A positive electrode and a sodium-ion battery

Abstract

This invention provides a positive electrode sheet and a sodium-ion battery. A first aspect of this invention provides a positive electrode sheet comprising a positive current collector and a positive active material layer disposed on the surface of the current collector. The positive active material layer includes a sodium replenishing agent, which comprises sodium borohydride and a carbon layer coated on the surface of the sodium borohydride. The sodium replenishing agent provided by this invention has a core-shell structure, with sodium borohydride as the core. During charging, it can irreversibly decompose and release sodium, achieving a sodium replenishment effect and improving the initial coulombic efficiency and energy density of the sodium-ion battery. Furthermore, due to the poor conductivity and stability of sodium borohydride in air, this invention coats the surface of sodium borohydride with a carbon layer, effectively improving the conductivity and stability of sodium borohydride and enhancing its sodium replenishment effect.

Description

Technical Field

[0001] This invention relates to a positive electrode and a sodium-ion battery, and relates to the field of sodium-ion battery technology. Background Technology

[0002] Lithium-ion batteries, as energy storage devices with high energy density and long lifespan, have been widely used in electronic devices such as mobile phones and laptops. However, lithium resources are limited and expensive, making it difficult for lithium-ion batteries to meet the growing demands of mobile electronics and the automotive industry. Compared to lithium, sodium is more abundant, which can significantly reduce battery costs, making sodium-ion batteries a promising candidate for widespread application.

[0003] Because sodium and lithium have similar electrochemical properties, during the first charge-discharge cycle of a sodium-ion battery, some sodium ions react on the negative electrode surface to form a solid electrolyte interphase (SEI), resulting in irreversible sodium loss. This reduces the initial coulombic efficiency and energy density of the sodium-ion battery. By adding a sodium replenishing agent to the positive electrode active material layer, the sodium ion loss during the first cycle can be compensated, thereby improving the initial coulombic efficiency and energy density of the sodium-ion battery. Therefore, developing an effective sodium replenishing agent to compensate for this sodium ion loss is a hot topic of ongoing interest to those skilled in the art. Summary of the Invention

[0004] This invention provides a positive electrode and a sodium-ion battery, which includes a sodium supplement to improve the initial coulombic efficiency and energy density of the sodium-ion battery.

[0005] The first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on the surface of the positive current collector, the positive active material layer comprising a sodium supplementing agent, the sodium supplementing agent comprising sodium borohydride and a carbon layer coated on the surface of the sodium borohydride;

[0006] The sodium borohydride has a particle size of 0.5–6 μm, and the carbon layer has a thickness of 10–100 nm.

[0007] The sodium supplement agent for the positive electrode sheet described above is prepared by the following method:

[0008] Trimethyl borate was prepared by reacting boric acid with methanol, and sodium hydride was prepared by reacting metallic sodium with hydrogen.

[0009] Sodium borohydride was prepared by reacting the trimethyl borate with sodium hydride.

[0010] The sodium supplement is obtained by heat-treating the sodium borohydride with a gaseous carbon source.

[0011] The positive electrode sheet described above is prepared by reacting metallic sodium with hydrogen gas to obtain sodium hydride, specifically including:

[0012] Sodium hydride is prepared by dispersing metallic sodium in an oily medium, introducing hydrogen gas into the oily medium, and reacting at 200–500°C for 4–12 hours.

[0013] The sodium supplement agent is obtained by heat-treating the sodium borohydride with a gaseous carbon source as described above, specifically including:

[0014] Under an inert atmosphere, the sodium borohydride is dispersed in an oily medium, and a gaseous carbon source is introduced to deposit elemental carbon on the surface of the sodium borohydride to form a carbon layer, thereby obtaining the sodium supplement.

[0015] As described above, the gaseous carbon source includes one or more of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.

[0016] In the positive electrode as described above, the molar ratio of sodium borohydride to the gaseous carbon source is 50 to 200:1.

[0017] As described above, the heat treatment temperature of the sodium borohydride and gaseous carbon source is 250–280°C, and the time is 2–12 h.

