A Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte and fuel cell

Abstract

This invention discloses a Ga-Mn dual-doped pyrochlore-type La₂Zr₂O₇ low-temperature ceramic electrolyte and a fuel cell. The low-temperature ceramic electrolyte has a single-phase pyrochlore structure and the chemical formula La. 2‑ x Ga x Zr 2‑x Mn x O 7‑δ Where 0.2≤x≤0.6; Ga is Ga 3+ The form replaces part of the La bit, Mn with Mn 2+ / Mn 3+ / Mn 4+ By substituting some Zr sites, co-doping induces oxygen vacancy enrichment and modulates local charge distribution, thereby promoting oxide ion transport. The optimized composition of this invention, La... 1.6 Ga 0.4 Zr 1.6 Mn 0.4 O 7‑δ The ionic conductivity reaches 0.28 S·cm at 550 °C. ‑1 The activation energy was reduced to 0.678 eV; a single cell constructed using this electrolyte achieved 1171 mW·cm⁻¹ at 550 °C. ‑2 The peak power density is reduced to 0.37 Ω; the present invention realizes rapid oxide ion transport of La2Zr2O7-based electrolyte under medium and low temperature conditions, which can be used in high-performance solid oxide fuel cells.

Description

Technical Field

[0001] This invention relates to a low-temperature ceramic electrolyte, particularly to a Ga-Mn double-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte, and also to a low-temperature ceramic fuel cell composed using the above-mentioned low-temperature ceramic electrolyte. Background Technology

[0002] Stability-oriented zirconate compounds, especially La₂Zr₂O₇, are considered potential candidate materials for electrolytes in low-to-medium temperature solid oxide fuel cells due to their excellent chemical and thermal stability and the inherent defect-accommodating capacity of the pyrochlore structure. However, unmodified La₂Zr₂O₇ typically exhibits low oxygen ion conductivity in the low-to-medium temperature range, making it difficult to balance low ohmic losses with high power output. Therefore, researchers have undertaken various improvement efforts for this material. Existing improvement methods mainly include: firstly, introducing heterovalent dopants such as Ca, Sr, Mg, Y, Sc, and Ga at the La or Zr sites to increase the oxygen vacancy concentration through charge compensation, thereby improving oxygen ion transport capacity; secondly, improving the oxygen vacancy formation and migration environment by controlling the pyrochlore / defect fluorite phase structure, increasing the anion sublattice disorder, or constructing a mixed-phase structure; and thirdly, shortening the transport path and attempting to reduce grain boundary impedance through microstructure control techniques such as sol-gel, nanofiberization, and particle refinement. Existing literature shows that the above methods can improve the ion transport properties of La2Zr2O7 to some extent. For example, acceptor doping can induce the formation of oxygen vacancies, while pyrochlore / defect fluorite phase modulation and nanofiberization can also improve the conductivity of the material.

[0003] However, existing technologies still have significant shortcomings. First, while single-valent doping can increase the number of oxygen vacancies, there is often a strong association between the dopant ion and the oxygen vacancy. Especially when the dopant enters the Zr site, the oxygen vacancy is more easily bound by electrostatic and elastic forces, thus forming defect aggregates or local clusters. This results in "increased vacancy concentration but decreased vacancy mobility," and the activation energy remains high. Second, some alkaline earth metal doped systems also suffer from limited solid solubility. When the doping amount increases, a second phase is easily precipitated, weakening the phase purity and stability of the electrolyte. For example, in previous studies, the solid solubility of Sr in La2Zr2O7 is limited, and after exceeding a certain content, a second phase such as SrZrO3 will appear. Furthermore, while pyrochlore / defect fluorite miscibility and nanostructure modulation can improve conductivity, they are typically sensitive to preparation conditions, often depending on specific calcination temperatures, phase ratios, or microstructures. Simultaneously, these methods primarily improve transport at the phase interface or microstructure level, offering limited optimization of bulk defect chemistry and making it difficult to simultaneously achieve a balance between high oxygen vacancy concentration, low vacancy trapping, and high mobility. Therefore, existing La2Zr2O7 modification techniques still haven't solved a crucial problem: how to simultaneously promote oxygen vacancy generation, weaken the binding effect of dopants on oxygen vacancies, and lower the oxygen ion migration barrier below 600℃ while maintaining the intrinsic chemical and structural stability of La2Zr2O7, thereby obtaining a truly high-performance ceramic electrolyte suitable for medium- and low-temperature solid oxide fuel cells. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a Ga-Mn double-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte that enriches oxygen vacancy defects, enhances charge redistribution, improves conductivity, and reduces activation energy, as well as a low-temperature ceramic fuel cell technology composed thereof.

