Graphene oxide coated positive electrode material for thermal battery and preparation method of graphene oxide coated positive electrode material

Abstract

The invention relates to a graphene oxide coated positive electrode material for a thermal battery and a preparation method of the graphene oxide coated positive electrode material, and solves the problems of low utilization rate, limited discharge capacity and the like of the existing thermal battery positive electrode material. Comprising 30%-80% of an active positive electrode material, 10%-40% of an ionic conductive agent, 1%-20% of lithium oxide and 1%-10% of an electronic conductive agent, and the ionic conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF and LiCl-KCl. The preparation method comprises the following steps: (1) dissolving a FeS2 positive electrode material in a distilled water solution, adding graphene oxide, and stirring to obtain a FeS2 / GO dispersion liquid; (2) freezing the FeS2 / GO dispersion liquid in a freeze dryer, and carrying out a sublimation drying process to obtain FeS2 / GO composite powder; (3) putting the FeS2 / GO composite powder into a tubular furnace, and performing a high-temperature reduction process of GO in an argon environment to obtain FeS2 / RGO composite powder; and (4) uniformly mixing the FeS2 / RGO composite powder, the CoS2 powder, an ionic conductive agent and lithium oxide, and performing lithiation, sieving and drying treatment to obtain the graphene oxide coated thermal battery composite positive electrode material. The discharge performance of the thermal battery positive electrode material is improved.

Description

Technical Field

[0001] The invention relates to a graphene oxide coated positive electrode material for a thermal battery and a preparation method thereof, belonging to the technical field of thermal batteries. Background Art

[0002] At present, the mainstream positive electrode materials of thermal batteries are mainly transition metal sulfides such as FeS2 and CoS2. They are an important component of thermal batteries and account for a large proportion of electrode materials. Therefore, the performance of positive electrode materials largely determines the performance of batteries. However, sulfide positive electrode materials have poor conductivity, which affects the release of the actual capacity of the battery. Among them, CoS2 positive electrode materials are artificially synthesized in the laboratory and have good conductivity. The conductivity at room temperature is 500S.cm -1 The FeS2 cathode material is extracted from natural pyrite, with large particle size and uneven distribution, poor conductivity, and only 28S.cm at room temperature. -1 Therefore, improving the conductivity of the positive electrode material is particularly important for improving the performance of thermal batteries and developing the thermal battery market. Summary of the invention

[0003] The present invention proposes a graphene oxide coated positive electrode material for a thermal battery and a preparation method thereof, which solves the technical problems that restrict the development of thermal batteries, such as the poor conductivity of the positive electrode material of the thermal battery resulting in low utilization rate and limited actual discharge capacity.

[0004] The present invention is achieved by the following technical solutions:

[0005] A graphene oxide coated positive electrode material for a thermal battery comprises two active positive electrode materials of sulfides FeS2 and CoS2, lithium oxide, an ionic conductive agent and an electronic conductive agent, wherein the mass percentages are: 30% to 80% of the active positive electrode material, 10% to 40% of the ionic conductive agent, 1% to 20% of the lithium oxide, and 1% to 10% of the electronic conductive agent, wherein the ionic conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF, and LiCl-KCl, and the electronic conductive agent is graphene oxide.

[0006] A method for preparing a graphene oxide-coated positive electrode material for a thermal battery comprises the following steps:

[0007] (1) dissolving FeS2 cathode material in a distilled water solution, adding a certain proportion of graphene oxide, and stirring for a certain period of time to uniformly mix the mixture to obtain a FeS2 / GO dispersion;

[0008] (2) placing the FeS2 / GO dispersion in a freeze dryer and freezing it, and performing a sublimation drying process after the water in the material forms ice crystals to obtain a FeS2 / GO composite powder;

[0009] (3) placing the FeS2 / GO composite powder into a tubular furnace, performing a high-temperature reduction process of GO under an argon environment, and obtaining a FeS2 / RGO composite powder after cooling;

[0010] (4) The FeS2 / RGO composite powder, CoS2 powder, ion conductive agent and lithium oxide are mixed evenly, and after lithiation, screening and drying, a graphene oxide-coated thermal battery composite positive electrode material is obtained.

[0011] Wherein, in step (1), the proportion of graphene oxide is 1% to 30%, and the stirring time is 1 to 24 hours.

[0012] Wherein, in step (3), the high temperature reduction temperature is 100 to 600° C. and the time is 1 to 15 hours.

