Preparation method of negative plate, negative plate and sodium ion battery

Abstract

The invention discloses a preparation method of a negative electrode plate, the negative electrode plate and a sodium-ion battery, and the negative electrode plate of the sodium-ion battery comprises a negative electrode current collector; the phosphorus-carbon negative electrode coatings are arranged on the two sides of the negative electrode current collector in the thickness direction of the negative electrode current collector; and the titanium dioxide coating is arranged on one side, far away from the negative electrode current collector, of the phosphorus-carbon negative electrode coating. According to the embodiment of the invention, the titanium dioxide coating is arranged on the phosphorus-carbon negative electrode coating of the sodium-ion battery negative electrode plate, the titanium dioxide coating can be applied to the phosphorus-carbon negative electrode coating with high phosphorus content, and the titanium dioxide coating can improve the overall potential of the negative electrode, avoid the sodium precipitation phenomenon in the battery cell circulating process, prevent the battery cell from being degraded and improve the battery cell circulating performance.

Description

Technical Field

[0001] This application relates to the field of negative electrode material technology, and more specifically, to a method for preparing a negative electrode sheet, the negative electrode sheet, and a sodium-ion battery. Background Technology

[0002] Currently, there is a significant energy density gap between sodium-ion batteries and lithium-ion batteries. Phosphorus-carbon materials, compared to traditional hard carbon materials used in sodium-ion batteries, have a higher energy density and can effectively improve the energy density of sodium-ion batteries when used as the anode. However, compared to hard carbon 10... 3 ~10 2 S·m 1 The conductivity of red phosphorus is only 10. 12 S·m 1 Therefore, the kinetic performance of phosphorus-carbon anodes with high phosphorus content decreases, and sodium is more easily deposited, leading to a decline in cycle capacity retention. Summary of the Invention

[0003] One objective of this application is to provide a method for preparing a sodium-ion battery negative electrode sheet, which can solve at least one of the technical problems existing in the prior art when using phosphorus-carbon materials, such as decreased kinetic performance of phosphorus-carbon negative electrodes, easier sodium precipitation, and resulting in decay of cycle capacity retention rate.

[0004] Another object of this application is to provide a sodium-ion battery negative electrode sheet, including a sodium-ion battery negative electrode sheet prepared by the above-described method for preparing a sodium-ion battery negative electrode sheet.

[0005] Another object of this application is to provide a sodium-ion battery, including the above-described sodium-ion battery negative electrode sheet.

[0006] To achieve the above objectives, this application provides the following technical solutions.

[0007] A sodium-ion battery negative electrode sheet according to a first aspect of this application includes: a negative electrode current collector; a phosphorus-carbon negative electrode coating disposed on both sides of the negative electrode current collector in its thickness direction; and a titanium dioxide coating disposed on the side of the phosphorus-carbon negative electrode coating away from the negative electrode current collector.

[0008] Optionally, the weight ratio of phosphorus to carbon in the phosphorus-carbon anode coating is (10-15):(85-90).

[0009] Optionally, the thickness of the titanium dioxide coating is 3µm-5µm.

[0010] The method for preparing a sodium-ion battery negative electrode sheet according to the second aspect of this application includes the following steps: preparing a phosphorus-carbon negative electrode slurry using a phosphorus-carbon negative electrode material, a first conductive agent, and a first binder; coating the phosphorus-carbon negative electrode slurry onto a negative electrode current collector to obtain a phosphorus-carbon negative electrode sheet; preparing a titanium dioxide slurry using a titanium dioxide material, a second conductive agent, and a second binder; coating the titanium dioxide slurry onto the surface of the phosphorus-carbon negative electrode sheet, and drying it to obtain the negative electrode sheet.

[0011] Optionally, the step of preparing the phosphorus-carbon anode slurry includes: mixing the first conductive agent and the first binder in deionized water in a certain proportion, and stirring under vacuum at room temperature to obtain a first conductive adhesive solution; adding the phosphorus-carbon anode material to the first conductive adhesive solution, and stirring under vacuum at room temperature to obtain the phosphorus-carbon anode slurry.