[0005] Technical solution: This invention provides a Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte, wherein the general chemical formula of the low-temperature ceramic electrolyte is La. 2-x Ga x Zr 2-x MnxO 7-δ Where 0.2≤x≤0.6, δ is the oxygen nonstoichiometric defect caused by oxygen vacancies, 0<δ<1; preferably, x is 0.2, 0.4 or 0.6; the low-temperature ceramic electrolyte has a single-phase pyrochlore structure, Ga is used as Ga 3+ The form replaces part of the La bit, Mn with Mn 2+ / Mn 3+ / Mn 4+ The form replaces some Zr sites, the material contains oxygen vacancy defects, and second-phase separation basically does not occur.

[0006] The above-mentioned Ga-Mn double-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte was prepared by a citrate-assisted sol-gel method, including the following steps:

[0007] (1) Press La 2-x Ga x Zr 2-x Mn x O 7-δ According to the stoichiometric ratio, lanthanum nitrate hexahydrate La(NO3)3·6H2O, zirconium nitrate hydrate Zr(NO3)4·4H2O, gallium nitrate hydrate Ga(NO3)3·nH2O, and manganese nitrate hydrate Mn(NO3)2·mH2O were weighed, dissolved in deionized water, and stirred to form a transparent precursor solution; where n and m represent the number of water of crystallization in the gallium nitrate hydrate and manganese nitrate hydrate used, respectively, depending on the actual hydration state of the raw materials used;

[0008] (2) Add chelating agent citric acid to the precursor solution and heat to 80-85°C under continuous stirring until a uniform gel is formed; dry the gel at 150-160°C to obtain a dry gel, grind it and then calcine it in air at 1000-1100°C for 4-5 hours with a heating rate of 3-5°C / min to obtain Ga-Mn double-doped pyrochlore type La2Zr2O7 low-temperature ceramic electrolyte.

[0009] The molar ratio of La, Zr, Ga, and Mn, calculated as metal cations, is (2-x):(2-x):x:x, where 0.2 ≤ x ≤ 0.6; the molar ratio of citric acid to total metal cations is 1.8:1 to 2.2:1, more preferably 2:1.

[0010] The fuel cell using the above-mentioned Ga-Mn double-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte has a symmetrical sandwich structure consisting of an anode, an electrolyte, and a cathode arranged sequentially. The cathode and anode are both NCAL electrodes of the same specification, and the electrolyte layer is the Ga-Mn double-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte.

[0011] The NCAL electrode is prepared by mixing and grinding NCAL and polyvinylidene fluoride binder in terpineol to obtain a uniform slurry; uniformly coating the slurry onto the surface of nickel foam, then drying to remove the solvent, thus forming an NCAL coating, thereby obtaining the NCAL electrode. Preferably, the mass ratio of NCAL to polyvinylidene fluoride binder is 93:7 to 97:3, more preferably 95:5, and the effective area of ​​the slurry coated on the nickel foam is 0.64 cm². 2 The resulting NCAL coating has a thickness of 8–12 μm.

[0012] The above-mentioned fuel cell is prepared by laminating an electrolyte layer between two identical NCAL electrodes, then placing the three-layer structure in a mold and cold-pressing it at 180-220 MPa for 8-12 minutes to enhance interfacial contact, finally obtaining a compact sandwich structure single cell with an overall thickness of 600-700 μm.

