A Multifunctional Separator Enables Safe and Durable Lithium/Magnesium–Sulfur Batteries under Elevated Temperature

Abstract

Rechargeable metal–sulfur batteries encounter severe safety hazards and fast capacity decay, caused by the flammable and shrinkable separator and unwanted polysulfide dissolution under elevated temperatures. Herein, a multifunctional Janus separator is designed by integrating temperature endurable electrospinning polyimide nonwovens with a copper nanowire‐graphene nanosheet functional layer and a rigid lithium lanthanum zirconium oxide‐polyethylene oxide matrix. Such architecture offers multifold advantages: i) intrinsically high dimensional stability and flame‐retardant capability, ii) excellent electrolyte wettability and effective metal dendritic growth inhibition, and iii) powerful physical blockage/chemical anchoring capability for the shuttled polysulfides. As a consequence, the as constructed lithium–sulfur battery using a pure sulfur cathode displays an outstandingly high discharge capacity of 1402.1 mAh g−1 and a record high cycling stability (approximately average 0.24% capacity decay per cycle within 300 cycles) at 80 °C, outperforming the state‐of‐the‐art results in the literature. Promisingly, a high sulfur mass loading of ≈3.0 mg cm−2 and a record low electrolyte/sulfur ratio of 6.0 are achieved. This functional separator also performs well for a high temperature magnesium–sulfur battery. This work demonstrates a new concept for high performance metal–sulfur battery design and promises safe and durable operation of the next generation energy storage systems.

Progress and Perspective on Rechargeable Magnesium–Sulfur Batteries

“…[ 36a,61 ] Mg plating and stripping can be accomplished under a large overpotential in Mg(TFSI) 2 (i.e., Mg[N(SO 2 CF 3 ) 2 ] 2 ) and Mg(CF 3 SO 3 ) 2 salts due to the formation of a low Mg ion conductive layer on Mg anode. [ 62 ] Nevertheless, Mg(TFSI) 2 without incorporation of any additional anions usually has low Coulombic efficiency, a large overpotential and low Mg plating/stripping kinetics due to formation of a passive surface upon the inevitable presence of traces of moisture. [ 24b,26,28b,55,57a,63 ] To this end, MgCl 2 or Mg(BH 4 ) 2 are often added to help obtain stable and reversible Mg plating/stripping using Mg(TFSI) 2 salt.…”

“…Highly soluble polysulfides, however, may exacerbate ineffective shuttle effect, which should be inhibited through design of other battery components (e.g., CNF‐coated separators and protective layers on anodes). [ 24a,62 ] In addition, some techniques to increasing the sulfur utilization in Li‐S batteries are still applicable to Mg‐S batteries, including improving the contact between elemental sulfur and carbon matrix, increasing electronic conductivity of carbon matrix or developing more conducing transition metal sulfides. [ 42b,77 ]…”

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

“…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).…”

Recent Advances in Emerging Non‐Lithium Metal–Sulfur Batteries: A Review

“…Although difficulties remain, Mg-S batteries are among the most cost-effective ones in terms of their high volumetric capacity (3832 mAh cm −3 ), superior safety, high abundance, and low cost. [160][161][162]…”