Thin-film lithium battery and process

• US 5,895,731 A
• Filed: 05/15/1997
• Issued: 04/20/1999
• Est. Priority Date: 05/15/1997
• Status: Expired due to Fees

• Current Assignee: Nelson E. Smith
• Original Assignee: Nelson E. Smith
• Inventors: Clingempeel, Richard K.
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US08/856,658
• Time in Patent Office: 705 Days
• Field of Search: 429/82, 429/162, 429/176, 429/190, 429/198, 429/234, 429/245, 29/623.2, 29/623.4
• US Class Current: 429/162
• CPC Class Codes: H01M 10/05 Accumulators with non-aqueous electrolyte H01M10/39 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 29/4911 including sealing
• CPC Class Codes: Y10T 29/49114 including adhesively bonding

Abstract

A lithium battery and process of making same involves employing alternate layers of a lithium anode and an aluminum foil or NiAl expanded metal supported cathode assembly with a gel electrolyte contacting the alternate layers. The electrolyte includes a quantity of N-methyl-2-pyrrollidone and lithium contained within a polyimide matrix and the entire assembly is contained within a sealed polyimide casing. Separate electrical contacts are provided for each of the lithium anode assembly and the aluminum foil or NiAl supported cathode assembly. An out-gassing vent tube extends from the sealed polyimide casing and is sealed a predetermined time after battery construction.

Claims

1. A thin film lithium battery comprising:

a lithium anode assembly;

a cathode assembly;

a metal film supporting said cathode assembly;

said lithium anode and said metal film supporting said cathode assembly being disposed in alternate layers;

a composite electrolyte in gel form contacting the alternate layers of said lithium anode assembly and said metal film supporting said cathode assembly;

said electrolyte including a quantity of lithium and N-methyl-2-pyrrollidone contained within a polyimide matrix; and

a sealed polyimide casing containing the alternate layers of said lithium anode assembly and said metal film supporting said cathode assembly.

2. The lithium battery of claim 1 including separate electrical contacts for each of said lithium anode assembly and said metal supported cathode assembly;

said electrical contacts extending to the exterior of said sealed polyimide casing.

3. The lithium battery of claim 1 including an out-gassing vent tube extending from said sealed polyimide casing, said out-gassing vent tube being open when said lithium battery is first constructed and sealed within 24 hours after battery assembly.

4. The lithium battery of claim 1 wherein said metal film supporting said cathode assembly is selected from the group of metal films consisting of (a) an NiAl expanded metal, (b) aluminum foil, and a copper clad plastics.

5. A method of making a lithium battery comprising the steps of:

(a) providing a gel electrolyte by dissolution of lithium in an N-methyl-2-pyrrollidone/polyimide matrix;

(b) providing a non-conductive matting including a first sheet of fiberglass material having a mixture consisting of fiberglass resin and resin hardener and a polyimide powder press dried thereon;

(c) providing a lithium anode assembly including at least one layer of a lithium film and an anode conductor layer;

(d) providing a second sheet of fiberglass material disposed on a metal film selected from the group of metal films consisting of (i) an aluminum foil sheet, (ii) a NiAl expanded metal foil, and (iii) a copper clad plastics film;

(e) press drying a cathode material mixture onto the metal film from step (d) to form a cathode material matting;

(f) cutting two identical strips from the cathode material matting obtained in step (e) and placing each strip between a pair of aluminum plates;

(g) press bonding each of the strips of cathode material matting to the aluminum plates disposed thereon in a lab press at 16,000 PSI for twenty minutes;

(h) spreading a lithium/NMP/polyimide gel onto the cathode material matting;

(i) sandwiching and bonding the anode assembly obtained in step (c) between the aluminum plates containing the cathode material obtained in step (f);

(j) covering the article obtained in step (i) with a layer of the non-conductive matting provided in step (b);

(k) wrapping or spooling the non-conductive matting and bonded anode and cathode materials into a radial configuration;

(l) inserting the radial configuration into an open casing formed of a fiberglass/hardener mixture; and

(m) sealing the open fiberglass resin/hardener casing with an exterior coating of a polyimide to produce a finished lithium battery.

