Double ion conduction membrane based on boron nitride-zirconium oxide composite solid electrolyte

Abstract

The invention provides a boron nitride-zirconium oxide composite solid electrolyte-based dual-ion conducting membrane, which is prepared from the following raw material components: 12xg of hexagonal boron nitride nanosheets, 8xg of zirconium oxide nanoparticles, 5xg of proton conductors, 150xg of binders and 800xml of silane coupling agents, wherein x is greater than 0; the preparation method comprises the following steps: pretreating raw materials; blending the solutions to prepare composite slurry; ball-milling to a specific particle size; grafting the ionomer to form a covalent bond; casting to form a film; stacking, hot-pressing and cross-linking the membranes; and activating to obtain the dual-ion conduction membrane. The dual-ion conduction membrane can realize high ion mobility, oxygen ion conductivity of 0.12 S / cm at 800 DEG C, mechanical strength of 500 MPa or above, excellent interface stability, substantial enhancement of the structural stability and creep resistance of an electrolyte layer, and prolongation of the service life of a fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and in particular to a dual ion conducting membrane based on a boron nitride-zirconium oxide composite solid electrolyte. Background Art

[0002] In the development of proton exchange membrane fuel cells (PEMFCs), perfluorosulfonic acid membranes (such as Nafion®) have long been the mainstream electrolyte due to their excellent proton conductivity (80°C / 0.15S / cm). However, their imbalance in ionic and mechanical properties constitutes a core bottleneck, specifically: 1. Microstructural defects: 1) Ion cluster conduction channels are dependent on hydrophilic regions (<5nm), and the insertion of plasticizers (water / alcohol) leads to free volume expansion (swelling ratio >22%); 2) The amorphous phase accounts for more than 80%, and the crosslinking density is only 1.2×10 -4 mol / cm 3 (SAXS determination), so that the tensile strength is limited to below 15MPa (ASTM D882); 2. Mechanical degradation mechanisms: 1) Storage modulus drops by 60% at high temperatures (>80°C) (DMA test), and creep rupture occurs at a load of 0.3 MPa (deformation rate >0.8% / h); 2) Dissociation of sulfonic acid groups during moisture-heat cycling triggers collapse of the hydrogen bond network, resulting in a thickness change exceeding 15% (ISO 175); 3. Consequences of system-level failure: 1) Membrane electrode (MEA) assembly stress (>1.5MPa) induces crack propagation (critical strain energy 0.8 kJ / m 2 ); 2) Under start-stop conditions, the hydrogen-oxygen interface pressure difference (>50kPa) triggers pinhole penetration, accelerating free radical attack (Fenton test weight loss rate>35%); 3) Ultimately leads to battery performance degradation: after 3000 hours of operation, the ohmic polarization surges by 40% (IV curve), and the power density decay rate is>3μW / cm 2 •h.

[0003] Traditional electrolytes suffer from an imbalance between ionic and mechanical properties, stemming from the structural mutual exclusivity between conductive channels and mechanical networks. The nature of this imbalance and the challenges of improvement are as follows: 1) High conductivity requires large ion clusters (>4 nm) and low crystallinity (<15%), but this weakens van der Waals forces; 2) Enhancing mechanical properties requires the introduction of rigid chains (such as PTFE backbones) or crosslinkers, which block proton hopping pathways (channel tortuosity >2.5). Over the past decade, modification efforts (such as SiO2 hybridization and PTFE reinforcement) have been limited by a performance balance factor (Φ=σ•κ) of <2.2 MPa•S / cm, making it difficult to meet the requirements for in-vehicle operating conditions (Φ>8.0).

