Sodium-ion battery positive electrode slurry, preparation method thereof and sodium-ion battery

Abstract

The invention relates to sodium ion battery positive electrode slurry, a preparation method thereof and a sodium ion battery. The preparation method comprises the following steps: mixing a sodium supplementing agent and a first solvent to obtain a sodium supplementing agent solution; mixing the sodium supplementing agent solution and the positive electrode main material to obtain sodium ion battery positive electrode slurry; the sodium supplementing agent comprises benzene sodium salt; the first solvent comprises an alcohol solvent and a dispersing agent. According to the preparation method, the adopted alcohol solvent can increase the solubility of the organic sodium salt, and the dispersing agent can prevent agglomeration of the sodium supplementing agent, so that the sodium supplementing agent can be better dispersed. According to the preparation method, a special process is not needed, and the preparation method can be realized by stirring a kettle at normal temperature in a positive electrode slurry mixing workshop. The processes of extra pulping and coating of sodium benzene salt are avoided, and the preparation process is simplified. The sodium ion battery provided by the invention has high first efficiency and long cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery positive electrode slurry and a preparation method thereof, and a sodium ion battery. Background Art

[0002] Sodium-ion batteries have experienced rapid development due to their low cost. However, similar to lithium-ion batteries, they also suffer from the problem of active sodium loss in the system due to irreversible reactions such as the formation of the SEI film on the negative electrode surface. This directly leads to a decrease in the energy density of the entire battery, seriously hindering the commercialization of sodium-ion batteries. Therefore, replenishing sodium ions in the sodium-ion battery system is of great significance for improving the energy density of sodium-ion batteries and promoting their commercialization.

[0003] Currently, the low energy density of sodium-ion batteries is one of the main obstacles to their industrialization. For sodium-ion battery systems, all sodium ions used for electrochemical reactions come from the positive electrode. Any loss of sodium ions will directly lead to a decrease in the energy density of the entire battery. When a sodium-ion battery is first charged, the sodium ions released from the positive electrode will form an SEI film on the surface of the negative electrode or undergo other side reactions, resulting in a loss of active sodium. As a result, the same amount of sodium ions will not be released from the negative electrode and return to the positive electrode during discharge, thereby reducing the initial coulombic efficiency of the sodium-ion battery and affecting its energy density.

[0004] In order to improve the energy density, first coulombic efficiency and cycle stability of sodium-ion batteries, researchers generally use pre-sodiumization technology, such as adding positive electrode sodium supplements to the positive electrode materials, to promote the commercial application of sodium-ion batteries. In the existing technology, positive electrode sodium supplements are mainly inorganic substances, including Na2CO3, NaN3, Na3P, etc. However, these positive electrode sodium supplements have the following problems: (1) Na2CO3 is a strong alkaline substance, which will destroy the structure of the binder PVDF, resulting in a decrease in the electrode peeling force, reducing the performance of the battery cell, and increasing the risk of gelation of the positive electrode slurry, and ultimately making it impossible to coat; (2) NaN3 and Na3P are not only expensive, but also extremely unstable in the air, which makes the product manufacturability worse and the cost higher; (3) There is generally residual alkali in sodium-ion positive electrode materials. These alkaline sodium supplements not only cannot neutralize the residual alkali in the positive electrode materials, but may even further introduce residual alkali, exacerbating the risk of gelation of the positive electrode slurry.

[0005] As a new type of sodium supplement, sodium phenolate has great advantages over the current inorganic positive electrode sodium supplement materials such as Na2C2O4, NaCrO2 and Na2CO3 in terms of material synthesis, sodium removal residue and sodium removal voltage. After the first activation, in addition to releasing sodium ions, it can also release carbon and oxygen functional groups to act on the surface defects of the negative electrode to form carbon-oxygen double bonds. The reduction of negative electrode defects is conducive to improving the first effect. At the same time, the carbon and oxygen double bonds can also react with Na + The reaction increases the negative electrode's Na + At the same time, the residue after sodium removal will further stabilize the positive electrode and improve the stability of the battery in subsequent cycles.

