Binder-assisted metal catalyst modified electrode material and preparation method and application thereof

Abstract

The invention relates to a binder-assisted metal catalyst modified electrode material and a preparation method and application thereof.The binder-assisted metal catalyst modified electrode material comprises a modified graphite felt and a metal catalyst loaded on the modified graphite felt, and the modified graphite felt and the metal catalyst are connected through a binder; the chemical structural formula of the binder contains polar groups; the modified graphite felt contains oxygen-containing functional groups. The binding agent provided by the invention assists a metal catalyst modified electrode material to improve the electrochemical activity of a chromium ion pair, so that the energy efficiency and the voltage efficiency of the iron-chromium flow battery are improved. The introduction of the binder not only can fix the catalyst, but also can enhance the mechanical strength of the graphite felt, reduce fiber fracture or shedding in the circulation process, and prolong the service life of the electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow battery energy storage technology, and in particular to a binder-assisted metal catalyst modified electrode material, a preparation method thereof, and uses thereof. Background Art

[0002] With the continuous advancement of science and technology, humanity's demand for energy is constantly increasing. Accelerating the development of clean, low-carbon, renewable energy is imperative. However, in the process of promoting resource transformation, renewable energy sources such as wind power and photovoltaics, due to their inherent characteristics such as indirectness and volatility, pose significant challenges to the stable operation of the power system. Therefore, the development of large-scale, long-duration energy storage technology has become key to absorbing renewable energy and regulating grid peak loads. Traditional energy storage technologies, such as lithium-ion batteries, are difficult to implement due to their high cost, short lifespan, and suitability for only short-term frequency regulation. Pumped hydropower storage is also difficult to implement due to geographical constraints, long construction cycles, and significant ecological impacts. In recent years, researchers have proposed using flow batteries to address the problem of sustainable power generation from renewable energy sources.

[0003] At present, all-vanadium liquid flow battery is a relatively mature energy storage technology in commercialization, but it still has problems such as high cost and limited resources. In contrast, iron-chromium liquid flow battery has obvious advantages in terms of material cost and resource availability. However, its large-scale commercial application still faces the problem of negative electrode Cr 3+ / Cr 2+ The ion pairs have poor redox kinetics and are prone to hydrogen evolution side reactions, which not only leads to a decrease in the coulombic efficiency of the battery, but also causes the battery capacity to decay too quickly and the cycle stability to be poor.

[0004] To address these issues, researchers have focused on modifying the electrolyte, membrane, and electrodes. As one of the key materials in flow batteries, electrodes have become the first choice for improving battery performance.

[0005] In the prior art, graphite felt is usually used as the electrode material of iron-chromium flow batteries because of its low cost, good chemical stability and good reaction activity in iron-chromium flow batteries. However, the unmodified graphite felt has poor electrolyte wettability and lacks catalytic active sites on the surface, which leads to the Cr 3+ / Cr 2+ The ions have poor redox reaction activity and poor mechanical strength, which may cause corrosion and breakage of graphite fibers during long cycles.

[0006] Based on the above defects, how to develop an effective method to enhance the negative electrode Cr 3+ / Cr 2+The electrode materials and preparation methods for improving the reactivity of ion pairs to improve the energy efficiency, voltage efficiency, service life and cycle stability of iron-chromium flow batteries have become urgent issues to be solved. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention aims to provide a binder-assisted metal catalyst modified electrode material and its preparation method and use. The binder-assisted metal catalyst modified electrode material of the present invention effectively enhances the negative electrode Cr 3+ / Cr 2+ The reactivity of ion pairs improves the energy efficiency and voltage efficiency of the iron-chromium flow battery. At the same time, it alleviates the fiber breakage of the graphite felt electrode during the cycle, extends the service life of the electrode, and thus improves the cycle stability of the battery.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a binder-assisted metal catalyst modified electrode material, wherein the binder-assisted metal catalyst modified electrode material includes a modified graphite felt and a metal catalyst loaded on the modified graphite felt, wherein the modified graphite felt and the metal catalyst are connected by a binder; the chemical structure of the binder contains a polar group; and the modified graphite felt contains an oxygen-containing functional group.