[0018] As described above, the positive electrode sheet further includes a positive electrode active material layer, a conductive agent, and a binder, wherein the mass of the sodium supplement is 5-20% of the total mass of the positive electrode active material, the conductive agent, and the binder.

[0019] As described above, the mass ratio of the positive electrode active material, conductive agent, and binder is 8-9:1:1.

[0020] A second aspect of the present invention provides a sodium-ion battery, the sodium-ion battery comprising any of the positive electrode sheets described above.

[0021] The implementation of this invention has at least the following advantages:

[0022] 1. The positive electrode sheet provided by this invention includes a sodium replenishing agent with a core-shell structure, and uses sodium borohydride as the core. During the charging process of sodium-ion batteries, it can irreversibly decompose and release sodium ions to achieve a sodium replenishment effect, thereby improving the specific capacity and coulombic efficiency of sodium-ion batteries. In addition, since sodium borohydride has poor conductivity and stability in air, this invention coats the surface of sodium borohydride with a carbon layer, which effectively improves the conductivity and stability of sodium borohydride and enhances the sodium replenishment effect of sodium borohydride.

[0023] 2. By limiting the particle size of sodium borohydride and the thickness of the carbon coating layer, this invention helps to further improve the sodium replenishment effect of sodium borohydride, thereby increasing the specific capacity and coulombic efficiency of sodium-ion batteries.

[0024] 3. The sodium supplement provided by this invention has a simple preparation method, readily available raw materials, low pollution, and simple post-processing. It is compatible with the existing sodium-ion battery manufacturing process and is conducive to large-scale production and application.

[0025] 4. The sodium-ion battery provided by the present invention includes the above-mentioned sodium replenishing agent, which can effectively improve the specific capacity and coulombic efficiency of the sodium-ion battery. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of a sodium supplement provided in an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Positive current collector;

[0031] 2- Positive electrode active material layer;

[0032] Sodium 31-borohydride;

[0033] 32-Carbon layer. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] Figure 1 This is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the positive electrode includes a positive current collector 1 and a positive active material layer 2 disposed on the surface of the positive current collector. It can be understood that... Figure 1The positive electrode current collector has positive electrode active material layers on both its upper and lower surfaces. In addition, the positive electrode active material layers can also be disposed separately on the upper or lower surface of the positive electrode current collector. This invention does not limit this and can be done according to conventional technical means in the field.

[0036] The positive electrode current collector 1 refers to the base metal in the positive electrode of the battery used to attach active materials, such as conventional materials like aluminum foil.

[0037] The positive electrode active material layer 2 includes a sodium supplement. Figure 2 This is a schematic diagram of the structure of a sodium supplement provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the sodium supplement includes sodium borohydride 31 and a carbon layer 32 coated on the surface of the sodium borohydride. The inventors of this application have discovered that sodium borohydride has the ability to transport sodium ions and dissociate sodium ions, and therefore use it as a sodium supplement. In order to improve the conductivity and stability of sodium borohydride, carbon elemental in an extremely fine powder state is deposited on the surface of sodium borohydride 31 by van der Waals forces to form a coated carbon layer 32.

[0038] Specifically, the particle size of sodium borohydride is 0.5–6 μm. Particle size refers to the size of sodium borohydride particles, which can be obtained by particle size analyzer.

[0039] The thickness of carbon layer 32 is 10–100 nm. The thickness of carbon layer 32 refers to the distance between the outermost layer of carbon layer 32 and the surface of sodium borohydride 31. This distance ranges from 10 to 100 nm. Carbon layer 32 and its thickness can be determined by various methods such as SEM, EDS, TEM, and XPS.

[0040] In one specific embodiment, the sodium supplement is prepared by the following method:

[0041] Step 1: Trimethyl borate is prepared by reacting boric acid with methanol, and sodium hydride is prepared by reacting metallic sodium with hydrogen.

