CN114824447A - Sodium battery and preparation method thereof - Google Patents

Abstract

The invention provides a sodium battery, and belongs to the technical field of batteries. The sodium battery comprises a positive electrode, a negative electrode, electrolyte and a diaphragm; the positive electrode includes an active material including at least one selected from the group consisting of sodium titanate, manganese dioxide, sulfur powder, and hard carbon; the active component of the negative electrode comprises sodium or sodium copper alloy, sodium aluminum alloy, sodium magnesium alloy and other alloys. The sodium battery has the advantages of low cost, high safety, high energy density, environmental protection and the like.

Description

A kind of sodium battery and preparation method thereof

technical field

The invention belongs to the technical field of batteries, and in particular relates to a sodium battery and a preparation method thereof.

Background technique

A secondary battery, also known as a rechargeable battery, is a battery that can be repeatedly charged and discharged for multiple uses. At present, the main secondary battery technologies are lead-acid batteries, nickel-chromium batteries, nickel-hydrogen batteries and lithium-ion batteries. Lithium-ion batteries are widely used in the field of energy storage due to their high energy density and long life. Sodium is located just below lithium in the periodic table of elements, and has the chemical properties closest to lithium metal, and is abundant in the earth's crust, which is thousands of times more abundant than lithium, so sodium-ion batteries are expected to become a new generation of high-performance, Low-cost energy storage technology. The working principle of sodium-ion battery is similar to that of lithium-ion battery. The core components of a sodium-ion battery include a positive electrode, a negative electrode, and an electrolyte. During charging, sodium ions are extracted from the positive electrode active material and embedded in the negative electrode active material; during discharge, sodium ions are extracted from the negative electrode active material and embedded in the positive electrode active material.

In order to avoid the precipitation of metallic sodium in the negative electrode, the design capacity of the negative electrode of the sodium ion battery should be higher than that of the positive electrode, so that the active material of the positive electrode determines the capacity of the sodium ion battery. At present, the main factors limiting the application of Na-ion batteries are: capacity and cycle stability, and these two limiting factors mainly depend on the theoretical specific capacity and structural stability of the cathode active material. Therefore, the development of high-performance cathode materials is the key to the application of Na-ion batteries. Existing cathode active materials for sodium ion batteries include layered oxides and organic cathodes. Layered oxides have high theoretical capacity but unsatisfactory structural stability, and organic cathodes have unsatisfactory theoretical capacity and structural stability, and the preparation process is also more complicated.

Therefore, there is still an urgent need for a sodium battery with high capacity, good structural stability, good safety and low cost.

SUMMARY OF THE INVENTION

To solve the above problems, the present invention provides a sodium battery.

A sodium battery, comprising: a positive electrode, a negative electrode, an electrolyte and a separator; the positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one selected from the group consisting of sodium titanate, manganese dioxide, sulfur powder and hard carbon The negative electrode includes a negative electrode active component, and the active component of the negative electrode includes sodium, sodium-copper alloy, sodium-aluminum alloy or sodium-magnesium alloy.

The negative electrode is a metal sodium composite copper current collector.

The positive electrode includes a positive electrode active material, a conductive agent and a binder.

The positive active material is sodium titanate and other positive active materials, and the other positive active materials are selected from at least one of manganese dioxide, sulfur powder, and hard carbon. In some embodiments, the positive active material is sodium titanate and hard carbon. In some embodiments, the positive active material is sodium titanate, manganese dioxide and hard carbon.

The mass ratio of the sodium titanate and other positive active materials is 1:9-9:1. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 1:7-7:1. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 1:6-6:1. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 1:5-5:1. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 1:3-3:1. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 2:1-1:2. In some embodiments, the mass ratio of the sodium titanate and other positive active materials is 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1: 2, 1:1.5, 45:55, 1:1, 55:45, 1.5:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9.