[0010] The present invention adopts modified graphite felt containing oxygen-containing functional groups to improve the wettability of graphite felt electrode to electrolyte; introduces metal catalyst to improve Cr 3+ / Cr 2+ The reactivity of ion pairs improves the energy efficiency and voltage efficiency of iron-chromium flow batteries. However, as iron-chromium flow batteries operate over long cycles, the metal catalyst will fall off, battery performance will decline, and the graphite felt itself will corrode and break, shortening the service life of the electrodes.

[0011] To this end, the present invention also prevents the metal catalyst from falling off by introducing a binder containing polar groups. Properly introducing the binder into the surface of the graphite felt can not only fix the catalyst, but also the oxygen-containing functional groups contained in the modified graphite felt can combine with the polar groups in the binder, so that the binder can adhere firmly to the surface of the graphite felt; on the other hand, the binder can also enhance the mechanical strength of the graphite felt to extend the service life of the electrode, thereby improving the cycle stability of the iron-chromium liquid flow battery.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] Preferably, the binder includes any one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyacrylonitrile (PAN) or polyacrylic acid (PAA) or a combination of at least two thereof. Typical but non-limiting combinations include a combination of PVDF and PVA, a combination of PVA and PVB, a combination of PVB and PAN, a combination of PAN, PAA and PAN, a combination of PVDF, PVA and PVB, a combination of PVDF and PVB, or a combination of PVDF, PAN and PAA, preferably PVDF.

[0014] The binder selected in the present invention contains polar groups such as vinylidene fluoride monomer (-CH2-CF2-), hydroxyl group (-OH), ether bond (-O-), cyano group (-C≡N), and carboxyl group (-COOH), and is further preferably polyvinylidene fluoride (PVDF), wherein the vinylidene fluoride monomer (-CH2-CF2-) in the PVDF molecular chain is polar and is adsorbed on the surface of the modified graphite felt through the adsorption effect between the polar groups, thereby improving its adhesion to the modified graphite felt; at the same time, PVDF can also enhance the mechanical strength of the modified graphite felt, alleviate the fiber breakage of the graphite felt electrode during the cycle, and extend the service life of the electrode.

[0015] Preferably, the oxygen-containing functional groups include carboxyl and / or hydroxyl groups.

[0016] Preferably, the metal catalyst comprises any one of bismuth nitrate, bismuth chloride, bismuth sulfate, lead nitrate, lead chloride, tin nitrate, tin chloride, tin sulfate, stannous chloride, stannous sulfate or indium chloride, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of bismuth nitrate and bismuth chloride, a combination of lead nitrate and lead chloride, a combination of tin nitrate and tin chloride, a combination of stannous chloride and stannous sulfate, a combination of bismuth nitrate, bismuth chloride and bismuth sulfate, a combination of tin nitrate, tin chloride, tin sulfate, stannous chloride and stannous sulfate, or a combination of stannous chloride, stannous sulfate and indium chloride, preferably bismuth nitrate.

[0017] The preferred metal catalyst of the present invention is bismuth nitrate, which is more conducive to increasing the Cr 3+ / Cr 2+ The reactivity of ion pairs can improve the energy efficiency and voltage efficiency of iron-chromium flow batteries.

[0018] Preferably, the loading amount of the metal catalyst on the binder-assisted metal catalyst modified electrode material is 0.01 mmol / cm 2 -0.1mmol / cm 2 , for example, it can be 0.01mmol / cm 2 , 0.02mmol / cm 2 , 0.03mmol / cm2 , 0.04mmol / cm 2 , 0.05mmol / cm 2 、0.06mmol / cm 2 , 0.07mmol / cm 2 , 0.08mmol / cm 2 、0.09mmol / cm 2 or 0.1mmol / cm 2 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0019] In a second aspect, the present invention provides a method for preparing a binder-assisted metal catalyst-modified electrode material as described in the first aspect, the preparation method comprising the following steps:

[0020] (1) immersing the modified graphite felt in a binder solution, ultrasonicating, and drying to obtain pretreated graphite felt;

[0021] (2) Immersing the pretreated graphite felt in a metal catalyst solution, subjecting it to a hydrothermal reaction and drying, thereby obtaining a binder-assisted metal catalyst-modified electrode material.

