Dynamic Multistage Coupling of FeS₂/S Enables Ultrahigh Reversible Na–S Batteries

Abstract

The fundamental challenges that coexisted around sulfur cathode energy storage systems, are the severe polysulfide dissolution and low reactivity resulting in poor reversibility and short cycle life, specifically, in inexpensive sodium ion batteries. Herein, the solution‐processed synthesis of ultra‐high intimate contacted FeS2/S architecture is reported and evolution of the dynamic multistage coupling between the FeS2 and S in sodium–sulfur batteries is revealed. Atomic visualization and in situ spectroscopy conclude that: NaxFeS2 (0 <x ≤1) effectively captures sodium polysulfides and promotes the conversion of S8 to Na2S4 to Na2S2/Na2S; simultaneously, the presence of Na2S2/Na2S traps the continuous growth of iron grains during continuously discharging to 0.4 V, thereby boosting the reversibility and high capacity. Moreover, the density functional theory further analyses the unique coupling effect of Na2Sx with different intermediate states of FeS2. The electrode with unique structure and dynamic coupling exhibits outstanding cycle reversibility and extremely long life, which delivers a reversible capacity of 860 mAh g−1 after 1000 cycles with no capacity decay at 0.5 A g−1. Even under a practical areal capacity of 4 mAh cm−2, it still shows pretty‐well cycling stability.

In Situ Reconstruction of Electrocatalysts for Lithium–Sulfur Batteries: Progress and Prospects

“…Different from the surface gelation of MoS 2 , a reversible phase transformation of metal sulfide FeS 2 to Na x FeS 2 (0 < x ≤1) was observed by Chen et al in Na-S batteries. [189] The results of in situ Raman spectra indicated that the ultrahigh intimate contacted FeS 2 /S architecture prompted the reversible formation and decomposition of Na 2 S 2 /Na 2 S (Figure 10f,g). By contrast, with the commercial FeS 2 substrate, only Na 2 S 4 was [183] Copyright 2021, Wiley-VCH.…”

Binder‐Induced Ultrathin SEI for Defect‐Passivated Hard Carbon Enables Highly Reversible Sodium‐Ion Storage

“…[1,2] The key electrode materials have been fully explored in the past few years and are being used in the process of industrialization, including important cathodes (transition metal oxides (TMOs), polyanionic compounds, and Prussian blue analogues (PBAs)) [3] and hard carbon (HC) anode. [4,5] However, HC suffers the low initial Coulombic efficiency (ICE), poor cycle stability, and rate performance in typical organic electrolytes [6] given that the formed solid electrolyte interphase (SEI) on the defect-rich HC is uneven, thick, and easy to break because of its poor mechanical strength. The resulting excessive consumption of electrolytes and increasing interface impedance reduce its ICE, cycle stability, and reaction kinetics.…”

Sulfur–Carbon Electrode with PEO‐LiFSI‐PVDF Composite Coating for High‐Rate and Long‐Life Lithium–Sulfur Batteries

“…To overcome the aforementioned shortcomings, extensive research has been conducted on the design and assembly technology of composite sulfur cathode with high mechanical stability and long‐cycling reliability. This includes the kinetics of the sulfur cathode, [ 4 ] doping of elements carbon or nitrogen, in suit coating with inorganic or organic materials on sulfur or adding an interlayer between the cathode and separator. [ 2b,5 ] Surface coating technology, as a common electrode treatment method, has the remarkable advantages such as strong universality, controllable processing cost, and easy process implementation.…”