A manganese chloride electrolyte and its application in manganese-based flow batteries

Abstract

This invention discloses a manganese chloride electrolyte and its application in a manganese-based flow battery. The manganese chloride electrolyte comprises the active substance manganese chloride and an amino acid additive; the amino acid additive is selected from one or more of glycine, alanine, valine, arginine, lysine, and proline. The amino acid additive introduced into the manganese chloride electrolyte of this invention can coordinate with chloride and manganese ions in the electrolyte, altering the solvation structure of chloride and manganese ions and the electrochemical reactions during charge and discharge, thereby avoiding the toxicity of chlorine gas evolution and the release of manganese nitrogen. 3+ Disproportionation causes battery performance degradation. This electrolyte preparation method features a simple production process, facilitates continuous mass production with zero pollutant emissions, is environmentally friendly, safe, and has low production costs. This invention enables the application of high-concentration manganese chloride electrolyte in manganese-based flow batteries, maximizing the high solubility of manganese chloride.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and specifically relates to a manganese chloride electrolyte and its application in manganese-based flow batteries. Background Technology

[0002] The intermittent and fluctuating nature of wind and solar energy affects the stability of power systems. Energy storage technology is needed to achieve large-scale utilization of renewable energy. Flow batteries have attracted widespread attention due to their high safety and long lifespan. Vanadium redox flow battery energy storage technology, currently in the commercial demonstration stage, is one of the most mature energy storage technologies; however, the low electrode potential of the expensive vanadium electrolyte limits its further commercial development.

[0003] Manganese-based flow batteries have become a promising battery technology for large-scale energy storage due to their low cost, good electrochemical activity, and high energy density, but they still face challenges related to Mn. 3+ Ion disproportionation generates manganese dioxide, causing problems such as battery blockage and capacity decay. Previously, Xie Congxin et al. reported on "A Neutral Zinc-Manganese Secondary Battery and Electrolyte" (CN112490515B), where the positive electrode reaction was based on Mn... 2+ The solid-liquid phase transformation with MnO2 avoids Mn 3+ While manganese chloride exhibits high ion disproportionation, the low solubility of its active material, manganese acetate, limits the battery's energy density. Among various manganese salts, manganese chloride possesses extremely high solubility, exceeding 6.42 mol / L in aqueous solution. However, manganese chloride electrolytes suffer from trivalent manganese ion disproportionation during charging and are prone to severe chlorine evolution reactions, reducing battery capacity and safety, thus limiting the application of highly soluble manganese chloride. Summary of the Invention

[0004] The purpose of this invention is to provide a manganese chloride electrolyte for manganese-based flow batteries. By optimizing the electrolyte formulation, the disproportionation reaction and chlorine evolution reaction of trivalent manganese ions are effectively avoided, thereby improving battery performance.

[0005] This invention alters the battery reaction process through the interaction between the additive and manganese ions in the electrolyte, thereby achieving Mn 2+ The solid-liquid phase transformation with MnO2 avoids Mn 3+ Ion disproportionation, and through the interaction between the additive and chloride ions in the electrolyte, the chloride evolution potential is increased, thereby preventing the chloride evolution reaction from occurring.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a manganese chloride electrolyte, wherein the manganese chloride electrolyte comprises an active substance and an amino acid additive; the amino acid additive is selected from one or more of glycine, alanine, valine, arginine, lysine, and proline; and the active substance is manganese chloride.

[0008] In the above technical solution, the concentration of the active substance is 0.01-6.42 mol / L, preferably 0.5 mol / L; the concentration of the additive is 0.01-5 mol / L, preferably 0.5 mol / L.

[0009] In the above technical solution, the electrolyte further includes a supporting electrolyte with a concentration of 0.01-3 mol / L, preferably 1 mol / L; the supporting electrolyte is one or more of KCl, K2SO4, NaCl, and Na2SO4, preferably KCl.

[0010] Another aspect of the present invention provides a method for preparing the above-mentioned manganese chloride electrolyte, characterized in that the method includes the following steps:

[0011] (1) Dissolve the amino acid additive in an aqueous solution and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved;

[0012] (2) Add manganese chloride to the solution prepared in step (1) and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved.

[0013] In the above technical solution, the method further includes: adding the supporting electrolyte to the solution prepared in step (2), stirring at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved, and then cooling the solution to room temperature.

[0014] In another aspect, the present invention provides the application of the above-mentioned manganese chloride electrolyte in a manganese-based flow battery.

