CN108550874A - A kind of cerium oxide-barium cerate base solid-oxide fuel battery electrolyte and preparation method - Google Patents

Abstract

The present invention relates to a kind of cerium oxide barium cerate base solid-oxide fuel battery electrolyte and preparation method, the main component of electrolyte is Ce_0.8Bi _x Re_(0.2‑x)O_2‑δ‑BaCe_0.8Bi _x Re_(0.2‑x)O_3‑δ(0≤x≤0.2), wherein Re are one kind in La, Nd, Eu, Gd, Dy, Er, Yb.Using solid reaction process single sintering Ce_0.8Bi _x Re_(0.2‑x)O_2‑δ‑BaCe_0.8Bi _x Re_(0.2‑x)O_3‑δComposite granule prepares composite electrolyte by granulation, compression moulding, high-temperature calcination.The electrolyte has the advantages that firing temperature is low and ionic conductivity is high, which has the advantages that be simple and efficient and be convenient for industrialization.

Description

A cerium oxide-barium cerate-based solid oxide fuel cell electrolyte and its preparation method

technical field

The invention relates to the field of electrolytes for solid oxide fuel cells, in particular to a cerium oxide-barium cerate-based solid oxide fuel cell electrolyte and a preparation method.

Background technique

Solid oxide fuel cells (SOFCs) have become a research hotspot in the field of fuel cells due to their high energy conversion efficiency, no pollution, and fuel diversity. Electrolyte is the key and core material of SOFCs. At present, YSZ (yttrium oxide doped zirconia) is the most mature electrolyte material for SOFCs. However, YSZ usually has a high ionic conductivity above 1000 ° C. Too high operating temperature has brought a series of problems to SOFCs, such as: reduced electrode activity, high requirements for connector materials, and poor battery sealing. Therefore, reducing the operating temperature of SOFCs is an important development direction to expand the selection of battery component materials and improve the long-term operation stability of batteries. However, as the operating temperature decreases, the conductivity of the YSZ electrolyte decreases rapidly, leading to a sharp decrease in battery performance. The development of new intermediate temperature solid oxide fuel cell electrolytes is the current key research direction.

Chinese patent document _CN101000966 discloses "a composite doped _cerium oxide electrolyte and its preparation _method " _. The composite oxide of gadolinium oxide and yttrium oxide has an electrical conductivity of 0.038 S·cm ^-1 at 600°C in air. Chinese patent document CN102544559A discloses "a cerium oxide-based electrolyte for solid oxide fuel cells and its preparation method". The firing temperature is reduced by adding lanthanum oxide and vanadium oxide to cerium oxide. The conductivity under the condition is 0.0178S·cm ^-1 . However, Ce ⁴⁺ in ceria-based electrolytes is easily partially reduced to Ce ³⁺ under low oxygen partial pressure or reducing atmosphere, resulting in electronic conductance, resulting in a decrease in the open-circuit voltage of SOFCs, which in turn leads to a decrease in battery performance.

Chinese patent document CN103086716A discloses "composite proton conductor material based on rare earth oxide doped barium cerate and its preparation method". The electrolyte is barium cerate doped with gadolinium oxide or yttrium oxide. The rate is higher than 10 ^-2 S·cm ^-1 . However, the barium cerate electrolyte is unstable in the presence of CO ₂ and H ₂ O, and is prone to chemical reactions to form barium carbonate, barium hydroxide, etc., resulting in a decrease in conductivity.

