TWI335305B - The metallic bipolar plate of solid oxide fuel cell with perovskite protective coating and method of manufacturing thereof - Google Patents

Description

1*335305 IX. Description of the Invention: [Technical Field] The present invention relates to performance improvement of solid oxide fuel cell (S0FC) metal 1 ic interconnects, in particular to the use of a stable 1 canalite structure (perovski te) oxide as a metal bipolar plate protection, the metal bipolar plate is resistant to high temperature oxidation, the metal bipolar plate can maintain the high conductivity of the original metal for a long time, and can also hinder the chromium The surface of the alloy generates a volatile gas of a high-valent chromium compound to enter the electrode and the electrolyte, thereby avoiding a decrease in power generation efficiency and life of the solid oxide fuel cell. [Prior Art]

In recent years, the bipolar plate components of solid-state oxidized fuel cells have been replaced by low-cost and easy-to-process high-temperature resistant alloys. These alloy materials usually contain Cr and A1, which form dense Cr2〇3 and Al2〇3 on the surface. Protect the alloy. Although such an oxide film can improve the high temperature oxidation resistance of the metal bipolar plate, its electrical resistivity is relatively high, and the higher the temperature at high temperature operation, the thicker the oxide film thickness, resulting in a significant increase in the resistance of the metal bipolar plate. It will hinder the current transfer of the solid oxide fuel cell, which will reduce its power generation efficiency. At present, research has been conducted to coat the perovskite structure oxide La^SrxMnOa on the surface of the metal bipolar plate to isolate the surrounding atmosphere of the alloy substrate, reduce the invasion of the alloy substrate by oxygen, and thus slow down the high temperature oxidation of the alloy. LahSrxMnOs itself is used in cathode materials and has high electronic conductivity, so it does not hinder the original high conductivity of metal bipolar plates.

Client's Docket No. : 0950089 6 TT's Docket No : 0912-A50929-TW / Draft-Final / Chiin 1*335305 [J.-H. Kim, R. -H. SongandS.-H. Hyun, "Effect of Slurry- Coated LaSrMn〇3 on the Electrical Property of Fe-Cr Alloy for Metallic Interconnect of S0FC” , Solid State Ionics, Vol. 174, pp. 185-191 (2004)], This document uses (La〇.85Srfl.i5)D The winning body of .9Mn〇3 was coated on the surface of Fe_16Cr alloy, and the coating (LaD.85Sn.15V9Mn〇3 test piece was sintered at 1200 ° C for 2 hours in Ar atmosphere + 10% H 2 . The results show that during the environmental sintering process (LaD.uSro.do.gMnOs will decompose into other unstable phases, and other oxides decomposed will cause the resistance of the metal bipolar plate to rise.

[JQ Li and P. Xiao, "Fabrication and characterization of La〇.sSr〇.2Mn〇3/meta 1 interfaces for application in SOFCs", Journal of the European Ceramic Society, Vol. 21, pp. 659-668 (2001 In this paper, La〇.8Sr〇.2Mn〇3 is screen printed on the metal interface and sintered at 1200 °C in different atmospheres. The results are shown in an Ar atmosphere and vacuum sintering, 1^. .88犷. .21411〇3 will be decomposed into (1^..881*().2)2|{11〇4+ again, (1(&,81')2〇3 with MnO, and air at 1200 °C , Ar atmosphere and vacuum sintering, will form a thick oxide film between the La.·eSro. 2Mn〇3 layer and the alloy substrate interface, which is not conducive to the conductivity of the metal bipolar plate. The current study in order to dense LahSrxMnCb Sintering on the surface of the metal bipolar plate is sintered at a high temperature of 1200 ° C, and generally the high temperature resistant alloy can not withstand the high temperature of 1200 ° C, which will form an oxide film with excessive thickness and high resistance on the surface of the alloy. Sintering in an inert atmosphere or under vacuum, but Lai-xSrxMn〇3 will decompose into other oxides in a low-oxygen partial pressure atmosphere at a high temperature of 1200 ° C. The decomposed oxide has a high electrical resistance, resulting in the resistance of the metal bipolar plate. Rising, reducing the power generation efficiency and life of solid oxide fuel cells