[0006] However, since these materials are organic salts, if they are directly added to the positive electrode slurry, they are immiscible because the positive electrode slurry solution is generally NMP (N-methylpyrrolidone), an organic solvent. The sodium supplement is usually applied after the positive electrode is coated, which is equivalent to a double-layer coating. The process is cumbersome, time-consuming, and labor-intensive, and the resulting positive electrode sheet has poor stability.

[0007] Therefore, based on the problems existing in the preparation process of the above-mentioned sodium supplement and positive electrode slurry, how to provide a method that can achieve the blending of sodium phenolate organic sodium supplement and positive electrode slurry to simplify the preparation process of positive electrode slurry and electrode has become a problem that needs to be solved urgently. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention aims to provide a sodium ion battery positive electrode slurry, a preparation method thereof, and a sodium ion battery. The sodium ion battery positive electrode slurry of the present invention directly prepares a sodium supplement agent into a solution and uniformly mixes it with the positive electrode slurry, and applies them together, thereby reducing the process of applying the sodium supplement agent solution twice.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a positive electrode slurry for a sodium ion battery, the preparation method comprising the following steps:

[0011] A sodium supplementing agent and a first solvent are mixed to obtain a sodium supplementing agent solution; the sodium supplementing agent solution and a positive electrode main material are mixed to obtain a sodium ion battery positive electrode slurry; the sodium supplementing agent includes sodium benzene salt; and the first solvent includes an alcohol solvent and a dispersant.

[0012] The present invention first dissolves a sodium supplement agent, benzene sodium salt, in a first solvent to obtain a sodium supplement agent solution, then adds a positive electrode main material thereto, and mixes them evenly to obtain a positive electrode slurry. In the preparation method of the present invention, the alcohol solvent used can increase the solubility of the organic sodium salt, and the dispersant can prevent the sodium supplement agent from agglomerating, thereby better dispersing it.

[0013] The benzene sodium salt sodium supplement in the present invention can be directly blended with the positive electrode material. The preparation method does not require special processes and can be achieved in a stirring kettle at room temperature in a positive electrode slurry workshop. The preparation method is simpler and overcomes the process defects of the prior art that the benzene sodium salt sodium supplement needs to be slurried separately and coated twice.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] Preferably, the sodium benzene salt comprises any one of sodium o-dihydroxybenzene, sodium m-dihydroxybenzene, sodium p-dihydroxybenzene or sodium trihydroxybenzene, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sodium o-dihydroxybenzene and sodium m-dihydroxybenzene, a combination of sodium m-dihydroxybenzene and sodium p-dihydroxybenzene, a combination of sodium p-dihydroxybenzene and sodium trihydroxybenzene, a combination of sodium o-dihydroxybenzene, sodium p-dihydroxybenzene and sodium trihydroxybenzene, a combination of sodium m-dihydroxybenzene, sodium p-dihydroxybenzene and sodium trihydroxybenzene, or a combination of sodium o-dihydroxybenzene, sodium m-dihydroxybenzene, sodium p-dihydroxybenzene and sodium trihydroxybenzene, preferably sodium o-dihydroxybenzene.

[0016] Preferably, the first solvent further comprises a second solvent.

[0017] Preferably, the mass ratio of the second solvent, the alcohol solvent and the dispersant in the first solvent is 1:(0.005-0.01):(0.002-0.005), for example, it can be 1:0.005:0.002, 1:0.005:0.004, 1:0.005:0.005, 1:0.006:0.002, 1:0.006:0.003, 1:0.006:0.004, 1:0.006:0.005, 1:0.007:0.002, 1:0.007:0.003, 1:0.007:0.004, 1:0.007:0.005, 1:0.008:0.0 02, 1:0.008:0.003, 1:0.008:0.004, 1:0.008:0.005, 1:0.009:0.002, 1:0.009:0.003, 1:0.009:0.004, 1:0.009:0.005, 1:0.01:0.002, 1:0.01:0.003, 1:0.01:0.004, 1:0.01:0.005 or 1:0.005:0.003, but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable, preferably 1:(0.005-0.007):(0.002-0.003).

