A fluorine-doped modified ceria-based solid electrolyte material and a preparation method thereof

Abstract

The application relates to the field of solid oxide fuel cell technology, in particular to a fluorine-doped modified cerium oxide-based solid electrolyte and a preparation method thereof, and the chemical formula of the electrolyte material is as follows: CeO 2‑y F y , wherein 0.1<=y<=0.6; y=0.4 in the formula. The preparation method is as follows: CeF3 powder, nano CeO2 powder and powder are weighed according to the stoichiometric ratio and mixed, a certain amount of ethanol is added to the mixed powder, and grinding is conducted until the ethanol is completely volatilized; the composite obtained in S1 is put into a container and sintered at high temperature in a high-temperature furnace; the sintered material obtained in S2 is ground to obtain the fluorine-doped modified cerium oxide-based solid electrolyte powder; the low-temperature solid oxide fuel cell prepared by the method has the advantages that the stability of the cell is effectively improved, the voltage decay rate is 0.0047 V / h under a current density of 158.7 mA cm ‑2 at 500 DEG C, the short-circuit problem of the commercialized nano CeO2 cell is solved, and the power output and stability of the cell are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid oxide fuel cell technology, in particular to a fluorine-doped modified ceria-based solid electrolyte and a preparation method thereof. BACKGROUND

[0002] Solid oxide fuel cell (SOFC) is a device for directly converting chemical energy into electrical energy, which is not limited by the efficiency of Carnot cycle and can directly and efficiently convert hydrogen-containing fuels such as hydrogen and alkenes. Yttria-stabilized zirconia (YSZ) has been applied for more than 100 years as the most mature solid oxide fuel cell electrolyte. However, the high-temperature (700-1000℃) operating environment required by YSZ and the high cost problem caused thereby limit the commercialization and popularization.

[0003] Ceria-based electrolyte material is a common material in low-temperature (300-600℃) solid oxide fuel cell (LTSOFC), for example, samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) have shown excellent performance at low temperature (300-600℃).

[0004] In pure ceria (CeO2), cerium ions have two stable valence states of 3+ and 4+, and a certain amount of oxygen vacancies are formed in the CeO2 lattice through the mutual conversion between Ce 4+ and Ce 3+ ions, which has a certain ion conductivity. However, experiments have shown that the ionic conductivity of commercialized nano-CeO2 is very low, and the intrinsic electronic conductivity is too high, which leads to poor performance and stability of the commercialized nano-CeO2 cell, and short circuit occurs after a period of operation. Therefore, the existing pure commercialized nano-CeO2 cannot be directly applied to low-temperature solid oxide fuel cells. SUMMARY

[0005] The present application aims to solve the problem of short circuit and poor stability of ceria electrolyte in the fuel cell operation process in the background art, and proposes a fluorine-doped modified ceria-based solid electrolyte material, the chemical formula of which is as follows: CeO 2-y F y , wherein 0.1≤y≤0.6.

[0006] Preferably, y=0.4 in the formula.

[0007] Preferably, the ceria-based electrolyte material is doped with one or more than two of Sm, Gd, Ca, Y, La, Nd, and Pr in any combination. The single-doped ceria-based material includes Ce 0.8 Sm 0.2 O2-δ Ce 0.8 Gd 0.2 O 1.95 Ce 0.91 Y 0.09 O 1.95 Ce 0.9 Ca 0.1 O 1.9 Ce 0.8 Sm 0.17 La 0.03 O 1.9 Ce 0.8 Sm 0.1 Nd 0.1 O 1.9 Ce 0.8 Gd 0.17 Pr 0.03 O 1.9 Ce 0.85 Gd 0.1 Sm 0.05 O2, La 0.33 Ce 0.62 Pr 0.05 O 2-δ Sm 0.1 Ca 0.05 Gd 0.05 Ce 0.8 O 2-δ .

