RU2064210C1 - Electrochemical device - Google Patents

Abstract

FIELD: high-temperature electrochemical devices such as thermal elements, oxygen pumps, electrolyzers, and gas analyzers of oxygen-containing gases, miscellaneous devices based on stabilized zirconium dioxide. SUBSTANCE: electrochemical device has electrodes, electric connector, and solid electrolyte layer made of mixture of metal oxides including zirconium dioxide, cobalt oxide, and oxide of metal chosen from group including calcium oxide, magnesium oxide, oxides of rare-earth elements and their mixtures. Electrolyte layer composition is as follows, mass percent: zirconium dioxide, 75-97; cobalt oxide, 0.013-1.97; metal oxide, the balance. Other components of structure have in their composition, pass percent: zirconium dioxide, 0.9-45; cobalt oxide, 50.35-98.9; metal oxide, the balance. EFFECT: improved composition.

Description

 The invention relates to the field of high-temperature electrochemical devices with solid oxide electrolyte and can be used in the manufacture of fuel cells, oxygen pumps, electrolyzers and gas analyzers of oxygen-containing gases and other devices based on stabilized zirconia.

 Known solid oxide fuel cell of a tubular design, which is a porous pipe that provides an oxidizer supply, on which the layers of the cathode, electrolyte, anode are applied sequentially, while the electrolyte and anode have a gap along the generatrix, in which the layers that play the role of current passage are placed [1] Fuel cell planar structure [2] is made in the form of a package of plates of two types: a plate formed by layers of a cathode, electrolyte, anode, and a plate that acts as a current passage and a gas separation layer, and having longitudinal on the surface (recesses for supplying and removing reagents). A monolithic solid oxide oxygen pump [3] is known in which the cathode, anode and gas separation layers are made of lanthanum manganite, and zirconia stabilized with yttrium is used as the electrolyte.

 Closest to this invention is a high temperature solid electrolyte fuel cell and ceramic electrodes [4] The cell contains a porous cathode of electrically conductive ceramics, a porous anode of the same electrically conductive ceramic, and a solid electrolyte of oxide ion-conducting ceramic based on stabilized hafnium or zirconia.

 A disadvantage of the known electrochemical device is its low electrical characteristics.

 The objective of the invention is the creation of a high-temperature electrochemical device (wind turbine) with satisfactory electrical characteristics in combination with an increased service life in conditions of multiple thermal cycling.

The specified technical result is achieved in that: in an electrochemical device containing electrodes, an electrical connector and a solid electrolyte layer made of a mixture of metal oxides, including zirconium dioxide and a metal oxide selected from the group consisting of: calcium oxide, magnesium oxide, rare earth oxides , or mixtures thereof, the mixture of metal oxides additionally contains cobalt oxide in the following ratio of components (wt.)
for electrolyte layers:
zirconium dioxide from 75 to 97
cobalt oxide CoO from 0.013 to 1.97,
metal oxide the rest is up to 100
for other structural elements:
zirconium dioxide from 0.9 to 45
cobalt oxide CoO from 50.35 to 98.9;
metal oxide the rest is up to 100
Examples of specific performance:
Example 1. Monolithic fuel cell.

Two materials of the following compositions M1 were prepared by coprecipitation: ZrO ₂ 97 wt. MgO 2.987, CoO 0.013 wt. and M2: ZrO ₂ 45 wt. MgO 4.65, CoO 50.35 wt. From the obtained powders masses EM1 and EM2 were prepared, containing an additional 7% solution of rubber in gasoline at a weight ratio of powder to solution of 0.8, and films of P1 and P2 were cast 0.3 mm thick. From the film P1, rolled to a thickness of 0.07 mm, square blanks of solid electrolyte (E) were cut. Square blanks of cathodes (K) and anodes (A) were cut from P2 film, rolled to a thickness of 0.15 mm. From the film P2, rolled to a thickness of 0.07 mm, square blanks of gas separation layers (PC) are cut. Between two layers of the non-rolled P2 film a mesh of cotton fibers with a diameter of 0.3 mm was laid and they were jointly rolled to a thickness of 0.6 mm, after which square blanks of switching and gas supply layers (TP) were cut down. The blanks are collected in a package of three sets of sequentially collected layers: PC, TP, K, E, A, TP, PC. The collected package is pressed at a pressure of 500 kg / cm ² and sintered at a temperature of 1400 ^o C in air for 1 hour. Using glass solder, the opposite side faces of TP to A and K were sealed and gas and such collectors were installed.

