High voltage tantalum anode and method of manufacture

Patent metadata

Field	Value
Publication number	US-9633796-B2
Application number	US-201615095196-A
Country	US
Kind code	B2
Filing date	Apr 11, 2016
Priority date	Sep 6, 2013
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

Tantalum powders produced using a tantalum fiber precursor are described. The tantalum fiber precursor is chopped or cut into short lengths having a uniform fiber thickness and favorable aspect ratio. The chopped fibers are formed into a primary powder having a controlled size and shape, narrow/tight particle size distribution, and low impurity level. The primary powder is then agglomerated into an agglomerated powder displaying suitable flowability and pressability such that pellets with good structural integrity and uniform pellet porosity are manufacturable. The pellet is sintered and anodized to a desired formation voltage. The thusly created capacitor anode has a dual morphology or dual porosity provided by a primary porosity of the individual tantalum fibers making up the primary powder and a larger secondary porosity formed between the primary powders agglomerated into the agglomerated powder.

First claim

What is claimed is:

1. A capacitor assembly, comprising:
a) a casing comprising first and second inner wall surfaces;
b) at least a first tantalum anode housed inside the casing, wherein:
i) the first tantalum anode is characterized as having been fabricated from tantalum fibers having a diameter ranging from 0.5 μm to 2.5 μm and a length ranging from 5 μm to 50 μm, the tantalum fibers forming a tantalum powder as a loosely packed mass of the tantalum fibers, and
ii) the tantalum powder is characterized as having been agglomerated into a randomly oriented, substantially non-aligned, porous agglomerated tantalum powder having a primary porosity, which agglomerated tantalum powder is characterized as having been pressed into a tantalum pellet having a secondary porosity, and
iii) the tantalum pellet is characterized as having been sintered so that the pellet has:
A) an inter-granule pore size attributed to the primary porosity of:
d10 of 0.5 μm to 2 μm; and
d90 of 3 μm to 10 μm; and

B) an intra-granule pore size attributed to the secondary porosity of:
d10 of 20 μm to 40 μm; and
d90 of 60 μm to 100 μm; and

iv) the sintered pellet is characterized as having then been anodized to a formation voltage greater than zero up to 550 V to form a dielectric oxide on the tantalum fibers and thereby provide the tantalum anode;

c) an insulative seal comprising a feedthrough wire electrically connected to the first anode, wherein the feedthrough wire extends outside the casing and is electrically isolated from the casing;
d) a cathode comprising cathode active material supported by and in electrical contact with the first inner wall surface and with the second inner wall surface of the casing;
e) a separator preventing direct physical contact between the first anode and the cathode active material supported on the first and second inner wall surfaces of the casing while allowing for ion flow therethrough; and
f) an electrolyte contacting the cathode and the first anode.

2. The capacitor of claim 1 including a second tantalum anode housed inside the casing, wherein the second tantalum anode is electrically connected in parallel with the first tantalum anode, and wherein a cathode current collector comprising opposed major current collector faces supporting the cathode active material is disposed intermediate the first and second anodes.

3. The capacitor of claim 1 wherein there are “n” tantalum anodes electrically connected in parallel with each other and housed inside the casing, and wherein there are n−1 cathode current collectors supporting the cathode active material on opposed major current collector faces thereof and disposed intermediate side-by-side adjacent ones of the n tantalum anodes.

4. The capacitor of claim 1 wherein the casing comprises a first casing member having a first face wall joined to a surrounding side wall and a second casing member having a second face wall secured to the surrounding side wall of the first casing member.

5. The capacitor of claim 1 wherein the feedthrough wire is connected to the first tantalum anode and a wire extends from the first tantalum anode to the second tantalum anode to electrically connect the first and second tantalum anodes in parallel.

6. The capacitor of claim 1 wherein the tantalum fibers comprising the tantalum powder have a length-to-diameter (L/D) aspect ratio ranging from 2 to 100.

7. The capacitor of claim 1 wherein the tantalum fibers comprising the tantalum powder have a L/D aspect ratio ranging from 10 to 40.

