Enhanced Performance of Lithium–Sulfur Batteries with Co-Doped g-C₃N₄ Nanosheet-Based Separator

Abstract

Lithium−sulfur batteries are considered as one of the most potential energy storage devices in the future owing to their ideal theoretical energy density and specific capacity. However, the shuttle of soluble polysulfides and sluggish redox kinetics of polysulfides lead to insufficient use efficiency of active sulfur and the rapid capacity fading. In this study, novel Co-doped g-C 3 N 4 (Co−CN) nanosheets are fabricated by a simple calcination process. The high discharge capacity of the commercial bulk S cathode with the Co−CN-modified separator is 1121 mAh g −1 at 0.2C with a satisfying rate performance of up to 3C. The Co−CN-modified separator also leads to excellent stability (640 mAh g −1 after 250 cycles) with high Coulombic efficiency of over 98%. At the sulfur mass loading of 3 mg cm −2 , the cell can still deliver a discharge capacity of 719 mAh g −1 after 100 cycles with a high capacity retention of 95%. The improved performance can be attributed to the effective restriction of polysulfides shuttle due to the enhanced adsorption and catalytic conversion of polysulfides by the Co−CN nanosheet-modified separator. This work shares a simple and highly efficient strategy for increasing the performance of lithium−sulfur batteries.

Mo2C‐Embedded Carbon Nanofibers as the Interlayer in High‐Performance Lithium‐Sulfur Batteries

“…To research the catalytic effect of Mo 2 C@CNF on the conversion of LiPSs, cyclic voltammetry (CV) curves for symmetrical cells with Mo 2 C@CNF/CP (CNF/CP or CP) electrodes are obtained with a voltage from −1.0 to 1.0 V. From Figure 4a, the CV curve of Mo 2 C@CNF/CP symmetrical cells without Li 2 S 6 electrolyte presents no obvious current response, however the symmetrical cells containing Li 2 S 6 deliver a significant response, manifesting that the response current relates to the redox reaction of Li 2 S 6 . Besides, the symmetric cells with Mo 2 C@CNF/CP exhibit the largest redox current, confirming that the Mo 2 C can heighten the redox kinetics of LiPSs conversion [28] . The interfacial charge transfer behaviors of the Li 2 S 6 ‐symmetrical cells are further investigated through the electrochemical impedance spectroscopy (EIS).…”

“…Besides, the symmetric cells with Mo 2 C@CNF/ CP exhibit the largest redox current, confirming that the Mo 2 C can heighten the redox kinetics of LiPSs conversion. [28] The interfacial charge transfer behaviors of the Li 2 S 6 -symmetrical cells are further investigated through the electrochemical impedance spectroscopy (EIS). As displayed in Figure 4b, symmetric cells with Mo 2 C@CNF/CP exhibit the lowest charge transfer resistance than that of CP and CNF/CP based cells, which is due to the reason that Mo 2 C enhances the electrochemical conversion and interfacial redox reactions of Li 2 S 6 .…”

Strategies toward High-Loading Lithium–Sulfur Batteries

“…Consequently, the cell with the LVPF/CNT-modified separator maintained 551 mAh g –1 after 350 cycles at a sulfur loading of 7 mg cm –2 . Co-doped C 3 N 4 (Co-CN) can modify the separator for high-loading LSBs . The Co-CN nanosheets have a strong chemical affinity to LiPS by forming Co–S bonds and facilitate the LiPS reaction kinetics, thus preventing the shuttling effect.…”

“…Co-doped C 3 N 4 (Co-CN) can modify the separator for high-loading LSBs. 170 The Co-CN nanosheets have a strong chemical affinity to LiPS by forming Co−S bonds and facilitate the LiPS reaction kinetics, thus preventing the shuttling effect. The LSB with the Co-CN-modified separator showed a high capacity under a sulfur loading of 7 mg cm −2 .…”

Vanadium-doped graphitic carbon nitride for high performance lithium–sulfur batteries

“…With optimized mass ratio of MPC to g-C 3 N 4 precursor (melamine), g-C 3 N 4 /MPC attained a high adsorption capacity for polysulfides and could give rise to good electrochemical kinetics for polysulfide conversion. [11][12][13] Synthesis of g-C 3 N 4 from melamine resulted in a dense lamellar stacking structure. There are irregular particles on its surface, scattered with mesoporous and macroporous structures.…”