TWI594488B - Ceramic cathode material for solid oxide fuel cell and its preparation method - Google Patents

Description

Ceramic cathode material of solid oxide fuel cell and preparation method thereof

The invention relates to a ceramic cathode material for a solid oxide fuel cell and a preparation method thereof, in particular to a fuel cell field, which has high conductivity and a low thermal expansion coefficient in an operating temperature range of 500 to 800 ° C. Ceramic cathode material.

At present, there are many types of fuel cells and different classification methods. The commonly used classifications are based on electrolytes and operating temperature range. Among them, proton exchange membrane PEMFC and solid oxide SOFC have the most development potential.

At present, one of the main purposes of commercialization of SOFC is to reduce the operating temperature. Generally, the operating temperature of high-temperature SOFC is 800~1000 °C. However, high operating temperature will lead to many disadvantages, such as low open circuit voltage and high requirements on battery materials. High, the need to use more expensive ceramic materials in the battery stack can be solved when the connection plate and the time required for heating up are long. In addition, due to the high temperature operating environment, it is necessary to wait for a long time to warm up and cool down, causing tensile stress and compressive stress in the internal structure, resulting in damage of the battery components. As for the operation temperature of IT-SOFC of 500~800 °C, compared with the high temperature type SOFC, the improvement items such as the increase of battery life, the use of various connecting materials and the use of stainless steel as the connecting plate. However, the conductivity of the cathode material decreases and the activation polarity increases significantly as the temperature decreases under low temperature operation. Therefore, it is extremely important to develop medium/low temperature high performance cathode materials.

Solid oxide fuel cells have the following advantages:

(1) High efficiency: The traditional power generation process must generate energy through a series of energy conversions, because each energy conversion has part of the energy that is diffused into the air in the form of heat energy, resulting in low energy conversion efficiency, and the traditional thermal power generation efficiency is about 30%. . The fuel cell directly converts chemical energy into electrical energy. Without the combustion process, the energy loss is small, theoretically about 85~90%, and actually 40~60%.

(2) No noise: In the general power generation technology, including thermal power generation, hydropower generation, and nuclear power generation, the main equipment is mainly large turbines, and the operation process is very noisy. In contrast, the electrochemical reaction of a fuel cell does not require the operation of mechanical parts, and unlike conventional conventional power generation, it can be made into a noise-free power generation system.

(3) low contamination: After generating electrical energy through coal, oil and nuclear power, will generate a lot of harmful substances such as SO _x, NO _x, Co _x with nuclear waste and the like can cause pollution of air, water and the environment. Because the fuel cell does not need to undergo a combustion process, the power generation method is relatively clean. If hydrogen is used as the fuel, the product is clean water after the reaction, which is a very environmentally friendly way of generating electricity.

(4) Variety of fuel selection: Specific fuel cell stacks can use energy sources other than hydrogen. Because of the low density of hydrogen and the inconvenient storage, liquid hydrogen energy is used as fuel, such as alcohol or liquid petrochemical fuel. Can provide more convenience and durability.

At present, the most widely used high-temperature SOFC cathode material has problems in that the operating temperature is high, resulting in poor conductivity, thermal expansion and stability of the cathode, resulting in difficulty in large-scale commercial development, and therefore high conductivity at low and medium temperatures. Rate, electrolyte compatibility and good stability. Currently, the three structures of perovskite, cubic fluorite and pyrochlore meet these requirements. The development trend of perovskite is in China.

The following conditions are required for medium temperature cathode materials:

(1) Stability: From room temperature to operating temperature range, the cathode material must have chemical, crystal, morphology and dimensional stability, as well as other components such as electrolytes and connecting materials with good chemical stability.

(2) Conductivity: The cathode must have high ion conduction and electron conduction to reduce ohmic polarization.

(3) Thermal expansion: It is necessary to match the thermal expansion of other components such as electrolytes and connecting materials to avoid deformation, shedding and cracking.

(4) Porosity: In order to allow gas to penetrate into the electrode reaction, the cathode material must have a porosity of 30%.

(5) Catalytic ability: It has a good catalytic ability for oxygen to dissociate the oxygen molecule.

In the early days, the cathode material was made of a noble metal such as platinum, palladium or silver. Although it has good electrical conductivity, it is expensive and silver is volatile at high temperatures. At present, it is found that Ln _1-x A _x MO _3+δ (Ln is a lanthanoid element, A is an alkaline earth element and M is a transition metal element) having a perovskite structure conforms to the conductivity requirement of the cathode material. Generally, the alkaline earth element is added to LnMO ₃ to improve the conductivity of the cathode material at a high temperature, and the charge deficiency caused by the partial replacement of the rare earth element by the alkaline earth element partially promotes the conversion of the valence of the excessive metal element, or Oxygen vacancies are formed under certain conditions to maintain the lattice neutrality and thus the conductivity.

