Negative electrode material and preparation method therefor, negative electrode sheet, battery cell and sodium-ion battery

Abstract

Provided is a preparation method for a negative electrode material of a sodium-ion battery. The method comprises: mixing ethylene tar with a hard carbon material; subjecting the mixed material to immersion treatment in an immersion furnace; and subjecting the immersed hard carbon material to carbonization treatment to obtain a hard carbon negative electrode material. Further provided are a negative electrode material obtained by means of the method, and a negative electrode sheet, a battery cell and a sodium-ion battery containing the negative electrode material. The soft-carbon-coated and -filled hard carbon material prepared by means of the method has high first effect, high compaction and excellent cycle stability, which facilitates the large-scale production of the negative electrode material and improves the use feasibility of the hard carbon material in a sodium-ion battery.

Description

Negative electrode material and preparation method thereof, negative electrode sheet, battery cell and sodium ion battery

[0001] Related applications

[0002] This application claims priority to the Chinese patent application filed on June 14, 2023, with application number 202310708074.X and entitled “Negative electrode material and preparation method thereof, negative electrode sheet, battery cell and sodium ion battery”, the full text of which is hereby incorporated by reference. Technical Field

[0003] The present disclosure relates to the technical field of secondary batteries, and in particular to negative electrode materials and preparation methods thereof, negative electrode sheets, battery cells and sodium ion batteries. Background Art

[0004] Sodium-ion battery is a rechargeable battery that mainly relies on the movement of sodium ions between the positive and negative electrodes to work.

[0005] Currently, sodium-ion batteries include a battery cell consisting of a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets. The battery cell is placed in an electrolyte. Sodium-ion batteries rely on the movement of sodium ions between the positive and negative electrodes to work.

[0006] Currently, hard carbon is used as the negative electrode material in sodium-ion batteries. Hard carbon materials cannot be graphitized, and their carbon layers are less regularly arranged than soft carbon, resulting in a larger number of micropores between the layers, facilitating the insertion and extraction of ions. Furthermore, hard carbon materials offer advantages such as high metal storage capacity, low metal storage voltage, and stable cycling, making them a commonly used negative electrode material.

[0007] Summary of the Invention

[0008] According to various embodiments of the present application, a negative electrode material and a preparation method thereof, a negative electrode sheet, a battery cell and a sodium ion battery are provided.

[0009] A first aspect of the present disclosure provides a method for preparing a negative electrode material for a sodium ion battery, comprising:

[0010] mixing ethylene tar with a hard carbon material;

[0011] The mixed material of ethylene tar and hard carbon material is impregnated in an impregnation furnace;

[0012] The impregnated hard carbon material is carbonized to obtain a hard carbon negative electrode material.

[0013] In one embodiment, the D50 of the hard carbon material is in the range of 4 μm-10 μm, and the specific surface area is 3.0 g / m 2 -10.0g / m 2 .

[0014] In one embodiment, the D50 of the hard carbon material is in the range of 5 μm to 6.5 μm.

[0015] In one embodiment, the specific surface area of ​​the hard carbon material is 5 g / m 2 -6g / m 2 .

[0016] In one embodiment, the mass ratio of ethylene tar to hard carbon material is 5:100-15:100.

[0017] In one embodiment, the mass ratio of ethylene tar to hard carbon material is 7:100-9:100.

[0018] In one embodiment, the mixture of ethylene tar and hard carbon material is impregnated in an impregnation furnace, comprising:

[0019] placing a mixture of ethylene tar and hard carbon material in an impregnation furnace;

[0020] The impregnation furnace is evacuated and heated;

[0021] The heated impregnation furnace is pressurized for impregnation.

[0022] In one embodiment, the heating temperature in the impregnation furnace ranges from 100° C. to 300° C., the pressure ranges from 0.8 MPa to 2 MPa, and the impregnation time ranges from 2 h to 6 h.

[0023] In one embodiment, the temperature range of the carbonization process is 900° C. to 1200° C., and the carbonization time is 3 hours to 6 hours.