Wenping Sun et al. (A novel electronic current-blocked stable mixed ionicconductor for solid oxide fuel cells, Journal of Power Sources, 2011, 196(1):62-68) introduced a rare earth element doped CeO ₂ /BaCeO ₃ composite electrolyte , realizing the complementary performance advantages of the cerium oxide-based electrolyte and the barium cerate-based electrolyte, and solving the problems that the cerium oxide-based electrolyte is easily partially reduced and the barium cerate-based electrolyte is chemically unstable. However, the firing temperature of the composite electrolyte is high (>1350°C), and interfacial reaction or element diffusion is prone to occur between the two electrolytes, resulting in low conductivity.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention proposes a Bi-doped Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ (0≤ x≤0.2, Re=La, Nd, Eu, Gd, Dy, Er, Yb, etc.) composite electrolyte and its preparation method. The prepared electrolyte has the advantages of low firing temperature and high electrical conductivity. The proposed preparation method has the advantages of simple process and convenient industrialization.

The present invention is realized through the following technical solutions, including the following steps.

1. The preparation method of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _{0.8 Bi x} Re _{(0.2- x )} O _3-δ composite powder is as follows.

1.1 Weigh BaCO ₃ , CeO 2 , Bi 2 O 3 , Re ₂ O according to the stoichiometric ratio of Ce _0.8 Bi _x Re _{( 0.2- x} ) O _{2 -δ} -BaCe _0.8 Bi _x Re ₍ 0.2- _x ) O _3- δ ₃ (Re=La, Nd, Eu, Gd, Dy, Er, Yb, etc.), put it into a polyurethane ball mill tank, add absolute ethanol, and use zirconia balls as the medium for ball milling for 8 to 12 hours. Raw materials, zirconia balls, The mass ratio of absolute ethanol is 1: (2.5-3.5): (0.8-0.9), and the slurry is obtained.

1.2 Drying, granulation, and compression molding under a pressure of 5-15 MPa to obtain a green body.

1.3 Put the green body into the heating furnace, raise the temperature to 900-1050°C, keep it warm for 10-15 hours, and then cool it with the furnace.

1.4 Break the calcined block to obtain Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite powder.

2. The preparation method of Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite electrolyte is as follows.

2.1 Add 1 wt.% binder to the Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite powder, mix well, and granulate , Pressed under a pressure of 30-60 MPa to form a sheet-shaped electrolyte green body with a thickness of 0.3-1.5 mm.

2.2 Put the electrolyte green body into the heating furnace, raise the temperature to 1100-1250°C, and keep it warm for 2-6 hours to obtain the solid oxide fuel cell electrolyte.

The purity of the raw materials described in the present invention is greater than 99.9%; the described absolute ethanol is of analytical grade.

The mass ratio of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ to BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ in step 1.1 of the present invention is (95～50): (5～ 50).

Preferably according to the present invention, in step 1.1, in Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ , 0.05≤x≤0.12.

In step 1.2 of the present invention, the drying temperature is 80-100° C., and the drying time is 12-15 hours. The sieve mesh of the granulated powder is 40 mesh.

Preferably according to the present invention, the heating regime in step 1.3 is: heating at 3-6°C/min to 950-1000°C, and keeping the temperature for 11-13 hours.

The binder described in step 2.1 of the present invention is one of 5wt.% PVA (polyvinyl alcohol) aqueous solution or PVB (polyvinyl butyral) ethanol solution.

Preferably according to the present invention, the sieve mesh number of the crushed powder in step 2.1 is 40 mesh.

Preferably according to the present invention, the thickness of the sheet-shaped electrolyte sheet in step 2.1 is 0.6-1.2 mm.

Preferably according to the present invention, the heating regime in step 1.3 is: heating up to 1150-1200°C at 2-4°C/min, and keeping the temperature for 3-5 hours.

Beneficial effect

1. Low firing temperature: Bi ₂ O ₃ has a low melting point, and Bi doping reduces the firing temperature of the CeO ₂ /BaCeO ₃ composite electrolyte by more than 100°C.

2. High oxygen ion conductivity: Compared with single-element doped CeO ₂ /BaCeO ₃ composite electrolyte without Bi doping, the ion conductivity is more than 3 times higher.

3. Composite-doped CeO ₂ /BaCeO ₃ powder can be prepared through one-step reaction without subsequent mixing process, the process flow is simple, and it is convenient for industrialization.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the examples, but the protection scope of the present invention is not limited thereto.