LaCoO _3-δ is a typical perovskite structure material, which has a rhombohedral structure at normal temperature, and a twisted octahedral structure (CoO ₆ ^9- ) is formed in the middle, and a phase transition occurs at a temperature of 509 ° C. The rhombohedral structure is converted into a cubic structure. LaCoO _3-δ cathode material is a mixed conductor with electronic and ionic conductivity characteristics, and its conductivity is semiconductor. However, according to the literature, LaCoO _3-δ and LaCo _0.4 Ni _0.6 O _3-δ are currently prepared by sol-gel method. Although it has high conductivity at 500 ° C, it has obvious potential for application to a medium temperature SOFC cathode, but its thermal expansion coefficient and sintering temperature are too high, which is a problem that is extremely difficult to overcome.

Therefore, if it is possible to develop a medium/low temperature type high performance SOFC cathode material, it is mainly to replace the Ni and Co at the B site with elements having similar atomic radii to increase the oxygen vacancy generation and reduce the thermal expansion coefficient, and adopt solid state synthesis. The preparation of the method, the selection of the best parameters for microstructure and electrical analysis, the development of a newer and lower cost new cathode material, this should be an optimal solution.

The present invention provides a ceramic cathode material for a solid oxide fuel cell and a preparation method thereof, which comprises mixing a ruthenium-containing compound, a cobalt-containing compound, a nickel-containing compound and a copper-containing compound to prepare a medium-low temperature type. The ceramic cathode material is capable of achieving high electrical conductivity and lowering the coefficient of thermal expansion in a medium/low temperature environment.

The ceramic cathode material of the above solid oxide fuel cell can be achieved, and the chemical formula of the ceramic cathode material is: LaCo _z Ni _y Cu _x O _3-δ , wherein the x+y+z=1 and δ is an oxygen vacancy value.

More specifically, the x is 0.01 to 0.3, the y is 0 to 0.89, and the z is 0.1 to 0.99.

More specifically, the ceramic cathode material of the solid oxide fuel cell is a mixture of a ruthenium-containing compound, a cobalt-containing compound, a nickel-containing compound, and a copper-containing compound, and is synthesized by solid state synthesis or wet synthesis. Prepared by the method.

More specifically, the cerium-containing compound is a cerium-containing oxide, a cerium-containing chloride, a cerium-containing nitrate, a cerium-containing acetate, a cerium-containing oxalate or a cerium-containing organic metal. Salt.

More specifically, the cobalt-containing compound is a cobalt-containing oxide, a cobalt-containing chloride, a cobalt-containing nitrate, a cobalt-containing acetate, a cobalt-containing oxalate or a cobalt-containing organic metal salt. class.

More specifically, the nickel-containing compound is a nickel-containing oxide, a nickel-containing chloride, a nickel-containing nitrate, a nickel-containing acetate, a nickel-containing oxalate or a nickel-containing organic metal salt. class.

More specifically, the copper-containing compound is a copper-containing oxide, a copper-containing chloride, a copper-containing nitrate, a copper-containing acetate, a copper-containing oxalate or a copper-containing organic metal salt. class.

The method for preparing a ceramic cathode material of the solid oxide fuel cell of the present invention comprises the following steps: (1) pre-baking the ruthenium-containing compound, burning the water gas, adding the cobalt-containing compound, and then doping the nickel-containing compound. Compound and copper-containing compound, the prepared powder is subjected to ball milling mixing, pulping and drying procedures; (2) the powder is calcined, the powder is prepared, and then subjected to secondary ball milling, and then baked again after pulping. Dry, after that, the dried powder is pressed into a green ingot; (3) after the raw embryo is deesterified and sintered, a sintered compact cathode block is formed, and the cathode block is used as a ceramic cathode material. Measurement analysis.

More specifically, the ruthenium containing compound is a ruthenium containing oxide.

More specifically, the cobalt-containing compound is a cobalt-containing oxide.

More specifically, the nickel-containing compound is a copper-containing oxide.

More specifically, the copper-containing compound is a copper-containing oxide.

More specifically, the content of doped cobalt in the cathode block is 10 to 99 atom%.

More specifically, the content of doped nickel in the cathode block is 0 to 89 atom%.

More specifically, the content of doped copper in the cathode block is 1 to 30 atom%.

More specifically, the copper-containing compound is doped with a molar percentage of 5 to 30%.

