Core-shell structure waterborne polyurethane microsphere dispersion and preparation method thereof, lithium ion battery diaphragm and preparation method thereof

Abstract

The invention provides a core-shell structure waterborne polyurethane microsphere dispersion and a preparation method thereof, and a lithium ion battery diaphragm and a preparation method thereof. The preparation method comprises the following steps: (1) uniformly mixing 12-24 parts by weight of isocyanate, 5-10 parts by weight of macromolecular polyol, 5-10 parts by weight of soft segment diol and 0.5-7 parts by weight of hydrophilic monomer, and reacting at 65-75 DEG C for 2-4 hours; (2) adding 0.01-0.1 part of a catalyst and 10-20 parts of micromolecular polyol, and reacting at 70-80 DEG C until NCO is 0; (3) adding 50-200 parts of butanone, cooling to 30-40 DEG C, adding 35-300 parts of a polyisocyanate crosslinking monomer, and uniformly mixing; (4) adding 0.5-6 parts of a neutralizing agent into the prepolymer, neutralizing for 30 minutes, transferring to a dispersion cylinder, adding 220-320 parts of deionized water into the dispersion cylinder, dispersing for 30 minutes at the speed of 1500 rpm, heating to 60-70 DEG C, and reacting for 3-7 hours; and (5) carrying out reduced pressure distillation to remove butanone, adjusting the solid content to 30 + / -1%, filtering and discharging. The lithium ion battery diaphragm adopting the polyurethane microsphere dispersion can improve the cycle life, the rate capability and the energy density of the lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, specifically relating to a core-shell structured aqueous polyurethane microsphere dispersion and its preparation method, and a lithium-ion battery separator and its preparation method. Background Technology

[0002] Currently, commercially available lithium-ion battery separators primarily use polypropylene and polyethylene. However, as performance requirements for lithium-ion batteries increase, these two materials alone are insufficient, necessitating the application of coatings to improve performance. Commercially available separator coatings typically use solvent-based or water-based polymers. Solvent-based systems often require non-environmentally friendly solvents such as NMP. With increasingly stringent environmental regulations, solvent-based systems will face greater constraints from environmental laws and costs, requiring integrated solvent recovery systems, which are costly and negatively impact competitiveness.

[0003] Aqueous polymers use deionized water as the dispersion medium, offering advantages such as low cost and environmental friendliness. However, currently commercially available aqueous polymer materials for separator coatings, such as PVDF and PMMA, are rigid but lack elasticity. As the number of cycles increases, they cannot absorb or mitigate the volume expansion of the negative electrode (especially silicon-doped negative electrode systems) caused by the insertion and extraction of lithium ions during charge and discharge, resulting in insufficient interfacial stability and even delamination. These limitations restrict further improvements in lithium-ion battery performance. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a core-shell structured aqueous polyurethane microsphere dispersion and its preparation method, as well as a lithium-ion battery separator and its preparation method. The polyurethane microsphere dispersion is a core-shell structure in which a hydrophilic polyurethane shell encapsulates a hydrophobic polyisocyanate crosslinked monomer core. Lithium-ion battery separators using this polyurethane microsphere dispersion can improve the liquid absorption and retention properties of the interface, ensure interface stability, enhance the ion transport capacity of the interface, and improve the cycle life, rate performance, and energy density of lithium-ion batteries.

[0005] To achieve the above objectives, the present invention provides a method for preparing a core-shell structured aqueous polyurethane microsphere dispersion, comprising the following steps: (1) mixing 12-24 parts by weight of isocyanate, 5-10 parts by weight of macromolecular polyol, 5-10 parts by weight of soft segment diol, and 0.5-7 parts by weight of hydrophilic monomer, and reacting at 65-75°C for 2-4 hours; (2) adding 0.01-0.1 parts by weight of catalyst and 10-20 parts by weight of small molecule polyol, and reacting at 70-80°C until NCO is 0; (3) adding butanone. Add 50-200 parts and cool to 30-40℃, add 35-300 parts of polyisocyanate crosslinking monomer, and mix evenly; (4) Add 0.5-6 parts of neutralizing agent to the prepolymer and neutralize for 30 min, transfer to the dispersion tank, add 220-320 parts of deionized water to the dispersion tank, disperse at 1500 rpm for 30 min, and heat to 60-70℃ to react for 3-7 h; (5) Remove butanone by vacuum distillation, adjust the solid content to 30±1%, filter and discharge to obtain a core-shell structured waterborne polyurethane microsphere dispersion.