Example 1

Weigh BaCO ₃ , CeO 2 , Bi 2 O 3 _, La ₂ O ₃ according to 90wt.% Ce _0.8 Bi _0.1 La _0.1 O _2-δ -10 wt _. % BaCe _0.8 Bi _0.1 La _0.1 O ₃ - _δ stoichiometric ratio, Put it into a polyurethane ball mill jar, add absolute ethanol, and use zirconia balls as the medium for ball milling for 10 hours. The mass ratio of raw materials, zirconia balls, and absolute ethanol is 1: 3: 0.8 to obtain a slurry. Dry at 90° C. for 12 hours, pass through a 40-mesh sieve to granulate, and press under a pressure of 10 MPa to obtain a green body. Put the green body into the heating furnace, raise the temperature to 1000°C at 3°C/min, keep it warm for 12 hours, and then cool down with the furnace. The calcined block was crushed to obtain 90wt.% Ce _0.8 Bi _0.1 La _0.1 O _2-δ -10 wt.% BaCe _0.8 Bi _0.1 La _0.1 O _3-δ composite powder. Add 1 wt.% PVA aqueous solution to the composite powder, mix well, pass through a 40-mesh sieve to granulate, and press under a pressure of 50 MPa to form a sheet-shaped electrolyte body with a thickness of 1.0 mm. Put the electrolyte body into a heating furnace, raise the temperature to 1150°C at 3°C/min, and keep it warm for 4 hours to obtain a solid oxide fuel cell electrolyte.

Using electrochemical workstation (Shanghai Chenhua, CHI660E) test, 90wt.% Ce _0.8 Bi _0.1 La _0.1 O _2-δ -10 wt.% BaCe _0.8 Bi _0.1 La _0.1 O _3-δ composite electrolyte under 600 ℃ air condition The ionic conductivity is 0.031 S cm ^-1 .

Example 2

Weigh BaCO ₃ , CeO 2 _, Bi 2 O ₃ , Gd ₂ O ₃ according to 70wt.% Ce _0.8 Bi _0.1 Gd _0.1 O _2-δ -30 _wt .% BaCe _0.8 Bi _0.1 Gd _0.1 O _3-δ stoichiometric ratio, Put it into a polyurethane ball mill jar, add absolute ethanol, and use zirconia balls as the medium for ball milling for 10 hours. The mass ratio of raw materials, zirconia balls, and absolute ethanol is 1: 3.1: 0.9 to obtain a slurry. Dry at 80°C for 15 hours, pass through a 40-mesh sieve to granulate, and press to form under a pressure of 8 MPa to obtain a green body. Put the green body into the heating furnace, raise the temperature to 980°C at 5°C/min, keep it warm for 13 hours, and then cool down with the furnace. The calcined block was crushed to obtain 70wt.% Ce _0.8 Bi _0.1 Gd _0.1 O _2-δ -30 wt.% BaCe _0.8 Bi _0.1 Gd _0.1 O _3-δ composite powder. Add 1 wt.% PVB ethanol solution to the composite powder, mix well, pass through a 40-mesh sieve to granulate, and press under a pressure of 40MPa to form a sheet-shaped electrolyte body with a thickness of 0.9 mm. Put the electrolyte body into a heating furnace, raise the temperature to 1200°C at 4°C/min, and keep it warm for 5 hours to obtain a solid oxide fuel cell electrolyte.

Using an electrochemical workstation (Shanghai Chenhua, CHI660E) test, 70wt.% Ce _0.8 Bi _0.1 Gd _0.1 O _2-δ -30 wt.% BaCe _0.8 Bi _0.1 Gd _0.1 O _3-δ composite electrolyte at 600 ℃, air conditions The ionic conductivity is 0.028 S cm ^-1 .