[0024] In one embodiment, the temperature range of the carbonization process is 1000°C to 1100°C.

[0025] In one embodiment, ethylene tar is mixed with a hard carbon material, comprising:

[0026] Ethylene tar is added to the hard carbon material and stirred to obtain a mixed material of ethylene tar and the hard carbon material.

[0027] A second aspect of the present disclosure provides a negative electrode material for a sodium ion battery, comprising:

[0028] A hard carbon negative electrode material is prepared using the negative electrode material of any of the above embodiments.

[0029] A third aspect of the present disclosure provides a negative electrode sheet for a sodium ion battery, comprising:

[0030] The current collector and the negative electrode active material include the above-mentioned negative electrode material, a conductive agent and a binder.

[0031] A fourth aspect of the present disclosure provides a sodium ion battery cell, comprising:

[0032] positive electrode;

[0033] The above-mentioned negative electrode sheet;

[0034] The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet.

[0035] A fifth aspect of the present disclosure provides a sodium ion battery, comprising:

[0036] case;

[0037] The above-mentioned battery cell encapsulated in a shell;

[0038] Inject the electrolyte into the shell.

[0039] The details of one or more embodiments of the present application are set forth in the following drawings and descriptions. Other features, objects and advantages of the present application will become apparent from the specification, drawings and claims. As described above, the present disclosure provides a negative electrode material and a preparation method thereof, a negative electrode sheet, a battery cell and a sodium ion battery. In this embodiment, ethylene tar is used as a filler and a coating agent. By impregnation, the ethylene tar fills the internal pores of the hard carbon material and adheres to its surface. Then, by carbonization, the soft carbon formed by the ethylene tar can fill the mesopores and macropores inside the hard carbon, reduce surface defects, and will not change the microporous structure of the hard carbon material. In particular, ethylene tar has good fluidity and a certain viscosity at room temperature, which can reduce the temperature and pressure requirements of the impregnation process. During the impregnation process, the volatile matter of ethylene tar is relatively low and the residual carbon rate is high. During the heat treatment process, it is not easy to form a large number of pores due to the volatilization of impurities. The prepared soft carbon-coated and filled hard carbon material has high first efficiency, high compaction and excellent cycle stability, which is conducive to the large-scale production of negative electrode materials and improves the feasibility of using hard carbon materials in sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to better describe and illustrate the embodiments and examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be considered to limit the scope of the disclosed inventions, the presently described embodiments and examples, and any of the best modes currently understood for these inventions.

[0041] FIG1 shows a flow chart of a method for preparing a negative electrode material according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present disclosure using specific examples. Those skilled in the art can easily understand the other advantages and benefits of the present disclosure from the information disclosed herein. The present disclosure can also be implemented or applied to systems using different specific embodiments. The details of the present disclosure can also be modified or altered based on different viewpoints and application systems without departing from the spirit of the present disclosure. It should be noted that the embodiments and features of the embodiments in the present disclosure can be combined with each other unless they conflict.

[0043] The following is a detailed description of the embodiments of the present disclosure with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in many different forms and is not limited to the embodiments described herein.

[0044] In the present disclosure, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and integrate different embodiments or examples described in the present disclosure, as well as features of different embodiments or examples, unless otherwise contradictory.

[0045] Although not defined differently, all terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art to which this disclosure belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with relevant technical literature and the current message. Unless otherwise defined, they should not be overly interpreted as ideal or highly formalized meanings.

[0046] Research on related technologies revealed that hard carbon materials, while being used as negative electrode materials for sodium-ion batteries due to their advantages, are subject to the volatilization and overflow of impurity components during the synthesis process, resulting in the formation of a large number of pores within the hard carbon particles. This results in a large specific surface area and low compaction density. This leads to low initial efficiency, low volumetric energy density, and poor cycle stability when used as negative electrode materials for sodium-ion batteries. This reduces the feasibility of using hard carbon materials in sodium-ion batteries.

