WO1983003105A1

WO1983003105A1 - Method for manufacturing a large surface current collector for an electrochemical cell in the form of a porous titanium plate or sheet

Info

Publication number: WO1983003105A1
Application number: PCT/CH1983/000021
Authority: WO
Inventors: Boveri & Cie Bbc Aktiengesellschaft Brown
Original assignee: Devantay, Hubert; Stucki, Samuel
Priority date: 1982-03-05
Filing date: 1983-02-28
Publication date: 1983-09-15
Also published as: IT1160493B; IT8319907A0; CH653581A5; EP0102966A1; IT8319907A1

Abstract

The large surface current collector for an electro-chemical cell, in the form of a titanium plate or sheet having a given porosity, is fabricated by arranging on a non-adhesive support (1), for example a plane plate of non porous special graphite having an orientated structure of individual graphite platelets, a uniform layer (3) of dry titanium powder or of viscous homogeneous paste (2) formed by titanium powder suspended in a liquid, by subjecting the dried layer (3) to a presintering, cold rolling and resintering, all these operations being carried out in vacuum conditions, and finally covering the dried layer with an electric catalyst. The cold rolling as well as the resintering may be repeated several times until the desired sheet density is obtained.

Description

Process for producing a large-area current collector for an electrochemical cell in the form of a porous plate or foil made of titanium

The invention is based on a method for producing a large-area current collector according to the preamble of claim 1.

When building electrolysis devices, in particular for water electrolysis using solid electrolytes, the task is to provide corrosion-resistant, porous current collectors. Foils and plates made of porous titanium are preferably used for such purposes on the chemically aggressive oxygen side. Components of this type are produced almost exclusively by powder metallurgical methods. Other process steps such as hot pressing, hot pressing, gravity sintering, powder rolling, etc. are used (US Pat. No. 2,997,777: Poroshkovaya Metallurgya 7, pages 13 to 16, July 1976; Poroshkovaya Metallurgya 6, pages 96 to 99, June 1977).

According to the above mentioned methods, they are mainly porous

Titanium foils of limited dimensions for experimental purposes

2 has been produced. If you want to go to large areas (up to 1 m), such as those used for industrial electrolysis systems are necessary, you encounter difficulties. The problem mainly consists in the fact that it appears almost hopeless to achieve a uniform distribution of the titanium powder for surfaces of any size, which is then reflected in different thicknesses, non-uniform porosity and other inhomogeneities. In addition, according to the known methods, it is hardly possible to obtain a desired, targeted porosity of the film that builds up the current collector.

The invention is based on the object of specifying an economical method for producing a current collector in the form of a porous plate or foil made of titanium, the area of which is not limited and the thickness and porosity of which are uniform over the entire area, the density or Porosity can be selectively reproduced within narrow limits with narrow tolerances.

This object is achieved according to the invention by the features of claim 1.

The invention is described with reference to the following exemplary embodiment explained by three figures.

It shows:

1 shows the temperature curve over time for the heat treatment;

2 shows the mode of operation of the powder distribution device; Fig. 3 is a Flie ^'ssdiagramm the method.

1 shows the temperature profile as a function of time for the heat treatment of the titanium powder. posed. The diagram is self-explanatory. In deviation from the diagram, heating to 500 ° C. can also be carried out in the period from 30 to 90 minutes. The sintering temperature can be 900 to 1200 c.

2 schematically shows the use of a device for applying the dry titanium powder or the titanium paste. 1 is the support in the form of a flat plate (non-porous, non-sticky graphite). 2 represents the viscous, homogeneous paste consisting of titanium powder and terpineol (C .H „0). 3 is the coherent, uniform layer of this paste. A movable coating device 4 to be displaced in the direction of the arrow in the form of a container tapering downward can be used as a means for applying the paste.

In a variant of the method, 2 and 3 represent the dry, free-flowing titanium powder or the upper layer thus produced on the carrier 1.

Ausführungsbeisgiel_l See Figures 1 and 2.