[0022] The electrode material preparation method provided by the present invention is simple to operate, has controllable reaction conditions, and is suitable for large-scale industrial production. Furthermore, the modified graphite felt exhibits high energy and voltage efficiency and good cycling stability. Loading the metal catalyst on the graphite felt enhances the electrochemical activity of chromium ion pairs, thereby improving the energy and voltage efficiency of iron-chromium redox flow batteries.

[0023] Preferably, the method for obtaining modified graphite felt in step (1) comprises: immersing the graphite felt in an acid solution for acid treatment, and drying to obtain the modified graphite felt.

[0024] The acid treatment in the present invention is to subject the cleaned graphite felt electrode to a chemical impregnation process with an acid solution to increase oxygen-containing functional groups and obtain modified graphite felt.

[0025] Preferably, before immersing the graphite felt in the acid solution, the graphite felt is ultrasonically cleaned and dried to remove impurities and dust on the surface of the graphite felt.

[0026] The drying and baking methods described in the present invention all adopt conventional drying technology, the purpose of which is to remove the solvent during the cleaning process.

[0027] Preferably, the solvent used in the ultrasonic cleaning includes water and / or ethanol.

[0028] Preferably, the acid solution comprises any one of nitric acid, sulfuric acid or phosphoric acid, or a combination of at least two thereof, preferably nitric acid.

[0029] The present invention further preferably uses nitric acid, the oxidizing property of nitric acid reacts with the graphite felt to produce an oxidation reaction, thereby introducing a plurality of oxygen-containing functional groups such as carboxyl (-COOH) and carbonyl (C=O) on the surface of the graphite felt. The oxygen-containing functional groups combine with the polar groups in the binder in step (2), which not only avoids the phenomenon of the binder agglomerating due to excessively high local load concentration, but also increases the bonding performance of the binder on the surface of the graphite felt.

[0030] Preferably, the concentration of the acid solution is 1 mol / L-6 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, or 6 mol / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3 mol / L-5 mol / L.

[0031] Preferably, the acid treatment time is 4h-12h, for example, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 8h-10h.

[0032] Preferably, the concentration of the binder solution in step (1) is 5 mg / mL-20 mg / mL, for example, it can be 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL or 20 mg / mL, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 10 mg / mL-15 mg / mL.

[0033] Preferably, the ultrasonic time is 5 min-20 min, for example, 5 min, 8 min, 10 min, 15 min, 18 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 5 min-10 min.

[0034] The present invention further controls the concentration of the binder solution and the ultrasonic time. If the concentration of the binder solution is too high, it is easy to clog the pores of the modified graphite felt, affecting the transmission of electrolyte ions and thus affecting battery performance. In addition, the lack of conductivity of PVDF will affect the conductivity of the graphite felt electrode. If the concentration of the binder solution is too low, the loading amount of PVDF is small, which is not conducive to the subsequent adhesion of metal ions to the graphite felt.

[0035] Preferably, the concentration of the metal catalyst solution in step (2) is 0.01mol / L-0.05mol / L, for example, it can be 0.01mol / L, 0.018mol / L, 0.02mol / L, 0.025mol / L, 0.03mol / L, 0.035mol / L, 0.04mol / L, 0.045mol / L or 0.05mol / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.015mol / L-0.035mol / L.

[0036] Preferably, the hydrothermal reaction of the present invention can be carried out in a homogeneous reactor.

[0037] Preferably, the temperature of the hydrothermal reaction is 120°C-180°C, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 150°C-180°C.

