Flow battery composite membrane material and preparation method thereof

Abstract

The invention belongs to the technical field of electrochemical energy storage, and discloses a flow battery composite membrane material and a preparation method thereof, and the preparation method comprises the following steps: spraying a ZIF-8 metal organic framework solution to the positive electrode side of a microporous diaphragm, and drying to obtain the flow battery composite membrane material. According to the zinc-bromine flow battery and the preparation method thereof, ZIF-8 acts on the positive electrode side of the microporous diaphragm, ZIF-8 shows good chemical stability in an acidic electrolyte environment of the zinc-bromine flow battery and is not easily oxidized and degraded by bromine, and a stable framework ensures that a screening pore channel is kept complete in long-term operation and continuously plays a role in resisting bromine, so that the corrosion of a zinc negative electrode and the loss of bromine active substances are reduced, and the service life of the zinc-bromine flow battery is prolonged. The problems of low bromine permeation and bromine reaction rate on the positive electrode side of the zinc-bromine flow battery and the like can be effectively solved, and the coulombic efficiency and the voltage efficiency can be remarkably improved, so that the microporous diaphragm with excellent comprehensive performance is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and in particular relates to a composite membrane material for a flow battery and a preparation method thereof. Background Art

[0002] As an important electrochemical energy storage technology, zinc-bromine flow battery has broad application prospects in the field of large-scale energy storage due to its advantages such as high energy density, low cost and long cycle life. However, its industrialization has long been restricted by three core bottlenecks: (1) active bromine species (Br3 - / Br2) penetrates the diaphragm and triggers self-discharge, resulting in a sharp drop in coulombic efficiency (usually <85%) and continuous capacity decay; (2) uneven deposition of zinc anode forms dendrites, which easily pierce the diaphragm and cause battery short circuit, threatening safety and limiting cycle life (<500 times); (3) bromine / bromide (Br2 / Br2) at the positive electrode - The conversion reaction is slow, involves multiple steps, and requires high activation energy. Complexing agents are often added to the positive electrode to complex Br2 to improve solubility, but this further complicates the Br2 reaction pathway. The sluggishness of the Br2 reaction becomes a shortcoming in overall battery performance, generating a high polarization voltage that significantly reduces voltage efficiency and power density, resulting in low energy efficiency, limited power density, and low coulombic efficiency. These three bottlenecks have directly led to the industrialization dilemma of zinc-bromine flow batteries.

[0003] Traditional zinc-bromine flow battery separators have large pore sizes, weak bromine barrier properties, and are unable to suppress zinc dendrites. Ceramic membranes, while offering strong bromine barrier properties, suffer from high brittleness and low ionic conductivity. Furthermore, the Nafion membranes disclosed in existing patents rely primarily on pore size screening and lack a chemical adsorption mechanism, further limiting their bromine barrier effectiveness and application range. Therefore, there is an urgent need to develop new separator materials that combine high selectivity, high ionic conductivity, and strong mechanical and chemical stability. Summary of the Invention

[0004] In response to the problem of poor bromine barrier effect of Nafion membrane in the prior art, the main purpose of the present invention is to provide a liquid flow battery composite membrane material and a preparation method. The composite membrane material can solve the problems of slow bromine permeation and bromine reaction rate on the positive electrode side of zinc-bromine liquid flow batteries, and can significantly improve the coulombic efficiency and voltage efficiency.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a composite membrane material for a flow battery comprises the following steps:

[0007] The ZIF-8 metal organic framework solution is sprayed onto the positive electrode side of the microporous diaphragm and dried to obtain a liquid flow battery composite membrane material.

[0008] Further, the method further comprises the step of: spraying the V4C3T x The MXene dispersion liquid is mixed with the ZIF-8 solution and then sprayed on the positive side of the flow battery composite membrane material.

[0009] Further, the method further comprises the step of: x The spraying speed of the MXene dispersion liquid mixed with the ZIF-8 solution is 5-10 ml / min, and the spraying time is 5-10 min.

[0010] Further, the method further comprises the step of:

[0011] The Mo2CT x The MXene dispersion liquid is sprayed on the V4C3T X The MXene dispersion liquid is mixed with the ZIF-8 solution and then sprayed on the negative side of the flow battery composite membrane material, and dried, wherein T is -OH and -F, and x is 1.8-2.2.

[0012] Further, the Mo2CT x The concentration of the MXene dispersion liquid is 5-25 mg / mL.

[0013] Further, the Mo2CT x The spraying speed of the MXene dispersion liquid is 5-10 ml / min, and the spraying time is 5-10 min.

[0014] Further, the mass concentration of the ZIF-8 metal organic framework solution is 10%-30%.

[0015] Further, the spraying speed of the ZIF-8 metal organic framework solution is 5-10 ml / min, and the spraying time is 5-10 min.

[0016] Further, the V4C3T x The concentration of the MXene dispersion liquid is 20 mg / mL, the mass concentration of the ZIF-8 solution is 10%-30%, the spraying speed of the V4C3T x The volume ratio of the MXene dispersion liquid to the ZIF-8 solution is 8:2-2:8.

[0017] A flow battery composite membrane material.

