An alkaline zinc-iron flow battery

Abstract

The invention discloses an alkaline zinc-iron liquid flow battery, which belongs to the technical field of liquid flow batteries. The alkaline zinc-iron liquid flow battery of the invention mainly comprises a positive electrode, a positive electrode electrolyte, a diaphragm, a negative electrode and a negative electrode electrolyte, wherein the positive electrode electrolyte comprises Fe(CN)6 4‑ or / and Fe(CN)6 3‑ , alkali and a regulator, wherein the regulator is MnO4 ‑ and MnO4 2‑ One or both of the above, by introducing MnO4 into the positive electrode electrolyte ‑ or / and MnO4 2‑ , increasing the concentration of positive electrode active materials, thereby increasing the battery energy density and reducing the volume of the battery system. At the same time, the lower limit of the operating temperature of the alkaline zinc-iron flow battery is reduced from room temperature to below 0°C, which broadens the scope of use of the alkaline zinc-iron flow battery and greatly reduces the system maintenance cost.

Description

Technical Field

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

[0002] With the increasing depletion of fossil energy, the development and utilization of renewable energy such as wind energy and solar energy has become the focus of attention of all countries. Since wind energy and solar energy are discontinuous and unstable due to factors such as weather, this will cause impact on the power grid during the process of renewable energy power generation and grid connection, affecting the power supply quality and grid stability. Energy storage technology can solve this problem and ensure the efficient and stable operation of renewable energy power generation and grid connection. Energy storage technology is mainly divided into two categories: physical energy storage and chemical energy storage. Among them, chemical energy storage represented by flow batteries has the most advantages in large-scale energy storage due to its many advantages such as independent power and capacity, rapid response, simple structure, easy design, long cycle life, and environmental friendliness. Alkaline zinc-iron flow batteries use abundant zinc and iron as active materials, with the characteristics of low cost (~$100 / kWh) and high open circuit voltage (1.74V). They have good application prospects in the field of energy storage, especially distributed energy storage. However, the concentration of positive electrode active substances in the electrolyte of alkaline zinc-iron flow batteries is relatively low, resulting in low battery energy density and large battery system volume. At the same time, since the solubility of positive electrode active substances is greatly affected by temperature, the positive electrode active substances are easily precipitated when the battery operates at low temperatures, causing battery failure. Summary of the invention

[0003] In view of this, an object of the present invention is to provide an alkaline zinc-iron liquid flow battery positive electrode electrolyte and an alkaline zinc-iron liquid flow battery obtained by assembling the same.

[0004] The object of the present invention is to achieve the following:

[0005] The present invention provides a positive electrolyte for a liquid flow battery, comprising Fe(CN)6 4- or / and Fe(CN)6 3- , alkali and a regulator, wherein the regulator is MnO4 - and MnO4 2- One or both of the following.

[0006] Furthermore, the alkali is one or both of sodium hydroxide and potassium hydroxide.

[0007] Furthermore, the positive electrode electrolyte is an aqueous electrolyte.

[0008] Furthermore, the positive electrode electrolyte contains Fe(CN)6 4- or / and Fe(CN)6 3- The total concentration is 0.2-0.8M, OH - Concentration is 0.6-4M, MnO4- or / and MnO4 2- The total concentration is 0.2-1M, Fe(CN)6 4- or / and Fe(CN)6 3- The total concentration of MnO4 - or / and MnO4 2- The total concentration ratio is (4:1)-(1:1).

[0009] Furthermore, the positive electrode electrolyte contains Fe(CN)6 4- or / and Fe(CN)6 3- The total concentration is 0.6-0.8M, OH - Concentration is 0.6-2M, MnO4 - or / and MnO4 2- The total concentration is 0.4-1M.

[0010] Another aspect of the present invention provides an alkaline zinc-iron flow battery, which mainly comprises a positive electrode, a positive electrode electrolyte, a diaphragm, a negative electrode and a negative electrode electrolyte, wherein the positive electrode electrolyte is the positive electrode electrolyte described above, and MnO4 is introduced into the positive electrode electrolyte. - or / and MnO4 2- , increasing the concentration of positive electrode active materials, thereby increasing the battery energy density and reducing the volume of the battery system. At the same time, the lower limit of the operating temperature of the alkaline zinc-iron flow battery is reduced from room temperature to below 0°C, which broadens the application range of the alkaline zinc-iron flow battery and can inhibit the migration of water in the negative electrode electrolyte to the positive electrode in the alkaline zinc-iron flow battery.

[0011] Furthermore, the negative electrode electrolyte comprises Zn(OH)4 2- and a base, wherein the base is one or both of sodium hydroxide and potassium hydroxide.

[0012] Furthermore, the negative electrode electrolyte contains Zn(OH)4 2- The concentration is 0.2-0.8M, OH - The concentration is 0.6-4M.

