Electrode material, preparation method therefor and use thereof

Abstract

The application provides an electrode material and a preparation method and application thereof, wherein the electrode material comprises a Ti3C2Tx base and elemental selenium on the surface of the Ti3C2Tx base. In the application, the elemental selenium is generated in situ on the surface of the Ti3C2Tx base, when the electrode material is used to prepare a lithium-selenium battery, in the cycle process of the lithium-selenium battery, the lithiation and delithiation of selenium are both carried out on the surface of the Ti3C2Tx base, and the functional groups such as hydroxyl and carboxyl on the surface of the Ti3C2Tx base can also capture free selenium, so that the occurrence of the shuttle effect can be effectively reduced, meanwhile, the stacking between the Ti3C2Tx layers in the Ti3C2Tx base can also form a certain barrier effect to hinder the shuttle of selenium, so that the capacity attenuation problem is improved, and the capacity of the prepared lithium-selenium battery can be maintained to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to an electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous consumption of fossil energy, it is necessary to develop new clean energy such as wind energy, solar energy, geothermal energy, etc. However, the use of clean energy cannot be separated from electrochemical energy storage devices, among which lithium ion batteries with safety, high efficiency and environmental protection are widely studied.

[0003] Lithium-selenium battery is a new type of lithium secondary battery system, which uses elemental selenium as the positive electrode and metal lithium as the negative electrode. Selenium is a homologous element of sulfur, has a similar redox mechanism as sulfur, and has a volume specific capacity close to sulfur. In addition, selenium is a semiconductor material, and its electrical conductivity is much higher than that of sulfur. Therefore, lithium-selenium batteries have high volume specific capacity (3253 mAh·cm -3 ) and high electrical conductivity (1×10 -3 S·m -1 ), and have potential application value in energy storage. However, there are still many problems to be solved in lithium-selenium batteries, such as capacity decay and poor cycle performance caused by lithium selenide shuttle effect. SUMMARY

[0004] Embodiments of the present application provide an electrode material and a preparation method and application thereof to improve the technical problems of poor cycle performance and capacity decay of lithium-selenium batteries.

[0005] In a first aspect, embodiments of the present application provide an electrode material, comprising a Ti3C2Tx matrix and elemental selenium on the surface of the Ti3C2Tx matrix.

[0006] In an embodiment, the particle size of the Ti3C2Tx matrix is 0-5 um.

[0007] In a second aspect, embodiments of the present application provide a preparation method of an electrode material, comprising the steps of:

[0008] Mixing selenium powder and an oxidizing agent to prepare a selenous acid solution;

[0009] Mixing Ti3C2Tx matrix, cationic surfactant and water to prepare a Ti3C2Tx matrix solution;

[0010] Mixing the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare an electrode material.

[0011] In an embodiment, the step of mixing the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare the electrode material comprises:

[0012] mixing the selenous acid solution and the Ti3C2Tx matrix solution to obtain a composite solution;

[0013] adding a reducing agent to the composite solution to prepare the electrode material.

[0014] In an embodiment, the ratio of the Ti3C2Tx matrix, the cationic surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150 by mass fraction.

[0015] In an embodiment, the oxidizing agent is hydrogen peroxide with a mass fraction of 30%-50%.

[0016] In an embodiment, the reducing agent is glucose or ascorbic acid.

[0017] In an embodiment, the purity of the selenium powder is greater than 99.9%.

[0018] In an embodiment, the cationic surfactant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, hexadecyl dimethyl ethyl bromide or hexadecyltrimethylammonium chloride.

[0019] In a third aspect, embodiments of the present application provide a lithium-selenium battery comprising the electrode material or the electrode material prepared by the preparation method of the electrode material.