The method for preparing a ceramic cathode material of another solid oxide fuel cell of the present invention comprises the following steps: (1) dissolving a quantitative ruthenium-containing compound, a cobalt-containing compound, a nickel-containing compound, and a copper-containing compound in a solvent. Medium, configured to contain a solution of a fixed metal ion ratio; (2) further adding a precipitating agent to precipitate ions in the solution as a precipitate, followed by filtration, washing and drying; and (3) heat treatment to form a ceramic cathode Material powder.

More specifically, the ruthenium-containing compound is ruthenium-containing chloride, ruthenium-containing nitrate, ruthenium-containing acetate, ruthenium-containing oxalate or ruthenium-containing organometallic salt.

More specifically, the cobalt-containing compound is a cobalt-containing chloride, a cobalt-containing nitrate, a cobalt-containing acetate, a cobalt-containing oxalate or a cobalt-containing organometallic salt.

More specifically, the nickel-containing compound is a nickel-containing chloride, a nickel-containing nitrate, a nickel-containing acetate, a nickel-containing oxalate or a nickel-containing organometallic salt.

More specifically, the copper-containing compound is a copper-containing chloride, a copper-containing nitrate, a copper-containing acetate, a copper-containing oxalate or a copper-containing organometallic salt.

More specifically, the content of doped cobalt in the ceramic cathode material powder is 10 to 99 atom%.

More specifically, the content of doped nickel in the ceramic cathode material powder is 0 to 89 atom%.

More specifically, the ceramic cathode material powder has a doped copper content of 1 to 30 atom%.

More specifically, the copper-containing compound powder is doped with a molar percentage of 5 to 30%.

1 is a flow chart showing the preparation of a ceramic cathode material of a solid oxide fuel cell of the present invention and a preparation method thereof.

Fig. 2 is a graph showing the thermal expansion coefficient of the ceramic cathode material of the solid oxide fuel cell of the present invention and a preparation method thereof.

Fig. 3 is a graph showing the conductivity analysis of the ceramic cathode material of the solid oxide fuel cell of the present invention and a method for preparing the same.

Fig. 4 is a graph showing the conductivity data of the ceramic cathode material of the solid oxide fuel cell of the present invention and a preparation method thereof.

Fig. 5 is a flow chart showing another embodiment of the ceramic cathode material of the solid oxide fuel cell of the present invention and a preparation method thereof.

The foregoing and other technical contents, features and effects of the present invention are as follows The detailed description of the preferred embodiment with reference to the drawings will be apparent.

1 is a flow chart showing the application of a ceramic cathode material for a solid oxide fuel cell of the present invention and a preparation method thereof. The present invention can carry out a ruthenium-containing compound, a cobalt-containing compound nickel-containing compound, and a copper-containing compound. Mixed and prepared by solid state synthesis, and the ruthenium-containing compound (oxide) used in the present embodiment is La ₂ O ₃ , the cobalt-containing compound (oxide) is Co ₃ O ₄ , and the nickel-containing compound (Oxide) is NiO, and the copper-containing compound (oxide) is CuO. As can be seen from the figure, the ceramic cathode material (cathode block) applied to the fuel cell is prepared by: 1.La ₂ O ₃ powder After the calcination is carried out, the water gas is burned off, Co ₃ O _{4 is} added, and then CuO and NiO powder are doped, and the prepared powder is subjected to ball milling mixing, slurrying and drying process 101; 2. The powder is calcined and finished. Preparation of samarium cobalt nickel-copper oxide (LaCo _0.4 Ni _0.6-x Cu _x O _3-δ ) powder, followed by secondary ball milling, and drying again after pulping, after which the dried powder is pressed Producing the raw embryo 102; (in the present embodiment, the chemical formula LaCo _z Ni _y after preparation is further set Cu _x O _3-δ , where y=y'-x, z=1-y', y'=0.6, and x+y+z=1)3. The raw embryo is de-esterified and sintered, and then sintered. The dense cathode block was subjected to measurement analysis 103.