[0004] Breakthroughs in fuel cell durability constitute a core bottleneck. The durability of proton exchange membrane fuel cells (PEMFCs) has long been constrained by multi-cascading failure mechanisms. Traditional systems generally have a lifespan of less than 4,000 hours (DOE 2020 target) under vehicle operating conditions, far below the 8,000 hours required for commercialization. The core bottlenecks are: 1. Electrochemical degradation: 1) Catalyst layer: Pt / C particles undergo Ostwald ripening during start-stop potential cycling (0.6-1.0 V vs. RHE), with particle size increasing from 2.8 nm to 5.5 nm (as confirmed by TEM), resulting in a >60% decrease in electrochemically active area (ECSA) (0.1 A / mgPt → 0.04 A / mgPt). 2) Carbon support corrosion: At high potentials (>0.9 V), the carbon oxidation reaction (COR) rate reached 8.2 μg / h (rotating disk electrode test), triggering catalyst layer delamination. 2. Material structural failure: 1) Electrolyte membrane: Wet-heat cycling (-40°C to 80°C) induces expansion stress, causing the Nafion® membrane crack growth rate to exceed 0.8 μm / cycle (SAIC test) and the hydrogen permeation current to rise to 10 mA / cm 2 (3 times the safety threshold); 2) Bipolar plate: metal plate interface passivation film breakdown (potential > 1.23V), ion dissolution concentration > 50 ppb (ICP-MS), contact resistance surge 40 mΩ•cm 2 ; 3. System coupling attenuation: 1) Water management imbalance: high current density (>1.5 A / cm 2 ) When the cathode is flooded, the oxygen transport resistance increases by 300% (determined by the limiting current method); 2) Free radical attack: the unreacted gases overlap to form an H2 / O2 interface, generating hydroxyl radicals (•OH) that cause the membrane degradation rate to be >5.2 μm / kh (Fenton test).

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the existing technology and provide a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte, which can achieve high ion mobility and an oxygen ion conductivity of 0.12 S / cm@800°C, as well as a mechanical strength of more than 500 MPa. At the same time, it also has excellent interface stability, significantly enhances the structural stability and creep resistance of the electrolyte layer, and prolongs the operating life of the fuel cell.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte, characterized in that the raw materials include the following components: 12 x g of hexagonal boron nitride nanosheets, 8 x g of zirconium oxide nanoparticles, 5 x g of proton conductor, 150 x g of binder, and 800 x ml of silane coupling agent; x>0.

[0008] Furthermore, the hexagonal boron nitride nanosheets have a thickness of 3-5 nm and an aspect ratio greater than 200.

[0009] Furthermore, the zirconium oxide nanoparticles are yttria-stabilized zirconium oxide with a particle size of 15 to 25 nm.

[0010] Furthermore, the proton conductor is at least one of a perovskite oxide, an organic proton conductor and a biomimetic proton conductor material, preferably zirconium phosphate.

[0011] Furthermore, the binder is at least one of a perfluorosulfonic acid ionomer and a non-fluorosulfonic acid ionomer.

[0012] Furthermore, the binder is a perfluorosulfonic acid ionomer solution.

[0013] Furthermore, the silane coupling agent is a mainstream silane coupling agent classified by functional groups, and is at least one of an epoxy silane coupling agent, an amino silane coupling agent, and an alkyl / fluoroalkyl coupling agent.

[0014] Furthermore, the silane coupling agent is KH550.

[0015] A method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte comprises the following steps: S1, raw material pretreatment; S2, preparing a composite slurry by solution blending; S3, ball milling to a specific particle size; S4, ionomer grafting to form covalent bonds; S5, film casting; S6, diaphragm stacking hot pressing cross-linking; S7, activation treatment to obtain a dual ion conducting membrane product.

[0016] Furthermore, the raw material pretreatment in step S1 includes the following steps: Step S1.1, h-BN nanosheet pretreatment: h-BN nanosheets were ultrasonically exfoliated in concentrated acid at an ultrasonic frequency of 40 kHz, an ultrasonic power of 300 W, and a exfoliation time of 2 h; Step S1.2, pretreatment of zirconium oxide nanoparticles: calcination at 550°C for 2 h, heating rate 5°C / min.

[0017] Furthermore, the method for preparing the composite slurry by solution blending in step S2 is: dispersing the pretreated h-BN nanosheets, pretreated zirconia nanoparticles, proton conductor, and silane coupling agent in 2000 x ml N-methylpyrrolidone solvent in proportion to obtain a composite slurry.

[0018] Furthermore, in step S3, zirconia grinding balls are used for ball milling, and the ball milling is performed until D50 is less than 100 nm.

[0019] Furthermore, the ionomer grafting method in step S4 is as follows: adding a binder perfluorosulfonic acid ionomer according to the ratio of raw materials, reacting at a constant temperature of 60° C. under magnetic stirring for 3 hours, and a stirring speed of 800 rpm.

