Figure 1
From: Amorphous iron phosphate: potential host for various charge carrier ions
Schematic representation of alkali-ion insertion in crystalline and amorphous electrode hosts. The feasibility of inserting alkali ions (Li/Na/K) in crystalline (layered, spinel and olivine structured) and amorphous hosts has been presented in detail. Although the insertion of Li ions in the presented crystalline and amorphous hosts is feasible, the insertion of Na ions has only been demonstrated in layered-type cathodes. The feasibility of K-ion insertion in crystalline hosts is even more remote because of the relatively large size of the K-ion. The significance of amorphous hosts with short-range ordering is that these hosts facilitate the accommodation/transport of alkali ions irrespective of their sizes or possibly even charges.