[0012] Optionally, the step of preparing the titanium dioxide slurry includes: mixing the second conductive agent and the second binder in deionized water in a certain proportion, and stirring under vacuum at room temperature to obtain a second conductive adhesive solution; adding the titanium dioxide material to the second conductive adhesive solution, and stirring under vacuum at room temperature to obtain a titanium dioxide slurry.

[0013] Optionally, the first conductive agent and / or the second conductive agent is SWCNT or a mixture of SWCNT and SP.

[0014] Optionally, the first adhesive and / or the second adhesive are PAA or SA.

[0015] Optionally, after coating the titanium dioxide slurry onto the surface of the phosphorus-carbon negative electrode sheet, the electrode sheet is vacuum baked in a vacuum oven with inert gas circulation protection, and then cooled to room temperature to obtain the negative electrode sheet.

[0016] The sodium-ion battery according to the third aspect of this application includes any of the sodium-ion battery negative electrode sheets described above, or a sodium-ion battery negative electrode sheet prepared by any of the methods described above.

[0017] According to the embodiments of this application, the phosphorus-carbon negative electrode coating of the sodium-ion battery is provided with a titanium dioxide coating. The titanium dioxide coating can be applied to phosphorus-carbon negative electrode coatings with high phosphorus content. The titanium dioxide coating can improve the overall potential of the negative electrode, avoid sodium precipitation during cell cycling, prevent cell degradation, and improve cell cycling performance.

[0018] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0020] Figure 1 This is a schematic diagram of the structure of a sodium-ion battery negative electrode sheet according to an embodiment of this application.

[0021] Attached icon number Sodium-ion battery negative electrode 100; Negative electrode current collector 10; Phosphorus-carbon anode coating 20; Titanium dioxide coating 30. Detailed Implementation

[0022] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0023] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0025] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0027] The sodium-ion battery negative electrode 100 according to an embodiment of this application is described in detail below with reference to the accompanying drawings.

[0028] like Figure 1 As shown, the sodium-ion battery negative electrode 100 according to an embodiment of this application includes: a negative electrode current collector 10, a phosphorus-carbon negative electrode coating 20, and a titanium dioxide coating 30.

[0029] Specifically, the phosphorus-carbon negative electrode coating 20 is disposed on both sides of the negative electrode current collector 10 in its thickness direction, and the titanium dioxide coating 30 is disposed on the side of the phosphorus-carbon negative electrode coating 20 away from the negative electrode current collector 10.

[0030] In other words, the sodium-ion battery negative electrode 100 according to the embodiments of this application combines a negative electrode current collector 10, a phosphorus-carbon negative electrode coating 20, and a titanium dioxide coating 30. The phosphorus-carbon negative electrode coating 20 is located on both sides of the negative electrode current collector 10, and the titanium dioxide coating 30 is located on the outer side of the phosphorus-carbon negative electrode coating 20. For example, the negative electrode current collector 10 extends horizontally, and its thickness direction is vertical. The phosphorus-carbon negative electrode coating 20 is provided above and below the negative electrode current collector 10, and the phosphorus-carbon negative electrode coating 20 extends horizontally. The titanium dioxide coating 30 is provided above the phosphorus-carbon negative electrode coating 20 above the negative electrode current collector 10, and below the phosphorus-carbon negative electrode coating 20 below the negative electrode current collector 10, and the titanium dioxide coating 30 extends horizontally.

[0031] Understandably, compared to Hard Carbon 10 3 ~10 2 S·m 1 The conductivity of red phosphorus is only 10. 12 S·m 1 Therefore, the kinetic performance of phosphorus-carbon anodes with high phosphorus content decreases, making them more prone to sodium deposition. Titanium dioxide materials, on the other hand, have an average sodium storage potential of around 0.9V and good rate performance. Therefore, adding a 30% titanium dioxide coating increases the overall anode potential, moving it further away from the sodium deposition potential. + / Na transition potential, avoid sodium deposition, prevent cell degradation, and improve cell cycle performance.

[0032] Therefore, according to the embodiments of this application, the phosphorus-carbon negative electrode coating 20 of the sodium-ion battery negative electrode sheet 100 is provided with a titanium dioxide coating 30. The titanium dioxide coating 30 can be applied to the phosphorus-carbon negative electrode coating 20 with high phosphorus content. The titanium dioxide coating 30 can improve the overall potential of the negative electrode, avoid sodium precipitation during the cell cycle, prevent cell degradation, and improve the cell cycle performance.