[0015] In the above technical solution, the manganese-based flow battery is further comprising a stack consisting of one or more single cells connected in series and / or parallel. Each single cell includes a positive electrode plate, a positive current collector, a positive electrode, a separator, a negative electrode, a negative current collector, a negative electrode plate, a positive electrolyte storage tank containing positive electrolyte, a negative electrolyte storage tank containing negative electrolyte, and a pump. The manganese-based flow battery includes zinc-manganese flow batteries, copper-manganese flow batteries, and titanium-manganese flow batteries, but is not limited to these types of flow batteries.

[0016] In the above technical solution, the positive electrode electrolyte is further described as the manganese chloride electrolyte;

[0017] The negative electrode electrolyte is an aqueous solution containing a negative electrode active material, the concentration of which is 0.01-6 mol / L, preferably 0.5 mol / L.

[0018] The specific steps involved in preparing the negative electrode electrolyte are as follows:

[0019] (1) Dissolve zinc salt, copper salt or titanium salt in aqueous solution and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved;

[0020] (2) Add one or both of the negative electrode supporting electrolytes HCl and H2SO4 to the solution prepared in step (1), and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved; the concentration of the negative electrode supporting electrolyte is 0.01-3mol / L.

[0021] In the above technical solution, the composition of the positive and negative electrode electrolytes can also be the same. The manganese chloride electrolyte is dissolved with negative electrode active material and then used as the positive and negative electrode electrolytes. The concentration of the negative electrode active material is 0.01-6 mol / L, preferably 0.5 mol / L.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention provides a manganese chloride electrolyte for manganese-based flow batteries, realizing the application of high-concentration manganese chloride electrolyte in manganese-based flow batteries, maximizing the high solubility of manganese chloride, and significantly improving the energy density and cycle life of manganese-based flow batteries.

[0024] 2. By introducing amino acid additives, and utilizing the coordination effect between amino acids and manganese ions, the electrode reaction at the positive electrode becomes soluble Mn. 2+ The dissolution and deposition reaction between MnO2 solid and the battery is a reversible two-electron reaction, which greatly improves the battery's specific capacity and fundamentally avoids the degradation of MnO2. 3+ Ion disproportionation side reaction.

[0025] 3. The battery electrolyte provided by the present invention utilizes the coordination effect between the introduced amino acid additive and chloride ions to change the solvation structure of chloride ions, increase the electrode potential of the chloride evolution reaction, thereby making the chloride evolution reaction difficult to occur, improving the performance and safety of the battery, and providing a technical solution for suppressing the chloride evolution reaction.

[0026] 4. The electrolyte preparation method provided by this invention is simple and easy to implement. The chemical substances used are non-toxic, non-polluting, clean, environmentally friendly, and inexpensive, making it easy to achieve mass production. Attached Figure Description

[0027] The technical solution and other beneficial effects of the present invention will become apparent from the following detailed description of specific embodiments of the invention, in conjunction with the accompanying drawings.

[0028] Figure 1 The images show the phenomena observed after charging the zinc-manganese redox flow batteries obtained in Comparative Example 1 and Example 1. a) shows the electrolyte after charging in Comparative Example 1; b) shows the starch-potassium iodide test paper at the bottle mouth of Comparative Example 1; c) shows the electrolyte after charging in Comparative Example 1 after the addition of Mn. 3+ The phenomenon observed with the indicator (sodium pyrophosphate): d represents the electrolyte after charging in Example 1; e represents the starch-potassium iodide test paper at the bottle mouth in Example 1; f represents the electrolyte after charging in Example 1 with added Mn. 3+ The phenomenon observed with the indicator (sodium pyrophosphate);

[0029] Figure 2 For the zinc-manganese redox flow batteries obtained in Comparative Example 1 and Example 1, 20 mA / cm 2 At current density, 2 mA h / cm 2 Comparison of capacity and coulomb efficiency for areal capacity;

[0030] Figure 3 The battery performance diagrams are for the zinc-manganese redox flow batteries obtained in Comparative Example 1, Example 1, Example 4, Example 5, Example 6, Example 7, and Example 8.

[0031] Figure 4 The graph shows a comparison of the battery performance of the copper-manganese flow battery obtained in Comparative Example 2 and Example 18 and the titanium-manganese flow battery obtained in Comparative Example 3 and Example 19. Detailed Implementation

[0032] The present invention will be described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0033] Unless otherwise specified, the raw materials used in the embodiments of the present invention were all purchased through commercial channels.

[0034] Comparative Example 1

[0035] (1) Dissolve manganese chloride in an aqueous solution in 10 portions, stirring for 10 minutes each time at room temperature (25°C) and a speed of 400 r / min. The concentration of manganese chloride is 0.5 mol / L.