[0038] The present invention further controls the temperature of the hydrothermal reaction to be 120°C-180°C. The reaction temperature has an impact on the modification of the electrode material: if the temperature is too high (>200°C), the internal structure of the selected binder may be destroyed, thereby affecting the stability of the prepared electrode material; if the temperature is too low, the reaction rate of the metal catalyst is slow, resulting in poor loading effect, which will affect the performance of the electrode modification.

[0039] Preferably, the hydrothermal reaction time is 1 h-12 h, for example, it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 8 h-12 h.

[0040] Preferably, step (1) and step (2) further include washing the graphite felt with water after impregnation and before drying.

[0041] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0042] (I) ultrasonically cleaning the graphite felt using water and / or ethanol, drying the graphite felt, immersing the graphite felt in an acid solution having a concentration of 1 mol / L to 6 mol / L for 4 to 12 hours, performing an acid treatment, and drying the graphite felt to obtain a modified graphite felt;

[0043] (II) immersing the modified graphite felt in a binder solution with a concentration of 5 mg / mL to 20 mg / mL, ultrasonically treating the graphite felt for 5 min to 20 min, washing the graphite felt with water, and drying the graphite felt to obtain a pretreated graphite felt;

[0044] (III) Immersing the pretreated graphite felt in a metal catalyst solution having a concentration of 0.01 mol / L-0.05 mol / L, hydrothermally reacting the solution at 120° C.-180° C. for 1 h-12 h, washing the graphite felt with water, and drying the solution to obtain a binder-assisted metal catalyst-modified electrode material.

[0045] In a third aspect, the present invention provides a use of a binder-assisted metal catalyst-modified electrode material as described in the first aspect, wherein the binder-assisted metal catalyst-modified electrode material is used for an iron-chromium redox flow battery electrode.

[0046] The iron-chromium flow battery electrode provided by the present invention adopts a binder to assist the metal catalyst to modify the electrode material, so that the metal catalyst is not easy to fall off from the surface of the graphite felt, thereby promoting the metal catalyst to play a role in the long cycle process of the battery, thereby improving the Cr 3+ / Cr 2+ The ion pairs are active in redox reactions, which alleviates capacity fade, improves energy efficiency and voltage efficiency, and also improves cycle stability.

[0047] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The present invention prevents the metal catalyst from falling off by introducing a binder containing polar groups. The oxygen-containing functional groups in the modified graphite felt can combine with the polar groups in the binder, thereby firmly adhering the binder to the surface of the graphite felt. Properly introducing the binder to the surface of the graphite felt not only fixes the catalyst but also enhances the mechanical strength of the graphite felt, thereby extending the service life of the electrode and improving the cycling stability of the iron-chromium flow battery.

[0050] (2) The preparation method of the electrode material provided by the present invention is simple to operate, the reaction conditions are controllable, and it is suitable for large-scale industrial production. In addition, the obtained electrode material exhibits high energy efficiency, voltage efficiency and good cycle stability.

[0051] (3) The iron-chromium flow battery electrode provided by the present invention adopts a binder to assist the metal catalyst to modify the electrode material, so that the metal catalyst is not easy to fall off from the surface of the graphite felt, thereby promoting the metal catalyst to play a role in the long cycle of the battery, thereby improving the Cr 3+ / Cr 2+ Ion pairs redox reaction activity, alleviate capacity fading, improve energy efficiency, voltage efficiency and cycle stability. 2 When tested under current density, the coulombic efficiency reached 98.2%, the voltage efficiency reached 83.9%, the energy efficiency reached 82.4%, and the 50-cycle capacity retention rate reached 89.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a process flow chart of the modified electrode preparation method provided in Example 1 of the present invention;

[0053] Figure 2 3 is a comparison chart of the energy efficiency of the electrode materials obtained in Example 1 of the present invention and Comparative Examples 1, 2, and 3;

[0054] Figure 3 1 is a comparison chart of the coulombic efficiencies of the electrode materials obtained in Example 1 of the present invention and Comparative Examples 1, 2, and 3;

[0055] Figure 4 This is a comparison chart of the voltage efficiency of the electrode materials obtained in Example 1 of the present invention and Comparative Examples 1, 2, and 3. DETAILED DESCRIPTION

[0056] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0057] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0058] Example 1

[0059] This embodiment provides a binder-assisted metal catalyst modified electrode material, the binder-assisted metal catalyst modified electrode material comprising a modified graphite felt and a bismuth nitrate metal catalyst supported on the modified graphite felt, wherein the modified graphite felt and the metal catalyst are connected via a polyvinylidene fluoride binder;

[0060] The loading of bismuth nitrate on the binder-assisted metal catalyst modified electrode material is 0.056 mmol / cm2 .