 Example 2. Tubular fuel cell.

Two materials of the following compositions M1 were prepared by coprecipitation: ZrO ₂ 75 wt. Y ₂ O ₃ 23.03; CoO 1.97 wt. and M2: ZrO ₂ 0.9 wt. Y ₂ O ₃ 0.2, Coo 98.9 wt. From the obtained powders masses EM1 and EM2 were prepared, containing an additional 7% solution of rubber in gasoline at a weight ratio of powder to solution 1 0.8 and films P1 and P2 were cast 0.3 mm thick. A porous tube with a wall thickness of 1 mm was formed from M2 by extrusion. The P1 film, rolled to a thickness of 0.07 mm, is laid between two layers of a P2 film, rolled to a thickness of 0.2 mm, and they are jointly rolled to a thickness of 0.35 mm. A blank was cut from the created multilayer structure, which was deposited by isostatic pressing at a pressure of 1000 kg / cm ₂ on the outer surface of the tube with an overlap of edges of 2 mm, and heat treatment was carried out at a temperature of 1150 ^o C for 1 hour. The surface of the tube was opened by flat grinding in the place of overlapping, and EM2 spoil 0.5 mm thick and a width equal to the gap of the lower electrode layer was deposited in the gap between the electrolyte and the outer electrode layers. The structure was sintered at a temperature of 1450 ^° C in air for 1 hour, after which the joints were sealed with glass weld, between the ends of the electrolyte layer and the current passage layer.

The electrochemical devices formed by the above-described method had good thermomechanical properties (they could withstand 50 heating-cooling thermal cycles from room temperature to 900 ^o С for 2 hours without visible changes) and made it possible to obtain current densities of up to 2 A / cm ² in short-term modes. Their enhanced characteristics are apparently due to the fact that all their constituent layers have the same set of chemical elements. This contributes to the formation between the formed functional layers of transition layers with a smooth change in the concentration of cobalt with a constant ratio of the concentration of the remaining ingredients, and as a result, a smooth change in the physicomechanical characteristics in the multilayer structure. Obviously, the formation of such relatively extended transition layers between the electrodes and the electrolyte determines the obtained high electrochemical characteristics of such structures. A smooth change in the concentration of chemical elements in the layers forming the electrochemical device allows us to predict a higher stability of its characteristics over time, because the main reason for their deterioration is the mutual diffusion at the boundaries between heterogeneous layers.

Information sources
1. US patent N 5085742, CL. MKI H O1 M 6/00, 1992.

2. The patent of Germany N 3922673, class. MKI N 01 M 8/12, 1989
3. US patent N 4877506, CL. MKI C 25 V 9/00, 1989.

 4. US patent N 4459341, CL. MKI H O1 M 8/12, 1984.

Claims (1)

 An electrochemical device containing electrodes, an electrical connector and a solid electrolyte layer made of a mixture of metal oxides, including zirconia and a metal oxide selected from the group consisting of: calcium oxide, magnesium oxide, rare earth oxides, or mixtures thereof, characterized in that the mixture of metal oxides additionally contains cobalt oxide in the following ratio of components, wt. for electrolyte layers:
Zirconium dioxide 75 97,
Cobalt oxide CoO 0.013 1.97,
Metal oxide The rest is up to 100%
For other structural elements:
Zirconium dioxide 0.9 45,
Cobalt oxide CoO 50.35 98.3,
Metal oxide The rest is up to 100%