[0047] FIG1 is a flow chart of a method for producing negative electrode materials for sodium ion batteries according to an embodiment of the present application. It should be understood that although the steps in the flow chart shown in FIG1 are displayed in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction for the execution of these steps, and they can be performed in other orders. Moreover, at least a portion of the steps in FIG1 may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily performed at the same time, but can be performed at different times, and their execution order is not necessarily sequential, but can be performed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0048] As shown in FIG1 , the preparation method includes but is not limited to the following steps:

[0049] Step 110: mixing ethylene tar with a hard carbon material;

[0050] Step 120: impregnating the mixture of ethylene tar and hard carbon material in an impregnation furnace;

[0051] Step 130: performing carbonization treatment on the impregnated hard carbon material to obtain a hard carbon negative electrode material.

[0052] This embodiment uses ethylene tar as a filler and coating agent. Through impregnation, the ethylene tar fills the internal pores of the hard carbon material and adheres to its surface. Subsequently, through carbonization, the soft carbon formed from the ethylene tar fills the mesopores and macropores within the hard carbon material, reducing surface defects without changing the hard carbon material's microporous structure, thereby improving the hard carbon material's initial efficiency, compaction density, and cycling stability. It is understood that initial efficiency specifically refers to the initial charge and discharge efficiency, which is the ratio of the initial discharge capacity to the initial charge capacity.

[0053] In particular, ethylene tar has good fluidity and a certain viscosity at room temperature, which can reduce the temperature and pressure requirements of the impregnation process. During the impregnation process, ethylene tar has a relatively low volatility and a high residual carbon content. It is not easy to form a large number of pores due to the volatilization of impurities during heat treatment. The prepared soft carbon-coated and filled hard carbon material has a high initial efficiency, high compaction density, and excellent cycle stability. This is conducive to the large-scale production of negative electrode materials and improves the feasibility of using hard carbon materials in sodium-ion batteries.

[0054] In an embodiment of the present disclosure, ethylene tar is mixed with a hard carbon material, comprising:

[0055] Ethylene tar is added to the hard carbon material and stirred to obtain a mixed material of ethylene tar and the hard carbon material.

[0056] The ethylene tar and the hard carbon material are mixed more evenly by stirring, so that the density of the hard carbon negative electrode material obtained is more uniform. A low-speed mechanical stirring can be used for stirring, and the stirring speed can be adjusted according to the actual situation.

[0057] In the embodiment of the present disclosure, the D50 of the hard carbon material is in the range of 4 μm-10 μm, and the specific surface area is 3.0 g / m 2 -10.0g / m 2 In one embodiment, the D50 of the hard carbon material is in the range of 5 μm to 6.5 μm. In one embodiment, the specific surface area of ​​the hard carbon material is in the range of 5 g / m 2 -6g / m 2 D50 refers to the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%, and specific surface area (SSA) refers to the total surface area of ​​a solid per unit mass. D50 and SSA are used to characterize the hard carbon material's ability to adsorb and store active metal ions. Within the scope of this embodiment, the hard carbon material is able to more fully adsorb and store active metals, resulting in improved cycling performance for sodium-ion batteries.

[0058] In certain applications, a high ethylene tar mass ratio may fill the micropores of the hard carbon material, while a low ethylene tar mass ratio may affect its ability to fill macropores or mesopores. Therefore, the mass ratio of ethylene tar to hard carbon material can be adjusted experimentally in certain applications.

[0059] In an embodiment of the present disclosure, the mass ratio of ethylene tar to hard carbon material is 5:100-15:100. In one embodiment, the mass ratio of ethylene tar to hard carbon material is 7:100-9:100.

[0060] Within this range, ethylene tar can better fill the macropores or mesopores of hard carbon materials without changing the micropore structure, allowing the hard carbon negative electrode material to better exert its advantages, thereby making the sodium ion battery have better cycle performance.