[0013] Furthermore, the diaphragm is selected from an ion conducting membrane and a Nafion membrane, preferably a sulfonated polyetheretherketone ion conducting membrane.

[0014] Furthermore, the electrode materials of the positive electrode and the negative electrode are selected from graphite felt or carbon felt, preferably carbon felt.

[0015] The beneficial effects of the present invention compared with the prior art are as follows:

[0016] 1. The existing alkaline zinc-iron flow battery electrolyte has a low concentration of positive electrode active material (the solubility of positive electrode active material is low, and the current positive electrode active material has a maximum of 0.8M), resulting in low battery energy density and large battery system volume. - / MnO4 2- The electrode pair is redox active under alkaline conditions. By introducing MnO4 into the positive electrode electrolyte - / MnO4 2- The electrode pair can increase the concentration of positive electrode active materials, thereby increasing the battery energy density and reducing the system volume.

[0017] 2. The present invention adjusts Fe(CN)6 4- The concentration and MnO4 - / MnO4 2- The concentration ratio of the two is made between (4:1)-(1:1). Under the condition of keeping the total active material concentration unchanged, the low-temperature performance of the battery is improved, the operating temperature range of the alkaline zinc-iron flow battery is widened, the low-temperature stability of the system is improved, and the maintenance cost of the system is greatly reduced.

[0018] 3. By introducing MnO4 into the cathode electrolyte - / MnO4 2- , reducing the total ion concentration in the positive electrode electrolyte, thereby inhibiting the migration of water in the negative electrode electrolyte to the positive electrode in the alkaline zinc-iron flow battery, and improving the battery cycle stability.

[0019] 4. By regulating the alkali concentration, the occurrence of manganese disproportionation reaction in alkaline solution can be effectively inhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0021] Figure 1 The cyclic charge and discharge performance of the alkaline zinc-iron flow battery assembled in Example 1.

[0022] Figure 2 The cyclic charge and discharge performance of the alkaline zinc-iron flow battery assembled in Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

[0024] Example 1

[0025] Alkaline zinc-iron flow batteries were assembled using sulfonated polyetheretherketone (SPEEK) ion-conducting membranes with a cathode electrolyte composition of 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+0.4mol L -1 Na2MnO4+2mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L -1 Na2Zn(OH)4+2mol L -1 NaOH. The positive electrolyte volume is 80mL; the negative electrolyte volume is 80mL; under normal temperature conditions, at 80mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0026] The results are as follows Figure 1 As shown, it can be seen that the battery charging and discharging performance is stable, and the energy density of the battery using this component electrolyte can reach 20Wh / L.

[0027] Comparative Example 1

[0028] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The cathode electrolyte composition was 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+2mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L - 1 Na2Zn(OH)4+2mol L -1 NaOH. The positive electrolyte volume is 80mL; the negative electrolyte volume is 80mL; under normal temperature conditions, at 80mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0029] The results are as follows Figure 2 As shown, the battery charge and discharge performance is stable, and the energy density of the battery using this component electrolyte is only 14Wh / L. It can be seen that the energy density of the electrolyte battery with added Na2MnO4 is increased by 6Wh / L compared with the battery without addition.

[0030] Example 2

[0031] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The cathode electrolyte composition was 0.3 mol L -1Na4Fe(CN)6+0.3mol L -1 K4Fe(CN)6+0.2mol L -1 Na2MnO4+2mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L -1 Na2Zn(OH)4+2mol L -1 NaOH. The positive electrolyte volume is 80 mL; the negative electrolyte volume is 80 mL; at 15 °C, at 80 mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0032] By converting Fe(CN)6 4- The concentration was reduced to 0.6 mol L -1 , and add 0.2 mol L -1 MnO4 2- Under the condition of keeping the total active material concentration unchanged, the above battery can operate normally at a temperature of 15°C without electrolyte precipitation.

[0033] Comparative Example 2

[0034] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The cathode electrolyte composition was 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+2mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L - 1 Na2Zn(OH)4+2mol L -1 NaOH. The positive electrolyte volume is 80 mL; the negative electrolyte volume is 80 mL; at 15 °C, at 80 mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0035] During the charging process, the positive electrode electrolyte precipitates, clogging the battery and causing it to fail to operate normally.

[0036] Example 3

[0037] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The cathode electrolyte composition was 0.2 mol L -1 Na4Fe(CN)6+0.2mol L -1K4Fe(CN)6+0.4mol L -1 Na2MnO4+2mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L -1 Na2Zn(OH)4+2mol L -1 NaOH. The positive electrolyte volume is 80 mL; the negative electrolyte volume is 80 mL; at 0 °C, at 80 mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0038] By converting Fe(CN)6 4- The concentration was reduced to 0.4 mol L -1 , and 0.4 mol L -1 MnO4 2- Under the condition of keeping the total active material concentration unchanged, the above battery operates normally at a temperature of 0°C without electrolyte precipitation. 2- While keeping the total active material concentration unchanged, the lower limit of the operating temperature of the alkaline zinc-iron flow battery was reduced from room temperature to 0°C, broadening the application range of the alkaline zinc-iron flow battery.