[0061] The preparation flow chart of the binder-assisted metal catalyst modified electrode material provided in this embodiment is as follows: Figure 1 As shown, the specific preparation method comprises the following steps:

[0062] (Ⅰ) Use water and ethanol to 2 ×4cm 2 The graphite felt was ultrasonically cleaned and dried, and then immersed in 3 mol / L nitric acid for 10 h for acid treatment, and then dried to obtain modified graphite felt;

[0063] (II) immersing the modified graphite felt in a 10 mg / mL PVDF solution (solvent: NMP), ultrasonicating for 10 min, washing the graphite felt with water, and drying to obtain pretreated graphite felt;

[0064] (III) Immersing the pretreated graphite felt in a 0.03 mol / L bismuth nitrate solution, hydrothermally reacting it at 180° C. for 8 h, cooling it to room temperature, removing the graphite felt, washing it several times with water, and drying it to obtain a binder-assisted metal catalyst modified electrode material.

[0065] Example 2

[0066] This embodiment provides a binder-assisted metal catalyst modified electrode material, the binder-assisted metal catalyst modified electrode material comprising a modified graphite felt and a lead nitrate metal catalyst supported on the modified graphite felt, wherein the modified graphite felt and the metal catalyst are connected via a polyvinyl alcohol binder;

[0067] The loading of lead nitrate on the binder-assisted metal catalyst modified electrode material is 0.0375mmol / cm 2 .

[0068] The preparation method of the binder-assisted metal catalyst modified electrode material provided in this embodiment includes the following steps:

[0069] (Ⅰ) Use water and ethanol to 2 ×4cm 2 The graphite felt was ultrasonically cleaned and dried, and then immersed in 1 mol / L sulfuric acid for 12 h for acid treatment, and then dried to obtain modified graphite felt;

[0070] (II) immersing the modified graphite felt in a 5 mg / mL PVA solution (solvent: water), ultrasonically treating the graphite felt for 10 min, washing the graphite felt with water, and drying the graphite felt to obtain pretreated graphite felt;

[0071] (III) Immersing the pretreated graphite felt in a 0.02 mol / L lead nitrate solution, hydrothermally reacting it at 120° C. for 12 h, cooling it to room temperature, removing the graphite felt, washing it several times with water, and drying it to obtain a binder-assisted metal catalyst modified electrode material.

[0072] Example 3

[0073] This embodiment provides a binder-assisted metal catalyst-modified electrode material, which includes a modified graphite felt and a tin sulfate metal catalyst supported on the modified graphite felt, wherein the modified graphite felt and the metal catalyst are connected via a mixed binder of polyvinylidene fluoride and polyacrylonitrile;

[0074] The loading of tin sulfate on the binder-assisted metal catalyst modified electrode material is 0.094 mmol / cm 2 .

[0075] The preparation method of the binder-assisted metal catalyst modified electrode material provided in this embodiment includes the following steps:

[0076] (Ⅰ) Use water and ethanol to 2 ×4cm 2 The graphite felt was ultrasonically cleaned, dried, immersed in 5 mol / L nitric acid for 5 h, subjected to acid treatment, and dried to obtain modified graphite felt;

[0077] (II) The modified graphite felt was immersed in a 20 mg / mL PVDF and PAN solution (PVDF and PAN mass ratio was 7:3, and the solvent was NMP), ultrasonicated for 20 min, and then the graphite felt was washed with water and dried to obtain the pretreated graphite felt;

[0078] (III) Immersing the pretreated graphite felt in a 0.05 mol / L tin sulfate solution, hydrothermally reacting it at 160° C. for 10 h, cooling it to room temperature, removing the graphite felt, washing it several times with water, and drying it to obtain a binder-assisted metal catalyst modified electrode material.

