CN107611321B - Separator and Secondary Battery - Google Patents

Abstract

The invention provides a separator and a secondary battery. The separator includes a porous polymeric substrate and a coating. The coating includes ceramic particles and a binder. The ceramic particles comprise boehmite. The binder includes a compound having a reactive isocyanate functional group. The inventive separator has excellent heat resistance, and can improve the dynamic performance of secondary battery and improve the safety performance of secondary battery.

Description

Separator and Secondary Battery

technical field

The present invention relates to the field of batteries, in particular to a separator and a secondary battery.

Background technique

With the popularization of consumer electronic products and electric vehicles, the performance requirements for the secondary batteries used in these products are also getting higher and higher. For example, the secondary batteries are required to have high volume or weight energy density while maintaining It has better cycle performance and high-rate charge-discharge performance, and at the same time puts forward more stringent requirements for the safety performance of secondary batteries.

In order to meet the improvement of the energy density of the secondary battery, the thickness of the separator substrate and the thickness of the separator coating are continuously reduced, and the heat resistance of the separator is greatly challenged, which increases the safety hazard of the secondary battery. . For example, when the secondary battery is abused under high temperature conditions, the large shrinkage of the separator will lead to a short circuit of the positive and negative electrodes, which will generate more heat, and eventually lead to safety accidents such as fire and explosion of the secondary battery.

In practical use, in order to increase the heat resistance of the separator, a thicker or denser ceramic coating is usually applied on the substrate and a larger amount of a binder with better adhesion is added. However, a thicker ceramic coating is not conducive to the improvement of the energy density of the secondary battery. The use of denser ceramic coatings results in a substantial reduction in the porosity of the separator. However, adding a large amount of binder will cause the risk of blocking pores on the ceramic coating and the base material of the separator, resulting in a large increase in the impedance of ions during the transmission of the separator, which is not conducive to the cycle performance and rate performance of the secondary battery. further improvement.

SUMMARY OF THE INVENTION

In view of the problems existing in the background art, the purpose of the present invention is to provide a separator and a secondary battery, the separator has excellent heat resistance, can improve the kinetic performance of the secondary battery, and at the same time improve the secondary battery. safety performance.

In order to achieve the above objects, in one aspect of the present invention, the present invention provides a separator comprising a porous polymer substrate and a coating. The coating includes ceramic particles and a binder. The ceramic particles include boehmite. The binder includes a compound having reactive isocyanate functional groups.

In another aspect of the present invention, the present invention provides a secondary battery including the separator according to an aspect of the present invention.

Compared with the prior art, the beneficial effects of the present invention are:

The separator of the present invention has excellent heat resistance, and after being applied to a secondary battery, the dynamic performance of the secondary battery can be effectively improved, and the safety performance of the secondary battery can be improved.

Detailed ways

The separator and the secondary battery according to the present invention will be described in detail below.

First, the separator according to the first aspect of the present invention will be described.

A separator according to the first aspect of the present invention comprises: a porous polymer substrate and a coating. The coating includes ceramic particles and a binder. The ceramic particles include boehmite. The binder includes a compound having reactive isocyanate functional groups.

In the separator according to the first aspect of the present invention, the existing binder mainly has physical interaction with the ceramic particles, such as van der Waals force or hydrogen bonding, so the bonding between the binder and the ceramic particles Force and bond strength are limited. Since the surface of boehmite is rich in hydroxyl groups, and the reactive isocyanate functional group has high reactivity, it is easy to react with the hydroxyl groups on the surface of boehmite to form urethane bonds, so the bond between the binder and the ceramic particles is The adhesive force and bond strength are stronger, which makes the heat resistance of the separator better and the properties more stable.

In addition, the reactive isocyanate functional group can react with a small amount of water molecules on the surface of boehmite in addition to reacting with the hydroxyl groups on the surface of boehmite, which not only makes the bonding force and adhesion between the binder and the ceramic particles difficult. The junction strength is increased, and gaseous carbon dioxide is generated during the reaction, which in turn generates a porous isocyanate polymer, which generates more pores inside the coating and provides more lithium ion moving channels, which is beneficial to improve the rate performance of the secondary battery.