Client’s Docket No·: 0950089 TT*s Docket No : 0912-A50929-TW/Draft-Final/Chlin 7 1-335305 Life. SUMMARY OF THE INVENTION The object of the present invention is to coat a surface of a high temperature resistant alloy with a La^xSixMnC^ protective layer to prevent the Lai_xSrxMn03 protective layer from decomposing into other high-resistance oxides during sintering, resulting in a decrease in conductivity of the protective layer. Reduce the high temperature oxidation resistance of the alloy substrate. Therefore, the present invention provides a layer of 10 to 100 μm intact perovskite structure LakSixMnOs protective layer, which maintains the original high conductivity and effectively isolates the atmosphere outside the alloy substrate, and provides two-temperature oxidation resistance to the metal bipolar plate. Sexuality and maintain long-term south-temperature conductivity, extending the operational life of solid oxide fuel cells. Another object of the present invention is to reduce the formation of an oxide film between the La^SrxMnC^ protective layer and the alloy substrate interface during the sintering process of the La^SrxMnC^ protective layer. The formation of an excessively thick oxide film will greatly increase the resistance of the metal bipolar plate and reduce the power generation efficiency and operating life of the solid oxide fuel cell. [Embodiment]

The invention relates to a method for manufacturing a La^SixMnOs protective layer coating, which avoids decomposing Lai_xSrxMn〇33 into La^xSi^MnOw, (LahxSrxhMnOw, MnO, La2〇3 and SrO oxides) during sintering, and destroys the protective layer. Continuous compactness, and the above-mentioned decomposed oxides have high electrical resistance, so LahSrxMnC^ decomposition will be detrimental to the high-temperature oxidation resistance and electrical conductivity of the metal bipolar plates. Therefore, a complete continuous perovskite structure is sintered on the surface of the alloy. The protective layer of SrxMnOs can prevent the alloy from being invaded by the external atmosphere of 〇2, thereby improving the high temperature oxidation resistance of the metal bipolar plate. The Lai_xSrxMn〇3 itself has a south conductivity.

Client's Docket No. : 0950089 8 TT's Docket No : 0912-A50929-TW / Draft-Final / Chlin 1.335305 Properties, as long as La^xSrxMnC^ maintains the original structure without conversion to other oxides, the metal bipolar plate can be used for a long time. Maintain high conductivity and avoid the decrease in power generation efficiency and operating life of solid oxide fuel cells due to increased resistance. [Embodiment 1] Referring to Fig. 1, there is shown a flow chart for the production of a protective coating of La0.7Sr0.3MnO3 (hereinafter referred to as LSMO) of the present invention. The method for producing the LSMO powder of the embodiment of the present invention is not particularly limited, and a solid phase synthesis method, a liquid phase synthesis method, and a gas phase synthesis method can be used as long as the particle size of the prepared powder is 1 μm or less. The LSMO powder of the present embodiment is prepared by an oxide method to produce a ceramic powder having a stable perovskite structure, and then LSMO slurry is prepared. For the detailed production process, please refer to "Fig. 2". The first step is to mix the powder, first put the La203 powder into the high temperature box furnace and bake at a high temperature of 550 °C for 5 hours. Because La203 easily reacts with the moisture in the atmosphere to form La(OH)3, it needs to be baked. After weighing, the weight required for La203 is measured. After baking, the powder should be avoided from contact with moisture in the atmosphere. Then, the weights of La203, SrC03 and Μη02 powders are calculated by stoichiometric weighting. Mix 3 g of powder of the scale into a plastic bottle, add 1/2 bottle of high zirconia balls to the bottle, oxidize the ball with a diameter of 10 mm, and then pour 6 to 7 minutes of full alcohol. After being fixed on a planetary ball mill, wet ball milling is carried out for 24 hours to uniformly mix the powders together, and to reduce pellet formation and reduce the particle size of the powder, and to make the powder size and shape more uniform. After wet ball milling, it was placed in an oven at 90 ° C for drying, and the dried powder was sieved using a 350 mesh sieve to ensure that the powder was not agglomerated and the powder particle size was more evenly distributed. Next, a calcination treatment was carried out, and the mixed powder which was sufficiently ball-milled and sieved was placed and simmered at ll ° C for 3.5 hours. Simmering process

