Organic matter-doped phosphorus-coated current collector, preparation method thereof and sodium ion battery

Abstract

The invention belongs to the technical field of sodium ion batteries, and particularly relates to an organic matter doped phosphorus-coated current collector, a preparation method thereof and a sodium ion battery, the organic matter doped phosphorus-coated current collector and an electrode coating coated on the surface of the current collector form an electrode pole piece, and the electrode coating is coated on the surface of the current collector with the loading capacity of 0.6-1.2 mg / cm < 2 >; wherein the electrode coating is made of a mixture of simple substance phosphorus powder and an organic matter, and in the mixture of the simple substance phosphorus powder and the organic matter, the mass ratio of the organic matter is 5%-40%. The sodium-ion battery prepared by using the sodium-ion battery electrode plate provided by the invention can realize high reversible specific capacity and high capacity retention rate, the loading capacity of an electrode coating is controlled to be 0.6-1.2 mg / cm < 2 >, the ineffective mass of a negative electrode is greatly reduced while sufficient sodium ion deposition active sites are ensured, and the energy density of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to an organic-mixed phosphorus-coated current collector and its preparation method, and a sodium-ion battery. Background Technology

[0002] With the continuous development of energy storage materials such as batteries, the shortcomings of lithium batteries are becoming increasingly apparent. Due to the finite nature of lithium resources, from a cost perspective, the reserves of lithium resources are insufficient to support lithium-ion batteries in meeting the demands of modern society for large-scale energy storage systems. The continued growth in energy demand will inevitably lead to a continuous rise in lithium prices. Therefore, sodium-ion batteries, which emerged around the same time as lithium-ion batteries, have once again come into the public eye. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries; they are also rocking chair batteries. Ions store and release charge through an intercalation / deintercalation mechanism. The working principle is as follows: during charging, sodium ions are extracted from the positive electrode and intercalated into the negative electrode through the electrolyte; during discharging, the opposite occurs, with sodium ions being extracted from the negative electrode and intercalated into the positive electrode through the electrolyte. However, the low specific capacity and large volume expansion of traditional sodium-ion battery negative electrode materials limit their further development. Finding new sodium-ion battery negative electrode systems has become a problem that needs to be solved.

[0003] In recent years, self-generated negative electrode technology has received widespread attention. However, in lithium-ion batteries, self-generated negative electrode technology is prone to the formation of lithium dendrites, which pose a risk of short circuit due to puncture of the separator. Sodium-ion batteries are suitable for the application of self-generated negative electrode technology due to their safety and dendrite-free advantages, but existing technologies have problems such as low initial efficiency and poor cycle stability. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the present invention provides a sodium-ion battery electrode sheet, wherein the electrode sheet includes a current collector and an electrode coating coated on the surface of the current collector, wherein the electrode coating has a flux concentration of 0.6-1.2 mg / cm³. 2 The loading amount is coated on the surface of the current collector; wherein, the electrode coating is made of a mixture of elemental phosphorus powder and organic matter, wherein the mass percentage of organic matter in the mixture of elemental phosphorus powder and organic matter is 5%-40%.

[0005] In some embodiments, the electrode coating is at a concentration of 0.7-1.0 mg / cm³. 2 The electrode coating is applied to the surface of the current collector at a loading rate of 0.8 mg / cm²; in some embodiments, the electrode coating is applied at a loading rate of 0.8 mg / cm². 2 The loading amount is coated on the surface of the current collector.

[0006] In some embodiments, the current collector is a metal foil; in other embodiments, the metal foil is a copper foil or an aluminum foil.

[0007] In some implementations, the organic matter accounts for 10%-20% of the mass of the mixture of elemental phosphorus powder and organic matter.

[0008] In some embodiments, the elemental phosphorus powder is at least one of black phosphorus or red phosphorus.