[0020] The beneficial effects of embodiments of the present application are as follows:

[0021] In embodiments of the present application, the electrode material comprises a Ti3C2Tx matrix and elemental selenium on the surface of the Ti3C2Tx matrix. By generating elemental selenium in situ on the surface of the Ti3C2Tx matrix, the elemental selenium on the surface of the Ti3C2Tx matrix is bound by Ti-O bonds. When the electrode material is used to prepare a lithium-selenium battery, in the cycling process of the lithium-selenium battery, lithiumation and delithiation of selenium are both carried out on the surface of the Ti3C2Tx matrix, and the functional groups such as hydroxyl and carboxyl groups on the surface of the Ti3C2Tx matrix can also capture free selenium, thereby effectively reducing the occurrence of shuttle effect. At the same time, the stacking between the Ti3C2Tx layers in the Ti3C2Tx matrix also forms a certain barrier effect to hinder the shuttle of selenium, thereby improving the capacity attenuation problem, and to some extent, the capacity of the prepared lithium-selenium battery can be maintained. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments description. Obviously, the drawings in the following description only show some of the embodiments of the present application, and all other drawings obtained by those skilled in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0023] Figure 1 is a flowchart of the preparation method of the electrode material provided by the embodiments of the present application;

[0024] Figure 2 is a cycle performance diagram of the electrode material prepared by the embodiments and the comparative examples of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort also belong to the protection scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0026] It should be noted that the shuttle effect refers to that the polyselenide dissolved in the electrolyte reaches the lithium negative electrode and is reduced to form low-valence selenide in a chemical manner. Since the low-valence selenide is not limited by polarity, part of the low-valence selenide can return to the selenium positive electrode and be oxidized again. Since the shuttle effect occurs inside the lithium-selenium battery, the charge-discharge capacity and the coulombic efficiency of the lithium-selenium battery are reduced, and at the same time, the self-discharge phenomenon of the lithium-selenium battery is easily caused, thereby leading to poor cycle performance and capacity decay of the lithium-selenium battery.

[0027] In order to solve the technical problems of poor cycle performance and capacity decay of the lithium-selenium battery, the embodiments of the present application provide an electrode material, which comprises a Ti3C2Tx matrix and elemental selenium on the surface of the Ti3C2Tx matrix.

[0028] Specifically, in the present embodiment, the elemental selenium on the surface of the Ti3C2Tx matrix in the electrode material is bound by Ti-O bonds, and when the electrode material is used to prepare a lithium-selenium battery, in the cycling process of the lithium-selenium battery, both lithiation and delithiation of selenium are carried out on the surface of the Ti3C2Tx matrix, and the functional groups such as hydroxyl and carboxyl groups on the surface of the Ti3C2Tx matrix can also capture free selenium, so that the occurrence of shuttle effect can be effectively reduced, and at the same time, the stacking between the Ti3C2Tx layers in the Ti3C2Tx matrix also forms a certain barrier effect to hinder the shuttle of selenium, so that the capacity attenuation problem is improved, and to some extent, the capacity of the prepared lithium-selenium battery can be maintained.

[0029] Preferably, the particle size of the Ti3C2Tx matrix is 0-5 um.

[0030] Further, as shown in the present embodiment, a preparation method of an electrode material is provided, comprising the steps of: Figure 1

[0031] S10, mixing selenium powder and an oxidizing agent to prepare a selenous acid solution;

[0032] S20, mixing a Ti3C2Tx matrix, a cationic surfactant and water to prepare a Ti3C2Tx matrix solution;

[0033] S30, mixing the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare an electrode material.

[0034] In the present embodiment, first, by mixing selenium powder and an oxidizing agent, the purity of the selenium powder is greater than 99.9%, a selenous acid (H2SeO3) solution is prepared, and then a Ti3C2Tx matrix, a cationic surfactant and water are mixed, and after stirring and dispersing, a Ti3C2Tx matrix solution is obtained, since the cationic surfactant is added in the Ti3C2Tx matrix solution, the surface of the Ti3C2Tx matrix in the Ti3C2Tx matrix solution is positively charged, when the selenous acid solution is mixed with the Ti3C2Tx matrix solution to prepare a composite solution, in the composite solution, the negatively charged SeO3 2- is attracted to the positively charged Ti3C2Tx matrix, so that the negatively charged SeO3 2- is distributed on the surface of the positively charged Ti3C2Tx matrix, and when a reducing agent is continuously added, the reducing agent can reduce SeO3 2- to elemental selenium, that is, the electrode material is obtained.

[0035] ​The stirring speed for mixing the Ti3C2Tx matrix, the cationic surfactant and water in step S20 is 500-1000 rpm, and the stirring time is 0.5-1 h.

