Catalytic and Dual‐Conductive Matrix Regulating the Kinetic Behaviors of Polysulfides in Flexible Li–S Batteries

Abstract

The main challenge in developing foldable Li–S batteries (LSB) lies in developing an electrode that is ultraflexible, conductive, and catalytic for dissolved lithium polysulfides (LiPSs). In this paper, lightweight macromolecule graphitic carbon nitride (g‐C3N4) film and a conductive polymer (CP) of poly(3,4‐ethylenedioxythiophene) shell are introduced into flexible LSBs by compositing with carbon cloth (CC). In the designed hybrid of CP/g‐C3N4@CC, 2D g‐C3N4 is used in the form of an effective trapper and functions as a continuous catalytic layer for LiPSs via the formation of pyridinic‐N‐Li bonds. This is revealed by both experimental investigations and theoretical analysis. The sandwich‐like CC and CP simultaneously bring an omnidirectional conductive network for fast interfacial reaction kinetics. With these benefits, the self‐supported CP/g‐C3N4@CC forms a powerful interaction system to fully in situ “lock” LiPSs in the commercial CC matrix. Thus, a substantially enhanced electrochemical performance is obtained at a high sulfur loading (4.7 mg cm–2) even operating in a pouch cell. This work may provide a potential avenue for practical use of high‐performance LSBs toward flexible energy‐storage devices.

Macroporous Multichannel Carbon Nanofibers Embedded with Co/Fe‐N Electrocatalyst as the Sulfur Host for Boosting Polysulfides Conversion in Lithium‐Sulfur Batteries

“…The large capacity difference between initial cycle and second cycle is mainly attributed the rearrangement of active sulfur. [48] Compared with Co/FeÀ N/MCFs/S, MCFs/S presents an inferior cyclability and delivers a low reversible capacity of 776.9 mA h g À 1 after 100 cycles. Moreover, Co/FeÀ N/MCFs/S also delivers a decent initial capacity of 1156 mA h g À 1 at 0.2 C with an improved sulfur loading of 2 mg cm À 2 , and maintains stable cycling performance with a low decay rate of 0.17 % per cycle over 250 cycles (Figure S10).…”

“…The CV curves were obtained at different scanning rate to determine the Li + diffusion coefficients of Co/FeÀ N/MCFs/S and MCFs/S (Figure S7 a-d). [48] Based on the Randles-Sevcik equation, there is a linear relationship between the peak current and the square root of scanning rates, and the slope of the fitting curves reflects diffusion coefficients of Li + . [49,50] In both reduction and oxidation processes, the D Li + values of Co/FeÀ N/MCFs/S are higher than the counterparts of MCFs/S (Figure 3f).…”

“…Such phenomenon is mainly attributed to that the active Co/Fe−N sites embedded in the carbon skeleton can functionalize as the trapping and catalyzing center toward the soluble LiPSs. The CV curves were obtained at different scanning rate to determine the Li + diffusion coefficients of Co/Fe−N/MCFs/S and MCFs/S (Figure S7 a–d) [48] . Based on the Randles‐Sevcik equation, there is a linear relationship between the peak current and the square root of scanning rates, and the slope of the fitting curves reflects diffusion coefficients of Li + [49,50] .…”

Fibrous Materials for Flexible Li–S Battery

“…Constructing fibrous current collectors with hierarchical architectures can solve this problem. So far, CNTs, [80] CNFs, [81,82] graphene-based network, [83] carbonized fibers/fabric, [84] and their hybrids [85] were broadly reported as good flexible S/Li 2 S current collectors. For example, Yuan et al developed a CNT-based current collector (7.1 S cm −1 ) consisting of highly conductive MWCNTs and mechanically robust VACNTs (Figure 8a).…”

Recent Advances of Freestanding Cathodes for Li‐S Batteries

“…In the past few years, researchers have come up with various strategies to improve the electrochemical performance of LSBs [13–16] . Carbon‐based materials with high conductivity have been widely used as sulfur host for the construction of sulfur/carbon composites to enhance the performance of LSBs [17–20] .…”