[0018] Compared with the prior art, the present application has the following technical effects:

[0019] Since the ZIF-8 has a highly uniform microporous structure with a pore size of about 0.34 nm, it allows small-sized ions to pass through but can directly block Br2 and Br3 -The penetration of bromine is physically cut off, thereby achieving the bromine barrier function and significantly reducing capacity loss. Therefore, in the present invention, by acting ZIF-8 on the positive electrode side of the microporous diaphragm, ZIF-8 shows good chemical stability in the acidic electrolyte environment of the zinc-bromine flow battery, and is not easily oxidized and degraded by bromine. The stable framework ensures that its screening channels remain intact during long-term operation, continuously plays a bromine barrier role, reduces zinc negative electrode corrosion and bromine active material loss, improves battery stability, and can effectively solve the problems of bromine penetration and slow bromine reaction rate on the positive electrode side of the zinc-bromine flow battery, and can significantly improve the coulomb efficiency and voltage efficiency, thereby obtaining a microporous diaphragm with excellent comprehensive performance.

[0020] Further, V4C3T x The interlayer spacing of MXene powders can be more finely controlled by ion intercalation, surface functional group regulation, or interlayer effect of composite membrane materials. This precise control can design a structure that allows hydrated zinc ions (Zn 2+ ) efficiently through, while effectively blocking larger polybrominated ions (such as Br3 - , Br5 - ) or bromine molecules (Br2) channels, which are the core of inhibiting bromine penetration and battery self-discharge. And V4C3T x Multivalent states of vanadium (V 3+ / V 4+ / V 5+ ) Accelerate Br - / Br2 redox reaction, accelerates the reaction kinetics of Br, inhibits the polarization of bromine electrode, and thus improves voltage efficiency. x MXene is resistant to bromine corrosion, and the surface layer of vanadium oxide (VO x ) resists bromine corrosion, remains intact during long-term operation, continuously exerts its bromine barrier effect and accelerates bromine reaction kinetics, thereby increasing the life of the battery's microporous diaphragm.

[0021] Furthermore, Mo2CT x MXene forms a homogeneous electron transport layer on the negative electrode side of the microporous separator, eliminating local charge enrichment points and allowing zinc ions (Zn 2+ ) The electric field distribution during deposition is more uniform, avoiding the tip effect and suppressing zinc dendrites from the source. x The oxygen-containing groups (-OH) on the surface of MXene powder and Zn 2+ There is a strong interaction, forming an "ion pre-distribution channel" to guide Zn 2+ Preferential deposition in the gaps between MXene sheets rather than disordered accumulation. x MXene sheets construct nanoscale confinement spaces on the electrode surface, limiting the vertical growth direction of zinc deposition and forcing zinc to extend laterally to form a dense deposition layer. DETAILED DESCRIPTION

[0022] For the purposes of promoting an understanding of the principles of the application, the application will now be described more fully hereinafter. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0023] A method for preparing a composite membrane material of a flow battery of the present application, comprising the following steps:

[0024] 1. Modification of the positive side of the microporous separator

[0025] (1) Synthesis of V4AlC3 MAX phase precursor:

[0026] Synthesis by "high-temperature solid-phase reaction", mix vanadium powder (V), aluminum powder (Al) and carbon powder (C) according to the stoichiometric ratio of V:Al:C = 4:1:3. After mixing, the powder is ball milled under inert atmosphere for 8-24 hours, and then sintered at high temperature of 1500-2000℃ for 2-5 hours to make the elements fully react and diffuse. Then the sintered block is ground into fine powder (usually passed through a 400 mesh sieve, particle size < 38 μm), and V4AlC3 MAX phase precursor is obtained.

[0027] (2) V4C3T x Preparation of MXene powder:

[0028] Slowly add V4AlC3 powder into the pre-prepared etchant hydrofluoric acid with a mass concentration of 50%. Stir the reaction at 30-60℃ for 48-72 hours. During the etching process, the Al layer is dissolved, and -OH and -F functional groups are left on the surface of the MXene layer, forming V4C3T x MXene, T is -OH and -F, and x is in the range of 1.8-2.2. After the reaction is completed, an acidic slurry containing multi-layer "V4C3T x " MXene particles is obtained. The etched acidic slurry is repeatedly centrifuged at a speed of 3500-10000 rpm, and the supernatant is obtained, and the precipitate is redispersed with deionized water. This process is repeated several times until the pH of the supernatant is close to neutral (pH 7). Then the precipitate is freeze-dried to obtain V4C3T x MXene powder.

[0029] (3) Pretreatment of microporous separator

[0030] The microporous separator (thickness 0.5-1.0 mm, thickness uniformity <3%, plasticizer content <2%, BET specific surface area > 60-120 m 2 / g, cumulative pore volume > 0.15 ml / g, average pore size < 20 nm. ) Washing treatment can be used ethanol or deionized water ultrasonic cleaning porous membrane 15 min-30 min, to remove the surface impurities and contaminants, and then in a vacuum drying oven at 40-60 °C drying 12-24 hours, ready for use.

[0031] (4) Modification of the positive side of the microporous membrane

[0032] ① Modification of the positive side of the microporous membrane by ZIF-8

[0033] Take 50 ml of ZIF-8 metal organic framework solution with different mass fractions (10%-30%, preferably 10%, 20% and 30%) and use a spray gun to uniformly spray the dispersion liquid to the positive side of the microporous membrane with the same size, with a spray flow rate of 5 ml / min and a spraying time of 10 min. The sprayed microporous membrane is placed in a vacuum drying oven and dried at 60-100 °C for 6-12 h to obtain a ZIF-8 modified microporous membrane.