8. The capacitor of claim 1 wherein the agglomerated tantalum powder has substantially no fines less than 200 mesh.

9. The capacitor of claim 1 wherein, prior to being sintered and anodized to form the first tantalum anode, the tantalum pellet has a pressed density of 3 g/cc to 8 g/cc.

10. The capacitor of claim 1 wherein, prior to being sintered and anodized to form the first tantalum anode, the tantalum pellet has a pressed density of 4 g/cc to 6.5 g/cc.

11. The capacitor of claim 1 wherein the tantalum pellet is characterized as having been sintered at a temperature ranging from 1,200° C. to 2,200° C., for a time ranging from 0.1 to 120 minutes, and at a vacuum of <1×10 −4 Torr (Argon).

12. The capacitor of claim 1 wherein the tantalum pellet is characterized as having been sintered at a temperature ranging from 1,500° C. to 1,850° C., for a time ranging from 1 to 10 minutes, and at a vacuum of <1×10 −5 Torr (Argon).

13. The capacitor of claim 1 wherein, prior to being anodized to form the first tantalum anode, the sintered tantalum pellet has a sintered density ranging from 4 g/cc to 9 g/cc.

14. The capacitor of claim 1 wherein, prior to being anodized to form the first tantalum anode, the sintered tantalum pellet has a sintered density ranging from 5 g/cc to 8 g/cc.

15. The capacitor of claim 1 wherein, prior to being anodized to form the first tantalum anode, the sintered tantalum pellet has a d50 inter-granule pore size attributed to the primary porosity of 1 μm to 5 μm, and a d50 intra-granule pore size attributed to the secondary porosity of 30 μm to 80 μm.

16. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder has an agglomerate density ranging from 1.5 g/cc to 4.5 g/cc.

17. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder is has an agglomerate density ranging from 2.5 g/cc to 3.5 g/cc.

18. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder has an agglomerate diameter of:
i) d10 of 74 μm;
ii) d50 ranging from 200 μm to 500 μm; and
iii) d90 of 1,000 μm.

19. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder has a d50 inter-granular pore size attributed to the primary porosity of 1 μm to 5 μm.

20. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder has a d50 inter-granular pore size attributed to the primary porosity of 2 μm to 3 μm.

21. The capacitor of claim 1 wherein, prior to being pressed into the tantalum pellet, the agglomerated tantalum powder has an inter-granular pore size attributed to the primary porosity of d10 of 0.5 μm and d90 of 20 μm.

22. The capacitor of claim 1 wherein the sintered tantalum pellet is characterized as having been anodized in an electrolyte comprising H 3 PO 4 and having a conductivity up to about 20,000 μS at 40° C.

23. A capacitor assembly, comprising:
a) a casing comprising first and second inner wall surfaces;
b) at least a first tantalum anode and a second tantalum anode electrically connected in parallel and housed inside the casing, wherein:
i) the parallel connected first and second tantalum anodes are characterized as each having been fabricated from tantalum fibers having a diameter ranging from 0.5 μm to 2.5 μm and a length ranging from 5 μm to 50 μm, the tantalum fibers forming a tantalum powder as a loosely packed mass of the tantalum fibers, and
ii) the tantalum powder is characterized as having been agglomerated into a randomly oriented, substantially non-aligned, porous agglomerated tantalum powder having a primary porosity, which agglomerated tantalum powder is characterized as having been pressed into a first tantalum pellet and into a second tantalum pellet, both pellets havi

Assignees

• Greatbatch Ltd

Inventors

• Liu Yanming
• Muffoletto Barry C
• Hahl Jason T

Classifications

• B22F1/148

  Agglomerating · CPC title

• B22F9/04

  starting from solid material, e.g. by crushing, grinding or milling ({C22C1/1084 takes precedence}; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C) · CPC title

• B22F3/02

  Compacting only · CPC title

• B22F3/002

  Manufacture of articles essentially made from metallic fibres · CPC title

• H01G9/145

  Liquid electrolytic capacitors (H01G11/00 takes precedence) · CPC title