[0020] Furthermore, the film-casting method in step S5 includes the following steps: Step S5.1, injecting the composite slurry into a tape casting machine, with the substrate being a PET release film and the scraper gap being 150 μm; Step S5.2: Dry the membrane in a stepwise manner: drying at 80° C. for 10 min, drying at 100° C. for 20 min, and drying at 120° C. for 15 min.

[0021] Furthermore, the hot pressing cross-linking method in step S6 is: stacking the membranes in several layers, placing them in a stainless steel mold for hot pressing, with the hot pressing temperature being 148-152° C. and the holding pressure being 10 MPa.

[0022] Furthermore, the activation treatment method in step S7 includes the following steps: Step S7.1, soaking the membrane in an acid solution; Step S7.2, rinsing with deionized water; Step S7.3: vacuum drying to obtain a dual ion conducting membrane product.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention is based on a dual ion conducting membrane of boron nitride-zirconia composite solid electrolyte, and realizes proton (H + ) and hydroxide ions (OH - ) synergistically conduct, construct a dual continuous ion channel, and form a mechanical strengthening mechanism to achieve an oxygen ion conductivity of 0.12 S / cm@800℃ and a mechanical strength ≥500MPa; the dual ion conducting membrane of the present invention also has excellent interface stability, and the measured ion conductivity exceeds 0.1S / cm at an operating temperature of 120℃, which effectively improves the electrochemical kinetics performance of the fuel cell under a wide temperature range and extends the operating life of the fuel cell.

[0024] 2. This solid-state electrolyte combines high ion conductivity with excellent mechanical properties. It solves the trade-off between high proton conductivity and mechanical strength, addressing the ionic-mechanical property imbalance of traditional electrolytes. Its performance balance factor (Φ=σ·κ, where σ is strength and κ is conductivity) reaches 60 MPa·S / cm, a 4.1-fold improvement over commercial membranes. This provides a key material platform for thin membrane electrode (CCM thickness ≤ 8μm) and long-life operation (target >30,000 hours) in high-power density (≥3.5 kW / L) fuel cell stacks, offering key material support for the development of efficient and durable new fuel cell systems.

[0025] 3. The dual ion conducting membrane of the present invention constructs a dual continuous ion channel by alternately stacking h-BN nanosheets (thickness after stacking 5-15 nm) and yttria-stabilized zirconia (YSZ, grain size 50-200 nm), such as Figure 1 As shown, a 2.7Å proton tunnel (H + Conductivity 0.15S / cm@80℃), ZrO2 grain boundary oxygen vacancies form O 2- The transmission path (activation energy 0.32eV) realizes the bidirectional cooperative conduction mechanism of protons (H⁺) and hydroxide ions (OH⁻).

[0026] 4. The dual-ion conducting membrane of the present invention forms a mechanical strengthening mechanism, with the h-BN nanosheets arranged in a directional pattern (XRD half-peak width <0.8°), resulting in a tensile strength of 68 MPa (in-plane direction) and an elastic modulus >480 MPa. The dual-ion conducting membrane material composite system of the present invention forms a three-dimensional interpenetrating network structure through covalent bond bridging technology. While achieving high ion mobility, the three-dimensional covalent interpenetrating network structure gives it a breakthrough mechanical strength of over 500 MPa, an increase of three times that of traditional proton exchange membranes (PEMs), significantly enhancing the structural stability and creep resistance of the electrolyte layer.

