Magnesium insertion into A0.5Ti2(PO4)3 (A=Mg, Ca, Sr, Ba)

A series of alkaline earth titanium phosphates, A(0.5)Ti(2)(PO4)(3) (A=Mg, Ca, Sr, Ba), were prepared by sot-gel method and evaluated as a cathode material for magnesium cells in propylene carbonate. Electrochemical magnesium insertion was found possible up to one magnesium per unit formulae at a low current density. The limit of electrochemical magnesium insertion decreased remarkably with increasing the current density, which suggested that the insertion limit is controlled by the low mobility of Mg2+ in these hosts. A large unit cell volume was considered as an important factor to realize fast Mg2+ transport in these phosphates and the rate-independent electrochemical insertion limit.