Extracting the Full Potential of Single‐Walled Carbon Nanotubes as Durable Supercapacitor Electrodes Operable at 4 V with High Power and Energy Density

Ultrahigh‐Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron‐Correlated Oxides

“…Despite slight decrease of the volumetric capacitance with the increase of the current density up to up to 312 A cm −3 , the NP V 2 O 3 /MnO 2 based pseudocapacitor can sustain high volumetric capacitances at ultrafast charge/discharge rates, which are ≈2–5 times higher than the best values reported for EDLCs based on the chemically converted graphene (CCG) films with a high packing density of 1.33 g cm −3 (Figure 4c) 13. This excellent rate capability is also much better than those of other carbon materials, such as single‐walled carbon nanotubes/reduced graphene oxide (SWNT/rGO) fibers,11 graphene/carbon nanotube (graphene/CNT) carpet,12 SWNTs 14 or activated carbon (AC),14 and the pseudocapacitive Ni(OH) 2 supported by NP Ni skeleton [NP Ni/Ni(OH) 2 ] 55, 56…”

“…Unlike electrochemical double‐layer capacitors (EDLCs),8, 9, 10, 11, 12 in which charge storage is achieved by nonfaradaic electrostatic adsorption in nanostructured carbons with low intrinsic capacitance (≈20 μF cm −2 carbon ),1, 13, 14 pseudocapacitors store high‐density energy on pseudocapacitive materials by fast and reversible surface redox reactions at or near the electrode/electrolyte interface 1, 2, 3, 4, 5, 6, 7, 15, 16, 17. The surface mechanisms are fundamentally distinguished from rate‐limited volumetric reactions in batteries by short charge/discharge time, high power density and long‐term cycling stability 1, 2, 3, 18.…”

“…It thus remains a primarily challenge in realizing high‐power and high‐energy densities in pseudocapacitors, which requires pseudocapacitive electrode materials simultaneously providing large specific surface area and ultrahigh transports of ions and electrons 22, 23, 24. In this regard, controlling nanostructures and exploring novel materials have become critical processes to meet these requirements in developing TMO‐based composite electrodes,1, 6, 17, 23, 25 wherein various conductive materials, including nanostructured carbons (such as porous carbon,14, 26 carbon nanotubes,27, 28, 29, 30 and graphene 31, 32) and conducting polymers, are extensively employed to serve as electron pathways. Although the large specific surface area in these low‐dimensional composite nanostructures allows ion transports,1, 17, 23, 26, 27, 28, 29, 30, 31, 32 their assembled bulk electrodes usually exhibit high electrical resistance as a result of the short electron transport distance within these low‐dimensional conductive materials, the undesirably high contact resistances produced by the coating of electrically insulating active TMOs and polymer binders, as well as the weak and noncoherent TMO/conductor interfaces 24, 33, 34, 35.…”

Carbon nanotubes prepared by anodic aluminum oxide template method

“…Carbon nanotubes (CNTs) with unique structure and properties such as well-defined hollow interiors, inert surface properties, and resistance to acid and base environment have been proven to be excellent candidates as support in catalytic reactions [1][2][3][4][5][6][7] and energy storage and conversion medium [8][9][10][11]. Structural parameters of CNTs such as inner diameter, wall thickness, length, crystallinity, and electronic structure have a great influence on the performance of the supported particles or loaded matters [12][13][14][15].…”

Enormous shrinkage of carbon nanotubes by supersonic stress and low-acceleration electron beam irradiation

“…Therefore, the artificial decoration of the SWCNT surface with a functional group 6,7 drastically increases the surface area, up to 1300 m 2 /g, and the performance (energy density of 94 Wh/kg and power density of 210 kW/kg) almost reaches their ideal values. 8 Despite such superior characteristics of a CNT-based supercapacitor, further improvement of its storage density is required for practical applications such as electrical vehicles.…”