Layered alkali rhodium oxides A<inf>x</inf>RhO<inf>2</inf>: Topotactic solvation, exchange, and redox reactions

The intercalation/deintercalation properties of the layered oxides LiRhO2, NaRhO2, and KRhO2 have been investigated with respect to redox and exchange processes. The chemical reactivity was found to be strongly dependent upon the alkali cation. Only KRhO2 is able to form hydrated phases and to undergo quantitative K+ H+ exchange, resulting in the formation of the new layered hydrogen bronze HRhO2. HRhO2 has a limited phase range up to H1.1RhO2 and exhibits no Brönsted acid character. LiRhO2 and NaRhO2 both show a limited cycling range in aprotic Li+ or Na+ electrolytes beyond which irreversible lattice disorder is observed. The origin of the significant differences in topotactic reactivity between layered dichalcogenide and oxide systems is discussed. © 1987.