[0061] In an embodiment of the present disclosure, the mixture of ethylene tar and hard carbon material is impregnated in an impregnation furnace, comprising:

[0062] placing a mixture of ethylene tar and hard carbon material in an impregnation furnace;

[0063] The impregnation furnace is evacuated and heated;

[0064] The heated impregnation furnace is pressurized for impregnation.

[0065] In this embodiment, the impregnation is to immerse the hard carbon material in ethylene tar so that the ethylene tar covers and fills the hard carbon material. Specifically, a mixture of ethylene tar and hard carbon material is placed in an impregnation furnace and impregnated by heating and pressurizing.

[0066] The vacuum heating increases the fluidity of the ethylene tar, allowing it to fully adhere to the hard carbon material. The pressurization can be performed in a protective gas environment, such as nitrogen or other inert gas, to allow the ethylene tar to enter the interior of the hard carbon particles.

[0067] In the disclosed embodiment, the heating temperature within the impregnation furnace ranges from 100°C to 300°C, the pressure ranges from 0.8 MPa to 2 MPa, and the impregnation time ranges from 2 hours to 6 hours. The heating temperature and pressure influence the filling and coating effect of the ethylene tar on the hard carbon material. In this embodiment, the above temperature and pressure ranges are not within the high temperature and high pressure ranges, yet the filling and coating effect of the ethylene tar on the hard carbon material is achieved.

[0068] In this embodiment, the above temperature, pressure, and time ranges are sufficient to achieve a better filling and coating effect of ethylene tar on the hard carbon material. In certain applications, the corresponding parameters can be adjusted within these ranges. In other embodiments, the effect may be compromised if the parameters are outside these ranges, but these ranges may be exceeded without affecting the feasibility of the solution.

[0069] In the disclosed embodiments, ethylene tar is carbonized to form soft carbon, which can then coat and fill the hard carbon material. The carbonized hard carbon material has more graphite regions, larger graphite flakes, and a smaller specific surface area, thereby improving the electrochemical performance of the hard carbon material.

[0070] In the embodiment of the present disclosure, the temperature range of the carbonization process is 900°C to 1200°C, the carbonization time is 3 hours to 6 hours, and the temperature range of the carbonization process is 1000°C to 1100°C.

[0071] Within this parameter range, the ethylene tar can be fully carbonized to become soft carbon. In other embodiments, if the parameter range is exceeded, the effect may be compromised, but it is also possible to exceed the parameter range without affecting the feasibility of the solution.

[0072] The embodiment of the present disclosure also provides a negative electrode material for a sodium ion battery. The negative electrode material is a hard carbon negative electrode material made using the negative electrode material of the embodiment shown in FIG. 1 .

[0073] The present disclosure also provides a negative electrode sheet for a sodium ion battery, the negative electrode sheet comprising:

[0074] The current collector and the negative electrode active material include the above-mentioned negative electrode material, a conductive agent and a binder.

[0075] The present disclosure also provides a sodium ion battery cell, which includes:

[0076] positive electrode;

[0077] The above-mentioned negative electrode sheet;

[0078] The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet.

[0079] The present disclosure also provides a sodium ion battery, comprising:

[0080] case;

[0081] The above-mentioned battery cell encapsulated in a shell;

[0082] Inject the electrolyte into the shell.

[0083] The present disclosure also provides the following experimental data to illustrate the beneficial effects of the solution of this embodiment.

[0084] Example 1:

[0085] Select particle size D50 = 5.0 μm, specific surface area = 6.0 g / m 2 The hard carbon material is prepared by mechanically stirring ethylene tar and hard carbon material in a mass ratio of 7:100 to obtain an ethylene tar-hard carbon mixture. The ethylene tar-hard carbon mixture is then impregnated in an impregnation furnace at 150°C and a pressure of 1.5 MPa for 3 hours to obtain an impregnated hard carbon material. Finally, the impregnated hard carbon material is carbonized at 1000°C for 5 hours to obtain a hard carbon material coated and filled with soft carbon. The hard carbon material coated and filled with soft carbon is mixed with SP (super PLL, i.e., conductive carbon black), CMC (Ceramic Matrix Composite, i.e., ceramic matrix composite), and SBR (Polymerized Styrene Butadiene Rubber, i.e., styrene-butadiene rubber) in a mass ratio of 94.0:3.0:1.0:2.0 to form a slurry. The negative electrode sheet is then produced through coating, drying, and roller pressing. The negative electrode sheet is then assembled into a soft-pack battery together with the positive electrode sheet, electrolyte, and other materials.