[0036] (2) Add KCl to the solution prepared in step (1) in 10 portions, stirring for 15 minutes each time at a temperature of 55℃ and a speed of 400r / min, and then cool to room temperature. The concentration of KCl is 1.0mol / L.

[0037] (3) Add zinc chloride, the active substance of the negative electrode electrolyte, to the solution prepared in step (2) in 10 portions. Each time, stir for 10 minutes at room temperature (25°C) and speed (400 r / min). The concentration of zinc chloride is 0.5 mol / L.

[0038] The resulting electrolyte contains both positive and negative electrode active materials, serving as both positive and negative electrode electrolytes. That is, the positive and negative electrode electrolytes have the same composition.

[0039] Comparative Example 2

[0040] The preparation method is similar to that of Comparative Example 1, except that the active substance of the negative electrode electrolyte is copper chloride.

[0041] Comparative Example 3

[0042] The positive and negative electrolytes have different compositions, and their preparation methods are as follows:

[0043] Preparation method of positive electrode electrolyte:

[0044] (1) Dissolve manganese chloride in an aqueous solution in 10 portions, stirring for 10 minutes each time at room temperature (25°C) and a speed of 400 r / min. The concentration of manganese chloride is 0.5 mol / L.

[0045] (2) Add KCl to the solution prepared in step (1) in 10 portions, stirring for 15 minutes each time at a temperature of 55℃ and a speed of 400r / min, and then cool to room temperature. The concentration of KCl is 1.0mol / L.

[0046] Preparation method of negative electrode electrolyte:

[0047] (1) Dissolve TiOSO4 in an aqueous solution and stir for 300 min at room temperature (25°C) and speed (400 r / min). The concentration of TiOSO4 is 0.5 mol / L.

[0048] (2) Add sulfuric acid to the solution prepared in step (1) in 10 portions. After each addition, stir for 10 minutes at room temperature (25°C) and speed (400 r / min). The sulfuric acid concentration is 1 mol / L.

[0049] Example 1

[0050] (1) Dissolve glycine in an aqueous solution and stir for 10 min at room temperature (25°C) and speed (400 r / min). The concentration of glycine is 0.5 mol / L.

[0051] (2) Add manganese chloride to the solution prepared in step (1) in 10 portions. After each addition, stir for 10 minutes at room temperature (25°C) and speed (400 r / min). The concentration of manganese chloride is 0.5 mol / L.

[0052] (3) Add KCl to the solution prepared in step (2) in 10 portions. After each addition, stir for 15 minutes at 55°C and 400 r / min, and then cool to room temperature. The concentration of KCl is 1.0 mol / L.

[0053] (4) Add zinc chloride, the active substance of the negative electrode electrolyte, to the solution prepared in step (3), and stir for 10 min at room temperature (25°C) and speed (400 r / min). The concentration of zinc chloride is 0.5 mol / L.

[0054] The resulting electrolyte contains both positive and negative electrode active materials, serving as both positive and negative electrode electrolytes. That is, the positive and negative electrode electrolytes have the same composition.

[0055] Example 2

[0056] The preparation method is similar to that in Example 1, except that the concentration of glycine is 0.25 mol / L.

[0057] Example 3

[0058] The preparation method is similar to that in Example 1, except that the concentration of glycine is 1.0 mol / L.

[0059] Example 4

[0060] The preparation method is similar to that in Example 1, except that the additive is alanine.

[0061] Example 5

[0062] The preparation method is similar to that in Example 1, except that the additive is valine.

[0063] Example 6

[0064] The preparation method is similar to that in Example 1, except that the additive is arginine.

[0065] Example 7

[0066] The preparation method is similar to that in Example 1, except that the additive is lysine.

[0067] Example 8

[0068] The preparation method is similar to that in Example 1, except that the additives are valine and arginine, with the concentration of valine being 0.25 mol / L and the concentration of arginine being 0.25 mol / L.

[0069] Example 9

[0070] The preparation method is similar to that in Example 1, except that the concentration of manganese chloride is 0.1 mol / L.

[0071] Example 10

[0072] The preparation method is similar to that in Example 1, except that the concentration of manganese chloride is 2.0 mol / L.

[0073] Example 11

[0074] The preparation method is similar to that in Example 1, except that the concentration of zinc chloride is 0.1 mol / L.

[0075] Example 12

[0076] The preparation method is similar to that in Example 1, except that the concentration of zinc chloride is 2.0 mol / L.