[0018] The present invention further controls the mass ratio of the second solvent, the alcohol solvent, and the dispersant to be 1:(0.005-0.01):(0.002-0.005), and the mass ratios of the components of the first solvent cooperate with each other, so that the sodium benzene salt sodium supplement can be completely dissolved and the uniformity of the sodium supplement solution is maintained, creating conditions for the subsequent addition of the positive electrode main material. If the content of the alcohol solvent is too high, the excessive alcohol substance has a certain impact on the electrical performance; if the content of the alcohol solvent is too low, the sodium supplement solvent is insufficient (the main reason is that the solution of the sodium supplement is mainly decomposed into sodium ions and phenolate ions, and too low an alcohol content will cause the solution polarity to be insufficient and unable to dissolve); if the content of the dispersant is too low, the phenolate ions and sodium ions cannot be evenly dispersed in the solution; if the content of the dispersant is too high, unnecessary waste will result.

[0019] Preferably, the second solvent comprises any one or a combination of at least two of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), water, ethanol or toluene, typical but non-limiting combinations include a combination of NMP and DMF, a combination of water and ethanol, a combination of ethanol and toluene, a combination of NMP, water and ethanol, a combination of NMP, DMF, water and toluene, a combination of NMP, DMF and toluene, and a combination of NMP, DMF, water, ethanol and toluene.

[0020] Preferably, the alcohol solvent includes isopropyl alcohol and / or butanediol, preferably isopropyl alcohol.

[0021] Preferably, the dispersant comprises any one of polyvinyl pyrrolidone (PVP), polyamide, polyimide, polyurethane or polyacrylate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of polyvinyl pyrrolidone and polyamide, a combination of polyamide and polyimide, a combination of polyurethane and polyacrylate, a combination of polyvinyl pyrrolidone, polyamide, polyimide and polyurethane, a combination of polyvinyl pyrrolidone, polyurethane and polyacrylate, a combination of polyamide, polyimide, polyurethane and polyacrylate, or a combination of polyvinyl pyrrolidone, polyamide, polyimide, polyurethane and polyacrylate.

[0022] Preferably, the mass concentration of the sodium supplement solution is 0.1wt%-1.5wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt% or 1.5wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. Preferably, it is 1.4wt%-1.5wt%.

[0023] The present invention further controls the mass concentration of the sodium supplement solution to be 0.1wt%-1.5wt%. Within this range, the cycle performance of the obtained sodium ion battery is more excellent. If the mass concentration of the sodium supplement solution is too high, it will lead to excessive sodium ions in the positive electrode, resulting in a low NP ratio and the problem of sodium precipitation. If the mass concentration of the sodium supplement solution is too low, it will lead to insufficient sodium supplementation, reduced first efficiency, and the inability to eliminate negative electrode defects to the maximum extent, thereby affecting the cycle performance.

[0024] Preferably, the positive electrode main material includes a positive electrode active material, a conductive agent and a binder.

[0025] Preferably, the mass ratio of the positive electrode active material, the conductive agent and the binder is (94-97): (2.5-3.5): (2-2.5), preferably (94-95): (2.5-3): (2-2.5), for example, it can be 94:2.5:2, 94:2.5:2.5, 94:3:2, 94:3:2.5, 94:3.5:2, 94:3.5:2.5, 95:2.5:2, 95:2.5:2.5, 95:3:2, 95 :3:2.5, 95:3.5:2, 95:3.5:2.5, 96:2.5:2, 96:2.5:2.5, 96:3:2, 96:3:2.5, 96:3.5:2, 96:3.5:2, 97:2.5:2, 97:2.5:2.5, 97:3:2, 97:3:2.5, 97:3.5:2 or 97:3.5:2.5, but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the solid content of the sodium ion battery positive electrode slurry is 40%-60%, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or 60%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the present invention has no particular limitation on the type of the positive electrode active material. As an example, the positive electrode active material includes at least one of polyanions, P2-type transition metal oxides, O3-type transition metal oxides, or Prussian blue.