As shown in Fig. 2, after LaCoO _{3-δ is} doped with CuO and NiO, a cathode block of LaCo _0.4 Ni _0.6-x Cu _x O _3-δ is prepared, and then the cathode block is subjected to 0 to 900 ° C. The thermal expansion coefficient analysis shows that x is 0.01 to 0.2 (x = 0.2 means Cu content of 20 atom% doped, y means doped Ni content, z means doped Co content), and its thermal expansion coefficient It is the lower the driving force, in which LaCo _0.4 Ni _0.6-x Cu _x O _3-δ (x is 0.2), the performance of lowering the coefficient of thermal expansion is the best; in addition, in order to compare with the technique of the present invention, three In the experimental analysis, the first group is the cathode block of LaCoO _3-δ undoped oxide, the second group is the cathode block of LaCoO _3-δ doped NiO, and the third group is LaCoO _3-δ doped CuO and The cathode bulk material of NiO has a coefficient of thermal expansion (CTE) of 23.9 (10 ^-6 /°C) measured at a normal temperature of 800 ° C, and the coefficient of thermal expansion (CTE) measured by the second group is 18.3 (10 ^-6 /°C), the coefficient of thermal expansion (CTE) measured by the third group is 15.6 (10 ^-6 /°C). It can be seen that LaCoO _{3-δ is} doped with CuO and NiO to prepare LaCo. _0.4 Ni _0.6-x of thermal expansion of the cathode block material of Cu _x O _3-δ is Coefficient is the lowest, although the doped NiO product was also possible to reduce the coefficient of thermal expansion, but the experiment of the present invention, since the product was not doped NiO reduce the sintering temperature and increase the conductivity, so that the present invention is prepared by doping CuO and NiO an LaCo _{The characteristics of the 0.4} Ni _0.6-x Cu _x O _3-δ cathode block are significantly better than those produced by doping NiO.

As shown in Fig. 3 and Fig. 4, the conductivity analysis curve and the conductivity data analysis table of different x values are LaCo _0.4 Ni _0.6-x Cu at the sintering temperature (1100, 1225, 1300, 1400 °C). The cathode block of _x O _3-δ is subjected to DC electrical measurement in the range of 500 to 800 ° C. It can be seen from the figure that after doping CuO and NiO of the present invention, the conductivity can be effectively improved, although x=0.3. The electrical conductivity will be lower than the electrical conductivity of x = 0.2, but it is still much higher than the conductivity of the conventional ceramic cathode material (100 S ‧ cm ^-1 ).

It can be seen from Fig. 2~4 that after doping CuO and NiO with LaCoO _3-δ , the Cu doping amount can increase the sintering temperature and increase the conductivity, and the doping Cu content is 0.2 atom% (x=0.2). The characteristics of the performance are the best, but in addition to x = 0.2, the range of x is 0.01 ~ 0.3 (including 0.01, 0.0125, 0.025, 0.0375, 0.05, 0.0625, 0.075, 0.0875, 0.1, 0.1125, 0.125, 0.1375, 0.15 , 0.1625, 0.175, 0.1875, 0.2, 0.2125, 0.225, 0.2375, 0.25, 0.2625, 0.275, 0.2875, 0.3), and the content of doped copper in the cathode block is 1 to 30 atom%.

Since x+y+z=1, the range of x is 0.01~0.3, and the range of y is 0~0.89, the range of z is 0.1~0.99, and the content of doped cobalt in the cathode block is 10~99 atom%, the content of doped nickel in the cathode block is 0~89 atom%, and the cathode block is doped The content of copper is 1~30 atom%.

However, in addition to the oxides used in the above examples, other ruthenium-containing compounds, cobalt-containing compounds, nickel-containing compounds, copper-containing compounds (such as chlorides, nitrates, acetates, oxalates) can be used. Or organometallic salts) to prepare ceramic cathode materials of the formula LaCo _z Ni _y Cu _x O _3-δ , which can only be used due to chloride, nitrate, acetate, oxalate or organometallic salts. The preparation method is as shown in FIG. 5, and the preparation method is as follows: 1. First, the quantitative ruthenium-containing compound, the cobalt-containing compound, the nickel-containing compound and the copper-containing compound are dissolved in a solvent, and a solution 501 containing a fixed metal ion ratio; 2. adding a precipitant to precipitate ions in the solution as a precipitate, followed by filtration, washing and drying 502; and 3. performing heat treatment to form a ceramic cathode material powder 503 .

The ceramic cathode material of the solid oxide fuel cell provided by the invention and the preparation method thereof are compared with other conventional techniques, and the advantages thereof are as follows:

1. The present invention combines a ruthenium-containing compound, a cobalt-containing compound, a nickel-containing compound, and a copper-containing compound, and prepares LaCo _z Ni _y Cu _x O _3-δ by solid state synthesis or wet synthesis. The cathode block is characterized by high electrical conductivity and reduced thermal expansion coefficient in a medium/low temperature environment (500~800 °C).

