Preparation And Modification Of Mesoporous Spinel Li₄Ti₅O₁₂ Nanosheets As Anode Materials For Lithium-ion Batteries

Spinel Li4Ti5O12 (LTO), as a "zero-strain" material, has been intensively investigated as promising anode materials for lithium-ion batteries (LIBs) due to its high voltage plat, good cycle performance, low cost, remarkable structural stability, excellent safety, and so on. But, the low electron conductivity and lithium-ion diffusion coefficient greatly limit its practical applications. In order to improve the rate performance of the spinel LTO, we prepared the novel mesoporous spinel LTO nanosheets, and further modified the as-prepared mesoporous spinel LTO nanosheets.Firstly, the unique mesoporous spinel LTO nanosheets with excellent performances were prepared by a facial hydrothermal method. The experiment results indicated that the newly prepared spinel mesoporous LTO nanosheets demonstrated extra surface lithium storage reaction and excellent electrochemical performances, delivering high reversible capacity of 169 mAh/g at 1C and superior rate performance of more than 140 mAh/g at 30C between 1.0 and 2.5 V vs. Li+/Li. The beneficial surface lithium storage is mainly attributed to its advanced microstructure. The porous structure can offer rich channels for the sufficient interaction between active materials and electrolytes, which facilitates the transfer of lithium-ions and electrons, thereby leading to high capacity and excellent rate capability.In order to further improve the electrochemical performances of the mesoporous spinel LTO nanosheets, the as-prepared LTO samples were coated by highly dispersed nanosized Ag particles via a electroless deposition (ED) process. The Ag additive could increase the electronic conductivity of the LTO/Ag composite, and then in turn greatly improve the high-rate performance. Compared with the mesoporous spinel LTO nanosheets, the mesoporous LTO/Ag nanosheets demonstrated much improved electrochemical performances, delivering excellent reversible capacity of 174 mAh/g at 1C and outstanding rate performance of more than 145 mAh/g at 30C between 1.0 and 2.5 V vs. Li+/Li.In addition, TiO2 has been considered as promising host of lithium ions owe to its advantages of fast lithium insertion/extraction ability, lower volume change during the charge/discharge process and high theoretical capacity (336 mAh/g). We prepared a type of mesoporous LTO/rutile-TiO2 nanosheets with different molar ratio of Li and Ti by a hydrothermal method. Compared with the as-prepared mesoporous LTO/Ag nanosheets, the mesoporous LTO/rutile-TiO2 nanosheets demonstrated much more better electrochemical performances, delivering considerable reversible capacity of 179 mAh/g at 1C and brilliant rate performance of more than 150 mAh/g at 30C between 1.0 and 3.0 V vs. Li+/Li.