Electrochemical Mechanism for FeS2/C Composite in Lithium Ion Batteries with Enhanced Reversible Capacity

Abstract

Nanoscale FeS 2 was synthesized via a simple hydrothermal method and was decorated by hydrothermal carbonization (FeS 2 @C). The structural properties of the synthesized materials detected by X-ray diffraction (XRD), together with the morphologies characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the hydrothermal carbonization only had an impact on the morphology of pyrite. Additionally, the electrochemical performance of the coated pyrite in Li/FeS 2 batteries was evaluated by galvanostatic discharge-charge tests and electrochemical impedance spectroscopy (EIS). The results showed that the initial capacity of FeS 2 @C was 799.2 mAh¨g´1 (90% of theoretical capacity of FeS 2 ) and that of uncoated FeS 2 was only 574.6 mAh¨g´1. XRD and ultraviolet (UV) visible spectroscopy results at different depths of discharge-charge for FeS 2 were discussed to clarify the electrochemical mechanism, which play an important part in Li/FeS 2 batteries.

Production of Quasi-2D Platelets of Nonlayered Iron Pyrite (FeS2) by Liquid-Phase Exfoliation for High Performance Battery Electrodes

“…There are three contributions to the diffusion time in lithium ion half cells, diffusion in the electrolyte within the separator ( ), within the electrolyte in the porous interior of the electrode ( ), and solid state diffusion within the active particles ( ) . Here, L S = 36 μm, L E = 3 μm, and L AM ∼ 50 nm (half the thickness of the thickest platelets, Figure L) are the separator thickness, the electrode thickness, and the diffusion length within the active material, while D Liq ≈ 10 –10 m 2 /s (ref , including porosity and tortuosity) and D Solid = 7 × 10 –17 m 2 /s (ref ) are the Li ion diffusion coefficients in the electrolyte and the active particles. In our case, these diffusion times are approximately τ D1 ≈ 13 s, τ D2 ≈ 0.02 s, τ D3 ≈ 7 s. This crude calculation shows τ D1 + τ D2 + τ D3 ∼ 20 s, quite close to the measured value of τ = 17 s, indicating that τ is completely dominated by diffusion terms and confirms the rate-performance to be predominately diffusion limited.…”

Synthesis, modular composition, and electrochemical properties of lamellar iron sulfides

“…Composites of other iron sulfides with carbon-based materials have shown improved electrochemical performance compared to iron sulfides alone. [67][68][69][70][71][72] As such, composite electrodes comprising 1-Li and multiwalled carbon nanotubes (CNTs) were tested as cathodes for lithium and sodium ion batteries. Electrochemical cycling tests show initial capacities of 450 mAh/g and 600 mAh/g for Li and Na respectively (Figure 4, S18-S21).…”

Development of the Ca/FeS2Chemistry for Thermal Batteries

“…These higher diffusion constants are comparable to the values of between 10 −5 and 10 −7 cm 2 s −1 typically expected for Li(Si)/FeS 2 thermal batteries 31 and several magnitudes greater than traditional organic electrolyte lithium-ion cells, with Li/FeS 2 diffusion coefficients calculated to be between 10 −11 and 10 −13 cm 2 s −1 . 32 To better understand the mechanisms of the cell chemistry, further tests were performed on cells after discharge. These were performed on the cells that contained eutectic within the cathode material, as they had a much greater depth of discharge.…”