Client's Docket No. : 0950089 9 TT's Docket No : 0912-A50929-TW / Draft-Final / Chlin Γ335305 Isolation 1 removes carbon dioxide, water, (tetra) and other hydrocarbons from /ill, and finally π becomes the =S powder characteristics 'And by the thermochemical reaction to make the mixed powder process = C ' and through the simmering sm 〇 〇 〇 〇 X X X X X X 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 After the simmering is completed, the LSMO powder is subjected to XRD two brigade to check whether the powder is a full-touch structure. If the knives are entangled, the knives will continue to be treated for the second time until: The same Γ Γ 粉末 powder completely becomes LSM 〇 powder. Simmering place, do another cycle of wet ball milling, drying and sieving,

俨 is a uniform distribution. The preparation method of the perovskite structure powder-t it' xsrxMn〇3, 仏χ4, can further control the 疋Lai:xSrxMn〇3, 〇J 'χ^〇3, the preferred range is A preferred embodiment is to control at x = 0.3. The average particle size of the LSMO powder prepared by the preparation of the perovskite, and the final step of the structure is controlled to be less than 1 [xm. In the LSMO slurry preparation process of the present invention, the LSM(R) powder is weighed to a desired weight by a microbalance, and the powder is poured into a solvent (terpineol) and a combination (4) (ethylcellulose), and the weight ratio is about 10 : 4~5 : 0.2, the solvent ratio is slightly adjusted according to the consistency required for the HMC). After mixing the mixed slurry, the slurry is poured into a three-roller mixer. The slurry is made up of a large roller. After the pitch is repeatedly rolled and the sentence is repeated, the next smaller roller pitch is repeatedly rolled until the LSMO powder is evenly dispersed in the slurry. The adjusted LSMO charge is placed in a sealable container to avoid the volatilization of the LSMO charge solvent during cryopreservation, resulting in a change in the LSM slurry concentration. The high temperature resistant alloy used in the metal bipolar plate may be a nickel base alloy, a chromium base alloy or an iron base stainless steel. In this embodiment, 22〇5 duplex stainless steel (hereinafter referred to as 2205DSS) is used as the material of the metal bipolar plate, and the thermal expansion coefficient (TEC) of the general high temperature resistant alloy is generally used.

Client's Docket No. : 0950089 1〇TT's Docket No : 0912-A50929-TW/Draft-Final/Chlin 1-335305 Higher than LSMO, so the difference between the high temperature alloy and LSMO thermal expansion coefficient is not too large, the range is about 10 X 10_6/ °C~20 X 1 (T6/°C, avoiding the sintering process to break the LSMO protective coating. The composition and thermal expansion coefficient of each material are shown in Table 1. Table 1 Chemical composition (wt%) and thermal expansion coefficient IIIII of the test material Ύνη~I 77TT7r6~7v^T" Material Mn Ni Cr Mo Fe TEC ax (xlO'6/°C) 30〇C~1200〇C 2205DSS 1.46 5.20 22.73 2. 83 Bal. 18. 048 430SS 0.48 - 15.97 - Bal . 15.569 LSMO - - - - - 12.259

