Iron Oxide–Iron Sulfide Hybrid Nanosheets as High-Performance Conversion-Type Anodes for Sodium-Ion Batteries

Abstract

Commercialization of Na-ion batteries is hindered by the shortage of abundant and environmentally benign electrode materials with high electrochemical performance. Most of the high-capacity alloying-and conversion-type anodes face rapid capacity loss during prolonged cycling. Herein, we report superior Na-ion storage performance of iron oxide−iron sulfide hybrid nanosheet anodes. Composite anodes containing Fe 2 O 3 −FeS and Fe 3 O 4 −FeS hybrid nanosheets demonstrated high specific capacities of 487 and 364 mA h g −1 , respectively, at a 0.1C rate. These electrodes also exhibited excellent cycling performance, maintaining 330 mA h g −1 after 50 galvanostatic cycles at a 1C rate with ∼100% coulombic efficiency. Mechanistic investigations revealed a high degree of pseudocapacitive-type Na-ion storage (up to ∼65%) in these iron oxide−iron sulfide hybrid nanosheet anodes. Spectroscopic studies confirmed the complete disappearance of the starting oxide and sulfide structures. 57 Fe Mossbauer spectroscopy confirmed Na-ion storage through the conversion reaction of iron oxide−iron sulfide hybrid anodes. Excellent Na-ion storing performance in these hybrid anodes compared with that of previously investigated iron sulfide-and iron oxide-based electrodes is accredited to the enhanced pseudocapacitive Na-ion diffusion caused by the two-dimensional microstructure, high surface area, and crystal mismatch between the iron oxide−iron sulfide nanograins of the hierarchical nanosheets.

Fundamental Insight into the Degradation Mechanism of an rGO-Fe3O4 Supercapacitor and Improving Its Capacity Behavior via Adding an Electrolyte Additive

“…Despite that FeS derived from Fe 3 O 4 has a relatively high theoretical capacity, significant changes in volume during the insertion/extraction of sodium ions lead to a rapid loss of capacity. Hence, the formation of FeS on the electrode surface impedes the contact between Fe 3 O 4 and the electrolyte. , As a result, a solid electrolyte interface (SEI) that inhibits redox reactions is formed on the electrode, thus preventing the Fe 3 O 4 from exerting the pseudocapacitance effect and reducing the specific capacitance. On the one hand, rGO contributes to stabilizing the electrode surface and improves cycling stability .…”

Single-Source-Derived Nitrogen-Doped Soft Carbons for Application as Anode for Sodium-Ion Storage

“…The capacitive effect increased with rise in scan speed, with a value of 58% for the scan speed of 0.2 mV s −1 and a value of 67% for the scan speed of 0.3 mV s −1 , which manifests that the high contribution of the capacitive part benefits the rate performance of the electrode material. 36 The bar plots of capacitive and diffusive contributions are provided in Figure 5d. The electrochemical stability of the materials was tested at a current density of 100 mA g −1 for 500 cycles.…”

Rational Design of Sulfur-Doped Carbon with Expanded Inter-layer Spacing toward Anode Material of Sodium-Ion Batteries

“…Figure c displays the capacitive component of the curve represented by the shaded region. The capacitive contribution enhanced with the sweep rate with 48.38% contribution at a sweep rate of 0.2 mV s –1 and 54.5% contribution at a sweep rate of 0.3 mV s –1 , indicating the capacitive part’s large contribution with an increase in the scan rate Figure d shows the capacitive and diffusive contributions as bar charts.…”

“…The capacitive contribution enhanced with the sweep rate with 48.38% contribution at a sweep rate of 0.2 mV s −1 and 54.5% contribution at a sweep rate of 0.3 mV s −1 , indicating the capacitive part's large contribution with an increase in the scan rate. 39 Figure 5d shows the capacitive and diffusive contributions as bar charts. At a scan rate of 0.1 mV s −1 , the capacitive contribution was determined to be about 43% for CS-1000, while the value was found to be nearly 34% for Cs-1200, as shown in Figures S9 and S10, respectively.…”