Alkaline zinc-manganese flow battery

Abstract

The application relates to the technical field of liquid flow batteries, in particular to an alkaline zinc-manganese liquid flow battery, the positive electrode of the battery is a liquid-liquid phase reaction of MnO4 ‑ / MnO4 2‑ , and the negative electrode is a Zn(OH)4 2‑ / Zn deposition-dissolution reaction. The positive electrode adopts MnO4 ‑ / MnO4 2‑ as the active substance, the concentration of the positive electrode active substance of the alkaline zinc-based liquid flow battery is improved, and the energy density of the battery is improved. The positive electrode adopts the liquid-liquid phase reaction to solve the problem that the positive electrode of the traditional zinc-manganese liquid flow battery is a liquid-solid reaction, the surface capacity of the battery is limited, the working current density of the battery is improved, and the power density of the battery is improved. In addition, the positive electrode adopts MnO4 ‑ / MnO4 2‑ as the active substance, and the low-temperature stability of the alkaline zinc-based liquid flow battery is improved.

Description

Technical Field

[0001] This invention relates to the field of flow battery technology, and particularly to the field of zinc-manganese flow batteries. Background Technology

[0002] With the increasing depletion of fossil fuels, the development and utilization of renewable energy sources such as wind and solar power have become a focus of attention for countries worldwide. However, wind and solar power are discontinuous and unstable due to weather and other factors, which can impact the power grid during grid connection, affecting power quality and grid stability. Energy storage technology can solve this problem, ensuring the efficient and stable operation of renewable energy generation connected to the grid. 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 greatest advantage in large-scale energy storage due to its many advantages, such as independent power and capacity, rapid response, simple structure, ease of design, long cycle life, and environmental friendliness. Alkaline zinc-iron flow batteries, using abundant zinc and iron as active materials, are characterized by low cost (~$100 / kWh) and high open-circuit voltage (1.74V), showing great application prospects in the energy storage field, especially in distributed energy storage. However, the concentration of positive electrode active material in the electrolyte of alkaline zinc-iron flow batteries is relatively low, resulting in low battery energy density and large battery system size. At the same time, since the solubility of positive electrode active material is greatly affected by temperature, positive electrode active material is prone to precipitation when the battery is operating at low temperatures, leading to battery failure. Summary of the Invention

[0003] This invention proposes an alkaline zinc-manganese flow battery, with MnO4 as the positive electrode. - / MnO4 2- The liquid-liquid phase reaction, with Zn(OH)4 as the negative electrode. 2- / Zn deposition and dissolution reaction. MnO4 is used at the positive electrode. - / MnO4 2- This technology utilizes MnO4 as the active material to increase the concentration of the positive electrode active material in alkaline zinc-based flow batteries, thereby improving the battery's energy density. By employing a liquid-liquid phase reaction at the positive electrode, it addresses the issue of limited battery surface capacity caused by liquid-solid reactions in traditional zinc-manganese flow batteries, thus increasing the battery's operating current density and power density. Furthermore, the use of MnO4 at the positive electrode... - / MnO4 2- As an active material, it improves the low-temperature stability of alkaline zinc-based flow batteries.

[0004] The complete technical solution provided by this invention is as follows:

[0005] The positive electrode of the alkaline zinc-manganese flow battery is MnO4. - / MnO4 2- The liquid-liquid phase reaction, with Zn(OH)4 as the negative electrode. 2- / Zn deposition and dissolution reaction.

[0006] The positive electrode active material of the alkaline zinc-manganese flow battery is NaMnO4, wherein the concentration of NaMnO4 is 1-3.5M, preferably 2-3M.

[0007] The alkaline zinc-manganese flow battery supports NaOH or KOH as the electrolyte, or a mixture of both; wherein the hydroxide concentration is 4-8M, preferably 6-8M.

[0008] The alkaline zinc-manganese flow battery operates at a temperature of -20℃ to 50℃, preferably 20℃ to 30℃.

