Separator, preparation method thereof, and secondary battery, battery module, battery pack, and apparatus related thereto

1 . A separator, comprising:

a substrate; and

a coating layer provided on at least one surface of the substrate;

wherein the coating layer comprises:

an inorganic particle layer disposed on the substrate and comprising inorganic particles; and

organic particles,

wherein the organic particles comprise first organic particles, and the first organic particles are secondary particles formed by agglomerating primary particles with a particle size of 150 nm-300 nm, the first organic particles are partially embedded into the inorganic particle layer and form bulges on a surface of the inorganic particle layer,

the first organic particles comprise one selected from the group consisting of polytetrafluoroethylene, polychlorctrifluoreethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, a copolymer containing different fluoroalkenyl monomer units, a copolymer containing fluoroalkenyl monomer units and alkenyl monomer units, a copolymer containing fluoroalkenyl monomer units and acrylic acid monomer units, a copolymer containing fluoroalkenyl monomer units and acrylate monomer units, and any combinations thereof;

a mass percentage of the first organic particles in the coating layer is 15% to 25%;

a mass percentage of the inorganic particles in the coating layer is 65%-75%; and

a number-based median particle size of the first organic particles is from 12 μm to 25 μm,

wherein the organic particles further comprise second organic particles, the second organic particles are embedded into the inorganic particle layer and form bulges on a surface of the inorganic particle layer, and the second organic particles are primary particles, a number-based median particle size of the second organic particles is 2 μm to 10 μm, and a mass percentage of the second organic particles in the coating layer is 2% to 10%;

wherein the second organic particles comprise a copolymer of an acrylate monomer unit and a styrene monomer unit, the acrylate monomeric unit comprising at least one of an isooctyl acrylate unit or an isooctyl methacrylate unit,

a mass percentage of the second organic particles in the coating is less than a mass percentage of the first organic particles in the coating.

2 . The separator according to claim 1 , wherein the number-based median particle size of the first organic particles is 15 μm-20 μm.

3 . The separator according to claim 1 , wherein the first organic particle comprises one or more of polytetrafluoroethylene, polychlorctrifluoreethylene, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide.

4 . The separator according to claim 1 , wherein the first organic particle comprises one or more of vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer.

5 . The separator according to claim 1 , wherein the mass percentage of the first organic particles in the coating layer is 20%-25%.

6 . A separator comprising:

a substrate; and

a coating layer provided on at least one surface of the substrate;

wherein the coating layer comprises:

an inorganic particle layer disposed on the substrate and comprising inorganic particles, wherein a mass percentage of the inorganic particles in the coating layer is ≤85%; and

organic particles,

wherein the organic particles comprise first organic particles, the first organic particles are secondary particles partially embedded into the inorganic particle layer and form bulges on a surface of the inorganic particle layer, a mass percentage of the first organic particles in the coating layer is 15% to 25%, a number-based median particle size of the first organic particles is from 12 μm to 25 μm;

wherein the organic particles further comprise second organic particles, the second organic particles are embedded into the inorganic particle layer and form bulges on a surface of the inorganic particle layer, and the second organic particles are primary particles, a number-based median particle size of the second organic particles is 2 μm to 10 μm, and a mass percentage of the second organic particles in the coating layer is 2% to 10%;

wherein the first organic particles comprise one selected from the group consisting of polytetrafluoroethylene, polychlorctrifluoreethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, a copolymer containing different fluoroalkenyl monomer units, a copolymer containing fluoroalkenyl monomer units and alkenyl monomer units, a copolymer containing fluoroalkenyl monomer units and acrylic acid monomer units, a copolymer containing fluoroalkenyl monomer units and acrylate monomer units, and any combinations thereof,

wherein the second organic particles comprise a copolymer of an acrylate monomer unit and a styrene monomer unit, the acrylate monomeric unit comprising at least one of an isooctyl acrylate unit or an isooctyl methacrylate unit,

a mass percentage of the second organic particles in the coating is less than a mass percentage of the first organic particles in the coating.

7 . The separator according to claim 6 , wherein a number-based median particle size of the second organic particles is 2.5 to 6 μm.