[0013] Wherein, in step (4), the mass ratio of FeS2 / RGO, CoS2, ion conductive agent and lithium oxide powder is 20% to 80%: 20% to 80%: 10% to 40%: 10% to 20%.

[0014] Wherein, in step (4), the lithiation temperature is 100 to 600° C. and the time is 1 to 15 hours.

[0015] The present invention has the following characteristics and positive effects:

[0016] The positive electrode material coated with graphene oxide for a thermal battery of the present invention has the following advantages:

[0017] (1) The present invention provides a positive electrode material coated with graphene oxide for a thermal battery. By introducing graphene oxide into the positive electrode material and performing a subsequent high-temperature reduction process, the specific surface area and conductivity of the positive electrode material are increased, the electrochemical polarization during the discharge process is reduced, and the discharge performance of the positive electrode material of the thermal battery is improved.

[0018] (2) The present invention is a thermal battery positive electrode material coated with graphene oxide. The positive electrode powder and the crystalline dispersion of graphene oxide are directly converted into a gas state without passing through a liquid state by freeze-drying and sublimation. Compared with the heating and drying method, the thermal motion of molecules is avoided, ensuring that the structure and morphology of the graphene oxide wrapped in the positive electrode material are not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 XRD patterns of graphene oxide (GO) and reduced graphene oxide (RGO) in the present invention;

[0020] Figure 2 is the Raman spectra of graphene oxide (GO) and reduced graphene oxide (RGO) in the present invention;

[0021] Figure 32 are SEM images of graphene oxide (a) and reduced graphene oxide (b) in the present invention;

[0022] Figure 4 XRD patterns of FeS2 and FeS2 / RGO in the present invention;

[0023] Figure 5 SEM images of FeS2 (a) and FeS2 / RGO (b) in the present invention;

[0024] Figure 6 It is the discharge performance diagram of FeS2-CoS2 and FeS2 / RGO-CoS2 positive electrode single cell in the present invention; DETAILED DESCRIPTION

[0025] Example:

[0026] The present invention provides a method for preparing a graphene oxide-coated positive electrode material for a thermal battery, and the specific steps are as follows:

[0027] S1. Dissolve FeS2 cathode material in distilled water solution, add a certain proportion of graphene oxide, and stir for 2 h to make it evenly mixed to obtain FeS2 / GO dispersion.

[0028] S2, placing the dispersion in a freeze dryer and drying for 24 hours to obtain FeS2 / GO composite positive electrode powder;

[0029] S3, placing the FeS2 / GO composite powder into a tubular furnace, performing a high-temperature reduction process of graphene oxide at 500°C in an argon environment, and obtaining a FeS2 / RGO composite positive electrode powder after cooling;

[0030] S4. The FeS2 / RGO composite powder, CoS2 powder, ion conductive agent and lithium oxide are mixed evenly in a certain proportion, and after lithiation, screening and drying, a thermal battery composite positive electrode material coated with graphene oxide can be obtained.

[0031] The battery was assembled with the thermal battery composite positive electrode material coated with graphene oxide prepared in the example. The single cell consists of two positive electrode materials (FeS2 and CoS2), an ion conductor (LiCl-LiBr-LiF eutectic powder), an electronic conductor (graphene oxide), an electrolyte separator, a baffle ring, a thermal buffer layer, a negative electrode material and a current collector. Take 1g of the thermal battery composite positive electrode material in Example 1, 0.9g of electrolyte, 0.6g of negative electrode lithium boron alloy, plus a baffle ring and a current collector to form a single cell with a diameter of 31mm. The single cell was discharged at a constant current density of 300mA / cm2 in a 450℃ hot press furnace, and the lower cut-off voltage was 1.3V.

[0032] Figure 1The XRD patterns of graphene oxide (GO) and high temperature reduced graphene oxide (RGO) in the present invention show that graphene oxide has an obvious diffraction peak near 11°, corresponding to the (001) crystal plane of graphene oxide, while the peak position of graphene after high temperature thermal reduction disappears near 11°, and a diffuse peak near 25° is presented, close to the (002) peak of graphite at 26.53°, indicating that most of the oxygen-containing functional groups are removed after reduction. Compared with GO, the characteristic peak of RGO is very weak, which may be due to its low density, loose structure, and difficulty in compaction, so it is impossible to obtain sufficient signal strength in the test.