[0077] Example 13

[0078] The preparation method is similar to that in Example 1, except that the supporting electrolyte is K2SO4 with a concentration of 0.5 mol / L.

[0079] Example 14

[0080] The preparation method is similar to that in Example 1, except that the supporting electrolyte is NaCl.

[0081] Example 15

[0082] The preparation method is similar to that in Example 1, except that the supporting electrolytes are K2SO4 and KCl, with the concentration of K2SO4 being 0.25 mol / L and the concentration of KCl being 0.5 mol / L.

[0083] Example 16

[0084] The preparation method is similar to that in Example 1, except that the concentration of KCl is 0.1 mol / L.

[0085] Example 17

[0086] The preparation method is similar to that in Example 1, except that the concentration of KCl is 2.0 mol / L.

[0087] Example 18

[0088] The preparation method is similar to that in Example 1, except that the active substance of the negative electrode electrolyte is copper chloride.

[0089] Example 19

[0090] The positive and negative electrolytes have different compositions, and their preparation methods are as follows:

[0091] Preparation method of positive electrode electrolyte:

[0092] (1) Dissolve glycine in an aqueous solution and stir for 10 min at room temperature (25°C) and speed (400 r / min). The concentration of glycine is 0.5 mol / L.

[0093] (2) Add manganese chloride to the solution prepared in step (1) in 10 portions. After each addition, stir for 10 minutes at room temperature (25°C) and speed (400 r / min). The concentration of manganese chloride is 0.5 mol / L.

[0094] (3) Add potassium chloride to the solution prepared in step (2) in 10 portions. After each addition, stir for 15 minutes at a temperature of 55℃ and a speed of 400r / min, and then cool to room temperature. The concentration of potassium chloride is 1mol / L.

[0095] Preparation method of negative electrode electrolyte:

[0096] (1) Dissolve TiOSO4 in an aqueous solution and stir for 300 min at room temperature (25°C) and speed (400 r / min). The concentration of TiOSO4 is 0.5 mol / L.

[0097] (2) Add sulfuric acid to the solution prepared in step (1) in 10 portions. After each addition, stir for 10 minutes at room temperature (25°C) and speed (400 r / min). The sulfuric acid concentration is 1 mol / L.

[0098] Test Example 1

[0099] Assembly of flow single cells:

[0100] The structure of a single cell includes an end plate, a graphite current collector, and a diameter of 6×6cm. 2 The invention comprises carbon felt (as positive and negative electrodes), a diaphragm (composite membrane), a flow frame, a silicone pad, positive and negative electrode electrolyte storage tanks and pumps, and piping. The diaphragm in this invention is a composite membrane composed of a polyolefin porous membrane and an ion exchange resin, which is significantly cheaper and has superior performance than conventional Nafion membranes.

[0101] The performance of the batteries obtained in Examples 1-19 and Comparative Examples 1-3 was tested. The test conditions were as follows: the flow rate of the electrolyte (positive and negative electrode electrolytes) in the battery was 50 mL / min, and the charging current was 20 mA / cm.2 Charging cutoff capacity 2mA·h / cm 2 The discharge cutoff voltage was 1.0V. The average values ​​of coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) were measured during the first 100 charge-discharge cycles, and the results are shown in Table 1.

[0102] Table 1 Battery performance of Examples 1-19 and Comparative Examples 1-3

[0103]

[0104]

[0105] Results analysis:

[0106] Figure 1 To illustrate the phenomena observed after charging of the zinc-manganese redox flow batteries obtained in Comparative Example 1 and Example 1, ac represents the electrolyte after charging in the system without additives (Comparative Example 1), the starch-potassium iodide test paper at the bottle neck, and the electrolyte after charging with added Mn, respectively. 3+ The phenomenon observed with the indicator (sodium pyrophosphate). The values ​​df represent the electrolyte after charging (with added glycine, Example 1), the starch-potassium iodide test paper at the bottle mouth, and the electrolyte after charging with added Mn, respectively. 3+ The phenomenon observed with the indicator (sodium pyrophosphate). It can be seen that Mn is generated after charging in the system without additives. 3+ The presence of Cl2 causes color changes in both the electrolyte and the test paper. In contrast, the addition of glycine inhibits the reaction of Mn. 3+ It reacts with Cl2 to form a solution that keeps the solution and test paper colorless.

[0107] Figure 2 The capacity and coulombic efficiency graphs of the zinc-manganese flow batteries obtained in Comparative Example 1 and Example 1 show that 20 mA / cm²... 2 At current density, 2 mA h / cm 2 At the charging cutoff capacity, the battery with added glycine (Example 1) can achieve a discharge capacity of 1000 cycles without significant decay, while the system without added complexing agent (Comparative Example 1) has a severe discharge capacity decay after 150 cycles and a coulombic efficiency of only 58.53%.

