LiV₃O₈-Based Functional Separator Coating as Effective Polysulfide Mediator for Lithium–Sulfur Batteries

Abstract

The commercial development of high-energy lithium−sulfur (Li−S) batteries is still hampered by the irreversible active material loss and fast capacity decay triggered by the dissolution of polysulfide species and the subsequent polysulfide shuttle effect. Carbon-coated separators can limit the diffusion of polar polysulfide intermediates between electrodes. However, the capacity fading still exists owing to the weak interaction of nonpolar carbons. Herein, a novel lithium vanadium(V) oxide-coated hybrid separator (LiV 3 O 8 − HS) is designed for enhancing the performance of Li−S batteries. The results show that the LiV 3 O 8 coating acts as a shield-like redox mediator to physically block the diffusion of polysulfide intermediates and chemically promotes the conversion of soluble higher-order polysulfides to insoluble short-chain polysulfides via internal disproportionation reactions, accelerating the redox reaction kinetics and lessening the active material loss during cycling. As a consequence, Li−S cells with the LiV 3 O 8 −HS demonstrated superior electrochemical performance despite using a pure sulfur cathode, with a high initial discharge capacity of 1254 mAh g −1 at 0.2 C and superior long-term cyclability with a low average capacity decline of 0.063% per cycle after 500 cycles at 0.5 C. The coating of the commercial separator, which can be straightforwardly adopted in an industrial process, offers a simple and powerful route for boosting the performance of Li−S batteries toward commercial application.

A Mott–Schottky Heterogeneous Layer for Li–S Batteries: Enabling Both High Stability and Commercial‐Sulfur Utilization

“…To the best of our knowledge, such high-rate (5 C) cycle stability based on the commercial-sulfur cathode is superior to most of the reported LSBs (Figure 2g). [19,43,46,48,[53][54][55][56][57] Although the low temperature will slow down the LiPSs migration and inhibit the catalytic effect of active component in sulfur conversion, the cell with RPM/PP delivers a high initial discharge capacity of 941.2 mAh g −1 even at −20 °C, which can still maintain at 717.8 mAh g −1 after 150 cycles at 0.5 C with a capacity retention of 56.2% (Figure S12, Supporting Information). [58] Furthermore, a high sulfur utilization of 56.2% can also be achieved under such harsh temperature conditions, demonstrating the strong catalytic and utilization ability of the RPM layer for LiPSs.…”

Functionally Modified Polyolefin-Based Separators for Lithium-Sulfur Batteries: Progress and Prospects

“…Meanwhile, carbon nanofiber coatings have effectively positive roles in limiting polysulfide shuttles by dual-effects. Due to the high strength to weight ratio, adjustable microarchitecture, and facile preparation, carbon nanofibers are prone to an ideal specific surface area, porosity, and size, determining the capability of (Maletti et al, 2020) sieving polysulfides. Moreover, according to these features, coating technology can easily access functional separators with ultrathin thickness, high mechanical strength, and good flexibility.…”

Dual-role magnesium aluminate ceramic film as an advanced separator and polysulfide trapper in a Li–S battery: experimental and DFT investigations

“…Maletti et al reported a LiV 3 O 8 -coated commercial separator, which acts as a redox mediator, converting the soluble higher-order polysulfides into lower-order sulfides. 35 The high polysulfide affinity and the improved charge transfer at the electrode/electrolyte interface was reported using a CeO 2 /multiwalled carbon nanotubes (MWCNT) composite-coated separator, which retained a stable capacity of 520 mA h g À1 even after 300 cycles. CeO 2 exhibited affinity toward polysulfide, and MWCNTs exhibited physisorption of polysulfide, besides serving as a secondary current collector to improve the conductivity at the interface of the cathode/separator.…”