The LSMO slurry is coated on the surface of 2205DSS. The coating method is not limited. It can be brushed, immersed or screen printed. The thickness of the protective layer is controlled at 5~100 μπι'. We test LSMO below 1 μηη. The protective layer is not sufficient to protect the alloy substrate. Too thick will hinder the current conduction of the metal bipolar plate. Therefore, the thickness of the protective layer is preferably controlled at 20 to 80 μm, and the optimum is controlled at 20 to 60 μm. In this embodiment, the LSMO slurry is coated by screen printing, the thickness of the coating can be controlled by the screen, and the coating distribution is relatively uniform. The screen is made of 60 mesh mesh, and the thickness of the coated emulsion is 30 μιη, screen printing. The test piece (hereinafter referred to as 2205LSM) was placed in an oven and baked at 130 ° C to evaporate the slurry solvent. The baked test piece is placed in a high-temperature atmosphere furnace for sintering, and the air in the furnace is extracted by a mechanical pump, and then introduced into the furnace through an inert atmosphere. In this embodiment, the 2205DSS is protected by an N2 atmosphere to avoid high-temperature sintering to produce a large amount of oxide on the surface of the alloy substrate. The 2205LSM was sintered at a temperature of 1100 ° C for 1.5 hours, the rate of rise/fall was 100 ° C / hr, and the binder was removed at 400 ° C for 1 hour during the temperature rise. The sintering result is shown in Fig. 3, which is the first embodiment.

Client’s Docket No. : 0950089 TT's Docket No : 0912-A50929-TW/Draft-Final/Chlin 11 1-335305

SEM cross-sectional view. As shown in the figure, after sintering at 1100 ° C for 1.5 hours, the thickness of layer 10 was about 45 μηη, and no other oxides were found by XRD and EDS analysis, and the original perovskite structure was maintained. Therefore, the LSMO protective layer after sintering has high electron conductivity and chemical stability. Between the interface of layer 10 and layer 12, a single layer of dense and thin layer 11 is formed. The thickness of layer 11 is about 1~2 // m. The layer 11 is characterized by XRD and EDS. The main composition is Cr203 and (Cr, Μη ) 304 spinel phase telluride. The thickness of the layer 11 is very thin, and does not significantly affect the conductivity of the metal bipolar plate, and the layer 10 is rich in a large amount of ,, so that the layer 11 is easily converted into a highly conductive (Cr, )) 304, and the layer 11 It is very continuous and dense, which can more effectively hinder the diffusion of 〇2 to layer 12, which helps to slow the oxidation rate of metal bipolar plates. 2205LSM performs an oxidation kinetic analysis of 800 ° C in an air atmosphere, as shown in Figure 4. As seen from Fig. 4, the horizontal axis is the oxidation time, the vertical axis is the weight increase per unit area of the test piece, and the curve 31 is much lower than the curve 30, which shows that the 2205DSS has an LSMO protective layer which can effectively reduce the oxidation rate by 2.21 orders of magnitude, thus slowing down The thickness of the oxide layer of the alloy substrate is increased to avoid the rapid rise of the resistance of the metal bipolar plate, and the operating life of the solid oxide fuel cell is prolonged. The 2205LSM performs a high-temperature electrical measurement at 800 °C in an air atmosphere, as shown in Figure 5. As shown in Fig. 5, the horizontal axis represents the oxidation time, the vertical axis represents the resistance change amount of the cross-sectional area of the test piece, and the curve 40 is measured at a high temperature resistance of the air atmosphere of 800 ° C for 500 hours, and the resistance of the curve 40 increases with the operation time. The increase is due to the continuous growth of the oxide film thickness of the 2205DSS surface resistance, which causes the power generation efficiency of the solid oxide fuel cell to decrease with the increase of the operation time. Compared with curve 40, curve 41 has a high temperature resistance that decreases slowly with increasing operating time due to the layer

Client's Docket No. : 095(8)89 TT's Docket No : 0912-A50929-TW / Draft-Final / Chlin 12 1335305 10 effectively hinders the invasion of layer 2 to layer 12, so that the thickness of layer 11 between the layer and layer 12 interface does not follow The time increases and grows, and the layer 10 is rich in Μη, transforming the high-resistance Cr203 oxide of layer 11 into a lower-resistance (Cr, Mn) 304 spinel phase oxide, so the resistance is slow as the operation time increases. Reduction. In the above experiments, at 1100T: the sintered layer 1〇 can avoid the decomposition of LSM◦, still maintain a structurally complete and stable perovskite structure, effectively insulate the invasion of 02 to layer 12, and prevent the high resistance oxide film of 2205DSS. Rapid growth reduces the electrical conductivity of metal bipolar plates.