[0033] According to one embodiment of this application, the weight ratio of phosphorus to carbon in the phosphorus-carbon negative electrode coating 20 is (10-15):(85-90). By adopting the above ratio, the specific capacity of the negative electrode can be significantly improved, thereby increasing the energy density of the battery cell.

[0034] In some specific embodiments of this application, the thickness of the titanium dioxide coating 30 is not less than 3 μm and not more than 5 μm, for example, the thickness of the titanium dioxide coating 30 is 3 μm, 3.1 μm, 3.3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, etc. That is to say, a titanium dioxide coating 30 thickness of 3 μm-5 μm is beneficial for achieving complete coverage of the phosphorus-carbon anode coating 20 with titanium dioxide. Titanium dioxide is a zero-strain material with a more stable chemical structure and fewer interfacial side reactions with the electrolyte, which can protect the phosphorus-carbon anode coating 20. Moreover, after the titanium dioxide coating 30 is applied, the overall potential of the anode is increased, moving away from Na+. + / Na transition potential, avoiding sodium precipitation; in addition, it can also prevent the titanium dioxide coating 30 from being too thick.

[0035] This application also discloses a method for preparing the sodium-ion battery negative electrode 100 of any of the above embodiments, including the following steps: Phosphorus-carbon anode slurry is prepared by using phosphorus-carbon anode material, a first conductive agent, and a first binder. Phosphorus-carbon negative electrode slurry is coated onto negative electrode current collector 10 to obtain phosphorus-carbon negative electrode sheet; Titanium dioxide slurry was prepared by using titanium dioxide material, a second conductive agent, and a second binder. Titanium dioxide slurry is coated onto the surface of a phosphorus-carbon negative electrode sheet, and the negative electrode sheet is obtained after drying.

[0036] In this embodiment, a phosphorus-carbon negative electrode slurry is first prepared, then coated onto the negative electrode current collector 10 to obtain a phosphorus-carbon negative electrode sheet. Next, a titanium dioxide slurry is coated onto the surface of the phosphorus-carbon negative electrode sheet to prepare the negative electrode sheet. By employing the above steps, not only can the phosphorus-carbon negative electrode coating 20 and the titanium dioxide coating 30 be prepared in a simple manner, but the thickness of the titanium dioxide coating 30 can also be easily controlled.

[0037] According to one embodiment of this application, the steps for preparing the phosphorus-carbon anode slurry include: The first conductive agent and the first binder are mixed in deionized water in a certain proportion, and the mixture is stirred under vacuum at room temperature to obtain the first conductive adhesive solution. Phosphorus-carbon anode material was added to the first conductive adhesive solution, and phosphorus-carbon anode slurry was obtained under vacuum stirring at room temperature.

[0038] In this embodiment, the phosphorus-carbon anode slurry prepared by the above steps has the advantages of uniform mixing and slurry stability.

[0039] In some specific embodiments of this application, the steps for preparing the titanium dioxide slurry include: The second conductive agent and the second binder are mixed in deionized water in a certain proportion, and the mixture is stirred under vacuum at room temperature to obtain the second conductive adhesive solution. Titanium dioxide material was added to the second conductive adhesive solution, and titanium dioxide slurry was obtained under vacuum stirring at room temperature.

[0040] In this embodiment, the titanium dioxide slurry prepared by the above steps has the advantages of uniform mixing and slurry stability.

[0041] According to one embodiment of this application, the first conductive agent and / or the second conductive agent is SWCNT, or a mixture of SWCNT and SP, for example, the total overall proportion of the conductive agent is 3.5. By using SWCNT as the conductive agent, SWCNT is a linear conductive agent that can form chemical bonds with phosphorus carbon materials, thereby slowing down the capacity decay of the negative electrode.

[0042] In some specific embodiments of this application, the first adhesive and / or the second adhesive are PAA and SA, for example, in a ratio of 2:1.5. By using PAA and SA as adhesives, PAA and SA will undergo an adhesive reaction, which improves the adhesion of the coating and prevents material from falling off.