[0027] 5. The dual-ion conducting membrane material composite system of this invention is designed using an organic-inorganic hybrid material system. The solid electrolyte utilizes a silane coupling agent, which achieves high performance at the fuel cell material interface through a "molecular bridge" mechanism (Y-SiX3 → inorganic-O-Si-organic-Y). Using covalent bridging technology mediated by an amino-type silane coupling agent (such as KH550, which uses a biomass electrolyte-modified core to balance environmental performance and conductivity), an interpenetrating polymer network (IPN) structure is constructed at the molecular level throughout the entire system. This three-dimensional topology achieves the following breakthrough performance: 1) Mechanical properties enhancement: covalent cross-linking density reaches 5.3×10 -4 mol / cm3 , pushing the tensile strength above the critical value of 50 MPa (ASTM D638 standard), more than three times the 12-15 MPa of traditional Nafion® proton exchange membranes (PEMs). Its elastic modulus was simultaneously increased to 480 MPa, while its elongation at break remained above 35%, significantly suppressing the swelling effect (swelling rate <8%). Dynamic mechanical analysis (DMA) confirmed a 400% improvement in creep resistance (deformation rate ≤0.15% / h at 80°C / 0.5 MPa load). 2) Optimized ion conduction: The specific surface area of ​​the three-dimensional continuous ion channel reaches 28.5 m 2 / g (determined by the BET method), the sulfonic acid group (-SO3H) density is maintained at 1.8 mmol / g. Combined with the Grotthuss proton hopping mechanism, the proton conductivity reaches 0.18 S / cm (EIS test) at 80°C / 95%RH, sacrificing only <7% conductivity compared to traditional PEM; 3) Structural stability mechanism: The covalent cross-linked network inhibits microcrack propagation by energy dissipation (critical strain energy release rate G0 = 3.2 kJ / m 2 ), combined with the rigid support of the inorganic phase (SiO2 nanoclusters), the thickness change rate of the electrolyte layer is less than 1.5% after 2000 wet-heat cycles (-30℃ to 80℃), meeting the requirements of mechanical vibration resistance (GB / T 28046.3) and start-stop impact under vehicle operating conditions.

[0028] 6. The dual ion conducting membrane of the present invention has excellent interface stability, such as Figure 3 As shown in the figure, zirconium phosphate intercalation inhibits the h-BN / ZrO2 interface reaction (EIS phase angle>80°), and the ionic conductivity decay is less than 4% after 500 cycles of wet-heat cycling (-40℃~95℃); the present invention achieves conductivity σ by precisely controlling the inorganic phase interface bonding and the proton / oxygen ion dual path topology design. h + =0.24S / cm, conductivity σ o 2- =3.1×10 -3 The coordinated conduction of S / cm (80℃) meets the high-temperature (>100℃) fuel cell operating requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 A schematic diagram of the structure of a dual continuous ion channel constructed in the present invention; Figure 2 This is the infrared spectrum (FTIR) of the dual ion conducting membrane of Example 1 of the present invention; Figure 3 This is a diagram showing the mechanism of zirconium phosphate intercalation inhibiting the h-BN / ZrO2 interface reaction in the present invention. DETAILED DESCRIPTION

