Method of producing a lithium ion secondary battery and a lithium ion secondary battery produced thereby

• US 6,231,626 B1
• Filed: 02/03/1998
• Issued: 05/15/2001
• Est. Priority Date: 02/04/1997
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yoshida, Yasuhiro, Shiota, Hisashi, Murai, Michio, Inuzuka, Takayuki, Aihara, Shigeru, Hamano, Kouji, Shiraga, Syo
• Primary Examiner(s): Maples, John S.
• Application Number:
  US09/018,016
• Time in Patent Office: 1,197 Days
• Field of Search: 429/217, 296/235
• US Class Current: 29/623.5
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 4/02 Electrodes composed of, or comprising, active material
• CPC Class Codes: H01M 4/0471 involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/139 Processes of manufacture
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/60 of organic compounds
• CPC Class Codes: H01M 4/622 being polymers
• CPC Class Codes: H01M 6/188 Processes of manufacture
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

A paste-like active material mixture prepared by mixing an active material powder and a particulate material comprising a polymer soluble in a nonaqueous electrolytic solution is applied to, e.g., collectors 1c and 2c to a uniform thickness, and then dried to form positive and negative electrodes 1, 2 containing an active material powder and a particulate polymer. The two electrodes are assembled into an electrode laminate into which the foregoing electrolytic solution is then injected.

Claims

1. A method of producing a lithium ion secondary battery, which comprises the steps of:

preparing a positive electrode active material mixture by mixing a positive electrode active material powder with a particulate polymer soluble in a nonaqueous electrolytic solution;

preparing a negative electrode active material mixture by mixing a negative electrode active material powder with a particulate polymer soluble in a nonaqueous electrolytic solution;

forming a positive electrode comprising said positive electrode active material powder and said particulate polymer soluble in a nonaqueous electrolytic solution by coating the positive electrode active material mixture onto a metal substrate;

forming a negative electrode comprising said negative electrode active material powder and particulate polymer soluble in a nonaqueous electrolytic solution by coating the negative electrode active material mixture onto a metal substrate;

assembling said positive electrode and said negative electrode into an electrode laminate;

and then injecting said electrolytic solution into said electrode laminate.

2. The method of producing a lithium ion secondary battery according to claim 1, wherein said particulate polymer soluble in a nonaqueous electrolytic solution comprises at least one of methacrylic polymer, acrylic polymer, polyethylene glycol, polypropylene glycol, and a copolymer obtained by the copolymerization of these polymers with other monomers.

3. The method of producing a lithium ion secondary battery according to claim 1, further comprising the step of introducing the particulate polymer soluble in a nonaqueous electrolytic solution externally into voids in said positive electrode and said negative electrode before the step of assembling said positive electrode and said negative electrode into the electrode laminate.

4. The method of producing a lithium ion secondary battery according to claim 1, further comprising the steps of:

coating said positive electrode and said negative electrode with or dipping said positive electrode and said negative electrode in a solution of said polymer soluble in a nonaqueous electrolytic solution;

and then drying said coated positive electrode and said negative electrode before the step of assembling said positive electrode and said negative electrode into the electrode laminate.

5. The method of producing a lithium ion secondary battery according to claim 4, wherein said active material mixture further comprises a binder resin and the method further comprises the step of heating said positive electrode and said negative electrode at a temperature at which said particulate polymer soluble in a nonaqueous electrolytic solution melts and said binder resin does not melt.

6. The method of producing a lithium ion secondary battery according to claim 5, wherein said particulate polymer comprises at least one polymer selected from the group consisting of polyethylene glycol and polypropylene glycol and said electrodes are heated at 80°

C.

7. The method of producing a lithium ion secondary battery according to claim 1, wherein a diameter of said particulate polymer is not larger than 20 μ

m.

8. The method of producing a lithium ion secondary battery according to claim 7, wherein a diameter of said particulate polymer is not larger than 5 μ

m.