Alkali hexatitanates—A2Ti6O13 (A = Na, K) as host structure for reversible lithium insertion

Electrochemical lithium insertion into two isostructural titanium-based oxides, K2Ti6O13 and Na2Ti6O13 has been investigated. Although the two compounds differ mainly from their particle size and cell volume, pronounced differences in the insertion mechanism have been evidenced. They can accommodate about three Li per formula unit at relatively low potentials (1.5–0.9 V versus Li reference), which qualifies them as potential alternatives to Li4Ti5O12. The main limitations are their rate capabilities and capacity retention related to large particles and parasitic electrolyte decomposition, respectively.