[0013] Invention Principle: The present invention relates to a Ga-Mn co-doped pyrochlore-type La₂Zr₂O₇ electrolyte, which combines vacancy generation with redox-assisted charge regulation. Gallium, as a vacancy-forming dopant, activates the non-stoichiometric ratio of oxygen and induces local lattice distortion, thereby promoting vacancy transitions; while multivalent manganese (Mn) 2＋ / Mn 3＋ / Mn 4＋ As a charge-compensating buffer, it reshapes local bonds and alleviates the strong vacancy trapping effect. Specifically, after Ga-Mn doping, the relevant characteristic lattice modes (such as Eg, F2g, and Alg) are still identifiable, but peak broadening and enhancement of defect-related features (including bands attributed to Ga-O / Mn-O vibrations and "oxygen vacancy-related" signals) gradually become significant. This evolution indicates that local distortion is intensified and oxygen vacancy activation is enhanced, but the parent lattice does not collapse, thus enhancing ion transport while maintaining phase stability.

[0014] In Ga-Mn dual-doped pyrochlore-type La2Zr2O7 materials, Ga is used as Ga... 3＋ Mn is incorporated into the oxide lattice in the form of Mn 2＋ / Mn 3＋ / Mn 4＋The coexistence of species: Manganese can act as an internal redox buffer under fuel cell operating conditions, regulating local charge fluctuations and stabilizing non-stoichiometric oxygen configuration. In Ga-Mn co-doped pyrochlore-type La2Zr2O7, the oxygen vacancy content increased from 36.6% in La2Zr2O7 to 53.2% in LZGM-04, reflecting the redistribution of oxygen species induced by co-doping. XPS and EPR results jointly confirmed the change in defect structure in LZGM-04, characterized by a large number of electronically active oxygen vacancies. After Ga-Mn doping, the Fermi level position and surface potential of the material changed significantly, with the undoped La2Zr2O7 exhibiting a wide optical bandgap (Eg≈3.30 eV), consistent with the electron blocking characteristics of the zirconate framework. In contrast, LZGM-04 exhibits significantly enhanced visible light absorption and a narrowed bandgap (Eg≈2.02 eV), indicating that the electronic states derived from dopants / defects are accompanied by lattice distortion and a vacancy-rich local environment. The work function increases from 4.66 eV (La2Zr2O7) to 6.26 eV (LZGM-04), proving that the Fermi level position and surface potential are significantly altered after Ga-Mn doping. For ceramic fuel cells, the huge chemical potential mismatch is expected to induce interfacial band bending and a space charge layer at the grain / electrode contact, thereby generating an internal electrostatic field. This field can both assist ion drift and construct an energy barrier that hinders the penetration of planar electrons.

[0015] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: The Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte of the present invention enriches oxygen vacancy defects after Ga-Mn co-doping, thereby improving conductivity and reducing activation energy, achieving 0.28 S cm⁻¹ at 550℃. -1 With high conductivity and a peak power density of 1171 mW / cm², the conductivity is high. -2 It is applied to low-temperature ceramic fuel cells. Its transport mechanism is that Ga-Mn co-doping reduces the migration barrier through local electronic polarization, while stabilizing a higher concentration of mobile oxygen vacancies, thereby enhancing oxide ion conduction under the working conditions of solid oxide fuel cells and realizing the operation of high-performance solid oxide fuel cells. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the preparation of the low-temperature ceramic electrolyte of the present invention;

[0017] Figure 2 XRD and Raman analyses of the low-temperature ceramic electrolyte of this invention are shown, including (a) XRD patterns of La2Zr2O7 and LZGM-x (x=02, 04, 06), and (b) XRD patterns of La2Zr2O7 and LZGM-x in the range of 100-1000 cm⁻¹. -1 Raman spectra in the wavenumber range;

[0018] Figure 3 The scanning electron microscope-energy dispersive spectroscopy analysis of the low-temperature ceramic electrolyte of the present invention includes the elemental distribution diagrams of lanthanum (a), zirconium (b), oxygen (c), manganese (d) and gallium (e), the corresponding superimposed distribution diagram of all elements (f), and the energy dispersive spectroscopy diagram showing the characteristic peaks of lanthanum, zirconium, oxygen, manganese and gallium (g).