In the separator according to the first aspect of the present invention, the compound with reactive isocyanate functional group contains reactive -NCO or the compound with reactive isocyanate functional group is deblocked to generate reactive -NCO . Here, "active -NCO" refers to -NCO that can react with hydroxyl groups on the surface of boehmite, water molecules, or the like.

In the separator according to the first aspect of the present invention, the compound having a reactive isocyanate functional group can be selected from compound I, compound II obtained by reacting compound I with a first compound containing active hydrogen, compound I and compound containing active hydrogen Compound III obtained by reacting the second compound containing active hydrogen, compound IV obtained by reacting compound I with the third compound containing active hydrogen, compound I obtained by reacting the second compound containing active hydrogen and the third compound containing active hydrogen V. Compound VI obtained by reacting compound I with the first compound containing active hydrogen and the third compound containing active hydrogen, compound VII obtained by reacting compound I with the first compound containing active hydrogen and the second compound containing active hydrogen, One or more of the self-polymers formed by compound VIII and compound I obtained by reacting compound I with the first compound containing active hydrogen, the second compound containing active hydrogen and the third compound containing active hydrogen.

In compound I, n≥2; R ₁ is selected from an alkyl group with 3-15 carbon atoms, a cycloalkyl group with a carbon number of 6-30, an aryl group with a carbon number of 6-30 and an aryl group with a carbon number of 6-30 It is one of the arylalkyl groups of 6-30.

The first compound containing active hydrogen is selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, glycerol, trimethylolpropane, trihydroxyethane, pentaerythritol, sorbitol, polyethylene glycol, One or more of ester polyol and polyether polyol. The polyether polyol can be selected from polytetrahydrofuran ether polyol, tetrahydrofuran-propylene oxide copolymer polyol, tetrahydrofuran-ethylene oxide copolymer polyol, tetrahydrofuran-propylene oxide-ethylene oxide copolymer polyol , ethylene glycol-propylene oxide copolymer polyol, propylene glycol-propylene oxide copolymer polyol, ethylene glycol-ethylene oxide copolymer polyol, propylene glycol-ethylene oxide copolymer polyol, trimethylol One or more of propylene oxide-propylene oxide copolymer polyols.

The second compound containing active hydrogen is selected from phenol, α-caprolactam, methanol, ethanol, ethyl mercaptan, thionaphthalene, hydrocyanic acid, N-methylaniline, acetone oxime, butanone oxime, cyclohexanone One or more of oxime, diethyl malonate, methyl ethyl ketoxime, acetylacetone, and sodium bisulfite.

The third compound containing active hydrogen is selected from polyethylene glycol, polyethylene glycol monomethyl ether, ethylene glycol-propylene glycol copolymer, fatty alcohol polyoxyethylene ether, alkyl phenyl polyoxyethylene ether, fatty alcohol Polyoxyethylene ether-sulfonate, alkylphenyl polyoxyethylene ether-sulfonate, fatty alcohol polyoxyethylene ether-sulfate, alkylphenyl polyoxyethylene ether-sulfate, fatty alcohol polyoxyethylene ether - One or more of phosphate, alkyl phenyl polyoxyethylene ether-phosphate.

In compound II, the molar ratio of active -NCO in compound I to active hydrogen in the first compound containing active hydrogen is greater than 1.

In compound III, the molar ratio of active -NCO in compound I to active hydrogen in the second compound containing active hydrogen is greater than or equal to 1.

In compound IV, the molar ratio of active -NCO in compound I to active hydrogen in the third compound containing active hydrogen is greater than 1.

In compound V, the molar ratio of active -NCO in compound I to the sum of active hydrogen in the second compound containing active hydrogen and the sum of active hydrogen in the third compound containing active hydrogen is greater than or equal to 1.

