Oxygen‐Doped Carbon Nitride Tubes for Highly Stable Lithium–Sulfur Batteries

Abstract

Graphitic carbon nitride g‐C3N4 (GCN) has attracted extensive attention for electrochemical energy storage and conversion due to its high surface area, metal‐free characteristics, “earth‐abundance,” and facile synthesis. Furthermore, GCN has been demonstrated to exhibit a chemical interaction with polysulfides because of functional pyridinic nitrogen atoms, thus representing promising properties for application in lithium–sulfur (Li–S) batteries. Herein, an oxygen‐doped hexagonal tubular carbon nitride (O‐TCN) is obtained through a simple hydrolysis and pyrolysis approach. The tubular structure favors electrolyte infiltration and accommodates the volume change of sulfur during the redox reaction. Moreover, O‐TCN/S with a high content of pyridinic N of about 80 wt% as the sulfur host is beneficial for trapping various polysulfide intermediates via numerous strong N–Li chemical interactions, further facilitating the transformation from high‐order polysulfides to low‐order Li2S2 or Li2S. As a result, O‐TCN delivers a high discharge capacity of 1281 mAh·g−1 at 0.05 C for the first cycle, and an excellent reversible capacity of 401 mAh g−1 after 1000 cycles at 0.5 C with an ultralow capacity decay of 0.064% per cycle, presenting a high sulfur utilization and capacity retention.

Enhanced Cyclic Stability of Sulfur Electrode by a Li‐Nafion‐Supported Encapsulated Configuration

“…[ 27,50 ] The CV results of the encapsulated sulfur electrode testing for five cycles are shown in Figure 7b. The peaks around 2.3 and 2.0 V indexed to the two‐step reductions of elemental sulfur to dissolved Li 2 S 4‐8 and insoluble Li 2 S 2 /Li 2 S [ 51 ] are nearly overlapped in the five CV curves. The peak at 2.4 V ascribed to the process of Li 2 S oxidized to Li 2 S 4‐8 and S 8 shows merely a slight decline as the cycle proceeds.…”

Freestanding MXene‐based macroforms for electrochemical energy storage applications

“…Lithium-sulfur batteries (LiSBs) have been seen as one of the more promising candidates for next-generation energy storage devices by virtue of their high energy density (2600 Wh kg −1 ) and low cost. [129][130][131][132][133][134] Nevertheless, the practical application of LiSBs still suffers from the fast capacity fading and low Coulombic efficiency, owing to the problematic issues of the sulfur cathode: (1) the shuttle effect of lithium polysulfides (LiPSs) (Li 2 S n , 4 ≤ n ≤ 8) between the anode and cathode and (2) sluggish redox reaction kinetics. A general strategy to tackle these challenges is physically and chemically entrapping LiPSs with non-polar host materials.…”

Renewable biomass-derived carbon-based hosts for lithium–sulfur batteries

“…Carbon nitride (g-C 3 N 4 ), with its nitrogen content as high as 61 wt% and can form strong N-Li bonds, presents remarkable immobilization capacity for polysuldes. 41,159 Furthermore, Lewis-base pyridine nitrogen exists in g-C 3 N 4 and can effectively interact with the strong Lewis-acid of terminal Li atoms in polysuldes, thereby contributing to prolonging the lifespan of LSBs. 142,160 Wu et al 161 prepared a chitin-derived N-doped carbon material (C-NC) and combined it with a small amount of graphene (GN) and g-C 3 N 4 for use as the host in LSBs.…”