Hierarchical N‐Rich Carbon Sponge with Excellent Cycling Performance for Lithium‐Sulfur Battery at High Rates

Abstract

Lithium-sulfur batteries (LSBs) are receiving extensive attention because of their high theoretical energy density. However, practical applications of LSBs are still hindered by their rapid capacity decay and short cycle life, especially at high rates. Herein, a highly N-doped (≈13.42 at %) hierarchical carbon sponge (HNCS) with strong chemical adsorption for lithium polysulfide is fabricated through a simple sol-gel route followed by carbonization. Upon using the HNCS as the sulfur host material in the cathode and an HNCS-coated separator, the battery delivers an excellent cycling stability with high specific capacities of 424 and 326 mA h g and low capacity fading rates of 0.033 % and 0.030 % per cycle after 1000 cycles under high rates of 5 and 10 C, respectively, which are superior to those of other reported carbonaceous materials. These impressive cycling performances indicate that such a battery could promote the practical application prospects of LSBs.

Sustainable Synthesis of N‐Doped Hollow Porous Carbon Spheres via a Spray‐Drying Method for Lithium‐Sulfur Storage with Ultralong Cycle Life

“…More importantly, the N‐HPCS/S sample also shows awe‐inspiring cycling performance at 0.1 C (Figure S10d) and 1 C (Figure 4e) rates. As shown in Figure 4e, the discharge capacity of HPCS/S at 1 C rate is 529.4 mA h g −1 at the first cycle and decreases to 162.1 mA h g −1 at the 910 th cycle (capacity decay: 0.069 % per cycle), the relatively fast decay should be ascribed to the low surface specific area, and lack of effective pore structure and chemical bonding sites [41,46,56] . On the contrary, the N‐HPCS/S sample delivers a high capacity of 1102.7 mA h g −1 at the initial cycle and an impressive capacity of 646.9 mA h g −1 at the 1000 th cycle (capacity decay: 0.041 % per cycle).…”

“…It is well known that pyrrolic‐N and pyridinic‐N have been confirmed to significantly improve the electrochemical performance of Li−S batteries, especially that pyrrolic‐N is more critical than pyridinic‐N in promoting charge transfer and immobilization of polysulfides due to its low carrier scattering and strong donor capability [43,44] . In addition, pyrrolic‐N is p‐type doping, which can cause a large number of vacancy defects [45,46] . Each pyrrolic‐N atom can provide a lone pair of electrons in the aromatic ring of the carbon spheres, providing a binding site for the highly positively charged Li + in the lithium polysulfide (Li 2 S x ), thereby forming the Li 2 S x ‐N bond, and preventing the dissolution and shuttling effect of Li 2 S x more efficiently [4,47] .…”

“…However, although N content of N‐HPCS/S‐2 is higher than N‐HPCS/S, its specific capacity at 0.1 C is still lower than that of N‐HPCS/S because N‐HPCS/S carbon spheres have the highest pyrrolic‐N content. As above‐mentioned, pyrrolic‐N could cause a large number of vacancy defects for Li‐ion and electron transportation, as well as provide abundant binding sites for S adsorption [43,46] …”

An Integrated Strategy towards Enhanced Performance of the Lithium–Sulfur Battery and its Fading Mechanism

“…[37] To solve these issues, various 3D currentc ollectors have been in-vestigated, which allow ah igh sulfur loading, efficient charge transfer and long cycling stability. [37][38][39][40][41][42][43][44] However,t hese innovative structuresh ave some drawbacks, including:a )complex and expensive fabrication procedures that are difficult to scale up, b) as pecial sulfur introductions tep that is incompatible with traditional slurry preparation processes, c) the demand for large electrolyte volumet ow et the electrode, which sacrifices the overall energy density. [35,45] Current collectors that offset these shortfalls while maintaining some structural advantages are desirable.…”

Binary graphene-based cathode structure for high-performance lithium-sulfur batteries

“…The chemical adsorption from the weak interactions between non-polar carbon materials and polar polysulfides arouses the concern of insufficient polysulfide-anchoring capability [28][29][30]. Functionalizing carbon materials such as heteroatom doping is an effective way to introduce polar surface chemistry within the cathode material, which serves to enhance the interaction with the polar polysulfides via chemical adsorption [31][32][33]. Besides, the metal compounds with inherent polar surfaces, such as TiN [34], TiO x [35], VN [36] and MnO 2 [37], have also been used for achieving a high affinity of polysulfides in the cathode.…”