High-specific-energy sodium ion battery

Abstract

The invention belongs to the field of electrochemical energy storage, and particularly relates to a sodium ion battery. In order to solve the problem of low energy density of the sodium-ion battery, the metal cyanamide compound negative electrode material with high specific energy is developed and applied to the sodium-ion battery, and the energy density can be greatly improved compared with that of a traditional hard carbon negative electrode sodium-ion battery. Specifically, metal cyanamide compounds including FeNCN, ZnNCN, CuNCN and the like are used as negative electrode active materials to design and prepare the sodium ion battery with high specific energy, and higher energy density and longer cycle life can be realized under the condition of higher charge-discharge rate.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy storage, and particularly relates to a sodium-ion battery. Background Art

[0002] Low-cost energy storage technology is the key to realizing the sustainable use of large-scale clean energy. Sodium-ion batteries have the advantages of no dependence on lithium resources, low raw material costs, relatively high energy density, high safety, good low-temperature performance and rate performance, and are a new type of electrochemical energy storage technology route suitable for large-scale promotion. However, the energy density of sodium-ion batteries is generally lower than that of lithium-ion batteries, making it difficult to meet the high-energy-density energy storage applications such as electric vehicles and drones, which restricts the further application of sodium-ion batteries. Therefore, it is urgent to apply new electrode materials to develop high specific energy sodium-ion batteries. Summary of the Invention

[0003] Based on the problem of the low energy density of sodium-ion batteries, the present invention develops a high specific energy metal cyanamide compound negative electrode material and applies it to sodium-ion batteries, which can significantly improve the energy density compared with traditional hard carbon negative electrode sodium-ion batteries. The present invention is achieved as follows:

[0004] The present invention includes a high specific energy sodium-ion battery, characterized in that the high specific energy sodium-ion battery is composed of a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The negative electrode sheet includes a negative electrode active material, a binder, a conductive agent, and a negative electrode current collector, wherein the negative electrode active material is a metal cyanamide compound with the chemical formula Mx[NCN]y.

[0005] Preferably, the metal cyanamide compound includes one or more of FeNCN, ZnNCN, and CuNCN, and FeNCN is preferably selected.

[0006] Preferably, the morphology of the metal cyanamide compound is one or more of sheet-like, granular, amorphous, and porous, and sheet-like is preferably selected.

[0007] Preferably, the size of the metal cyanamide compound is between 5 nanometers and 50 micrometers, and 1 micrometer to 10 micrometers is preferably selected.

[0008] Preferably, the positive electrode sheet includes a positive electrode current collector, a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material includes one or more of sodium-containing layered metal oxides, sodium vanadium phosphate, sodium fluorovanadate, Prussian blue, sodium iron phosphate, and sodium iron sulfate, and sodium-containing layered metal oxides and sodium vanadium phosphate are preferably selected.

[0009] Preferably, the loading amount of the positive electrode active material on the surface of the positive electrode sheet is 1-50 mg / cm 2 , and 20-30 mg / cm 2 .

[0010] Preferably, the electrolyte contains sodium salt, solvent and additive, wherein the sodium salt includes one or more of NaPF6, NaOTF, NaFSI, NaTFSI, NaBF4, NaBOB, NaDFOB, NaClO4, and preferably NaPF6 and NaTFSI.

[0011] Preferably, the solvent in the electrolyte includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC), and preferably a mixed solvent of dimethyl carbonate (DMC) and ethylene carbonate (EC).

[0012] Preferably, the positive current collector and the negative current collector include one or more of aluminum foil, copper foil, composite aluminum foil, composite copper foil, carbon-coated aluminum foil, carbon-coated copper foil, carbon fiber cloth, and carbon paper, and preferably aluminum foil and composite aluminum foil.

[0013] Preferably, the conductive agents in the positive electrode and the negative electrode include one or more of conductive carbon black, acetylene black, hard carbon, soft carbon, graphite, carbon nanotubes, graphene, biomass pyrolysis carbon, graphdiyne, and carbon fiber, and preferably conductive carbon black and acetylene black. Description of the Drawings

[0014] Figure 1 . Shows a physical photo of the battery prepared in Example 1. Detailed Embodiments

[0015] In order to further illustrate the content, features and actual effects of the present invention, the present invention will be described in detail below with reference to the embodiments. It should be noted that the modified methods designed by the present invention are not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent substitutions and modifications made by those skilled in the art on the basis of reading the content of the present invention are also within the scope of protection required by the present invention.

[0016] To prepare the high specific energy sodium ion battery of the present invention, the preparation method is a conventional method in the art. The conventional preparation process of the embodiment includes: stacking the positive electrode sheet, the separator, and the negative electrode sheet, and performing subsequent processes such as electrolyte injection and encapsulation.

[0017] The sodium ion battery in the embodiment of the present invention can specifically be a button battery, a cylindrical battery, a soft package battery, a square shell battery, a blade battery, etc., without special limitation.