For producing a current collector for an electrolytic cell Wasser¬ in the form of a porous titanium film of 0.5 mm thickness initially a viscous, homogeneous paste 2 of titanium powder particle size was 15 to 120 yes and anhydrous terpineol C_ _n _o 0 H_ mixed. The titanium powder

1U lo was made from titanium sponge with a large inner surface. The powder particles had very irregular shapes with branches and protuberances. The mixing ratio was adjusted in such a way that 9 titanium powders per 6 ml terpineol. The viscous, homogeneous paste 2 was placed in a mobile coating device *. for thin Layer chromatography plates are filled in the form of a tapering container and applied as a coherent, uniform layer 3 to a support 1 in the form of a flat plate. The arrow in FIG. 2 shows the direction of movement of the coating device 4. A special pore-free and non-adhesive graphite type was selected as the carrier 1, which had an aligned structure of the individual graphite flakes (Sigraflex from Sigri). In a further process step, the liquid (in the present case

Terpineol) evaporated in air by heating to approx. 200 ° C. Layer 3 was then dried together with carrier substance 1 in a vacuum drying cabinet at approx. 200 ° C. The titanium powder was already compacted. Furthermore, the material was subjected to a multi-stage heat treatment. To this end, the layer

3 introduced on the carrier substance 1 in a vacuum oven, the vacuum of which was 10 -5 to 10-6 Torr.

First, the material was heated to a temperature of 500 C over a period of about 90 min and during

Maintained at this temperature for 30 min. Any remaining solvent (terpineol) is completely removed in this process. The material was then further heated to a temperature of about 900 ° C. over the course of about 30 minutes and held at this temperature for about 3 minutes. The titanium powder sintered together to form a coherent porous film. Care must be taken that this sintering temperature is not set too high so that the titanium layer does not stick to the carrier 1. After sintering, the material was cooled and the film was detached from carrier 1. The film was then cold rolled in a roll stand with rolls of 300 mm in diameter at a rolling speed of 2 m / min. The decrease in height due to this rolling pass wore 15 /., which corresponded to a reduction in porosity from 70% to 64%. The cold-rolled foil was then placed on a graphite powder-coated support 1 and subjected to a further heat treatment according to FIG. 1. The measured porosity was still 58%. Now a layer consisting of platinum was applied to the porous titanium foil in an electrochemical manner. The

2

Doping was 0.1 mg platinum per cm. After a suitable heat treatment, the current collector was further covered with a platinum metal b-zw. Platinum metal oxides existing electrocatalyst coated. In the present

The case was a mixture of ruthenium oxide

2 and iridium oxide in a total amount of 3 mg / cm film surface.

The process steps of cold rolling and sintering can be carried out several times in succession until the desired targeted density or porosity of the film or plate has been reached.

In principle, paste 2 can also be produced with the aid of a suitable liquid other than C. The application of the paste is also not bound to the coating device 4 for thin-layer plates, but can be carried out with the aid of any other suitable device. The condition is that a viscous, homogeneous paste is first produced and then applied as uniformly as possible to a non-adhesive substrate (carrier 1).

Execution example_II_

A current collector ^* for an electrochemical ozone cell in the form of a porous titanium foil 1.45 mm thick was produced as follows: On one with graphite powder (KS 75 from Lonza) coated support 1 made of fine-grained graphite (ground plate, quality Ringsdorff EK 72) was dry, free-flowing titanium powder 2 (Sumitomo, Osaka) in the form of a uniform layer using a movable coating device 4 (Camag thin-layer apparatus for chromatography) 3 applied. The layer thickness was approximately 1.9 mm; the area was a square with a side length of 200 mm. The whole was then subjected to a multi-stage heat treatment in a vacuum oven in order to sinter the titanium powder. The mixture was first heated from room temperature to 500 ° C. over a period of about 90 minutes and this temperature was kept constant for a further 30 minutes. The mixture was then heated to 1000 ° C. for 30 minutes and this temperature was maintained for 3 hours. After cooling to room temperature, the pre-sintered in this way

Titanium foil can be easily detached from the carrier 1, since the graphite powder had formed a protective layer. The thickness of the film after presintering was approx. 1.8 mm, the porosity 70%. Now the film was cold rolled in several passes in a roll stand with rolls of 130 mm in diameter. The decrease in height per stitch was approx. 0.1 mm, so that after 3 stitches a film thickness of approx. 1.5 was now achieved. The rolling speed was 1.2 m / min. Care must be taken that the total cross-sectional reduction before the next heat treatment does not exceed 30%, since otherwise the material could tear. The decrease in height per stitch should not exceed 15%. The rolling speed can advantageously be set to 1 to 30 m / min. The porosity had dropped to about 62% after cold rolling. The cold-rolled titanium foil was then subjected to a further sintering process in accordance with the heat treatment described above. ^* The thickness of the film was still after sintering approx.1.45 mm, the porosity approx. 59%. The porous titanium foil was now coated with platinum according to Example I. An additional layer consisting of PbO _p in

2 applied an amount of 15 mg / cm film surface.