[0034] ② Modification of the positive side of the microporous membrane by ZIF-8 and V4C3T x Modification of the positive side of the microporous membrane by MXene

[0035] Take 200 mg of the prepared V4C3T x MXene powder is dispersed in 10 ml of deionized water and ultrasonically dispersed to form a V4C3T x MXene dispersion liquid. Then prepare ZIF-8 solutions with different mass fractions (10%-30%, preferably 10%, 20% and 30%).

[0036] Mix the V4C3T x MXene dispersion liquid and the ZIF-8 solution in different volume ratios (8:2-2:8, preferably 8:2, 6:4, 4:6 and 2:8) and magnetically stir for 30-60 min to form a V4C3T x MXene dispersion liquid and ZIF-8 solution with different volume ratios.

[0037] Take 50 ml of the above mixed solution and use a spray gun to uniformly spray the dispersion liquid to the positive side of the ZIF-8 modified microporous membrane with the same size, with a spray flow rate of 5 ml / min and a spraying time of 10 min. The sprayed microporous membrane is placed in a vacuum drying oven and dried at 60-100 °C for 6-12 h to complete the modification of the positive side of the microporous membrane by V4C3T x MXene / ZIF-8, to obtain a MXene / ZIF-8 modified microporous membrane.

[0038] 2. Modification of the negative side of the microporous membrane

[0039] (1) Synthesis of Mo2GaC MAX phase precursor

[0040] Synthesis by "high temperature solid phase reaction", molybdenum powder (Mo), gallium (Ga) and carbon powder (C) are weighed according to the stoichiometric ratio of Mo: Ga: C = 2: 1: 1 and placed in an agate mortar, and then ground for 1-2 h to mix uniformly. The mixed powder is ball milled under inert atmosphere for 8-24 h, and then sintered at high temperature of 1500 ℃-2000 ℃ for 2 h-5 h to make the elements fully react and diffuse. Then the sintered block is ground into fine powder (usually passed through a 400 mesh sieve, particle size <38 μm), and the MAX phase precursor is obtained.

[0041] (2) Mo2CT x Preparation of MXene powder:

[0042] The Mo2GaC powder is slowly added to the pre-prepared etchant hydrofluoric acid with a mass concentration of 50%. Stirring at 30 ℃-60 ℃ for 48 h-72 h. During the etching process, the Ga layer is dissolved, and -OH and -F functional groups are left on the surface of the MXene layer, forming Mo2CT x MXene, x is in the range of 1.8-2.2. After the reaction is completed, an acidic slurry containing multi-layer "Mo2CT x " MXene particles is obtained. The etched acidic slurry is repeatedly centrifuged at a speed of 3500-10000 rpm, and the supernatant is obtained, and the precipitate is redispersed with deionized water. This process is repeated several times until the pH of the supernatant is close to neutral. Then the precipitate is freeze-dried to obtain Mo2CT x MXene powder.

[0043] (3) Modification of the negative side of the microporous separator

[0044] The prepared Mo2CT x MXene powder is dispersed in a suitable dispersant (deionized water) to form a Mo2CT x MXene dispersion liquid with a concentration of 5-25 mg / mL. Take 50 ml of the above Mo2CT x MXene dispersion liquid, and use an airbrush to uniformly spray the dispersion liquid onto the negative side of the above MXene / ZIF-8 modified microporous separator, with a spraying speed of 5 ml / min and a spraying time of 10 min. The sprayed microporous separator is placed in a vacuum drying oven and dried at 60 ℃-100 ℃ for 6 h-12 h. Finally, the microporous separator modified on both the positive and negative sides is obtained, that is, the flow battery composite membrane material.

[0045] The application first synthesizes V4AlC3 MAX and Mo2GaC MAX by adopting a high-temperature solid-phase reaction, and then performs selective etching on the V4AlC3 MAX and Mo2GaC MAX by using hydrofluoric acid (HF) through a wet chemical etching process, so as to obtain V4C3T x and Mo2CT x MXene. After the V4C3T x MXene dispersion liquid is mixed with the ZIF-8 solution to modify the positive electrode side of the microporous diaphragm, the bromine permeation problem and the kinetic reaction of bromine can be effectively slowed down. On the basis of the modification of the positive electrode side of the microporous diaphragm, the Mo2CT x MXene is used to modify the negative electrode side of the microporous diaphragm, which can further effectively slow down the zinc dendrite growth problem.

[0046] The technical solutions of the application will be described in detail below in combination with specific embodiments, and the embodiments do not constitute a limitation on the application.

[0047] Table 1 Synthesis conditions of composite film materials in different embodiments

[0048]

[0049] Example 1

[0050] 1) Microporous diaphragm pretreatment: The microporous diaphragm is cleaned and treated, and can be ultrasonically cleaned with ethanol or deionized water for 30 min to remove impurities and pollutants on the surface, and then dried in a vacuum drying oven at 60 DEG C for 12 hours for standby.

[0051] 2) Take 50 ml of a 10% mass fraction ZIF-8 solution, and use an airbrush to uniformly spray the dispersion liquid to the positive electrode side of the microporous diaphragm, with a spraying speed of 5 ml / min and a spraying time of 10 min. The microporous diaphragm after spraying is placed in a vacuum drying oven and dried at 80 DEG C for 12 h to obtain a ZIF-8 modified microporous diaphragm.

[0052] Example 2

[0053] 1) The microporous diaphragm pretreatment is the same as in Example 1.

