A High‐Kinetics Sulfur Cathode with a Highly Efficient Mechanism for Superior Room‐Temperature Na–S Batteries

Abstract

Applications of room‐temperature–sodium sulfur (RT‐Na/S) batteries are currently impeded by the insulating nature of sulfur, the slow redox kinetics of sulfur with sodium, and the dissolution and migration of sodium polysulfides. Herein, a novel micrometer‐sized hierarchical S cathode supported by FeS2 electrocatalyst, which is grown in situ in well‐confined carbon nanocage assemblies, is presented. The hierarchical carbon matrix can provide multiple physical entrapment to polysulfides, and the FeS2 nanograins exhibit a low Na‐ion diffusion barrier, strong binding energy, and high affinity for sodium polysulfides. Their combination makes it an ideal sulfur host to immobilize the polysulfides and achieve reversible conversion of polysulfides toward Na2S. Importantly, the hierarchical S cathode is suitable for large‐scale production via the inexpensive and green spray‐drying method. The porous hierarchical S cathode offers a high sulfur content of 65.5 wt%, and can deliver high reversible capacity (524 mAh g−1 over 300 cycles at 0.1 A g−1) and outstanding rate capability (395 mAh g−1 at 1 A g−1 for 850 cycles), holding great promise for both scientific research and real application.

General Synthesis of Single‐Atom Catalysts for Hydrogen Evolution Reactions and Room‐Temperature Na‐S Batteries

“…The Fe 1 @NC@S shows average capacities of 850, 522, 444, 392, 323, 250, and 205 mA hg À1 at the corresponding current densities of 0.2, 0.3, 0.5, 1, 2, 5, and 10 Ag À1 .Impressively,the capacity could be recovered to 542 mA hg À1 when the applied the current density was reversed to 0.2 Ag À1 .A lso,w ith ag radually increased rate,t he charge/discharge curves of Fe 1 @NC@S only show as mall polarization ( Figure 6D), meaning that the Fe 1 single atom is very effective for polysulfide immobilization and conversion even at high current rate.Acomparison of the reversible capacity versus the cycling stability of Fe 1 @NC@S with the state-of-the-art reports in the literature is presented in Figure 6E.I ti s impressive that the Fe 1 @NC@S shows an excellent capacity with ultra-stable cycling performance. [20,[23][24][34][35][36] Moreover, the retention of reversible capacity is very significant for the design of high-energy density batteries as well as its real use. Thesample Fe 1 @NC@S presented the high capacity retention of 76 %ofits initial reversible capacity,which is much higher than for the previously reported metal catalysts (inset image in Figure 6E).…”

“…[34] In particular,the peak at 0.81 Vcan be attributed to the formation of Na 2 Sa nd the solid-electrolyte interphase (SEI) layer. [35] Also,itisinteresting that those cathodic conversions are highly repeatable during the following cycles.Three strong reversible peaks have also been found at 1.64 V, 1.75 V, and 2.2 Vd uring the anodic scan of Fe 1 @NC@S,i ndicating its strong catalytic ability to achieve high charge capacity.Incontrast, the CV curves of Pt 1 @NC@S showed two major redox peaks at 1.95 Vand 2.09 V, indicating that the capacity is mainly attributable to the conversion from sulfur to long-chain polysulfides ( Figure 5C). The different major CV peaks of Fe 1 @NC@S and Pt 1 @NC@S are consistent with their different voltage-plateaus in chargedischarge curves.T ou nderstand the catalytic processes of Fe 1 @NC@S and Pt 1 @NC@S in the Na-S chemistry,the in situ synchrotron XRD (l = 0.6888 )w as carried out to gain insight into the products that appeared within the chargedischarge process throughout af resh coin cell.…”

Lewis Acid–Base Interactions between Polysulfides and Boehmite Enables Stable Room‐Temperature Sodium–Sulfur Batteries

“…NiS 2 nanocrystals, FeS 2 nanoparticles, metallic Co nanoparticles, VO 2 nanoflowers) could enhance the redox kinetics of RT Na-S batteries. [23][24][25][26] In this report, we have demonstrated that the Lewis acidbase interaction could be an alternative strategy to suppress the gradual dissolution of higher-order polysulfides and promote their further conversion to lower-order sulfides. A thin sheath of aluminum oxyhydroxide (AlOOH) to the surface of sulfur nanoparticles/carbon black composite (S@CB) is applied and the resulting composite is used as cathode material for RT Na-S batteries.…”

Potassium‐sulfur batteries: Status and perspectives

“…[26][27][28][29][30] Similar to Li-S batteries, however, the practical application of room-temperature Na-S batteries faces the challenges of low electrochemical utilization, reversibility, and efficiency. 26,[31][32][33] Additional challenges, such as the lack of favorable liquid electrolyte for the complicated reaction of sulfur and sodium, also need to be overcome before it becomes a reality. 2,34,35 Being the next alkaline metal to sodium, potassium, with some unique advantages over lithium and sodium, has drawn substantial attention from the scientific community as a future battery system of interest.…”