The weight ratio of the positive electrode active material, the conductive agent and the binder is (80-95):(0.5-8):(1-5). In some embodiments, the weight ratio of the positive active material, the conductive agent and the binder is (90-95):(2-6):(1-4). In some embodiments, the weight ratio of the positive electrode active material, the conductive agent and the binder is (90-95):(2-4):(2-3). In some embodiments, the weight ratio of the positive electrode active material, the conductive agent and the binder is (90-95):(3-4):(2-3).

The electrolyte includes sodium salt, solvent A and additives.

The sodium salt includes sodium hexafluorophosphate, sodium nitrate, sodium bisfluorosulfonimide (NaFSI), sodium bistrifluoromethanesulfonimide (NaTFSI), sodium difluorooxalate borate (NaODFB) and dioxalic acid At least one of sodium borate (NaBOB). In some embodiments, the sodium salts include sodium hexafluorophosphate and sodium nitrate. In some embodiments, the sodium salt comprises sodium hexafluorophosphate and sodium nitrate, and the weight ratio of sodium hexafluorophosphate and sodium nitrate is 0.5:99-99:0.5. In some embodiments, the sodium salt comprises sodium hexafluorophosphate and sodium nitrate, and the weight ratio of sodium hexafluorophosphate and sodium nitrate is 10:90-90:10. In some embodiments, the sodium salt includes sodium hexafluorophosphate and sodium nitrate, and the weight ratio of the sodium hexafluorophosphate and sodium nitrate is 10:90, 20:80, 30:70, 40:60, 45: 55, 50:50, 55:45, 60:40, 70:30, 80:20 or 90:10.

The solvent A includes a solvent selected from the group consisting of fluoroethylene carbonate (FEC), dimethyl ether (DME), FPC (fluoropropylene carbonate), FEMC, FDMC and perfluorodimethyl ether (CF ₃ OCF ₃ ). at least one. In some embodiments, the solvent A includes fluoroethylene carbonate and dimethyl ether.

The additives include CsPF ₆ (cesium hexafluorophosphate), FVC (fluoroethylene carbonate), FPS (fluoro 1, 3-propane sultone), FPST (fluoro 1, 3-propene sulfonate) acid lactone) and at least one of FSPA (fluoropropenyl sulfate). In some embodiments, the additive comprises at least one selected from CsPF ₆ (cesium hexafluorophosphate), FVC (fluoroethylene carbonate), FPS (fluoro 1,3-propane sultone) . In some embodiments, the additive comprises selected from the group consisting of _CsPF6 (cesium hexafluorophosphate), FVC (fluoroethylene carbonate), FPS (fluoro1,3-propane sultone).

The base material of the separator is selected from polyethylene or polypropylene.

The surface of the separator contains a coating, and the coating is ceramic, boehmite, sodium titanium aluminum phosphate and polyvinylidene fluoride or a mixture of any at least two thereof. In some embodiments, the surface of the separator contains a coating that is a mixture of ceramic, boehmite, sodium aluminum titanium phosphate, and polyvinylidene fluoride. In some embodiments, the surface of the separator contains a coating, the coating is a mixture of ceramic, boehmite, sodium titanium aluminum phosphate and polyvinylidene fluoride, the ceramic, boehmite, sodium titanium aluminum phosphate and The weight ratio of polyvinylidene fluoride is (33-50):(60-30):(5-10):(2-10). In some embodiments, the membrane surface contains a coating, and the coating is sodium titanium aluminum phosphate and polyvinylidene fluoride. In some embodiments, the surface of the separator contains a coating, and the coating is sodium aluminum titanium phosphate and polyvinylidene fluoride, and the weight ratio of sodium aluminum titanium phosphate and polyvinylidene fluoride is 80:20-95: 5.

Based on the total volume of the electrolyte, the content of the sodium salt is 0.5 mol/L-5.0 mol/L. In some embodiments, based on the total volume of the electrolyte, the content of the sodium salt is 0.5mol/L, 0.9mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L L, 3.0mol/L, 3.5mol/L, 4.0mol/L, 4.5mol/L or 5.0mol/L. In some preferred embodiments, based on the total volume of the electrolyte, the content of the sodium salt is 0.9 mol/L-2.0 mol/L.