[0006] Optionally, the isocyanate is at least one selected from isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), and diphenylmethane diisocyanate (MDI).

[0007] Optionally, the macromolecular polyol is at least one of polycarbonate diol (molecular weight 1000-3000) and polyester diol (molecular weight 1000-3000).

[0008] Optionally, the soft segment glycol is at least one of polyethylene glycol 1000 (PEG 1000), polyethylene glycol 2000 (PEG 2000), polypropylene glycol 1000 (PPG 1000), and polypropylene glycol 2000 (PPG 2000).

[0009] Optionally, the hydrophilic monomer is at least one of dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA).

[0010] Optionally, the small molecule polyol is at least one of trimethylolpropane (TMP), 1,4-butanediol (BDO), and neopentyl glycol (NPG).

[0011] Optionally, the polyisocyanate crosslinking monomer is at least one of HDI trimer, HDI biuret, IPDI trimer, and TDI trimer.

[0012] Optionally, the catalyst is at least one of Vantrus 8330R and AC83.

[0013] Optionally, the neutralizing agent is at least one of triethylamine (TEA) and N,N-dimethylethanolamine (DMEA).

[0014] The present invention also provides a core-shell structured aqueous polyurethane microsphere dispersion prepared according to the above preparation method.

[0015] The present invention also provides a lithium-ion battery separator comprising the above-mentioned core-shell structured aqueous polyurethane microsphere dispersion.

[0016] The present invention also provides a method for preparing a lithium-ion battery separator, comprising the following steps: adding a nonionic surfactant, a binder, a thickener, and a wetting agent to the above-mentioned core-shell structured aqueous polyurethane microsphere dispersion, and stirring thoroughly to obtain a coating slurry; coating the coating slurry onto the separator, and drying to obtain a lithium-ion battery separator.

[0017] Optionally, the mass ratio of the aqueous polyurethane microsphere dispersion, surfactant, binder, thickener, and wetting agent is 270:1:8:1:1.

[0018] The present invention also provides a lithium-ion battery, including the above-described lithium-ion battery separator.

[0019] Optionally, the positive electrode of the lithium-ion battery is NCM811, the negative electrode is silicon-carbon negative electrode, and the electrolyte is lithium-ion secondary electrolyte (LB-107).

[0020] The advantages and beneficial effects of this invention are as follows:

[0021] (1) The present invention prepares an aqueous polyurethane microsphere dispersion with a core-shell structure and a core-shell ratio (by weight) of 50:50 to 90:10: First, a hydrophilic polyurethane shell containing hydroxyl groups is synthesized, then a polyisocyanate crosslinking monomer is introduced, and the mixture is emulsified and dispersed in water to self-assemble into a microsphere structure. Then, in-situ polymerization is carried out to connect and solidify the core-shell structure through chemical bonds to form a polyurethane microsphere dispersion with a core-shell structure in which a hydrophilic polyurethane shell encapsulates a hydrophobic polyisocyanate crosslinking monomer core. The microsphere size is 1 to 5 μm.

[0022] (2) The polyurethane microsphere dispersion of the present invention has a rigid cross-linked structure in the core of the microspheres, which has good heat resistance and does not collapse after being heated. It also has good solvent resistance and is not dissolved by the electrolyte. When subjected to external compression, it does not undergo significant deformation and can form a polyurethane microsphere stacking structure with high porosity and high specific surface area. This results in a certain gap between the diaphragm and the positive and negative electrode plates, ensuring sufficient liquid retention performance at the interface between the diaphragm and the positive and negative electrodes, ensuring the stability of the interface, and improving the ion transport capacity of the interface.

[0023] (3) The polyurethane microsphere dispersion of the present invention contains a large number of urethane polar groups in the shell molecular structure of the microspheres, which have good electrolyte affinity. The good electrolyte affinity of the shell can enable the electrolyte to wet and diffuse well at the interface between the separator and the electrode, and improve the electrolyte retention performance at the interface. Moreover, the flexible long-chain structure of the shell has good resilience characteristics, which can absorb and alleviate the volume expansion of the negative electrode (especially the silicon-doped negative electrode system) during battery charging and discharging due to the insertion and extraction of lithium ions, reduce internal stress, maintain the integrity and stability of the electrode interface structure, and improve the cycle life, rate performance and energy density of lithium-ion batteries. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the embodiments.