[0028] Preferably, the present invention has no particular limitation on the type of the conductive agent. As an example, the conductive agent includes at least one of conductive carbon black, graphene, graphene oxide, acetylene black, carbon nanotubes, porous carbon or graphite carbon.

[0029] Preferably, the present invention has no particular limitation on the type of the adhesive. As an example, the adhesive includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or sodium alginate.

[0030] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0031] (1) mixing a sodium supplement and a first solvent to obtain a sodium supplement solution having a mass concentration of 0.1 wt% to 1.5 wt%; the sodium supplement comprises sodium benzene salt;

[0032] (2) mixing the sodium supplement solution and the positive electrode main material to obtain a sodium ion battery positive electrode slurry with a solid content of 40% to 60%;

[0033] The first solvent comprises a second solvent, an alcohol solvent, and a dispersant in a mass ratio of 1:(0.005-0.01):(0.002-0.005);

[0034] The positive electrode main material includes a positive electrode active material, a conductive agent and a binder in a mass ratio of (94-97):(2.5-3.5):(2-2.5).

[0035] In a second aspect, the present invention provides a positive electrode slurry for a sodium ion battery, which is prepared according to the preparation method described in the first aspect.

[0036] In a third aspect, the present invention provides a sodium ion positive electrode plate, which is obtained by coating the sodium ion battery positive electrode slurry described in the second aspect on a current collector.

[0037] Preferably, the present invention has no particular limitation on the type of current collector. As an example, the current collector includes any one of aluminum foil, composite aluminum foil, steel wire mesh or nickel foam.

[0038] After the preparation of the sodium supplement solvent is completed, the positive electrode slurry can be prepared according to a conventional positive electrode slurry preparation method, thereby avoiding the additional slurry preparation and coating steps of sodium benzene salt and simplifying the preparation process.

[0039] In a third aspect, the present invention provides a sodium ion battery, comprising the sodium ion positive electrode sheet described in the third aspect.

[0040] The sodium ion battery provided by the present invention has high initial efficiency and long cycle life.

[0041] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The present invention first dissolves sodium benzene salt, a sodium supplement agent, in a first solvent to obtain a sodium supplement agent solution, then adds the positive electrode main material thereto, and mixes them evenly to obtain a positive electrode slurry. The preparation method of the present invention uses an alcohol solvent to increase the solubility of the organic sodium salt, and the dispersant can prevent the sodium supplement agent from agglomerating and better disperse it. The sodium supplement agent is directly blended with the positive electrode material. The preparation method does not require special processes and can be achieved in a stirred tank at room temperature in a positive electrode slurry workshop.

[0044] (2) After the sodium supplement solvent is prepared, the cathode slurry can be prepared according to conventional cathode slurry preparation methods, avoiding the additional slurry preparation and coating steps of sodium benzene salt, thereby simplifying the preparation process. The sodium ion battery provided by the present invention has a high initial efficiency and a long cycle life. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be further described below by way of specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention, which shall be subject to the claims.

[0046] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0047] Example 1

[0048] This embodiment provides a method for preparing a positive electrode slurry for a sodium ion battery, the preparation method comprising the following steps:

[0049] (1) mixing sodium o-dihydroxybenzene and a first solvent to obtain a sodium supplement solution having a mass concentration of 1.5 wt %;

[0050] (2) mixing the sodium supplement solution and the positive electrode main material to obtain a sodium ion battery positive electrode slurry with a solid content of 50%;

[0051] The first solvent includes NMP, isopropyl alcohol, and PVP (K30, molecular weight 40,000) in a mass ratio of 1:0.005:0.003;

[0052] The main materials of the positive electrode include Na4Fe3(PO4)2P2O7 positive electrode active material, conductive carbon black and PVDF with a mass ratio of 95:3:2.

