CoS2-NC@CNTs hierarchical nanostructures for efficient polysulfide regulation in lithium-sulfur batteries

Constructing high-throughput and highly adsorptive lithium-sulfur battery separator coatings based on three-dimensional hexagonal star-shaped MOF derivatives

The electrochemical performance of high-performance lithium-sulfur (Li-S) batteries is affected by many factors such as shuttle effect and lithium dendrites. To effectively solve this problem, a hexagonal star-shaped composite catalyst containing Co-N-C active sites (Co-NC-X) has been rationally developed under the joint action of Zn2+ and Co2+ bimetallic ions. By modifying it to the Li-S battery separator, Co-NC-X can not only act as a physical barrier to effectively prevent the diffusion of lithium polysulfide (LiPS), but also the special morphology can expose more active sites and have a strong chemisorption effect on LiPS, which effectively promotes the redox conversion of LiPS and mitigates the shuttle effect. Li-S battery with Co-NC-X exhibits excellent electrochemical performance. It has a high specific capacity and stable cycling performance, with an initial discharge capacity of 1406.9 mAh·g-1 at 0.2 C and 876.8 mAh·g-1 at 2 C, and a lower capacity decline rate of 0.093 % for 500 cycles.

A multifunctional self-supporting LLTO/C interlayer for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are recognized as an encouraging alternative for future power storage technologies. However, their practical application is hindered by several significant challenges, including slow redox kinetics, the shuttle effect, and the formation of lithium dendrites. Here a binder-free, self-supporting multifunctional interlayer composed of lithium lanthanum titanate (LLTO) with amorphous carbon nanofiber matrices for Li-S batteries has been constructed. This multifunctional interlayer has been designed to facilitate the redox kinetics of lithium polysulfides (LiPSs), promote the nucleation of lithium sulfide (Li2S), and hinder the formation of lithium dendrites. The electrocatalytic properties of the interlayer were subjected to systematic evaluation through electrochemical testing, and the lithium deposition was assessed by examining the surface evolution of lithium metal in symmetric cells. The LLTO carbon matrix interlayer sustained a high specific capacity of 703.3 mA h g-1 after 200 cycles at 0.1C, with a sulfur loading of 5.5 mg cm-2. Furthermore, it demonstrated a high capacity of 905.9 mA h g-1 with a decay rate of 0.069% per cycle over 1000 cycles at a current density of 5C with a sulfur loading of 1 mg cm-2. This investigation highlights the potential of LLTO carbon composite materials as multifunctional interlayers, which could facilitate the optimization of advanced Li-S batteries.

CoS2@C catalyzes polysulfide conversion to promote the rate and cycling performances of lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have been considered one of the most promising candidates for next-generation energy storage devices due to their high theoretical energy density and low cost. Nonetheless, the practical application of Li-S batteries is still inhibited by their lithium polysulfide (LiPS) shuttling and sluggish redox kinetics, which cause rapid capacity decay and inferior rate performance. Hence, anchoring LiPSs and catalyzing their conversion reactions are imperative to enhance the performance of Li-S batteries. In this work, one-dimensional (1D) porous carbon-encapsulated CoS2 (CoS2@C) fiber structures were prepared through a simple two-step hydrothermal reaction and they exhibited a robust LiPS trapping ability and rapid catalytic conversion of LiPSs. The formed three-dimensional (3D) architecture (CoS2@C/MWCNT) facilitates the physical adsorption of LiPSs and rapid ion transport. The electrode exhibited a high initial capacity of 1329.5 mA h g-1 at a current density of 0.1 C and a reversible capacity of 1060.6 mA h g-1 after 100 cycles, with an 80% capacity retention rate. Meanwhile, the decay rate of the electrode is 0.048% per cycle at 1 C and after 500 cycles. With a sulfur loading of 3 mg cm-2, the capacity retention rate is approximately 83.7% after 80 cycles.