Nanostructured Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> Anodes: Delineating the Impact of Morphology, Exposed Facets, and Phase Purity on the Performance
Supriya Pal, Sabyasachi Roy, Prajna Jalagam, Pratyay Basak
Abstract
Nanostructured lithium titanate (LTO, Li4Ti5O12) has garnered immense attention as a prospective anode material that can sustain high charge–discharge rates, offer prolonged cycle life, and particularly address the concerns regarding battery safety. In our present research effort, an attempt is made toward gathering evidence for an in-depth comparative appraisal of discrete LTO samples synthesized by different routes under controlled conditions yielding diverse particle morphology. Two commercial samples, nano-LTO and submicron-sized LTO along with Super-P and polyvinylidene fluoride (PVdF), are used as reference materials for the assessment. Comprehensive electrochemical evaluation of the electrodes prepared employing both commercially available as well as synthesized LTO samples is carried out to assess the specific capacity, rate adaptability, Coulombic efficiency, capacity retention, and cyclic stability over multiple (>250 cycles) charge/discharge cycles. X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), and high-resolution transmission electron microscopy (HRTEM) studies performed on the commercial and synthesized samples lead to some interesting observations and yielded crucial clues toward understanding the observations noted in the electrochemical studies. The findings supported by detailed physicochemical characterizations of the materials substantiate the dominating impact of the particle morphology and % of exposed facets along with the nature of the minor phase present on the overall electrode performance given that all of the other parameters, such as particle size, crystallinity, and phase purity, were held similar to an appreciable degree. Our studies evidently suggest that hierarchical LTO assemblies of nanostructured primary particles, which tender the substantial presence of the (001) plane as the exposed facet coupled with the presence of an optimal amount of rutile as the minor phase, can possibly offer excellent electrode performance, notably without the additional carbon coating or use of multivalent dopants extended as alternate strategies.