By deliberately repeating the process steps of cold rolling in one or more passes and the heat treatment used for sintering, any desired film thickness and any porosity between 0 and that approximately corresponds to the loosely poured titanium powder can be achieved, which is primarily used for sintering heat treatment can be carried out under vacuum or protective gas.

After the last sintering process, the porous titanium foil is provided with a thin layer of platinum, on which another layer made of at least one platinum metal or one

Platinum metal oxide or PbO existing electrocatalyst layer is applied.

The process according to the invention enables the economical production of current collectors in the form of porous titanium foils and titanium plates of 0.1 to approximately 5 mm constant thickness with uniform, targeted porosity and practically any surface area, such as that required for the construction of large industrial ones electrochemical devices, in particular electrolysis apparatus (individual parts and entire batteries constructed according to the filter press principle) are required.

Claims

Patent claims

1. A process for producing a large-area current collector for an electrochemical cell in the form of a porous plate or foil with a targeted porosity made of titanium, starting from titanium powder, the latter directly or indirectly in the form of a uniform layer (3) on one Carrier (1) is applied and the layer (3) is subjected to a sintering process, characterized in that the layer (3) is subjected to a gradual heat treatment under vacuum or protective gas and pre-sintered to form a coherent porous film and that the latter is at least one times cold rolled and additionally sintered at least once after said stepwise heat treatment and finally coated with an electrocatalyst.

2. The method according to claim 1, characterized in that the heat treatment of the layer (3) on the same original carrier (1) is carried out and in the subsequent steps carried out under vacuum from 10 -5 to 10-6 Torr:

- heating up to 500 ° C in the course of 30 to 90 min,

- keeping the temperature at 500 ° C for 30 min,

- heating in the course of 30 min from 500 ° C to 900 to 1000 ° C,

- Sintering the layer by keeping the temperature between 900 and 1000 ° C for 3 hours.

3. The method according to claim 1, characterized in that the presintered film in one or more rolling Stitches with a decrease in height of at most 15% per stitch and a total decrease in height of at most 30% at a rolling speed of 1 to 30 m / min reduced in thickness and then during! .1 / 2 h is sintered at 500 ° C and for a further 3 h at 1100 ° C.

4. The method according to claim 3, characterized in that the process steps of cold rolling and subsequent sintering are carried out several times in succession.

5. The method according to claim 1, characterized in that the sintered film is first provided with a platinum layer and additionally with a further layer consisting of at least one platinum metal or at least one platinum metal oxide.

6. The method according to claim 1, characterized in that the sintered film is first provided with a platinum layer and additionally with a further layer consisting of PbO.

7. The method according to claim 1 ,. characterized in that the titanium powder is applied directly in free-flowing, dry form as a layer (3) to a support (1) consisting of fine-grained graphite powder and coated with graphite powder.

8. The method according to claim 1, characterized in that the titanium powder is suspended in a liquid and the viscous, homogeneous paste (2) produced in this way in the form of a coherent, uniform layer (3) on a support (1) consisting of special pore-free, non-sticky graphite with an aligned structure of the individual graphite platelets, the liquid evaporates in air and the layer (3) is then dried in vacuo.

9. The method according to claim 8, characterized in that the liquid used for slurrying is Terpineol C _H o0, which is evaporated at 200 C and that the layer (3) is dried at 200 ° C in a vacuum.

10. The method according to claim 8, characterized in that the viscous paste (2) made of titanium powder with a particle size of 15 JU to 120 λi with very irregular shapes having branches and protuberances, which was produced from titanium sponge, and from terpineol in Mixing ratio 9 S titanium to 6 ml terpineol is produced.

11. The method according to claim 8, characterized in that the viscous paste (2) is applied to the carrier (1) with a movable coating device (4) for thin-layer plates.

B e z e i c h n u n g s l i s t e

1 carrier (graphite)

2 titanium powder or titanium paste

3 Even layer of powder or paste

4 Movable coating device (container tapering downwards)