[0054] 2) Take 50 ml of a 20% mass fraction ZIF-8 solution, and use an airbrush to uniformly spray the dispersion liquid to the positive electrode side of the microporous diaphragm, with a spraying speed of 5 ml / min and a spraying time of 10 min. The microporous diaphragm after spraying is placed in a vacuum drying oven and dried at 80 DEG C for 12 h to obtain a ZIF-8 modified microporous diaphragm.

[0055] Example 3

[0056] 1) The microporous diaphragm pretreatment is the same as in Example 1.

[0057] 2) Take 50 ml of ZIF-8 solution with a mass fraction of 30%, and use an airbrush to uniformly spray the dispersion liquid to the positive side of the microporous membrane, with a spraying speed of 5 ml / min and a spraying time of 10 min. Place the sprayed microporous membrane in a vacuum drying oven and dry at 80°C for 12 h to obtain a ZIF-8 modified microporous membrane.

[0058] Example 4

[0059] 1) Mix vanadium powder (V), aluminum powder (Al) and carbon powder (C) uniformly according to the stoichiometric ratio of V:Al:C = 4:1:3. Ball mill the mixed powder under inert atmosphere for 24 hours, and then sinter at high temperature of 1500°C for 3h to make the elements fully react and diffuse. Then grind the sintered block into fine powder (usually pass through a 400 mesh sieve, particle size < 38 μm) to obtain a MAX phase precursor, i.e. V4AlC3 powder.

[0060] 2) Slowly add V4AlC3 powder to the pre-prepared etchant HF and stir at 50°C for 48h. During the etching process, the Al layer is dissolved, and -OH and -F functional groups are left on the surface of the MXene layer, forming V4C3T x MXene, x is in the range of 1.8-2.2. After the reaction is completed, an acidic slurry containing multi-layer V4C3T x MXene particles is obtained. Centrifuge the etched acidic slurry repeatedly at a speed of 6000 rpm, take the supernatant, and redisperse the precipitate with deionized water. This process is repeated several times until the pH of the supernatant approaches neutral. Then freeze-dry the precipitate to obtain V4C3T x MXene powder.

[0061] 3) Pretreatment of microporous membrane: clean the microporous membrane by ultrasonic cleaning with ethanol or deionized water for 30 min to remove surface impurities and contaminants, and then dry in a vacuum drying oven at 60°C for 12 hours for standby.

[0062] 4) Take 2000 mg of prepared V4C3T x MXene and disperse in 100 ml deionized water, and finally form a V4C3T x MXene dispersion liquid with a concentration of 20 mg / ml. Prepare a ZIF-8 solution with a mass fraction of 30%.

[0063] Mix V4C3T x MXene and ZIF-8 solution in a volume ratio of 8:2, and magnetically stir for 30 min to finally form V4C3T xThe mixed solution of MXene dispersion liquid and ZIF-8 solution in a volume ratio of 8:2.

[0064] The V4C3T x The mixed solution of MXene dispersion liquid and ZIF-8 solution in a volume ratio of 8:2 was taken 50ml, and the dispersion liquid was uniformly sprayed to the positive side of the microporous membrane of the same size by using a spray gun, the spraying flow rate was 5ml / min, the spraying time was 10min, and the sprayed microporous membrane was placed in a vacuum drying box and dried at 80℃ for 12h to complete the V4C3T x Modification of the positive side of the microporous membrane by MXene / ZIF-8.

[0065] Example 5

[0066] 1) V4C3T x The MXene powder was prepared according to Example 4.

[0067] 2) The pretreatment of the microporous membrane was the same as Example 1.

[0068] 3) 20mg / ml of V4C3T x The MXene dispersion liquid was prepared according to Example 4, and a ZIF-8 solution with a mass fraction of 30% was prepared.

[0069] 4) The V4C3T x The MXene and ZIF-8 solution were mixed and magnetically stirred for 30min, and finally the V4C3T x The mixed solution of MXene dispersion liquid and ZIF-8 solution in a volume ratio of 6:4.

[0070] 5) The V4C3T x The mixed solution of MXene dispersion liquid and ZIF-8 solution in a volume ratio of 6:4 was taken 50ml, and the dispersion liquid was uniformly sprayed to the positive side of the microporous membrane of the same size by using a spray gun, the spraying flow rate was 5ml / min, the spraying time was 10min, and the sprayed microporous membrane was placed in a vacuum drying box and dried at 80℃ for 12h to complete the V4C3T x Modification of the positive side of the microporous membrane by MXene / ZIF-8.

[0071] Example 6

[0072] 1) V4C3T x The MXene powder was prepared according to Example 4.

[0073] 2) The pretreatment of the microporous membrane was the same as Example 1.

[0074] 3) 20mg / ml of V4C3T xThe MXene dispersion liquid was prepared according to the process of Example 4, and a ZIF-8 solution with a mass fraction of 30% was prepared.

[0075] 4) The V4C3T MXene and the ZIF-8 solution were mixed at a volume ratio of 4:6, and magnetic stirring was performed for 30 min, to finally form V4C3T MXene / ZIF-8. X The MXene dispersion liquid was prepared according to the process of Example 4, and a ZIF-8 solution with a mass fraction of 30% was prepared. x The MXene dispersion liquid and the ZIF-8 solution were mixed at a volume ratio of 4:6.

