Binder for secondary battery providing excellent cycle property

Patent metadata

Field	Value
Publication number	US-9543584-B2
Application number	US-201113704013-A
Country	US
Kind code	B2
Filing date	Jun 8, 2011
Priority date	Jun 16, 2010
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

Provided is a binder for secondary battery electrodes wherein the content of a gel comprising a polymer particle obtained by copolymerizing three or more types of monomers is 50 to 100% by weight and a swelling index of the binder to an electrolyte is 1.1 to 5.0. The binder fundamentally improves electrode stability due to the gel content defined above and increases ionic conductivity due to the swelling index, thus providing secondary batteries with superior cycle properties.

First claim

The invention claimed is:

1. A binder for secondary battery electrodes, comprising: a gel comprising a polymer particle obtained by copolymerizing three or more types of monomers, the binder having a gel content ranging from 97 to 99% by weight and a swelling index in the presence of an electrolyte ranging from 1. 3 to 1.9, wherein the electrolyte comprises ethylene carbonate, propylene carbonate and diethyl carbonate, wherein a mass ratio of diethyl carbonate to ethylene carbonate and propylene carbonate is 1:1 and
wherein the three or more types of monomers are an ethylenically unsaturated carbonic acid ester monomer, at least one monomer selected from the group consisting of a vinyl monomer and a nitrile monomer, and an ethylenically unsaturated carbonic acid monomer,
wherein the ethylenically unsaturated carbonic acid ester monomer and the at least one monomer selected from the group consisting of a vinyl monomer and a nitrile monomer are present in an amount of 80 to 99% by weight, based on the total weight of the binder, and the ethylenically unsaturated carbonic acid monomer is present in an amount of greater than 5% to 20% by weight, based on the total weight of the binder,
wherein the cross-linking agent is present in an amount of 0.1 to less than 1% by weight, based on the total weight of the copolymer, and
wherein the cross-linking agent is at least one monomer selected from the group consisting of difunctional monomers, trifunctional monomers, tetrafunctional monomers, pentafunctional monomers, and hexafunctional monomers.

2. The binder according to claim 1 , wherein the ethylenically unsaturated carbonic acid ester monomer and the at least one monomer selected from a vinyl monomer and a nitrile monomer are added in a molar ratio of 1:10 to 10:1.

3. The binder according to claim 1 , wherein the ethylenic ally unsaturated carbonic acid ester monomer is at least one monomer selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethyl hexyl acrylate, hydroxy propyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethyl hexyl methacrylate, hydroxy propyl methacrylate, lauryl methacrylate, methyl crotonate, ethyl crotonate, propyl crotonate, butyl crotonate, isobutyl crotonate, n-amyl crotonate, isoamyl crotonate, n-hexyl crotonate, 2-ethyl hexyl crotonate, hydroxy propyl crotonate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate.

4. The binder according to claim 1 , wherein the vinyl monomer is at least one monomer selected from the group consisting of styrene, o-, m- and p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, o-, m- and p-ethylstyrene, p-t-butylstyrene, divinyl benzene and vinyl naphthalene.

5. The binder according to claim 1 , wherein the nitrile monomer is at least one monomer selected from the group consisting of succinonitrile, sebaconitrile, fluoronitrile, chloronitrile, acrylonitrile and methacrylonitrile.

6. The binder according to claim 1 , wherein the ethylenic ally unsaturated carbonic acid monomer is at least one selected from the group consisting of unsaturated monocarbonic acid monomers, unsaturated dicarbonic acid monomers, and acid anhydrides thereof.

7. The binder according to claim 6 , wherein the unsaturated monocarbonic acid monomers are selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid and isocrotonic acid, and wherein the unsaturated dicarbonic acid monomers are selected from the group consisting of maleic acid, fumaric acid, citraconic acid, mesaconic acid, glutaconic acid, and itaconic acid.

8. An electrode for secondary batteries in which an electrode active material is bonded to a conductive material by the binder for secondary batteries according to claim 1 .

9. The electrode according to claim 8 , wherein the electrode active material is a lithium transition metal oxide powder or carbon powder.

10. A lithium secondary battery comprising the electrode for secondary batteries according to claim 8 .

11. The binder according to claim 1 , wherein the difunctional monomers are selected from the group consisting of 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, dimethylol dicyclopentane diacrylate, ethylene oxide-modified hexahydrophthalic acid diacrylate, tricyclodecane dimethanol acrylate, neopentyl glycol-modified trimethylolpropane diacrylate, and adamantane diacrylate,
wherein the trifunctional monomers are selected from the group consisting of trimethylol propanetri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylol propanetri(meth)acrylate, and tris(acryloxyethyl)isocyanurate,
wherein the tetrafunctional monomers are selected from the group consisting of diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate,
wherein the pentafunctional monomers are selected from the group consisting of propionic acid-modified dipentaerythritol and penta(meth)acrylate, and
wherein the hexafunctional monomers are selected from the group consisting of caprolactone-modified dipentaerythritol and hexa(meth)acrylate.

Assignees

• Kim Ok Sun
• Kim Young-Min
• Kang Minah
• Lg Chemical Ltd

Inventors

• Kim Ok Sun
• Kim Young-Min
• Kang Minah

Classifications

• C08F220/1808

  C8-(meth)acrylate, e.g. isooctyl (meth)acrylate or 2-ethylhexyl (meth)acrylate · CPC title

• C08F220/44

  Acrylonitrile · CPC title

• C08F220/40

  Esters of unsaturated alcohols {, e.g. allyl (meth)acrylate} · CPC title

• H01M4/134

  Electrodes based on metals, Si or alloys · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title