[0009] In some embodiments, the organic compound is a carbohydrate compound; in some embodiments, the carbohydrate compound is at least one of a monosaccharide, a disaccharide, or a polysaccharide; in some embodiments, the monosaccharide is glucose or fructose, the disaccharide is sucrose or maltose, and the polysaccharide is starch, cellulose, or chitosan.

[0010] The organic compounds described in this invention can also be any organic compounds rich in electron-rich functional groups such as hydroxyl and carboxyl groups, which can enhance adhesion and buffer the volume stress generated during the insertion and extraction of sodium ions, such as hydroxyl-containing polymers (e.g., polyvinyl alcohol).

[0011] The organic compounds mentioned above serve to connect the active material and the current collector, exhibiting higher adhesion and cohesion. The phosphorus powder provides more active sites for sodium ion deposition, lowering the sodium ion deposition barrier. Low loading or a thin coating is used because sodium ions do not need to be embedded in the active material; they only need to be deposited on the electrode film surface, thus reducing the mass of the battery's negative electrode.

[0012] On one hand, the present invention provides a method for preparing the aforementioned electrode sheet, comprising the following steps: (1) After ball milling and mixing the mixture of elemental phosphorus powder and organic matter, the electrode active material is obtained by washing with a polar solution; (2) An electrode coating is prepared based on the electrode active material. The electrode coating is applied to the surface of the current collector and then dried and rolled to obtain the electrode sheet.

[0013] In some embodiments, the ball milling in step (1) is carried out under a protective gas atmosphere; in some embodiments, the ball milling is carried out under a protective gas atmosphere, wherein the protective gas is one or more of nitrogen, argon, helium, neon, krypton or xenon; in some embodiments, the protective gas is argon; in some embodiments, the ball milling speed is 300-500 rpm and the time is 2-6 hours; in some embodiments, the ball milling is carried out under an argon atmosphere at a speed of 400 rpm for 4 hours.

[0014] In this invention, elemental phosphorus powder and organic matter do not need to form bonds under high-energy ball milling; they only need to be mixed and entangled together under low-energy ball milling to function, effectively reducing energy consumption in the preparation process.

[0015] In some embodiments, the polar solution contains a polar solvent with electron-rich functional groups; in some embodiments, the polar solvent containing electron-rich functional groups is an amide solvent; in some embodiments, the amide solvent is N-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) or N-ethylpyrrolidone (NEP); in some embodiments, the amide solvent is N-methylpyrrolidone (NMP).

[0016] In some embodiments, the electrode coating is obtained by mixing an electrode active material, a conductive agent, and a binder.

[0017] In some embodiments, the mass ratio of the electrode active material, conductive agent, and binder is (8-9.5):(0.3-1.5):(0.3-1.5); in some embodiments, the mass ratio of the electrode active material, conductive agent, and binder is (8.5-9):(0.5-1):(0.5-1); in some embodiments, the mass ratio of the electrode active material, conductive agent, and binder is 9:0.5:0.5.

[0018] In some embodiments, the conductive agent is one or more of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, or graphene, and the binder is one or more of PVDF, PTFE, CMC, or SBR; in some embodiments, the conductive agent is conductive carbon black, and the binder is PVDF.

[0019] In some embodiments, the electrode coating is applied at a concentration of 0.6-1.2 mg / cm³. 2 The electrode coating is applied to the surface of the current collector at a loading rate of 0.7-1.0 mg / cm². 2 The electrode coating is applied to the surface of the current collector at a loading rate of 0.8 mg / cm²; in some embodiments, the electrode coating is applied at a loading rate of 0.8 mg / cm². 2 The loading amount is coated on the surface of the current collector; in some embodiments, the current collector is a metal foil; in some embodiments, the metal foil is a copper foil or an aluminum foil.

[0020] On one hand, the present invention provides an application of the electrode sheet described above or the electrode sheet prepared according to the preparation method described above in a sodium-ion battery; the electrode sheet provides active sites for sodium ion deposition, so that sodium ions are deposited in metallic form on the negative electrode current collector.

[0021] On one hand, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the electrode sheet described above or the electrode sheet prepared according to the preparation method described above.