In compound VI, the molar ratio of active -NCO in compound I to the sum of active hydrogen in the first compound containing active hydrogen and the sum of active hydrogen in the third compound containing active hydrogen is greater than 1.

In compound VII, the molar ratio of active -NCO in compound I to the sum of active hydrogen in the first compound containing active hydrogen and active hydrogen in the second compound containing active hydrogen is greater than or equal to 1.

In compound VIII, the difference between the active -NCO in compound I and the active hydrogen in the first compound containing active hydrogen, the active hydrogen in the second compound containing active hydrogen, and the active hydrogen in the third compound containing active hydrogen The total molar ratio is greater than or equal to 1.

In the separator according to the first aspect of the present invention, in the compound III, when the molar ratio of the active -NCO in the compound I to the active hydrogen in the second compound containing active hydrogen is equal to 1, the compound containing The second compound of active hydrogen will form a closed structure with compound I, and the closed structure will be unblocked under certain conditions (such as high temperature, etc.) to form active -NCO again, and the formed active -NCO can also be combined with other compounds. Compounds of active hydrogen (such as hydroxyl groups or water molecules on the surface of boehmite) form relatively stable chemical bonds. In compound V, compound VII, compound VIII, there is a similar situation.

In the separator according to the first aspect of the present invention, in compound IV, compound V, compound VI, and compound VIII, the third compound containing active hydrogen can both react with the active -NCO in compound I and It has good solubility in water, so that the compounds formed by the two (compound IV, compound V, compound VI, and compound VIII) can be emulsified and dispersed in water.

In the isolation film according to the first aspect of the present invention, the aryl group having 6-30 carbon atoms can be selected from one of phenyl and naphthyl; the arylalkyl group having 6-30 carbon atoms can be is selected from benzyl.

In the release film according to the first aspect of the present invention, the compound I is selected from hexamethylene diisocyanate (HDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), tetramethyl xylylene diisocyanate (TMXDI) in one or more.

In the separator according to the first aspect of the present invention, the self-polymer formed by the compound I is selected from the group consisting of dimerized hexamethylene diisocyanate, dimerized diphenylmethane diisocyanate and polydiphenylmethane diisocyanate. one or more of them.

In the separator according to the first aspect of the present invention, the molecular weight of the compound having a reactive isocyanate functional group is 100 g/mol to 10000 g/mol.

In the separator according to the first aspect of the present invention, the mass ratio of the ceramic particles to the binder is (80-99):(1-20), preferably (90-98):(2 ~10).

In the separator according to the first aspect of the present invention, the thickness of the coating layer may be 0.1 μm˜20 μm.

In the separator according to the first aspect of the present invention, the porous polymer substrate is not particularly limited, and can be selected according to requirements. Specifically, the porous polymer substrate may be selected from one or more of polypropylene (PP), polyethylene (PE), and copolymers of propylene and ethylene.

Next, the secondary battery according to the second aspect of the present invention, which includes the separator according to the first aspect of the present invention, will be described.

The secondary battery according to the second aspect of the present invention may be a lithium ion secondary battery, a sodium ion secondary battery or a zinc ion secondary battery.

In the secondary battery according to the second aspect of the present invention, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and an electrolyte.

In the secondary battery according to the second aspect of the present invention, the specific types of the positive electrode sheet, the electrolyte solution and the negative electrode sheet are not particularly limited, and can be selected according to actual needs.

The present application will be further described below with reference to the embodiments. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

In the following examples, the materials, reagents and instruments used can be purchased from commercial sources unless otherwise specified.

Example 1

(1) Preparation of separator

The ceramic particle boehmite (Mohs hardness 3-4) with a mass ratio of 95:5 and the binder compound 1 were added to the solvent deionized water, and mixed uniformly to prepare a slurry with a solid content of 40%.

