A preparation method of a positive electrode sodium supplement

Abstract

The present invention discloses a preparation method of a sodium supplement for the positive electrode, comprising the following steps: S1: Mix a sodium salt, a conductive agent, and a solvent, and mechanically stir and mix them evenly to obtain slurry A; S2: Perform spray granulation on slurry A to obtain a precursor; S3: Calcinate the precursor in a gas atmosphere to obtain the sodium supplement for the positive electrode; the sodium salt is one or several combinations of sodium carbonate and sodium bicarbonate; the solvent is deionized water or ethanol; the conductive agent is an aqueous solution of carbon nanotubes or an aqueous solution of graphene, and its solid content is 4% - 6%; the mass ratio of the sodium salt, the conductive agent, and the solvent is 1:0.5 - 3.0:0.5 - 5. The present invention combines a sodium salt with a nano conductive agent, and through the efficient catalytic action of the nano material, the decomposition of the sodium salt is accelerated, and at the same time, the efficient conduction of electrons is ensured during the charging process, which is beneficial to the realization of the sodium supplement effect of the battery. The present invention is simple and easy to implement, uses a sodium salt with low cost, and the treated sodium supplement material is safe, non-toxic, and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the field of sodium-ion batteries, and specifically to a preparation method of a sodium supplement for the positive electrode. Background Art

[0002] With the scarcity of traditional fossil energy and the increasing environmental pressure on humanity, new energy forms are imminent. The combination of renewable energy and electrochemical energy storage methods has become the trend of the future energy structure. However, due to the scarcity and uneven distribution of lithium resources, the cost of lithium-ion batteries has remained high in recent years, and there are significant risks to national strategic resource security. Sodium has an abundant reserve abundance and the advantage of natural low cost. Especially for the field of large-scale energy storage, the development of sodium-ion batteries is of great significance. The negative electrode of a sodium-ion battery generally uses soft carbon or hard carbon materials. When forming the SEI film during the first charge, its Coulomb efficiency is low. Especially when matching with a positive electrode with a relatively low specific capacity, the first irreversible capacity and efficiency loss are large, and the energy density of the full battery is low.

[0003] By supplementing sodium, the sodium ions lost for the first time can be compensated, which can effectively improve the low Coulomb efficiency of the battery and increase the energy density of the battery. The existing sodium supplementation methods for sodium-ion batteries include negative electrode sodium supplementation and positive electrode sodium supplementation. Negative electrode sodium supplementation generally has complex operations, high costs, and great difficulties in large-scale industrial production. Positive electrode sodium supplementation generally involves adding sodium-rich materials to the positive electrode, and sodium ions are released through oxidative decomposition during the first charge for sodium supplementation. This method has simple operations and is conducive to industrialization.

[0004] Regarding the selection of the sodium supplement, first, it is required to provide a high capacity of sodium ions within the battery charging voltage range, and the Coulomb efficiency of this material itself should be as low as possible. After the sodium ions are released during the first charge, the discharge is irreversible, so as to ensure that all the released sodium ions are used for sodium supplementation. Second, the sodium supplement material has excellent chemical stability in the battery, does not participate in or affect the electrochemical reaction, and there is no physical change during the charge and discharge process. Third, it does not pollute the environment, is compatible with existing battery process equipment in the battery manufacturing process, and has a certain processability. Fourth, the material preparation is simple, the cost is low, and it is suitable for industrialization.

[0005] Patent CN110683944A discloses a squarate and its preparation method and application, using a mixture of squaric acid and alkali to prepare a series of squarates as sodium supplements. Its preparation process uses high-energy ball milling and is prepared in an organic solvent. Its process is complex and not conducive to industrialization. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a sodium supplement for the positive electrode, develop a sodium supplement material and method that meet the requirements, and at the same time take into account the low-cost requirement, which plays a very important role in the development and popularization of sodium-ion batteries.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A preparation method of a positive electrode sodium supplement agent, comprising the following steps:

[0009] S1: Mix sodium salt, conductive agent, and solvent, and mechanically stir and mix evenly to obtain slurry A;

[0010] S2: Spray granulate slurry A to obtain a precursor;

[0011] S3: Calcinate the precursor in a gas atmosphere to obtain a positive electrode sodium supplement agent.

[0012] Preferably, the sodium salt is one or a combination of sodium carbonate and sodium bicarbonate.

[0013] Preferably, the solvent is deionized water or ethanol.

[0014] Preferably, the conductive agent is an aqueous solution of carbon nanotubes or an aqueous solution of graphene, and its solid content is 4% - 6%.

[0015] Preferably, the mass ratio of the sodium salt, conductive agent, and solvent is 1:0.5 - 3.0:0.5 - 5.

[0016] Preferably, the gas in the gas atmosphere is argon or nitrogen.