The content of each of the additives is 0.5wt%-10wt% based on the total mass of the electrolyte. In some preferred embodiments, the content of each of the additives is 1.0wt%-5wt% based on the total mass of the electrolyte. In some embodiments, based on the total mass of the electrolyte, the content of each of the additives is 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt% , 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt% or 10wt% %.

The solvent A is fluoroethylene carbonate and dimethyl ether, and the mass ratio of the fluoroethylene carbonate and dimethyl ether is 10:90-90:10, 20:80-80:20, 30:70- 70:30 or 40:60-60:40.

The thickness of the base material of the separator is 10 to 40 microns.

The thickness of the coating is 1 to 5 microns.

The preparation method of the positive electrode comprises: mixing the positive electrode active material, the conductive agent and the binder with the solvent B, coating on the aluminum foil current collector, drying, and forming by quinone pressing.

The binder is selected from the group consisting of polyvinylidene fluoride.

The solvent B is selected from N-methylpyrrolidone.

In the preparation method of described positive electrode, the ratio of the mass sum of described active component, conductive agent and binder and the mass of solvent B is 30:70-60:40. In some embodiments, in the preparation method of the positive electrode, the ratio of the sum of the mass of the active ingredient, the conductive agent and the binder to the mass of the solvent B is 40:60-50:50.

The preparation method of the negative electrode includes: compounding the flake-shaped negative electrode active component on the copper current collector or coating the negative electrode active component with a powder anhydrous solvent or powder sputtering on the copper current collector.

The sodium battery may also include an outer package.

The outer package includes aluminum-plastic film, metal shell or plastic shell.

beneficial effect

Compared with the prior art, an embodiment of the present invention has at least one of the following technical effects:

(1) The positive electrode active material adopts sodium titanate and other positive electrode active materials (such as manganese dioxide, sulfur powder or hard carbon), which can play a synergistic technical effect. Compared with the use of sodium titanate alone or the use of other positive electrodes alone The active material has better charge-discharge cycle capacity retention rate and improves the safety of the battery.

(2) The negative electrode active component adopts sodium, or sodium copper alloy, sodium aluminum alloy or sodium magnesium alloy, which is beneficial to improve the stability and workability of the negative electrode.

(3) By selecting a suitable electrolyte solvent, it is beneficial to improve the cycle performance, power and temperature performance of the battery.

(4) Compared with the sodium batteries of other formulations, the sodium batteries provided by the present invention have less platform change after being placed at 80° C. for 4 hours.

(5) Compared with the electrolytic solution using a single solvent, the present invention can greatly reduce the internal resistance change after being placed at 80°C for 4 hours by using a variety of solvents.

(6) Compared with the sodium batteries of other formulations, the sodium batteries provided by the present invention have smaller and more stable capacity changes after being placed at 80°C for 4 hours, and the positive active materials are more preferably hard carbon and sodium titanate.

Definition of Terms

Unless otherwise specified, the following terms and phrases as used herein are intended to have the following meanings:

The term "V/V" denotes a volume ratio.

The term "wt%" means the mass percentage of the component in the total mass of the composition.

The term "M" or "mol/L" means "mole per liter".

The terms "optional", "optional" or "optionally" indicate that the technical feature modified by the term may or may not be present.

In the following, all numbers disclosed herein are approximations, whether or not the words "about" or "about" are used. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15% or 20%. Whenever a number with a value of N is disclosed, any with N+/-1%, N+/-2%, N+/-3%, N+/-5%, N+/-7%, N+/-8%, N+ //-10%, N+/-15% or N+/-20% values are explicitly disclosed, where "+/-" means plus or minus.

In the description of the present invention, it should be understood that the terms "first" and "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Detailed ways

In order to make those skilled in the art better understand the technical solutions of the present invention, some non-limiting embodiments are further disclosed below to further describe the present invention in detail.

The reagents used in the present invention can be purchased from the market or can be prepared by the method described in the present invention.