Compound 1

The slurry is uniformly coated on one side of a 9 μm-thick porous polymer matrix polyethylene by gravure coating to obtain a wet film, and the wet film is dried in an oven to obtain a separator, wherein the slurry is dried The thickness of the coating layer formed later was 3 μm.

Wherein, the preparation process of compound 1 is:

First, under the heating condition of 80°C, 1 mol of trimethylolpropane and 1 mol of polyethylene glycol monomethyl ether HO-(CH ₂ CH ₂ O) ₁₀ -CH ₃ were vacuumed to remove moisture to less than 1000 ppm. Then the trimethylolpropane was lowered to 60°C, 3mol HDI was added, reacted for 2h, a small amount of acetone was added to dilute, then 1mol sodium bisulfite in DMF solution was added, the reaction was continued for 2h, and then 1mol HO-(CH ₂ CH ₂ O) was added ₁₀ - _CH3 was reacted for 2h, and finally acetone was added to dilute to a viscosity of 500mPa.s before shipment to obtain compound 1.

(2) Preparation of positive electrode sheet

The positive active material lithium cobaltate, the conductive agent conductive carbon, and the binder polyvinylidene fluoride (PVDF) were added to the N-methylpyrrolidone solvent system in a weight ratio of 94:3:3, and after fully stirring and mixing, coating Dry and cold-press on Al foil to obtain a positive electrode sheet.

(3) Preparation of negative electrode sheet

The negative active material artificial graphite, conductive agent conductive carbon, binder styrene-butadiene rubber emulsion (SBR), thickener sodium carboxymethyl cellulose (CMC) in a weight ratio of 97:1:1.5:0.5 in deionized water solvent After fully stirring and mixing in the system, it is coated on Cu foil for drying and cold pressing to obtain a negative electrode sheet.

(4) Preparation of electrolyte

The electrolyte includes an organic solvent and a lithium salt, the organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the volume ratio of EC and EMC is 1:1, and the lithium salt is LiPF ₆ , in the electrolyte The concentration is 1mol/L.

(5) Preparation of lithium ion secondary battery

The positive electrode sheet, the separator film and the negative electrode sheet are stacked in sequence, so that the separator film is in the middle of the positive and negative electrode sheets to play a role of isolation, and is wound to obtain a bare cell. The bare cell is placed in an outer package, an electrolyte solution is injected and packaged, and then a lithium ion secondary battery is prepared through a process such as chemical formation (the chemical formation voltage is 3.85V).

Example 2

The preparation process of the lithium ion secondary battery is the same as that of Example 1, except that the binder is Compound 2.

The preparation process of compound 2 is:

First, under the heating condition of 80 °C, 1 mol of the copolymer of trimethylolpropane and propylene oxide (molecular weight is about 2800 g/mol) and 1 mol of polyethylene glycol monomethyl ether HO-(CH ₂ CH ₂ O) _{20 -CH3} vacuum to remove moisture to below 500ppm. Then, 3mol HDI was added to the copolymer of trimethylolpropane and propylene oxide at 80°C, reacted for 2h, diluted with a small amount of acetone, then added 1mol phenol in acetone solution, continued to react for 2h, and then added 1mol HO-(CH ₂ CH ₂ O) ₂₀ -CH ₃ was reacted for 2h, and finally acetone was added to dilute to a viscosity of 500mPa.s before shipment to obtain compound 2.

Example 3

The preparation process of the lithium ion secondary battery is the same as that in Example 1, except that the binder is diphenylmethane diisocyanate.

Example 4

The preparation process of the lithium ion secondary battery is the same as that in Example 1, except that the thickness of the coating formed after the slurry is dried is 2 μm.

Example 5

The preparation process of the lithium ion secondary battery is the same as that of Example 1, except that the thickness of the coating formed after the slurry is dried is 1 μm.

Example 6

The preparation process of the lithium ion secondary battery is the same as that in Example 1, except that the mass ratio of the ceramic particles to the binder is 97:3.