[0009] The negative electrode active material of the alkaline manganese flow battery is Zn(OH)4. 2- Anthraquinone, preferably Zn(OH)4 2- The concentration of the negative electrode active material is 0.5-1.25M, preferably 1-1.25M.

[0010] The zinc-manganese flow battery positive electrode electrolyte contains one of ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and their salts, with DTPA being preferred.

[0011] The molar ratio of the positive electrode additive to NaMnO4 is 2:1-0.5:1, preferably 1:1.

[0012] The electrode materials for the positive and negative electrodes are selected from graphite felt or carbon felt, with carbon felt being preferred.

[0013] The diaphragm is a sulfonated polyether ether ketone ion-conducting membrane.

[0014] The zinc-manganese redox flow battery consists of, in sequence, a positive electrode current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a zinc sheet, a negative electrode frame, and a negative electrode current collector. The battery structure includes an additional zinc sheet on the carbon felt negative electrode side near the current collector.

[0015] Advantages of this invention:

[0016] 1. Compared with traditional alkaline zinc-based flow batteries, the positive electrode uses MnO4 - / MnO4 2- As an active material, it increases the concentration of positive electrode active material in alkaline zinc-based flow batteries, thereby improving battery energy density and low-temperature stability.

[0017] 2. For the use of MnO4 in alkaline zinc-manganese flow battery systems - / MnO4 2- To address the manganese disproportionation problem present when the active material is used, it is necessary to introduce appropriate additives into the positive electrode electrolyte to significantly suppress manganese disproportionation and improve battery cycle stability and voltage efficiency.

[0018] 3. By using a liquid-liquid phase reaction at the positive electrode, the problem of limited battery surface capacity caused by the liquid-solid reaction at the positive electrode in traditional zinc-manganese flow batteries is solved.

[0019] 4. The positive electrode is MnO4 - / MnO4 2- The liquid-liquid phase reaction increases the battery's operating current density and power density.

[0020] 5. The negative electrode active material is mainly stored in the negative electrode electrolyte. The battery structure adds a zinc sheet to the side of the carbon felt negative electrode near the current collector. This is for the first discharge cycle of the battery system. In addition, the negative electrode reaction mainly occurs at the interface between the membrane and the carbon felt. After long-term charge and discharge cycles, zinc dendrites are prone to pierce the membrane. The zinc sheet is placed away from the membrane, which is conducive to inducing the direction of zinc deposition and improving the long-term cycle stability of the battery.

[0021] 6. Due to the strong oxidizing properties of the active material in the positive electrode electrolyte, the separator is required to have good chemical stability and high ion conductivity. Sulfonated polyether ether ketone ion-conducting membrane is preferred, and it exhibits excellent battery performance and cycle life when applied to this system. Attached Figure Description

[0022] Figure 1 Performance diagram of an alkaline zinc-manganese redox flow battery;

[0023] Figure 2 Scanning electron microscope image of zinc negative electrode with zinc sheet placed;

[0024] Figure 3 Performance graph of batteries without Na2Zn(OH)4 in electrolyte;

[0025] Figure 4 This is a graph showing the battery performance when only the zinc sheet is used as the negative electrode. Detailed Implementation

[0026] In the following embodiments, the alkaline zinc-manganese flow battery includes, in sequence, a positive electrode current collector, a positive electrode placed in the positive electrode frame, a separator, a negative electrode and zinc sheet placed in the negative electrode frame, and a negative electrode current collector.

