碳布负载的缺氧型Na2Ti3O7纳米带阵列作为高性能柔性钠离子电池负极材料

摘要

作为锂离子电池的理想替代品,钠离子电池因具有能源储备丰富、成本低廉等优点而受到人们的广泛关注.柔性便携式电子产品的发展亟需柔性储能器件的研制.因此,发展一种廉价、高性能的柔性钠离子电池负极材料成了科研工作者的共同目标.在此项工作中,我们通过简单的水热合成和热还原法发展了一种以柔性碳布为基底,与缺氧型的Na2Ti3O7纳米带(NTO)构成三维阵列结构的新型柔性钠离子电池负极材料.复合材料(R-NTO/CC)的导电性和活性位点得到提高,电化学性能也大幅提升,在200 mA·cm?2的电流密度下,实现100 mAh·cm?2的面积比容量,且经过200次循环后仍保留最初电容值的80%.此外,这种电极还具有优良的倍率性能,当电流密度提高到400 mA·cm?2时,仍保持69.7 mAh·cm?2的面积比容量,是未引入氧空位材料的三倍之多.这种三维缺氧的电极材料可有效提高载流子浓度,缩短离子传输通道,从而大幅提升电极的电化学性能.此工作为设计合成高储钠性能的新型的负极材料提供了一种实用有效的策略.%Sodium ion batteries (SIBs), a promising substitute for lithium ion batteries (LIBs), have attracted extensive attention due to the abundance and low cost of sodium resources. In addition, flexible sodium-ion batteries may be able to satisfy the demands of large-scale energy storage applications for portable, wearable, and flexible electronics. Compared to the development of cathode materials, the progress on anode materials has been relatively slow. Therefore, the exploration of low-cost anode materials with high Na+storage capacity is very important. Herein, we present oxygen-deficient Na2Ti3O7nanobelts grown on carbon cloth (CC) as a promising novel flexible anode material for SIBs. Free-standing Na2Ti3O7nanobelts with oxygen vacancies were directly grown on CC through a simple hydrothermal and thermal reduction process. Benefiting from the improved conductivity and increased active sites after the introduction of oxygen vacancies, the new material exhibits a high reversible capacity of 100 mAh·cm?2at 200 mA·cm?2, with almost 80% capacitance retention after 200 cycles. When the current density was increased to 400 mA·cm?2, a high capacity of 69.7 mAh·cm?2was achieved, which is three times that of bare Na2Ti3O7nanobelts on CC. This 3D oxygen-deficient electrode can significantly promote the transport of Na+ions and electrons, leading to remarkably improved electrochemical properties. Furthermore, this work constitutes a promising strategy to rationally design and fabricate novel Na2Ti3O7-based anodes with enhanced capacitive behavior, which hold great promise for energy storage/conversion devices, facilitating the large-scale implementation of high-performance flexible SIBs.