Nanofibers Comprising Interconnected Chain‐Like Hollow N‐Doped C Nanocages as 3D Free‐Standing Cathodes for Li–S Batteries with Super‐High Sulfur Content and Lean Electrolyte/Sulfur Ratio

Abstract

The development of a suitable cathode host that withstands high sulfur content/loading and low electrolyte/sulfur (E/S) ratio is particularly important for practically sustainable Li–S batteries. Herein, a facile approach is utilized to prepare free‐standing 3D cathode substrates comprising nitrogen‐doped carbon (N‐C) scaffold and metal–organic framework derived interconnected chain‐like hollow N‐C nanocages, forming a highly porous N‐C nanofiber (HP‐N‐CNF) framework. The N‐C skeleton provides highly conductive pathways for fast lithium ion/electron diffusion. The hollow interconnected N‐C nanocages not only offer enough space to absorb a high volume of active material but also effectively channelize severe volume stress during the electrochemical performance. The Li–S cell utilizing HP‐N‐CNF as cathode host displays exceptional battery parameters with high effective sulfur content (83.2 wt%), ultrahigh sulfur loading (14.3 mg cm–2), and low E/S ratio (6.8 μL mg–1). The Li–S cell exhibits a maximum areal capacity of 12.2 mAh cm–2 which stabilizes at ≈5.5 mAh cm–2 after the 130th cycle at 0.05 C‐rate and is well above the theoretical threshold. Therefore, the proposed unique nanostructure synthesis approach would open new frontiers for developing more realistic and sustainable host materials with feasible battery parameters for various energy storage applications.

Self-standing sulfur cathodes enabled by a single Fe site decorated fibrous membrane for durable lithium–sulfur batteries

“…It is worth noting that the discharge capacity of CNF increases obviously in the first few cycles, which should be related to the insufficient porosity and the incomplete infiltration of the catholyte. 19,38 The morphology of different components of the Li–S batteries after 100 cycles was also characterized by SEM. The structures of FeSA-PCNF are maintained well and Li 2 S is uniformly distributed over the whole nanofibers (Fig.…”

“…17 The unique one-dimensional nanofibers enable fast electron conduction for sulfur redox reactions. 18 Moreover, high porosity inside the nanofibers can be easily achieved with the addition of pore formers, such as sacrificial polymers or metal–organic frameworks, 19–21 which can not only physically adsorb LiPSs but also buffer volume variations during cycling for enhanced electrode integrity. 18…”

Artificially Layered CoSe2 Nanosheets by a Dual-Templating Strategy for High-Performance Lithium–Sulfur Batteries

“…17,18 (iii) Not only the starting active material (S) but also the discharging product (Li 2 S) has low electronic/ionic conductivities, leading to poor rate performance. 19,20 (iv) The inert Li 2 S requires an activation potential in the charging process. 21 To overcome these issues, incorporation of active MX 2 electrocatalysts featuring strong chemisorption and high catalytic activity is proposed as a powerful route to enhance the discharge/charge perform-ance.…”

“…One the other hand, lithium–sulfur batteries (LSBs) possessing a high theoretical specific capacity (1675 mAh g –1 ) are promising as the next-generation high-energy-density rechargeable batteries. − Nevertheless, the development of LSBs still encounters several critical issues and obstacles. (i) The slow reaction kinetics of S 8 -Li 2 S x -Li 2 S in the electrochemical process leads to low capacity and poor rate capability. , (ii) The soluble lithium polysulfides (LiPSs) in the electrolyte induce an undesirable phenomenon of “shuttle effect”, resulting in active material loss and specific capacity degeneration. , (iii) Not only the starting active material (S) but also the discharging product (Li 2 S) has low electronic/ionic conductivities, leading to poor rate performance. , (iv) The inert Li 2 S requires an activation potential in the charging process . To overcome these issues, incorporation of active MX 2 electrocatalysts featuring strong chemisorption and high catalytic activity is proposed as a powerful route to enhance the discharge/charge performance. − L-CoSe 2 has the merits of a layered structure for fast Li + diffusion, a metallic conductivity for fast electron transport, and a large surface area providing sufficient catalytic sites for strong immobilization and high catalytic activity.…”

Carbon‐to‐sulfur ratio in the cell controls the discharge capacity, cycling performance and energy density of a lithium‐sulfur battery

“…13 Another study developed a highly porous N-doped C nanofiber cathode providing high active material utilization as well as effective electrolyte percolation. 14 Moreover, cathode design with freestanding and low-tortuosity N, O co-doped wood-like carbon frameworks with carbon nanotube forests were reported to achieve high energy density as a result of high S loading in the cathode. 15 Cobalt nanoparticleencapsulated carbon nanowire arrays on carbon cloth was also shown to attain enhanced reaction kinetics and high initial discharge capacity of 807 mAh g À1 at 1C with a low capacity fading rate through 300 cycles.…”