Lithium Titanate Anode Material for Lithium Ion Energy Storage Battery

Compared with carbon anode materials widely used in lithium-ion batteries, spinel structure lithium titanate (Li4Ti5O12) anode materials have almost no structural changes in the process of lithium ion intercalation and deintercalation, and have good safety and excellent circulation. Performance is one of the first choice anode materials for long-life energy storage lithium-ion batteries. However, lithium titanate itself has poor conductivity and poor high-rate performance. In order to improve its lithium storage kinetics, it is usually used to nano-nanostructure and carbon coating. However, in this way, the same solid electrolyte interface film (SEI) as the conventional carbon anode material is formed at the electrode/electrolyte interface, which may cause interface problems and affect safety.

With the support of the National Natural Science Foundation of China, the Ministry of Science and Technology and the Chinese Academy of Sciences, researchers from the Key Laboratory of Molecular Nanostructures and Nanotechnology Institute of the Institute of Chemistry, Chinese Academy of Sciences are developing novel non-carbon inorganic materials coated with lithium titanate nanomaterials. New progress has been made in interface stability and rate performance. The results of the study are published in full text on J. Am. Chem. Soc., (2012, 134, 7874−7879).

The researchers synthesized a high-quality lithium titanate nanosheet anode material (LTO-600) and a lithium titanate nanosheet anode material coated with rutile TiO2 on the side by regulating the Li:Ti charging ratio in the hydrothermal reaction (LTO-RT- 600). They collaborated with researchers from the Institute of Physics of the Chinese Academy of Sciences and Japanese researchers to directly observe atomic resolution images through spherical aberration-corrected transmission electron microscopy (STEM), demonstrating that 1 nm-thick rutile TiO2 is indeed grown in-situ along the Li4Ti5O12 [001] direction. Coating (Figure 1).

Fig. 1 STEM photograph of rutile TiO2-coated lithium titanate nanoplates (LTO-RT-600) on the side

Electrochemical performance tests show that after the rutile TiO2 coating, the polarization of lithium titanate anode material is reduced, and the specific capacity, high rate performance, and cycle stability are significantly improved (Fig. 2). At 1C, the specific capacity is 178 mA hg−1. Even at 60C, the specific capacity of 110 mA hg−1 is 10 times higher than before coating. In order to reveal the reasons for the improvement of performance, they found that after the rutile TiO2 coating, the interface charge transfer resistance of the electrode material system was reduced by half, and the transmission capacity of Li was increased by 10 times. Careful research and analysis have found that the high efficiency of this coating lies in that rutile TiO2 only exists on the side and does not completely coat the lithium titanate nanosheets, so it does not hinder the transport of lithium ions along the [110] direction of Li4Ti5O12.

Fig. 2 Comparison of electrochemical properties of lithium titanate anode material before and after rutile TiO2 coating

In addition, because rutile TiO2 also has lithium storage activity within the lithium titanate operating voltage range, LixTiO2 with higher Li+/e-conductivity can be formed, and the mass transfer process at the lithium titanate-electrolyte interface can be improved. These findings not only deepen the understanding of non-stoichiometric lithium titanate anode materials, but also provide new ideas for the development of new high-efficiency, high-security electrode coating materials and coating methods.