[0033] Figure 2 The Raman spectroscopy experiments of graphene oxide (GO) and high-temperature reduced graphene oxide (RGO) confirmed that most of the oxygen-containing groups in GO have been removed after thermal reduction, thus forming a reduced graphene oxide morphology with a high degree of exfoliation and very thin layers. However, the diffraction peak of GO is still relatively strong, indicating that the generated RGO still has many defects. Figure 3 From the SEM images of graphene oxide (GO) and high-temperature reduced graphene oxide (RGO), it can be seen that compared with graphene oxide, reduced graphene oxide is in a curled state, and wrinkles caused by intrinsic undulations on the surface can be seen, indicating that high-temperature reduction obtains reduced graphene oxide with a high degree of exfoliation and very thin flakes.

[0034] Figure 4 The XRD spectrum of FeS2 / RGO composite cathode material shows a C diffraction peak in the XRD spectrum of the product, which is the diffraction peak of reduced graphene oxide in the composite cathode material. Figure 5 As shown in the SEM image, it can be seen that the FeS2 positive electrode material particles are evenly distributed on the graphene, forming a conductive network on the surface of the positive electrode material, so that the active points of the positive electrode material can contact the electrolyte more and faster, greatly increasing the conductivity of the positive electrode material and improving the battery discharge performance.

[0035] Figure 6 The discharge performance diagram of FeS2-CoS2 and FeS2 / RGO-CoS2 positive electrode single cell. The discharge results show that when the current density is 300mA / cm2, the cut-off voltage is 1.5V, the discharge time of FeS2-CoS2 and FeS2 / RGO-CoS2 single cells are 415s and 546s respectively, and the discharge specific capacity is 214mAh.g-1 and 282mAh.g-1 respectively, indicating that the discharge time of FeS2 / RGO-CoS2 single cell is 24.1% higher than that of FeS2-CoS2 single cell.

[0036] In summary, the composite positive electrode material coated with graphene oxide for a thermal battery of the present invention can discharge stably for a long time at a high current density. Compared with the positive electrode single cell control sample without graphene oxide, it can effectively extend the working time of the thermal battery and has extremely high engineering application value.

Claims

1. A graphene oxide coated positive electrode material for a thermal battery, characterized in that: The invention comprises active positive electrode materials of two sulfides FeS2 and CoS2, lithium oxide, ionic conductive agent and electronic conductive agent, wherein the mass percentages are: 30% to 80% active positive electrode materials, 10% to 40% ionic conductive agent, 1% to 20% lithium oxide, 1% to 10% electronic conductive agent, the ionic conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF and LiCl-KCl, and the electronic conductive agent is graphene oxide.

2. A method for preparing a graphene oxide coated positive electrode material for a thermal battery, characterized in that: The following steps are involved: (1) dissolving FeS2 cathode material in a distilled water solution, adding a certain proportion of graphene oxide, and stirring for a certain period of time to uniformly mix the mixture to obtain a FeS2 / GO dispersion; (2) placing the FeS2 / GO dispersion in a freeze dryer and freezing it, and performing a sublimation drying process after the water in the material forms ice crystals to obtain a FeS2 / GO composite powder; (3) placing the FeS2 / GO composite powder into a tubular furnace, performing a high-temperature reduction process of GO under an argon environment, and obtaining a FeS2 / RGO composite powder after cooling; (4) The FeS2 / RGO composite powder, CoS2 powder, ion conductive agent and lithium oxide are mixed evenly, and after lithiation, screening and drying, a graphene oxide-coated thermal battery composite positive electrode material is obtained.

3. The method for preparing a graphene oxide coated positive electrode material for a thermal battery according to claim 2, wherein: In step (1), the proportion of graphene oxide is 1% to 30%, and the stirring time is 1 to 24 hours.

4. The method for preparing a graphene oxide coated positive electrode material for a thermal battery according to claim 2, wherein: In step (3), the high temperature reduction temperature is 100 to 600° C. and the time is 1 to 15 hours.

5. The method for preparing a graphene oxide coated positive electrode material for a thermal battery according to claim 2, wherein: In step (4), the mass ratio of FeS2 / RGO, CoS2, ion conductive agent and lithium oxide powder is 20% to 80%: 20% to 80%: 10% to 40%: 10% to 20%.

6. The method for preparing a graphene oxide coated positive electrode material for a thermal battery according to claim 2, wherein: In step (4), the lithiation temperature is 100 to 600° C. and the time is 1 to 15 hours.

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