[0022] The sodium-ion battery electrode sheet provided by this invention has the following beneficial effects: This invention modifies the current collector to reduce the deposition barrier of sodium ions and increase the nucleation sites for sodium ions on the current collector, thereby improving the initial efficiency and cycle performance of sodium-ion batteries. The current collector of this invention uses an electrode active material composed of elemental phosphorus powder and oxygen-containing organic matter, achieving a high reversible specific capacity of 780-801 mAh / g at a current density of 0.5 A / g, with a capacity retention rate of 95.2%-97.3% after 50 cycles. The electrode coating loading is controlled at 0.6-1.2 mg / cm³. 2 This ensures sufficient sodium ion deposition of active sites while significantly reducing the ineffective mass of the negative electrode and improving the battery energy density. Attached Figure Description

[0023] Figure 1 SEM image of the material prepared in Example 1; Figure 2 This is a SEM image of elemental phosphorus. Detailed Implementation

[0024] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.

[0025] Example 1 (1) Weigh 1.8g of black phosphorus powder and 0.2g of cellulose and put them into an agate ball mill jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. SEM images of the electrode are attached. Figure 1 As shown, compare the attached Figure 2 The smooth interface of elemental phosphorus and the relatively rough interface of the prepared material suggest that organic matter is coated on the surface of the material. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0026] Example 2 (1) Weigh 1.6g of black phosphorus powder and 0.4g of cellulose and put them into an agate ball mill jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0027] Example 3 (1) Weigh 1.8g of red phosphorus powder and 0.2g of cellulose and put them into an agate ball milling jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0028] Example 4 (1) Weigh 1.6g of red phosphorus powder and 0.4g of cellulose and put them into an agate ball milling jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0029] Example 5 (1) Weigh 1.8g of black phosphorus powder and 0.2g of glucose and put them into an agate ball mill jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0030] Example 6 (1) Weigh 1.6g of black phosphorus powder and 0.4g of glucose and put them into an agate ball mill jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0031] Comparative Example 1 This comparative example demonstrates the use of copper foil as an electrode without any electrode paste coating.

[0032] A sodium-ion battery was prepared using copper foil as the working electrode without any surface treatment, and sodium metal as the counter electrode to test its performance.

[0033] Comparative Example 2 This comparative example provides an electrode sheet prepared using only black phosphorus powder as the electrode slurry in the absence of organic matter.

[0034] (1) Weigh 2g of black phosphorus powder and put it into an agate ball mill jar. Mill it at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³.2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0035] Comparative Example 3 (1) Weigh 2g of red phosphorus powder and put it into an agate ball milling jar. Mill it at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and sodium metal as the counter electrode, sodium-ion batteries were prepared and their performance was tested.

[0036] Comparative Example 4 (1) Weigh 1.6g of black phosphorus powder and 0.4g of cellulose and put them into an agate ball mill jar. Mill the material at 400rpm for 4 hours under an argon atmosphere. After taking out the material, clean it with NMP and then dry it in a vacuum oven at 60℃ for 5 hours to obtain the active material. (2) The obtained materials are thoroughly mixed in a ratio of active material: conductive carbon black: PVDF = 9:0.5:0.5 to obtain an electrode slurry with uniformly distributed particles. The electrode slurry is then mixed at a concentration of 0.8 mg / cm³. 2 The loading amount is coated on copper foil to form a uniform electrode film. The electrode film is dried and rolled to finally prepare an electrode sheet with a certain thickness and structural characteristics. (3) Using the electrode sheet as the working electrode and lithium metal as the counter electrode, the performance of lithium-ion batteries was tested.

[0037] Battery performance test The batteries prepared in Examples 1-6 and Comparative Examples 1-4 were subjected to performance tests according to the following steps: 50 cycles under a charge-discharge condition of 0.5 A / g.

[0038] The battery performance test results are shown in Table 1: Table 1. Battery performance test results provided in the examples and comparative examples.

