Synthesis and electrochemical properties of TiNb (PO4)3 cathode materials for lithium secondary batteries

Hexagonal TiNb(PO4)(3), a host framework structure, has been synthesized at various temperatures ranging from 200 to 1300 degreesC and systematically characterized. An optimum synthesis temperature of 1200 degreesC has been found to be suitable for a cathode material for lithium secondary batteries. The samples synthesized at 1100 and 1200 degreesC have shown fewer undesirable reaction products than the samples synthesized at 1000 or 1300 degreesC. Titanium niobium phosphate (TiNb(PO4)3), without any lithium in its structure, was used as a cathode for a lithium secondary battery and intercalation of lithium into the vacant sites of the sample was achieved electrochemically. Of the TiNb(PO4)(3) samples studied (1100, 1200 and 1300 degreesC, the sample synthesized at 1200 degreesC exhibits a better capacity of 147 mAh/g with a relatively high voltage. The discharge potential of this sample was found to be 2.3 V vs. lithium. In order to maximize cycle life and deliverable capacity, a safe voltage limit for this material has been determined. (C) 2003 Elsevier B.V. All rights reserved.