Preparation of lithium titanate nanoparticles assisted by an ion-exchange process and their electrochemical performance as anode materials for Li-ion batteries

Abstract

Spinel-structured lithium titanate (Li4Ti5O12, LTO) has received broad attention as a next-generation anode material for Li+-ion batteries because of its excellent safety and long cycle life. However, calcination at the high temperatures (>800 °C) is necessary to obtain spinel-phase LTO. This interferes the synthesis of LTO particles as nano-sized material which is advantageous for electrochemical performance. In this study, spinel-structured LTO nanoparticles were synthesized via an ion-exchange process in conjunction with a mild calcination temperature (600 °C). First, Li2TiO3 was prepared by calcination of a LiOH∙H2O/TiO2 (atomic ratio Li/Ti = 2) mixture at 600 °C. Second, the Li+ ions of the layered Li2TiO3 were partially exchanged with H+ ions in HCl solution, resulting in the synthesis of HxLi2−xTiO3 (0 <x<2). We investigated the effects of the H/Li ratio in the ion-exchange process of Li2TiO3 particles and the calcination temperature on the phase composition of the final product. The phases in the final product are sensitively determined by the conditions used in the ion-exchange reaction and subsequent calcination. Under the optimized conditions, spinel phase dominant LTO particles are synthesized by calcination at a low temperature (600 °C). Because of the mild calcination temperature, the crystal size and secondary particle size of the spinel-structured LTO are 23.9 nm and<1 µm, respectively. These particles show a high initial discharge capacity of 165.3 mAh g−1 at 1 C, excellent cyclic stability, and superior rate performance when used as an anode material in a Li+-ion battery. Therefore, the suggested synthetic process is advantageous for the production of nanostructured LTO electrode materials.