Preparation of Micron‐Sized Li4Ti5 O 12 and Its Electrochemistry in Polyacrylonitrile Electrolyte‐Based Lithium Cells

Micron-sized Li 4 Ti 5 O 12 was prepared in a single-step solid-state reaction involving TiO 2 and Li 2 CO 3 , and its electrochemical behavior was evaluated in Li and Li-ion cells containing a polyacrylonitrile (PAN)-based solid polymer electrolyte. The usefulness of Li 4 Ti 5 O 12 was demonstrated for three distinctive applications: (i) cathode of a 1.5 V rechargeable Li battery, (ii) auxiliary electrode for investigating the electrochemistry of Li insertion cathode materials, and (iii) anode of a Li-ion cell in conjunction with a high voltage cathode, e.g., cubic spinel LiMn 2 O 4 . The micron-sized Li 4 Ti 5 O 12 exhibited a capacity of 160 mAh/g at C/20-C/30 rates which is about 7% better than the capacity exhibited by this material prepared according to a previously published procedure. More importantly, the micron-sized oxide showed significantly better high rate capability, yielding 25-50% larger capacity at the 3C to 8C rates. Li/solid polymer electrolyte//Li 4 Ti 5 O 12 cells underwent extended, ull-depth, charge/discharge cycling at≥1C rates with virtually no capacity fade. The auxiliary electrode concept was demonstrated in Li (4+x) Ti 5 O 12 (x∼ 1.2)//solid polymer electrolyte//LiMn 2 O 4 cells. At a 1C discharge rate, more than 150 cycles were demonstrate in these cells with a capacity fade rate of about 0.1% per cycle and an end utilization of ∼90 mAh/g for spinel LiMn 2 O 4 . Balanced Li 4 Ti 5 O 12 //solid polymer electrolyte//LiMn 2 O 4 cells of slightly cathode-limited configuration showed full-depth extended cycling capability at a utilization of ∼90 mAh/g for LiMn 2 O 4 at 1C rate and a capacity fade rate of about 0.08% per cycle. The capacity fade in the LiMn 2 O 4 -containing cells appears to come from this cathode. When fully packaged, specific energy of the Li//PAN electrolyte//Li 4 Ti 5 O 12 cell would be about 57 Wh/kg and that of the Li 4 Ti 5 O 12 //PAN electrolyte//LiMn 2 O 4 cell is about 60 Wh/kg.