[0019] Figure 4 The microstructure characterization of the electrolyte materials La2Zr2O7 and LZGM-04 of this invention includes: (a–c) high-resolution transmission electron microscopy images of La2Zr2O7 at different magnifications; (d–f) HRTEM images of LZGM-04 at corresponding length scales; (g) lattice interference fringe images and interlayer spacing analysis of La2Zr2O7 (d ≈ 0.319 nm); (h) lattice interference pattern and interlayer spacing analysis of LZGM-04 (d ≈ 0.325 nm); three-dimensional surface morphology images of La2Zr2O7 and LZGM-04 obtained by atomic force microscopy.

[0020] Figure 5 This invention relates to the electrochemical performance and transport characteristics of the low-temperature ceramic electrolytes La2Zr2O7 and LZGM-04 electrolytes. (a, b) show the IV and IP curves of single cells using La2Zr2O7(a) and LZGM-04(b) electrolytes measured at 430–550 °C. (c, d) show the Nyquist plots and corresponding equivalent circuit fittings of La2Zr2O7(c) and LZGM-04(d) at 430–550 °C. (e) shows the ionic conductivity as a function of temperature (1000 / T). (f) shows the Arrhenius plot of ln(σT) versus 1000 / T and the extracted activation energy. (g) compares the maximum power density of La2Zr2O7 and LZGM-04 at different operating temperatures. (h) compares the total polarization resistance (R-total) measured by electrochemical impedance spectroscopy as a function of temperature. (i) 550 °C Comparison of peak power densities of La2Zr2O7 and La2Zr2O7 electrolytes with different Ga-Mn doping ratios at °C;

[0021] Figure 6The band structure of La₂Zr₂O₇ and LZGM-04 is measured based on UV-Vis spectroscopy and UV photoelectron spectroscopy. (a, b) show the UV-Vis absorption spectra of LZGM-04 and La₂Zr₂O₇, respectively; the inset shows the Tauc plots used to estimate the optical band gap (LZGM-04 band gap Eg = 2.02 eV, La₂Zr₂O₇ band gap Eg = 3.30 eV); (c, d) show the UPS spectra of LZGM-04 and La₂Zr₂O₇ (He I, hν = 21.22 eV), highlighting the secondary electron cutoff region (SEC) and the Fermi edge region, respectively; the work function (φ) is calculated based on the cutoff position: φ = 4.66 eV for LZGM-04 and φ = 6.26 eV for La₂Zr₂O₇.

[0022] Figure 7 This invention relates to the surface chemical states and oxygen vacancy characteristics of the low-temperature ceramic electrolytes La2Zr2O7 and LZGM-04, including high-resolution XPS La 3d spectra of La2Zr2O7 and LZGM-04; high-resolution XPS Zr 3d spectra of La2Zr2O7 and LZGM-04; high-resolution XPS Ga 2p spectrum of LZGM-04; high-resolution XPS Mn 2p spectrum of LZGM-04; high-resolution XPS O 1s spectrum of La2Zr2O7 and LZGM-04, decomposed into lattice oxygen (OL) and oxygen vacancy-related oxygen (OV) components; comparison of oxygen vacancy content obtained by O 1s XPS fitting of La2Zr2O7 and LZGM-04; XPS spectra of La2Zr2O7 and LZGM-04; and EPR spectra of La2Zr2O7 and LZGM-04, showing characteristic signals related to oxygen vacancies (g ≈ 0.5%). 2.003);

[0023] Figure 8 For density functional theory defect energy and charge redistribution, and the proposed working mechanism of LZGM electrolyte in low-temperature solid oxygen fuel cells, (a) the optimized La2Zr2O7 supercell, highlighting oxygen vacancies (V O (a) Sites used to assess oxygen vacancy formation energy; (b) Optimized LZGM-04 superunit (V O (c) LZGM-04 charge density difference plot (Δρ=ρ) is used to evaluate the oxygen vacancy formation energy after Ga-Mn co-doping. LZGM-04 -ρ atoms (d) A schematic diagram of the mechanism of Ni-NCAL|LZGM|Ni-NCAL fuel cell, focusing on the transport process of defect-assisted ions through the co-doped La–Zr–O framework structure under H2 / O2 operating conditions. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments.