[0086] Example 2:

[0087] Compared with Example 1, the difference of Example 2 is that the particle size D50=6.5μm and the specific surface area=5.0g / m 2 For other steps and parameters, please refer to Example 1.

[0088] Example 3:

[0089] Compared with Example 1, the difference of Example 3 is that ethylene tar and hard carbon negative electrode material are mechanically stirred in a mass ratio of 9:100 to obtain ethylene tar-hard carbon mixed material. Other steps and parameters can refer to Example 1.

[0090] Example 4:

[0091] Compared with Example 1, the difference of Example 4 is that the impregnated hard carbon material is carbonized at 1100° C. for 5 h to obtain a hard carbon material coated and filled with soft carbon. Other steps and parameters can refer to Example 1.

[0092] Comparative Example

[0093] Preparation of precursor: Add 100 parts of enzymatically hydrolyzed lignin and 16 parts of tetraisocyanatosilane to 150 parts of benzene, stir until completely dissolved, heat to 80°C and maintain constant temperature, add 0.55 parts of triethylamine dropwise for 30 minutes, react under stirring for 5 hours, cool naturally to room temperature after the reaction, filter, wash with benzene three times to remove unreacted raw materials, dry in a vacuum at 80°C for 12 hours, grind to 0.3 mm, and set aside;

[0094] Precursor pretreatment: The precursor was milled in an XQM-0.5L planetary ball mill with φ = 10 mm agate balls and φ = 6 mm agate balls in a ratio of 1:4, for a total of 15 balls, at a speed of 300 r / min and a ball-to-material ratio of 7:1 for 26 h to obtain a ball-milled material with a particle size of 12 μm. The ball-milled material was then dispersed in 210 parts of a 5 wt% phytanic acid solution (solvent benzene) with an ultrasonic wave having a frequency of 80 kHz and a power of 400 W for 1 h. Benzene was removed by vacuum distillation, dried, and frozen. φ = 10 mm agate balls, φ = 6 mm agate balls, and φ = 4 mm agate balls in a ratio of 1:1:1, for a total of 15 balls, at a speed of 450 r / min and a ball-to-material ratio of 10:1, for 36 h to obtain a powder with a particle size of 2.7 μm, which was set aside.

[0095] Carbonization: The pretreated powder was added to a rotary carbonization furnace, purged with argon, and heated uniformly at 10°C / min to 1400°C and maintained at this temperature for 3 hours for carbonization. After carbonization, the powder was cooled to room temperature and ground to obtain a hard carbon powder with a particle size of 8 μm.

[0096] Chemical vapor deposition: The hard carbon powder obtained by carbonization is added to the reaction chamber, argon is introduced, and the temperature is uniformly raised to 1000°C at a rate of 5°C / min and maintained at a constant temperature. A mixed gas of argon and acetylene with a volume ratio of 2:1 is introduced, and the reaction is kept warm for 2 hours. After the insulation is completed, argon is introduced and the temperature is cooled to room temperature at a rate of 8°C / min to obtain a surface-coated hard carbon material.

[0097] The experimental results are shown in the following table:

[0098] As can be seen from the above table, compared with the comparative example, the particle size and specific surface area of ​​the final hard carbon negative electrode material in each embodiment are relatively smaller, and the compaction density, first efficiency and cycle performance are all improved.