[0025] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0026] The preparation method of the core-shell structured aqueous polyurethane microsphere dispersion according to the present invention includes the following steps: (1) according to the weight parts, 12-24 parts of isocyanate, 5-10 parts of macromolecular polyol, 5-10 parts of soft segment diol, and 0.5-7 parts of hydrophilic monomer are mixed evenly and reacted at 65-75°C for 2-4 hours; (2) 0.01-0.1 parts of catalyst and 10-20 parts of small molecule polyol are added and reacted at 70-80°C until NCO is 0; (3) 50-200 parts of butanone are added. (3) Add 35-300 parts of polyisocyanate crosslinking monomer to the prepolymer and cool it to 30-40℃, mix it evenly; (4) Add 0.5-6 parts of neutralizing agent to the prepolymer and neutralize for 30 min, transfer it to the dispersion tank, add 220-320 parts of deionized water to the dispersion tank, disperse at 1500 rpm for 30 min, and heat to 60-70℃ to react for 3-7 h; (5) Remove butanone by vacuum distillation, adjust the solid content to 30±1%, filter and discharge to obtain a core-shell structured aqueous polyurethane microsphere dispersion. The isocyanate can be at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), and diphenylmethane diisocyanate (MDI). The macromolecular polyol may be at least one of polycarbonate diol (molecular weight 1000-3000) and polyester diol (molecular weight 1000-3000). The soft segment diol may be at least one of polyethylene glycol 1000 (PEG 1000), polyethylene glycol 2000 (PEG 2000), polypropylene glycol 1000 (PPG 1000), and polypropylene glycol 2000 (PPG 2000). The hydrophilic monomer may be at least one of dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA). The small molecule polyol may be at least one of trimethylolpropane (TMP), 1,4-butanediol (BDO), and neopentyl glycol (NPG). The polyisocyanate crosslinking monomer may be at least one of HDI trimer, HDI biuret, IPDI trimer, and TDI trimer. The catalyst may be at least one of Vantrus 8330R and AC83. The neutralizing agent may be at least one of triethylamine (TEA) and N,N-dimethylethanolamine (DMEA).

[0027] The core-shell structured aqueous polyurethane microsphere dispersion according to the present invention was prepared according to the above preparation method.

[0028] The lithium-ion battery separator according to the present invention comprises the above-described core-shell structured aqueous polyurethane microsphere dispersion.

[0029] The method for preparing a lithium-ion battery separator according to the present invention includes the following steps: adding a nonionic surfactant, a binder, a thickener, and a wetting agent to the above-mentioned core-shell structured aqueous polyurethane microsphere dispersion, and stirring thoroughly to obtain a coating slurry; coating the coating slurry onto a separator, and drying to obtain a lithium-ion battery separator. The mass ratio of the aqueous polyurethane microsphere dispersion, surfactant, binder, thickener, and wetting agent can be 270:1:8:1:1.

[0030] The lithium-ion battery according to the present invention includes the above-described lithium-ion battery separator. In one embodiment, the positive electrode of the lithium-ion battery may be NCM811, the negative electrode may be a silicon-carbon negative electrode, and the electrolyte may be a lithium-ion secondary electrolyte (LB-107).

[0031] The following description is based on specific embodiments. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all conventional commercially available raw materials, and the process methods used are all conventional methods in the art.

[0032] Example 1

[0033] (1) By weight, 18 parts of isophorone diisocyanate (IPDI), 7 parts of polycarbonate diol (molecular weight 2000), 8 parts of polyethylene glycol 1000 (PEG 1000), and 4 parts of dimethylolpropionic acid (DMPA) are mixed evenly and reacted at 70°C for 3 hours.

[0034] (2) Add 0.05 parts of catalyst 8330R and 15 parts of trimethylolpropane (TMP), and react at 75°C until NCO is 0;

[0035] (3) Add 120 parts of butanone and cool to 35°C, add 100 parts of HDI trimer and mix well;

[0036] (4) Add 3 parts of triethylamine (TEA) to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 270 parts of deionized water, disperse at 1500 rpm for 30 min, and heat to 65℃ to react for 6 h.