[0042] First, trimethyl borate was prepared by reacting boric acid and methanol as raw materials. The reaction formula involved is: B(OH)3+3CH3OH=B(OCH3)3+3H2O. The molar ratio of boric acid to methanol is 1:3, the reaction temperature is 25~100℃, and the reaction time is 1~2h.

[0043] Simultaneously, sodium hydride is prepared by reacting sodium metal and hydrogen gas as raw materials. Because sodium metal is highly reactive and readily reacts with air and water, this invention disperses sodium metal in an oily medium and introduces hydrogen gas into the oily medium. Specifically, the molar ratio of sodium metal to hydrogen gas is 1:1, the reaction temperature is 200–500°C, and the reaction time is 4–12 hours to prepare sodium hydride.

[0044] Furthermore, the oily medium is paraffin oil.

[0045] Step 2: Prepare sodium borohydride by reacting the trimethyl borate with sodium hydride;

[0046] Next, trimethyl borate and sodium hydride prepared in step 1 were used as raw materials for reaction. The molar ratio of trimethyl borate to sodium hydride was 1:4, the reaction temperature was 200-400℃, and the reaction time was 2-12h. After the reaction was completed, the solid product was collected to obtain sodium borohydride.

[0047] The prepared sodium borohydride was crushed, and its particle size was controlled to be 0.5–6 μm.

[0048] Step 3: Heat-treat the sodium borohydride with a gaseous carbon source to obtain the sodium supplement.

[0049] Using sodium borohydride obtained in step 2 as raw material, the sodium borohydride is dispersed in an oily medium under an inert atmosphere, and a gaseous carbon source is introduced to carry out the reaction. After the reaction is completed, the sodium supplement is prepared.

[0050] Furthermore, the gaseous carbon source includes one or more of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.

[0051] Furthermore, the molar ratio of sodium borohydride to the gaseous carbon source is 50 to 200:1.

[0052] Furthermore, the heat treatment temperature of the sodium borohydride and the gaseous carbon source is 250-280°C for 2-12 hours, so that carbon elements are deposited on the surface of the sodium borohydride to form a coating layer.

[0053] It is understood that, in addition to the sodium replenishing agent, the positive electrode active material layer 2 also includes the positive electrode active material, the conductive agent, and the binder, wherein the mass of the sodium replenishing agent is 5 to 20% of the total mass of the positive electrode active material, the conductive agent, and the binder.

[0054] Furthermore, the mass ratio of the positive electrode active material, conductive agent, and binder is 8-9:1:1.

[0055] The selection of the positive electrode active material, conductive agent, and binder is not special and can be conventional in the field. For example, the positive electrode active material can be a sodium-containing layered oxide material, Prussian white material, sodium-containing polyanionic material, etc.; for example, the positive electrode active material can be nickel-containing NaNi. 0.3 Fe 0.25 Mn 0.45 O2, copper-containing NaCu 0.20 Fe 0.40 Mn 0.40O2, polyanionic NaV2(PO4)3 or one or more; the conductive agent is selected from one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, single-walled carbon nanotube, multi-arm carbon nanotube, and carbon fiber; the binder is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and lithium polyacrylate (PAALi).

[0056] During the preparation process, the positive electrode active material, sodium supplement, conductive agent and binder are dispersed in a solvent and stirred evenly to obtain a positive electrode slurry; then, the positive electrode slurry is uniformly coated on the positive electrode current collector 1 to obtain a positive electrode active material layer 2, which is dried and cut to obtain a positive electrode sheet.

[0057] A second aspect of the present invention provides a sodium-ion battery comprising any of the above-described positive electrode plates.

[0058] Based on the positive electrode sheet provided by the present invention, sodium-ion batteries including the positive electrode sheet have good specific capacity and coulombic efficiency.

[0059] It is understood that the sodium-ion battery provided by the present invention also includes a negative electrode, a separator, and an electrolyte, all of which are conventional choices in the art.

[0060] The sodium supplement, positive electrode sheet, and sodium-ion battery provided by the present invention will be described below with reference to specific embodiments.