[0036] In this embodiment, the stirring speed can be 600 rpm, 700 rpm, 800 rpm or 900 rpm, etc., and the stirring time can be 0.6 h, 0.7 h, 0.8 h or 0.9 h, etc.

[0037] Further, step S30, the mixing of the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare an electrode material, comprises:

[0038] S301, mixing the selenous acid solution and the Ti3C2Tx matrix solution to obtain a composite solution;

[0039] S302, adding a reducing agent to the composite solution to prepare an electrode material.

[0040] In this embodiment, in step S301, by first mixing the selenous acid solution and the Ti3C2Tx matrix solution, the negatively charged SeO3 2- in the composite solution can fully attract the positively charged Ti3C2Tx matrix on the surface, so that the negatively charged SeO3 2- is uniformly distributed on the surface of the positively charged Ti3C2Tx matrix. Then, in step S302, a reducing agent is added to the composite solution, and the SeO3 2- uniformly distributed on the surface of the positively charged Ti3C2Tx matrix is reduced to elemental selenium, and the prepared elemental selenium is anchored to the surface of the positively charged Ti3C2Tx matrix by the formed chemical bond, thereby obtaining the electrode material.

[0041] In step S301, the stirring speed for mixing the selenous acid solution and the Ti3C2Tx matrix solution is 500-1000 rpm, and the stirring time is 0.5-1 h.

[0042] In this embodiment, the stirring speed can be 600 rpm, 700 rpm, 800 rpm or 900 rpm, etc., and the stirring time can be 0.6 h, 0.7 h, 0.8 h or 0.9 h, etc.

[0043] Preferably, in the present embodiment, after the addition of the reducing agent to the composite material completes the redox reaction, the mixed solution containing the electrode material after the reaction is first subjected to centrifugal treatment to obtain the electrode material, wherein the centrifugal speed is 500-1500 rpm, and then the electrode material is subjected to drying treatment at 50-80°C to remove the solvent attached to the surface of the electrode material.

[0044] In one embodiment, the ratio of the Ti3C2Tx matrix, the surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150 by mass fraction.

[0045] In one embodiment, the ratio of the Ti3C2Tx matrix, the surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150 by mass fraction.

[0046] In one embodiment, the ratio of the Ti3C2Tx matrix, the surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150 by mass fraction.

[0047] In one embodiment, the ratio of the Ti3C2Tx matrix, the surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150 by mass fraction.

[0048] In the embodiment, the hydrogen peroxide with a mass fraction of 30% is used as the oxidant, and after the redox reaction between the hydrogen peroxide and the selenium powder, the selenite solution is prepared, and water is another reaction product, so that the selenite solution prepared by using the hydrogen peroxide as the oxidant does not need to be purified, the process flow is simplified, the hydrogen peroxide is simple and easy to obtain, and the cost is low, which is beneficial to mass production in industry.

[0049] In a specific embodiment, the reducing agent is glucose or ascorbic acid.

[0050] In the embodiment, the glucose or ascorbic acid is used as the reducing agent, and after the redox reaction between the glucose or ascorbic acid and the SeO3 2- After the redox reaction, elemental selenium is generated in situ on the surface of the Ti3C2Tx matrix.

[0051] In a specific embodiment, the cationic surfactant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, hexadecyl dimethyl ethyl ammonium bromide, and hexadecyltrimethylammonium chloride.

[0052] In addition, the embodiment of the present application further provides a lithium ion battery comprising the electrode material or the electrode material prepared by using the preparation method of the electrode material.

[0053] The present application will be further described in detail below with reference to specific embodiments.

[0054] Embodiment 1

[0055] 0.5 g of selenium powder and 1.5 mL of hydrogen peroxide with a mass fraction of 30% are mixed to prepare a selenite solution, 8 mL of distilled water is added for dilution to obtain a diluted selenite solution, 1 g of Ti3C2Tx nanosheet and 0.01 g of CTAB are mixed with 50 mL of distilled water, and under the condition that the stirring speed is 600 rpm, the mixture is stirred for 0.6 h to obtain a Ti3C2Tx matrix solution with a positively charged surface, then the selenite solution is added to the Ti3C2Tx matrix solution for mixing, and under the condition that the stirring speed is 600 rpm, the mixture is stirred for 0.6 h to obtain a SeO3 2- / TiO2 / Ti3C2Tx composite solution, finally, 2 g of glucose is added to the composite solution to reduce the selenite to elemental selenium, after the reaction is completed, centrifugal and drying treatments are performed, the centrifugal speed is 800 rpm, and the drying temperature is 60°C, to prepare an electrode material 1.