[0076] 5) The V4C3T MXene and the ZIF-8 solution were mixed at a volume ratio of 4:6, and magnetic stirring was performed for 30 min, to finally form V4C3T MXene / ZIF-8. x The MXene dispersion liquid and the ZIF-8 solution were mixed at a volume ratio of 4:6. x The MXene / ZIF-8 was modified on the positive side of the microporous membrane.

[0077] Example 7

[0078] 1) The V4C3T MXene was prepared according to the process of Example 4. x The MXene powder was prepared according to the process of Example 4.

[0079] 2) The microporous membrane was pretreated according to Example 1.

[0080] 3) The V4C3T MXene was prepared according to the process of Example 4. x The MXene dispersion liquid was prepared according to the process of Example 4, and a ZIF-8 solution with a mass fraction of 30% was prepared.

[0081] 4) The V4C3T MXene and the ZIF-8 solution were mixed at a volume ratio of 2:8, and magnetic stirring was performed for 30 min, to finally form V4C3T MXene / ZIF-8. x The MXene dispersion liquid was prepared according to the process of Example 4, and a ZIF-8 solution with a mass fraction of 30% was prepared. x The MXene dispersion liquid and the ZIF-8 solution were mixed at a volume ratio of 2:8.

[0082] 5) The V4C3T MXene and the ZIF-8 solution were mixed at a volume ratio of 2:8, and magnetic stirring was performed for 30 min, to finally form V4C3T MXene / ZIF-8. x The MXene dispersion liquid and the ZIF-8 solution were mixed at a volume ratio of 2:8. x The MXene / ZIF-8 was modified on the positive side of the microporous membrane.

[0083] Example 8

[0084] 1) The V4C3T MXene was prepared according to the process of Example 4.x MXene powder preparation is the same as Example 4.

[0085] 2) Microporous membrane pretreatment is the same as Example 1.

[0086] 3) 20 mg / ml of V4C3T x MXene dispersion liquid preparation process is the same as Example 4, and a 30% mass fraction of ZIF-8 solution is prepared.

[0087] 4) V4C3T x MXene and ZIF-8 solution are mixed and magnetically stirred for 60 min, and finally V4C3T X The mixed solution of MXene dispersion liquid and ZIF-8 solution is 6:4 in volume ratio.

[0088] 5) The above V4C3T x Take 50 ml of the mixed solution of MXene dispersion liquid and ZIF-8 solution in a volume ratio of 6:4, and use a spray gun to uniformly spray the dispersion liquid to the positive side of the microporous membrane of the same size, the spray flow rate is 5 ml / min, the spraying time is 10 min, and the sprayed microporous membrane is placed in a vacuum drying box and dried at 80°C for 12 h, to complete the V4C3T x MXene / ZIF-8 modification of the positive side of the microporous membrane.

[0089] Example 9

[0090] 1) V4C3T x MXene powder preparation is the same as Example 4.

[0091] 2) Microporous membrane pretreatment is the same as Example 1.

[0092] 3) 20 mg / ml of V4C3T x MXene dispersion liquid preparation process is the same as Example 4, and a 30% mass fraction of ZIF-8 solution is prepared.

[0093] 4) V4C3T x MXene and ZIF-8 solution are mixed and magnetically stirred for 60 min, and finally V4C3T x The mixed solution of MXene dispersion liquid and ZIF-8 solution is 6:4 in volume ratio.

[0094] 5) The above V4C3T xA mixed solution of MXene dispersion liquid and ZIF-8 solution with a volume ratio of 6:4 was taken 50 ml, and the dispersion liquid was uniformly sprayed to the positive side of the microporous separator with the same size by using an airbrush, the spraying flow rate was 10 ml / min, and the spraying time was 5 min. The sprayed microporous separator was placed in a vacuum drying oven and dried at 80°C for 12 h to complete the V4C3T x MXene / ZIF-8 modification of the positive side of the microporous separator.

[0095] Example 10

[0096] 1) Modification of the positive side of the microporous separator

[0097] The modification of the positive side of the microporous separator was the same as in Example 8.

[0098] 2) Modification of the negative side of the microporous separator

[0099] Molybdenum powder (Mo), gallium (Ga) and carbon powder (C) were weighed according to the stoichiometric ratio of Mo:Ga:C=2:1:1 and placed in an agate mortar, and ground for 1 h to mix uniformly. The mixed powder was ball milled under inert atmosphere for 24 hours, and then sintered at high temperature of 1500°C for 3 h to make the elements fully react and diffuse. Then the sintered block was ground into fine powder (usually passed through a 400 mesh sieve, particle size <38 μm) to obtain the MAX phase precursor.

[0100] 3) The Mo2GaC powder was slowly added to the pre-prepared etchant HF. Stirring at 50°C for 48 h. During the etching process, the Ga layer is dissolved, and at the same time, -OH and -F functional groups are left on the surface of the MXene layer, forming Mo2CT x MXene, x is in the range of 1.8-2.2. After the reaction, an acidic slurry containing multi-layer "Mo2CT x " MXene particles was obtained. The etched acidic slurry was repeatedly centrifuged at a speed of 6000 rpm, and the supernatant was obtained, and the precipitate was redispersed with deionized water. This process was repeated several times until the pH of the supernatant was close to neutral. Then the precipitate was freeze-dried to obtain Mo2CT x MXene powder.