One skilled in the art will recognize that many methods and materials similar or equivalent to those described herein could be used in the practice of the present invention. The present invention is in no way limited to the methods and materials described herein. In the event that one or more of the incorporated literature, patents, and similar materials differs from or contradicts this application (including, but not limited to, terms defined, uses of terms, techniques described, etc.), this Application shall prevail.

It should further be appreciated that certain features of the invention, which are, for clarity, described in the context of multiple separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, can also be provided separately or in any suitable subcombination.

Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents and publications referred to herein are incorporated by reference in their entirety.

Example 1: Preparation of sodium battery (positive electrode active material is hard carbon and sodium titanate)

The preparation of the positive electrode: take 32 parts by weight of sodium titanate, 48 parts by weight of hard carbon, 3.5 parts by weight of PVDF (polyvinylidene fluoride) and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, apply Distributed on 25-micron-thick aluminum foil, baked, rolled, and slit to form pole pieces.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 2wt% FPS, 0.2M CsPF ₆ and 2wt% FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55 :45.

Diaphragm: Sodium titanium aluminum phosphate and polyvinylidene fluoride coated diaphragm substrate, the illustrated diaphragm substrate is polypropylene, and the weight ratio of the titanium aluminum sodium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Example 2: Preparation of sodium battery (positive electrode active material is hard carbon and sodium titanate)

Preparation of the positive electrode: take 40 parts by weight of sodium titanate, 40 parts by weight of hard carbon, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, and coat them on a 25-micron thick film. On the aluminum foil, the pole pieces are made after baking, rolling and slitting.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.1 M CsPF ₆ , 1 wt % FPS and 1 wt % FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery

Example 3: Preparation of sodium battery (positive active material is manganese dioxide and sodium titanate)

Preparation of positive electrode: take 40 parts by weight of sodium titanate, 40 parts by weight of manganese dioxide, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, and coat to a thickness of 25 microns On the aluminum foil, the pole pieces are made after baking, rolling and slitting.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.05M CsPF ₆ , 5wt% FPS and 5wt% FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Example 4: Preparation of sodium battery (positive active material is sulfur powder and sodium titanate)

Preparation of the positive electrode: take 40 parts by weight of sodium titanate, 40 parts by weight of sulfur powder, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, and coat them on a 25-micron-thick On the aluminum foil, the pole pieces are made after baking, rolling and slitting.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.01M CsPF ₆ , 10wt% FPS and 10wt% FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Comparative Example 1: Preparation of sodium battery (positive electrode active material is hard carbon)

Preparation of the positive electrode: take 80 parts by weight of hard carbon, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, and coat them on a 25-micron-thick aluminum foil. The pole pieces are made after the rollers are cut and cut.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.1M CsPF ₆ , 2wt% FPS and 2wt% FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Comparative Example 2: Preparation of sodium battery (positive electrode active material is sodium titanate)

Preparation of positive electrode: take 80 parts by weight of sodium titanate, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone evenly, apply them to 25 micron thick aluminum foil, and bake them , Roll and cut into pole pieces.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.1 M CsPF ₆ , 1 wt % FPS and 1 wt % FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Comparative Example 3: Preparation of sodium battery (positive electrode active material is manganese dioxide)

Preparation of positive electrode: take 80 parts by weight of manganese dioxide, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methyl pyrrolidone, and apply them to 25-micron-thick aluminum foil. After baking , Roll and cut into pole pieces.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.1 M CsPF ₆ , 1 wt % FPS and 1 wt % FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Comparative Example 4: Preparation of sodium battery (positive electrode active material is sulfur powder)

The preparation of the positive electrode: take 80 parts by weight of sulfur powder, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, and mix them with 130 parts by weight of N-methylpyrrolidone evenly, then apply it to 25 micron thick aluminum foil, after baking, The pole pieces are formed after the rollers are cut and cut.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1M NaPF ₆ , 0.05M CsPF ₆ , 5wt% FPS and 5wt% FVC, the solvent of the solution is a mixture of FEC and DME, and the weight ratio of FEC and DME is 55: 45.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Comparative Examples 5 to 6: Investigation of Electrolyte Solvents

Preparation of positive electrode: take 32 parts by weight of sodium titanate, 48 parts by weight of hard carbon, 3.5 parts by weight of PVDF and 2.5 parts by weight of conductive agent S-P, mix them with 130 parts by weight of N-methylpyrrolidone, and coat them on a 25-micron thick On the aluminum foil, the pole pieces are made after baking, rolling and slitting.

