Rapid fabrication of thick spray-layer-by-layer carbon nanotube electrodes for high power and energy devices

Abstract

Rapid fabrication of layer-by-layer (LbL) electrodes is essential to expand their utility in energy storage applications. Herein, we address challenges in developing thick LbL electrodes of multi-wall carbon nanotubes (MWNTs) using conventional dip-and spray-LbL processes, and present a solution to overcome these challenges. The vacuum-assisted spray-LbL process using porous carbon substrates enabled a linear growth of LbL-MWNT electrodes with a 600 time decrease in their fabrication time.This result was attributed to the enhanced surface interactions between MWNTs and substrate via increased surface areas, enhanced capillary forces, physical entrapment in pores, and changes in hydrodynamic drag forces. Scanning electron microscopy (SEM) revealed high surface area carbon nanotube networks comprised of individual MWNT's. The spray MWNT electrodes delivered a high gravimetric energy of 100 W h kg À1 at high gravimetric power of 50 kW kg À1 , which is higher than those of most carbon nanotube electrodes reported. Moreover, the spray MWNT electrodes delivered the highest energy capacity per unit area (up to 300 mW h cm À2 at 0.4 mW cm À2 among the LbL electrodes reported, and showed excellent retention of energy capacity up to 100 mW h cm À2 at high power capacity of 200 mW cm À2 . These performance values are higher or comparable to the most advanced battery electrodes for high energy capacity per unit area. Broader contextWith emerging applications of Li-ion batteries such as electrical vehicles, load-leveling, and new electronic devices, the demand for improving both the gravimetric and areal energy and power output of battery electrodes is ever increasing. Although the previously reported battery electrodes assembled via layerby-layer (LbL) assembly have been shown to provide high gravimetric energy and power densities, the LbL electrodes deliver only limited total energy (per area) because of the long fabrication time required by traditional LbL processes. In this work, we demonstrate a rapid fabrication of thick LbL electrodes of multi-wall carbon nanotubes (MWNTs) via the modied spray-LbL method; the fabrication time decreased 600 times compared with traditional processes. The spray LbL-MWNT electrode showed both high gravimetric energy (100 W h kg electrode À1 ) and areal energy (100 mW h cm À2 ) without the expense of gravimetric or areal power density (50 kW kg electrode À1 or 200 mW cm À2 ). Our method can be easily expanded to different combinations of energy storage materials, substrates with different structures, and spray conditions, allowing us to efficiently fabricate novel energy storage electrodes via LbL assembly.

Fabrication and functionalization of carbon nanotube films for high-performance flexible supercapacitors

“…(Figure 2(d)) [35] The introduction of static charge effect further increased the efficiency in a certain extent for the fast and tied between individual CNTs. [17] Casting method is another way to prepare large-area flexible CNT films. (Figure 2(f) and (g)) Its typical process was shown in Figure 2(e).…”

Recent Progress in Layer-by-layer Assembly of Nanomaterials for Electrochemical Energy Storage Applications

“…LPEI, PAA). 6) This was attributed to the fact that, in the spray-LbL method, additional hydrodynamic forces act upon the highaspect-ratio nanotubes, pulling them away from the substrate and impeding the development of intimate contact between the incoming charged species and the substrate. Also, the short processing times for spray LbL (~15 sec) might not be enough to deposit mechanically stiff MWNTs, since their rearrangement or deformation under electrostatic interactions is limited compared to the soft polymers.…”

Spray‐Layer‐by‐Layer Carbon Nanotube/Electrospun Fiber Electrodes for Flexible Chemiresistive Sensor Applications

“…In addition, we have demonstrated the ability to construct multiwalled carbon nanotube (MWNT) multilayer films without binder on planar substrates and carbon paper using conventional dip-LbL [9] and spray-LbL [10] , repectively, to create electrodes for energy storage applications. These studies suggest that the LbL technique is well suited for depositing conformal MWNT films on porous ES fiber substrates.…”

“…were prepared as previously reported by reacting MWNT-COO − suspension (400 mL, 0.5 mg ml −1 ) with excess ethylenediamine (40 mL) in the presence of 4 g of [1][2][3]propyl]-3-ethylcarbodiimide methiodide [10]. The resulting suspension was also dialyzed for a few days to remove any residuals and byproducts.…”