A composite lithium supplementing flame-retardant material, a preparation method and application thereof

Abstract

The application provides a composite lithium supplement and flame retardant material, a preparation method and application thereof, and the preparation method comprises the following steps: S1: preparing a lithium supplement solution: adding lithium supplement powder into a solvent and stirring until uniform; S2: adsorption and compounding: adding nano-silicon dioxide into the solution obtained in the step S1, stirring until uniform, and then standing and adsorbing; S3: post-treatment: filtering the product obtained in the step S2, collecting the solid product and drying, so as to obtain the composite lithium supplement and flame retardant material. Through the above preparation method, the lithium supplement and flame retardant functions are realized in a synergistic manner, and the problems of poor dispersibility and insufficient compatibility of the existing materials are solved.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation, specifically to a composite lithium-replenishing flame-retardant material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, power batteries, and energy storage. However, during long-term cycling, electrolyte decomposition and the continuous formation of the SEI film consume a large amount of active lithium, leading to battery capacity decay and shortened cycle life. Furthermore, the flammable nature of the electrolyte poses a risk of thermal runaway, severely limiting improvements in battery safety.

[0003] In existing technologies, lithium replenishing agents are mainly divided into two categories: inorganic lithium replenishing agents (such as Li2O, LiOH, Li2CO3, etc.) and organic lithium replenishing agents. Inorganic lithium replenishing agents have higher theoretical capacity, but they generally suffer from problems such as strong air sensitivity, easy moisture absorption and deterioration, and poor compatibility with electrolytes. In addition, they have high delithiation potential and low capacity utilization. Although organic lithium replenishing agents have improved stability, it is difficult to balance lithium replenishment efficiency and safety.

[0004] Regarding flame retardants, traditional bromine-based and phosphazene-based flame retardants can improve the flame retardancy of electrolytes, but they are mostly inert additives that occupy internal battery space and reduce energy density. Some flame retardants can also affect ion conduction efficiency, leading to a decrease in battery rate performance.

[0005] In addition, existing technologies often achieve lithium replenishment and flame retardant functions by adding two different materials separately, which leads to problems such as complex formulations, poor compatibility, and increased costs, making it difficult to meet the development needs of high energy density and high safety batteries. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for preparing composite lithium-added flame-retardant materials, which addresses the problems of complex formulations, poor compatibility, increased costs, and complicated preparation processes in existing battery lithium-added flame-retardant formulations.

[0007] The second objective of this invention is to provide a composite lithium-supplemented flame-retardant material, which is prepared by the above-described preparation method.

[0008] A third objective of this invention is to provide an application of the above-mentioned composite lithium-replenishing flame-retardant material in the positive electrode of a battery.

[0009] To achieve the aforementioned first objective, the present invention provides a method for preparing a composite lithium-replenishing flame retardant material, the method comprising the following steps: S1: preparing a lithium-replenishing agent solution: adding lithium-replenishing agent powder to a solvent and stirring until uniform; S2: adsorption and composite: adding nano-silica to the solution in step S1, stirring until uniform, and then allowing it to stand for adsorption; S3: post-treatment: filtering the product obtained in step S2, collecting the solid product and drying it to obtain the composite lithium-replenishing flame retardant material.

[0010] As can be seen from the above scheme, the preparation method solves the problems of strong air sensitivity, particle agglomeration, high delithiation potential, and insufficient capacity utilization when lithium replenishing agents are used alone. Nano-silica (SiO2) has a high specific surface area, good adsorption and dispersibility, and also has a certain flame retardant effect. The combination of the two achieves synergistic effects of lithium replenishment and flame retardancy, while solving the problems of poor dispersibility and insufficient compatibility of existing materials. Specifically, during the static adsorption process, nano-silica adsorbs the lithium replenishing agent, which is nano-sized on the surface and in the internal pores of the silica, improving the lithium replenishment capacity utilization and reducing the lithium salt decomposition temperature. The flame retardant is nano-silica, which has a large number of nano-sized pores within and between particles. Its porous structure provides a large specific surface area, providing more adsorption sites for solvated lithium ions and anions of the lithium salt. After the adsorbed lithium salt solution is dried, the adsorbed lithium salt is nano-sized in situ. At the same time, this preparation method is simple, energy-efficient, and low-cost, and can be implemented without complex equipment and instruments.

[0011] A further proposed approach is to use a lithium supplement powder to nano-silica in a mass ratio of (0.5~2):1.

[0012] As can be seen from the above scheme, within the above proportion, lithium supplement powder can be nano-sized within nano-silica.

