Alkaline zinc-iron flow battery

Abstract

The invention belongs to the field of flow batteries, and particularly relates to an alkaline zinc-iron flow battery. The alkaline zinc-iron flow battery comprises an ion conduction membrane unit, an electrolyte unit and an electrode unit, the ion conduction membrane unit is a porous ion conduction membrane with negative charge, and can quickly conduct positively charged carriers and repel negatively charged active substances; a positive electrode of the electrolyte unit is a ferricyanide couple, a negative electrode of the electrolyte unit is a zinc couple, a positive electrode supporting electrolyte is a lithium-based mixed alkali metal solution, and a negative electrode supporting electrolyte is an alkali metal solution; the positive electrode and the negative electrode of the electrode unit are both porous carbon nanosheet array modified carbon fiber electrodes, so that the concentration polarization of a positive electrode active material can be reduced, and the carbon fiber electrodes can also be used as active sites for zinc deposition of the negative electrode. The alkaline zinc-iron flow battery disclosed by the invention is excellent in performance and shows a very good application prospect.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow batteries, and in particular relates to an alkaline zinc-iron liquid flow battery. Background Art

[0002] Clean energy plays an important strategic role in the energy market. However, the intermittent and unstable nature of renewable energy sources such as wind and solar energy poses a great challenge to continuous energy supply, so efficient energy storage technology is urgently needed to improve energy utilization. Liquid flow batteries are considered to be a very promising large-scale energy storage technology because of their green, safe, long cycle life, flexible structural design and high energy conversion efficiency.

[0003] Alkaline zinc-iron flow batteries have attracted more and more attention from researchers due to their low cost and high energy density. In particular, the cost advantage is obvious, and the development cost of a kilowatt-class reactor is less than $11 / kWh. However, due to the contradiction between the rapid reaction kinetics of the positive electrode active material and the low electrolyte concentration, concentration polarization becomes the main obstacle to battery operation. China's patent "A hydrotalcite-carbon fiber electrode material and its alkaline zinc-iron flow battery", application number 202310522899.2, publication number CN116525843, discloses a hydrotalcite composite carbon felt electrode that reduces the concentration polarization on the positive electrode side and improves the performance of the alkaline zinc-iron flow battery. However, the ohmic polarization of the battery at high current density cannot be ignored. Hydrotalcite, which is essentially a semiconductor material, will significantly reduce the conductivity of the electrode and increase the ohmic impedance of the battery. Therefore, the development of high-performance electrode materials is of great significance to alkaline zinc-iron flow batteries. Summary of the invention

[0004] In view of the deficiencies in the prior art and in combination with the problem of composite electrodes being washed away by electrolyte in liquid flow batteries, the present invention prevents the carbon fiber loading material from being washed away by electrolyte and losing activity. The present invention provides a method for preparing and applying a composite electrode for an alkaline zinc-iron liquid flow battery.

[0005] The technical solution of the present invention is: The technical solution of the present invention is: An alkaline zinc-iron flow battery comprises an ion conduction membrane unit, an electrolyte unit and an electrode unit: the ion conduction membrane unit is a negatively charged porous ion conduction membrane; the electrolyte unit has a positive electrode of a ferrocyanide electrode pair, a negative electrode of a zinc electrode pair, and an alkali metal solution as a supporting electrolyte; the positive and negative electrodes of the electrode unit are both carbon fiber electrodes modified by porous carbon nanosheet arrays.

[0006] Furthermore, in the above-mentioned alkaline zinc-iron liquid flow battery, the negatively charged porous ion conductive membrane includes one of sulfonated polyetheretherketone, sulfonated polybenzimidazole, and sulfonated polyimide, and has a thickness of 80 to 120 microns.

[0007] Furthermore, in the above-mentioned alkaline zinc-iron liquid flow battery, the ratio of the ferrocyanide electrode concentration to the zinc electrode concentration is 2:1.