[0039] The initial capacity of Comparative Example 1 shows that sodium metal can be directly deposited on copper foil, but its battery energy decays rapidly during cycling. The extremely low capacity of Comparative Examples 2-3 after adding phosphorus powder indicates that it cannot be effectively used in sodium batteries. Theoretically, phosphorus powder provides more deposition sites for sodium ions, which helps sodium ion deposition. However, in practical applications, the reversible discharge specific capacity and capacity retention of Comparative Examples 2-3 are significantly reduced, even as low as 40.6%. In Comparative Example 4, the method provided by this invention is applied to a lithium-ion battery. Although it has a high initial reversible discharge specific capacity, its performance drops significantly after 50 cycles, and the capacity retention is only 71.9%.

[0040] In the embodiments 1-6 of the present invention, after phosphorus-organic compounding, not only was the sodium ion deposition site problem solved, but the capacity retention rate was also greatly improved, maintaining the capacity retention rate at over 90%.

Claims

1. A sodium-ion battery electrode sheet, characterized in that, The electrode sheet includes a current collector and an electrode coating applied to the surface of the current collector, wherein the electrode coating has a concentration of 0.6-1.2 mg / cm³. 2 The loading amount is coated on the surface of the current collector; The electrode coating is made of a mixture of elemental phosphorus powder and organic matter, wherein the organic matter accounts for 5%-40% of the mass of the mixture.

2. The electrode sheet according to claim 1, characterized in that, The electrode coating has a concentration of 0.7-1.0 mg / cm³. 2 The loading amount is coated on the surface of the current collector.

3. The electrode sheet according to claim 2, characterized in that, The current collector is a metal foil.

4. The electrode sheet according to claim 1, characterized in that, In the mixture of elemental phosphorus powder and organic matter, the organic matter accounts for 10%-20% by mass.

5. The electrode sheet according to claim 1, characterized in that, The electrode plates satisfy any one of (a)-(c): (a) The elemental phosphorus powder is at least one of black phosphorus or red phosphorus; (b) The organic compound is a carbohydrate compound; (c) The organic compound is a carbohydrate compound, which is at least one of a monosaccharide, a disaccharide, or a polysaccharide.

6. A method for preparing an electrode sheet as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) After ball milling and mixing the mixture of elemental phosphorus powder and organic matter, the electrode active material is obtained by cleaning with a polar solvent; (2) An electrode coating is prepared based on the electrode active material. The electrode coating is applied to the surface of the current collector and then dried and rolled to obtain the electrode sheet.

7. The preparation method according to claim 6, characterized in that, Step (1) satisfies any one of (e)-(i): (e) The ball milling mixing is carried out under a protective gas atmosphere; (f) The ball milling mixing is carried out under a protective gas atmosphere, wherein the protective gas is one or more of nitrogen, argon, helium, neon, krypton or xenon; (g) The ball milling mixing speed is 300-500 rpm and the time is 2-6 hours; (h) The polar solvent is a polar solvent containing electron-rich functional groups; (i) The polar solvent is a polar solvent containing electron-rich functional groups, and the polar solvent containing electron-rich functional groups is an amide solvent.

8. The preparation method according to claim 6, characterized in that, The electrode coating is obtained by mixing electrode active material, conductive agent and binder.

9. The preparation method according to claim 8, characterized in that, The mass ratio of the electrode active material, conductive agent and binder is (8-9.5): (0.3-1.5): (0.3-1.5).

10. The preparation method according to claim 8, characterized in that, The conductive agent is one or more of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes or graphene, and the binder is one or more of PVDF, PTFE, CMC or SBR.

11. The application of the electrode sheet according to any one of claims 1-5 or the electrode sheet prepared by the preparation method according to any one of claims 6-10 in a sodium-ion battery.

12. A sodium-ion battery, characterized in that, The sodium-ion battery comprises an electrode sheet as described in any one of claims 1-5 or an electrode sheet prepared by the preparation method according to any one of claims 6-10.

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