[0099] Therefore, this embodiment uses ethylene tar as a filler and coating agent with high economic value. Secondly, ethylene tar has good fluidity and a certain viscosity at room temperature, and can penetrate well into the mesopores and macropores in the hard carbon particles, and adhere to the surface of the hard carbon to improve its surface defects. The operation process is simple and efficient and does not affect the microporous structure of the hard carbon material; finally, the volatile matter of ethylene tar is relatively low and the residual carbon rate is high. During the heat treatment process, it is not easy to form a large number of pores due to the volatilization of impurities. The prepared hard carbon material coated and filled with soft carbon has high first efficiency, high compaction density, and excellent cycle stability.

[0100] The above embodiments are merely illustrative of the principles and effects of this disclosure and are not intended to limit this disclosure. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this disclosure. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein shall be covered by the claims of this disclosure.

[0101] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for preparing a negative electrode material for a sodium ion battery, include: mixing ethylene tar with a hard carbon material; The mixed material of the ethylene tar and the hard carbon material is impregnated in an impregnation furnace; The impregnated hard carbon material is carbonized to obtain a hard carbon negative electrode material.

2. The method for preparing a negative electrode material for a sodium ion battery according to claim 1, in, The D50 of the hard carbon material is in the range of 4 μm-10 μm, and the specific surface area is 3 g / m 2 -10g / m 2 .

3. The method for preparing the negative electrode material for sodium ion battery according to claim 2, in, The D50 of the hard carbon material is in the range of 5 μm to 6.5 μm.

4. The method for preparing a negative electrode material for a sodium ion battery according to claim 2 or 3, in, The specific surface area of ​​the hard carbon material is 5 g / m 2 -6g / m 2 .

5. The method for preparing the negative electrode material for sodium ion battery according to any one of claims 1 to 4, in, The mass ratio of the ethylene tar to the hard carbon material is 5:100-15:

100.

6. The method for preparing a negative electrode material for a sodium ion battery according to claim 5, in, The mass ratio of the ethylene tar to the hard carbon material is 7:100-9:

100.

7. The method for preparing a negative electrode material for a sodium ion battery according to any one of claims 1 to 6, in, The step of impregnating the mixed material of the ethylene tar and the hard carbon material in an impregnation furnace comprises: placing the mixed material of the ethylene tar and the hard carbon material in the impregnation furnace; The impregnation furnace is evacuated and heated; The heated impregnation furnace is subjected to pressure impregnation.

8. The method for preparing a negative electrode material for a sodium ion battery according to claim 7, in, The heating temperature in the impregnation furnace ranges from 100° C. to 300° C., the pressure is from 0.8 MPa to 2 MPa, and the impregnation time is from 2 h to 6 h.

9. The method for preparing a negative electrode material for a sodium ion battery according to claim 7 or 8, in, The temperature range of the carbonization process is 900° C. to 1200° C., and the carbonization time is 3 to 6 hours.

10. The method for preparing a negative electrode material for a sodium ion battery according to claim 9, in, The temperature range of the carbonization process is 1000°C to 1100°C.

11. The method for preparing a negative electrode material for a sodium ion battery according to any one of claims 1 to 10, in, The step of mixing ethylene tar with a hard carbon material comprises: The ethylene tar is added to the hard carbon material and stirred to obtain a mixed material of the ethylene tar and the hard carbon material.

12. A negative electrode material for a sodium ion battery, include: A hard carbon negative electrode material prepared using the method for preparing a negative electrode material for a sodium ion battery as described in any one of claims 1 to 11.

13. A negative electrode sheet for a sodium ion battery, include: A current collector and a negative electrode active material, wherein the negative electrode active material comprises the negative electrode material for a sodium ion battery according to claim 12, a conductive agent and a binder.

14. A sodium ion battery cell, include: Positive electrode; The negative electrode sheet for a sodium ion battery as claimed in claim 13; The separator is arranged between the positive electrode sheet and the negative electrode sheet.

15. A sodium ion battery, include: case; The battery cell as claimed in claim 14 encapsulated in a housing; An electrolyte is injected into the housing.

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