A process for the production of MOFs coated lithium battery separators

Abstract

The present application relates to the field of electrochemistry, in particular to a production process of MOFs coated lithium battery diaphragm, the production process comprises the following steps (1) preparation of MOFs (2) preparation of coating slurry (3) preparation of coating, the functional groups on the surface of the MOFs of the present application are more abundant because they are not subjected to high-temperature annealing, which can better affinity electrolyte, and through the esterification reaction between dihydroxy acetone and the carboxyl groups on the surface of MOFs and carboxyl butadiene styrene rubber, not only reduces the pore size of the accumulated pores between MOFs and the gap between MOFs and butadiene styrene rubber, but also introduces carbonyl groups, which have good affinity for carbonyl electrolyte, and suitable pore size adjustment further reduces the generation of lithium dendrites and improves the cycle stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a production process for MOFs-coated lithium battery separators. Background Technology

[0002] Lithium-ion rechargeable batteries, as a mainstream energy storage tool, have become the best choice for power energy. With the expansion of their application and the popularization of new energy electric vehicles, the demand for lithium batteries is constantly rising, and the requirements for them are gradually increasing. As the number of lithium battery-powered vehicles on the road increases, safety accidents involving electric vehicles have been reported repeatedly, thus safety issues are increasingly affecting public acceptance of electric vehicles. Among the components of lithium batteries, the separator's main function is to prevent short circuits between the positive and negative electrodes, while also providing a channel for lithium ion transport. It plays a crucial role in the safety and normal operation of the lithium battery; therefore, the improvement of lithium battery safety performance has led to increasingly higher requirements for the separator.

[0003] Ceramic-coated separators are currently the most widely used lithium-ion battery separator material. Their high hardness and high liquid absorption rate ensure battery safety and reduce battery impedance, thus better guaranteeing battery performance. However, existing ceramic separators on the market also have some problems: due to the inorganic functional groups on their surface, ceramic separators still have poor compatibility in electrolytes containing both inorganic and organic substances. This means that there is still considerable room for improvement in their wettability and liquid absorption rate, and it is difficult to prevent the growth of lithium dendrites, resulting in poor cycle stability. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a production process for MOFs-coated lithium battery separators to improve the electrolyte affinity and cycle stability of lithium battery separators.

[0005] To achieve the above objectives, the present invention provides a manufacturing process for MOFs-coated lithium battery separators, comprising the following steps:

[0006] S1: Add zinc acetate dihydrate to N,N-dimethylformamide and stir at room temperature for 30-60 min to obtain zinc acetate dihydrate solution;

[0007] S2: Add terephthalic acid to N,N-dimethylformamide and stir at room temperature for 20-40 min. Then add it dropwise to the above zinc acetate dihydrate solution. After the addition is complete, stir at room temperature for 24-36 h. Finally, centrifuge, wash, and dry under vacuum at 50-60℃ for 3-5 h to obtain MOF-5.

[0008] S3: Add carboxylated styrene-butadiene rubber and catalyst to water, stir for 20-35 minutes to obtain catalytic binder solution;

[0009] S4: Add MOF-5 and dihydroxyacetone to the above catalytic binder and stir for 1-3 hours to obtain the coating slurry;

[0010] S5: Coating slurry is applied to the surface of the separator substrate, reacted at 75-85℃ for 5-10 hours, washed with water 3-5 times, and dried at 65-75℃ for 12-24 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0011] Preferably, in step S1, the mass ratio of zinc acetate dihydrate to N,N-dimethylformamide is 1-3:40-120.

[0012] Preferably, in step S2, the mass ratio of terephthalic acid to N,N-dimethylformamide is 0.3-0.9:20-60.

[0013] Preferably, the carboxylated styrene-butadiene rubber in step S3 is carboxylated styrene-butadiene latex PC-756.

[0014] Preferably, the catalyst in step S3 is one of concentrated sulfuric acid, concentrated hydrochloric acid, and benzoic acid.

