【摘要】 设计具有快速传荷动力学的二氧化钛负极材料是进一步构建高能量功率密度混合离子电容器的关键所在.本文提出一个氧空位辅助二氧化钛高阴离子掺杂的策略,合成了高含量硫/硒/磷掺杂的二氧化钛负极材料.通过实验结果与理论计算相结合,本文系统地研究了氧空位辅助掺杂的可行性、硫掺杂对二氧化钛的影响以及二氧化钛负极材料倍率性能极大提升的深层次机理.研究发现,氧空位的引入可以使硫掺杂过程自发进行,高含量的硫掺杂在二氧化钛能带结构中引入S 2p,使得其能带间隙变小,导电率显著提升;同时,硫进入晶格后,离子的迁移能垒降低,离子迁移速率增加,传荷动力学提高.这项工作为实现阴离子的高含量掺杂和提升二氧化钛的电荷转移动力学提供了一种新的策略,为设计具有快速动力学的电极材料提供了行之有效的方法.更多还原

【Abstract】 The rate-determining process for sodium storage in TiO₂ is greatly depending on charge transfer happening in the electrode materials owing to its inferior diffusion coefficient and electronic conductivity.Apart from reducing the diffusion distance of ion/electron,the increasement of ionic/electronic mobility in the crystal lattice is also very important for charge transport.Here,an oxygen vacancy （OV） engineering assisted in high-content anion （S/Se/P） doping strategy to enhance charge transfer kinetics for ultrafast sodium-storage performance is proposed.Theoretical calculations indicate that OV-engineering evokes spontaneous S doping into the TiO₂ phase and achieves high dopant concentration to bring about impurity state electron donor and electronic delocalization over S occupied sites,which can largely reduce the migration barrier of Na⁺.To realize the speculation,high-content anion doped anatase TiO₂/C composites(9.82 at%for S in A-TiO_2–x-S/C) are elaborately designed.The optimized A-TiO_2–x-S/C anode exhibits extraordinarily high-rate capability with 209.6 mAh g^-1at 5000 mA g^-1.The assembled sodium ion capacitors deliver an ultrahigh energy density of 150.1 Wh kg^-1at a power density of 150 W kg^-1when applied as anode materials.This work provides a new strategy to realize high content anion doping concentration,and enhances the charge transfer kinetics for TiO₂,which delivers an efficient approach for the design of electrode materials with fast kinetic.更多还原