Preparation method and application of FeS-FeSO4 composite material

Abstract

The invention discloses a preparation method and application of a FeS-FeSO4 composite material, and the preparation method comprises the following steps: step 1, precursor construction: heating ferrous sulfate heptahydrate to 400-500 DEG C in an inert gas atmosphere, calcining for 2-8 hours, and then cooling to room temperature to obtain an iron-based oxide / sulfate composite material Fe2O3-FeSO4 as a precursor material; and step two, vulcanization reaction: performing vulcanization treatment on the precursor material through a heat vulcanization treatment process to obtain the FeS-FeSO4 composite material. Aiming at the key problems of capacity stability and the like of the FeS negative electrode material in the lithium storage process, based on the construction of FeSO4 heterogeneous coupling, the structure stability of the FeS material is enhanced, the ion transport is enhanced, and the shuttle effect is inhibited, so that the lithium storage stability of the material is improved.

Description

Technical Field

[0001] The present invention relates to the field of electrode material preparation, and in particular to a preparation method and application of a FeS-FeSO4 composite material. Background Art

[0002] As the global economy continues to develop, people's demand for energy is also growing. The supply of oil, coal and natural heat sources is limited. Long-term over-exploitation will lead to resource depletion and cause a crisis of non-renewable energy such as natural gas. Driven by the dual support of multinational policies and technological development, lithium-ion batteries have become one of the key energy storage technologies and are widely used in important fields such as electric vehicles, portable devices, and smart grids.

[0003] The capacity of traditional graphite anode materials (theoretical capacity of about 372 mAh g-1) is difficult to meet the higher requirements of energy density and cycle performance in the future. Developing high-performance anode materials to replace traditional graphite anode materials is one of the necessary means to achieve high energy density and excellent cycle performance lithium-ion battery systems.

[0004] In the process of developing negative electrode materials, researchers found that FeS negative electrode materials have potential advantages such as high theoretical capacity (about 609 mAhg-1) and low cost, and are considered to be one of the strong competitors that are expected to replace graphite negative electrode materials, with broad application prospects. One of the current technical bottlenecks of FeS negative electrode materials is energy storage stability. Especially when deep charging / discharging at high current density, the reversibility of the electrode reaction is reduced due to structural changes, shuttle effects, reaction kinetic hysteresis, etc., and even a sudden drop in capacity. The resulting short cycle life and energy density attenuation are heavy shackles that limit the progress of FeS negative electrode materials. Designing and preparing new FeS-based negative electrode materials with stable structure, efficient reaction kinetics, and low shuttle effects is of great significance to promoting the development of high energy density and cycle performance lithium-ion battery technology.

[0005] Related studies have shown that the introduction of FeSO4 can not only ensure the structural stability of the electrode material, but also the sulfate generated by the reaction between sulfate ions and lithium ions can build an efficient lithium ion transmission channel, promote the rapid migration of lithium ions, and improve the reaction kinetics of the material. 2+ It can form a complex with polysulfide in the electrolyte, slowing down the diffusion of polysulfide, and the easy oxidation property of FeSO4 can directly react with polysulfide and also form an anchoring effect. In addition, the composite structure constructed with FeSO4 can form a certain spatial confinement effect, effectively physically intercepting polysulfide and inhibiting the occurrence of the shuttle effect.

[0006] Due to the easy solubility (water solvent) and thermal decomposition characteristics of FeSO4, traditional liquid phase synthesis and heat treatment processes are difficult to synthesize and maintain the physical structure of FeSO4 composite materials, which brings certain challenges to the composite of FeSO4 and FeS. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a preparation method and application of a FeS-FeSO4 composite material.

[0008] The technical solution of the present invention is: A method for preparing a FeS-FeSO4 composite material comprises the following steps: Step 1: Precursor construction: ferrous sulfate heptahydrate is heated to 400-500° C. in an inert gas atmosphere and calcined for 2-8 hours, and then cooled to room temperature to obtain an iron-based oxide / sulfate composite material Fe2O3-FeSO4 as a precursor material; Step 2: sulfurization reaction: the precursor material is subjected to sulfurization treatment through a thermal sulfurization process to obtain a FeS-FeSO4 composite material.