[0053] The prepared sodium ion battery positive electrode slurry is coated on aluminum foil, and then dried and rolled to obtain a sodium ion positive electrode sheet.

[0054] Example 2

[0055] This embodiment provides a method for preparing a positive electrode slurry for a sodium ion battery, the preparation method comprising the following steps:

[0056] (1) mixing sodium p-dihydroxybenzene and a first solvent to obtain a sodium supplement solution with a mass concentration of 0.5 wt %;

[0057] (2) mixing the sodium supplement solution and the positive electrode main material to obtain a sodium ion battery positive electrode slurry with a solid content of 45%;

[0058] The first solvent includes DMF, butanediol and Disuper dispersant (S9100) in a mass ratio of 1:0.008:0.002; the positive electrode main material includes Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2 positive electrode active material, acetylene black and polytetrafluoroethylene.

[0059] The prepared sodium ion battery positive electrode slurry is coated on aluminum foil, and then dried and rolled to obtain a sodium ion positive electrode sheet.

[0060] Example 3

[0061] This embodiment provides a method for preparing a positive electrode slurry for a sodium ion battery, the preparation method comprising the following steps:

[0062] (1) mixing sodium trihydroxybenzene and a first solvent to obtain a sodium supplement solution having a mass concentration of 1.1 wt %;

[0063] (2) mixing the sodium supplement solution and the positive electrode main material to obtain a sodium ion battery positive electrode slurry with a solid content of 60%;

[0064] The first solvent includes a second solvent (ethanol:toluene = 1 vol%:1 vol%), isopropyl alcohol and polymethyl acrylate PMMA (molecular weight 35,000) in a mass ratio of 1:0.01:0.003; the positive electrode main material includes Na4Fe3(PO4)2P2O7 positive electrode active material, carbon nanotubes and sodium alginate in a mass ratio of 96:2:2.

[0065] The prepared sodium ion battery positive electrode slurry is coated on aluminum foil, and then dried and rolled to obtain a sodium ion positive electrode sheet.

[0066] Example 4

[0067] This embodiment provides a sodium ion battery positive electrode slurry, which is different from Example 1 only in that when preparing the sodium ion battery positive electrode slurry, the mass ratio of NMP, isopropyl alcohol and PVP in step (1) is 1:0.005:0.001.

[0068] Example 5

[0069] This embodiment provides a sodium ion battery positive electrode slurry, which is different from Example 1 only in that when preparing the sodium ion battery positive electrode slurry, the mass ratio of NMP, isopropyl alcohol and PVP in step (1) is 1:0.02:0.003.

[0070] Example 6

[0071] This embodiment provides a sodium ion battery positive electrode slurry, which is different from Example 1 only in that when preparing the sodium ion battery positive electrode slurry, the mass ratio of NMP, isopropyl alcohol and PVP in step (1) is 1:0.001:0.003.

[0072] Example 7

[0073] This embodiment provides a positive electrode slurry for a sodium ion battery. The only difference from Example 1 is that when preparing the positive electrode slurry for a sodium ion battery, the concentration of the sodium supplement solution in step (1) is 0.05 wt%.

[0074] Example 8

[0075] This embodiment provides a positive electrode slurry for a sodium ion battery. The only difference from Example 1 is that when preparing the positive electrode slurry for a sodium ion battery, the concentration of the sodium supplement solution in step (1) is 2 wt %.

[0076] Comparative Example 1

[0077] This comparative example provides a sodium ion battery positive electrode slurry, which differs from Example 1 only in that, when preparing the sodium ion battery positive electrode slurry, no isopropyl alcohol is added in step (1).