[0013] A further option is to select at least one lithium supplement from lithium oxalate, lithium formate, lithium tartrate, and lithium citrate.

[0014] As can be seen from the above scheme, the lithium replenishing agent has a high theoretical capacity and excellent air stability, and is not easily deteriorated by absorbing moisture.

[0015] A further option is to use deionized water and / or organic solvents as solvents, with a mass ratio of lithium supplement to solvent of 1:(1~100).

[0016] As can be seen from the above scheme, within the above proportion, the lithium supplement can be uniformly dispersed in deionized water, ensuring the effective execution of subsequent steps.

[0017] A further approach involves using nano-silica with a particle size of 10nm~1000nm and a specific surface area of ​​100m². 2 / g~3000m 2 / g.

[0018] A further approach is to use nano-silica with a particle size of 10nm to 500nm.

[0019] As can be seen from the above scheme, nano-silica has excellent adsorption performance under the above parameters, which enables the lithium supplement to be uniformly loaded on its surface and in its pores.

[0020] A further option is to allow the adsorption process in step S2 to proceed by allowing the adsorption to stand at room temperature (25°C) for 6 to 24 hours.

[0021] As can be seen from the above scheme, the above-mentioned settling time can ensure that the lithium replenishing agent can be fully nano-sized on the surface and in the internal pores of silica.

[0022] A further option is to use a drying temperature of 60℃~120℃ in step S3.

[0023] As can be seen from the above scheme, the above drying temperature can ensure rapid evaporation of moisture and shorten the drying time, while preventing the product structure from being damaged by excessively high temperatures.

[0024] To achieve the second objective described above, the present invention provides a composite lithium-supplemented flame retardant material prepared by the preparation method of the composite lithium-supplemented flame retardant material described in any of the above schemes.

[0025] To achieve the third objective mentioned above, the present invention provides an application of the above-mentioned composite lithium-replenishing flame retardant material in the positive electrode of a battery, wherein the mass ratio of the composite lithium-replenishing flame retardant material in the positive electrode material of the battery is 0.1% to 15%.

[0026] As can be seen from the above scheme, the aforementioned composite lithium-replenishing flame-retardant material can simultaneously improve battery cycle life and safety performance. Detailed Implementation

[0027] This invention provides a method for preparing a composite lithium-supplemented flame-retardant material, the method comprising the following steps: S1: Preparation of lithium supplement solution: Add lithium supplement powder to solvent and stir until uniform. The lithium supplement is selected from at least one of lithium oxalate, lithium formate, lithium tartrate, and lithium citrate. The solvent is deionized water and / or organic solvents such as ethanol, preferably deionized water. The mass ratio of lithium supplement to solvent is 1:(1~100). Preferably, the mass ratio of lithium supplement to deionized water is 1:(1~20). S2: Adsorption and Recombination: Nano-silica is added to the solution from step S1, stirred until homogeneous, and then allowed to stand at room temperature (25°C) for 6-24 hours for adsorption. The mass ratio of lithium supplement powder to nano-silica is (0.5-2):1. The particle size of the nano-silica is 10nm-1000nm, preferably 10nm-500nm, and the specific surface area of ​​the nano-silica is 100m². 2 / g~3000m 2 / g; S3: Post-processing: Filter the product obtained in step S2, collect the solid product and dry it at a temperature of 60℃~120℃ to obtain the composite lithium-supplemented flame retardant material.

[0028] The mass ratio of the aforementioned composite lithium-replenishing flame-retardant material in the battery cathode material is 0.1% to 15%.

[0029] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0030] Example 1 S1 Preparation of lithium oxalate aqueous solution: Add 35 g of lithium oxalate to 500 mL of deionized water and stir magnetically for 2 hours; S2 Adsorption and Combination: Add 30 g of silica particles with a particle size of 30 nm to the lithium oxalate aqueous solution in step S1, stir for 2 hours, and then let it stand at room temperature for 12 hours for adsorption. S3 Post-processing: The mixture from step S2 is filtered, the solid product is collected, dried at 80°C for 12 hours, and then vacuum dried for 12 hours to obtain the composite lithium-supplemented flame retardant material of Example 1.

[0031] Preparation of S4 cathode sheet: The composite lithium-supplementing flame-retardant material of Example 1 above was mixed with ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNT) in a mass ratio of 3:94:1.4:1.5:0.1, and then coated with N-methylpyrrolidone (NMP) as solvent. The areal mass of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0032] Preparation of S5 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm³. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0033] S6 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them into a 5000mAh battery as described in Example 1 by stacking. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0034] Example 2 The difference between Example 2 and Example 1 is only that in step S4, the mass ratio of the composite lithium-replenishing flame retardant material to the ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNT) is 4:93:1.4:1.5:0.1. The battery of Example 2 was prepared by the above ratio.

