Effects of excess Li on the structure and electrochemical performance of Li1+zMnTiO4+δ cathode for Li-ion batteries

Abstract

Spinel-based LiMn2O4 is the most attractive cathode for Li-ion battery due to high voltage, low cost, and non-toxicity. The cycle life of the spinel cathodes could be improved by replacing Mn4+ with Ti4+ leading to the formation of new spinel cathode, LiMnTiO4. However, its application is restricted due to the associated loss in the specific capacity. In this work, spinel-layered Li1+zMnTiO4+δ (z = 0, 0.5, and 1.0; δ is the value to reflect the composite character of the material) cathodes were fabricated to achieve long cycle life, without compromising on the specific capacity. Cathodes with excess Li (z = 0.5 and 1.0) formed a spinel-layered composite structure with notation (1-a)LiMn2-xTixO4.aLi2MnyTi1-yO3 [y = 0.5–((1/a − 1)(1 − x))]. These cathodes exhibited an enhanced specific capacity of ∼218 mAh g−1 (20% higher), with a capacity retention of 94% after 60 cycles. The structural and electrochemical properties of these cathodes were investigated using X-ray diffraction, galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique to understand the mechanisms underlying the enhanced capacity and cycle stability. The effect of the Li-rich layered phase on the electrochemical performance of the Li1+zMnTiO4+δ cathodes was also investigated.