Influence of Li addition on charge/discharge behavior of spinel lithium titanate

This article provides proof of an efficient approach to adjust the behavior of Li(+) intercalation into Li(4)Ti(5)O(12) spinel structures prepared by spray-drying followed by solid-state calcination. The spherical Li(4)Ti(5)O(12) powders consist of a number of grains with an average size of 300-500 nm, showing high rate capability at various rates of 0.1-20 C. The addition of Li-ions greatly modifies the Li(4)Ti(5)O(12) crystallites with different relative intensity ratios of (3 1 1)/(4 0 0), R value, determined from X-ray diffraction results. The overall reversible capacity in the voltage range of 2.5-0.01 V vs. Li/Li(+) is limited by the vacant tetrahedral (8a) and octahedral (16c) sites. The decrease of capacity ratio of second plateau (1.0-0.01 V) to first plateau (2.5-1.0 V) with the R value proves that the ratio of site vacancy greatly affects the capacity contribution. At high C rates, the tetrahedral (8a) sites exhibit a better accessibility to accommodate Li-ions during the intercalation process, compared with the accessibility of octahedral (16c) sites. This extra capacity of Li(4)Ti(5)O(12), originating from the Li(+) insertion at low potential, facilitates not only an enhanced reversible capacity but also a wider working voltage, leading to a higher energy density for rechargeable Li-ion batteries. (C) 2010 Elsevier B.V. All rights reserved.