[0035] Example 3 S1 Preparation of lithium formate aqueous solution: Add 150 g of lithium formate to 500 mL of deionized water and stir magnetically for 2 hours; S2 Adsorption and Combination: Add 30 g of silica particles with a particle size of 30 nanometers to the lithium formate aqueous solution in step S1, stir for 2 hours, and then let it stand at room temperature for 12 hours for adsorption. S3 Post-processing: The mixture from step S2 is filtered, the solid product is collected, dried at 100°C for 12 hours, and then vacuum dried for 12 hours to obtain the composite lithium-supplemented flame retardant material of Example 3.

[0036] Preparation of S4 cathode sheet: The composite lithium-supplementing flame-retardant material of Example 3 above was mixed with ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNT) in a mass ratio of 4:93:1.4:1.5:0.1, and then coated with N-methylpyrrolidone (NMP) as solvent. The areal load of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0037] Preparation of S5 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm³. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0038] S6 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them into a 5000mAh battery as described in Example 3 by stacking. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0039] Example 4 S1 Preparation of lithium tartrate aqueous solution: Add 180 g of lithium tartrate to 500 mL of deionized water and stir magnetically for 2 hours; S2 Adsorption and Combination: Add 30 g of silica particles with a particle size of 30 nm to the lithium oxalate aqueous solution in step S1, stir for 2 hours, and then let it stand at room temperature for 12 hours for adsorption. S3 Post-processing: The mixture system of step S2 is filtered, the solid product is collected, dried at 100°C for 12 hours, and then vacuum dried for 12 hours to obtain the composite lithium-supplemented flame retardant material of Example 4.

[0040] Preparation of S4 cathode sheet: The composite lithium-supplementing flame-retardant material of Example 4 above was mixed with ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNT) in a mass ratio of 3:94:1.4:1.5:0.1, and then coated with N-methylpyrrolidone (NMP) as solvent. The areal mass of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0041] Preparation of S5 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm³. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0042] S6 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them into a 5000mAh battery as described in Example 4 by stacking. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0043] Example 5 S1 Preparation of lithium citrate aqueous solution: Add 250 g of lithium citrate to 500 mL of deionized water and stir magnetically for 2 hours; S2 Adsorption and Combination: Add 30 g of silica particles with a particle size of 30 nm to the lithium oxalate aqueous solution in step S1, stir for 2 hours, and then let it stand at room temperature for 12 hours for adsorption. S3 Post-processing: The mixture system of step S2 is filtered, the solid product is collected, dried at 110°C for 12 hours, and then vacuum dried for 12 hours to obtain the composite lithium-supplemented flame retardant material of Example 5.

[0044] Preparation of S4 cathode sheet: The composite lithium-supplementing flame-retardant material of Example 5 above was mixed with ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNT) in a mass ratio of 3:94:1.4:1.5:0.1, and then coated. N-methylpyrrolidone (NMP) was used as a solvent. The areal mass of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0045] Preparation of S5 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm³. -2The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0046] S6 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them into a 5000mAh battery as described in Example 5 by stacking. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0047] Comparative Example 1 Preparation of S1 cathode sheet: Nano-silica, ternary 8-series cathode (NCM811), PVDF binder, conductive carbon powder Super P (SP), and conductive carbon nanotubes (CNTs) were mixed and coated in a mass ratio of 3:94:1.4:1.5:0.1, using N-methylpyrrolidone (NMP) as a solvent. The areal load of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0048] Preparation of S2 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm⁻¹. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0049] S3 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them into a 5000mAh battery, similar to Comparative Example 1, using a stacking method. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0050] Comparative Example 2 Preparation of S1 cathode sheet: Lithium oxalate, ternary 8-series cathode (NCM811), PVDF binder, super P conductive carbon powder (SP), and conductive carbon nanotubes (CNTs) were mixed and coated at a mass ratio of 4:93:1.4:1.5:0.1, with N-methylpyrrolidone (NMP) as the solvent. The areal load of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0051] Preparation of S2 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm⁻¹. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0052] S3 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them using a stacking method to create a battery with a capacity of 5000mAh, similar to Comparative Example 2. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0053] Comparative Example 3 S1. Lithium tartrate and nano-silica were ball-milled and mixed at a mass ratio of 1:3 to obtain the composite lithium-supplemented flame retardant material of Comparative Example 3. Preparation of S2 cathode: The composite lithium-supplementing flame-retardant material of Comparative Example 3 was mixed with ternary 8-series cathode (NCM811), binder PVDF, conductive carbon powder super P (SP), and conductive carbon nanotubes (CNTs) in a mass ratio of 4.5:92.5:1.4:1.5:0.1, and then coated with N-methylpyrrolidone (NMP) as a solvent. The areal load of NCM811 was 13.9 mg·cm³. -2 The surface capacity is 3mAh·cm³. -2 .