[0009] A further improvement is that the purity of the ferrous sulfate heptahydrate is ω (FeSO4·7H2O)≥99%.

[0010] As a further improvement, in step 1, the inert gas is one or more of nitrogen, helium or argon.

[0011] As a further improvement, in step 1, the heating rate is 2-8°C / min.

[0012] As a further improvement, the method of the thermal vulcanization treatment process is as follows: the precursor material is placed downstream of a tubular furnace, a sulfur source is placed upstream, and heat treated at 350°C for 2 hours in a nitrogen atmosphere, and the FeS-FeSO4 composite material is obtained after cooling in the furnace.

[0013] In a further improvement, the sulfur source is thiourea or sublimated sulfur; and the mass ratio of the precursor material to the sulfur source is 1:5.

[0014] A use of a FeS-FeSO4 composite material, the preparation method of the FeS-FeSO4 composite material is as described above; the FeS-FeSO4 composite material is used as a negative electrode material for a lithium battery.

[0015] Compared with the prior art, the present invention has the following obvious advantages: The present invention aims at key issues such as capacity stability of FeS negative electrode materials during lithium storage, and based on the construction of FeSO4 heterogeneous coupling, enhances the structural stability of FeS materials, strengthens ion transport and inhibits the shuttle effect, thereby improving the lithium storage stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the construction of the FeS-FeSO4 composite material of the present invention Figure 2 This is an X-ray diffraction (XRD) phase analysis diagram of the FeS-FeSO4 composite material of Example 1 of the present invention; Figure 3 The FeS-FeSO4 composite material of the present invention is 100mA g -1 Charge and discharge performance diagram under current density. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application. Example 1

[0018] A method for synthesizing a FeS-FeSO4 composite material of the present invention comprises the following steps: Step S1, preparing a precursor material based on the thermal decomposition of FeSO4·7H2O, grinding 5 g of FeSO4·7H2O (ω (FeSO4·7H2O) ≥ 99%) material in a mortar, grinding for 30 min, placing in a tube furnace, and adjusting the heating rate to 5 °C min -1 , heated to 400℃, maintained for 8 h, and collected the precursor sample (about 500 mg) after natural cooling in the furnace; during the heating process, FeSO4·7H2O underwent thermal decomposition reaction, including two processes: dehydration decomposition of FeSO4·7H2O (FeSO4·7H2O→FeSO4·xH2O, 0≤x<7) and thermal decomposition of FeSO4 (FeSO4→Fe2O3). The Fe2O3-FeSO4 precursor with different Fe2O3 proportions can be obtained by controlling the holding time.

[0019] Step S2, thermal vulcanization conversion, placing the precursor material downstream of the tube furnace, placing 2.5 g of thiourea (or sublimated sulfur) upstream, placing the precursor material downstream, heat treating at 350 ° C for 2 h in a nitrogen atmosphere, and obtaining FeS-FeSO4 composite material after cooling with the furnace; thiourea or sublimated sulfur can effectively prevent the further decomposition of FeSO4 components, ensuring the construction of the composite structure After the mixed solution 1 is cooled to room temperature, it is slowly added dropwise into deionized water to cause phase separation, filtered, freeze-dried and shaped to obtain a micron-structured tin source-polymer hierarchical porous skeleton precursor. Example 2

[0020] The FeS-FeSO4 composite material prepared in Example 1 was mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride PVDF) in a mixing ratio of 7:2:1, and an active material slurry was coated on a copper foil and dried (vacuum drying conditions: temperature 90 ° C, time 12 h) to obtain a negative electrode sheet material; The negative electrode sheet is cut, a lithium metal sheet is used as the counter electrode, and the button cell is assembled in a glove box using a diaphragm, an electrolyte, and a button cell packaging shell (CR2032). Comparative Example 1

[0021] Corresponding to the application method of Example 2, pure FeS was used to prepare electrode materials and assemble batteries.

