Nitrogen‐Doped Hollow Carbon Polyhedrons with Carbon Nanotubes Surface Layers as Effective Sulfur Hosts for High‐Rate, Long‐Lifespan Lithium–Sulfur Batteries

Abstract

Effectively confining lithium polysulfides inside porous material matrix with a high electrical conductivity represents a judicious way to extend lifespan and enhance rate performance of lithium‐sulfur (Li‐S) batteries. Herein, nitrogen‐doped hollow carbon polyhedrons with a thin CNTs conductive surface layer (CNTs/HNC) were prepared by directly pyrolyzing the CNTs coated ZIF‐8 polyhedrons crystallite precursors, and subsequently served as sulfur hosts in Li‐S batteries. The resulted product CNTs/HNC‐800 comprises a nitrogen content of 4.94 at.% as well as a high electrical conductivity of 8.43×10−1 S cm−1, which help to effectively adsorb/confine lithium polysulfides and substantially improve the rate capacity of Li‐S batteries. With a sulfur loading of 1.60 mg cm−2, the S@CNTs/HNC based cathode shows a discharge capacity of 870.7 mAh g−1 at 1.0 C, and can maintain 76.4 % of its initial capacity after 500 charge‐discharge cycles, corresponding to a capacity fade rate of only 0.047 % per cycle. While with a higher sulfur loading of 2.46 mg cm−2, a discharge capacity of 649.7 mAh g−1 can be achieved at 0.5 C, along with a capacity fade rate of merely 0.044 % per cycle during 200 cycles. When sulfur loading is further increased to 5.39 mg cm−2, it can also maintain a considerable initial discharge capacity of 812 mAh g−1 at 0.1 C. This work enriches the ways to prepare complicate nano structured sulfur hosts for long‐life and high‐rate Li‐S batteries.

Fe(III) Ions-Assisted Aniline Polymerization Strategy to Nitrogen-Doped Carbon-Supported Bimetallic CoFeP Nanospheres as Efficient Bifunctional Electrocatalysts toward Overall Water Splitting

“…In addition, a small amount of N was detected in the CoFeP-NC samples, likely originating from PANI. In the spectrum of N 1s, the corresponding pyrrolic N, graphitic N and pyridinic N can be observed ( Figure S7 ) [ 47 ]. For Co 2p ( Figure 3 b), the existence of two peaks at 778.7 and 793.3 eV can be assigned to Co-P, the peaks at 781.7 and 798.1 eV can be explained as the oxidation form on the catalyst surface and the remaining peaks located at 785.5 and 803.7 eV can be identified as satellite peaks [ 48 ] For Fe 2p ( Figure 3 c), the small peaks located at 707.3 and 720.5 eV can be attributed to the Fe-P.…”

Polypyrrole/Graphene Composite Interlayer: High Redox Kinetics of Polysulfides and Electrochemical Performance of Lithium–Sulfur Batteries Enabled by Unique Pyrrolic Nitrogen Sites

“…Sluggish redox kinetics of polysulfides (PSs), low electrical conductivity of sulfur and shuttling effect of soluble PSs in electrolyte result in rapid capacity fading and inferior charge/ discharge current density of LiÀ S batteries, and thus prevent their practical application. [1][2][3][4][5] Currently, most of the LiÀ S battery is performed using flooded electrolyte, [6] resulting in a quite low energy density. Hence, practical application of LiÀ S batteries requires to further reduce the usage of electrolyte and improve energy density, rendering them competitive with that of lithium-ion batteries.…”

“…Sluggish redox kinetics of polysulfides (PSs), low electrical conductivity of sulfur and shuttling effect of soluble PSs in electrolyte result in rapid capacity fading and inferior charge/discharge current density of Li−S batteries, and thus prevent their practical application [1–5] . Currently, most of the Li−S battery is performed using flooded electrolyte, [6] resulting in a quite low energy density.…”

Review of Cathode in Advanced Li−S Batteries: The Effect of Doping Atoms at Micro Levels

“…In short, thanks to the non‐polarity of carbon materials, the polysulfides cannot be kept in the C/S cathode commendably, resulting in the production of low‐grade polysulfides and reduction of the available capacity and coulomb efficiency. Therefore, the atomic doping strategy, which can provide enough chemical coupling and stronger confinement effects to keep lithium polysulfide in cathode materials, has attracted extensive attention and in‐depth research [30–33] . The doping of heteroatoms in the carbon skeleton can induce higher charge delocalization and a donor density of states near Fermi level, expand the interlayer spacing, enhance the wettability of active materials and improve the conductivity of carbon‐based electrodes [34,35] .…”