Paper Discussion

Petal-like 3D SnS2 via ratio control and their Supercapacitor behavior

Evolution of hierarchically formed petal-like 3 dimensional layer structures for SnS2 via ratio control of Sn/thiourea and their electrochemical charge storage behavior

About work-

This work reports thiourea (TU) based layer structure material performance of tin sulfide electrode material via the one-step solvothermal method. Structural, morphology, and electrochemical performance were studied thoroughly. Prepared layered SnS2 electrode material exhibits the highest specific capacitance of 1403 Fg-1 at 1 mVs-1 and retains an outstanding cyclic retention value of 85.87% after 5000 cycles. Promising electrochemical behaviors of 2D SnS2 material via facile and direct grown optimization-based method make it a potential candidate for the next-generation energy storage system.  

Overview of the research question-

  • Using a layered structure of tin sulfide electrode material for high-performance supercapacitors, we study the effect of thiourea on the electrode structure.
  • This study reports first-ever optimizations of the TU ratio for SC electrode material. It covers substrate integrity, material layered structure optimization, layer thickness observation, and excellent electrode material and device performances.
  • As observed, optimized Sn: TU ratio (1:2) demonstrates ultra-thin petal-like microstructure and shows the highest specific capacitance of 1403 Fg-1 at 1 mVs-1 scan rate and maintains excellent 85.87 % retention even after 5000 cycles.
  • The TU ratio was used to grow hierarchically layered, vertically grown ultrathin petals.
  • Further, the SSC device was assembled and showcased with commercial LED illumination, showing the potential of this novel electrode material.

Description of study design-

  • The tin sulfide-based compounds with different levels of thiourea as Sulphur sources were synthesized successfully.
  • The discrete nanostructure obtained in a 1:2 ratio sample (SNS12) exhibits better electrochemical performance.
  • SNS12 exhibits the highest specific capacitance of 1403 Fg-1 at 1 mVs-1 and is extremely cyclically stable, with cyclic stability of 85.87%, after 5000 cycles.
  • Due to the desirable discrete layering, they are resulting in a shorter ion-diffusion pathway and a more accessible electrode-electrolyte interface.
  • Furthermore, fabricated SSC devices are highly significant for lightening commercial LEDs.
  • An excellent capacitance performance, cyclic stability, and a beneficial nanostructure make this an ideal material for practical applications.

Key findings-

In this work, we examine various aspects in terms of material and device-level performance that will facilitate improvements in electrochemical efficiency; 

(i) A one-step solvothermal method displaying favorable layer electrode material morphology that is easy, inexpensive, scalable, and requires no template, 

(ii) SnS2 (1:2 ratio) offers high accessibility optimized interfacial contact, an improved performance due to reduced internal resistance of less thin layers, 

(iii) With simple optimization steps, layer structure and facet thickness, an important parameter of the layered structure, are optimized, 

(iv) The issue of Brittleness in Nickel foam substrate is resolved with structural level substrate material integrity, and 

(v) LED demonstrations to provide device-level real-time evidence of material performance as an effective energy storage system.

Generalized results-

  • XPS characterization was performed on all prepared electrode materials to evaluate their surface chemical compositions. 
  • From the FESEM micro-image, it is evident that the thiourea ratio changed the layered structure of the electrode material such that it became packed rather than well distributed. 
  • An interesting aspect of the electrode material is the fact that the morphology changes as the TU ratio increases. 
  • During the nucleation of materials, the top sulfide layer allows the growth of a new layer with more TU content due to the low electron conductivity of the bottom layer. 
  • With changes in thiourea concentration, the SNS sample layers' properties are correlated with the nucleation process' kinetics. 
  • During low-thiourea concentrations, the growth process is prolonged, resulting in a thinner and more homogenous layer. 
  • Microstructures of ultra-thin Patel flowers can provide greater electrode-electrolyte interface access for better electrochemical performance.
  • Observed higher specific capacitance in sample SNS12 indicates more accessible charge storage at the surface of its distributed layering structure. 
  • Due to its thin-layer structure, the electrode/electrolyte interface can realize rapid ion intercalation and charge transfer, making it an electrode material with high-performance potential.

Future work perspectives-

  • Study results suggest that a 3D SnS2 electrode material with optimal layering capability and a controllable protocol for Sn/TU ratio modulation is useful for the envisioned energy storage applications.
  • It has been found that layered electrodes synthesized with favorable properties can be used for next-generation energy storage.

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