Positive Electrode Slurry Composition for Secondary Battery, and Positive Electrode for Secondary Battery and Secondary Battery Which are Prepared by Using the Same

Patent metadata

Field	Value
Publication number	US-2020203778-A1
Application number	US-202016809075-A
Country	US
Kind code	A1
Filing date	Mar 4, 2020
Priority date	Nov 24, 2017
Publication date	Jun 25, 2020
Grant date	—

Abstract

A positive electrode slurry composition for a secondary battery which includes a positive electrode active material, a carbon-based conductive agent having a specific surface area (Brunauer-Emmett-Teller (BET)) of 100 m 2 /g to 200 m 2 /g, a binder, and a nitrile-based copolymer which has an electrolyte solution swelling degree defined by Equation (1) of 200% or less and does not contain a functional group other than a cyano group is provided:
electrolyte solution swelling degree (%)={( W 1 −W 0 )/ W 0 }×100  Equation (1)
wherein, W 0 is an initial weight of a polymer film prepared from the nitrile-based copolymer, and W 1 is a weight of the polymer film which is measured after storing the polymer film at 60° for 48 hours in an electrolyte solution.

First claim

1 . A positive electrode slurry composition for a secondary battery, comprising:
a positive electrode active material, a carbon-based conductive agent having a specific surface area measured by a Brunauer-Emmett-Teller (BET) of 100 m 2 /g to 200 m 2 /g, a binder, and a nitrile-based copolymer which has an electrolyte solution swelling degree defined by Equation (1) of 200% or less and does not contain a functional group other than a cyano group:
electrolyte solution swelling degree (%)={( W 1 −W 0 )/ W 0 }×100  Equation (1)

wherein, in Equation (1), W 0 is an initial weight of a polymer film prepared from the nitrile-based copolymer, and W 1 is a weight of the polymer film which is measured after storing the polymer film at 60° for 48 hours in an electrolyte solution.

2 . The positive electrode slurry composition of claim 1 , wherein the nitrile-based copolymer is a nitrile-based binary copolymer having an α,β-unsaturated nitrile-derived unit and a hydrogenated conjugated diene-derived unit.

3 . The positive electrode slurry composition of claim 2 , wherein the nitrile-based binary copolymer comprises 60 wt % to 80 wt % of the hydrogenated conjugated diene-derived unit and 20 wt % to 40 wt % of the α,β-unsaturated nitrile-derived unit.

4 . The positive electrode slurry composition of claim 2 , wherein the nitrile-based binary copolymer comprises 65 wt % to 75 wt % of the hydrogenated conjugated diene-derived unit and 25 wt % to 35 wt % of the α,β-unsaturated nitrile-derived unit.

5 . The positive electrode slurry composition of claim 2 , wherein the nitrile-based binary copolymer has a hydrogenation rate of the conjugated diene-derived unit of 90% or more.

6 . The positive electrode slurry composition of claim 1 , wherein the nitrile-based copolymer is composed of a repeating unit represented by [Formula 1] and a repeating unit represented by [Formula 2],

7 . The positive electrode slurry composition of claim 1 , wherein the nitrile-based copolymer has a weight-average molecular weight of 200,000 g/mol to 350,000 g/mol.

8 . The positive electrode slurry composition of claim 1 , wherein the carbon-based conductive agent is carbon nanotubes having a specific surface area (BET) of 150 m 2 /g to 200 m 2 /g.

9 . The positive electrode slurry composition of claim 1 , wherein the carbon-based conductive agent is carbon black having a specific surface area (BET) of 100 m 2 /g to 150 m 2 /g.

10 . The positive electrode slurry composition of claim 1 , comprising:
96 parts by weight to 98.5 parts by weight of the positive electrode active material, 0.1 part by weight to 2 parts by weight of the conductive agent, 1.2 parts by weight to 2 parts by weight of the binder, and 0.02 part by weight to 2 parts by weight of the nitrile-based copolymer based on 100 parts by weight of a total solid content in the positive electrode slurry composition.

11 . The positive electrode slurry composition of claim 1 , wherein the positive electrode slurry composition has a solid content concentration of 70 wt % to 75 wt %.

12 . A positive electrode comprising a positive electrode active material layer formed by using the positive electrode slurry composition of claim 1 .

13 . A secondary battery comprising the positive electrode of claim 12 , a negative electrode, a separator, and an electrolyte.

14 . The secondary battery of claim 13 , wherein a resistance increase rate measured after storage of the secondary battery at 60° C. for 4 weeks is 20% or less.

15 . The positive electrode slurry composition of claim 1 , wherein the nitrile-based copolymer has the electrolyte solution swelling degree of 141% to 200%.

16 . A method of preparing a positive electrode slurry comprising:
mixing a positive electrode active material, a carbon-based conductive agent, a nitrile-based copolymer, and a binder in a solvent, wherein the carbon-based conductive agent has a specific surface area measured by a Brunauer-Emmett-Teller (BET)method of 100 m 2 /g to 200 m 2 /g, and the nitrile-based copolymer has an electrolyte solution swelling degree defined by Equation (1) of 200% or less and does not contain a functional group other than a cyano group:
electrolyte solution swelling degree (%)={( W 1 −W 0 )/ W 0 }×100  Equation (1)

wherein, in Equation (1), W 0 is an initial weight of a polymer film prepared from the nitrile-based copolymer, and W 1 is a weight of the polymer film which is measured after storing the polymer film at 60° for 48 hours in an electrolyte solution

17 . The method of claim 16 , wherein the mixing comprises dispersing the carbon-based conductive agent and the nitrile-based copolymer in the solvent to prepare a conductive agent dispersion, and then the conductive agent dispersion is mixed with the positive electrode active material and the binder.

18 . The method of claim 16 , wherein the mixing includes a cavitation dispersion treatment.

19 . The method of claim 18 , wherein the cavitation dispersion treatment is performed by ultrasonic wavers, a jet mill or a shear dispersion treatment.

Assignees

• Lg Chemical Ltd

Inventors

• Yoo Jung Woo
• Shim Hye Lim
• Lim Jun Muk

Classifications

• H01M4/625

  Carbon or graphite · CPC title

• H01M4/62

  Selection of inactive substances as ingredients for active masses, e.g. binders, fillers · CPC title

• H01M4/13 Primary

  Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/622 Primary

  being polymers · CPC title