JPH03297062A - Electrochemical element - Google Patents

Abstract

PURPOSE:To accomplish an electrochemical element having stable bond with solid electrolyte by forming electrode from a plurality of materials, which are laminated one over another while the mix proportion is varied in steps. CONSTITUTION:A plurality of materials are used mixedly and laminated one over another to form an electrode 2, wherein the mix proportion is varied in steps. That is, the laminative constitution of electrode shall be such that a materials, which is non-reactive with solid electrolyte 1 and having equal thermo-expansion characteristics to the solid electrolyte 1, is used to the innermost part 4 in contact with the solid electrolyte 1, and that the content of a material or materials not having the matching property with solid electrolyte 1 about thermo-expansion etc., but having excellent electroconductivity increases outward in steps. This enables stabilization of the bond of the interface between electrode 2 and electrolyte 1.

Description

[Detailed Description of the Invention] Industrial Application Fields of the Invention Solid electrolyte fuel cells, solid electrolyte oxygen sensors, oxygen pumps, and other electrochemical devices. Although YSZ (Ittria-stabilized zirconia) is often used as the solid electrolyte, for example, in high-temperature solid electrolyte stranded batteries (for example, Lat-xSrxCo is used as the cathode).
Belobus force such as Os-δ, etc. Ni/YSZ cermet has been considered as a promising anode due to its excellent electrical properties, thermal properties, and chemical properties. The bonding between the GL electrode and the electrolyte interface is an important element in chemical devices.If the bonding is inappropriate or if the bonding state changes over time in the environment in which the device is used, abnormal output may occur. Or change
Conventional 41: A material with excellent conductivity for electrodes, but whose thermal expansion cannot be matched with the solid electrolyte.A material whose thermal expansion can be matched even if its conductivity is lower. For example, in high-temperature solid electrolyte fuel cells, reducing electrode resistance is an important issue from the perspective of improving output, and in this respect, conductive materials are used as cathode materials. Although it is thought that a perovskite oxide based on δ with a high coefficient of thermal expansion is the most desirable, the only problem to be solved by the invention is the perovskite type oxide with a high coefficient of thermal expansion. In addition to having a large value of about twice that of YSZ, it also has a reactivity with YSZ, so it cannot be used. The mixing ratio of these materials is changed in stages to form electrodes that are laminated in sequence.4 For example, the innermost part in contact with the solid electrolyte is non-reactive with the solid electrolyte and has thermal expansion characteristics equivalent to that of the solid electrolyte. The electrode structure is made by laminating the electrodes in such a way that the mixture ratio of materials that lack thermal expansion consistency with the solid electrolyte but have excellent conductivity gradually increases toward the outside. A Function: With the above configuration, an electrode is formed in which multiple materials are sequentially laminated while changing their mixing ratio in stages, resulting in excellent electrical conductivity and a thermally stable bonding state with the solid electrolyte. FIG. 1 is a schematic diagram showing a partial cross section of a single cell of a high temperature solid oxide fuel cell in which a cathode according to the present invention is formed. 1 is a solid electrolyte sintered base made of yttria-stabilized zirconia (YSZ) with a thickness of 0.5 mm; 2 is a solid electrolyte sintered substrate;
, ss rs, tc o O to δ and Las, @S r
3 is a cathode with a thickness of 1.20 μm made of s, aMn Os-δ, and 3 is an anode with a thickness of XOOIJm made of Ni1, ・Y' S Z cermet. 4 is L
凰5 consisting of aa, tSrs, *MnOs, δ is L
a #, &S r a, eM v Os-δ/L
a s, * S r m, trCods-δ=8/2
Seed 6 is M
凰7 where n/Co=6/4 is M n / Co
= 4 / 6 [8 is M n / Co = 2
/ 8 becomes 凰 9 is Las, 5Srs, aCoO3
The thickness of each layer is 20 μm.
For comparison, 120μm thick sheet, sS
r 12c A cell with a cathode made only of OQs-δ, and a cell with a thickness of 120 μm, Lawei, S
A cell with a cathode consisting only of r s, pM n Os-δ was prepared, and the cells prepared in this manner were evaluated as follows: j-These cells were sent to RT in air. 1QO
The cell was subjected to a heat cycle test (continuous 5 C/times) at 0°C (temperature rise and fall at a rate of 300°C/h), and after the test, the cross section of the cell was observed and checked for any peeling between the solid electrolyte and the electrodes. Beta Result Laa, * S r s, 2c
o Take O*-δ, a*, sS r s, sM n
In the case of a cell with a cathode made of a mixture of Os-δ, no abnormality was observed at the bonding interface between the solid electrolyte and the electrode, indicating that the initial bonding state was maintained well. Similarly, there was no abnormality in the cell with a cathode made only of Sr@, *MnO3-δ.
+t in a cell formed with a cathode consisting of only
Peeling or microcracks occur in a part of the cathode, 7'.

Next, the electrode-electrolyte interfacial conductivity was measured. Five cells each formed with each cathode were heated at 1000°C for 50 minutes.
After being left for 0 hours, the interfacial conductivity at 1000°C before and after being left was measured and compared using AC impedance measurement.The results are shown in Table 1.The results and Laa, KaiSr@, *
C)Q formed a cathode consisting of a mixture of Mn0s-δ and Las, *Sr・, 2MnCL+-δ
In the case of a cell with a quad made of C7, there is almost no change in the interfacial conductivity, and the electrode-electrolyte interface bond is maintained well (force<, T, , a).
In the case of a cell that formed a quad consisting only of a, 's S r o, tC, o Oa, and δ, it was clearly observed that the junction state changed. Judging, Lag, S with better conductivity
Although it is judged that the electrode reaction rate and output can be improved by mixing r., aCoOs-δ, The electromotive force at 1000°C was measured using air as a reference gas.The results were as shown in Figure 2.

as r *, aCo Os-δ and L a s, as
The electromotive force of a cell with a cathode made of a mixture of r *, *M n Ot-δ shows almost the theoretical value. It has been revealed that forming a cathode consisting of a mixture of Las, Las, and Las as oxides significantly improves the bonding layer* between the electrode and the solid electrolyte, contributing to improvement and stabilization of the electrode reaction. @Sr・, 2C
oOs-δ and L a s, sS r I', 2M n
Similar results were obtained with other compositions in which the force < If it is, it is not limited to this (
~ Also, the mixing ratio and the number of laminated layers are not limited to those in the example, and it is also possible to use materials with three or more components instead of just two. ] Solid electrolyte is also YSZ
It is not limited to the above, but any method that exhibits the same function may be used (°C). Various known methods can be used to produce the cell. By using laminated electrodes with different conditions, it is possible to stabilize the bond between the electrode and electrolyte interface, and it is possible to obtain a highly reliable electrochemical device that is both thermally and electrically stable.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional diagram of an electrochemical device according to an embodiment of the present invention. FIG. 2 is a diagram showing the electromotive force of an oxygen concentration battery.

Claims (2)

[Claims] (1) An electrochemical device characterized in that an electrode made of a mixture of a plurality of materials is provided on a solid electrolyte substrate, and the electrodes are sequentially laminated while changing the mixing ratio of the materials in stages. (2) The solid electrolyte is yttria-stabilized zirconia (YS)
Z), the plurality of electrode materials are La_1_-_xSr_xCo
O_3_-δ (0≦x≦1, δ: oxygen vacancy amount) based perovskite oxide and La_1_-_xSr_xMnO_
2. The electrochemical device according to claim 1, wherein the electrochemical device is a perovskite-type oxide based on 3_-δ (0≦x≦1, δ: oxygen vacancy amount).