Reduced shuttle effect by dual synergism of lithium–sulfur batteries with polydopamine-modified polyimide separators

Micro-Nano Conductive Network Structured Aramid Paper-Based Self-Supporting Cathode Enhances Cycling Stability in Lithium-Sulfur Battery

Lithium-sulfur batteries (LSBs) continue to encounter significant challenges in practical applications, primarily attributed to the low electrical conductivity of the cathode active material sulfur, volume expansion during cycling and the uncontrolled shuttle effect of lithium polysulfides (LiPSs). In this work, flexible meta-aramid fibrids (AFs) were innovatively introduced, and polydopamine (PDA) was employed to effectively adhere highly conductive multiwalled carbon nanotubes (MWCNTs) to the AFs surface, thereby forming nanoscale conductive pathways. A wet-laid process analogous to aramid paper-making was utilized to enhance interfacial bonding between AFs and rigid carbon fibers (CFs), resulting in a self-supporting paper-based cathode material with a uniform, dense three-dimensional micronano-scale conductive network and stable structure. The porous structure between the fibers effectively alleviates sulfur's volume expansion. The polar PDA coating layer offers numerous chemical adsorption sites, which chemically anchor LiPSs and thereby more effectively suppresses the shuttle effect. The research results demonstrate that the AF@PDA-MWCNT/CF/S cathode delivers an impressive initial discharge specific capacity of 1140 mAh g-1 at a sulfur loading of 2.3 mg cm-2 and a current density of 0.2 C. After 400 cycles at a higher current density of 1 C, the single-cycle capacity fade rate is as low as 0.005%. Even at a high sulfur loading of 3.1 mg cm-2, the material still exhibits an initial discharge specific capacity of 890 mAh g-1. The AF@PDA-MWCNT/CF/S composite cathode developed in this study exhibits significant application potential and offers an approach for constructing self-supporting, paper-based cathode materials.

Influence of the PET-PTFE Separator Pore Structure on the Performance of Lithium Metal Batteries

The separator is a crucial component in lithium batteries, as it physically separates the cathode and the anode while allowing ion transfer through the internal channel. The pore structure of the separator significantly influences the performance of lithium batteries, particularly lithium metal batteries. In this study, we investigate the use of a Janus separator composed of poly(ethylene terephthalate) (PET)-polytetrafluoroethylene (PTFE) fibers in lithium metal batteries. This paper presents a comprehensive analysis of the impact of this asymmetric material on the cycling performance of the battery alongside an investigation into the influence of two different substrates on lithium-ion deposition behavior. The research findings indicate that when the rigid PET side faces the lithium metal anode and the soft PTFE side faces the cathode, it significantly extends the cycling lifespan of lithium metal batteries, with an impressive 82.6% capacity retention over 2000 cycles. Furthermore, this study demonstrates the versatility of this separator type in lithium metal batteries by assembling the lithium metal electrode with high cathode-loading capacities (4 mA h/cm2). In conclusion, the results suggest that the design of asymmetric separators can serve as an effective engineering strategy with substantial potential for enhancing the lifespan of lithium metal batteries.

Synergistic Effect of In2O3/NC-Co3O4 Interface on Enhancing the Redox Conversion of Polysulfides for High-Performance Li-S Cathode Materials at Low Temperatures

Lithium-sulfur (Li-S) batteries are considered as a promising energy storage technology due to their high energy density; however, the shuttling effect and sluggish redox kinetics of lithium polysulfides (LiPSs) severely deteriorate the electrochemical performance of Li-S batteries. Herein, we report a novel configuration wherein In2O3 and Co3O4 are incorporated into N-doped porous carbon as a sulfur host material (In2O3@NC-Co3O4) using metal-organic framework-based materials to synergistically tune the catalytic abilities of different metal oxides for different reaction stages of LiPSs, achieving a rapid redox conversion of LiPSs. In particular, the introduction of N-doped carbon improved the electron transport of the materials. The polar interface of In2O3 and Co3O4 anchors both long- and short-chain LiPSs and catalyzes long-chain and short-chain LiPSs, respectively, even at low temperatures. Consequently, the Li-S battery with In2O3@NC-Co3O4 cathode materials delivered an excellent discharge capacity of 1042.4 mAh g-1 at 1 C and a high capacity retention of 85.1% after 500 cycles. Impressively, the In2O3@NC-Co3O4 cathode displays superior performances at high current density and low temperature due to the enhanced redox kinetics, delivering 756 mAh g-1 at 2 C (room temperature) and 755 mAh g-1 at 0.1 C (-20 °C).

Cation-Selective Separators for Addressing the Lithium-Sulfur Battery Challenges

Lithium-sulfur batteries (LSBs) have become one of the most promising candidates for next-generation energy storage systems owing to their high theoretical energy density, environmental friendliness, and cost effectiveness. However, real-word applications are seriously restricted by an undesirable shuttle effect and Li dendrite formation. In essence, uncontrollable anion transport is a key factor that causes both polysulfide shuttling and dendrite formation, which creates the possibility of simultaneously addressing the two critical issues in LSBs. An effective strategy to control anion transport is the construction of cation-selective separators. Significant progress has been achieved in the inhibition of the shuttle effect, whereas addressing the problem of Li dendrite formation by utilizing a cation-selective separator is still under way. From this viewpoint, this Review analyzes critical issues with regard to the shuttle effect and Li dendrite formation caused by uncontrollable anion transport, based on which roles and advantages of cation-selective separators toward high-performance LSBs are presented. According to the separator-construction principle, the latest advances and progress in cation-selective separators in inhibiting the shuttle effect and Li dendrite formation are reviewed in detail. Finally, some challenges and prospects are proposed for the future development of cation-selective separators. This Review is anticipated to provide a new perspective for simultaneously addressing the two critical issues in LSBs.