[0027] Example 1

[0028] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH, and each containing a final concentration of 1 mol L -1 NaMnO4, 1.5 mol L - 1 NaMnO4, 2 mol L -1NaMnO4, 2.5 mol L -1 NaMnO4, 3 mol L -1 NaMnO4, 3.5 mol L -1 An aqueous solution of NaMnO4, with a negative electrode electrolyte composition of 0.5 mol / L. -1 Na₂Zn(OH)₄ + 6mol L -1 The electrolyte solution consisted of NaOH in an aqueous solution; the positive electrode electrolyte volume was 80 mL; the negative electrode electrolyte volume was 80 mL; both the positive and negative electrodes were carbon felt, and a zinc sheet was placed inside the negative electrode frame, positioned closer to the negative current collector. First, at 10 mA cm⁻¹... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0029] The battery performance is as follows:

[0030]

[0031] The battery performance of NaMnO4 solutions with different concentrations shows that the electrolyte concentration (VE) first increases and then decreases with increasing electrolyte concentration. The optimal NaMnO4 concentration is 2-3 M. When the NaMnO4 concentration is 2 mol / L... -1 The battery performance is optimal at this time. However, the battery CE is relatively low, mainly due to MnO4. 3- This is caused by a disproportionation reaction in an alkaline solution.

[0032] Example 2

[0033] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 The negative electrode electrolyte composition is 0.5 mol / L NaMnO4. - 1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned closer to the negative current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2The battery was discharged to 0.1V under the specified current density. The battery operating temperatures were -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, and 50℃.

[0034] Temperature / °C CE / % VE / % EE / % -20 90 75 68 -10 91 76 69 0 92 78 72 10 93 80 74 20 94 88 83 30 94 88 83 40 90 88 79 50 89 88 78

[0035] Alkaline zinc-manganese batteries can operate normally within the range of -20℃ to 50℃, with the preferred operating temperature being 20℃ to 30℃. As the temperature increases, both CE and VE of the battery increase. When the temperature is above 30℃, VE remains unchanged while CE decreases.

[0036] Example 3

[0037] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 2 mol L of NaMnO4 was added to the positive electrode electrolyte. - 1 EDTA, NTA, DTPA. The negative electrode electrolyte composition is 0.5 mol / L. -1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned closer to the negative electrode current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0038] The properties of different additives are as follows:

[0039] Additive CE / % VE / % EE / % EDTA 99 88 87 NTA 99 89 88 DPTA 99 90 89

[0040] After adding additives to the electrolyte, the battery CE (electrochemical conductivity) of all batteries reached 99%, with the battery using DPTA as the additive showing the best performance. Compared with the battery without additives, the battery CE increased by 5%, indicating that the addition of DPTA additives effectively suppressed MnO4 in the battery. 3- Disproportionation reaction.

[0041] Example 4

[0042] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 The negative electrode electrolyte composition is 0.5 mol / L NaMnO4. - 1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned near the negative electrode current collector. And first at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Charged to 2.1V under the specified current density conditions.

[0043] Using Zn(OH)4 2- The open-circuit voltage of the active material battery can reach 1.9V, and Zn(OH)4 is used in the negative electrode electrolyte. 2- The high open-circuit voltage of active material batteries is beneficial for obtaining high energy density.

[0044] Example 5

[0045] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 1 mol L of NaMnO4 was added to the positive electrode electrolyte. - 1 DTPA, 2 mol L -1 DTPA, 3 mol L -1 DTPA, 4 mol L -1 DTPA. The negative electrode electrolyte composition is 0.5 mol / L. -1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned closer to the negative electrode current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0046] The battery performance of different additive concentrations is as follows:

[0047] Concentration / mol L -1 ]] CE / % VE / % EE / % 1 96 90 86 2 99 90 89 3 99 88 87 4 99 86 85

[0048] As can be seen from the table, the battery performance is optimal when the ratio of active material to additive concentration is 1:1. When the additive concentration is too low, the voltage efficiency decreases. The reason may be that the low concentration of additive cannot completely suppress the battery disproportionation reaction, resulting in a low CE. When the additive concentration is too high, the battery VE decreases.