[0008] Furthermore, in the above alkaline zinc-iron flow battery, the supporting electrolyte positive electrode is a mixed solution of lithium hydroxide and potassium hydroxide (sodium hydroxide) in a ratio of 1:1 and a concentration of 1 mol L -1 The negative electrode is one of potassium hydroxide and sodium hydroxide, with a concentration of 1 mol L -1 .

[0009] Furthermore, in the above-mentioned alkaline zinc-iron liquid flow battery, the thickness of the porous carbon nanosheet array is 50 to 150 nanometers.

[0010] Furthermore, in the above-mentioned alkaline zinc-iron liquid flow battery, the carbon fiber electrode is one of graphite felt, carbon cloth, and carbon paper.

[0011] Furthermore, in the above-mentioned alkaline zinc-iron liquid flow battery, the carbon fiber electrode has a porosity of 60-90% and a thickness of 2-3 microns.

[0012] Advantages and beneficial effects of the present invention: 1. The negatively charged porous ion conductive membrane can quickly conduct positively charged carriers and repel negatively charged active substances, thereby improving battery efficiency while preventing dendrites generated by negative electrode active substances from piercing the ion conductive membrane and causing battery short circuit; 2. The positive electrode supporting electrolyte of the electrolyte unit is a lithium-based mixed alkali metal solution, which effectively reduces the polarization of ferrocyanide; 3. The positive and negative electrodes of the electrode unit are both carbon fiber electrodes modified by porous carbon nanosheet arrays, which can not only reduce the concentration polarization of the positive electrode active material, but also serve as active sites for the deposition of negative electrode zinc. The alkaline zinc-iron flow battery of the present invention has excellent performance and shows very good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a scanning electron microscope image of the composite electrode obtained in Example 1. DETAILED DESCRIPTION

[0014] The specific implementation modes of the present invention are further described in detail below in conjunction with examples and comparative examples. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention.

[0015] Example 1

[0016] This embodiment is an alkaline zinc-iron flow battery, comprising an ion conduction membrane unit, an electrolyte unit and an electrode unit: The ion conducting membrane unit is a negatively charged porous ion conducting membrane; The electrolyte unit has a positive electrode of ferrocyanide electrode pair, a negative electrode of zinc electrode pair, and an alkali metal solution as a supporting electrolyte; The positive and negative electrodes of the electrode unit are both 4×7 cm in size. 2 The porous carbon nanosheet array modified carbon felt electrode (thickness 2 mm) was used as the electrode material. Figure 1 The electrode shown is a microscopic morphology of a carbon felt electrode modified by a porous carbon nanosheet array. The ion-conducting membrane is a sulfonated polybenzimidazole porous membrane, and the positive electrode electrolyte is 0.6 mol L -1 Na4Fe(CN)6+1mol L -1 KOH / LiOH, negative electrode electrolyte is 0.3 mol L -1 Na2Zn(OH)4+1 mol L -1 NaOH.

[0017] The alkaline zinc-iron flow battery assembled in this example has a current of 80 mAcm -2 、150 mAcm -2 , 250 mA cm -2 、320mA cm -2 At the current density, the battery voltage efficiency was 94.1%, 90.8%, 86.0% and 79.1% respectively.

[0018] Example 2

[0019] This embodiment is an alkaline zinc-iron flow battery, comprising an ion conduction membrane unit, an electrolyte unit and an electrode unit: The ion conducting membrane unit is a negatively charged porous ion conducting membrane; The electrolyte unit has a positive electrode of ferrocyanide electrode pair, a negative electrode of zinc electrode pair, and an alkali metal solution as a supporting electrolyte; The positive and negative electrodes of the electrode unit are both 4×7 cm in size. 2 The porous carbon nanosheet array modified carbon felt electrode (thickness 2.5 mm) was used as the electrode material. Figure 1 The electrode shown is the microscopic morphology of a carbon felt electrode modified by a porous carbon nanosheet array. The ion-conducting membrane is a sulfonated polyetheretherketone porous membrane, and the positive electrode electrolyte is 0.8 mol L -1 Na4Fe(CN)6+1mol L -1 KOH / LiOH, negative electrode electrolyte is 0.4 mol L -1 Na2Zn(OH)4+1 mol L -1 NaOH.