[0056] Embodiment 2

[0057] A selenite solution was prepared by mixing 1.0 g of selenium powder and 2.8 mL of 30% mass fraction hydrogen peroxide, and diluting with 8 mL of distilled water. A positively charged Ti3C2Tx matrix solution was prepared by mixing 1.5 g of Ti3C2Tx nanosheets and 0.012 g of CTAB with 80 mL of distilled water, stirring at 600 rpm for 0.6 h. The selenite solution was then added to the Ti3C2Tx matrix solution and stirred at 600 rpm for 0.6 h to obtain a SeO3 2- / TiO2 / Ti3C2Tx composite solution. Finally, 4.5 g of glucose was added to the composite solution to reduce the selenite to elemental selenium. After the reaction was complete, centrifugation and drying were performed at a centrifugation speed of 800 rpm and a drying temperature of 60°C to obtain electrode material 2.

[0058] Example 3

[0059] A selenite solution was prepared by mixing 1.2 g of selenium powder and 3.4 mL of 30% mass fraction hydrogen peroxide, and diluting with 10 mL of distilled water. A positively charged Ti3C2Tx matrix solution was prepared by mixing 1.5 g of Ti3C2Tx nanosheets and 0.013 g of CTAB with 80 mL of distilled water, stirring at 600 rpm for 0.6 h. The selenite solution was then added to the Ti3C2Tx matrix solution and stirred at 600 rpm for 0.6 h to obtain a SeO3 2- / TiO2 / Ti3C2Tx composite solution. Finally, 5 g of glucose was added to the composite solution to reduce the selenite to elemental selenium. After the reaction was complete, centrifugation and drying were performed at a centrifugation speed of 800 rpm and a drying temperature of 60°C to obtain electrode material 3.

[0060] Example 4

[0061] A selenite solution was prepared by mixing 1.5 g of selenium powder and 4.5 mL of 30% mass fraction hydrogen peroxide, and diluting with 10 mL of distilled water. A positively charged Ti3C2Tx matrix solution was prepared by mixing 1.5 g of Ti3C2Tx nanosheets and 0.012 g of CTAB with 50 mL of distilled water, stirring at 600 rpm for 0.6 h. The selenite solution was then added to the Ti3C2Tx matrix solution and stirred at 600 rpm for 0.6 h to obtain a SeO3 2-The / TiO2 / Ti3C2Tx composite solution was prepared by adding 6g of glucose to the composite solution to reduce selenite to elemental selenium. After the reaction was completed, the solution was centrifuged and dried at 800 rpm and 60℃ to obtain electrode material 4.

[0062] Example 5

[0063] 2g of selenium powder and 6mL of 30% hydrogen peroxide were mixed to prepare a selenite solution, which was then diluted with 12mL of distilled water to obtain a diluted selenite solution. 1.5g of Ti3C2Tx nanosheets and 0.012g of CTAB were mixed with 50mL of distilled water and stirred at 600rpm for 0.6h to obtain a positively charged Ti3C2Tx matrix solution. Subsequently, the selenite solution was added to the Ti3C2Tx matrix solution and mixed, stirring at 600rpm for 0.6h to obtain SeO3. 2- The / TiO2 / Ti3C2Tx composite solution was prepared by adding 8g of glucose to the composite solution to reduce selenite to elemental selenium. After the reaction was completed, the solution was centrifuged and dried at 800 rpm and 60℃ to obtain electrode material 5.

[0064] Comparative Example 1

[0065] Mix 2g of selenium powder with 2g of Ti3C2Tx matrix material evenly to obtain electrode material 6.

