Composite of LiFePO₄ with Titanium Phosphate Phases as Lithium-Ion Battery Electrode Material

We report the synthesis of LiFePO₄ (LFP) battery materials where during synthesis the iron has been substituted by up to 10 mol % with titanium. Analysis of the Ti-substituted materials revealed that at the substitution levels investigated, the Ti did not form a solid solution with the LFP, but rather minority phases containing Ti phosphates were formed and segregated at the nanoscopic scale. The minority phases were amorphous or not well-crystallized and accepted Li on first discharge in a lithium half cell, and solid state NMR spectra were consistent with one of the constituents being LiTi₂(PO₄)₃. The Ti substituted materials had increased electrochemical capacities and discharge voltages relative to LFP prepared in an equivalent process, and the ability to accept Li on first discharge may find utility in using previously inaccessible capacity in battery cathode formulations and in balancing excess capacity from high energy cathode materials.