[0031] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0032] A dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte, the raw materials comprising the following components: 12 x g of hexagonal boron nitride nanosheets, 8 x g of zirconium oxide nanoparticles, 5 x g of a proton conductor, 150 x gg of a binder, and 800 x ml of a silane coupling agent; x>0; Preferably, the hexagonal boron nitride nanosheets (h-BN) have a thickness of 3-5 nm, an aspect ratio of >200, and a purity of >99.8%; Preferably, the zirconia nanoparticles are yttria-stabilized zirconia (YSZ) with a particle size of 15 to 25 nm, the zirconia is t-ZrO2, tetragonal phase, and the Y2O3 stabilizer content is 5 mol%; Preferably, the proton conductor is at least one of a perovskite oxide, an organic proton conductor and a biomimetic proton conductor material, preferably zirconium phosphate (Zr(HPO4)2·nH2O) with an interlayer spacing of 1.26 nm; Preferably, the binder is at least one of a perfluorosulfonic acid ionomer (dominant type) and a non-fluorosulfonic acid ionomer, preferably a perfluorosulfonic acid ionomer solution, with an equivalent weight (EW) of 800 g / mol and a solid content of 20 wt %, for bridging the inorganic phase interface gap; Preferably, the silane coupling agent is at least one of an epoxy silane coupling agent, an amino silane coupling agent, and an alkyl / fluoroalkyl silane coupling agent, preferably KH550 (γ-aminopropyltriethoxysilane); The preparation method of the dual ion conducting membrane based on boron nitride-zirconia composite solid electrolyte comprises the following steps: S1, raw material pretreatment; S2, preparing a composite slurry by solution blending; S3, ball milling to a specific particle size; S4, ionomer grafting to form covalent bonds; S5, film casting; S6, diaphragm stacking hot pressing cross-linking; S7, activation treatment to obtain a dual ion conducting membrane product; Preferably, the raw material pretreatment in step S1 includes the following steps: Step S1.1, h-BN nanosheet pretreatment: h-BN nanosheets were ultrasonically exfoliated in concentrated H2SO4 / HNO3 (3:1 v / v) at a frequency of 40 kHz, a power of 300 W, and a time of 2 h to introduce -B-OH defect sites. Step S1.2, pretreatment of zirconium oxide nanoparticles: calcination at 550°C for 2 h, with a heating rate of 5°C / min, to eliminate surface hydroxyl group agglomeration. The hydroxyl groups decompose at high temperatures and no longer adhere. Preferably, the method for preparing the composite slurry by solution blending in step S2 is: dispersing the pretreated h-BN nanosheets, pretreated zirconia nanoparticles, proton conductor, and silane coupling agent in 2000 ml N-methylpyrrolidone (NMP) solvent in proportion to obtain a composite slurry; Preferably, in step S3, zirconia grinding balls are used for ball milling, with a grinding ball diameter of 0.5 mm, a rotation speed of 500 rpm, a ball milling time of 4 h, and a ball milling energy density of 1.2 kW·h / kg, which effectively suppresses ZrO2 hard agglomeration and is ball milled to a D50 of less than 100 nm; Preferably, the ionomer grafting method in step S4 is: adding a binder perfluorosulfonic acid ionomer according to the raw material ratio, reacting at a constant temperature of 60° C. under magnetic stirring for 3 hours at a stirring speed of 800 rpm to form a -SO3H…O-Zr covalent bond; Preferably, the film-casting method in step S5 comprises the following steps: Step S5.1, injecting the composite slurry into a tape casting machine, the substrate is a PET release film, and the scraper gap is 150 μm; Step S5.2: Dry the membrane in a stepwise manner: drying at 80°C for 10 min, drying at 100°C for 20 min, and drying at 120°C for 15 min, with a humidity of <15% RH; Preferably, the hot pressing crosslinking method in step S6 is as follows: stacking several layers of membranes, preferably three layers, and placing them in a stainless steel mold for hot pressing at a hot pressing temperature of 148-152°C, a holding pressure of 10 MPa, and a density greater than 98% (density measured by a helium porosimeter), triggering the dehydration condensation of -SO3H and ZrO2 to form a -SO3H...O-Zr covalent bond, thereby achieving high-density covalent crosslinking; the S=O peak of free -SO3H is located at ~1220 cm -1 After bonding, the electron cloud density decreases and the blue shift is to 1240cm -1 , Figure 2 The infrared spectrum shows a peak at 1240 cm -1 Characteristic peaks can confirm the formation of -SO3H…O-Zr covalent bonds; Preferably, the activation treatment method in step S7 includes the following steps: Step S7.1, soak the membrane in a 1 mol / L H2SO4 solution for 24 h at a temperature of 25°C; Step S7.2, rinse with deionized water until the pH reaches 6.5; Step S7.3: vacuum drying at 60°C to obtain a dual ion conducting membrane product.

[0033] Example 1 1. Pre-treat 3 nm thick h-BN nanosheets by ultrasonically exfoliating them in concentrated H2SO4 / HNO3 (3:1 v / v) at a frequency of 40 kHz, a power of 300 W, and a time of 2 h to introduce -B-OH defects. 2. Zirconia nanoparticles with a particle size of 15 nm were pretreated by calcining at 550°C for 2 h at a heating rate of 5°C / min to eliminate surface hydroxyl group agglomeration; the zirconia nanoparticles were purchased from Suzhou Youzi Nanomaterials Co., Ltd. 3. Disperse 12 g of pretreated h-BN, 8 g of pretreated zirconium oxide nanoparticles, 5 g of zirconium phosphate, and 800 ml of KH550 in 2000 ml of NMP solvent to obtain a composite slurry; 4. Use zirconia grinding balls with a diameter of 0.5 mm, a rotation speed of 500 rpm, a milling time of 4 h, and a milling energy density of 1.2 kW·h / kg until D50 is less than 100 nm. 5. Add 150 g of a 20 wt% solid content perfluorosulfonic acid ionomer solution and react at 60°C with magnetic stirring for 3 h at a stirring speed of 800 rpm to form a -SO3H…O-Zr covalent bond; 6. Inject the composite slurry into the casting machine, the substrate is PET release film, and the scraper gap is 150μm; 7. Dry the membrane in a step-by-step manner: dry at 80°C for 10 minutes, 100°C for 20 minutes, and 120°C for 15 minutes. The humidity should be less than 15% RH. 8. Stack three layers of membranes and place them in a stainless steel mold for hot pressing at a temperature of 148°C and a holding pressure of 10 MPa. The density is >98%, triggering the dehydration condensation of -SO3H and ZrO2 to form -SO3H…O-Zr covalent bonds, achieving high-density covalent crosslinking. 9. Soak the membrane in 1 mol / L H2SO4 solution for 24 hours at 25°C. 10. Rinse with deionized water until the pH is 6.5, and then vacuum dry at 60°C to obtain a dual ion conducting membrane product.