[0066] Furthermore, the cycle performance of the electrode materials prepared in Examples 1 to 5 and the electrode materials prepared in the comparative examples was tested in this invention. The testing methods are as follows:

[0067] 1) Using N-methylpyrrolidone (NMP) as solvent, the electrode materials were prepared in a ratio of 7:2:1: electrode black: polyvinylidene fluoride (PVDF) to obtain the corresponding electrode sheet.

[0068] 2) In a glove box filled with high-purity argon, lithium metal was used as the negative electrode and the prepared electrode sheet was used as the positive electrode to assemble CR2025 button cells.

[0069] 3) Cyclic performance test was performed on a charge-discharge tester. The test conditions were: test temperature 25±2℃, test voltage 1.0-3.0V, and current density 0.5C (1C=675mAh / g).

[0070] from Figure 2As can be seen from the data in the table, the lithium selenium batteries prepared by using the electrode materials prepared in Examples 1 to 5 have better cycle performance than the lithium selenium battery prepared by using the electrode material prepared in Comparative Example 1, and the capacity of the battery can still be maintained at a high level after multiple cycles. For example, the cycle curve of the lithium selenium battery prepared by using the electrode material prepared in Example 2, the specific capacity of the prepared lithium selenium battery decreases from 600 mAh / g to 500 mAh / g after 150 cycles, while the specific capacity of the lithium selenium battery prepared by using the electrode material prepared in Comparative Example 1 decreases from 600 mAh / g to less than 100 mAh / g after 150 cycles.

[0071] Therefore, in the present embodiment, elemental selenium is generated in situ on the surface of the Ti3C2Tx matrix, and the elemental selenium on the surface of the Ti3C2Tx matrix is bound by Ti-O bonds. When the electrode material is used to prepare a lithium selenium battery, during the cycle process of the lithium selenium battery, lithiumation and delithiation of selenium are both carried out on the surface of the Ti3C2Tx matrix, and the functional groups such as hydroxyl and carboxyl groups on the surface of the Ti3C2Tx matrix can also capture free selenium, thereby effectively reducing the occurrence of shuttle effect. Further, the stacking between the Ti3C2Tx layers in the Ti3C2Tx matrix also forms a certain barrier effect to hinder the shuttle of selenium, thereby improving the capacity decay problem, and to some extent, the capacity of the prepared lithium selenium battery can be maintained.

[0072] The above describes the embodiments of the present application in detail, and the principles and implementation modes of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description should not be understood as a limitation of the present application.

Claims

1. A lithium-selenium battery, characterized by The electrode material comprises a Ti3C2Tx matrix and elemental selenium on the surface of the Ti3C2Tx matrix. The preparation method of the electrode material comprises the steps of: mixing selenium powder and an oxidizing agent to prepare a selenous acid solution; mixing a Ti3C2Tx matrix, a cationic surfactant and water to prepare a Ti3C2Tx matrix solution; mixing the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare the electrode material.

2. The lithium-selenium battery of claim 1, wherein, The particle size of the Ti3C2Tx matrix is 0-5 um.

3. The lithium-selenium battery of claim 1, wherein, The step of mixing the selenous acid solution, the Ti3C2Tx matrix solution and a reducing agent to prepare the electrode material comprises: mixing the selenous acid solution and the Ti3C2Tx matrix solution to obtain a composite solution; adding a reducing agent to the composite solution to prepare the electrode material.

4. The lithium-selenium battery according to claim 1 or 3, c h a r a c t e r i z e d in that The mass ratio of the Ti3C2Tx matrix, the cationic surfactant, the oxidizing agent, the selenium powder, the reducing agent and water is 1-10:0.1-1:1-15:1-10:1-10:80-150.

5. The lithium-selenium battery according to claim 1 or 3, c h a r a c t e r i z e d in that, The oxidizing agent is hydrogen peroxide with a mass fraction of 30%-50%.

6. The lithium-selenium battery according to claim 1 or 3, c h a r a c t e r i z e d in that, The reducing agent is glucose or ascorbic acid.

7. The lithium-selenium battery according to claim 1 or 3, c h a r a c t e r i z e d in that, The cationic surfactant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, hexadecyl dimethyl ethyl bromide and hexadecyl trimethyl ammonium chloride.

8. The lithium-selenium battery according to claim 1 or 3, c h a r a c t e r i z e d in that, The purity of the selenium powder is greater than 99.9%.

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