[0039] Example 4

[0040] Alkaline zinc-iron flow batteries were assembled using sulfonated polyetheretherketone (SPEEK) ion-conducting membranes with a composition of 0.3 mol L -1 Na4Fe(CN)6+0.3mol L -1 K4Fe(CN)6+0.2mol L -1 Na2MnO4+2mol L -1 The positive electrolyte was NaOH and 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+2mol L -1 The positive electrode electrolyte is NaOH; the negative electrode electrolyte composition is 0.6 mol L -1 Na2Zn(OH)4+2mol L -1 The volume of the above two positive electrolytes is 80mL; the volume of the negative electrolyte is 80mL; after assembling the alkaline zinc-iron flow battery, at room temperature, at 80mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0041] At 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+2mol L -1 When NaOH is the positive electrode electrolyte, the negative electrode electrolyte migrates 40 mL to the positive electrode after 50 cycles. -1 Na4Fe(CN)6+0.3mol L -1 K4Fe(CN)6+0.2mol L -1 Na2MnO4+2mol L -1 When the positive electrode electrolyte is used, the negative electrode electrolyte migrates 5 mL to the positive electrode after 50 cycles, and the electrolyte migration rate decreases. This is mainly due to the introduction of MnO4 in the positive electrode electrolyte. - / MnO4 2- , which reduces the total ion concentration in the positive electrode electrolyte. This also shows that MnO4 - / MnO4 2- The introduction of can reduce the migration of electrolyte in alkaline zinc-iron flow batteries.

[0042] Comparative Example 3

[0043] Alkaline zinc-iron flow batteries were assembled using sulfonated polyetheretherketone (SPEEK) ion-conducting membranes with a cathode electrolyte composition of 0.4 mol L -1 Na4Fe(CN)6+0.4mol L -1 K4Fe(CN)6+0.4mol L -1 Na2MnO4+5mol L -1 NaOH; the negative electrode electrolyte composition is 0.6 mol L -1 Na2Zn(OH)4+5mol L -1 NaOH. The positive electrolyte volume is 80mL; the negative electrolyte volume is 80mL; under normal temperature conditions, at 80mA cm -2 The current density was charged to 2 V, 80 mA cm -2 The discharge was carried out to 0.1 V under the condition of current density.

[0044] When the alkali concentration in the electrolyte increases to 5 mol L -1 When the battery is blocked, the positive electrode may be blocked. This may be due to the disproportionation reaction of manganese to form solid manganese dioxide as the alkali concentration increases.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrolyte for an alkaline zinc-iron flow battery, characterized in that: Including Fe(CN)6 4- or / and Fe(CN)6 3- , alkali and a regulator, wherein the regulator is MnO4 - and MnO4 2- One or both of the following: The positive electrode electrolyte Fe(CN)6 4- or / and Fe(CN)6 3- The total concentration is 0.2-0.8M, OH - Concentration is 0.6-4M, MnO4 - or / and MnO4 2- The total concentration is 0.2-1M.

2. The positive electrode electrolyte according to claim 1, characterized in that The alkali is one or both of sodium hydroxide and potassium hydroxide.

3. The positive electrode electrolyte according to claim 1, characterized in that The positive electrode electrolyte is an aqueous electrolyte.

4. An alkaline zinc-iron flow battery, characterized in that: The invention mainly comprises a positive electrode, a positive electrode electrolyte, a diaphragm, a negative electrode and a negative electrode electrolyte, wherein the positive electrode electrolyte is the positive electrode electrolyte according to any one of claims 1 to 3.

5. The alkaline zinc-iron flow battery according to claim 4, characterized in that: The negative electrode electrolyte includes Zn(OH)4 2- and a base, wherein the base is one or both of sodium hydroxide and potassium hydroxide.

6. The alkaline zinc-iron flow battery according to claim 5, characterized in that: The negative electrode electrolyte Zn(OH)4 2- The concentration is 0.2-0.8M, OH - The concentration is 0.6-4M.

7. The alkaline zinc-iron flow battery according to claim 4, characterized in that: The diaphragm is selected from an ion conducting membrane and a Nafion membrane.

8. The alkaline zinc-iron flow battery according to claim 7, characterized in that: The diaphragm is a sulfonated polyetheretherketone ion conducting membrane.

9. The alkaline zinc-iron flow battery according to claim 4, characterized in that: The electrode materials of the positive electrode and the negative electrode are selected from graphite felt or carbon felt.

10. The alkaline zinc-iron flow battery according to claim 9, characterized in that: The electrode materials of the positive electrode and the negative electrode are carbon felt.

Images