Preparation of negative electrode: 30-micron-thick metal sodium strips were compounded on 10-micron-thick copper foil, rolled in an oxygen-free and anhydrous environment, and cut into negative electrode pieces.

Electrolyte: a solution containing 1 M NaPF ₆ , 0.1 M CsPF ₆ , 2 wt % FPS and 10 wt % FVC, and the solvents of the solutions are shown in Table 1, respectively.

Diaphragm: Coating the diaphragm substrate with sodium aluminum titanium phosphate and polyvinylidene fluoride, the shown diaphragm substrate is polypropylene, and the weight ratio of the sodium aluminum titanium phosphate and polyvinylidene fluoride is 50:50.

Preparation of sodium battery: Take the above positive electrode, negative electrode, electrolyte and separator, and assemble into a soft pack battery.

Table 1: Investigation of Electrolyte Solvents

Example Electrolyte Solvent Comparative Example 5 FEC Comparative Example 6 DME

Effect Example 1: Cyclic charge-discharge capacity retention test

0.5C cycle charge-discharge capacity retention rate test: Take the sodium batteries obtained in Examples 1-4 and Comparative Examples 1-6 respectively. Under normal temperature environment, the battery is charged to 3.9V with a constant current of 0.5C, and then transferred to a constant voltage of 3.9V. Charging, when the charging current is less than 0.05C, the charging is terminated; the battery is put on hold for 30min, and then discharged to 1.5V at a constant current of 0.5C; let stand for 10min. Repeat the above steps to complete 300 cycles. Record the discharge capacity each time, and calculate the percentage of the 300-time discharge capacity and the first discharge capacity. The results are shown in Table 2.

1C cycle charge-discharge capacity retention rate test: Take the sodium batteries obtained in Examples 1-4 and Comparative Examples 1-6 respectively. Under the normal temperature environment, the battery is charged to 3.9V with a constant current of 1C, and then transferred to a constant voltage of 3.9V for charging. When the charging current is less than 0.05C, the charging is terminated; the battery is put on hold for 30 minutes, and then discharged to 1.5V at a constant current of 1C; left for 10 minutes. Repeat the above steps to complete 300 cycles. Record the discharge capacity each time, and calculate the percentage of the 300-time discharge capacity and the first discharge capacity. The results are shown in Table 2.

Table 2: Capacity retention results of 300 cycles of charge and discharge at 0.5C and 1C

Conclusion: The sodium battery provided by the present invention has a higher capacity retention rate after repeated charge and discharge cycles than other sodium batteries.

Effect Example 2: High temperature storage performance test

Take the sodium batteries obtained in Example 1-Example 4 (model 100200300 36Ah2.5V) and the sodium batteries obtained in Comparative Example 1-Comparative Example 6, and store them at 80°C for 4 hours, respectively, and test the properties described in Table 3 and Table 4, The results are shown in Tables 3 and 4.

Table 3: Example high temperature 80 ℃ storage performance test

Table 4: Comparative example high temperature 80 ℃ storage performance test

in conclusion:

(1) Compared with the sodium batteries of other formulations, the sodium batteries provided by the present invention have smaller changes in the platform after being placed at 80° C. for 4 hours.

(2) Compared with the electrolytic solution using a single solvent, the present invention can greatly reduce the internal resistance change after being placed at 80°C for 4 hours by using a variety of solvents.

(3) Compared with sodium batteries of other formulations, the sodium batteries provided by the present invention have smaller and more stable capacity changes after being placed at 80° C. for 4 hours. The substances are more preferably hard carbon and sodium titanate.