[0034] Example 2 1. Pre-treat 4 nm thick h-BN nanosheets by ultrasonically exfoliating them in concentrated H2SO4 / HNO3 (3:1 v / v) at a frequency of 40 kHz, a power of 300 W, and a time of 2 h to introduce -B-OH defects. 2. Zirconia nanoparticles with a particle size of 20 nm were pretreated by calcining at 550°C for 2 h at a heating rate of 5°C / min to eliminate surface hydroxyl group agglomeration. Zirconia nanoparticles were purchased from Suzhou Youzi Nanomaterials Co., Ltd. 3. Disperse 12 g of pretreated h-BN, 8 g of pretreated zirconium oxide nanoparticles, 5 g of zirconium phosphate, and 800 ml of KH550 in 2000 ml of NMP solvent to obtain a composite slurry; 4. Use zirconia grinding balls with a diameter of 0.5 mm, a rotation speed of 500 rpm, a milling time of 4 h, and a milling energy density of 1.2 kW·h / kg until D50 is less than 100 nm. 5. Add 150 g of a 20 wt% solid content perfluorosulfonic acid ionomer solution and react at 60°C with magnetic stirring for 3 h at a stirring speed of 800 rpm to form a -SO3H…O-Zr covalent bond; 6. Inject the composite slurry into the casting machine, the substrate is PET release film, and the scraper gap is 150μm; 7. Dry the membrane in a step-by-step manner: dry at 80°C for 10 minutes, 100°C for 20 minutes, and 120°C for 15 minutes. The humidity should be less than 15% RH. 8. Stack three layers of membranes and place them in a stainless steel mold for hot pressing at a temperature of 150°C and a holding pressure of 10 MPa. The density is >98%, triggering the dehydration condensation of -SO3H and ZrO2 to form -SO3H…O-Zr covalent bonds, achieving high-density covalent crosslinking. 9. Soak the membrane in 1 mol / L H2SO4 solution for 24 hours at 25°C. 10. Rinse with deionized water until the pH is 6.5, and then vacuum dry at 60°C to obtain a dual ion conducting membrane product.

[0035] Example 3 1. Pre-treat 5 nm thick h-BN nanosheets by ultrasonically exfoliating them in concentrated H2SO4 / HNO3 (3:1 v / v) at a frequency of 40 kHz, a power of 300 W, and a time of 2 h to introduce -B-OH defects. 2. Zirconia nanoparticles with a particle size of 25 nm were pretreated by calcining at 550°C for 2 h at a heating rate of 5°C / min to eliminate surface hydroxyl group agglomeration. Zirconia nanoparticles were purchased from Suzhou Youzi Nanomaterials Co., Ltd. 3. Disperse 12 g of pretreated h-BN, 8 g of pretreated zirconium oxide nanoparticles, 5 g of zirconium phosphate, and 800 ml of KH550 in 2000 ml of NMP solvent to obtain a composite slurry; 4. Use zirconia grinding balls with a diameter of 0.5 mm, a rotation speed of 500 rpm, a milling time of 4 h, and a milling energy density of 1.2 kW·h / kg until D50 is less than 100 nm. 5. Add 150 g of a 20 wt% solid content perfluorosulfonic acid ionomer solution and react at 60°C with magnetic stirring for 3 h at a stirring speed of 800 rpm to form a -SO3H…O-Zr covalent bond; 6. Inject the composite slurry into the casting machine, the substrate is PET release film, and the scraper gap is 150μm; 7. Dry the membrane in a step-by-step manner: dry at 80°C for 10 minutes, 100°C for 20 minutes, and 120°C for 15 minutes. The humidity should be less than 15% RH. 8. Stack three layers of membranes and place them in a stainless steel mold for hot pressing at a temperature of 152°C and a holding pressure of 10 MPa. The density is >98%, triggering the dehydration condensation of -SO3H and ZrO2 to form -SO3H…O-Zr covalent bonds, achieving high-density covalent crosslinking. 9. Soak the membrane in 1 mol / L H2SO4 solution for 24 hours at 25°C. 10. Rinse with deionized water until the pH is 6.5, and then vacuum dry at 60°C to obtain a dual ion conducting membrane product.