[0043] According to one embodiment of this application, after coating a titanium dioxide slurry onto the surface of a phosphorus-carbon negative electrode sheet, the electrode sheet is vacuum-baked in a vacuum oven under inert gas circulation protection. After baking, it is cooled to room temperature to obtain the negative electrode sheet. The negative electrode sheet prepared using the above steps has an average sodium storage potential of approximately 0.9V for the titanium dioxide material and exhibits good rate performance. Therefore, increasing the titanium dioxide coating by 30° increases the overall potential of the negative electrode, moving it further away from the sodium storage potential. + The / Na transition potential has the advantage of avoiding sodium precipitation.

[0044] This application also discloses a sodium-ion battery according to any of the above embodiments, including the sodium-ion battery negative electrode 100 of any of the above embodiments, or a sodium-ion battery negative electrode 100 prepared by the preparation method of the sodium-ion battery negative electrode 100 of any of the above embodiments. The sodium-ion battery negative electrode 100 of the embodiments of this application has a titanium dioxide coating 30 on its phosphorus-carbon negative electrode coating 20, which has the advantage of improved cell cycle performance.

[0045] The sodium-ion battery of this application embodiment will be described in detail below with reference to specific implementation methods.

[0046] Example 1 Step 1: Prepare phosphorus-carbon anode material, a first conductive agent, and a first binder as raw materials. The effective component ratio of the phosphorus-carbon anode material, the first conductive agent, and the first binder is 93:3.5:3.5. The weight ratio of phosphorus to carbon in the phosphorus-carbon anode material is 10:90. The first conductive agent is SWCNT, and the first binder is PAA or SA, with a ratio of 2:1.5.

[0047] Step 2: Mix the first conductive agent and the first binder evenly in deionized water according to the ratio set in Step 1, and stir under vacuum for 1 hour at room temperature to obtain a uniform first conductive adhesive solution; add the phosphorus-carbon negative electrode material set in Step 1 to the first conductive adhesive solution, and stir under vacuum for 1 hour at room temperature to obtain a phosphorus-carbon negative electrode slurry; coat the phosphorus-carbon negative electrode slurry onto the negative electrode current collector to obtain a phosphorus-carbon negative electrode sheet.

[0048] Step 3: Prepare titanium dioxide material, a second conductive agent, and a second binder as raw materials. The effective component ratio of the titanium dioxide material, the second conductive agent, and the second binder is 93:3.5:3.5. The titanium dioxide material is a nano-sized powder, the second conductive agent is SWCNT, and the second binder is PAA or SA, with a ratio of 2:1.5.

[0049] Step 4: Mix the second conductive agent and the second binder evenly in deionized water according to the ratio in Step 3, and stir under vacuum for 1 hour at room temperature to obtain a uniform second conductive adhesive solution; add the titanium dioxide material set in Step 3 to the second conductive adhesive solution, and stir under vacuum for 1 hour at room temperature to obtain a titanium dioxide slurry; coat the titanium dioxide slurry onto the phosphorus-carbon negative electrode sheet, and the thickness of the titanium dioxide coating 30 is 5 μm; after coating, the electrode sheet is vacuum baked at 150°C for 2 hours in a vacuum oven under inert gas circulation protection, cooled to room temperature, and the sodium-ion battery negative electrode sheet 100 is taken out to continue the operation.

[0050] Step 5: Assemble the sodium-ion battery negative electrode 100 into a cell and conduct a 1C cycle test in an environment of 25°C with a voltage window of 2.0V to 4.0V.

[0051] Example 2 The only difference between Example 2 and Example 1 is that the weight ratio of phosphorus to carbon in the phosphorus-carbon anode material is 15:85.

[0052] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no titanium dioxide coating is applied, and there is no titanium dioxide coating 30.

[0053] The negative electrode sheets of the above embodiments and comparative examples were assembled into sodium-ion batteries. After cycling under the same cycling conditions, the batteries were tested, and the test results are shown in Table 1.

