Renewable Polysulfide Regulation by Versatile Films toward High-Loading Lithium–Sulfur Batteries

Abstract

The development of a high specific energy lithium–sulfur battery is heavily hindered by the so-called “shuttle effect”. Nevertheless, as an effective strategy, most modified separators cannot block and reuse polysulfides simultaneously. Here, a unique and versatile film fabricated by nitrogen and phosphorus co-doped carbon nanofibers uniformly anchored with TiC nanoparticles is incorporated between the separator and cathode of the lithium–sulfur battery. The battery armed with this functional film exhibits a high capacity of 737.1 mA h g–1 at 5 C with a slow capacity-fading rate of 0.06%/cycle over 500 cycles. Even when augmenting the sulfur loading to 17.1 mg cm–2, it can achieve a capacity of 837.3 mA h g–1 with a retention of ∼80% after 50 cycles. The TiC nanoparticles as well as heteroatom doping in the porous carbon nanofiber exhibit strong physiochemical adsorption and catalytic effect, which is proven by experiments and theoretical calculations. Thus, the diffusion of polysulfides can be effectively inhibited. Meanwhile, heteroatom doping can further enhance the conductivity and reaction activity of this film. Hence, the adsorbed polysulfides could be revived and renewed during the subsequent cycling process, which is accurately observed and confirmed by experiments for the first time.

Engineering Functional Interface with Built‐in Catalytic and Self‐Oxidation Sites for Highly Stable Lithium–Sulfur Batteries

“…In view of the reversible electrochemical process, the G@MC‐based battery exhibits a high specific capacity of 1498.6 mAh g −1 at 0.1 C, which is much higher than the battery with pristine separator (889.2 mAh g −1 , Figure S11), the commercial MnCO 3 modified separator (1249.8 mAh g −1 , Figure S12), or the graphene modified separator (956.1 mAh g −1 , Figure S13). Moreover, it could also harvest a high specific capacity of 320.0 mAh g −1 with the distinct voltage platforms even at a high C rate of 8.0, which is comparable to many reported literatures (Figure 2d and Table S1) [51–60] . This superior rate performance is ascribed to the accelerated kinetic conversion of intermediates and the strong affinity with LiPS due to the G@MC modified layer in a working Li−S battery (Figure S14).…”

“… The electrochemical performance of Li−S batteries with the G@MC modified separator. a) CV curves; b) Charge‐discharge profiles; c) Cycling performance; d) Comparison with reported literatures [51–59] …”

“…Moreover, it could also harvest a high specific capacity of 320.0 mAh g À 1 with the distinct voltage platforms even at a high C rate of 8.0, which is comparable to many reported literatures (Figure and Table S1). [51][52][53][54][55][56][57][58][59][60] This superior rate performance is ascribed to the accelerated kinetic conversion of intermediates and the strong affinity with LiPS due to the G@MC modified layer in a working LiÀ S battery (Figure S14). The specific capacity of the battery could also be recovered to 1106.6 mAh g À 1 , when the C rate switched backed to low current of 0.1 C. Its capacity retention is much higher in comparison with the cased of the batteries with pristine and commercial MnCO 3 modified separator, respectively (Figure S11 and S12).…”

“…With the chemical deposition of LiPS, the corresponding Li element is also detected on the surface of G@MC layer due to the chemically redox reaction of intermediates (Figure 3d). Meanwhile, the positive Li + ions would simultaneously bond with the negative CO 3 2À ions because of the electrostatic interaction, providing the extra traps for anchoring polysulfides [51][52][53][54][55][56][57][58][59] and mitigating their shuttle in electrolyte. Moreover, it is worth noting that the additional characteristic peaks located at 162.5 and 163.5 eV of S element correspond to the conversion reaction from long-chain to short-chain LiPS on the active surface of G@MC layer (Figure 3e).…”

CoSe2/MoS2 Heterostructures to Couple Polysulfide Adsorption and Catalysis in Lithium‐Sulfur Batteries†

“…However, non‐polar surfaces of carbon‐based materials could not trap polar polysulfides sufficiently. [ 15 ] In view of this, polar materials such as metal oxides, [ 16‐17 ] sulfides, [ 18‐19 ] selenides, [ 20 ] phosphates, [ 21 ] nitrides [ 22 ] and carbides [ 23 ] have been developed as sulfur hosts to take advantages of their strong chemical interactions with polysulfides. Such strategies can effectively suppress the shuttling effect and modestly increase the utilization of active sulfur species.…”