[0079] Example 4

[0080] The only difference between this embodiment and embodiment 1 is that the mass concentration of PVDF in step (II) is 2 mg / mL, and the rest is the same as embodiment 1.

[0081] Example 5

[0082] The only difference between this embodiment and embodiment 1 is that the mass concentration of PVDF in step (II) is 25 mg / mL, and the rest is the same as embodiment 1.

[0083] Example 6

[0084] The only difference between this embodiment and embodiment 1 is that the ultrasonic immersion time of PVDF in step (II) is 2 minutes, and the rest is the same as embodiment 1.

[0085] Example 7

[0086] The only difference between this embodiment and embodiment 1 is that the ultrasonic immersion time of PVDF in step (II) is 30 minutes, and the rest is the same as embodiment 1.

[0087] Example 8

[0088] The only difference between this embodiment and Example 1 is that the concentration of bismuth nitrate in step (III) is 0.005 mol / L, and the rest is the same as Example 1.

[0089] Example 9

[0090] The only difference between this embodiment and Example 1 is that the concentration of bismuth nitrate in step (III) is 0.1 mol / L, and the rest is the same as Example 1.

[0091] Example 10

[0092] The only difference between this embodiment and embodiment 1 is that the temperature of the hydrothermal reaction in step (III) is 100° C., and the rest is the same as embodiment 1.

[0093] Example 11

[0094] The only difference between this embodiment and embodiment 1 is that the temperature of the hydrothermal reaction in step (III) is 200° C., and the rest is the same as embodiment 1.

[0095] Example 12

[0096] The only difference between this embodiment and embodiment 1 is that the time of the hydrothermal reaction in step (III) is 0.5 h, and the rest is the same as embodiment 1.

[0097] Example 13

[0098] The only difference between this embodiment and embodiment 1 is that the time of the hydrothermal reaction in step (III) is 15 h, and the rest is the same as embodiment 1.

[0099] Comparative Example 1

[0100] This comparative example provides an electrode material, which differs from Example 1 in that, when preparing the electrode material, only the graphite felt is ultrasonically cleaned and dried, without acid treatment, and without the introduction of a binder and a metal catalyst, i.e., steps (II) and (III) are not performed.

[0101] Comparative Example 2

[0102] This comparative example provides an electrode material, which differs from Example 1 in that no binder is introduced when preparing the electrode material, that is, step (II) does not involve soaking in a PVDF solution.

[0103] Comparative Example 3

[0104] This comparative example provides an electrode material, which differs from Example 1 in that, when preparing the electrode material, no acid treatment is performed, that is, step (I) does not involve soaking in an acid solution.

[0105] The modified graphite felts of Examples 1-13 and Comparative Examples 1-3 were applied to an iron-chromium flow battery. A single cell stack with a neutral energy storage rated power of 3W was selected. The size of the cell stack was 12×15×8 cm. 3 , the size of the electrode is 4cm×4cm.

[0106] The single-cell test setup is as follows: A single-cell test system is assembled, including a stack, two electrolyte tanks, and two peristaltic pumps. The stack structure, from the outside in, consists of end plates, gaskets, copper plates, washers, graphite plates, gaskets, graphite electrodes, and an ion exchange membrane. The single-cell operating temperature is 65°C.

[0107] The positive and negative electrolytes are prepared as follows: 1.0 mol / L ferrous chloride, 1.0 mol / L chromium chloride, and 3 mol / L hydrochloric acid. Each electrolyte tank contains 100 ml of electrolyte.

[0108] Test standard: The voltage range of the charge and discharge test of the LAND test system is 0.7V-1.2V, and the current density is 100mA / cm 2 The battery capacity test and battery energy efficiency test of the iron-chromium flow battery were carried out at different charge and discharge cycle times. The test results are shown in Table 1. Figure 2 、 Figure 3 and Figure 4 shown.