[0037] (5) Remove butanone by vacuum distillation, adjust the solid content to 30%, filter the material to obtain a microsphere dispersion with a particle size of 1.5 μm.

[0038] Example 2

[0039] (1) By weight, 12 parts of toluene diisocyanate (TDI), 10 parts of diphenylmethane diisocyanate (MDI), 5 parts of polyester glycol (molecular weight 1500), 10 parts of polypropylene glycol 2000 (PPG 2000) and 0.5 parts of dimethylolbutyric acid (DMBA) are mixed evenly and reacted at 65°C for 4 hours.

[0040] (2) Add 0.01 parts of catalyst AC83 and 20 parts of 1,4-butanediol (BDO), and react at 70°C until NCO is 0;

[0041] (3) Add 200 parts of butanone and cool to 40°C, add 35 parts of TDI trimer and mix well;

[0042] (4) Add 0.5 parts of N,N-dimethylethanolamine (DMEA) to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 320 parts of deionized water, disperse at 1500 rpm for 30 min, and heat to 60℃ to react for 3 h.

[0043] (5) Remove butanone by vacuum distillation, adjust the solid content to 30%, filter the material to obtain a microsphere dispersion with a particle size of 1.3 μm.

[0044] Example 3

[0045] (1) According to the weight parts, 15 parts of 4,4'-dicyclohexylmethane diisocyanate (HMDI), 9 parts of hexamethylene diisocyanate (HDI), 10 parts of polycarbonate diol (molecular weight 1000), 5 parts of polyethylene glycol 2000 (PEG 2000), and 7 parts of dimethylolpropionic acid (DMPA) are mixed evenly and reacted at 75°C for 2 hours;

[0046] (2) Add 0.1 parts of catalyst 8330R, 10 parts of neopentyl glycol (NPG) and 5 parts of 1,4-butanediol (BDO), and react at 80°C until NCO is 0;

[0047] (3) Add 50 parts of butanone and cool to 30°C, add 300 parts of IPDI trimer and mix well;

[0048] (4) Add 6 parts of triethylamine (TEA) to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 220 parts of deionized water, disperse at 1500 rpm for 30 min, and heat to 70℃ to react for 7 h.

[0049] (5) Remove butanone by vacuum distillation, adjust the solid content to 30%, filter the material to obtain microsphere dispersion with a particle size of 4.8 μm.

[0050] Example 4

[0051] (1) By weight, 12 parts of isophorone diisocyanate (IPDI), 6 parts of polyester glycol (molecular weight 3000), 7 parts of polypropylene glycol 1000 (PPG 1000) and 2 parts of dimethylolbutyric acid (DMBA) are mixed evenly and reacted at 68°C for 3.5 h.

[0052] (2) Add 0.03 parts of catalyst AC83, 8 parts of trimethylolpropane (TMP) and 7 parts of 1,4-butanediol (BDO), and react at 72°C until NCO is 0;

[0053] (3) Add 150 parts of butanone and cool to 38°C, then add 150 parts of HDI biuret and mix well;

[0054] (4) Add 2 parts of N,N-dimethylethanolamine (DMEA) to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 300 parts of deionized water, disperse at 1500 rpm for 30 min, and heat to 63℃ to react for 5.5 h.

[0055] (5) Remove butanone by vacuum distillation, adjust the solid content to 30%, filter the material to obtain microsphere dispersion with a particle size of 2.2 μm.

[0056] Example 5

[0057] (1) By weight, 24 parts of hexamethylene diisocyanate (HDI), 8 parts of polycarbonate diol (molecular weight 2000), 5 parts of polypropylene glycol 2000 (PPG 2000), 5 parts of polyethylene glycol 1000 (PEG 1000), 3 parts of dimethylolpropionic acid (DMPA), and 2 parts of dimethylolbutyric acid (DMBA) are mixed evenly and reacted at 75°C for 2.5 h.