Example 7

The preparation process of the lithium ion secondary battery is the same as that of Example 1, except that the mass ratio of ceramic particles to binder is 90:10

Comparative Example 1

The preparation process of the lithium ion secondary battery is the same as that in Example 1, except that the binder used is polyacrylate, and the mass ratio of boehmite to polyacrylate binder is 97:3.

Comparative Example 2

The preparation process of the lithium ion secondary battery is the same as that of Comparative Example 1, except that the mass ratio of boehmite and polyacrylate binder is 95:5.

Comparative Example 3

The preparation process of the lithium ion secondary battery is the same as that of Comparative Example 2, except that the thickness of the coating formed after the slurry is dried is 2 μm.

Comparative Example 4

The preparation process of the lithium ion secondary battery is the same as that of Comparative Example 2, except that the thickness of the coating formed after the slurry is dried is 1 μm.

Comparative Example 5

The preparation process of the lithium ion secondary battery is the same as that of Comparative Example 1, except that the mass ratio of boehmite and polyacrylate binder is 90:10.

Next, the test procedure of the lithium ion secondary battery will be described.

(1) Test of thermal shrinkage rate of separator

The separator was punched into square pieces with a knife die, and the area of the square piece was recorded as S0, and then the square piece was placed in a constant temperature oven at 130°C for 1 hour and taken out, and the area of the square piece at this time was recorded as S1.

Thermal shrinkage rate (%) of the separator=(S0-S1)/S0×100%.

(2) Adhesion test of separator

Laminate the coated side of the separator with the green glue, then cut it into test strips, fix the lower end of the test strips, and separate the green glue-coated coating and the substrate with a tensile machine. The measured peel force data is the adhesion between the coating of the release film and the substrate.

(3) Rate performance test of lithium ion secondary battery

At room temperature, discharge the lithium-ion secondary battery with a constant current of 0.5C to a voltage of 3.0V, let it stand for 5 minutes, charge it with a constant current of 0.5C to a voltage of 4.4V, and then charge it with a constant voltage of 4.4V to a current of 0.05C. Let stand for 5min, discharge with 0.5C constant current until the voltage is 3V, the discharge capacity at this time is recorded as C0.

At room temperature, discharge the lithium-ion secondary battery with a constant current of 0.5C to a voltage of 3.0V, let it stand for 5 minutes, charge it with a constant current of 1C to a voltage of 4.4V, and then charge it with a constant voltage of 4.4V to a current of 0.05C. Set for 5min, discharge with 0.5C constant current until the voltage is 3V, the discharge capacity at this time is recorded as C1.

At room temperature, discharge the lithium-ion secondary battery with a constant current of 0.5C to a voltage of 3.0V, let it stand for 5 minutes, charge it with a constant current of 0.5C to a voltage of 4.4V, and then charge it with a constant voltage of 4.4V to a current of 0.05C. After standing for 5 minutes, discharge with 2C constant current until the voltage is 3V, and the discharge capacity at this time is recorded as C2.

Lithium-ion secondary battery 1C/0.5V charge rate performance (%)=C1/C0×100%.

Lithium-ion secondary battery 2C/0.5V discharge rate performance (%)=C2/C0×100%.

From the performance test results in Table 1, it can be seen that in Comparative Examples 2-4, as the thickness of the coating decreases from 3 μm to 1 μm, the coating density gradually decreases, and the thermal shrinkage inhibition of the isolation film gradually deteriorates; When the thickness of the coating is reduced, more binder is effectively used on the interface between the coating and the substrate, which in turn leads to an increase in the peeling force, which is beneficial to improve the safety performance of the lithium-ion secondary battery; and the coating thickness The thinning of the lithium ion secondary battery shortens the transmission distance of lithium ions inside the lithium ion secondary battery, which is beneficial to the improvement of the rate performance. In Comparative Examples 1, 2, and 5, with the increase of the polyacrylate binder content, the thermal shrinkage of the coating remained basically unchanged, the peeling force gradually increased, the safety performance of the lithium ion secondary battery increased, and the rate performance appeared The decrease is due to the partial swelling of the polyacrylate binder in the electrolyte to block the pores and block the channel of lithium ion transport.