[0049] Example 6

[0050] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 NaMnO4+2mol L -1 DPTA, negative electrode electrolyte composition is 0.5 mol L -1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned closer to the negative electrode current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0051] from Figure 1 As can be seen, the alkaline zinc-manganese flow battery exhibits good cycle stability, with an average CE of 99%, VE of 90%, and EE of 89% after 800 cycles. The battery energy density is 30Wh / L. Figure 2 It can be seen that zinc is also deposited inside the carbon felt. This is mainly because the zinc sheet is positioned away from the membrane, which helps to induce zinc to deposit away from the membrane, thereby improving the long-term cycle stability of the battery.

[0052] Example 7

[0053] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 2 mol / L. -1 NaMnO4+6mol L -1 NaOH + 2 mol L -1 DPTA; the negative electrode electrolyte composition is 0.5 mol / L. -1Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 200mL; negative electrode electrolyte volume 200mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned near the negative electrode current collector. First, at 10mAcm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0054] Alkaline zinc-manganese flow batteries can achieve a surface capacity of up to 100 mAh / cm². 2 The battery surface capacity can reach four times that of a neutral zinc-manganese flow battery. This is mainly due to the positive electrode being MnO4. - / MnO4 2- The liquid-liquid phase reaction allows the positive electrode surface capacity to be unrestricted.

[0055] Example 8

[0056] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 2 mol / L. -1 NaMnO4+6mol L -1 NaOH; the negative electrode electrolyte composition is 0.5 mol / L. - 1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 200 mL; negative electrode electrolyte volume 200 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned near the negative electrode current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of 80mA cm⁻¹. -2 Under the condition of charging to 2.1V at a current density, and then under the condition of voltage cutoff, 80mA cm -2 Discharged to 0.1V under the current density conditions.

[0057] The alkaline zinc-manganese flow battery exhibits good cycle stability, with an average cycle current density (CE) of 97%, a current efficiency (VE) of 80%, and an energy efficiency (EE) of 78%. Compared to conventional zinc-manganese batteries, the alkaline zinc-manganese flow battery has a higher operating current density and a power density of 130 mW / cm³. 2 .

[0058] Comparative Example 1

[0059] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective battery area is 36 cm². 2 The positive electrode electrolyte composition is 0.4 mol / L. -1 Na₄Fe(CN)₆ + 0.4 mol 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. Positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; at 40 mA cm⁻¹ -2 Under current density conditions, it is charged to 2.1V, 40mA cm -2 Discharged to 0.1V under the specified current density. The alkaline zinc-iron flow battery consists of, in sequence, a positive current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a negative electrode frame, and a negative current collector.

[0060] The battery has an energy density of 16Wh / L, which is 14Wh / L lower than that of an alkaline zinc-manganese flow battery.

[0061] Comparative Example 2

[0062] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective battery area is 36 cm². 2 The positive electrode electrolyte composition is 0.4 mol / L. -1 Na₄Fe(CN)₆ + 0.4 mol 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. Positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; at 40 mA cm⁻¹ -2 Under current density conditions, it is charged to 2.1V, 40mA cm -2 Discharged to 0.1V under the specified current density. Battery operating temperature: 0℃. Battery structure is the same as Comparative Example 1.

[0063] When alkaline zinc-iron flow batteries operate at 0°C, electrolyte precipitation occurs, clogging the battery and causing it to fail and malfunction.

[0064] Comparative Example 3

[0065] A neutral zinc-manganese flow battery was assembled using a PE porous membrane as the separator, with an effective cell area of ​​36 cm². 2 The positive electrode electrolyte composition is 1.5 mol / L.-1 MnAc+2mol L -1 KCl; the negative electrode electrolyte composition is 1.5 mol L. -1 ZnCl₂ + 2mol L -1 KCl. At 40 mAcm -2 The electrode was charged to 2.1V under the specified current density conditions. The volume of the positive electrode electrolyte was 200mL, and the volume of the negative electrode electrolyte was 200mL. Both the positive and negative electrodes were carbon felt. The charge was applied at 40mA / cm². -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the specified current density. The neutral zinc-manganese flow battery consists of, in sequence, a positive current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a negative electrode frame, and a negative current collector.