[0025] Example 1

[0026] The Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte (LZGM-04) of the present invention is prepared by a citrate-assisted sol-gel method. The nitrate precursor is dissolved and stirred at 80°C, gelled and dried at 150°C, ground to prepare precursor powder, calcined at 1100°C to form crystalline oxide, and then further ground and cold-pressed to prepare a dense electrolyte preform. The process includes the following steps:

[0027] (1) Lanthanum nitrate hexahydrate (La(NO3)3·6H2O), zirconium nitrate hydrate (Zr(NO3)4·4H2O), gallium nitrate hydrate (Ga(NO3)3·9H2O), and manganese nitrate hydrate (Mn(NO3)2·6H2O) were used as metal sources, and citric acid was used as a chelating agent. The designed components are as follows: La 1.6 Ga 0.4 Zr 1.6 Mn 0.4 O 7-δ Where δ represents the non-stoichiometric oxygen deficit caused by oxygen vacancies. Equimolar amounts of the corresponding nitrate are dissolved in deionized water and stirred for 2 hours to form a transparent precursor solution.

[0028] (2) Citric acid was then added at a molar ratio of 2:1 to total metal cations. The mixed solution was heated to 80-85°C under continuous stirring until a uniform gel was formed. The gel was dried at 150°C to obtain a dry gel. After grinding, it was calcined in air at 1100°C for 4 hours (heating rate: 5°C / min) to finally obtain Ga-Mn double-doped pyrochlore type La2Zr2O7 low-temperature ceramic electrolyte powder material, denoted as LZGM-04.

[0029] The described structure is a pyrochlore structure, with Ga and Mn successfully incorporated into the lattice without phase separation. The diffraction patterns perfectly match the La2Zr2O7 (PDF#73-0444) standard card. Figure 2 As shown.

[0030] Example 2

[0031] The preparation method in this embodiment is the same as that in Example 1, except that the molar ratio of metal cations in step (1) is adjusted to La:Zr:Ga:Mn = 1.8:1.8:0.2:0.2, to obtain La 1.8 Ga 0.2 Zr 1.8 Mn0.2 O 7-δ This is designated LZGM-02. After assembling the fuel cell in the same manner as in Example 4, the peak power densities at 550, 520, 490, 460, and 430 °C were 972, 669, 512, 423, and 224 mW·cm⁻¹, respectively. -2 The total resistance at 550 ℃ is 0.431 Ω, and the ionic conductivity is 0.238 S·cm. -1 .

[0032] Example 3

[0033] The preparation method in this embodiment is the same as that in Example 1, except that the molar ratio of metal cations in step (1) is adjusted to La:Zr:Ga:Mn = 1.4:1.4:0.6:0.6, to obtain La 1.4 Ga 0.6 Zr 1.4 Mn 0.6 O 7-δ This is designated LZGM-06. After assembling the fuel cell in the same manner as in Example 4, the peak power densities at 550, 520, 490, 460, and 430 °C were 866, 658, 472, 363, and 196 mW·cm⁻¹, respectively. -2 The total resistance at 550 ℃ is 0.445 Ω, and the ionic conductivity is 0.228 S·cm. -1 .