[0061] Example 1

[0062] This embodiment provides a method for preparing a sodium supplement, which specifically includes the following steps:

[0063] Step 1: Add boric acid and methanol to a reaction vessel at a molar ratio of 1:3, heat to 80°C and react for 2 hours to prepare trimethyl borate;

[0064] Step 2: Disperse metallic sodium in paraffin oil, heat to 300°C, introduce hydrogen gas at a molar ratio of metallic sodium to hydrogen gas of 1:1, and react at 400°C for 6 hours to prepare sodium hydride.

[0065] Step 3: Mix trimethyl borate and sodium hydride at a molar ratio of 1:4 and react at 350°C for 5 hours to obtain sodium borohydride.

[0066] Step 4: Place sodium borohydride in a mortar and grind for 20 minutes to obtain sodium borohydride with a particle size of 3.79 μm;

[0067] Step 5: Place trimethyl borate and sodium hydride in paraffin oil, continuously pass nitrogen gas as a protective gas, heat to 250°C, and then pass methane under nitrogen protection to react for 2 hours to obtain sodium supplement NaBH4@C with a carbon layer thickness of 16 nm.

[0068] Example 2

[0069] The preparation method of the sodium supplement provided in this embodiment can be referred to in Embodiment 1. The difference is that in step 3, the reaction time of introducing methane is 5 hours and the carbon layer thickness is 43 nm.

[0070] Example 3

[0071] The preparation method of the sodium supplement provided in this embodiment can be referred to in Embodiment 1. The difference is that in step 3, the reaction time of introducing methane is 8 hours and the carbon layer thickness is 68 nm.

[0072] Example 4

[0073] The preparation method of the sodium supplement provided in this embodiment can be referred to in Embodiment 1. The difference is that in step 3, the reaction time of introducing methane is 11 hours and the carbon layer thickness is 95 nm.

[0074] Example 5

[0075] The preparation method of the sodium supplement provided in this embodiment can be referred to in Embodiment 1. The difference is that in step 3, the carbon source is replaced by ethylene instead of methane, and the carbon layer thickness is 21 nm.

[0076] Example 6

[0077] The preparation method of the sodium supplement provided in this embodiment can be referred to in Embodiment 1. The difference is that in step 3, the carbon source is replaced by acetylene instead of methane, and the carbon layer thickness is 19 nm.

[0078] Comparative Example 1

[0079] The preparation method of the sodium supplement provided in this comparative example can be referred to Example 1, except that in step 3, the reaction time of introducing methane is 20h and the carbon layer thickness is 200nm.

[0080] Comparative Example 2

[0081] The preparation method of the sodium supplement provided in this comparative example can be referred to Example 1, except that the particle size of sodium borohydride is 8.06 μm.

[0082] Example 7

[0083] This embodiment provides a positive electrode sheet, comprising a positive current collector aluminum foil and a positive active material layer disposed on the surface of the positive current collector aluminum foil, wherein the positive active material layer comprises 8 parts by mass of positive active material (NaNi). 0.3 Fe 0.25 Mn 0.45 O2), 1 part by weight of the sodium supplement provided in Example 1, 1 part by weight of the conductive agent acetylene black, and 1 part by weight of polyvinylidene fluoride (PVDF).

[0084] Positive electrode active material (NaNi) 0.3 Fe 0.25 Mn 0.45 Methods for preparing O2 include:

[0085] Step 1: Mix the precursor and lithium hydroxide evenly in a plow mixer, and then sinter at 900℃ for 20 hours;

[0086] Step 2: After the material is sintered once, it is crushed, sieved, washed, dried, and then transferred to a rotary kiln for sintering at 600℃ for 16 hours.

[0087] Step 3: The material after secondary sintering is sieved and iron is removed to obtain polycrystalline ternary cathode active material (NaNi). 0.3 Fe 0.25 Mn 0.45 O2).