[0101] 4) 500 mg of prepared Mo2CT x MXene was dispersed in 100 ml of deionized water, and ultrasonic dispersion was carried out to finally form a Mo2CT x MXene dispersion liquid with a concentration of 5 mg / ml. 5 mg / ml of Mo2CT xMXene dispersion liquid 50ml, the dispersion liquid is uniformly sprayed to the negative side of the above positive side modified microporous separator by using a spray gun, the spraying flow rate is 5ml / min, the spraying time is 10min, the sprayed microporous separator is placed in a vacuum drying box and dried at 80℃ for 12h, and finally the microporous separator modified on both positive and negative sides is obtained.

[0102] Example 11

[0103] 1) Modification of the positive side of the microporous separator

[0104] The modification of the positive side of the microporous separator is the same as that in Example 8.

[0105] 2) Modification of the negative side of the microporous separator

[0106] Mo2CT x The MXene powder is prepared in the same manner as in Example 10.

[0107] 1000mg of prepared Mo2CT x The MXene is dispersed in 100ml of deionized water, ultrasonic dispersion is performed, and finally a Mo2CT x MXene dispersion liquid. 10mg / ml of Mo2CT x MXene dispersion liquid 50ml, the dispersion liquid is uniformly sprayed to the negative side of the above positive side modified microporous separator by using a spray gun, the spraying flow rate is 5ml / min, the spraying time is 10min, the sprayed microporous separator is placed in a vacuum drying box and dried at 80℃ for 12h, and finally the microporous separator modified on both positive and negative sides is obtained.

[0108] Example 12

[0109] 1) Modification of the positive side of the microporous separator

[0110] The modification of the positive side of the microporous separator is the same as that in Example 8.

[0111] 2) Modification of the negative side of the microporous separator

[0112] Mo2CT x The MXene powder is prepared in the same manner as in Example 10.

[0113] 1500mg of prepared Mo2CT x The MXene is dispersed in 100ml of deionized water, ultrasonic dispersion is performed, and finally a Mo2CT x MXene dispersion liquid. 15mg / ml of Mo2CT xMXene dispersion liquid 50 ml, the dispersion liquid is uniformly sprayed to the negative side of the above positive side modified microporous separator by using a spray gun, the spraying flow rate is 5 ml / min, the spraying time is 10 min, the sprayed microporous separator is placed in a vacuum drying box and dried at 80°C for 12 h, and finally the microporous separator modified on both the positive and negative sides is obtained.

[0114] Example 13

[0115] 1) Modification of the positive side of the microporous separator

[0116] The modification of the positive side of the microporous separator is the same as that in Example 8.

[0117] 2) Modification of the negative side of the microporous separator

[0118] Mo2CT x The MXene powder is prepared according to Example 10.

[0119] 2000 mg of prepared Mo2CT x The MXene is dispersed in 100 ml of deionized water, ultrasonic dispersion is performed, and finally a Mo2CT x MXene dispersion liquid. 20 mg / ml of Mo2CT x MXene dispersion liquid 50 ml, the dispersion liquid is uniformly sprayed to the negative side of the above positive side modified microporous separator by using a spray gun, the spraying flow rate is 5 ml / min, the spraying time is 10 min, the sprayed microporous separator is placed in a vacuum drying box and dried at 80°C for 12 h, and finally the microporous separator modified on both the positive and negative sides is obtained.

[0120] Example 14

[0121] 1) Modification of the positive side of the microporous separator

[0122] The modification of the positive side of the microporous separator is the same as that in Example 8.

[0123] 2) Modification of the negative side of the microporous separator

[0124] Mo2CT x The MXene powder is prepared according to Example 10.

[0125] 2500 mg of prepared Mo2CT x The MXene is dispersed in 100 ml of deionized water, ultrasonic dispersion is performed, and finally a Mo2CT x MXene dispersion liquid. 25 mg / ml of Mo2CT x50 ml of MXene dispersion was evenly sprayed onto the negative electrode side of the modified microporous diaphragm on the positive electrode side using a spray gun. The spray rate was 5 ml / min and the spraying time was 10 min. The sprayed microporous diaphragm was placed in a vacuum drying oven and dried at 80 ° C for 12 h to finally obtain a microporous diaphragm with modified positive and negative electrodes.

[0126] Comparative Example 1

[0127] V4C3T x The preparation process of MXene powder is the same as that in Example 4.

[0128] The pretreatment of the microporous membrane is the same as that in Example 1.

[0129] Take 2000mg of prepared V4C3T x MXene was dispersed in 100 ml of deionized water and ultrasonically dispersed to form a V4C3T with a concentration of 20 mg / ml. x MXene dispersion.

[0130] Take 50ml of the above V4C3T x MXene dispersion was sprayed evenly onto the positive electrode side of the microporous diaphragm of the same size using a spray gun at a spray rate of 5 ml / min and a spraying time of 10 min. The sprayed microporous diaphragm was placed in a vacuum drying oven and dried at 80 ° C for 12 h to complete the V4C3T x MXene modification of the positive electrode side of the microporous separator.

[0131] Comparative Example 2

[0132] In this comparative example 2, a microporous membrane was used to conduct a battery performance test, wherein the membrane pretreatment was the same as that in the above embodiment 1. The coulombic efficiency was measured to be 91.0%, the voltage efficiency was 82.7%, and the energy efficiency was 75.257%.

[0133] To test the performance of the zinc-bromine flow battery membranes of Examples 1 to 14 and Comparative Examples 1-2, conventional electrode materials and electrolyte systems of zinc-bromine flow batteries were used to assemble the batteries. Charge and discharge tests were conducted on a battery testing system at a charge and discharge rate of 20 mA / cm 2 , charging time is 2 hours, test temperature is 25℃, test results are shown in Table 2.