[0109] pass Figure 2 、 Figure 3 and Figure 4 It can be seen that the voltage efficiency, energy efficiency and cycle performance of the iron-chromium flow battery provided in Example 1 of the present invention are significantly higher than those in Comparative Example 1 and Comparative Example 2, indicating that the synergistic effect of the binder-assisted catalyst can significantly improve the battery performance.

[0110] Table 1

[0111]

[0112]

[0113] The test results show that:

[0114] (1) It can be seen from Examples 1 to 3 that the voltage efficiency, energy efficiency and capacity retention rate of the binder-assisted metal catalyst modified electrode material provided by the present invention are improved after the single cell cycle test. The addition of metal catalysts can increase the electrochemical activity of chromium ions, reduce the influence of electrode polarization, and improve voltage efficiency and energy efficiency. The introduction of the binder makes it difficult for the metal catalyst to fall off the surface of the graphite felt. At the same time, it can also enhance the mechanical strength of the graphite felt, reduce fiber breakage during the cycle, and extend the service life of the electrode.

[0115] (2) By comparing Example 1 with Examples 4-5, it can be seen that the present invention strictly controls the content of the binder by adjusting the binder loading and ultrasonic time. In particular, when the binder content is too high, the conductivity of the graphite felt may be reduced, and the gaps in the graphite felt may be blocked, affecting the transmission of electrolyte ions and thus affecting the battery performance.

[0116] (3) By comparing Example 1 with Examples 6 to 13, it can be seen that the amount of catalyst added in the present invention affects the test performance of the single cell. The optimal loading content can be achieved by further adjusting the concentration of the catalyst, the temperature and time of the hydrothermal reaction.

[0117] (4) It can be seen from Example 1 and Comparative Example 1 that, compared with the original graphite felt, the binder-assisted metal catalyst modified electrode material provided by the present invention can promote the metal catalyst to play a role in the long cycle process of the battery, thereby improving the Cr 3+ / Cr 2+ Ion pair redox reaction activity can improve energy efficiency and voltage efficiency in battery cycling tests.

[0118] (5) It can be seen from Example 1 and Comparative Example 2 that if only catalyst is added, although the Cr 3+ / Cr 2+ The reactivity of ion pairs increases the battery voltage efficiency and energy efficiency, but as the battery cycles, some of the loaded catalyst will fall off, causing the capacity to decay faster. Therefore, the appropriate introduction of a binder can slow down the detachment of the catalyst from the graphite felt surface, assist the catalyst in exerting its effect, prolong the catalytic reaction time of the catalyst on the electrode surface, and alleviate the battery's capacity decay.

[0119] (6) As can be seen from Example 1 and Comparative Example 3, the present invention can improve the adhesion strength between the binder and the graphite felt by acid-treating the graphite felt to introduce oxygen-containing functional groups, and make the distribution more uniform, thereby increasing the service life of the graphite felt. When no acid treatment is performed, the performance of the battery is improved, but the hydrophilicity of the graphite felt surface is poor, and the PVDF solution has poor wettability, which causes the PVDF to directly adhere to the graphite felt surface and distribute unevenly, thus failing to effectively alleviate capacity decay and improve battery performance.

[0120] In summary, the present invention, by acid-treating graphite felt and adding a metal catalyst and a binder to the graphite felt, obtains a binder-assisted metal catalyst-modified electrode material, which has significantly improved voltage efficiency, energy efficiency, and capacity retention after single-cell cycle testing. Among them, the metal catalyst can increase the electrochemical activity of chromium ions, reduce the influence of electrode polarization, and improve voltage efficiency and energy efficiency. The introduction of the binder makes it difficult for the metal catalyst to fall off the surface of the graphite felt, while also enhancing the mechanical strength of the graphite felt, reducing fiber breakage during the cycle, and extending the service life of the electrode.

[0121] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A binder-assisted metal catalyst modified electrode material, characterized in that: The binder-assisted metal catalyst modified electrode material includes modified graphite felt and a metal catalyst supported on the modified graphite felt, wherein the modified graphite felt and the metal catalyst are connected via a binder; The chemical structural formula of the binder contains polar groups; and the modified graphite felt contains oxygen-containing functional groups.