[0008] The application discloses a preparation method of a fluorine-doped modified cerium oxide-based solid electrolyte material.

[0009] S1, the CeF3 powder, the nano CeO2 powder and the powder are weighed according to the stoichiometric ratio and mixed, a certain amount of alcohol is added to the mixed powder, and grinding is performed until the alcohol is completely volatilized;

[0010] S2, the compound obtained in S1 is placed into a container and sintered at high temperature in a high-temperature furnace;

[0011] S3, the sintered material obtained in S2 is ground to obtain the fluorine-doped modified cerium oxide-based solid electrolyte powder.

[0012] Preferably, the amount of alcohol added in S1 is enough to cover the powder.

[0013] Preferably, the sintering temperature in S2 is 900 DEG C, and the sintering time is 4 hours.

[0014] Preferably, the container in S2 is a corundum crucible.

[0015] Compared with the prior art, the application has the following beneficial technical effects:

[0016] The material modification method of the application is simple in operation, low in material cost and material preparation cost.

[0017] The low-temperature solid oxide fuel cell prepared by the method of the application effectively improves the stability of the cell, reaches 158.7mA cm -2 The current density is 0.0047V / h, the voltage decay rate is improved, and the power output and stability of the cell are improved.

[0018] According to the method of the application, other cerium oxide-based electrolyte materials can be fluorine-doped and modified. The doping of F ions endows the CeO2-based material with the characteristics of an insulator, which can effectively reduce the intrinsic electronic conductivity of the material, thereby effectively improving the stability of the CeO2-based cell and avoiding the short circuit problem caused by excessively high intrinsic electronic conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is an electrochemical performance curve diagram of a fuel cell using commercialized nano CeO2 electrolyte material at 450-550 degrees Celsius;

[0020] Figure 2 is a stability curve diagram of a fuel cell using commercialized nano CeO2 electrolyte material at 500 degrees Celsius, 158.7mA cm -2 constant current;

[0021] Figure 3 is an electrochemical performance curve diagram of a fuel cell using CeO 1.6 F 0.4 as an electrolyte material at 450-550 degrees Celsius;

[0022] Figure 4 is a stability curve diagram of a fuel cell using CeO 1.6 F 0.4 as an electrolyte material at 500 degrees Celsius, 158.7mA cm -2 constant current;

[0023] Figure 5 is an SEM image of CeO2 powder;

[0024] Figure 6 is an SEM image of CeO 1.6 F 0.4 powder;

[0025] Figure 7Schematic diagram of a fluorine-doped ceria-based battery. DETAILED DESCRIPTION

[0026] Example 1

[0027] 1. Weigh 4.13g of nano-CeO2 and 0.79g of CeF3 powder, mix them, put them into a mortar, add ethanol until the powder is covered, and grind until the alcohol is completely evaporated;

[0028] 2. Place the ground compound into a corundum crucible, cover it and burn it in a high-temperature furnace at 900 degrees for 4 hours;

[0029] 3. After the powder cools down, take it out, put it into a mortar, and grind it without adding alcohol to obtain CeO 1.6 F 0.4 powder;

[0030] Weigh 0.3gCeO 1.6 F 0.4 The powder is used as the battery electrolyte and sandwiched between two Ni-NCAL electrode layers. The ceramic sheet battery is made by using a tablet press with a pressure of 8-10 MPa. Figure 7 The battery shown;

[0031] The battery was mounted on a test fixture and placed in a test furnace at 550 degrees Celsius with hydrogen flowing through it. The battery was open-circuited for 1 hour before performance testing was performed.

[0032] In this embodiment, the instructions are attached. Figure 1 To use NCAL (LiNi 0.8 Co 0.15 Al 0.05 The graph of fuel cells with CdO2 as cathode and anode materials and commercial nano CeO2 as electrolyte material at 450-550 degrees Celsius; Figure 2 The fuel cell using NCAL as cathode and anode materials and commercial nano CeO2 as electrolyte material has a power output of 158.7 mA cm at 500 degrees Celsius. -2 Stability curve under constant current. Figures 1-2 It can be seen that the voltage decays from 0.670V to 0.621V within 1.75h, and the decay rate is -0.027V / h.