[0015] Preferably, in step S3, the mass ratio of carboxylated styrene-butadiene rubber, catalyst, and water is 5-15:0.1-0.3:100-200.

[0016] Preferably, in step S4, the mass ratio of MOF-5 to dihydroxyacetone is 50-80:4-9.

[0017] Preferably, the membrane substrate is one or more porous membranes selected from polypropylene, polyethylene, polymethylpentene, polyimide, and nonwoven fabric, with a pore size of 50-100 nm, a thickness of 10-30 μm, and a porosity of 40-50%.

[0018] Preferably, the thickness of the coating is 1-3 μm.

[0019] Preferably, the MOFs-coated lithium battery separator is obtained according to the above-mentioned production process of MOFs-coated lithium battery separator.

[0020] The beneficial effects of this invention are:

[0021] The functional groups on the surface of the MOFs of the present invention are more abundant because they have not undergone high-temperature annealing, which can better bind to the electrolyte. Furthermore, through the esterification reaction between dihydroxyacetone and carboxyl groups and carboxyl styrene-butadiene rubber on the MOFs surface, not only is the pore size of the stacking pores between MOFs and the gap between MOFs and styrene-butadiene rubber reduced, but carbonyl groups are also introduced, which have good affinity for carbonyl electrolytes. Appropriate pore size adjustment also further reduces the formation of lithium dendrites and improves cycle stability.

[0022] The secondary structure of the MOFs of this invention provides a very large surface area for contact with the electrolyte. At the same time, the secondary structure prevents material collapse and avoids small particles from clogging the membrane pores. In addition, its hollow structure provides more space for the electrolyte, allowing it to absorb more electrolyte and thus providing more pathways and channels for lithium ion transport. Finally, the esterification reaction consumes some of the carboxyl groups on the surface of the MOFs, exposing more metal sites and promoting lithium ion transport. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this 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 only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the production process of a MOFs-coated lithium battery separator according to the present invention.

[0025] Figure 2 This is a transmission electron microscope image of MOF-5 in Example 1 of the present invention;

[0026] Figure 3 This is a scanning electron microscope image of MOF-5 in Embodiment 1 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] The membrane substrates used in Examples 1-3 and Comparative Examples 1-3 of this invention are all polypropylene porous membranes with a pore size of 80 nm, a thickness of 15 μm, and a porosity of 46%.

[0029] Example 1

[0030] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0031] S1: Add 1g of zinc acetate dihydrate to 40g of N,N-dimethylformamide and stir for 30min at room temperature to obtain a zinc acetate dihydrate solution;

[0032] S2: Add 0.3g of terephthalic acid to 20g of N,N-dimethylformamide and stir at room temperature for 20min. Then add it dropwise to the above zinc acetate dihydrate solution. After the addition is complete, stir at room temperature for 24h. Finally, centrifuge, wash, and dry under vacuum at 50℃ for 3h to obtain MOF-5.

[0033] S3: Add 5g of carboxylated styrene-butadiene latex PC-756 and 0.1g of concentrated sulfuric acid to water, stir for 20 minutes to obtain a catalytic binder solution;

[0034] S4: Add 50g MOF-5 and 4g dihydroxyacetone to the above catalytic binder and stir for 1 hour to obtain the coating slurry;

[0035] S5: The coating slurry is coated onto the surface of the separator substrate, reacted at 75°C for 5 hours, washed with water 3 times, and dried at 65°C for 12 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0036] Example 2

[0037] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0038] S1: Add 2g of zinc acetate dihydrate to 80g of N,N-dimethylformamide and stir for 45min at room temperature to obtain a zinc acetate dihydrate solution;

[0039] S2: Add 0.6g of terephthalic acid to 40g of N,N-dimethylformamide and stir at room temperature for 30min. Then add it dropwise to the above zinc acetate dihydrate solution. After the addition is complete, stir at room temperature for 24-36h. Finally, centrifuge, wash, and dry under vacuum at 55℃ for 4h to obtain MOF-5.

