# US 10,872,731 B2 · Aluminum oxide layer on anode foil for aluminum electrolytic capacitor

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- Number: US 10,872,731 B2
- Document ID: US10872731B2
- Status: Granted
- Kind: B2
- Application number: 16/888,647
- Filed: 2020-05-29
- Published: 2020-09-17
- Granted: 2020-12-22
- Earliest claimed: 2018-06-01
- Assignees: Pacesetter, Inc.
- Applicants: Pacesetter, Inc.
- Inventors: Ralph Jason Hemphill; James Brian Smith
- Web page: https://patentgrep.com/patent/US10872731B2

## CPC

- C25D 11/18: After-treatment, e.g. pore-sealing
- H01G 9/0032: {formation of the dielectric layer}
- C25D 11/08: containing inorganic acids
- C25D 11/12: Anodising more than once, e.g. in different baths
- H01G 9/045: based on aluminium
- H01G 9/048: characterised by their structure (H01G11/22 takes precedence)
- H01G 9/07: Dielectric layers
- H01G 9/02: Diaphragms; Separators
- H01G 9/055: Etched foil electrodes
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)

## Abstract

A method of producing an oxide layer on a foil for use in a capacitor includes immersing the foil in a first solution; maintaining a target current between the immersed anodic foil and the first solution until a first target voltage is reached to form an oxide layer overlying the foil; maintaining the target current between the immersed foil and the first solution until a second target voltage is reached to reform the oxide layer; removing the foil from the first solution and heating the foil; immersing the heat treated foil in a second solution; maintaining the target current between the immersed foil and the second solution until a third target voltage is reached; and discharging the immersed foil after each of the first, second, and third target voltages are reached.

## Claims

### Claim 1

A device, comprising:
a conductive anode;
a layer of a barrier oxide disposed on a surface of the conductive anode, wherein the barrier oxide is an aluminum oxide having a boehmite phase and a pseudo-boehmite phase, the amount of the boehmite phase being greater than the amount of the pseudo-boehmite phase;
a conductive cathode; and
a separator disposed between the anode and the cathode.

### Claim 2 (depends on 1)

The device of claim 1, wherein the device is a capacitor.

### Claim 3 (depends on 2)

The device of claim 2, wherein the device is an electrolytic capacitor.

### Claim 4 (depends on 1)

The device of claim 1, wherein the boehmite phase is greater than or equal 50 wt % of the aluminum oxide.

### Claim 5 (depends on 4)

The device of claim 4, wherein the boehmite phase is from 50 wt % to 51 wt % of the aluminum oxide.

### Claim 6 (depends on 5)

The device of claim 5, wherein the pseudo-boehmite phase is from 49 wt % to 50 wt % of the aluminum oxide.

### Claim 7 (depends on 1)

The device of claim 1, wherein the boehmite phase is less porous than the pseudo-boehmite phase.

### Claim 8 (depends on 1)

The device of claim 1, wherein the pseudo-boehmite phase has a higher water content than the boehmite phase.

### Claim 9 (depends on 1)

The device of claim 1, wherein the aluminum oxide includes cores in shells where the boehmite phase is present at a surface of the shells and the pseudo-boehmite phase is present in the cores.

### Claim 10 (depends on 1)

The device of claim 1, wherein boehmite phase is less porous than the pseudo-boehmite phase;
the pseudo-boehmite phase has a higher water content than the boehmite phase; and
the aluminum oxide includes cores in shells where the boehmite phase is present at a surface of the shells and the pseudo-boehmite phase is present in the cores.

### Claim 11 (depends on 1)

The device of claim 1, wherein tunnels extend into the anode at a density of 30 to 40 million tunnels/cm2 of apparent area.

### Claim 12 (depends on 1)

The device of claim 1, wherein the anode has a leakage current between 0.1 mA/cm2 of apparent surface area and about 2.0 mA/cm2 of apparent surface area.

### Claim 13 (depends on 1)

The device of claim 1, wherein the anode includes a phosphate.

### Claim 14 (depends on 1)

The device of claim 1, wherein the aluminum oxide is not positioned over an edge of the anode.

### Claim 15 (depends on 1)

The device of claim 1, wherein a passivation layer is positioned on the anode.

### Claim 16 (depends on 15)

The device of claim 15, wherein the aluminum oxide is not positioned over an edge of the anode and the passivation layer is positioned over the edge of the anode.

### Claim 17 (depends on 16)

The device of claim 16, wherein an electrolyte between the anode and the cathode has a water content less than 3.0 wt % of the electrolyte.

### Claim 18 (depends on 17)

The device of claim 17, wherein the electrolyte has a water content between 0.5 wt % and 3.0 wt %.

### Claim 19

An electrolytic capacitor, comprising:
a conductive anode;
a layer of a barrier oxide disposed on a surface of the conductive anode, wherein the barrier oxide is an aluminum oxide having a boehmite phase and a pseudo-boehmite phase, the amount of the boehmite phase being greater than the amount of the pseudo-boehmite phase,
the boehmite phase being less porous than the pseudo-boehmite phase,
the pseudo-boehmite phase having a higher water content than the boehmite phase, and
the aluminum oxide includes cores in shells where the boehmite phase is present at a surface of the shells and the pseudo-boehmite phase is present in the cores;
a conductive cathode;
a separator disposed between the anode and the cathode; and
an electrolyte between the anode and the cathode with a water content less than 3.0 wt % of the electrolyte.