Lean-electrolyte lithium–sulfur electrochemical cells with high-loading carbon nanotube/nanofiber–polysulfide cathodes

Abstract

A carbon-nanotube/nanofiber–polysulfide cathode achieves long-term cycle stability and explores the failure mechanism of a lithium–sulfur cell with high sulfur loading/content at a lean electrolyte condition.

A Poly(ethylene oxide)/Lithium bis(trifluoromethanesulfonyl)imide-Coated Polypropylene Membrane for a High-Loading Lithium–Sulfur Battery

“…The polarization is also maintained low ( Figure S7). These results indicate that the PEO/LiTFSI-coated polypropylene membrane affords high-loading sulfur cathodes with good electrochemical reaction capability and high polysulfide retention [3,8,9,44]. Figure 3d illustrates the cycling performance of the high-loading polysulfide cathodes, which attain high discharge capacities of 1212 mA•h g −1 , 981 mA•h g −1 , and 637 mA•h g −1 at sulfur loadings (contents) of 2 mg cm −2 (51 wt%), 4 mg cm −2 (67 wt %), and 6 mg cm −2 (76 wt %), respectively.…”

“…To verify the foregoing results, the electrochemical reaction kinetics (Figure 3e,f) and reversibility/stability (Figure 3g-i) of high-loading sulfur cathodes are evaluated from their impedance spectra and rate-dependent CV curves, respectively. In Figure 3e,f, the low and decreasing cell impedance featuring low charge-transfer resistance and ion-diffusion impedance of the cell after cycling indicate good reaction capability and fast ion transfer [44,45]. Figure 3g-i presents the rate-dependent CV curves of the cells with sulfur loadings (content) of 2 mg cm −2 (51 wt%), 4 mg cm −2 (67 wt %), and 6 (76 wt %) mg cm −2 , respectively.…”

Nanoporosity of Carbon–Sulfur Nanocomposites toward the Lithium–Sulfur Battery Electrochemistry

“…Figure 2a-d depict the voltage profiles of the nanocomposites. The redox process involved the reduction of sulfur to polysulfides at~2.3 V (marked with a black box) and the subsequent conversion from polysulfides to sulfides at~2.1 V (marked with a red box) during discharge [9,[21][22][23]. The initial discharge capacity values of the nonporous, microporous, micro/mesoporous, and macroporous C-S nanocomposites attained 1036, 1084, 1077, and 831 mA•h g −1 , respectively, at the C/10 rate.…”

“…As the cycling rate increases to the fast C/3 rate, nonporous carbon cannot retain normal cyclability and loses its high-rate capability due to the formation of insulating solid-state active materials on its surface (Figure 3a). The microporous and micro/mesoporous carbons that encapsulate the insulating solid-state sulfur and sulfides, and absorb dissolved polysulfides within their nanoporous spaces [12,[19][20][21][22], enable the high-loading cathode to attain an enhanced high-rate capability and stability (Figure 3b,c). The macroporous C-S nanocomposite experiences low reaction kinetics and deteriorated polarization with increases in the cycling rates (Figure 3d).…”

“…To address these issues, great effort has been devoted to the encapsulation of the insulating sulfur in various porous conductive carbon substrates to yield a carbon-sulfur (C-S) nanocomposite, which improves the charge-transfer capability and absorbs the dissolved polysulfides [12][13][14][15][16][17][18]. Although different polar materials are subsequently reported to have a strong chemical polysulfide-trapping capability, these materials must be either mixed with, generated on, or made to decorate a porous conductive carbon substrate to obtain their promising performance in high-capacity retention [19][20][21][22][23][24][25]. This means that a C-S nanocomposite study might be the foundation for developing a Li-S battery cathode that enables the use of a large amount of insulating active material to attain high-performance electrochemical characteristics [12][13][14][15][16][17][18][19][20].…”