EP-3806191-B1 - SEPARATOR FOR RECHARGEABLE BATTERY AND LITHIUM RECHARGEABLE BATTERY COMPRISING SAME

Inventors

• KIM, JINWOO
• CHUN, JIHYUN
• HONG, DAEHYUN
• BAE, IMHYUCK
• LEE, SANGHO

Dates

Publication Date

20260513

Application Date

20190426

Claims (10)

1. A separator for rechargeable battery, comprising a porous substrate and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a binder including a fluorine-based binder and a (meth)acryl-based binder and a filler, the fluorine-based binder includes a first structural unit derived from vinylidene fluoride and a second structural unit derived from at least one monomer of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, ethylene tetrafluoride, and ethylene monomers, and 10 wt% or less of the second structural unit is included based on the fluorine-based binder, the fluorine-based binder includes a first fluorine-based binder having a weight average molecular weight of 800,000 to 1,500,000 and a second fluorine-based binder having a weight average molecular weight of less than or equal to 600,000, and the (meth)acryl-based binder has pencil hardness of 5H or higher wherein the weight average molecular weight is polystyrene-reduced average molecular weight measured by gel permeation chromatography.
2. The separator of claim 1, wherein the fluorine-based binder further includes a third structural unit derived from a monomer having at least one hydroxy group.
3. The separator of claim 2, wherein the monomer having at least one hydroxy group is at least one selected from (meth)acrylic acid, a derivative of (meth)acrylate having a hydroxy group, itaconic acid, or a derivative thereof, maleic acid or a derivative thereof and hydroxyalkane allyl ether.
4. The separator of claim 2, wherein the third structural unit is included in an amount of 0.5 wt% to 7 wt% based on the first fluorine-based binder.
5. The separator of claim 1, wherein the first fluorine-based binder is included in an amount of 10 wt% to 50 wt% and the second fluorine-based binder is included in an amount of 50 wt% to 90 wt% based on a total amount of the first fluorine-based binder and the second fluorine-based binder.
6. The separator of claim 1, wherein the (meth)acryl-based binder includes a structural unit derived from a monomer having a (meth)acrylate group or a (meth)acrylic acid group.
7. The separator of claim 1, wherein the fluorine-based binder is included in an amount of greater than or equal to 55 wt%, based on a total amount of the fluorine-based binder and the (meth)acryl-based binder.
8. The separator of claim 1, wherein the filler is included in an amount of 75 wt% to 99 wt% based on the coating layer.
9. The separator of claim 1, wherein the filler comprises Al 2 O 3 , SiO 2 , TiO 2 , SnO 2 , CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , boehmite, or a combination thereof.
10. A rechargeable lithium battery, comprising a positive electrode, a negative electrode, and the separator for rechargeable battery of any one of claim 1 to claim 9 between the positive electrode and the negative electrode.

Description

[Technical Field] A separator for rechargeable battery and a rechargeable lithium battery including the same are disclosed. [Background Art] A separator for an electrochemical battery is an intermediate film that separates a positive electrode and a negative electrode in a battery, and maintains ion conductivity continuously to enable charge and discharge of a battery. A separator for a rechargeable battery is required to have physical properties such as adhesive force, heat resistance, and durability. A number of techniques have been reported to improve wet adhesive force, which is adhesive force in a state in which an electrolyte is added to a battery. In recent years, in the case of large-sized batteries of the stack type, dry adhesive force, which is an adhesive force in the state in which the electrolyte is not added to the battery, is required. Therefore, it is necessary to develop a separator that not only has improved wet adhesive force and heat resistance, but also improved dry adhesive force. US 2017/338460 and US 2014/030578 refer both to separators including an adhesive layer including a fluorine based binder, PMMA and a filler. [Disclosure] [Technical Problem] A separator for rechargeable battery having improved heat resistance, wet adhesive force and dry adhesive force is provided. In addition, a rechargeable lithium battery having improved heat resistance, durability, cycle-life characteristics, and safety is provided. [Technical Solution] In an embodiment, a separator for a rechargeable battery includes a porous substrate and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a binder including a fluorine-based binder and a (meth)acryl-based binder and a filler, the fluorine-based binder includes a first structural unit derived from vinylidene fluoride and a second structural unit derived from at least one monomer of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, ethylene tetrafluoride, and ethylene monomers and 10 wt% or less of the second structural unit is included based on the fluorine-based binder,the fluorine-based binder includes a first fluorine-based binder having a weight average molecular weight of 800,000 to 1,500,000 and a second fluorine-based binder having a weight average molecular weight of less than or equal to 600,000, andthe (meth)acryl-based binder has pencil hardness of 5H or higher. In another embodiment, a rechargeable lithium battery includes a positive electrode, a negative electrode, and the separator for the rechargeable battery between the positive electrode and the negative electrode. [Advantageous Effects] The separator for the rechargeable battery has improved heat resistance, wet adhesive force and dry adhesive force, and a rechargeable lithium battery including the same has improved properties such as heat resistance, durability, cycle-life characteristics, and stability. [Description of the Drawings] FIG. 1 is a view showing a separator for a rechargeable battery according to an embodiment.FIG. 2 is an exploded perspective view showing a rechargeable lithium battery according to an embodiment. [Mode for Invention] Hereinafter, embodiments of the present invention are described in detail. However, these embodiments are exemplary, the present invention is not limited thereto and the present invention is defined by the scope of claims. Hereinafter, a separator for a rechargeable battery according to an embodiment is described. FIG. 1 is a view showing a separator for a rechargeable battery according to an embodiment. Referring to FIG. 1, a separator 10 for a rechargeable battery according to an embodiment includes a porous substrate 20 and a coating layer 30 disposed on one surface or both surfaces of the porous substrate 20. The porous substrate 20 may have a plurality of pore and may generally be a porous substrate used in an electrochemical device. Non-limiting examples of the porous substrate 20 may be a polymer film formed of a polymer selected from polyolefin such as polyethylene, polypropylene, and the like, a polyester such as polyethylene terephthalate, polybutylene terephthalate, and the like, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene oxide, a cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, a glass fiber, Teflon, and polytetrafluoroethylene, or a mixture of two or more. The porous substrate 20 may be for example a polyolefin-based substrate, and the polyolefin-based substrate may improve has safety of a battery due to its improved shut-down function. The polyolefin-based substrate may be for example selected from a polyethylene single film, a polypropylene single film, a polyethylene/polypropylene double film, a polypropylene/polyethylene/polypropylene triple film, and a polyethylene/polypropylene/polyethylene triple film. In a