[0040] S3: Add 10g of carboxylated styrene-butadiene latex PC-756 and 0.2g of concentrated sulfuric acid to water, stir for 27 minutes to obtain a catalytic binder solution;

[0041] S4: Add 65g MOF-5 and 6.5g dihydroxyacetone to the above catalytic binder and stir for 2 hours to obtain the coating slurry;

[0042] S5: The coating slurry is coated onto the surface of the separator substrate, reacted at 80°C for 8 hours, washed with water 4 times, and dried at 70°C for 18 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0043] Example 3

[0044] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0045] S1: Add 3g of zinc acetate dihydrate to 120g of N,N-dimethylformamide and stir for 60min at room temperature to obtain a zinc acetate dihydrate solution;

[0046] S2: Add 0.9g of terephthalic acid to 60g of N,N-dimethylformamide and stir at room temperature for 40min. Then add it dropwise to the above zinc acetate dihydrate solution. After the addition is complete, stir at room temperature for 36h. Finally, centrifuge, wash, and dry under vacuum at 60℃ for 5h to obtain MOF-5.

[0047] S3: Add 15g of carboxylated styrene-butadiene latex PC-756 and 0.3g of concentrated sulfuric acid to water, stir for 35 minutes to obtain a catalytic binder solution;

[0048] S4: Add 80g MOF-5 and 9g dihydroxyacetone to the above catalytic binder and stir for 3 hours to obtain the coating slurry;

[0049] S5: The coating slurry is coated onto the surface of the separator substrate, reacted at 85°C for 10 hours, washed with water 5 times, and dried at 75°C for 24 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0050] Comparative Example 1

[0051] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0052] S1: Same as Example 2;

[0053] S2: Same as Example 2;

[0054] S3: Same as Example 2;

[0055] S4: Add 65g MOF-5 to the above catalytic binder solution and stir for 2 hours to obtain the coating slurry;

[0056] S5: The coating slurry is coated onto the surface of the separator substrate, dried at 80°C for 8 hours, washed with water 4 times, and then dried at 70°C for 18 hours to obtain a lithium battery separator.

[0057] Comparative Example 2

[0058] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0059] S1: Same as Example 2;

[0060] S2: Same as Example 2;

[0061] S3: Add 10g of styrene-butadiene latex and 0.2g of concentrated sulfuric acid to water, stir for 27 minutes to obtain a catalytic binder solution;

[0062] S4: Add 65g MOF-5 and 6.5g dihydroxyacetone to the above catalytic binder and stir for 2 hours to obtain the coating slurry;

[0063] S5: The coating slurry is coated onto the surface of the separator substrate, reacted at 80°C for 8 hours, washed with water 4 times, and dried at 70°C for 18 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0064] Comparative Example 3

[0065] A manufacturing process for MOFs-coated lithium battery separators includes the following steps:

[0066] S1: Same as Example 2;

[0067] S2: Same as Example 2;

[0068] S3: Same as Example 2;

[0069] S4: Add 65g of zirconium oxide particles and 6.5g of dihydroxyacetone to the above catalytic binder and stir for 2 hours to obtain the coating slurry;

[0070] S5: The coating slurry is coated onto the surface of the separator substrate, reacted at 80°C for 8 hours, washed with water 4 times, and dried at 70°C for 18 hours to obtain a MOFs-coated lithium battery separator containing a coating.

[0071] Experimental tests of Examples 1-3 and Comparative Examples 1-3

[0072] Thermal stability test: The polypropylene porous membrane and the diaphragms prepared in the examples and comparative examples were cut into 10mm×10mm sizes and kept in a nitrogen atmosphere at a gradient temperature of 120℃, 140℃, 160℃, 180℃, 200℃, 220℃ and 240℃ for 1h. The morphological changes of the diaphragms were observed and the results are shown in Table 1.