Compared with Comparative Examples 1-5, the thermal shrinkage rate of the separators of Examples 1-7 of the present invention is reduced, and the adhesion between the coating and the substrate is enhanced. This is because the polyacrylate binders in Comparative Examples 1-5 mainly interact physically with the ceramic particles, so the binding force and the bonding strength between the binder and the ceramic particles are limited. The reactive isocyanate functional groups in the coatings of Examples 1-7 have high reactivity and are easy to react with the hydroxyl groups on the surface of the boehmite to form urethane bonds. The adhesive force and bond strength are stronger, which makes the heat resistance of the separator better and the properties more stable. From the comparison between Example 1 and Examples 4-5, it can be seen that as the thickness of the coating decreases, the compactness of the coating decreases, and the thermal shrinkage inhibition of the isolation film becomes slightly worse; The thinning of the layer thickness, more binder is effectively used at the interface between the coating and the substrate, so the adhesion between the coating and the substrate increases; and the thinning of the coating thickness makes the lithium The transmission distance of lithium ions inside the ion secondary battery is shortened, which is beneficial to the improvement of rate performance.

In addition, compared with Comparative Examples 1-5, the charge rate performance and discharge rate performance of the lithium ion secondary batteries of Examples 1-7 were improved. From the comparison of Example 1 and Examples 6-7, it can be seen that the rate performance of the lithium ion secondary battery is not affected even when the binder content in the coating is relatively high. This is because the reactive isocyanate functional group can not only react with the hydroxyl groups on the surface of the boehmite, but also react with a small amount of water molecules on the surface of the boehmite, which not only makes the bonding force between the binder and the ceramic particles and the ceramic particles better. The bonding strength increases, and gaseous carbon dioxide is generated during the reaction, which in turn generates a porous isocyanate polymer, which generates more pores inside the coating and provides more lithium ion movement channels, which is beneficial to improve the performance of lithium ion secondary batteries. rate performance. And because the bonding force and bonding strength between the binder and the ceramic particles are stronger, there will not be a phenomenon similar to the partial swelling and blocking of the pores of the polyacrylate binder in the electrolyte, so the lithium ion secondary The rate performance of the battery will not be degraded.

Claims (11)

1. A separator comprising: porous polymer substrates; and coating; It is characterized in that, The coating includes: ceramic particles; and binder; the ceramic particles include boehmite; The binder includes a compound having reactive isocyanate functional groups. 2 . The separator according to claim 1 , wherein the compound with reactive isocyanate functional group contains reactive -NCO or the compound with reactive isocyanate functional group is deblocked and generated after deblocking. 3 . Active -NCO. 3. The separator according to claim 2, wherein the compound with reactive isocyanate functional group is selected from the group consisting of compound I, compound I and the first compound containing active hydrogen obtained by reacting compound II, compound Compound III obtained by reacting I with the second compound containing active hydrogen, compound IV obtained by reacting compound I with the third compound containing active hydrogen, and compound I reacting with the second compound containing active hydrogen and the third compound containing active hydrogen The obtained compound V and compound I react with the first compound containing active hydrogen and the third compound containing active hydrogen The compound VI, compound I obtained by reacting the first compound containing active hydrogen and the second compound containing active hydrogen One or more of the self-polymers formed by the reaction of compound VII and compound I with the first compound containing active hydrogen and the second compound containing active hydrogen and the reaction of the third compound containing active hydrogen with compound VIII and compound I ;