[0033] and Figure 3 To use NCAL as cathode material and anode material, CeO 1.6 F 0.4 Electrochemical performance curve of fuel cell as electrolyte material at 450-550 degrees Celsius; Figure 4 NCAL is used as cathode material and anode material, CeO 1.6 F 0.4As the electrolyte material of fuel cell, the current is 158.7mA cm at 500 degrees Celsius. -2 Stability curve under constant current; Figures 3-4 and Figures 1-2 By comparison, we can see that the use of CeO 1.6 F 0.4 The fuel cell, using nano-CeO2 as an electrolyte material, can operate stably for more than seven hours, with the operating voltage dropping from 0.862V to 0.830V, maintaining a high level of output power and steadily decreasing at a decay rate of -0.0047V / h. Two IVP performance tests were conducted five hours into the stability experiment, with no impact on stability. After the experiments, the operating voltage continued to change at the same decay rate. This solves the short-circuit problem of commercial nano-CeO2 batteries while also improving their power output and stability.

[0034] Example 2

[0035] According to the method of Example 1, the ratio of commercial nano CeO2 and CeF3 powder was adjusted. The following table lists the preparation of CeO 2-y F y (0.1≤y≤0.6) The amount of CeO2 and CeF3 powder required for solid electrolyte material.

[0036] Table 1 Preparation of CeO 2-y F y (0.1≤y≤0.6) Required material quantity

[0037] Doping amount (mol) CeF3(g) CeO2(g) CeO 1.9 F 0.1 ]]> 0.1 0.2 4.9 CeO 1.8 F 0.2 ]]> 0.2 0.4 4.65 CeO 1.7 F 0.3 ]]> 0.3 0.59 4.39 CeO 1.6 F 0.4 ]]> 0.4 0.79 4.13 CeO 1.4 F 0.6 ]]> 0.6 1.03 3.614

[0038] For different cerium oxide-based electrolyte materials, the optimal fluorine doping modification ratio is not the same. The present invention is not limited to the above embodiments. The fluorine-doped modified cerium oxide-based solid electrolyte materials obtained by this method and idea all fall within the protection scope of the present invention.

Claims

1. A fluorine-doped modified cerium oxide-based solid electrolyte material, characterized in that: The chemical formula of the electrolyte material is as follows: CeO 2-y F y , where 0.1≤y≤0.6, where y=0.4; the cerium oxide-based electrolyte material is doped with one or any combination of two or more of the elements Sm, Gd, Ca, Y, La, Nd, and Pr; The preparation method of the electrolyte material is as follows: S1. Weigh CeF3 powder and nano-CeO2 powder according to the stoichiometric ratio and mix them, add a certain amount of ethanol to the mixed powder, and grind until the ethanol is completely evaporated; S2, placing the composite obtained in S1 into a container and sintering it at high temperature in a high temperature furnace; S3. Grinding the sintered material obtained in S2 to obtain the fluorine-doped modified cerium oxide-based solid electrolyte powder.

2. The fluorine-doped modified cerium oxide-based solid electrolyte material according to claim 1, characterized in that: Add enough alcohol to S1 to cover the powder.

3. The fluorine-doped modified cerium oxide-based solid electrolyte material according to claim 1, characterized in that: The particle size of CeO2 used in S1 is 20 nm.

4. The fluorine-doped modified cerium oxide-based solid electrolyte material according to claim 1, characterized in that: In S2, the sintering temperature is 900 degrees Celsius and the sintering time is 4 hours.

5. The fluorine-doped modified cerium oxide-based solid electrolyte material according to claim 1, characterized in that: The container in S2 is a corundum crucible.

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