[0034] Example 4

[0035] The fuel cell of the Ga-Mn dual-doped pyrochlore type La2Zr2O7 low-temperature ceramic electrolyte of the present invention:

[0036] The cathode and anode materials are commercially available Ni 0.8 Co 0.15 Al 0.05 LiO2 (NCAL) powder (≥99.9%, Sigma-Aldrich) was mixed and ground with polyvinylidene fluoride binder (5 wt% relative to NCAL) in terpineol to obtain a uniform slurry. The slurry was uniformly coated onto the surface of nickel foam (effective area: 0.64 cm²), and then dried at 120 °C for 30 minutes to remove the solvent, forming an NCAL coating with a thickness of about 10 μm. NCAL electrodes of the same specifications were prepared and used as the anode (3) and cathode (1) in the symmetrical battery structure, respectively. The preparation process is as follows. Figure 1 As shown.

[0037] The fuel cell was assembled by laminating an electrolyte membrane between two identical NCAL electrodes (NCAL|electrolyte|NCAL). The three-layer structure was then placed in a mold and cold-pressed at 200 MPa for 10 minutes to enhance interfacial contact, resulting in a compact sandwich structure single cell with an overall thickness of approximately 650 μm.

[0038] The electrolyte material is Ga-Mn double-doped pyrochlore-type La₂Zr₂O₇. Compared to undoped La₂Zr₂O₇, after Ga-Mn doping, the relevant characteristic lattice modes (such as Eg, F₂g, and Alg) are still identifiable, but peak broadening and enhanced defect-related features (including bands attributed to Ga-O / Mn-O vibrations and "oxygen vacancy-related" signals) become increasingly significant. This evolution indicates intensified local distortion and enhanced oxygen vacancy activation, but the parent lattice does not collapse, thus enhancing ion transport while maintaining phase stability. Figure 2 As shown, after Ga-Mn doping, the Fermi level position and surface potential of the material undergo significant changes. The undoped La2Zr2O7 exhibits a wide optical bandgap (Eg≈3.30 eV), consistent with the electron blocking characteristics of the zirconate framework. In contrast, LZGM-04 shows significantly enhanced visible light absorption and a narrowed bandgap (Eg≈2.02 eV), indicating that the electronic states derived from the dopant / defect are accompanied by lattice distortion and a vacancy-rich local environment. The work function increases from 4.66 eV (La2Zr2O7) to 6.26 eV (LZGM-04), proving that Ga-Mn doping significantly alters the Fermi level position and surface potential. For ceramic fuel cells, such a large chemical potential mismatch is expected to induce interfacial band bending and a space charge layer at the grain / electrode contact, thereby generating an internal electrostatic field—this field can both assist ion drift and construct an energy barrier that hinders the penetration of planar electrons, such as... Figure 6 As shown.

[0039] In the electrolyte material Ga-Mn dual-doped pyrochlore-type La2Zr2O7, Ga is used as Ga... 3+ Mn is incorporated into the oxide lattice in the form of Mn 2+ / Mn 3+ / Mn 4+ The coexistence of species: Manganese can act as an internal redox buffer under fuel cell operating conditions, regulating local charge fluctuations and stabilizing non-stoichiometric oxygen configuration. In Ga-Mn co-doped pyrochlore-type La2Zr2O7, the oxygen vacancy content increased from 36.6% in La2Zr2O7 to 53.2% in LZGM-04, reflecting the redistribution of oxygen species induced by co-doping. XPS and EPR results jointly confirmed the change in defect structure in LZGM-04, characterized by a large number of electronically active oxygen vacancies, such as... Figure 7 As shown.