The method of the present invention has been described through the preferred embodiments, and it is obvious that relevant persons can modify or appropriately change and combine the methods and applications described herein within the content, spirit and scope of the present invention to realize and apply the technology of the present invention . Those skilled in the art can refer to the content of this document to appropriately improve the process parameters to achieve. It should be particularly pointed out that all similar substitutions and modifications apparent to those skilled in the art are deemed to be included in the present invention.

Claims (10)

1. A sodium battery, comprising: a positive electrode, a negative electrode, an electrolyte and a separator; the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises a sodium titanate, manganese dioxide, sulfur powder and hard carbon At least one; the negative electrode includes a negative electrode active component, and the negative electrode active component includes sodium, sodium-copper alloy, sodium-aluminum alloy or sodium-magnesium alloy. 2. The sodium battery according to claim 1, wherein the negative electrode is a metal sodium composite copper current collector; Optionally, the positive electrode includes a positive electrode active material, a conductive agent and a binder. 3. The sodium battery according to claim 2, wherein the positive active material is sodium titanate and other positive active materials, and the other positive active materials are selected from at least one of manganese dioxide, sulfur powder, and hard carbon; Optionally, the mass ratio of the sodium titanate and other positive active materials is 1:2-2:1; Optionally, the weight ratio of the positive electrode active material, conductive agent and binder is (80～95):(0.5～8): (1 to 5). 4. The sodium battery according to any one of claims 1-3, wherein the electrolyte comprises sodium salt, solvent A and additives. 5. The sodium battery according to any one of claims 1-4, wherein the sodium salt comprises sodium hexafluorophosphate, sodium nitrate, sodium bisfluorosulfonimide, sodium bistrifluoromethanesulfonimide, at least one of sodium difluorooxalate borate and sodium dioxalate borate; or the sodium salt includes sodium hexafluorophosphate and sodium nitrate; Optionally, the solvent A comprises selected from the group consisting of fluoroethylene carbonate (FEC), dimethyl ether (DME), FPC (fluoropropylene carbonate), FEMC, FDMC and perfluorodimethyl ether (CF ₃ OCF ₃ ) at least one; or the solvent A includes fluoroethylene carbonate and dimethyl ether; Optionally, the additive comprises selected from the group consisting of cesium hexafluorophosphate, fluoroethylene carbonate, fluoro1,3-propene sultone, fluoro1,3-propene sultone, and fluoropropene sulfate at least one of the esters; Optionally, the base material of the separator comprises selected from polyethylene or polypropylene; Optionally, the surface of the separator contains a coating, and the coating is ceramic, boehmite, sodium aluminum titanium phosphate, and polyvinylidene fluoride, or a mixture of at least two of them. 6. The sodium battery according to claim 5, wherein the sodium salt is sodium hexafluorophosphate and sodium nitrate, and the mass ratio of the sodium hexafluorophosphate and sodium nitrate is (0.5～99): (99～0.5); Optionally, based on the total volume of the electrolyte, the content of the sodium salt is 0.5mol/L-5.0mol/L; Optionally, based on the total mass of the electrolyte, the content of each of the additives is 0.2wt%-10wt%; Optionally, the solvent A is fluoroethylene carbonate and dimethyl ether, and the mass ratio of the fluoroethylene carbonate and dimethyl ether is 10:90-90:10, 20:80-80:20, 30:70-70:30 or 40:60-60:40. 7. The sodium battery according to any one of claims 1-6, wherein the thickness of the base material of the separator is 10 to 40 microns; Optionally, the thickness of the coating is 1 to 5 microns. 8. The sodium battery according to any one of claims 1-7, the preparation method of the positive electrode comprises: mixing the positive electrode active material, the conductive agent and the binder with the solvent B, coating on the aluminum foil current collector, baking Dry, quinone press molding. 9. The sodium battery of claim 8, wherein the binder comprises polyvinylidene fluoride; Optionally, the solvent B comprises N-methylpyrrolidone selected from the group consisting of. 10. The sodium battery according to any one of claims 1-9, wherein the preparation method of the negative electrode comprises: compounding a sheet-shaped negative electrode active component on a copper current collector or coating the negative electrode active component with a powder anhydrous solvent. The cloth or powder is sputtered onto the copper current collector.