Cable‐Shaped Lithium–Sulfur Batteries Based on Nitrogen‐Doped Carbon/Carbon Nanotube Composite Yarns

Abstract

investigated carefully due to their strong mechanical properties and comprehensive orientational flexibility of one-dimensional (1D) architecture, [22] and 1D cable type devices can be bent into various shape and applied to electronic fabrics. [23] Cableshaped energy storage devices have been studied mostly due to their importance in electronic fabrics.The current cable-shaped lithium-ion batteries and supercapacitors, [24] however, cannot fully meet the requirements of practical applications due to the low energy density of electrode materials. [25] Lithium-sulfur (Li-S) batteries [26] with a theoretical energy density of 2600 Wh kg −1 and a specific capacity of 1675 mAh g −1 are emerging as a promising secondary battery system. [27] Sulfur as the active material possesses the advantages of low cost, abundant resources, and environmentally friendly behavior. [28,29] Although there are many reports on traditional flexible Li-S batteries, [30] the cable-shaped Li-S batteries with yarn structure cathode have been seldom reported up to date. Recently, typical cable-type Li-S batteries with high areal capacity and good flexibility were reported by Peng group. [31] They fabricated a device using a composite yarn cathode consisted of graphene oxide (GO)/mesoporous carbon (CMK-3)/ sulfur and current collector of carbon nanotube (CNTs) yarns made by chemical vapor deposition (CVD). The preparation of pure CNTs by CVD is complicated and costly. A simple method to fabricate the yarn cathode based on wet-spinning was reported by Kim et al. [22] Despite the better mechanical performance with the reduced graphene oxide/CNT/S cathode, the electrochemical performance of composite yarn cathode still needs to be improved for cable-shaped Li-S batteries. Thus, it is necessary to achieve yarn structure electrode with excellent electrochemical stability by simple approaches to assemble the cable-shaped Li-S batteries.Here, we have fabricated the cable-shaped Li-S batteries based on nitrogen-doped carbon/carbon nanotube/sulfur (NCNT/S) yarn cathode and further investigated its electrochemical performance. First, CNT [32] has outstanding mechanical and conductive properties and polyaniline (PANI) is a suitable choice as a source of nitrogen doping. The polyaniline/carbon nanotube (PANI/CNT) composite yarns were synthesized by the wetspinning approach (Figure 1a). The pure PANI/CNT yarns are shown in Figure 1b. To enhance the conductivity of PANI/CNT Cable-Shaped Batteries The research on flexible and wearable devices has attracted extensive attention in the last few years. Lithium-sulfur (Li-S) batteries are regarded as a promising option because of their high theoretical capacity and energy density. Here, cable-shaped Li-S batteries are developed based on a nitrogendoped carbon/carbon nanotube/sulfur (NCNT/S) composite cathode and lithium metal anode. The carbon nanotube (CNT) yarns with high conductivity and an appropriate amount of doped nitrogen are synthesized by wet-spinning followed by a carbonization process, and further act a...

Solutions to the Challenges of Lithium–Sulfur Batteries by Carbon Nanotubes

“…For instance, the sulfurloaded ring-like structure of MWCNTs has been established to promote electron transfer by the interconnected conductive network, as shown in Figure 11c. [110] Furthermore, cathodes in different forms (including 1D yarn, [111] 2D (freestanding) [103] Copyright 2020, American Chemical Society. b) Simulated configuration of CNTs with open rings created by thermal oxidation in air.…”

“…For instance, the sulfur‐loaded ring‐like structure of MWCNTs has been established to promote electron transfer by the interconnected conductive network, as shown in Figure 11c. [ 110 ] Furthermore, cathodes in different forms (including 1D yarn, [ 111 ] 2D (freestanding) films, [ 112 ] and 3D foams [ 113 ] /sponges [ 109a,114 ] /aerogels [ 115 ] ) have been prepared to not only improve the (cycling) performance of the cathode but also optimize the configuration of the batteries (such as eliminating the metal current collector [ 116 ] ). Superlong CNTs (2 mm in length) hybridized with graphene, for example, have been integrated with sulfur in fabricating freestanding cathodes with high mechanical strength (above 2 MPa at a strain of ≈10%).…”