase or structure change occurs in the reactant M when Li enters into its framework structure (that is a topotactic reaction). 
• In an addition reaction the phase structure of the lithiated LiMx is different from the parent phase M; thus, the reaction involves phase change from M to LiMx.
• Li insertion/extraction in crystalline Si, Sn, Al and Sb are considered as addition reactions because of the very limited solubility of lithium in these elements.
• The reactions of Li with Mg and amorphous Si are regarded as solid-solution reactions.
• The purpose of using compound alloys is to create a Li-insertion host that maintains a strong structural relationship with the intermediate and the lithiated phases to minimize the volume expansion during reaction.
• The voltage curves of smaller alloy particles tend to be round-shaped.
• Alloy anodes have been considered as one of the most promising electrode materials for next-generation lithium-ion batteries due to their high energy densities, relatively low cost, environmental compatibility and safe operation potentials.
• The disadvantages of alloy anodes include their short cycle life and high irreversible capacity loss as a result of the large volume expansion during lithium insertion.
• Alloying active elements with inactive elements can reduce volume expansion, leading to improved cycle life and it also maximize the energy density.

Conversion Mechanism:

• Conversion reactions are lithiation reactions in which the active material is fully reduced by lithium to the metal according to the following equation

                                               Mz+Xy + zLi → M0 + yLiz/yX

                              where M stands for a cation and X an anion.

• When discharged, the conversion reaction anodes such as metal oxide (MOx) react with Li+ ions and form metal nano-domains (M0) dispersed in the Li2O matrix.
• Then, during charging steps, the M0 and Li2O components are converted into the metal oxide (MOx).
• In conversion mechanism, decomposition and formation process takes place.

Displacement Mechanism:

• In displacement reaction, lithium reacts with one component M of an alloy compound MNy while the other component N is displaced or extruded from the parent phase.
• The displaced element N can be inactive or active towards lithium. For the N-inactive compounds such as Cu6Sn5, CrSb2, SnO or Sn2Fe, the reaction can be written generally as:

                                 Li + xMNy → LiMx + xyN

• Some displacement reactions are not reversible, and the extruded component N does not participate in the subsequent reaction cycles but acts as a buffering matrix. 
• When the displaced component N in reaction is active, it reacts with lithium at a potential lower than that for element M. This reaction can be considered as a displacement reaction plus an addition reaction for element N.
• The active/active alloy examples include SnSb, InSb and Mg2Si. Many active/active displacement reactions are not completely reversible in later cycles and the two active components react with lithium independently as separate addition reactions.