Example 2 In Example 2, 430 stainless steel (hereinafter abbreviated as: 430SS) was used as the metal bipolar plate material, and the LSMO powder production method, the LSMO slurry preparation method, the LSMO coating method, and the LSMO sintering process were all the same as in Example 1. The material composition and thermal expansion coefficient of 430SS are shown in Table 1. The sintering result is shown in Fig. 6 and is a SEM cross-sectional view of the second embodiment. As shown in the figure, the layer i〇a is sintered at ii〇〇°c for 1.5 hours, and its thickness is about 25 μm. It has not been found by XRD and EDS to find other oxides and still maintain the original perovskite structure. Therefore, the 'LSMO protective layer after sintering has high electron conductivity and chemical stability. Between the layer 10a and the layer 22 interface, a single layer of dense and thin layer 11a is formed, and the thickness is about 1~2#m. The main components of the identification by XRD and EDS are Cr2〇3 and (Cr,Mn)3〇4. Spinel phase oxide. The above results are similar to those of the embodiment 1, so that the layer l〇a sintered in the ll 〇〇 °C of the embodiment 2 can prevent the decomposition of the LSMO, and maintain the structurally intact and stable perovskite structure, effectively isolating the 02 layer 22 Invasion prevents the high-resistance oxide film of 430SS from growing rapidly and reduces the metal bipolar plate

Client’s Docket No. : 0950089 1 3 TT's Docket No : 0912-A50929-TW / Draft-Final / Chlin 1-335305 Conductivity. Example 3 In Example 3, 2205DSS was used as the metal bipolar plate material, and the LSMO powder production method, the LSMO slurry preparation method, and the LSMO coating method were the same as in the first embodiment. The 2205LSM of this example was changed to a 1000 ° C temperature N2 atmosphere for 2 hours, the rate of rise/fall was 100 ° C / hr, and the binder was removed at 400 ° C for 1 hour during the temperature rise.

The sintering result is shown in Fig. 7, which is a SEM cross-sectional view of the third embodiment. As can be seen, after the layer 10b was sintered at 1000 ° C for 2 hours, its thickness was about 30 μηη, and no other oxides were found by XRD and EDS analysis, and the original perovskite structure was maintained. Therefore, the LSMO protective layer after sintering has high electron conductivity and chemical stability. Between the layer 1 Ob and the layer 12b interface, a single layer of dense and thin layer lib is formed, and the thickness is about 1~2/im. The main components of the identification by XRD and EDS are Cr203 and (Cr, Mn)3〇4. Spinel phase oxide. The above results are similar to those of the first embodiment, so that the layer l〇b sintered in the case of the third embodiment can avoid the decomposition of the LSMO and maintain the structurally intact and stable perovskite structure, effectively separating the two directions. The layer 12b invades to prevent the rapid growth of the high-resistance oxide film of 2205 and reduce the conductivity of the metal bipolar plate. However, because the sintering temperature is lowered, the sintering bond strength of the layer l〇b is small, so the LSMO has a slight shedding phenomenon during the grinding and polishing process. Therefore, it can be inferred that the LSMO is sintered below 1000 ° C, and the LSMO cannot be sintered because of consideration. It is possible to use different high temperature furnace sintering and different thermocouples to measure the temperature. The sintering temperature can be ±50 °C, so the ideal sintering temperature of LSMO is about 950~1150 °C. The sintering time of 1 to 3 hours is a reasonable range.

Client's Docket No. : 0950089 XT's Docket No : 0912-A50929-TW / Draft-Final / Chlin 14 Γ335305 Comparative Example 1 Comparative Example 1 uses 2205DSS as a metal bipolar plate material, lSMO powder production method, LSM0 slurry preparation method and The lsmo coating method was the same as in Example 1. The 2205LSM of this Comparative Example 1 was changed to 12〇〇. (: The temperature was sintered in a N2 atmosphere for 2 hours, and the rate of rise/fall was 1 Torr (rC/hr), and the binder was removed at 4 〇ΐ for 1 hour during the temperature rise.