[0040] Transport mechanism in Ga-Mn co-doped pyrochlore-type La₂Zr₂O₇ low-temperature ceramic electrolyte: Ga-Mn co-doping lowers the migration barrier through local electronic polarization, while stabilizing a higher concentration of mobile oxygen vacancies, thereby enhancing oxide ion conduction under solid oxide fuel cell operating conditions, such as... Figure 8 As shown. Density functional theory (DFT) was further used to elucidate the defect chemistry and electronic modulation mechanisms induced by Ga / Mn co-doping, such as... Figure 8 As shown. Figure 8 a and 8b respectively compare the environments in which oxygen vacancies form in pristine LZO and LZGM-04. Ga 3+ The incorporation of A sites (La sites) and the substitution of B sites (Zr sites) with Mn together perturb the local coordination geometry, resulting in a more asymmetric oxygen atom environment around oxygen vacancies in LZGM-04. This distortion is consistent with the reduced oxygen vacancy formation energy compared to undoped LZO, and is consistent with the experimentally observed enhanced chemical activity of oxygen vacancies. The CDD pattern of LZGM-04 (…) Figure 8 c) Provides direct electronic structure evidence. Significant charge accumulation around the oxygen ions near gallium and manganese, coupled with charge depletion in the adjacent metal-oxygen bonds, indicates the presence of heterovalent Ga... 3+ The mixed valence states of substitution and manganese participate in the enhanced polarization of MO bonds. This local charge rearrangement weakens the binding of lattice oxygen, thereby stabilizing oxygen vacancy formation and promoting vacancy migration, which together drive oxide ion transport.

[0041] The LZGM-04 sample was analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), and the results are as follows: Figure 3 As shown. EDX element distribution diagram ( Figure 3 (ae) shows the spatial distribution of La, Zr, O, Mn, and Ga within the selected region, while the corresponding superimposed distribution map ( Figure 3 f) summarizes the overall elemental distribution. In addition, EDX spectra collected from the same region ( Figure 3 g) confirmed the presence of all component elements, directly proving that Ga and Mn were successfully incorporated into the La-Zr-O framework structure.

[0042] The nanoscale morphology of the parent LZO and the representative co-doped electrolyte LZGM-04 was compared using HRTEM and AFM techniques. Figure 4 At different magnifications, LZO exhibits relatively dense plate-like aggregates. Figure 4 LZGM-04 exhibits a more refined nanoparticle assembly structure with clearer interparticle boundaries. Figure 4This structure is generally advantageous for maximizing interfacial contact in pressed electrolyte particles. Both samples exhibit clear lattice fringes, confirming their excellent crystallinity; notably, the measured interplanar spacing is significantly different from that of LZO (d≈0.319 nm). Figure 4 g) is transformed into LZGM-04 with d≈0.325nm ( Figure 4 This is consistent with the weak lattice relaxation phenomenon induced by gallium / manganese doping. Complementary AFM 3D topography images show significant height variations in LZO, while LZGM-04 exhibits a relatively uniform surface morphology, indicating that surface uniformity is improved after co-doping. The above observations demonstrate that Ga / Mn co-doping, while maintaining high crystallinity, modulates the microstructure and lattice parameters of La2Zr2O7, providing a structural basis for the enhanced electrochemical behavior discussed below.

[0043] Figure 5 The effects of Ga / Mn co-doping on the electrochemical performance of La₂Zr₂O₇ under H₂ / O₂ conditions were summarized. Compared to pristine LZO, the LZGM-04 electrolyte exhibited systematically higher current output and power density in the 430-550 °C range. Figure 5 (a, b) demonstrates that it achieves more efficient charge / ion transport while maintaining stable battery polarization behavior. This advantage becomes even more significant at low temperatures: the maximum power density increases from 708 mW / cm² at 550 °C. -2 Increased to 1171 mW cm -2 At 430℃, it drops from 174 mW cm⁻¹ -2 Jumping to 408 mW cm -2 ( Figure 5 g), confirming that co-doping technology effectively alleviates the common problem of kinetic performance degradation in intermediate-temperature SOFCs.