[0108] Examples 1-3 demonstrate that the amount of additive also affects the chemical reaction of the manganese couple. In Examples 1-3, the highest coulombic efficiency, voltage efficiency, and energy efficiency were achieved when the additive concentration was 0.5 mol / L, which were 98.44%, 83.44%, and 82.13%, respectively (Table 1).

[0109] Figure 3The battery performance was compared when the initial electrolyte was 0.5 mol / L manganese chloride + 0.5 mol / L zinc chloride + 1 mol / L KCl, and glycine (Example 1), alanine (Example 4), valine (Example 5), arginine (Example 6), lysine (Example 7), and valine + arginine (Example 8) were added as additives. It can be seen that the energy efficiency and coulombic efficiency were the highest when glycine was used as the additive.

[0110] Examples 1, 9, and 10 show the effect of positive electrode active material concentration on battery performance. Low concentration limits battery life, while high concentration affects electrolyte viscosity. The optimal manganese chloride concentration is 0.5 mol / L (Table 1).

[0111] Examples 1, 11, and 12 show the effect of negative electrode active material concentration on battery performance. Low concentration limits battery life, while high concentration affects electrolyte viscosity. The optimal zinc chloride concentration is 0.5 mol / L (Table 1).

[0112] By comparing the battery performance obtained in Examples 1, 13, 14 and 15, KCl was selected as the optimal supporting electrolyte, which has higher energy efficiency and coulombic efficiency (Table 1).

[0113] Examples 1, 16, and 17 show the effect of electrolyte concentration on battery performance. Low concentration reduces electrolyte conductivity, while high concentration affects electrolyte viscosity. The preferred KCl concentration is 0.5 mol / L (Table 1).

[0114] Figure 4 This is a performance comparison chart of the copper-manganese flow batteries assembled in Comparative Example 2 (no additives) and Example 18 (with glycine) and the titanium-manganese flow batteries assembled in Comparative Example 3 (no additives) and Example 19 (with glycine). It can be seen that the amino acid additive significantly improves the battery performance and stability. This indicates that the electrolyte of the present invention is effective in different systems, resulting in good battery performance.

Claims

1. A manganese chloride electrolyte, characterized in that: The manganese chloride electrolyte comprises an active substance and an amino acid additive; the amino acid additive is selected from one or more of glycine, alanine, valine, arginine, lysine, and proline; the active substance is manganese chloride.

2. The manganese chloride electrolyte according to claim 1, characterized in that: The concentration of the active substance is 0.01-6.42 mol / L; the concentration of the additive is 0.01-5 mol / L.

3. The manganese chloride electrolyte according to claim 1, characterized in that: The electrolyte also contains a supporting electrolyte, the concentration of which is 0.01-3 mol / L; The supporting electrolyte is one or more of KCl, K2SO4, NaCl, and Na2SO4.

4. A method for preparing the manganese chloride electrolyte according to any one of claims 1-3, characterized in that: The method includes the following steps: (1) Dissolve the amino acid additive in an aqueous solution and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved; (2) Add manganese chloride to the solution prepared in step (1) and stir at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved.

5. The preparation method according to claim 4, characterized in that: The method further includes: adding the supporting electrolyte to the solution prepared in step (2), stirring at 5-85℃ and 200-1500r / min for 2-300min until completely dissolved, and then cooling the solution to room temperature.

6. The application of the manganese chloride electrolyte according to any one of claims 1-3 in a manganese-based flow battery.

7. The application according to claim 6, characterized in that: The manganese-based flow battery is composed of a stack consisting of one or more single cells connected in series and / or in parallel. Each single cell includes a positive electrode plate, a positive current collector, a positive electrode, a separator, a negative electrode, a negative current collector, a negative electrode plate, a positive electrolyte storage tank containing positive electrolyte, a negative electrolyte storage tank containing negative electrolyte, and a pump.

8. The application according to claim 7, characterized in that: The positive electrode electrolyte is the manganese chloride electrolyte; The negative electrode electrolyte is an aqueous solution containing a negative electrode active material with a concentration of 0.01-6 mol / L.

9. The application according to claim 7, characterized in that: The positive and negative electrode electrolytes can have the same composition. The manganese chloride electrolyte is used as the positive and negative electrode electrolytes after dissolving the negative electrode active material. The concentration of the negative electrode active material is 0.01-6 mol / L.

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