[0088] The preparation methods of the positive electrode sheet include:

[0089] Step 1: Disperse the positive electrode active material, sodium supplement, acetylene black and polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) solution and stir evenly to obtain positive electrode slurry;

[0090] Step 2: Coat the positive electrode slurry evenly on the aluminum foil, dry it in a vacuum drying oven for 24 hours, and then cut it to obtain the positive electrode sheet.

[0091] Example 8

[0092] The positive electrode sheet provided in this embodiment can be referred to in Embodiment 7, except that the positive electrode active material layer includes the sodium supplement agent provided in Embodiment 2.

[0093] Example 9

[0094] The positive electrode sheet provided in this embodiment can be referred to in Embodiment 7, except that the positive electrode active material layer includes the sodium supplement agent provided in Embodiment 3.

[0095] Example 10

[0096] The positive electrode sheet provided in this embodiment can be referred to in Embodiment 7, except that the positive electrode active material layer includes the sodium supplement agent provided in Embodiment 4.

[0097] Example 11

[0098] The positive electrode sheet provided in this embodiment can be referred to in Embodiment 7, except that the positive electrode active material layer includes the sodium supplement agent provided in Embodiment 5.

[0099] Example 12

[0100] The positive electrode sheet provided in this embodiment can be referred to in Embodiment 7, except that the positive electrode active material layer includes the sodium supplement agent provided in Embodiment 6.

[0101] Comparative Example 3

[0102] The positive electrode provided in this comparative example can be referred to in Example 7, except that the positive electrode does not include a sodium supplement.

[0103] Comparative Example 4

[0104] The positive electrode sheet provided in this comparative example can be referred to in Example 7, except that the sodium supplement is sodium borohydride without a carbon layer coating.

[0105] Methods for preparing sodium borohydride without a carbon layer coating include:

[0106] Step 1: Add boric acid and methanol to a reaction vessel at a molar ratio of 1:3, heat to 80°C and react for 2 hours to prepare trimethyl borate;

[0107] Step 2: Disperse metallic sodium in paraffin oil, heat to 300°C, introduce hydrogen gas at a molar ratio of metallic sodium to hydrogen gas of 1:1, and react at 400°C for 6 hours to prepare sodium hydride.

[0108] Step 3: Mix trimethyl borate and sodium hydride at a molar ratio of 1:4 and react at 350°C for 5 hours to obtain sodium borohydride.

[0109] Comparative Example 5

[0110] The positive electrode sheet provided in this comparative example can be referred to in Example 7, except that the positive electrode active material layer includes the sodium supplement provided in Comparative Example 1.

[0111] Comparative Example 6

[0112] The positive electrode sheet provided in this comparative example can be referred to in Example 7, except that the positive electrode active material layer includes the sodium supplement provided in Comparative Example 2.

[0113] Comparative Example 7

[0114] The positive electrode sheet provided in this comparative example can be referred to in Example 7, except that the sodium supplement is Na2O.

[0115] The positive electrode sheets and hard carbon negative electrodes provided in Examples 7-12 and Comparative Examples 3-7 were placed on both sides of a separator, and an appropriate amount of sodium-ion battery electrolyte (solute is sodium hexafluorophosphate, solvent is ethylene carbonate (EC) and dimethyl carbonate (DMC), with a volume ratio of EC:DMC = 1:1) was added to assemble a pouch battery. The discharge specific capacity and initial coulombic efficiency of the battery were then tested using the following methods, and the test results are shown in Table 1.

[0116] Test methods for discharge specific capacity and initial coulombic efficiency: At 25℃, charge and discharge performance tests are conducted at 1.5~4.2V with 0.1C charging / 0.1C discharging. The initial coulombic efficiency is then calculated according to the formula: Initial discharge efficiency = Initial discharge specific capacity / Initial charge specific capacity * 100%.

[0117] Table 1 shows the performance test results of the batteries provided in Examples 7-12 and Comparative Examples 3-7.