2. The LaCo _z Ni _y Cu _x O _3-δ ceramic cathode material of the present invention can effectively reduce the sintering temperature and the thermal expansion coefficient as the Cu doping amount increases, and increase the relative density to increase the conductivity.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

Claims (24)

A ceramic cathode material for a solid oxide fuel cell, the chemical formula of the ceramic cathode material being: LaCo _z Ni _y Cu _x O _3-δ , wherein the x+y+z=1 and δ is an oxygen vacancy value, and the x It is 0.01 to 0.3, the y is 0.3 to 0.89, and the z is 0.1 to 0.9. The ceramic cathode material of the solid oxide fuel cell according to claim 1 , wherein the cerium-containing compound, the cobalt-containing compound, the nickel-containing compound, and the copper-containing compound are mixed and solid-state synthesized or Prepared by wet synthesis. The ceramic cathode material of the solid oxide fuel cell according to claim 2 , wherein the cerium-containing compound is cerium-containing oxide, cerium-containing chloride, cerium-containing nitrate, cerium-containing acetate , bismuth-containing oxalate or cerium-containing organometallic salts. The ceramic cathode material of the solid oxide fuel cell according to claim 2 , wherein the cobalt-containing compound is a cobalt-containing oxide, a cobalt-containing chloride, a cobalt-containing nitrate, and a cobalt-containing acetate. , cobalt-containing oxalate or cobalt-containing organometallic salts. The ceramic cathode material of the solid oxide fuel cell according to claim 2 , wherein the nickel-containing compound is a nickel-containing oxide, a nickel-containing chloride, a nickel-containing nitrate, and a nickel-containing acetate. Nickel-containing oxalate or nickel-containing organometallic salts. The ceramic cathode material of the solid oxide fuel cell according to claim 2 , wherein the copper-containing compound is a copper-containing oxide, a copper-containing chloride, a copper-containing nitrate, or a copper-containing acetate. Copper-containing oxalate or copper-containing organometallic salts. A method for preparing a ceramic cathode material of a solid oxide fuel cell by calcining a compound containing ruthenium, extruding water vapor, adding a compound containing cobalt, and then doping a compound containing nickel and a compound containing copper , the prepared powder is ball milled, pulped, baked Dry process; the powder is simmered, the powder is prepared, and then subjected to secondary ball milling, and then dried again after pulverization. Thereafter, the dried powder is pressed into an ingot to form a green embryo; After sintering, a sintered dense cathode block is formed, and the cathode block is used as a ceramic cathode material for measurement analysis. A method of preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the ruthenium-containing compound is a ruthenium-containing oxide. The method for producing a ceramic cathode material of a solid oxide fuel cell according to claim 7 , wherein the cobalt-containing compound is a cobalt-containing oxide. A method of preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the nickel-containing compound is a nickel-containing oxide. A method of preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the copper-containing compound is a copper-containing oxide. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the cathode block has a cobalt doping content of 10 to 99 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the content of doped nickel in the cathode block is 0 to 89 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the cathode block has a doped copper content of 1 to 30 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 7 , wherein the copper-containing compound is doped with a molar percentage of 5 to 30%. A method for preparing a ceramic cathode material of a solid oxide fuel cell, the method is: First, the quantitative ruthenium-containing compound, the cobalt-containing compound, the nickel-containing compound, and the copper-containing compound are dissolved in a solvent, and are configured to contain a solution of a fixed metal ion ratio; and then a precipitant is added to precipitate ions in the solution. After the precipitate is precipitated, it is further subjected to filtration, washing and drying; and heat treatment is performed to form a ceramic cathode material powder. The method of preparing a cathode material such as a ceramic solid oxide fuel cell applications of the scope of the patent to item 16, wherein the lanthanum-containing compound containing lanthanum chloride, lanthanum nitrate, and lanthanum acetate-containing, lanthanum-containing Oxalate or an organometallic salt containing cerium. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the cobalt-containing compound is a cobalt-containing chloride, a cobalt-containing nitrate, a cobalt-containing acetate, and a cobalt-containing compound. Oxalate or an organometallic salt containing cobalt. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the nickel-containing compound is a nickel-containing chloride, a nickel-containing nitrate, a nickel-containing acetate, and a nickel-containing compound. Oxalate or an organic metal salt containing nickel. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the copper-containing compound is a copper-containing chloride, a copper-containing nitrate, a copper-containing acetate, or a copper-containing compound. Oxalate or an organic metal salt containing copper. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the ceramic cathode material powder has a cobalt doping content of 10 to 99 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the ceramic cathode material powder has a nickel-doped content of 0 to 89 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the ceramic cathode material powder has a doped copper content of 1 to 30 atom%. The method for preparing a ceramic cathode material for a solid oxide fuel cell according to claim 16 , wherein the copper-containing compound is doped with a molar percentage of 5 to 30%.