负载Cr_2O_3的H_2Ti_2O_5·H_2O纳米管的制备及其作为锂离子电池正极材料的电化学性能

Preparation and Electrochemical Performance of H_2Ti_2O_5·H_2O/Cr_2O_3 Nanotubes as Anode Materials for Lithium-Ion Batteries

限制纳米电极材料倍率性能的一个重要因素是,在大电流下充放电时,纳米结构可能坍塌,造成容量迅速衰减.通过异价离子的掺杂或第二相的负载有可能弥补纳米材料的这一缺陷.本文以含有Cr2O3的锐钛矿TiO2为原料,通过超声化学-水热法,制备了负载Cr2O3的H2Ti2O5·H2O纳米管.采用X射线衍射(XRD)和透射电镜(TEM)对制得的H2Ti2O5·H2O/Cr2O3纳米管的晶体结构和微观形貌进行了表征和分析.恒流充放电测试显示,H2Ti2O5·H2O/Cr2O3(5%(w,质量分数))纳米管作为锂离子电池阳极材料具有优异的循环稳定性及倍率性能.在150mA·g-1的电流密度下,H2Ti2O5·H2O/Cr2O3纳米管的首次放电容量达到288mAh·g-1;120次循环后,充放电容量仍保持在145mAh·g-1.在1500mA·g-1的电流密度下,首次放电容量为178mAh·g-1;600次循环后,充放电容量保持在80mAh·g-1以上;继续在150mA·g-1电流密度下充放电30个循环,充放电容量达到155mAh·g-1,显示出充放电容量的可回复性.循环伏安测试结果表明,H2Ti2O5·H2O/Cr2O3纳米管的充放电过程由法拉第赝电容反应控制.该一维纳米结构在锂离子电池和非对称电容器领域显示出良好的应用前景.

One problem that limits the rate capabilities of lithium-ion batteries is that despite the small size of the nanocrystalline particles in the electrode material, the crystalline structure might collapse during repetitive Li ＋ intercalation and extraction leading to the deterioration of charge and discharge performance under high currents. The prevention of this destruction has been attempted by substituting constituent atoms with other atoms to stabilize the structure in various transition metal oxide systems. In this work, H2Ti2O5·H2O/Cr2O3 compounds with nanotubes morphology were prepared by low temperature alkali-hydrothermal processing from anatase-type TiO2 with the addition of 5% （w） Cr2O3. The crystal structure and morphology of the as-prepared H2Ti2O5·H2O/Cr2O3 nanotubes were investigated by X-ray diffraction and transmission electron microscopy, respectively. Electrochemical lithium insertion cycling tests showed excellent cycling stability and an improved rate capability. The capacity of the first cycle was 288 mAh·g-1, and over 145 mAh·g-1 capacity remained after 120 cycles at 150 mA·g-1. At a current of 1500 mA·g-1, the capacity of the first cycle was 178 mAh·g-1. Over 80 mAh·g-1 capacity remained after 600 cycles at 1500 mA·g-1; furthermore, the capacity could come back to 150 mAh·g-1 at 150 mA·g-1 after 600 cycles at 1500 mA·g-1, which was close to the result for the cell that was immediately discharged/charged at 150 mA·g-1. The Cr2O3 particles, as the second phase, can improve the structural stability and high-rate capability of the H2Ti2O5·H2O nanotubes. These novelone-dimensional nanostructured materials may find promising applications in lithium-ion batteries and in electrochemical cells.