Separator, preparation method therefor and related secondary battery, battery module, battery pack and device
The present application relates to a separator in the electrochemical field and a preparation method therefor, and to a secondary battery comprising the separator, a device comprising the secondary battery. The separator of the present application is prepared by a simple process and has excellent heat resistance performance. Moreover, the secondary batteries and devices comprising the separator of the present application have good safety performance and cycling performance.
1 . A separator, comprising:
a substrate; and
a coating provided on at least one surface of the substrate;
wherein
the coating comprises inorganic particles and organic particles, the inorganic particles form an inorganic particle layer, the organic particles comprise first organic particles and second organic particles, the first organic particles and the second organic particles are embedded in the inorganic particle layer and forming protrusions on a surface of the inorganic particle layer;
the first organic particles have a number-average particle size of 13 μm to 25 μm, and an area coverage of the first organic particles on a surface of the coating of ≤10%;
the second organic particles have a number-average particle size of 2 μm-8 μm; and 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; a ratio of the area coverage of the first organic particles on the coating surface to an area coverage of the second organic particles on the coating surface is more than 1:1 and less than or equal to 20:1.
2 . The separator according to claim 1 , wherein the area coverage of the first organic particles on the coating surface is 0.5%-8%.
3 . The separator according to claim 1 , wherein the first organic particles have a number-average particle size of 15 μm-25 μm.
4 . The separator according to claim 1 , wherein the first organic particles comprise one or more of a homopolymer or copolymer of a fluorine-containing olefine monomeric unit, a homopolymer or copolymer of an olefine monomeric unit, a homopolymer or copolymer of an unsaturated nitrile monomeric unit, a homopolymer or copolymer of an alkylene oxide monomeric unit, and modified compounds of these homopolymers or copolymers.
5 . The separator according to claim 1 , wherein a mass percentage of the inorganic particles in the coating is ≤80%.
6 . The separator according to claim 1 , wherein
the first organic particles and the inorganic particles are formed from a same coating slurry;
a portion of the first organic particles is concentrated on a top portion of the coating without touching a surface of the substrate; and
a portion of the inorganic particles is concentrated on a bottom portion of the coating close to the substrate.
7 . The separator according to claim 1 , wherein the second organic particles have a number-average particle size of 2.5 μm-6 μm.
8 . The separator according to claim 1 , wherein
the mass percentage of the first organic particles in the coating is ≥12%;
the mass percentage of the second organic particles in the coating is ≤8%.
9 . The separator according to claim 1 , wherein a sum of the area coverages of the first organic particles and the second organic particles on the coating surface is ≤15%.
10 . The separator according to claim 1 , wherein the ratio of the area coverage of the first organic particles on the coating surface to the area coverage of the second organic particles on the coating surface is 2:1-10:1.
11 . The separator according to claim 1 , wherein the inorganic particles comprise 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 ).
12 . The separator according to claim 1 , wherein the separator satisfies one or more of the following (1)-(5):
(1) the separator has an air permeability of 100 s/100 mL-300 s/100 mL;
(2) the separator has a transverse tensile strength (MD) of 1500 kgf/cm 2 -3000 kgf/cm 2 ;
(3) the separator has a longitudinal tensile strength (TD) of 1000 kgf/cm 2 -2500 kgf/cm 2 ;
(4) the separator has a transverse elongation at break of 50%-200%; and
(5) the separator has a longitudinal elongation at break of 50%-200%.
13 . The separator according to claim 1 , wherein the inorganic particles and the organic particles form a non-uniform pore structure in the coating.
14 . The separator according to claim 1 , wherein a spacing between any two adjacent inorganic particles is denoted as L 1 , and a spacing between any inorganic particle and an adjacent organic particle is denoted as L 2 , with L 1 <L 2 .
15 . A method for preparing a separator the method comprising:
(1) providing a substrate;
(2) providing a coating slurry, the coating slurry comprising a component material and a solvent, wherein the component material comprises inorganic particles and organic particles, and the organic particles comprise first organic particles and second organic particles; and
(3) coating at least one side of the substrate from step (1) with the coating slurry from step (2), so as to form a coating, and drying the same to obtain the separator;
wherein the separator comprises the substrate and the coating the first organic particles and the second organic particles, the inorganic particles form an inorganic particle layer, the first organic particles and the second organic particles are embedded in the inorganic particle layer and form protrusions on a surface of the inorganic particle layer;
the first organic particles are secondary particles and have a number-average particle size from 13 μm to 25 μm, and an area coverage on a surface of the coating of ≤10%,
a ratio of the area coverage of the first organic particles on the coating surface to the area coverage of the second organic particles on the coating surface is more than 1:1 and less than or equal to 20:1,
the second organic particles have a number-average particle size of 2 μm-8 μm,
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.
16 . The preparation method according to claim 15 , wherein the second organic particles are in a mass percentage of 8% or less of a total dry weight of the component material.
17 . The preparation method according to claim 15 , wherein the method satisfies one or more of the following (1)-(7):
(1) in step (2), the first organic particles are in a mass percentage of 12% or more of a total dry weight of the component material;
(2) in step (2), the coating slurry has a solid content of 28%-45% based on a weight of the coating slurry;
(3) in step (3), the coating is carried out by using a coating machine, wherein the coating machine comprises a gravure roller which has a number of lines of 100 LPI-300 LPI;
(4) in step (3), the coating is carried out at a speed of 30 m/min-90 m/min;
(5) in step (3), the coating is carried out at a line speed ratio of 0.8-2.5;
(6) in step (3), the drying is carried out at a temperature of 40° C. to 70° C.; and
(7) in step (3), the drying is carried out for a period of 10 s-120 s.
18 . A secondary battery, comprising a separator according to claim 1 .
19 . The separator according to claim 1 , wherein the first organic particles are secondary particles having a secondary particle morphology, or the second organic particles are primary particles having a primary particle morphology.
20 . The separator according to claim 1 , wherein
the mass percentage of the first organic particles in the coating is 15% to 25%; and
the mass percentage of the second organic particles in the coating is 2% to 8%.
21 . The separator according to claim 1 , wherein the second organic particles comprise at least one of a copolymer of an acrylate monomeric unit and a styrene monomeric unit, and a copolymer of an acrylate monomeric unit, an acrylic acid monomeric unit, and a styrene monomeric unit, the acrylate monomeric unit comprising at least one of an isooctyl acrylate unit or an isooctyl methacrylate unit, the acrylic acid monomeric unit comprising at least one of an acrylic acid or a methacrylic acid unit.
22 . The separator according to claim 21 , wherein the copolymer of the second organic particles comprises one or more selected from a butyl methacrylate-isooctyl methacrylate copolymer, an isooctyl methacrylate-styrene copolymer, a methacrylate-methacrylic acid-styrene copolymer, a methyl acrylate-isooctyl methacrylate-styrene copolymer, a butyl acrylate-isooctyl acrylate-styrene copolymer, a butyl acrylate-isooctyl methacrylate-styrene copolymer, a butyl methacrylate-isooctyl methacrylate-styrene copolymer, and a butyl methacrylate-isooctyl acrylate-styrene copolymer.
23 . The separator according to claim 22 , wherein the copolymer of the second organic particles comprises a methacrylate-methacrylic acid-styrene copolymer.