[0066] The neutral zinc-manganese battery has a surface capacity of only 25mAh / cm². 2 Battery power density 50mW / cm³ 2 .

[0067] Comparative Example 4

[0068] An alkaline zinc-manganese flow battery was assembled using a Nafion 212 membrane. The effective cell area is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 NaMnO4+2mol L -1 DPTA, negative electrode electrolyte composition is 1 mol L -1 Na₂Zn(OH)₄ + 6mol / L -1 NaOH; positive electrode electrolyte volume 80mL; negative electrode electrolyte volume 80mL; the alkaline zinc-manganese flow battery consists of, in sequence, a positive electrode current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a zinc plate, a negative electrode frame, and a negative electrode current collector, with the zinc plate placed near the negative electrode current collector. First, at 10mA cm⁻¹... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0069] An alkaline zinc-manganese flow battery using Nafion 212 membrane as the separator achieves CE 95%, VE 85%, and EE 81%. The battery energy density is 22Wh / L. Compared to batteries using Nafion membranes, alkaline zinc-manganese batteries using SPEEK membranes can achieve higher battery efficiency and energy density.

[0070] Comparative Example 5

[0071] An alkaline zinc-iron flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective battery area is 36 cm². 2 The positive electrode electrolyte composition is 2 mol / L. -1 NaOH, 1 mol L -1 NaMnO4, 1 mol L -1 DPTA, negative electrode electrolyte composition is 0.5 mol L -1 Na₂Zn(OH)₄ + 2mol L -1 NaOH; other conditions are the same as in Example 1. Battery structure and test conditions are the same as in Example 1.

[0072] During the first discharge cycle, as the depth of discharge increases, battery blockage occurs at the negative electrode. This is mainly due to the low alkali concentration in the negative electrode electrolyte, which leads to zinc oxide precipitation inside the battery, causing blockage.

[0073] Comparative Example 6: The negative electrode electrolyte does not contain Na2Zn(OH)4.

[0074] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 NaMnO4+2mol L -1 DPTA, negative electrode electrolyte composition is 6 mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt, with a zinc sheet placed inside the negative electrode frame, positioned closer to the negative electrode current collector. First, at 10 mA cm... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0075] from Figure 3 As can be seen, the battery performance degrades after 90 cycles, mainly due to zinc dendrites piercing the separator. However, the battery with Na2Zn(OH)4 in the electrolyte shows no significant performance degradation after 800 cycles. This is primarily because the presence of Na2Zn(OH)4 in the negative electrode electrolyte reduces concentration polarization during zinc deposition, resulting in smoother zinc deposition and reduced zinc dendrite formation.

[0076] Comparative Example 7

[0077] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 NaMnO4+2mol L -1 DPTA, negative electrode electrolyte composition is 0.5 mol L -1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80mL; negative electrode electrolyte volume 80mL; the alkaline zinc-manganese flow battery consists of, in sequence, a positive electrode current collector, a positive electrode frame, a positive electrode, a separator, a zinc plate, a negative electrode frame, and a negative electrode current collector, with the zinc plate placed near the negative electrode current collector. First, at 10mA cm⁻¹... -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2 Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0078] from Figure 4 Temperature / °C CE / % VE / % EE / % Additive CE / % VE / % EE / % EDTA NTA DPTA CE / % VE / % EE / % Figure 1 Figure 2 Figure 3 Figure 4 Temperature / °C CE / % VE / % EE / % Additive CE As can be seen, battery performance degrades as charge-discharge cycles continue. This is mainly because when only the zinc sheet is used as the negative electrode, the zinc deposition reaction mainly occurs on the zinc surface near the separator. As the cycle progresses, zinc dendrites are prone to pierce the separator, leading to battery failure.