[0078] Comparative Example 2

[0079] This comparative example provides a sodium ion battery positive electrode slurry, which differs from Example 1 only in that no dispersant is added in step (1) when preparing the sodium ion battery positive electrode slurry.

[0080] Test method: The sodium ion battery positive electrode slurries prepared in the examples and comparative examples were tested. The test results are shown in Table 1 below.

[0081] Assembly of sodium ion battery: The electrode sheets prepared in Examples 1-7 of the present invention and Comparative Example 1 were used as positive electrodes, and the surface density of the positive electrode coating was 150 g / m 2 The negative electrode is hard carbon, the diaphragm is a double-sided ceramic diaphragm, and the electrolyte is a commercial ether electrolyte, and a sodium ion battery is assembled.

[0082] First-cycle coulombic efficiency: The prepared sodium-ion battery is charged and discharged at a rate of 0.5C in the voltage range of 1.5V-3.45V, and the ratio of the battery's first-cycle discharge capacity to the charge capacity is obtained.

[0083] Cycle life: The sodium ion battery was charged and discharged at a rate of 0.5C. The number of cycles when the capacity decayed to 80% of the initial discharge capacity was recorded as the cycle life. The results are shown in Table 1.

[0084] Table 1

[0085]

[0086] The test results show that:

[0087] (1) It can be seen from Examples 1 to 3 that the preparation method of the present invention can increase the solubility of the organic sodium salt by using an alcohol solvent, and the dispersant can prevent the sodium supplement agent from agglomerating, thereby better dispersing the sodium supplement agent. The sodium supplement agent is directly blended with the positive electrode material. The preparation method does not require a special process and can be achieved by stirring a kettle at room temperature in the positive electrode slurry workshop. The additional slurry preparation and coating process of sodium benzene salt is avoided, simplifying the preparation process. The sodium ion battery provided by the present invention has a high first efficiency and a long cycle life.

[0088] (2) By comparing Example 1 with Example 4-Example 6, it can be seen that the present invention further controls the mass ratio of the second solvent, alcohol solvent and dispersant to be 1: (0.005-0.01): (0.002-0.005), and the mass ratios of the components of the first solvent cooperate with each other, so that the sodium benzene salt sodium supplement can be completely dissolved and the uniformity of the sodium supplement solution is maintained, creating conditions for the subsequent addition of the positive electrode main material. If the content of the dispersant is too low, the phenolate ions and sodium ions cannot be evenly dispersed in the solution; if the content of the dispersant is too high, unnecessary waste will be caused. If the content of the alcohol solvent is too high, the excessive alcohol substance will have a certain effect on the electrical properties; if the content of the alcohol solvent is too low, the sodium supplement solvent will be insufficient (the main reason is that the sodium supplement solution is mainly decomposed into sodium ions and phenolate ions, and too low an alcohol content will cause the solution polarity to be insufficient and unable to dissolve).

[0089] (3) By comparing Example 1 with Example 7-Example 8, it can be seen that the present invention further controls the mass concentration of the sodium supplement solution to be 0.1wt%-1.5wt%. Within this range, the cycle performance of the obtained sodium ion battery is more excellent. If the mass concentration of the sodium supplement solution is too high, it will lead to excessive sodium ions in the positive electrode, resulting in a too low NP ratio, which is prone to sodium precipitation problems and causes life attenuation; if the mass concentration of the sodium supplement solution is too low, it will lead to insufficient sodium supplementation, reduced first efficiency, and the inability to eliminate negative electrode defects to the maximum extent, thereby affecting the cycle life.

[0090] (4) It can be seen from Example 1 and Comparative Examples 1-2 that if no alcohol solvent or dispersant is added, the sodium supplement cannot be prepared and the use conditions cannot be met.