The sintering results are shown in Fig. 8 and are the SEM cross-sectional views of Comparative Example 1. As shown in the figure, layer i〇c is 12 烧结t: after sintering for 2 hours, its thickness is about 20 μηη, and it is decomposed into Lai_xSrxMnO (4), (LakSi^MnO^, La2〇) by XRD, EDS and ΕΡΜΑ. 3 and SrO and other oxides. Between layer 1 〇c and layer 12C interface, a multi-layered and irregularly distributed, different type of layer llc has a total thickness of about 5~8 μιη, which is identified by xrD, EDS and ΕΡΜΑ. The white portion of layer 11c is LaCr03, and the portion with darker color is composed of (Mn, Cr) 304 spinel phase mixed with Cr2〇3. The above results are compared with Example 1 'LSMO has been decomposed into other oxide layers 10c The resistance is relatively increased and is not a stable structure, and there is no intrusion of the layer 12c into the layer 12c. The corrosion resistance of the 22〇5DSS is not significantly improved, and the thickness of the layer llc is continuously increased in the operating environment. And the thickness of the layer lie after sintering is higher than that of the layer u of the embodiment 1, so the temperature resistance of the brake example 1 is absolutely higher than that of the embodiment 1, and the resistance increases with the increase of the operation time. Invented LSMO manufacturing method to avoid LSMO knife solution into other oxygen The material still maintains a structurally complete and stable perovskite structure. The three effectively insulates the ruthenium into the alloy substrate, prevents the high-resistance oxide film on the surface of the alloy from rapidly growing, and reduces the conductivity of the metal bipolar plate, resulting in solid oxidized fuel. The power generation efficiency and operating life of the battery are degraded.

Client’s Docket No. : 0950089 TT’s Docket No : 0912-A50929-TW/Draft-Final/Chlin 15 Γ335305 [Simplified Schematic] Figure 1 is a flow chart of the method for manufacturing the LSMO protective coating of the present invention. Figure 2 is a flow chart of the LSMO powder production of the present invention. Figure 3 is a SEM cross-sectional view of the 2205 LSM of the present invention sintered at 1100 ° C for 1.5 hours. Figure 4 shows the oxidation kinetics of air at 800 °C for 2205DSS and 2205LSM. Figure 5 is a plot of ASR versus time at 800 °C for 2205DSS and 2205LSM.

Figure 6 is a SEM cross-sectional view of the 430LSM of the present invention sintered at 1100 ° C for 1-5 hours. Figure 7 is a SEM cross-sectional view of the 2205 LSM of the present invention sintered at 1000 ° C for 2 hours. Figure 8 is a SEM cross-sectional view of the 2205 LSM of the present invention sintered at 1200 ° C for 2 hours. [Main component symbol description] 10, 10a, 10b, 10c LSMO layer; 11, 11a, lib, 11c oxide film; 12, 12b, 12c 2205 duplex stainless steel; 22 430 stainless steel; 30 2205DSS oxidation weight gain curve; 31 2205LSM oxidation Weight gain curve; 40 2205DSS ASR changes curve with time; 41 2205LSM ASR changes curve with time.

Client’s Docket No· : 0950089 16 TT's Docket No : 0912-A50929-TW / Draft-Final ! Chlin

Claims (1)

• τι v patent application scope 1 · A method for manufacturing a solid oxide fuel cell metal bipolar plate with a perovskite structure protective coating, comprising: preparing a perovskite structure La〇.7SrG.3Mn〇3 powder; LaG.7Sr().3Mn03 powder is slurried; the slurry is coated on the surface of a metal bipolar plate by screen printing, the metal bipolar plate is a high temperature resistant alloy, and the thermal expansion coefficient is in the range of 1 〇χ 1 〇 '6 / 〇 C ~ 20 xl 〇 -6 / ° C; The metal bipolar plate coated with the slurry is subjected to a sintering step at a sintering temperature of 950 to 115 〇 ° C, and the sintering time is a gas of nitrogen gas of Ar gas, 1 to 3 hours, and burned. 7Sr 〇.3Mn03 protects the formation of a 5~100/zm perovskite structure. The layer is on the surface of the metal bipolar plate. 17