[0134] Table 2 Comparison of electrochemical performance of zinc-bromine flow batteries under different embodiment conditions

[0135] No. Coulombic efficiency Voltage efficiency Energy efficiency Example 1 91.3％ 82.9％ 75.688％ Example 2 91.5％ 83.2％ 76.128％ Example 3 91.8％ 83.7％ 76.837％ Example 4 93.6％ 85.5％ 80.028％ Example 5 94.5％ 85.9％ 81.176％ Example 6 94.0％ 85.3％ 80.182％ Example 7 93.2％ 85.2％ 79.406％ Example 8 95.0％ 86.2％ 81.890％ Example 9 94.2％ 85.6％ 80.635％ Example 10 95.4％ 86.5％ 82.521％ Example 11 95.8％ 86.9％ 83.250％ Example 12 96.3％ 87.2％ 83.974％ Example 13 96.9％ 87.4％ 84.691％ Example 14 97.2％ 87.7％ 85.244％ Comparative Example 1 91.8％ 83.7％ 76.837％ Comparative Example 2 91.0％ 82.7％ 75.257％

[0136] As can be seen from Table 2, Examples 1-10 and Comparative Example 1 all exhibit better electrochemical performance data than Comparative Example 2, proving that when MXene materials and ZIF-8 materials are used to modify microporous separators or bipolar plates, the energy efficiency, coulombic efficiency and voltage efficiency of the zinc-bromine flow battery can be improved, indicating that MXene materials and ZIF-8 materials have a significant impact on improving the bromine-blocking ability, accelerating the bromine reaction kinetics and inhibiting zinc dendrite growth.

[0137] The electrochemical performance of the zinc-bromine flow battery assembled from the composite film materials of Examples 1-3 and Comparative Examples 1-2 is shown in Table 3.

[0138] Table 3 Comparison of electrochemical performance of zinc-bromine flow battery under different example conditions

[0139]

[0140]

[0141] Comparative Example 1-Example 3, different concentrations of ZIF-8 solution were used to measure the electrochemical performance data of the zinc-bromine flow battery, including energy efficiency, voltage efficiency, coulombic efficiency and other parameters. As can be seen from Table 3, Example 3 obtained relatively better comprehensive electrochemical performance, proving that the higher the concentration of ZIF-8 used to make the composite film material, the higher the coulombic efficiency, voltage efficiency and energy efficiency, indicating that the composite film material made from ZIF-8 solution of different concentrations has a profound impact on the bromine-blocking ability of the zinc-bromine flow battery.

[0142] The electrochemical performance of the zinc-bromine flow battery assembled from the composite film materials of Examples 3-7 and Comparative Examples 1-2 is shown in Table 4.

[0143] Table 4 Comparison of electrochemical performance of zinc-bromine flow battery under different example conditions

[0144] No. Coulombic efficiency Voltage efficiency Energy efficiency Example 3 91.8％ 83.7％ 76.837％ Example 4 93.6％ 85.5％ 80.028％ Example 5 94.5％ 85.9％ 81.176％ Example 6 94.0％ 85.3％ 80.182％ Example 7 93.2％ 85.2％ 79.406％ Comparative Example 1 91.8％ 83.7％ 76.837％ Comparative Example 2 91.0％ 82.7％ 75.257％

[0145] Comparative Example 3-Example 7 and Comparative Example 1, V4C3T x The electrochemical performance data measured when the MXene dispersion liquid and the ZIF-8 solution were used to modify the positive electrode side of the microporous separator of the zinc-bromine flow battery, including energy efficiency, voltage efficiency, coulombic efficiency and other parameters, as can be seen from Table 4, when V4C3T x When the MXene dispersion liquid and the ZIF-8 solution are used to modify the positive electrode side of the microporous separator at the same time, they exhibit better electrochemical performance data than Example 3 and Comparative Example 1, indicating that V4C3T x The MXene dispersion liquid and the ZIF-8 solution can exhibit effective bromine-blocking function and the ability to improve bromine reaction kinetics.

[0146] Comparative Example 4 - Example 7, Example 5 shows better electrochemical performance data, indicating that V4C3T x The volume ratio of MXene dispersion liquid to ZIF-8 solution with a mass fraction of 30% has a profound influence on the performance of the composite film. From the above table, it can be seen that when the volume ratio of MXene dispersion liquid to ZIF-8 solution with a mass fraction of 30% is 6:4, better electrochemical performance data is shown than other ratios. x The volume ratio of MXene dispersion liquid to ZIF-8 solution with a mass fraction of 30% has a profound influence on the performance of the composite film. From the above table, it can be seen that when the volume ratio of MXene dispersion liquid to ZIF-8 solution with a mass fraction of 30% is 6:4, better electrochemical performance data is shown than other ratios.

[0147] The electrochemical performance of the composite film materials of Example 5, Example 8 and Example 9 assembled into zinc-bromine flow batteries is shown in Table 5.