6. The method of claim 5 wherein the mixture of fiberglass resin and resin hardener and polyimide powder includes a mixture ratio of one ounce of fiberglass epoxy resin and 16 drops of methylethylketone peroxide hardener with two grams of a polyimide powder.

7. The method of claim 6 wherein the first sheet of fiberglass material consists of a fiberglass matting of approximately five mils thickness and wherein the mixture of resin and resin hardener and polyimide powder is evenly distributed thereon.

8. The method of claim 7 wherein the fiberglass matting having the evenly distributed mixture thereon is placed between two sheets of clear acetate film, each having a thickness of approximately five mils, and pressed in a lab press at room temperature and at approximately 12,000 PSIG for a period of approximately three hours.

9. The method of claim 8 including the steps of:

sanding flat the recovered pressed non-conducting matting article using 400 grit sandpaper;

applying an additional quantity of the fiberglass resin, resin hardener and polyimide powder evenly distributed over the flat sanded matting article;

again placing the coated matting article between two sheets of clear acetate film and pressing again at approximately 12,000 PSIG in a lab press for an additional three and one/half hours; and

removing the pressed article from the lab press to recover a finished non-conductive matting for use in preparation of the lithium battery.

10. The method of claim 5 wherein the lithium film in the lithium anode assembly has a thickness of approximately 3 mils and including the step of providing a fiberglass matting supporting the lithium film.

11. The method of claim 10 including:

providing an anode conductor layer selected from the group of conductor layers consisting of (i) a layer of copper coated plastics (ii) a layer of nickel/aluminum expanded metal having a thickness of approximately 2 mils;

wrapping the fiberglass supported lithium film around the conductor layer to form an anode assembly;

placing the anode assembly between two layers of clear acetate film and pressing the anode assembly at 10,000 PSIG in a lab press for five-ten minutes;

removing the pressed anode assembly from the press and trimming the anode assembly pressed article to the desired configuration; and

wrapping the pressed anode assembly in a moisture proof wrapping until ready for use in making the lithium battery.

12. The method of claim 5 wherein the cathode material mixture includes:

(a) a mixture ratio of 14 grams of powdered graphite, 0.5 grams polyimide powder;

1 gram titanium nitride;

0.5 grams silicon; and

1 gram carbon precursor powder; and

(b) a mixture ratio of one ounce fiberglass resin and 16 drops methylethylketone peroxide hardener;

thoroughly agitating the mixture obtained in step (a) with that of step (b) for a period of at least 5 minutes to recover the cathode material mixture.

13. The method of claim 12 wherein said carbon precursor powder has a mean particle size of 2-5 microns and contains 2-20%, by volume, C₆₀⁴ and >

80%, by volume C₂⁴ carbon soot.

14. The method of claim 12 including:

pouring the cathode material mixture onto a sheet of fiberglass matting;

placing the fiberglass matting onto a metal film selected from the group of metal films consisting of (i) aluminum foil and (ii) nickel/aluminum expanded metal;

positioning the resulting article between two sheets of clear acetate film;

pressing the acetate film contents in a lab press at approximately 12,000 PSIG for three and one half hours;

removing the pressed article from the lab press;

removing the acetate films from the pressed article;

wiping excess moisture from the pressed article with paper towels; and

permitting the wiped article it to further dry at room temperature for at least 30 minutes prior to use.

15. The method of claim 14 including:

heating each of the two identical strips of cathode material to approximately 200°

F. for sixty to ninety minutes to remove any remaining mechanical moisture;

permitting the heated strips to cool to room temperature;

immersing the room temperature cooled strips of cathode material matting in a container of N-methyl-2-pyrrollidone and sealing the container and contents for a period of at least 24 hours.

16. The method of claim 15 including:

removing the two strips of cathode material matting from the container of N-methyl-2-pyrrollidone and inserting the strips into separate aluminum foil plates previously provided with cut-out portions to accept the cathode material strips;

placing each of the aluminum foil plates containing the cathode material matting between two sheets of clear acetate film and pressing the resultant at 16,000 PSIG in a lab press for twenty minutes prior to employing the pressed aluminum plates and cathode matting to sandwich and bond the anode assembly therebetween.