8 . The separator according to claim 6 , wherein the mass percentage of the second organic particles in the coating layer is 2%-8%.

9 . The separator according to claim 1 , wherein a volume-based median particle size Dv50 of the inorganic particles is 0.5 μm-2.5 μm.

10 . The separator according to claim 1 , wherein the inorganic particle comprises one or more of boehmite (γ-AlOOH), aluminum oxide (Al 2 O 3 ), barium sulfate (BaSO 4 ), magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2 ), silicon dioxide (SiO 2 ), tin dioxide (SnO 2 ), titanium oxide (TiO 2 ), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), nickel oxide (NiO), cerium oxide (CeO 2 ), zirconium titanate (SrTiO 3 ), barium titanate (BaTiO 3 ), and magnesium fluoride (MgF 2 ).

11 . The separator according to claim 1 , wherein the separator satisfies:

(1) an air permeability of the separator is 100 s/100 mL-300 s/100 mL;

(2) a tensile strength in transverse direction (MD) of the separator is 1500 kgf/cm 2 -3000 kgf/cm 2 ;

(3) a tensile strength in machine direction (TD) of the separator is 1000 kgf/cm 2 -2500 kgf/cm 2 ;

(4) a transverse elongation at break of the separator is 50%-200%; and

(5) a longitudinal elongation at break of the separator is 50%-200%.

12 . The separator according to claim 1 , wherein the inorganic particles and the organic particles form uneven pore structures in the coating layer.

13 . The separator according to claim 1 , wherein a distance between any two adjacent inorganic particles is denoted as L1, a distance between any adjacent inorganic particle and organic particle is denoted as L2, and L1<L2.

14 . A method for preparing the separator according to claim 1 , comprising the following steps:

(1) providing a substrate;

(2) providing a coating layer slurry, wherein the coating layer slurry comprises constituent materials and a solvent, the constituent materials comprise inorganic particles and organic particles, and the organic particles comprise first organic particles; and

(3) applying the coating layer slurry in step (2) on at least one side of the substrate in step (1) to form a coating layer, and performing drying to obtain the separator;

wherein the separator comprises: the substrate; and the coating layer provided on at least one surface of the substrate, wherein the coating layer comprises the inorganic particles and the organic particles, the organic particles comprise the first organic particles, the first organic particles are embedded into the inorganic particles and form bulges on a surface of the coating layer, and a number-based median particle size of the first organic particles is ≥12 μm.

15 . The method according to claim 14 , wherein in step (2), the organic particles further comprise second organic particles, and the second organic particles are primary particles.

16 . The method according to claim 15 , wherein mass of the added second organic particles is less than or equal to mass of the added first organic particles; and

a percentage of the mass of the added second organic particles in a total dry weight of the constituent materials is below 10%.

17 . The method according to claim 14 , wherein the method satisfies one or more of the following conditions (1) to (7):

(1) in step (2), a percentage of the mass of the added first organic particles in the total dry weight of the constituent materials is above 12%;

(2) in step (2), a solid content of the coating layer slurry is 28%-45%;

(3) in step (3), a coater is used for the coating, the coater comprises a gravure roller, and the number of lines of the gravure roller is 100 LPI-300 LPI;

(4) in step (3), a speed of the coating is 30 m/min-90 m/min;

(5) in step (3), a linear speed ratio of the coating is 0.8-2.5;

(6) in step (3), a drying temperature is 40° C.-70° C.; and

(7) in step (3), drying time is 10s-120s.

18 . A secondary battery, comprising the separator according to claim 1 .

19 . A battery module, comprising the secondary battery according to claim 18 .

20 . A battery pack, comprising the battery module according to claim 19 .

21 . The separator according to claim 6 , wherein the second organic particles comprise one or more selected from the group consisting of, butyl methacrylate-isooctyl methacrylate copolymer, isooctyl methacrylate-styrene copolymer, methyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl acrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl acrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, isooctyl methacrylate-styrene-acrylonitrile copolymer, and any combinations thereof.

22 . The separator according to claim 6 , wherein the first organic particle comprises one or more of polychlorctrifluoreethylene, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer.