Densely Packed 3D Corrugated Papery Electrodes as Polysulfide Reservoirs for Lithium–Sulfur Battery with Ultrahigh Volumetric Capacity

Abstract

Designing the optimum cathode configuration for lithium−sulfur (Li−S) batteries has held tremendous scientific momentum to achieve high energy density, fast reaction kinetics, and superior cycle retention. Herein, a self-standing and flexible PPy@rGO/CNTs (PCG) paper as sulfur host is constructed by integrating multiwalled carbon nanotubes into polypyrrole@reduced graphene oxide hybrid structure, rooted from in situ redox reaction and spontaneous assembly of pyrrole and graphene oxide. The three-dimensional (3D) corrugated papery frameworks with carbon nanotube (CNT) pillars deliver a highly conducting pathway for electron and ion transfer. Theoretical calculations indicate that ample nitrogen-and oxygen-containing functional groups can form strong polar−polar interaction with lithium polysulfides. Thus, the assembled lightweight PCG-S electrode exhibits a high gravimetric capacity of 1201.9 mA h g −1 and retains 727.8 mA h g −1 at 0.2 C after 450 cycles, remarkable rate performance, and excellent cyclic stability with an ultralow decay rate of 0.044% per cycle during 200 cycles at 1 C. Delightedly, thanks to its unique structure, the volumetric sulfur loading amount in the flexible electrode can reach ca. 0.82 g cm −3 , which endows the cathode with an ultrahigh volumetric capacity of 975 A h L −1 at 0.2 C simultaneously. This dense monolithic paper appears to be a scalable potential for developing high-performance cathodes in emerging flexible devices.

Highly Packed Monodisperse Porous Carbon Microspheres for Energy Storage in Supercapacitors and Li−S Batteries

“…While the sulfur content should be as high as possible in order to beat current Li‐ion battery technology, the ideal sulfur host must provide enough space for the volume changes that occur during lithiation and delithiation while avoiding large unoccupied spaces. Several S/C cathodes with graphene‐based architectures have shown ground‐breaking values of volumetric capacity, but they are not compatible with the mature industry based on the roll‐to‐roll manufacture of electrodes composed of active material, conducting additive and binder …”

Carbon Nanomaterials Embedded in Conductive Polymers: A State of the Art

“…In this line, Liu and co-workers fabricated a conductive paper with CNTs and SnS@PPy-nanobelts as building blocks by in situ polymerization of PPy on SnS nanobelt substrate and subsequent mixing with CNTs and filtration [ 240 ]. Similarly, as represented in Figure 14 , a self-standing and flexible PPy@rGO/CNTs (PCG) paper was constructed by filtration after integrating CNTs into PPy@reduced graphene oxide hybrid structure, rooted from in situ redox reaction and spontaneous assembly of pyrrole and graphene oxide [ 38 ].…”

“…The main limitation is the low sulfur loading achieved so far. Therefore, CNT networks on flexible substrates and embedded with CP have been used as hosts for high sulfur loading, while keeping the flexibility and providing high conductive electron pathways [ 38 ]. Going a step further, Zhang and co-workers designed 3D electrodes composed of carbon foam/CNTs and filled with PEDOT (NCF/CNT/PEDOT@S), which demonstrated significant achievements at various bending angles after being assembled into multiple flexible Li–S batteries, as shown in Figure 17 [ 241 ].…”

“…Since then, many studies have regarded this polymer, enunciating its stability in air, high conductivity and the ease of obtaining it [ 31 , 32 , 33 , 34 , 35 ]. Nowadays PPy is used in many fields, including in solar cells, biomedical applications, and energy storage, but its two main applications are in electronic devices and sensors [ 36 , 37 , 38 , 39 , 40 ]. The physical aspects of PPy are variable depending on the synthetic route used to obtain it and the final application; films, nanospheres, and nanowires are some examples of the possible final structures of PPy [ 32 ].…”

Free‐Standing Nanostructured Architecture as a Promising Platform for High‐Performance Lithium–Sulfur Batteries

“…The resultant sulfur cathode exhibited a high discharge capacity of 488 mAh g −1 under the areal sulfur loading of 5.4 mg cm −2 . [ 19 ] In addition, metal oxide (titanium monoxide) nanoparticles are also popular spacers, which can not only prevent the aggregation of graphene sheets but also suppress the migration of polysulfides due to their strong adsorption ability. [ 20 ] Unfortunately, the introduction of these spacers in the graphene films would increase the inactive mass of graphene‐based sulfur electrodes, which may decrease the overall energy density of batteries.…”