[0091] In summary, in order to improve the solubility of the sodium supplement, the present invention adds an alcohol solvent and a dispersant during the preparation of the positive electrode slurry. The alcohol solvent can increase the solubility of the organic sodium salt, and the dispersant can prevent the sodium supplement from agglomerating, thereby better dispersing the sodium supplement. Furthermore, by optimizing the solvent ratio, the sodium supplement is directly blended with the positive electrode material. This preparation method does not require a special process and can be achieved by a stirring kettle at room temperature in the positive electrode slurry workshop. The additional slurry preparation and coating process of sodium benzene salt is avoided, simplifying the preparation process. The sodium ion battery provided by the present invention has a high first effect and a long cycle life.

[0092] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a positive electrode slurry for a sodium ion battery, characterized in that: The preparation method comprises the following steps: Mixing a sodium supplement agent and a first solvent to obtain a sodium supplement agent solution; mixing the sodium supplement agent solution and a positive electrode main material to obtain a sodium ion battery positive electrode slurry; The sodium supplement includes benzene sodium salt; the first solvent includes an alcohol solvent and a dispersant.

2. The preparation method according to claim 1, characterized in that The sodium benzene salt includes any one of sodium o-dihydroxybenzene, sodium m-dihydroxybenzene, sodium p-dihydroxybenzene or sodium trihydroxybenzene, or a combination of at least two thereof, preferably sodium o-dihydroxybenzene.

3. The preparation method according to claim 1 or 2, characterized in that The first solvent also includes a second solvent; Preferably, the mass ratio of the second solvent, the alcohol solvent and the dispersant in the first solvent is 1:(0.005-0.01):(0.002-0.005), preferably 1:(0.005-0.007):(0.002-0.003); Preferably, the second solvent comprises any one or a combination of at least two of N-methylpyrrolidone, N,N-dimethylformamide, water, ethanol or toluene; Preferably, the alcohol solvent includes isopropyl alcohol and / or butanediol; Preferably, the dispersant includes any one of polyvinyl pyrrolidone, polyamide, polyimide, polyurethane or polyacrylate, or a combination of at least two thereof.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mass concentration of the sodium supplement solution is 0.1wt%-1.5wt%, preferably 1.4wt%-1.5wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that The positive electrode main material includes a positive electrode active material, a conductive agent and a binder; Preferably, the mass ratio of the positive electrode active material, the conductive agent and the binder is (94-97):(2.5-3.5):(2-2.5), preferably (94-95):(2.5-3):(2-2.5).

6. The preparation method according to any one of claims 1 to 5, characterized in that The solid content of the sodium ion battery positive electrode slurry is 40%-60%; Preferably, the positive electrode active material includes any one of polyanions, P2-type transition metal oxides, O3-type transition metal oxides, and Prussian blue, or a combination of at least two thereof.

7. The preparation method according to any one of claims 1 to 6, characterized in that The preparation method comprises the following steps: (1) mixing a sodium supplement and a first solvent to obtain a sodium supplement solution having a mass concentration of 0.1 wt% to 1.5 wt%; the sodium supplement comprises sodium benzene salt; (2) mixing the sodium supplement solution and the positive electrode main material to obtain a sodium ion battery positive electrode slurry with a solid content of 40% to 60%; The first solvent comprises a second solvent, an alcohol solvent, and a dispersant in a mass ratio of 1:(0.005-0.01):(0.002-0.005); The positive electrode main material includes a positive electrode active material, a conductive agent and a binder in a mass ratio of (94-97):(2.5-3.5):(2-2.5).

8. A sodium ion battery positive electrode slurry, characterized in that: The sodium ion battery positive electrode slurry is prepared according to the preparation method according to any one of claims 1 to 7.

9. A sodium ion positive electrode plate, characterized in that: The sodium ion positive electrode sheet is obtained by coating the sodium ion battery positive electrode slurry according to claim 8 on a current collector.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium ion positive electrode sheet according to claim 9.

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