Positive electrode for lithium-ion secondary battery and production process for the same, and lithium-ion secondary battery

Patent metadata

Field	Value
Publication number	US-9685660-B2
Application number	US-201414777584-A
Country	US
Kind code	B2
Filing date	Sep 10, 2014
Priority date	Sep 10, 2014
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

A positive electrode for lithium-ion secondary battery is provided, the positive electrode being able to endure high-temperature and high-voltage driving modes or operations. At least parts of the surface of positive-electrode active-material particles are covered by a polymer coating layer, and an amino group and phosphoric-acid group are included in the polymer coating layer. Since the polymer coating layer includes a phosphoric-acid-based polymer, capacity declines are inhibited at the time of cycle tests.

First claim

The invention claimed is:

1. A positive electrode for lithium-ion secondary battery comprising:
a positive-electrode active-material particles;
a polymer coating layer formed on at least parts of surface of said positive-electrode active-material particles; and
said polymer coating layer including an amino group, and a phosphoric-acid group.

2. The positive electrode for lithium-ion secondary battery as set forth in claim 1 , wherein said polymer coating layer is a composite of an amino-based polymer with an amino group and a phosphoric-acid-based polymer with a phosphoric-acid group on a side chain thereof.

3. The positive electrode for lithium-ion secondary battery as set forth in claim 1 , wherein said active-material particles include an Li compound or solid solution selected from the group consisting of Li x Ni a Co b Mn c O 2 , Li—Co b Mn c O 2 , Li x Ni a Mn c O 2 , Li x Ni a Co b O 2 and Li 2 MnO 3 (note that 0.5≦“x”≦1.5, 0.1≦“a”<1, 0.1≦“b”<1 and 0.1≦“c”<1).

4. The positive electrode for lithium-ion secondary battery as set forth in claim 1 , wherein a thickness of said polymer coating layer is 10 nm or less.

5. The positive electrode for lithium-ion secondary battery as set forth in claim 1 , wherein said positive-electrode active-material particles comprise Li x Ni a Co b Mn c O 2 .

6. The positive electrode for lithium-ion secondary battery as set forth in claim 1 , wherein said amino-based polymer with an amino group is polyethyleneimine.

7. A secondary-battery positive-electrode production process for the positive electrode as set forth in claim 1 , the production process comprising the steps of:
forming a positive-electrode active-material layer by applying a slurry onto a surface of a current collector and then drying the slurry thereon, the slurry comprising a binding agent, and positive-electrode active-material particles; and
forming a cationic polymer coating layer and then forming a phosphoric-acid-based polymer coating layer by applying onto the positive-electrode active-material layer a cationic polymer solution comprising a solvent and a cationic polymer which is dissolved in the solvent and of which the zeta potential is positive under a neutral condition, and then drying the cationic polymer solution, and subsequently applying onto the cationic polymer coating layer a phosphoric-acid-based polymer solution comprising a solvent and a phosphoric-acid-based polymer, which has a phosphoric-acid group on a side chain thereof and is dissolved in the solvent and of which the zeta potential is negative under a neutral condition, and then drying the phosphoric-acid-based polymer solution.

8. The secondary-battery positive-electrode production process as set forth in claim 7 , wherein the step of applying said cationic polymer solution is carried out by a dipping method.

9. The secondary-battery positive-electrode production process as set forth in claim 7 , wherein the step of applying said phosphoric-acid-based polymer solution is carried out by a dipping method.

10. The secondary-battery positive-electrode production process as set forth in claim 7 , wherein said positive-electrode active-material particles include an Li compound or solid solution selected from the group consisting of Li x Ni a Co b Mn c O 2 , Li x Co b Mn c O 2 , Li x Ni a Mn c O 2 , Li x Ni a Co b O 2 and Li 2 MnO 3 (note that 0.5≦“x”≦1.5, 0.1≦“a”<1, 0.1≦“b”<1 and 0.1≦“c”<1).

11. A lithium-ion secondary battery comprising said positive electrode for lithium-ion secondary battery as set forth in claim 1 .

12. The lithium-ion secondary battery as set forth in claim 11 exhibiting a battery voltage of 4.3 V or more when being charged.

Assignees

• Toyota Jidoshokki Kk

Inventors

• Oshima Hiroki
• Suzuki Kanae
• Maki Takeshi

Classifications

• H01M4/661

  Metal or alloys, e.g. alloy coatings (H01M4/669 take precedence) · CPC title

• H01M4/0404

  by coating on electrode collectors · CPC title

• H01M4/1391

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M10/4235

  Safety or regulating additives or arrangements in electrodes, separators or electrolyte (H01M10/4242 takes precedence) · CPC title