[0058] (2) Add 0.02 parts of catalyst 8330R, 0.03 parts of AC83, 5 parts of trimethylolpropane (TMP), and 10 parts of neopentyl glycol (NPG), and react at 78°C until NCO is 0;

[0059] (3) Add 180 parts of butanone and cool to 32°C, add 100 parts of HDI trimer and 100 parts of IPDI trimer, and mix well;

[0060] (4) Add 2 parts of triethylamine (TEA) and 2 parts of N,N-dimethylethanolamine (DMEA) to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 280 parts of deionized water, disperse at 1500 rpm for 30 min, and heat to 68℃ to react for 5.5 h.

[0061] (5) Remove butanone by vacuum distillation, adjust the solid content to 30%, filter the material to obtain a microsphere dispersion with a particle size of 3.7 μm.

[0062] Comparative Example 1

[0063] Arkema's LBG series PVDF microspheres were used instead of polyurethane microspheres, with a microsphere size of 1.5 μm.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that, instead of using soft segment glycol polyethylene glycol 1000 (PEG 1000), polycarbonate glycol (molecular weight 1000) is used.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that HMDI trimer, a polyisocyanate crosslinking monomer, is not used; instead, HMDI with an equal NCO value is used.

[0068] The microsphere dispersions prepared in Examples 1-5 and Comparative Examples 1-3 were mixed with nonionic surfactant Disponil A 3065, binder polyacrylate emulsion, thickener sodium carboxymethyl cellulose, and wetting agent polyether-modified silicone oil, and stirred thoroughly to prepare a coating slurry. This slurry was then coated onto a separator using a gravure coating process and dried to obtain a lithium-ion battery separator. The mass ratio of the aqueous polyurethane microsphere dispersion, surfactant, binder, thickener, and wetting agent was 270:1:8:1:1.

[0069] The prepared lithium-ion battery separator was subjected to the following performance tests, and the test methods are as follows:

[0070] 1. Liquid absorption rate test:

[0071] Cut a 30×30mm diaphragm sample and dry it in a vacuum oven at 60℃ until constant weight (mass M0);

[0072] Immerse in electrolyte and let stand at 25°C for 8 hours;

[0073] After removing it, use filter paper to absorb the residual liquid on the surface and weigh it immediately (mass M1);

[0074] Calculate the absorption rate: Absorption rate (%) = [(M1-M0) / M0] × 100%.

[0075] 2. Air permeability test: conducted in accordance with GB / T 36363-2018.

[0076] 3. Lithium-ion conductivity test: conducted in accordance with GB / T 36363-2018.

[0077] 4. Rate performance test: The test shall be conducted in accordance with the methods specified in the national standard GB / T31486-2015 "Electrical performance requirements and test methods for power batteries for electric vehicles".

[0078] 5. Cyclic performance test: The test shall be conducted in accordance with the methods specified in the national standard GB / T31484-2015 "Requirements and test methods for cycle life of power batteries for electric vehicles".

[0079] The performance test results of the lithium-ion battery separator are shown in Table 1.

[0080] Table 1. Test results of lithium-ion battery separator performance

[0081]

[0082] Compared to Example 1, Comparative Example 1 used PVDF microspheres. It is evident that the ionic conductivity and rate performance are reduced. This is because PVDF has a high glass transition temperature and poor chain flexibility. It lacks the highly flexible soft segments such as PEG or PPG that can coordinate with lithium ions, making it difficult to form channels for lithium ion transport. Therefore, its lithium ion conductivity is lower than that of the polyurethane microspheres of this invention. Furthermore, PVDF microspheres are rigid microspheres, unlike the polyurethane microspheres of this invention which simultaneously possess a rigid core and an elastic soft shell. Therefore, their ability to absorb and buffer the internal stress of the negative electrode during battery charging and discharging is not as good as that of the polyurethane microspheres of this invention, resulting in a significant decrease in rate performance after multiple charge-discharge cycles.

[0083] Compared to Example 1, Comparative Example 2 shows a significant difference in lithium-ion conductivity and rate performance. This may be because Example 1 contains PEG segments, whose ether oxygen groups possess lone pairs of electrons, enabling them to form weak coordination with lithium ions. Furthermore, the PEG segments exhibit high flexibility and a low glass transition temperature, allowing lithium ions to form continuous ion transport channels through a dynamic coordination-dissociation process during conduction, which is beneficial for lithium ion transport. In contrast, the aqueous polyurethane molecular chains in Comparative Example 2 consist of relatively rigid segmental structures, lacking coordination. Their high rigidity also results in insufficient resilience, a high glass transition temperature, and difficulty in segment movement, hindering the formation of channels for lithium-ion transport. Additionally, the presence of PEG segments in Example 1, with their lower glass transition temperature compared to polycarbonate and polyester, results in better elasticity of the polyurethane microspheres compared to Comparative Example 2. This allows for the absorption and mitigation of internal stress on the negative electrode during battery charging and discharging, leading to better integrity and stability of the electrode interface structure and thus better rate performance.