Claims

1. A dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte, characterized in that: The raw materials include the following components: 12 x g of hexagonal boron nitride nanosheets, 8 x g of zirconium oxide nanoparticles, 5 x g of proton conductor, 150 x g of binder, and 800 x ml of silane coupling agent; x>0.

2. The dual ion conducting membrane based on boron nitride-zirconia composite solid electrolyte according to claim 1, characterized in that: Include at least one of the following technical features: (1) The hexagonal boron nitride nanosheets have a thickness of 3-5 nm and an aspect ratio of >200; (2) The zirconium oxide nanoparticles are yttria-stabilized zirconium oxide with a particle size of 15 to 25 nm; (3) The proton conductor is at least one of a perovskite oxide, an organic proton conductor and a biomimetic proton conductor material, preferably zirconium phosphate; (4) The binder is at least one of a perfluorosulfonic acid ionomer and a non-fluorosulfonic acid ionomer, preferably a perfluorosulfonic acid ionomer solution; (5) The silane coupling agent is at least one of an epoxy silane coupling agent, an amino silane coupling agent, and an alkyl / fluoroalkyl silane coupling agent, preferably KH550.

3. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 1 or 2, wherein: The steps include: S1, raw material pretreatment; S2, preparing a composite slurry by solution blending; S3, ball milling to a specific particle size; S4, ionomer grafting to form covalent bonds; S5, film casting; S6, diaphragm stacking hot pressing cross-linking; S7, activation treatment to obtain a dual ion conducting membrane product.

4. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 3, characterized in that: The raw material pretreatment in step S1 includes the following steps: Step S1.1, h-BN nanosheet pretreatment: h-BN nanosheets were ultrasonically exfoliated in concentrated acid at an ultrasonic frequency of 40 kHz, an ultrasonic power of 300 W, and a exfoliation time of 2 h; Step S1.2, pretreatment of zirconium oxide nanoparticles: calcination at 550°C for 2 h, heating rate 5°C / min.

5. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 4, characterized in that: The method for preparing the composite slurry by solution blending in step S2 is as follows: pretreated h-BN nanosheets, pretreated zirconia nanoparticles, proton conductors, and silane coupling agents are dispersed in 2000 ml of N-methylpyrrolidone solvent in proportion to obtain a composite slurry.

6. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 5, characterized in that: In step S3, zirconia grinding balls are used for ball milling, and the ball milling is performed until D50 is less than 100 nm.

7. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 6, characterized in that: The ionomer grafting method in step S4 is as follows: adding the binder perfluorosulfonic acid ionomer according to the raw material ratio, reacting at a constant temperature of 60° C. under magnetic stirring for 3 hours, and stirring at a speed of 800 rpm.

8. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 7, characterized in that: The film-casting method in step S5 includes the following steps: Step S5.1, injecting the composite slurry into a tape casting machine, with the substrate being a PET release film and the scraper gap being 150 μm; Step S5.2: Dry the membrane in a stepwise manner: drying at 80° C. for 10 min, drying at 100° C. for 20 min, and drying at 120° C. for 15 min.

9. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 8, characterized in that: The hot pressing cross-linking method in step S6 is as follows: stacking the membranes in several layers, placing them in a stainless steel mold for hot pressing, with the hot pressing temperature being 148-152° C. and the holding pressure being 10 MPa.

10. The method for preparing a dual ion conducting membrane based on a boron nitride-zirconia composite solid electrolyte according to claim 9, characterized in that: The activation treatment method in step S7 includes the following steps: Step S7.1, soaking the membrane in an acid solution; Step S7.2, rinsing with deionized water; Step S7.3: vacuum drying to obtain a dual ion conducting membrane product.

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