[0079] Comparative Example 8 (no zinc sheet added to the negative electrode)

[0080] An alkaline zinc-manganese flow battery was assembled using a sulfonated polyetheretherketone (SPEEK) ion-conducting membrane. The effective area of ​​the battery is 36 cm². 2 The positive electrode electrolyte composition is 6 mol / L. -1 NaOH + 2 mol L -1 2 mol L of NaMnO4 was added to the positive electrode electrolyte. -1 DTPA. The negative electrode electrolyte composition is 0.5 mol / L. -1 Na₂Zn(OH)₄ + 6mol L -1 NaOH; positive electrode electrolyte volume 80 mL; negative electrode electrolyte volume 80 mL; both positive and negative electrodes are carbon felt. The alkaline zinc-manganese flow battery consists of, in sequence, a positive electrode current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a negative electrode frame, and a negative electrode current collector. The battery charge / discharge test conditions are as follows: first at 10 mA cm⁻¹ -2 Discharged to 0.1V under a current density of [value missing]. Then discharged at 40mA cm [value missing]. -2Under the condition of current density, it is charged to 2.1V, and then the voltage is cut off, 40mA cm -2 Discharged to 0.1V under the current density conditions.

[0081] Testing revealed that the battery could not discharge, preventing normal charge-discharge cycles. The cause was analyzed to be that the positive electrode active material is oxidized NaMnO4, while the corresponding negative electrode requires reduced zinc for the battery to discharge. In this design, the negative electrode lacked zinc, preventing the battery from completing its first discharge cycle.

Claims

1. An alkaline zinc-manganese flow battery, characterized in that: During battery charging and discharging, the positive electrode is MnO4. - With MnO4 2- A reversible liquid-liquid phase reaction occurs between them, with the negative electrode being Zn(OH)4. 2- The reversible deposition and dissolution reaction with Zn, wherein the positive electrode active material in the alkaline zinc-manganese flow battery electrolyte is one or two of NaMnO4 and KMnO4; wherein MnO4 - The concentration is 1-3.5 M, and the active material of the negative electrode of the alkaline zinc-manganese flow battery is Zn(OH)4. 2- The concentration of the negative electrode active material is 0.5-1.25M. The supporting electrolyte in the alkaline zinc-manganese flow battery is one or a mixture of NaOH and KOH. The concentration of hydroxide ions in the positive and / or negative electrode electrolyte is 4-8M. One or more positive electrode additives, including ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), and their soluble salts, are added to the positive electrode electrolyte of the zinc-manganese flow battery. The alkaline zinc-manganese flow battery includes, in sequence, a positive electrode current collector, a positive electrode frame, a positive electrode, a separator, a negative electrode, a zinc sheet, a negative electrode frame, and a negative electrode current collector. The separator is a sulfonated polyether ether ketone ion-conducting membrane.

2. The alkaline zinc-manganese flow battery according to claim 1, characterized in that: The MnO4 - The concentration is 2-3 M; the concentration of the negative electrode active material is 1-1.25 M.

3. The alkaline zinc-manganese flow battery according to claim 1, characterized in that: The concentration of hydroxide ions in the positive and / or negative electrode electrolytes is 6-8M.

4. The alkaline zinc-manganese flow battery according to claim 1, characterized in that: The alkaline zinc-manganese flow battery operates at a temperature of -20℃ to 50℃.

5. The alkaline zinc-manganese redox flow battery according to claim 4, characterized in that: The alkaline zinc-manganese flow battery operates at a temperature of 20-30℃.

6. The alkaline zinc-manganese flow battery according to any one of claims 1-3, characterized in that: Ethylenetriaminepentaacetic acid (DTPA) is added to the positive electrode electrolyte of a zinc-manganese redox flow battery; the molar ratio of the positive electrode additive to Mn is 2:1-0.5:

1.

7. The alkaline zinc-manganese flow battery according to claim 1, characterized in that: The electrode materials for the positive and / or negative electrodes are selected from graphite felt or carbon felt.

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