2. The binder-assisted metal catalyst modified electrode material according to claim 1, characterized in that: The binder comprises any one of polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, polyacrylonitrile or polyacrylic acid, or a combination of at least two thereof; Preferably, the oxygen-containing functional groups include carboxyl and / or hydroxyl groups; Preferably, the metal catalyst comprises any one or a combination of at least two of bismuth nitrate, bismuth chloride, bismuth sulfate, lead nitrate, lead chloride, tin nitrate, tin chloride, tin sulfate, stannous chloride, stannous sulfate or indium chloride; Preferably, the loading amount of the metal catalyst on the binder-assisted metal catalyst modified electrode material is 0.01 mmol / cm 2 -0.1mmol / cm 2 .

3. A method for preparing a binder-assisted metal catalyst-modified electrode material according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) immersing the modified graphite felt in a binder solution, ultrasonicating, and drying to obtain pretreated graphite felt; (2) Immersing the pretreated graphite felt in a metal catalyst solution, subjecting it to a hydrothermal reaction and drying, thereby obtaining a binder-assisted metal catalyst-modified electrode material.

4. The preparation method according to claim 3, characterized in that The method for obtaining modified graphite felt in step (1) comprises: The graphite felt is immersed in an acid solution for acid treatment, and then dried to obtain modified graphite felt; Preferably, the graphite felt is ultrasonically cleaned and dried before being immersed in the acid solution; Preferably, the solvent used in the ultrasonic cleaning includes water and / or ethanol.

5. The preparation method according to claim 4, characterized in that The acid solution comprises any one of nitric acid, sulfuric acid or phosphoric acid or a combination of at least two thereof, preferably nitric acid; Preferably, the concentration of the acid solution is 1 mol / L-6 mol / L, preferably 3 mol / L-5 mol / L; Preferably, the acid treatment time is 4 h to 12 h, preferably 8 h to 10 h.

6. The preparation method according to any one of claims 3 to 5, characterized in that The concentration of the binder solution in step (1) is 5 mg / mL-20 mg / mL, preferably 10 mg / mL-15 mg / mL; Preferably, the ultrasonication time is 5 min-20 min, preferably 5 min-10 min.

7. The preparation method according to any one of claims 3 to 6, characterized in that The concentration of the metal catalyst solution in step (2) is 0.01 mol / L-0.05 mol / L, preferably 0.015 mol / L-0.035 mol / L.

8. The preparation method according to any one of claims 3 to 7, characterized in that The temperature of the hydrothermal reaction is 120°C-180°C, preferably 150°C-180°C; Preferably, the hydrothermal reaction time is 1 h-12 h, preferably 8 h-12 h.

9. The preparation method according to any one of claims 3 to 8, characterized in that The preparation method comprises the following steps: (I) ultrasonically cleaning the graphite felt with water and / or ethanol, drying the graphite felt, immersing the graphite felt in an acid solution with a concentration of 3 mol / L to 5 mol / L for 8 h to 10 h, performing acid treatment, and drying the graphite felt to obtain a modified graphite felt; (II) immersing the modified graphite felt in a binder solution with a concentration of 10 mg / mL to 15 mg / mL, ultrasonically treating the graphite felt for 5 min to 10 min, washing the graphite felt with water, and drying the graphite felt to obtain a pretreated graphite felt; (III) Immersing the pretreated graphite felt in a metal catalyst solution having a concentration of 0.015 mol / L-0.035 mol / L, hydrothermally reacting the solution at 150° C.-180° C. for 8 h-12 h, washing the graphite felt with water, and drying the solution to obtain a binder-assisted metal catalyst-modified electrode material.

10. A use of a binder-assisted metal catalyst to modify an electrode material as claimed in claim 1 or 2, characterized in that: The binder-assisted metal catalyst modified electrode material is used for iron-chromium redox flow battery electrodes.

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