Li3Ti4NiMnO12 and Li3Ti4NiCrO12: New substituted lithium titanium oxides

The substitution Ti4+ + Li+ = Ni2+ + M3+ (M = Mn or Cr) has been tested in the spinel-type lithium titanium oxide Li4Ti5O12. The single-phase materials Li3Ti4NiMnO12 and Li3Ti4NiCrO12 have been synthesized by a modified sol-gel procedure and characterized by different techniques. X-ray diffraction indicates that the two materials crystallize in the typical Fd (3) over barm space group, and Li3Ti4NiMnO12 contains more heavy ions (likely, Mn3+) in the tetrahedral sites than Li3Ti4NiCrO12. Li3Ti4NiMnO12 shows a two-step reduction profile in the voltage range 0.5-2.5 V vs. Li/Li+ while Li3Ti4NiCrO12 shows a reduction profile typical for Li4Ti5O12. Initial discharge capacities close to the theoretical capacities were observed for both materials with considerable capacity retention on cycling. Due to smaller mean particle size and higher electronic conductivity of Li3Ti4NiCrO12, the material shows an improved rate capability compared with unsubstituted Li4Ti5O12. (C) 2013 Elsevier Masson SAS. All rights reserved.