Scale Synthesis of Uniform Fe1-xS Nanomaterials and Its Application in Sodium Ion Batteries

【introduction】

In order to make up for the limitations of lithium ion batteries in the direction of energy storage, sodium ion batteries have attracted widespread attention due to their rich sodium resources, wide distribution and low cost, and are expected to be applied in large-scale energy storage. The development of high performance anode materials is critical to the commercialization of sodium ion batteries. Among the well-received sodium ion battery anode materials, iron sulfide has the characteristics of high theoretical capacity, highly reversible redox characteristics, abundant natural resources and environmental friendliness, and is one of the most promising new anode materials. It is well known that nanostructures play a crucial role in improving the electrochemical performance of nanomaterials. However, due to the complicated experimental process, the large-scale synthesis of nanomaterials with special nanostructures has seriously restricted the practical use of nanomaterials.

[Introduction]

Recently, Prof. Peng Shengjie from Nanjing University of Aeronautics and Astronautics designed and prepared Fe1-xS nanomaterials with uniform morphology for large-scale production through one-step vulcanization. As a negative electrode material for sodium ion batteries, this material exhibits excellent rate performance and good cycle stability (after a 2000 week cycle, the reversible capacity retention can still reach approximately 100% at a current density of 10 A g-1). Kinetic analysis shows that the decisive role of tantalum capacitor is the key to the material's good rate performance. At the same time, the mechanism of sodium storage of Fe1-xS nanomaterials was studied by in-situ XRD characterization. In addition, Na0.6Co0.1Mn0.9O2 is matched with Fe1-xS to form a full cell of sodium ion battery, showing high specific capacity and cycle stability (at a current density of 20 mA g-1, after 100 cycles, capacity Maintain at about 380 mAh g-1). The work was published online in the journal Nano Energy (2017, 37, 81-89) under the title "Large-scale synthesis of highly uniform Fe1-xS nanostructures as a high-rate anode for sodium ion batteries".

[Graphic introduction]

Figure 1. Physical characterization of Fe1-xS nanomaterials

(a, b) scanning electron microscope (SEM) images of Fe1-xS nanomaterials at different magnifications; (c, d) projection electron microscopy (TEM) images of Fe1-xS nanomaterials, inset: electron diffraction images; Eg) EDX surface scan of each element of the Fe1-xS nanomaterial.

Figure 2. Electrochemical performance of Fe1-xS nanomaterials

(a) CV diagram of Fe1-xS nanomaterial; (b) charge and discharge curve; (c) cycle stability curve; (d) AC impedance diagram; (e) Cycle stability curve under different charge and discharge rates.

Figure 3. Kinetic properties of Fe1-xS nanomaterials

(a) rate performance curve of Fe1-xS nanomaterials; (b) charge-discharge curve at corresponding magnification; (c) CV curve at different sweep speeds; (d) log i vs. log v curve at corresponding redox peaks (e) contribution of tantalum capacitance at different sweep speeds; (f) ratio of CV curve and corresponding tantalum capacitance when the sweep speed is 0.5 mV s-1.

Figure 4. Study on the mechanism of sodium storage in Fe1-xS nanomaterials

(a) In-situ XRD pattern of charge and discharge in the first week; (b) In-situ XRD pattern of charge and discharge in the third week; (c) XRD pattern at a certain charge and discharge potential.

Figure 5. Sodium ion full cell performance of Fe1-xS nanomaterials

(a) Comparison of charge and discharge curves of Na0.6Co0.1Mn0.9O2 positive electrode and Fe1-xS negative electrode; electrochemical performance of Na0.6Co0.1Mn0.9O2/Fe1-xS full cell at current density of 20 mA g-1 (b, c) charge and discharge curve; (d) cycle stability curve.

【summary】

In this study, a homogeneous Fe1-xS nanostructure was successfully prepared by a simple one-step vulcanization method. As a sodium ion battery electrode material, it exhibits good rate performance and long cycle stability. It is worth noting that its excellent sodium storage performance is also fully demonstrated in the sodium ion full battery, further indicating its potential commercial application value.