Room-Temperature Potassium–Sulfur Batteries Enabled by Microporous Carbon Stabilized Small-Molecule Sulfur Cathodes

Abstract

Potassium−sulfur (K−S) batteries are a promising alternative to lithium ion batteries for large-area energy storage applications, owing to their high capacity and inexpensiveness, but they have been seldom investigated. Here we report room-temperature K−S batteries utilizing a microporous carbon-confined small-molecule sulfur composite cathode. The synergetic effects of the strong confinement of microporous carbon matrix and the small-molecule sulfur structure can effectually eliminate the formation of soluble polysulfides and ensure a reversible capacity of 1198.3 mA h g −1 and retain 72.5% after 150 cycles with a Coulombic efficiency of ∼97%. The potassium-storage mechanism was investigated by X-ray photoelectron spectroscopy analysis and theoretical calculations. The results suggest that K 2 S is the final potassiation product along with the reaction of 2K + S ↔ K 2 S, giving a theoretical capacity of 1675 mA h g −1 . Our findings not only provide an effective strategy to fabricate high-performance room-temperature K−S batteries but also offer a basic comprehension of the potassium storage mechanism of sulfur cathode materials.

Metal chalcogenides for potassium storage

“…For example, sulfur can be stored in microporous carbon substrates via impregnation or vaporization‐condensation methods. Xu's group has carried out an impressive work related to this . In their studies, small allotropes of sulfur (S n , n ≤ 3) were confined in a microporous carbon matrix, which prevented the sublimation and decomposition of sulfur via the strong interactions between the fragment sulfur species and carbon atoms, thereby effectively alleviating the solvation of polysulfides and enhancing the reaction kinetics.…”

“…Simultaneously, optimization to achieve the best match of anode material and electrolyte is also crucial to minimize parasitic reactions and achieve a wide voltage window and large capacity, thus further improving the energy density and working life of PIBs. On the other hand, improving the potassium storage capability of metal‐chalcogenide‐based materials will not only aid the development of PIBs as high‐performance power storage devices but will also facilitate the development of other novel rechargeable systems on the basis of K + ‐ion storage mechanism (such as K‐S/Se batteries, K dual‐ion batteries, K + ‐ion battery capacitors, and K‐O 2 batteries) for advanced and practical energy storage applications …”

Amidation‐Dominated Re‐Assembly Strategy for Single‐Atom Design/Nano‐Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K‐Storage

“…The cycling performance of NiSA/S/C nanotube in voltage cutoff from 0.4 to 3.0 V was also measured. In this voltage range, the capacity contribution of sulfur was measured . As shown in Figure S30 in the Supporting Information, the NiSA/S/C nanotubes also maintained good cycling performance, delivering a capacity of 901.1 mAh g −1 based on the mass loading of sulfur.…”

“…The improved kinetics motivated us to evaluate the potassium storage performance of the NiSA/S/C nanotubes. Figure S27 and Figure E in the Suppoting Information exhibit the CV and charge/discharge curves, respectively, which suggest a reversible electrochemical behavior (see the Supporting Information for detailed discussion) . The NiSA/S/C electrode delivers a high discharge capacity of 1040.9 mAh g −1 based on the total mass of the NiSA/S/C nanotubes, accompanying with an initial coulombic efficiency of 64.4 %.…”

“…Xu designed a microporous carbon to confine the small‐molecule sulfur (S 2 , S 3 ) with content of 20 wt %, which delivered a reversible capacity of 1198.3 mA h g −1 based on sulfur mass within voltage window from 0.5 to 3 V (vs. K + /K). The capacity retained 72.5 % after 150 cycles because of the sulfur stabilization effect of microporous carbon sphere . Although great advances were made at the early stage of the PIBs, exquisite structure and ingredient designs for further enhancing the electrochemical performance with respect to high capacity, good rate performance and cycling stability are highly imperative and significant.…”