Enhanced rate capability and cycle stability of lithium–sulfur batteries with a bifunctional MCNT@PEG-modified separator

Abstract

A MCNT@PEG composite is designed to modify the commercial separator of Li-S cells. With the MCNT@PEG-modified separator, Li-S cells possess enhanced rate capability and cycle stability.

Ultra-lightweight PANiNF/MWCNT-functionalized separators with synergistic suppression of polysulfide migration for Li–S batteries with pure sulfur cathodes

“…[5][6][7]17 Moreover, the SEM observation on the scraped region exhibits weak sulfur signals on the exposed Celgard PP sheet as compared to those on the bare Celgard membrane used in conventional cell configurations (Fig. [5][6][7][8][9][10] The electrochemical analyses of the cell employing the PANiNF/MWCNT-functionalized separator are summarized in Fig. This provides solid evidence that the migrating polysulfides are virtually confined in the PANiNF/MWCNT layer and are difficult to escape out from the thin-film barrier.…”

“…[1][2][3] However, the practical use of lithium-sulfur (Li-S) batteries is plagued by several vital culprits including (i) the low active-material utilization due to the insulating nature of sulfur and its discharge products (Li 2 S/Li 2 S 2 ) and (ii) the diffusion of polysulfide species (Li 2 S n , 4 < n ≤ 8) through the liquid electrolyte during operation resulting in fast capacity fade and short cycle life. [8][9][10][11][12][13] The carbon-coated separators attract enormous attention by dual-functionally working as an uppercurrent collector and as a polysulfide-diffusion obstacle, which enhance the cell reversibility. [5][6][7] These investigations motivated several groups for the successful development of different custom carbon-and polymer-coated separators, as summarized in Table 1.…”

“…The conductive PANiNF that has strong polysulfide-immobilizing capability is intended to chemically trap the migrating polysulfides. 7,9 Second, the hybrid conductive polymer and sp 2 carbon coating promote the redox accessibility of pure sulfur cathode and the reactivation/reutilization of the trapped active material. [10][11][12] In addition to trapping polysulfides, the MWCNTs that are interwoven with the conductive PANiNF in the hybrid coating facilitate electron transport for enhancing the electrochemical utilization of sulfur and for reactivating the trapped active materials.…”

Honeycomb‐like Nitrogen and Sulfur Dual‐Doped Hierarchical Porous Biomass‐Derived Carbon for Lithium–Sulfur Batteries

“…[7,8] Moreover,t he poor conductivities of sulfur (5 10 À30 Scm À1 at 25 8C) and its dischargep roduct Li 2 S( 1 10 À14 Scm À1 ) [9] also limit the rate capability of Li-S batteries.T he densities of sulfur and Li 2 Sa re 2.03 gcm À3 and 1.66 gcm À3 ,r espectively,w hich may induce the large volume expansion/shrinkage (80 %) during the charge/discharge process, destroying the electrode structure and impairing the life of the battery. One is to infiltrate sulfur into porousconductive carbon framework, such as micro/mesoporous carbon, [20,21] hollow carbons pheres, [22,23] graphene, [24,25] carbon nanofibers, [26,27] and some composites of these structures. Of particular interest is the use of an electrolyte additive, [19] such as lithium nitrate, which is one of the most useful strategies to extendc ycle life.…”

Li2S nano spheres anchored to single-layered graphene as a high-performance cathode material for lithium/sulfur cells

“…The dissolution of lithium polysulfides into organic liquid electrolytes and its "shuttle effect" together with mechanical degradation of the sulfur cathode (caused by severe volume change of sulfur particles (up to 80%) during cycling) limits the Li/S cell lifetime, meanwhile, the electrically insulating nature of sulfur and Li 2 S causes sluggish reaction kinetics, resulting in low electrochemical utilization of the active material and poor rate capability [16,17]. As a result of efforts to address these issues significant improvements have been made in recent years by coupling sulfur to various carbon materials (e.g., graphene, graphene oxide (GO), and carbon fibers), polymers (e.g., polyethylene glycol (PEG), polypyrrole (PPY), polyacrylonitrile (PAN)) and transition metal oxides with novel hierarchical and core-shell configurations to overcome the drawbacks of the sulfur cathode [4,[18][19][20][21][22][23][24][25][26][27][28][29]. In addition, another difficulty of the Li/S cells is the use of a metallic lithium anode, which is associated with dendrite formation on the surface of the Li metal anode caused by the inhomogeneous current distribution during cycling, leading to serious safety hazards and cell shorting [30][31][32].…”