[0020] The alkaline zinc-iron flow battery assembled in this example has a current of 80 mAcm -2、150 mAcm -2 , 250 mA cm -2 、320mA cm -2 At the current density, the battery voltage efficiency was 92.5%, 88.7%, 84.2% and 78.3% respectively.

[0021] Example 3

[0022] This embodiment is an alkaline zinc-iron flow battery, comprising an ion conduction membrane unit, an electrolyte unit and an electrode unit: The ion conducting membrane unit is a negatively charged porous ion conducting membrane; The electrolyte unit has a positive electrode of ferrocyanide electrode pair, a negative electrode of zinc electrode pair, and an alkali metal solution as a supporting electrolyte; The positive and negative electrodes of the electrode unit are both 4×7 cm in size. 2 The porous carbon nanosheet array modified carbon felt electrode (thickness 2.3 mm) was used as the electrode material. Figure 1 The electrode shown is a microscopic morphology of a carbon felt electrode modified by a porous carbon nanosheet array. The ion-conducting membrane is a sulfonated polyimide porous membrane, and the positive electrode electrolyte is 0.4 mol L -1 Na4Fe(CN)6+1mol L -1 KOH / LiOH, negative electrode electrolyte is 0.2 mol L -1 Na2Zn(OH)4+1 mol L -1 NaOH.

[0023] The alkaline zinc-iron flow battery assembled in this example has a current of 80 mAcm -2 、150 mAcm -2 , 250 mA cm -2 、320mA cm -2 At the current density, the battery voltage efficiency was 92.9%, 89.6%, 85.0% and 78.9% respectively.

[0024] The above embodiments show that the alkaline zinc-iron flow battery of the present design coordinates the comprehensive effects of key components, effectively reduces the concentration polarization of the positive electrode of the alkaline zinc-iron flow battery, reduces the internal resistance of the battery, and significantly improves the battery performance.

[0025] All the above embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. Any form of equivalent replacement or equivalent transformation is within the protection scope of the present invention.

Claims

1. An alkaline zinc-iron flow battery, characterized in that: It includes an ion conduction membrane unit, an electrolyte unit and an electrode unit: the ion conduction membrane unit is a negatively charged porous ion conduction membrane; the electrolyte unit has a positive electrode of a ferrocyanide electrode pair, a negative electrode of a zinc electrode pair, and an alkali metal solution as a supporting electrolyte; the positive and negative electrodes of the electrode unit are both carbon fiber electrodes modified by porous carbon nanosheet arrays.

2. An alkaline zinc-iron flow battery according to claim 1, characterized in that: The negatively charged porous ion conducting membrane comprises one of sulfonated polyetheretherketone, sulfonated polybenzimidazole and sulfonated polyimide, and has a thickness of 80 to 120 microns.

3. An alkaline zinc-iron flow battery according to claim 1, characterized in that: The ratio of the ferrocyanide electrode concentration to the zinc electrode concentration is 2:

1.

4. An alkaline zinc-iron flow battery according to claim 1, characterized in that: The supporting electrolyte positive electrode is a mixed solution of lithium hydroxide and potassium hydroxide or sodium hydroxide in a ratio of 1:1 and a concentration of 1 mol L -1 The negative electrode is one of potassium hydroxide and sodium hydroxide, with a concentration of 1 mol L -1 .

5. The alkaline zinc-iron flow battery according to claim 1, characterized in that: The thickness of the porous carbon nanosheet array is 50-150 nanometers.

6. An alkaline zinc-iron flow battery according to claim 1, characterized in that: The carbon fiber electrode is one of graphite felt, carbon cloth and carbon paper.

7. An alkaline zinc-iron flow battery according to claim 1, characterized in that: The carbon fiber electrode has a porosity of 60-90% and a thickness of 2-3 microns.

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