High-Performance Two-Ply Yarn Supercapacitors Based on Carbon Nanotube Yarns Dotted with Co₃O₄and NiO Nanoparticles

Abstract

Yarn supercapacitors are promising power sources for flexible electronic applications that require conventional fabric-like durability and wearer comfort. Carbon nanotube (CNT) yarn is an attractive choice for constructing yarn supercapacitors used in wearable textiles because of its high strength and flexibility. However, low capacitance and energy density limits the use of pure CNT yarn in wearable high-energy density devices. Here, transitional metal oxide pseudocapacitive materials NiO and Co3 O4 are deposited on as-spun CNT yarn surface using a simple electrodeposition process. The Co3 O4 deposited on the CNT yarn surface forms a uniform hybridized CNT@Co3 O4 layer. The two-ply supercapacitors formed from the CNT@Co3 O4 composite yarns display excellent electrochemical properties with very high capacitance of 52.6 mF cm(-2) and energy density of 1.10 μWh cm(-2) . The high performance two-ply CNT@Co3 O4 yarn supercapacitors are mechanically and electrochemically robust to meet the high performance requirements of power sources for wearable electronics.

A General Electrode Design Strategy for Flexible Fiber Micro‐Pseudocapacitors Combining Ultrahigh Energy and Power Delivery

“…Various carbonaceous materials like activated carbon,9, 10 carbon nanotubes (CNTs),11, 12, 13 reduced graphene oxide (rGO),14, 15, 16 and our recently developed rGO/CNT hybrids17, 18 were exploited as active materials for fiber m‐SCs, yet their applications are restricted by the low capacitance of <200 mF cm −2 . Alternatively, incorporating pseudocapacitive materials into fiber m‐SCs is a superior solution to achieve high‐density energy due to 10–100 times higher theoretical capacitance than carbon materials 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36. Due to the poor conductivity for pseudocapacitive materials, composite electrode design by depositing active materials on one‐dimensional (1D) conductive scaffolds including carbon‐based fibers19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or metal‐based wires,31, 32, 33, 34, 35, 36 was employed to improve the electron transport.…”

“…Alternatively, incorporating pseudocapacitive materials into fiber m‐SCs is a superior solution to achieve high‐density energy due to 10–100 times higher theoretical capacitance than carbon materials 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36. Due to the poor conductivity for pseudocapacitive materials, composite electrode design by depositing active materials on one‐dimensional (1D) conductive scaffolds including carbon‐based fibers19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or metal‐based wires,31, 32, 33, 34, 35, 36 was employed to improve the electron transport. Despite some progresses, the improvements in the areal energy density for these fiber m‐SCs are still too modest to cater for many practical requirements and often come at the expense of sacrificing their rate capability or power density 1, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36.…”

“…Due to the poor conductivity for pseudocapacitive materials, composite electrode design by depositing active materials on one‐dimensional (1D) conductive scaffolds including carbon‐based fibers19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or metal‐based wires,31, 32, 33, 34, 35, 36 was employed to improve the electron transport. Despite some progresses, the improvements in the areal energy density for these fiber m‐SCs are still too modest to cater for many practical requirements and often come at the expense of sacrificing their rate capability or power density 1, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36. This impedes their broad practical applications where both high power and energy densities are required.…”

“…The widely employed scaffolds in the literature are mainly carbonaceous fibers such as CNT yarns, rGO fibers, and their composite fibers. But their conductivity is unsatisfactory for long‐range electron transport along the fiber 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30. Unlike macroscopic planar SCs, effective long‐distance electron transport is highly required for fiber m‐SCs due to the lack of extra metal current collectors within slender fiber electrodes.…”

“…Unlike macroscopic planar SCs, effective long‐distance electron transport is highly required for fiber m‐SCs due to the lack of extra metal current collectors within slender fiber electrodes. However, such crucial design concern is often ignored in previous carbon‐based fiber m‐SCs, thus leading to a major bottleneck in performance (typically <200 mF cm −2 and <1 mW cm −2 ) 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30. As compared, metallic scaffold was recognized as the best candidate for long‐range electron transport 31, 32, 33, 34, 35, 36.…”