[0084] Compared to Example 1, Comparative Example 3 lacked the polyisocyanate crosslinking monomer, resulting in a significant deterioration in all properties. This is because the lack of a rigid core structure makes it difficult to maintain the core-shell morphology of the polyurethane microspheres. The film-forming state of the slurry coated on the separator is fundamentally altered, making it impossible to form a soft-shell, hard-core polyurethane microsphere structure. The inability to form a polyurethane microsphere stacking structure with high porosity and high specific surface area leads to a significant decrease in the coating's specific surface area, liquid absorption rate, and air permeability, affecting lithium-ion conductivity and interfacial stability. Consequently, all properties are significantly reduced.

[0085] Matters not covered in this invention are common knowledge. The above embodiments are only for illustrating the technical concept and features of this invention, and are intended to enable those skilled in the art to understand the content of this invention and implement it accordingly. They should not be construed as limiting the scope of protection of this invention. All equivalent changes or modifications made in accordance with the spirit and essence of this invention should be covered within the scope of protection of this invention.

Claims

1. A method for preparing a core-shell structured aqueous polyurethane microsphere dispersion, characterized in that, Includes the following steps: (1) By weight, mix 12-24 parts of isocyanate, 5-10 parts of macromolecular polyol, 5-10 parts of soft segment diol and 0.5-7 parts of hydrophilic monomer evenly and react at 65-75℃ for 2-4 hours. (2) Add 0.01 to 0.1 parts of catalyst and 10 to 20 parts of small molecule polyol, and react at 70 to 80°C until NCO is 0; (3) Add 50-200 parts of butanone and cool to 30-40℃, add 35-300 parts of polyisocyanate crosslinking monomer, and mix evenly; (4) Add 0.5 to 6 parts of neutralizing agent to the prepolymer and neutralize for 30 min. Transfer to a dispersion tank, add 220 to 320 parts of deionized water to the dispersion tank, disperse at 1500 rpm for 30 min, and heat to 60 to 70℃ to react for 3 to 7 h. (5) Remove butanone by vacuum distillation, adjust the solid content to 30±1%, filter and discharge to obtain a core-shell structured aqueous polyurethane microsphere dispersion.

2. The preparation method according to claim 1, characterized in that, The isocyanate is at least one selected from isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), and diphenylmethane diisocyanate (MDI).

3. The preparation method according to claim 1, characterized in that, The macromolecular polyol is at least one of polycarbonate diol (molecular weight 1000-3000) and polyester diol (molecular weight 1000-3000).

4. The preparation method according to claim 1, characterized in that, The soft segment glycol is at least one of polyethylene glycol 1000 (PEG1000), polyethylene glycol 2000 (PEG 2000), polypropylene glycol 1000 (PPG 1000), and polypropylene glycol 2000 (PPG 2000).

5. The preparation method according to claim 1, characterized in that, The hydrophilic monomer is at least one of dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA).

6. The preparation method according to claim 1, characterized in that, The small molecule polyol is at least one of trimethylolpropane (TMP), 1,4-butanediol (BDO), and neopentyl glycol (NPG).

7. The preparation method according to claim 1, characterized in that, The polyisocyanate crosslinking monomer is at least one of HDI trimer, HDI biuret, IPDI trimer, and TDI trimer.

8. The preparation method according to claim 1, characterized in that, The catalyst is at least one of Vantrus 8330R and AC83; and / or the neutralizing agent is at least one of triethylamine (TEA) and N,N-dimethylethanolamine (DMEA).

9. A core-shell structured aqueous polyurethane microsphere dispersion prepared by any one of the preparation methods according to claims 1-8.

10. A lithium-ion battery separator, characterized in that, Includes the core-shell structured aqueous polyurethane microsphere dispersion according to claim 9.

Images