[0118] Discharge specific capacity (mAh / g) First-time coulomb efficiency (%) Example 7 117.7 86.2％ Example 8 120.3 87.3％ Example 9 121.9 88.6％ Example 10 119.6 87.1％ Example 11 118.2 85.9％ Example 12 117.0 86.0％ Comparative Example 3 105.9 75.6％ Comparative Example 4 111.3 81.4％ Comparative Example 5 112.7 81.9％ Comparative Example 6 114.1 82.6％ Comparative Example 7 108.9 79.5％

[0119] According to the data provided in Comparative Example 3, adding sodium supplementation agent to the positive electrode helps improve the battery's discharge specific capacity and initial coulombic efficiency. According to Comparative Example 4, coating the surface of sodium borohydride with a carbon layer helps improve the discharge specific capacity and initial coulombic efficiency of sodium-ion batteries. According to the data provided in Comparative Examples 5 and 6, controlling the particle size of sodium borohydride and the thickness of the carbon coating layer helps further improve the discharge specific capacity and initial coulombic efficiency of sodium-ion batteries. According to Comparative Example 7, the sodium supplementation effect of sodium borohydride is better than that of N-ion batteries. According to Examples 7-10, as the gaseous carbon source introduction time increases, the carbon layer thickness continuously increases, but the discharge specific capacity and initial coulombic efficiency of the sodium-ion battery first increase and then decrease. Therefore, controlling the gaseous carbon source introduction time to 5-8 hours and the carbon layer thickness to 40-70 nm helps to further improve the discharge specific capacity and initial coulombic efficiency of the sodium-ion battery. According to Examples 11-12, the type of gaseous carbon source has little impact on the performance of the sodium-ion battery, which is beneficial for large-scale production and application.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer includes a sodium supplement agent, which includes sodium borohydride and a carbon layer coated on the surface of the sodium borohydride. The sodium borohydride has a particle size of 0.5–6 μm, and the carbon layer has a thickness of 10–100 nm.

2. The positive electrode sheet according to claim 1, characterized in that, The sodium supplement is prepared by the following method: Trimethyl borate was prepared by reacting boric acid with methanol, and sodium hydride was prepared by reacting metallic sodium with hydrogen. Sodium borohydride was prepared by reacting the trimethyl borate with sodium hydride. The sodium supplement is obtained by heat-treating the sodium borohydride with a gaseous carbon source.

3. The positive electrode sheet according to claim 2, characterized in that, Sodium hydride is prepared by reacting metallic sodium with hydrogen gas, specifically including: Sodium hydride is prepared by dispersing metallic sodium in an oily medium, introducing hydrogen gas into the oily medium, and reacting at 200–500°C for 4–12 hours.

4. The positive electrode sheet according to claim 2, characterized in that, The sodium supplement agent is obtained by heat-treating the sodium borohydride with a gaseous carbon source, specifically comprising: Under an inert atmosphere, the sodium borohydride is dispersed in an oily medium, and a gaseous carbon source is introduced to deposit elemental carbon on the surface of the sodium borohydride to form a carbon layer, thereby obtaining the sodium supplement.

5. The positive electrode sheet according to claim 2 or 4, characterized in that, The gaseous carbon source includes one or more of methane, ethane, propane, ethylene, propylene, acetylene, and propyne.

6. The positive electrode sheet according to claim 2 or 4, characterized in that, The molar ratio of sodium borohydride to the gaseous carbon source is 50 to 200:

1.

7. The positive electrode sheet according to claim 2 or 4, characterized in that, The heat treatment of sodium borohydride with gaseous carbon source is carried out at a temperature of 250–280°C for 2–12 hours.

8. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active material layer also includes a positive electrode active material, a conductive agent, and a binder, and the mass of the sodium supplement agent is 5-20% of the total mass of the positive electrode active material, the conductive agent, and the binder.

9. The positive electrode sheet according to claim 8, characterized in that, The mass ratio of the positive electrode active material, conductive agent, and binder is 8-9:1:

1.

10. A sodium-ion battery, characterized in that, The sodium-ion battery includes the positive electrode sheet as described in any one of claims 1 to 9.

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