[0054] Preparation of S3 negative electrode: The graphite negative electrode, matched with the positive electrode, has a surface loading of 9.4 mg·cm³. -2 The surface capacity is 3.3 mAh·cm³. -2 The negative electrode formulation has a mass ratio of graphite (Gr):SP:carboxymethyl cellulose (CMC):styrene-butadiene rubber (SBR) = 95.8:0.9:1.5:1.8, with water used as a solvent during the mixing and coating process.

[0055] S4 Battery Assembly: After drying the above positive and negative electrode sheets, cut them to dimensions of 60mm x 114mm and 63mm x 117mm respectively, and assemble them using a stacking method to create a 5000mAh battery, similar to Comparative Example 3. The positive electrode has 12 layers, and the negative electrode has 13 layers.

[0056] The batteries in the above embodiments and comparative examples were subjected to performance tests and nail penetration tests. The performance test batteries were tested at a temperature of 25°C, with a charge / discharge voltage range of 3V to 4.2V. The nail penetration test involved inserting a 5mm steel needle through the center of the battery cell and retaining the needle inside for 5 minutes. The battery cell was considered to have passed the test if it did not smoke, catch fire, or explode; otherwise, it failed the nail penetration test.

[0057] The test results are shown in Table 1 below.

[0058] Table 1

[0059] As can be seen from the table above, the lithium replenishing agent component in the composite lithium replenishing flame retardant material of this embodiment decomposes under a certain voltage, forming lithium ions, which improves the charging and discharging efficiency and rate performance of the battery; the nano-silica particles that encapsulate the active component NCM811 hinder the release of active oxygen from the ternary material during needle puncture, thus preventing the chain reaction during needle puncture and protecting battery safety.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite lithium-supplemented flame-retardant material, characterized in that, The preparation method includes the following steps: S1: Preparation of lithium replenishing agent solution: Add lithium replenishing agent powder to solvent and stir until uniform; S2: Adsorption and recombination: Add nano-silica to the solution in step S1, stir evenly, and let it stand for adsorption; S3: Post-processing: Filter the product obtained in step S2, collect the solid product and dry it to obtain the composite lithium-supplemented flame retardant material.

2. The preparation method of the composite lithium-supplemented flame-retardant material as described in claim 1, characterized in that: The mass ratio of the lithium supplement powder to the nano-silica is (0.5~2):

1.

3. The preparation method of the composite lithium-supplemented flame-retardant material as described in claim 1, characterized in that: The lithium supplement is selected from at least one of lithium oxalate, lithium formate, lithium tartrate, and lithium citrate.

4. The preparation method of the composite lithium-supplemented flame-retardant material as described in claim 1, characterized in that: The solvent is deionized water and / or an organic solvent, and the mass ratio of the lithium supplement to the solvent is 1:(1~100).

5. The preparation method of the composite lithium-supplemented flame-retardant material as described in claim 1, characterized in that: The nano-silica has a particle size of 10nm~1000nm and a specific surface area of ​​100m². 2 / g~3000m 2 / g.

6. The preparation method of the composite lithium-supplemented flame-retardant material as described in claim 5, characterized in that: The particle size of the nano-silica is 10nm~500nm.

7. A method for preparing a composite lithium-supplemented flame-retardant material according to any one of claims 1 to 6, characterized in that: In step S2, the static adsorption is carried out at room temperature for 6 to 24 hours.

8. A method for preparing a composite lithium-supplemented flame-retardant material according to any one of claims 1 to 6, characterized in that: The drying temperature in step S3 is 60℃~120℃.

9. A composite lithium-supplemented flame-retardant material, characterized in that: The composite lithium-supplemented flame retardant material is prepared by the preparation method of a composite lithium-supplemented flame retardant material as described in any one of claims 1 to 8.

10. The application of the composite lithium-replenishing flame-retardant material as described in claim 9 in the positive electrode of a battery, characterized in that: The composite lithium-replenishing flame-retardant material has a mass ratio of 0.1% to 15% in the battery cathode material.

Images