[0148] Table 5 Comparison of electrochemical performance of zinc-bromine flow batteries under different example conditions

[0149] No. Coulombic efficiency Voltage efficiency Energy efficiency Example 5 94.5％ 85.9％ 81.176％ Example 8 95.0％ 86.2％ 81.890％ Example 9 94.2％ 85.6％ 80.635％

[0150] The electrochemical performance data of the composite film materials of Comparative Example 5, Example 8-Example 9 under different synthesis conditions for zinc-bromine flow batteries, including energy efficiency, voltage efficiency, coulomb efficiency and other parameters, from Table 5, it can be seen that Example 8 obtains relatively better comprehensive electrochemical performance, proving that the composite film material prepared by increasing the magnetic stirring time and reducing the spraying rate has the effect of improving the coulomb efficiency, voltage efficiency and energy efficiency of the zinc-bromine flow battery, indicating that the composite film material prepared by different magnetic stirring time and spraying rate has a profound influence on the bromine resistance and accelerating the bromine reaction kinetics of the zinc-bromine flow battery.

[0151] The electrochemical performance of the composite film materials of Example 8, Example 10-Example 14 assembled into zinc-bromine flow batteries is shown in Table 6.

[0152] Table 6 Comparison of electrochemical performance of zinc-bromine flow batteries under different example conditions

[0153] No. Coulombic efficiency Voltage efficiency Energy efficiency Example 8 95.0％ 86.2％ 81.890％ Example 10 95.4％ 86.5％ 82.521％ Example 11 95.8％ 86.9％ 83.250％ Example 12 96.3％ 87.2％ 83.974％ Example 13 96.9％ 87.4％ 84.691％ Example 14 97.2％ 87.7％ 85.244％

[0154] The electrochemical performance data measured by modifying the positive and negative sides of the microporous separator of Comparative Example 8, Example 10-Example 14, including energy efficiency, voltage efficiency, coulomb efficiency and other parameters, from Table 6, it can be seen that on the basis of the modification of the positive side of the microporous separator in Example 8, the use of Mo2CT x The negative modification of the microporous separator by MXene shows better electrochemical performance data, indicating that Mo2CT x MXene can show effective inhibition of zinc dendrites.

[0155] Comparing Examples 10 to 14, Example 14 shows better electrochemical performance data, indicating that the higher the concentration of Mo2CT x The composite membrane material made of MXene dispersion has higher coulombic efficiency, voltage efficiency and energy efficiency, indicating that different concentrations of Mo2CT x Composite membrane materials made of MXene dispersions have a profound impact on the ability of zinc-bromine flow batteries to suppress zinc dendrites.

[0156] The present invention uses a partitioning design to act on the positive and negative sides of the microporous diaphragm with ZIF-8 and MXene materials, first synthesizing V4AlC3MAX and Mo2GaC MAX, and then selectively etching V4AlC3MAX and Mo2GaCMAX with hydrofluoric acid (HF) through a wet chemical etching process to obtain V4C3T x and Mo2CT x MXene. V4C3T x After the MXene dispersion is mixed with the ZIF-8 solution, the cathode side of the microporous membrane is modified, which can effectively alleviate the problem of bromine penetration and the slow kinetic reaction of bromine. x MXene can modify the negative electrode side of the microporous separator to further effectively slow down the growth of zinc dendrites, and has broad application prospects.

[0157] The above description is merely a description of the preferred embodiment of the present invention and is not to be construed as limiting the claims. The present invention is not limited to the above embodiment, and variations in the specific structure are permitted. Any variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0158] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method of making a composite membrane material for a flow battery, the method comprising: It comprises the following steps: Spray the ZIF-8 metal organic framework solution to the positive side of the microporous membrane, dry to obtain the flow battery composite membrane material.

2. The method of making a liquid flow battery composite membrane material of claim 1, wherein, It also comprises the following steps: V4C3T x The MXene dispersion liquid is mixed with the ZIF-8 solution and then sprayed onto the positive side of the flow battery composite membrane material and dried.

3. The method of making a liquid flow battery composite membrane material of claim 2, wherein, V4C3T x The speed of spraying the mixture of the MXene dispersion liquid and the ZIF-8 solution is 5-10 ml / min, and the spraying time is 5-10 min.

4. The method of making a liquid flow battery composite membrane material of claim 2, wherein, It also comprises the following steps: Mo2CT x MXene dispersion liquid is sprayed to V4C3T x The negative side of the flow battery composite membrane material after mixing the MXene dispersion liquid and the ZIF-8 solution is dried, wherein T is -OH and -F, and x is 1.8-2.

2.

5. The method of making a liquid flow battery composite membrane material of claim 4, wherein, Mo2CT x The concentration of the MXene dispersion liquid is 5-25 mg / mL.

6. The method of making a liquid flow battery composite membrane material of claim 4, wherein, Mo2CT x The MXene dispersion liquid was sprayed at a speed of 5-10 ml / min for 5-10 min.

7. The method of making a liquid flow battery composite membrane material of claim 1, wherein, The mass concentration of the ZIF-8 metal organic framework solution is 10%-30%.

8. The method of making a liquid flow battery composite membrane material of claim 1, wherein, The spraying speed of the ZIF-8 metal organic framework solution is 5-10ml / min, and the spraying time is 5-10min.

9. The method of making a liquid flow battery composite membrane material of claim 1, wherein, V4C3T x The concentration of the MXene dispersion liquid is 20 mg / mL, the mass concentration of the ZIF-8 solution is 10%-30%, V4C3T x The volume ratio of the MXene dispersion liquid to the ZIF-8 solution is 8:2-2:

8. 10.A flow battery composite membrane material prepared by the method according to any one of claims 1-9.

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