[0018] Specifically, the separator used in the high specific energy sodium-ion battery of the present invention is a conventional polymer separator material and a polymer / inorganic composite separator material in the art, which has a porous structure, can adsorb the electrolyte therein, and has good mechanical properties and high temperature resistance. In some preferred embodiments, the polymer separator material includes one or more of polypropylene, polyethylene, and polyimide, and specific implementation needs to be selected according to performance requirements such as sodium ion rate performance, operating temperature, and service life.

[0019] Specifically, the electrolyte includes sodium salt, solvent, and additive. If an organic solvent is used as the solvent, the total concentration of sodium salt can be selected from 0.1 to 3 M, such as 0.5 M, 0.8 M, 1.0 M, 1.2 M, 1.5 M, and is adjusted according to the selection of the positive electrode material and the battery performance requirements.

[0020] In the invention embodiment, the negative electrode sheet is generally prepared by a coating method. A certain proportion of negative electrode active material, conductive agent, and binder are stirred evenly in a solvent (such as water) to form a slurry, and then the slurry is coated on the surface of the negative electrode current collector, and dried and roll-pressed to obtain the negative electrode sheet. The positive electrode sheet can also be prepared by a coating method. The positive electrode active material, conductive agent, and binder are stirred evenly in a solvent (such as NMP) to form a slurry, and then the slurry is coated on the surface of the positive electrode current collector, and dried and roll-pressed to obtain the positive electrode sheet.

[0021] Example 1

[0022] Sodium manganate is used as the positive electrode active material. The positive electrode active material, PVDF, and acetylene black are placed in an NMP solvent in a mass ratio of 8:1:1 to form a slurry. The slurry is coated on the surface of the aluminum foil, dried, roll-pressed, and cut to prepare the positive electrode sheet. FeNCN is used as the negative electrode active material. The negative electrode active material, sodium carboxymethylcellulose, and acetylene black are mixed in a ratio of 8:1:1 to prepare a slurry. The slurry is coated on the surface of the aluminum foil, dried, roll-pressed, and cut to prepare the negative electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, injected with liquid and encapsulated to make a battery.

[0023] Referring to the preparation process of Example 1, Examples 2-6 and Comparative Example 1 are prepared. Except for the different compositions of the positive electrode active material and the negative electrode active material in Table 1, other conditions are the same for the examples and the comparative example.

[0024] At 25 °C, the LAND-CT2001C battery test system of Blue Electric Company is used to perform a constant current charge and discharge test on the batteries of Examples 1-6 and Comparative Example 1, record the charge and discharge specific capacity of each cycle at a 1C rate, calculate the battery energy density and cycle performance, and the recorded results are as follows in the table:

[0025] Table 1

[0026]

Claims

1. A high specific energy sodium-ion battery, characterized in that: The high specific energy sodium-ion battery is composed of a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The negative electrode sheet includes a negative electrode active material, a binder, a conductive agent, and a negative electrode current collector. The negative electrode active material is a metal cyanamide compound with the chemical formula Mx[NCN]y.

2. The high specific energy sodium ion battery according to claim 1, characterized in that, The metal cyanamide compound includes one or more of FeNCN, ZnNCN, and CuNCN.

3. The high specific energy sodium ion battery according to claim 1, wherein The morphology of the metal cyanamide compound is one or more of flaky, granular, amorphous, and porous.

4. The high specific energy sodium ion battery according to claim 1, characterized in that The size of the metal cyanamide compound is between 5 nanometers and 50 micrometers.

5. The high specific energy sodium ion battery according to claim 1, characterized in that The positive electrode sheet includes a positive electrode current collector and a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes one or more of sodium-containing layered metal oxides, sodium vanadium phosphate, sodium fluorovanadate, Prussian blue, sodium iron phosphate, and sodium iron sulfate.

6. The high specific energy sodium ion battery according to claim 1, wherein The loading amount of the positive electrode active material on the surface of the positive electrode sheet is 1 to 50 mg / cm 2 .

7. The high specific energy sodium ion battery according to claim 1, characterized in that The electrolyte contains a sodium salt, a solvent, and an additive. The sodium salt includes one or more of NaPF6, NaOTF, NaFSI, NaTFSI, NaBF4, NaBOB, NaDFOB, and NaClO4.

8. The high specific energy sodium ion battery according to claim 1, characterized in that, The solvent in the electrolyte includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC).

9. The high specific energy sodium ion battery according to claim 1, wherein The positive electrode current collector and the negative electrode current collector include one or more of aluminum foil, copper foil, composite aluminum foil, composite copper foil, carbon-coated aluminum foil, carbon-coated copper foil, carbon fiber cloth, and carbon paper.

10. The high specific energy sodium ion battery according to claim 1, wherein The conductive agent in the positive electrode and the negative electrode includes one or more of conductive carbon black, acetylene black, hard carbon, soft carbon, graphite, carbon nanotubes, graphene, biomass pyrolysis carbon, graphdiyne, and carbon fiber.

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