[0073] Liquid absorption rate and conductivity test: The electrolyte was made by dissolving 1M LiPF6 in (ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio 1:1:1)). The mass of the dried membrane of the example and the comparative example was weighed. The membrane was placed in the electrolyte and weighed after absorption saturation. The liquid absorption rate was calculated and the results are shown in Table 1. The conductivity of the membrane with sufficient liquid electrolyte was tested using an electrochemical workstation and the results are shown in Table 1.

[0074] Porosity and pore size tests: The average pore size of the membrane coatings of the examples and comparative examples was measured by a specific surface area analyzer, and the porosity of the membranes of the examples and comparative examples was measured by the immersion n-butanol absorption method. The results are shown in Table 1.

[0075] Table 1. Test results of diaphragm performance in Examples 1-3 and Comparative Examples 1-3

[0076]

[0077] Data analysis shows from Examples 1-3 above that the separator produced using the manufacturing process of this invention has significant thermal stability, high electrolyte absorption rate, high porosity and suitable pore size. Smaller pore size and higher porosity can reduce lithium dendrite formation during lithium-ion battery operation and improve battery life and stability.

[0078] Electrochemical performance test: The separator prepared in Example 2 and the separator prepared in the comparative example were used to make soft-pack lithium-ion battery chips using the same process. The electrolyte was 1M LiPF6 dissolved in (ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio 1:1:1)). The electrolyte was tested for 500 cycles using a constant current discharge of 1.0C. The test results are shown in Table 2.

[0079] Table 2. Battery performance test results for the separators prepared in Examples 2 and Comparative Examples 1-3.

[0080]

[0081] Data analysis shows from Example 2 above that the battery prepared using the separator produced by the manufacturing process of this invention still has a capacity retention rate of 96.3% after 500 cycles.

[0082] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0083] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A manufacturing process for MOFs-coated lithium battery separators, characterized in that, Includes the following steps: S1: Add zinc acetate dihydrate to N,N-dimethylformamide and stir at room temperature for 30-60 min to obtain zinc acetate dihydrate solution; S2: Add terephthalic acid to N,N-dimethylformamide and stir at room temperature for 20-40 min. Then add it dropwise to the above zinc acetate dihydrate solution. After the addition is complete, stir at room temperature for 24-36 h. Finally, centrifuge, wash, and dry under vacuum at 50-60℃ for 3-5 h to obtain MOF-5. S3: Add carboxylated styrene-butadiene rubber and catalyst to water, stir for 20-35 minutes to obtain catalytic binder solution; S4: Add MOF-5 and dihydroxyacetone to the above catalytic binder and stir for 1-3 hours to obtain the coating slurry; S5: Coating slurry is applied to the surface of the separator substrate, reacted at 75-85℃ for 5-10 hours, washed with water 3-5 times, and dried at 65-75℃ for 12-24 hours to obtain a MOFs-coated lithium battery separator containing a coating.

2. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, In step S1, the mass ratio of zinc acetate dihydrate to N,N-dimethylformamide is 1-3:40-120.

3. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, In step S2, the mass ratio of terephthalic acid to N,N-dimethylformamide is 0.3-0.9:20-60.

4. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, In step S3, the carboxylated styrene-butadiene rubber is carboxylated styrene-butadiene latex PC-756.

5. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, The catalyst in step S3 is one of concentrated sulfuric acid, concentrated hydrochloric acid, and benzoic acid.

6. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, In step S3, the mass ratio of carboxylated styrene-butadiene rubber, catalyst, and water is 5-15:0.1-0.3:100-200.

7. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, In step S4, the mass ratio of MOF-5 to dihydroxyacetone is 50-80:4-9.

8. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, The membrane substrate is one or more porous membranes selected from polypropylene, polyethylene, polymethylpentene, polyimide, and nonwoven fabric, with a pore size of 50-100 nm, a thickness of 10-30 μm, and a porosity of 40-50%.

9. The manufacturing process for a MOFs-coated lithium battery separator according to claim 1, characterized in that, The coating has a thickness of 1-3 μm.

10. A MOFs-coated lithium battery separator, characterized in that, The MOFs-coated lithium battery separator is obtained by a manufacturing process according to any one of claims 1-9.

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