[0044] Electrochemical impedance spectroscopy further revealed the source of the performance improvement. At all measurement temperatures, the Nyquist plots of LZGM-04 showed a significantly smaller arc size compared to LZO. Figure 5 (c, 5d) Equivalent circuit fitting results show that the overall resistance of the co-doped electrolyte is always lower (e.g., 0.37Ω vs 0.52Ω at 550℃; 1.85 vs 3.03Ω at 430 °C). Figure 5 h). The resulting LZGM-04 ionic conductivity is improved across the entire temperature range. Figure 5 e), reaching ~0.28 S cm at 550 °C. -1 (LZO is ~0.20 S cm) -1 And it maintains a significant advantage even at low temperatures. Arrhenius analysis ( Figure 5f) shows that the activation energy of LZGM-04 (0.678 eV) is lower than that of LZO (0.770 eV), indicating that Ga / Mn co-doping not only increases the effective carrier concentration but also lowers the transport barrier. Combined polarization / EIS / conductivity results demonstrate that LZGM-04 achieves a measurable reduction in resistance and activation energy through defect engineering, thereby significantly improving power output under mid-temperature conditions.

Claims

1. A Ga-Mn dual-doped pyrochlore-type La₂Zr₂O₇ low-temperature ceramic electrolyte, characterized in that, The chemical formula of the low-temperature ceramic electrolyte is La. 2-x GaxZr 2-x MnxO 7-δ Where 0.2≤x≤0.6, δ is the oxygen nonstoichiometric defect caused by oxygen vacancies, 0<δ<1; the low-temperature ceramic electrolyte has a single-phase pyrochlore structure, Ga is used as Ga 3+ The form replaces part of the La bit, Mn with Mn 2+ / Mn 3+ / Mn 4+ The form replaces part of the Zr bit.

2. A method for preparing the Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte as described in claim 1, characterized in that, It is prepared using a citrate-assisted sol-gel method, including the following steps: (1) La is composed according to the target 2-x Ga x Zr 2-x MnxO 7-δ Weigh out lanthanum nitrate hexahydrate, zirconium nitrate hydrate, gallium nitrate hydrate and manganese nitrate hydrate, dissolve them in deionized water, and stir to form a transparent precursor solution; (2) Add chelating agent citric acid to the precursor solution, stir continuously and heat until a uniform gel is formed, dry the gel to obtain a dry gel, grind and calcinate to obtain Ga-Mn double-doped pyrochlore type La2Zr2O7 low temperature ceramic electrolyte.

3. The preparation method according to claim 2, characterized in that, The molar ratio of La, Zr, Ga, and Mn, calculated as metal cations, is (2-x):(2-x):x:x, where 0.2 ≤ x ≤ 0.6; the molar ratio of citric acid to total metal cations is 1.8:1 to 2.2:

1.

4. The preparation method according to claim 2, characterized in that, Step (2) specifically involves heating the mixed solution to 80-85°C under continuous stirring until a uniform gel is formed. The gel is then dried at 150-160°C to obtain a dry gel. After grinding, the gel is calcined in air at 1000-1100°C for 4-5 hours at a heating rate of 3-5°C / min.

5. A fuel cell using the Ga-Mn dual-doped pyrochlore-type La2Zr2O7 low-temperature ceramic electrolyte as described in claim 1, characterized in that, The battery has a symmetrical sandwich structure consisting of an anode, an electrolyte, and a cathode arranged in sequence; wherein the cathode and anode are NCAL electrodes of the same specification, and the electrolyte material is a Ga-Mn double-doped pyrochlore type La2Zr2O7 low-temperature ceramic electrolyte.

6. The fuel cell according to claim 5, characterized in that, The method for preparing the NCAL electrode is as follows: NCAL and polyvinylidene fluoride binder are mixed and ground in terpineol to obtain a uniform slurry. The slurry is uniformly coated onto the surface of the nickel foam, and then dried to remove the solvent, forming an NCAL coating, thus obtaining the NCAL electrode.

7. The fuel cell according to claim 5, characterized in that, The mass ratio of NCAL to polyvinylidene fluoride adhesive is 93:7 to 97:3, and the resulting coating thickness is 8 to 12 μm.

8. A method for preparing the fuel cell according to claim 5, characterized in that, By laminating an electrolyte membrane between two identical NCAL electrodes, and then placing the three-layer structure in a mold, cold-pressing it at 180–220 MPa for 8–12 minutes to enhance interfacial contact, a sandwich structure single cell with an overall thickness of 600–700 μm was finally obtained.

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