[0054] Table 1 As shown in Table 1, under the same cycling conditions, after 100 cycles, no sodium was deposited at the disassembly interface in Examples 1 and 2, and the capacity retention rate after 1000 cycles met the requirement of ≥80%. However, in Comparative Example 1, sporadic spot sodium deposition appeared at the negative electrode interface, and the capacity retention rate after 1000 cycles was only 69.3%. This is because, compared to hard carbon 10... 3 ~10 2 S·m 1 The conductivity of red phosphorus is only 10. 12 S·m 1 Therefore, the kinetic performance of phosphorus-carbon anodes with high phosphorus content decreases, making them more prone to sodium deposition. Titanium dioxide materials, on the other hand, have an average sodium storage potential of around 0.9V and good rate performance. Therefore, adding a 30% titanium dioxide coating increases the overall anode potential, moving it further away from the sodium deposition potential. + / Na transition potential, avoid sodium deposition, prevent cell degradation, and improve cell cycle performance.

[0055] In summary, the sodium-ion battery negative electrode sheet 100 according to the embodiments of this application has a titanium dioxide coating 30 on the phosphorus-carbon negative electrode coating 20. The titanium dioxide coating 30 can be applied to the phosphorus-carbon negative electrode coating 20 with high phosphorus content. The titanium dioxide coating 30 can improve the overall potential of the negative electrode, avoid sodium precipitation during cell cycling, prevent cell degradation, and improve cell cycling performance.

[0056] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A sodium-ion battery negative electrode sheet, characterized in that, include: Negative electrode current collector; A phosphorus-carbon negative electrode coating, wherein the phosphorus-carbon negative electrode coating is disposed on both sides of the negative electrode current collector in its thickness direction; The titanium dioxide coating is disposed on the side of the phosphorus-carbon anode coating away from the anode current collector.

2. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The weight ratio of phosphorus to carbon in the phosphorus-carbon anode coating is (10-15):(85-90).

3. The sodium-ion battery negative electrode sheet according to claim 2, characterized in that, The thickness of the titanium dioxide coating is 3µm-5µm.

4. A method for preparing a sodium-ion battery negative electrode sheet according to any one of claims 1-3, characterized in that, Includes the following steps: Phosphorus-carbon anode slurry is prepared by using phosphorus-carbon anode material, a first conductive agent, and a first binder. The phosphorus-carbon negative electrode slurry is coated onto the negative electrode current collector to obtain a phosphorus-carbon negative electrode sheet; Titanium dioxide slurry was prepared by using titanium dioxide material, a second conductive agent, and a second binder. The titanium dioxide slurry is coated onto the surface of the phosphorus-carbon negative electrode sheet, and the negative electrode sheet is obtained after drying.

5. The method for preparing the sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The steps for preparing the phosphorus-carbon anode slurry include: The first conductive agent and the first adhesive are mixed in deionized water in a certain proportion, and the mixture is stirred under vacuum at room temperature to obtain the first conductive adhesive solution. The phosphorus-carbon anode material is added to the first conductive adhesive solution, and the phosphorus-carbon anode slurry is obtained under vacuum stirring at room temperature.

6. The method for preparing the sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The steps for preparing the titanium dioxide slurry include: The second conductive agent and the second binder are mixed in deionized water in a certain proportion, and the mixture is stirred under vacuum at room temperature to obtain the second conductive adhesive solution. The titanium dioxide material was added to the second conductive adhesive solution, and a titanium dioxide slurry was obtained under vacuum stirring at room temperature.

7. The method for preparing a sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The first conductive agent and / or the second conductive agent is SWCNT or a mixture of SWCNT and SP.

8. The method for preparing a sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The first adhesive and / or the second adhesive are PAA and SA.

9. The method for preparing a sodium-ion battery negative electrode sheet according to claim 4, characterized in that, After the titanium dioxide slurry is coated on the surface of the phosphorus-carbon negative electrode sheet, the electrode sheet is vacuum baked in a vacuum oven with inert gas circulation protection, and then cooled to room temperature to obtain the negative electrode sheet.

10. A sodium-ion battery, characterized in that, The sodium-ion battery negative electrode sheet includes any one of the sodium-ion battery negative electrode sheets according to claims 1-3, or sodium-ion battery negative electrode sheets prepared by any one of the sodium-ion battery negative electrode sheets according to claims 4-9.

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