Comparative example 1

As described in Example 1, the difference is: no Bi element is doped. That is: the composition of the composite electrolyte is 90wt.%Ce _0.8 La _0.2 O _2-δ -10 wt.% BaCe _0.8 La _0.2 O _3-δ . The firing temperature of this electrolyte is 1300°C. The ion conductivity at 600°C under air conditions is 0.0078 S cm ^-1 .

Comparative example 2

As described in Example 1, the difference is: no Bi element is doped. That is: the composition of the composite electrolyte is 70wt.%Ce _0.8 Gd _0.2 O _2-δ -30 wt.% BaCe _0.8 Gd _0.2 O _3-δ . The firing temperature of this electrolyte is 1350°C. The ionic conductivity at 600°C under air conditions is 0.0071 S cm ^-1 .

Compared with Comparative Example 1-2, the firing temperature of Example 1-2 of the present invention is significantly lowered, and the electrical conductivity is increased by more than 3 times. It shows that Bi element doping is beneficial to reduce the firing temperature of CeO ₂ /BaCeO ₃ composite electrolyte and improve its ionic conductivity.

It should be noted that the above examples are only a few specific embodiments of the present invention, and obviously the present invention is not limited to the above embodiments, and other modifications are also possible. All deformations directly derived or indirectly derived from the disclosure content of the present invention by those skilled in the art should be considered as the protection scope of the present invention.

Claims (5)

1. A CeO ₂ /BaCeO ₃ based solid oxide fuel cell electrolyte, characterized in that the main component is Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ - BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ (0≤x≤0.2), wherein Re is one of La, Nd, Eu, Gd, Dy, Er, Yb. 2. the preparation method of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ electrolyte according to claim 1, is characterized in that, comprises the following steps : (1) Preparation of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ composite powder: Weigh BaCO _{3 , CeO 2 ,} Bi 2 O 3 , Re ₂ O ₃ according to the stoichiometric ratio of Ce _0.8 Bi _x Re ( _{0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re ₍ 0.2- x ) O _{3 -δ} (Re=La, Nd, Eu, Gd, Dy, Er, Yb, etc.), put it into a polyurethane ball mill tank, add absolute ethanol, and use zirconia balls as the medium for ball milling for 8 to 12 hours. Raw materials, zirconia balls, The mass ratio of water to ethanol is 1: (2.5～3.5): (0.8～0.9), to obtain the slurry; Drying, granulation, and compression molding under a pressure of 5-15 MPa to obtain a green body; Put the green body into the heating furnace, raise the temperature to 900-1050°C, keep it warm for 10-15 hours, and then cool with the furnace; breaking the calcined block to obtain Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite powder; (2) Preparation of Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite electrolyte: Add 1 wt.% binder to Ce _0.8 Bi _x Re _(0.2-x) O _2-δ -Ba Ce _0.8 Bi _x Re _(0.2-x) O _3-δ composite powder, mix well, granulate, Press under the pressure of 30-60MPa to form a sheet-shaped electrolyte green body with a thickness of 0.3-1.5 mm; Put the electrolyte body into a heating furnace, raise the temperature to 1100-1250° C., and keep it warm for 2-6 hours to obtain the solid oxide fuel cell electrolyte. 3. Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ electrolyte according to claim 1, characterized in that Ce _0.8 Bi _x Re ₍ The mass ratio of _{0.2- x )} O _2-δ to BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ is (95～50):(5～50). 4. the preparation method of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ electrolyte according to claim 2, is characterized in that, described The drying temperature is 80-100°C, and the drying time is 12-15 hours; the sieve mesh of the granulated powder is 40 mesh. 5. the preparation method of Ce _0.8 Bi _x Re _{(0.2- x )} O _2-δ -BaCe _0.8 Bi _x Re _{(0.2- x )} O _3-δ electrolyte according to claim 2, is characterized in that, described The binder is one of 5wt.% PVA (polyvinyl alcohol) aqueous solution or PVB (polyvinyl butyral) ethanol solution.