in: n≥2; R ₁ is selected from an alkyl group with 3-15 carbon atoms, a cycloalkyl group with 6-30 carbon atoms, an aryl group with 6-30 carbon atoms and an arylalkyl group with 6-30 carbon atoms one of the The first compound containing active hydrogen is selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, glycerol, trimethylolpropane, trihydroxyethane, pentaerythritol, sorbitol, polyethylene glycol, One or more of ester polyol and polyether polyol; The second compound containing active hydrogen is selected from phenol, α-caprolactam, methanol, ethanol, ethyl mercaptan, thionaphthalene, hydrocyanic acid, N-methylaniline, acetone oxime, butanone oxime, cyclohexanone One or more of oxime, diethyl malonate, methyl ethyl ketoxime, acetylacetone, sodium bisulfite; The third compound containing active hydrogen is selected from polyethylene glycol, polyethylene glycol monomethyl ether, ethylene glycol-propylene glycol copolymer, fatty alcohol polyoxyethylene ether, alkyl phenyl polyoxyethylene ether, fatty alcohol Polyoxyethylene ether-sulfonate, alkylphenyl polyoxyethylene ether-sulfonate, fatty alcohol polyoxyethylene ether-sulfate, alkylphenyl polyoxyethylene ether-sulfate, fatty alcohol polyoxyethylene ether One or more of phosphate, alkyl phenyl polyoxyethylene ether-phosphate; In compound II, the molar ratio of active -NCO in compound I to active hydrogen in the first compound containing active hydrogen is greater than 1; In compound III, the molar ratio of active -NCO in compound I to active hydrogen in the second compound containing active hydrogen is greater than or equal to 1; In compound IV, the molar ratio of active -NCO in compound I to active hydrogen in the third compound containing active hydrogen is greater than 1; In compound V, the molar ratio of active -NCO in compound I to the sum of active hydrogen in the second compound containing active hydrogen and the sum of active hydrogen in the third compound containing active hydrogen is greater than or equal to 1; In compound VI, the molar ratio of the active -NCO in compound I to the sum of active hydrogen in the first compound containing active hydrogen and the sum of active hydrogen in the third compound containing active hydrogen is greater than 1; In compound VII, the molar ratio of active -NCO in compound I to the sum of active hydrogen in the first compound containing active hydrogen and the sum of active hydrogen in the second compound containing active hydrogen is greater than or equal to 1; In compound VIII, the difference between the active -NCO in compound I and the active hydrogen in the first compound containing active hydrogen, the active hydrogen in the second compound containing active hydrogen, and the active hydrogen in the third compound containing active hydrogen The total molar ratio is greater than or equal to 1. 4. The separator according to claim 3, wherein the polyether polyol is selected from the group consisting of polytetrahydrofuran ether polyol, tetrahydrofuran-propylene oxide copolymer polyol, and tetrahydrofuran-ethylene oxide copolymer polyol , tetrahydrofuran-propylene oxide-ethylene oxide copolymer polyol, ethylene glycol-propylene oxide copolymer polyol, propylene glycol-propylene oxide copolymer polyol, ethylene glycol-ethylene oxide copolymer polyol , one or more of propylene glycol-ethylene oxide copolymer polyol and trimethylolpropane-propylene oxide copolymer polyol. 5. The separator according to claim 3, wherein the compound I is selected from the group consisting of hexamethylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, One or more of isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate and tetramethyl xylylene diisocyanate. 6. The isolation film according to claim 3, wherein the self-polymer formed by compound I is selected from the group consisting of dimerized hexamethylene diisocyanate, dimerized diphenylmethane diisocyanate, and polydiphenylmethane diisocyanate. One or more of isocyanates. 7 . The separator according to claim 1 , wherein the compound having a reactive isocyanate functional group has a molecular weight of 100 g/mol to 10000 g/mol. 8 . 8 . The separator according to claim 1 , wherein the mass ratio of the ceramic particles to the binder is (80˜99):(1˜20). 9 . 9 . The separator according to claim 8 , wherein the mass ratio of the ceramic particles to the binder is (90˜98):(2˜10). 10 . 10 . The separator according to claim 1 , wherein the thickness of the coating is 0.1 μm˜20 μm. 11 . 11. A secondary battery, comprising the separator according to any one of claims 1-10.