The formation and properties of amorphous silicon as negative electrode reactant in lithium systems

Essentially all of the present commercial rechargeable lithium batteries use lithium-carbons as the negative electrode reactant. However, the announcement of Fujifilm in 1997 of the potential use of convertible oxides called attention to the possibility of alternatives, and a variety of different materials and approaches has been investigated in an number of laboratories. Recent work on the potential of the use of metal–metalloid alloys has led to the recognition of several potentially attractive possibilities. Among the most interesting are a group of materials containing silicon, a boro-silicide, several silicides, and SiO. In all of these cases an irreversible reaction takes place during the first lithium loading. The result is the formation of fine particles of amorphous elemental silicon in a matrix related to the precursor. Upon further cycling, lithium reversibly reacts with this amorphous silicon. The resulting specific capacities can reach attractive values, depending upon the weight of the precursor. Their relatively flat potential profiles at low potentials make them of interest for application as negative electrodes.