[0022] The negative electrode materials of Example 2 and Comparative Example 1 were tested at 100 mA g using the Xinwei test system. -1 Cycling performance of pure FeS anode material under current density; (1) 100 mA g -1 The cycling performance of Sn / C negative electrode materials was measured at current density; Please refer to Figure 3 , is a comparison chart of the cycle performance of FeS-FeSO4 composite materials and pure FeS in lithium-ion batteries. Figure 3 It can be confirmed that the FeS-FeSO4 composite material of the present invention exhibits excellent cycle stability when applied to lithium-ion batteries at 100 mA g -1 At a current density of 1.5 %, the first discharge capacity can reach 1258 mA h g -1 , after 70 cycles, it can maintain 837mA hg -1 The reversible specific capacity, after stabilization (from the 5th cycle), the capacity retention rate reaches 86%, and the coulombic efficiency is almost 100%; the FeS negative electrode material used as a comparison object is applied to lithium-ion batteries, although the first discharge specific capacity is 1158 mA h g -1 After 70 cycles, the reversible specific capacity decreased to 189 mA h g -1 The capacity retention rate is only 50%, and the reversible capacity is far less than that of the FeS-FeSO4 negative electrode. From the perspective of capacity, the difference in energy storage stability between the two electrodes is well explained, and the strengthening effect of FeSO4 has a good strengthening effect on the energy storage performance of FeS.

[0023] In the present invention, the introduction of FeSO4 can not only ensure the structural stability of the electrode material, but also the sulfate generated by the reaction between sulfate ions and lithium ions can construct an efficient lithium ion transmission channel, promote the rapid migration of lithium ions, and improve the reaction kinetics of the material.

[0024] The composite structure constructed by FeSO4 can form a certain spatial confinement effect, effectively physically intercept polysulfide and inhibit the occurrence of shuttle effect; Fe in FeSO4 2+ It can form complexes with polysulfides in the electrolyte to slow down the diffusion of polysulfides. The easily oxidizable property of FeSO4 can directly react with polysulfides and also form an anchoring effect. Combining the spatial confinement and chemical anchoring of the FeSO4 component is expected to achieve physical and chemical dual constraints on polysulfides.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a FeS-FeSO4 composite material, characterized in that: The steps include: Step 1: Precursor construction: ferrous sulfate heptahydrate is heated to 400-500° C. in an inert gas atmosphere and calcined for 2-8 hours, and then cooled to room temperature to obtain an iron-based oxide / sulfate composite material Fe2O3-FeSO4 as a precursor material; Step 2: sulfurization reaction: the precursor material is subjected to sulfurization treatment through a thermal sulfurization process to obtain a FeS-FeSO4 composite material.

2. The method for preparing the FeS-FeSO4 composite material according to claim 1, characterized in that: The purity of the ferrous sulfate heptahydrate ω (FeSO4·7H2O) is ≥ 99%.

3. The method for preparing the FeS-FeSO4 composite material according to claim 1, characterized in that: In step 1, the inert gas is one or more of nitrogen, helium or argon.

4. The method for preparing the FeS-FeSO4 composite material according to claim 1, characterized in that: In the step 1, the heating rate is 2-8°C / min.

5. The method for preparing the FeS-FeSO4 composite material according to claim 1, characterized in that: The method of the thermal vulcanization treatment process is as follows: the precursor material is placed downstream of a tubular furnace, a sulfur source is placed upstream, and a heat treatment is performed at 350° C. for 2 hours in a nitrogen atmosphere, and the FeS-FeSO4 composite material is obtained after cooling in the furnace.

6. The method for preparing the FeS-FeSO4 composite material according to claim 5, characterized in that: The sulfur source is thiourea or sublimated sulfur; the mass ratio of the precursor material to the sulfur source is 1:

5.

7. Use of a FeS-FeSO4 composite material, characterized in that: The preparation method of the FeS-FeSO4 composite material is as described in any one of claims 1-6; the FeS-FeSO4 composite material is used as a negative electrode material for a lithium battery.

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