Yan Zhang1, Yuanye Huang1, Vesna Srot1, Peter A van Aken1, Joachim Maier1, Yan Yu2,3. 1. Max Planck Institute for Solid State Research, Stuttgart, 70569, Germany. 2. Hefei National Laboratory for Physical Sciences at the Microscale, Department of Materials Science and Engineering, Key Laboratory of Materials for Energy Conversion, Chinese Academy of Sciences (CAS), University of Science and Technology of China, Hefei, 230026, Anhui, People's Republic of China. yanyumse@ustc.edu.cn. 3. Dalian National Laboratory for Clean Energy (DNL), Chinese Academy of Sciences (CAS), Dalian, 116023, Liaoning, People's Republic of China. yanyumse@ustc.edu.cn.
Abstract
Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms. Usually, they suffer from low intrinsic electronic and ion conductivities of the active materials. Here, taking advantage of the combination of TiS2 decoration, sulfur doping, and a nanometer-sized structure, as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons, and exhibit enhanced pseudo-capacitively dominated capacities. At a scan rate of 0.5 mV s-1, a high pseudo-capacitive contribution (76% of the total storage) is obtained for the S-doped TiS2/TiO2/C electrode (termed as TiS2/S-TiO2/C). Such enhanced pseudo-capacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2. The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g-1 at a current density of 5000 mA g-1. The capacity maintains at high level (161 mAh g-1) even after 1500 cycles and is still characterized by 58 mAh g-1 at the extreme condition of 10,000 mA g-1 after 10,000 cycles.
Pseudo-capacitive mechanisms can provide higher energy densin class="Chemical">ties than electrical double-layer capacitors while being faster than bulk storage mechanisms. Usually, they suffer from low intrinsic electronic and ion conductivities of the active materials. Here, taking advantage of the combination of TiS2 decoration, sulfur doping, and a nanometer-sized structure, as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons, and exhibit enhanced pseudo-capacitively dominated capacities. At a scan rate of 0.5 mV s-1, a high pseudo-capacitive contribution (76% of the total storage) is obtained for the S-doped TiS2/TiO2/C electrode (termed as TiS2/S-TiO2/C). Such enhanced pseudo-capacitive activity allows rapid chemical kinetics and significantly improves the high-rate sodium storage performance of TiO2. The TiS2/S-TiO2/C composite electrode delivers a high capacity of 114 mAh g-1 at a current density of 5000 mA g-1. The capacity maintains at high level (161 mAh g-1) even after 1500 cycles and is still characterized by 58 mAh g-1 at the extreme condition of 10,000 mA g-1 after 10,000 cycles.