Li vs. Zn substitution in Li17Si4 – Li17– ε – δ Zn ε Si4 connecting the structures of Li21Si5 and Li17Si4

Abstract

Abstract Binary lithium silicides play a crucial role in high energy density anode materials for rechargeable batteries. During charging processes of Si anodes Li15Si4 is formed as a metastable phase which has been stabilized through Li by Mg, Zn and Al substitution. Here we investigate Li by Zn substitution in the lithium-richest phase Li17Si4 and report on the particular site preference of Zn atoms since Zn is substituting Li atoms only on one out of 13 possible lithium sites. This site preference shows an interesting relation to the closely related phase Li21Si5 and thus Li17− ε − δ Zn ε Si4 with ε = 0.025(1) and δ = 0.033(1) can be considered as the missing link between the structures of Li21Si5 (= Li4.20Si) and Li17Si4 (= Li4.25Si).