[0017] Preferably, the calcination temperature in step S3 is 100 - 400 °C, and the calcination time is 1 - 20 h.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0019] In the present invention, the sodium salt is compounded with the nano conductive agent. Through the efficient catalytic action of the nano material, the decomposition of the sodium salt is accelerated, and at the same time, the efficient conduction of electrons is ensured during the charging process, which is beneficial to the realization of the sodium supplement effect of the battery. The present invention is simple and easy to implement, and the sodium salt is low in cost, suitable for industrial promotion. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 The first charge-discharge curve of sodium metal with sodium carbonate in the comparative example;

[0022] Figure 2SEM image of the sodium supplement in Example 1;

[0023] Figure 3 First charge-discharge curves of the sodium supplement against metallic sodium in Example 1;

[0024] Figure 4 First charge-discharge curves of the sodium supplement against metallic sodium in Example 2;

[0025] Figure 5 First charge-discharge curve of the composite cathode material of the sodium supplement against metallic sodium in Example 3. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0028] As Figures 1 - 5 shown,

[0029] Example 1:

[0030] Preparation of the sodium supplement: Weigh 100 g of sodium bicarbonate and dissolve it in 250 g of deionized water. Then add 250 g of carbon nanotube aqueous slurry (solid content is 4%). After mechanical stirring for 30 min, introduce it into a spray dryer for spray granulation to obtain a precursor. Transfer the precursor to a tubular furnace and sinter it at 300 °C for 12 h under a nitrogen atmosphere to obtain the sodium supplement.

[0031] Battery assembly and testing: Sodium carbonate, SP, and PVDF were weighed in a mass ratio of 90:5:5, and a certain amount of NMP was added for high-speed dispersion, followed by coating and roller pressing. After drying, φ14mm positive electrode sheets were cut and matched with φ16mm metal sodium sheets. The electrolyte was NaPF6+EC+PC+EMC system, and the battery was assembled and tested. The first charge and discharge capacity was as follows: Figure 3 As shown, the first charge and discharge capacities are 403.56 mAh / g and 0.2 mAh / g respectively, and the first coulombic efficiency is 0.05%.

[0032] Embodiment 2:

[0033] Preparation of sodium supplement: 100g sodium carbonate was weighed and dissolved in 200g water, then 200g carbon nanotube aqueous slurry (solid content 4%) was added, mechanically stirred for 30min, and then introduced into a spray dryer for spray granulation to obtain a precursor. The precursor was transferred to a tubular furnace and sintered at 300℃ for 12h in a nitrogen or argon atmosphere to obtain a sodium supplement.

[0034] Battery assembly and testing: Sodium carbonate, SP, and PVDF were weighed in a mass ratio of 90:5:5, and a certain amount of NMP was added for high-speed dispersion, followed by coating and roller pressing. After drying, φ14mm positive electrode sheets were cut and matched with φ16mm metal sodium sheets. The electrolyte was NaPF6+EC+PC+EMC system, and the battery was assembled and tested. The first charge and discharge capacity was as follows: Figure 4 As shown, the first charge and discharge capacities are 530.69 mAh / g and 4.71 mAh / g respectively, and the first coulombic efficiency is 0.89%.

[0035] Embodiment three:

[0036] Preparation of sodium supplement: 100g sodium carbonate was weighed and dissolved in 200g water, then 200g carbon nanotube aqueous slurry (solid content 4%) was added, mechanically stirred for 30min, and then introduced into a spray dryer for spray granulation to obtain a precursor. The precursor was transferred to a tubular furnace and sintered at 300℃ for 12h under a nitrogen atmosphere to obtain a sodium supplement.

[0037] Battery assembly and testing: Sodium ferrous sulfate, SP, and PVDF are weighed in a mass ratio of 90:5:5, and a certain amount of NMP is added for high-speed dispersion, and then coated, and the pole piece is ready for use. Sodium carbonate, SP, and PVDF are weighed in a mass ratio of 90:5:5, and a certain amount of NMP is added for high-speed dispersion. The sodium supplement slurry is compositely coated and rolled with the sodium ferrous sulfate pole piece. After drying, the φ14mm positive pole piece is cut and matched with the φ16mm metal sodium sheet. The electrolyte is the NaPF6+EC+PC+EMC system, and the assembly is tested by power-on. The first charge and discharge capacity is as follows: Figure 5As shown, the first charge and discharge capacities are 549.36 mAh / g and 101.16 mAh / g respectively, and the first Coulombic efficiency is 18.41%.

[0038] Comparative example:

[0039] Preparation of sodium supplement agent: None.

[0040] Battery assembly and testing: Sodium carbonate, SP, and PVDF were weighed according to a mass ratio of 90:5:5, added with a certain amount of NMP for high-speed dispersion, then coated and roll-pressed. After drying, a φ14 mm positive electrode sheet was cut. A φ16 mm sodium metal sheet was matched. The electrolyte was a NaPF6 + EC + PC + EMC system, and a button cell full battery was assembled for testing. The first charge and discharge capacities are as Figure 1 shown. The first charge and discharge capacities are 45.51 mAh / g and 2.03 mAh / g respectively, and the first Coulombic efficiency is 4.47%.

[0041] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a sodium supplement for a positive electrode, characterized in that, It includes the following steps: S1: Mix sodium salt, conductive agent and solvent, and mechanically stir and mix them evenly to obtain slurry A; S2: Spray granulate slurry A to obtain a precursor; S3: Calcinate the precursor in a gas atmosphere to obtain a sodium supplement for the positive electrode; The sodium salt is one or a combination of sodium carbonate and sodium bicarbonate; The solvent is deionized water or ethanol; The conductive agent is an aqueous solution of carbon nanotubes or an aqueous solution of graphene, and its solid content is 4% - 6%; The mass ratio of the sodium salt, conductive agent and solvent is 1:0.5 - 3.0:0.5 - 5; The gas in the gas atmosphere is argon or nitrogen; The calcination temperature in step S3 is 100 - 400 °C, and the calcination time is 1 - 20 h.

2. The preparation method of the positive electrode sodium supplement agent according to claim 1, characterized in that: The calcination temperature is 300 °C, and the calcination time is 12 h.

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