Aqueous iron-cerium flow battery electrolyte and preparation method thereof

Abstract

The invention relates to an aqueous iron-cerium flow battery electrolyte and a preparation method thereof, and belongs to the technical field of flow battery energy storage, in the electrolyte, the main component is an iron-containing salt, and the cerium-containing salt is respectively coordinated with N-(phosphonomethyl) iminodiacetic acid hydrate (PMIDA) and N-bis (phosphonohydroxymethyl) glycine (PAMG) or derivative chemicals thereof to form an aqueous solution of a coordination compound. PMIDA and PAMG have a plurality of functional groups such as carboxylic acid, phosphonic acid and amino, and can form stable polydentate coordination with metal ions, so that the stability of the coordination compound can be enhanced. And positive and negative electrolytes adopt the same chelating agent, so that cross contamination is reduced, the stability of the electrolytes can be ensured, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The invention relates to liquid flow battery energy storage technology, specifically to a preparation method of a novel aqueous iron-cerium liquid flow battery electrolyte, which can be applied in electric vehicles, backup power supplies and large-scale energy storage fields, etc. Background Art

[0002] Due to the excessive use of fossil energy, the world is facing serious climate warming and energy crisis. Increasing the proportion of clean renewable energy generation, such as hydropower, geothermal, solar energy and wind energy, can effectively alleviate these problems. As the main renewable energy sources, the average annual growth rate of solar energy and wind energy installed capacity reached 60% and 20% respectively. However, the generation of solar energy and wind energy is affected by time and weather, and there will be fluctuations, resulting in unstable power generation capacity, which makes it difficult to connect renewable energy to the grid, and then causes a large number of abandoned light and wind. Energy storage technology can provide stable power output and significantly improve the utilization efficiency of photovoltaic and wind energy. Therefore, stable, efficient and economical large-scale energy storage technology is of great significance in the application of renewable energy and the adjustment of energy structure.

[0003] Liquid flow batteries are particularly suitable for long-term energy storage due to their independent power and energy design, high safety and long cycle life. Among them, all-vanadium liquid flow batteries are the most mature technology and are in the commercialization and industrialization stage. However, the relatively high cost of vanadium electrolytes has limited their widespread application to a certain extent.

[0004] In recent decades, various flow batteries based on iron compounds have been developed due to the abundance of iron resources and low cost. The flow batteries that have been studied more and are relatively mature include iron-chromium flow batteries, zinc-bromine flow batteries, zinc-iron flow batteries, and all-iron flow batteries. The positive and negative electrodes of all-iron flow batteries both use iron ions as the active material of the electrolyte, which reduces the cost. However, iron ions have problems in hydrolysis and deposition / dissolution reactions, which limits their cycle stability, resulting in low efficiency of all-iron flow batteries and more serious capacity decay. In the present invention, the coordination compound formed by the coordination of cerium salt with N-(phosphonomethyl)iminodiacetic acid hydrate (PMIDA) and N-bis(phosphinomethyl)glycine (PAMG) or its derivative chemicals is the positive electrode electrolyte, and the coordination compound formed by the coordination of iron salt with PMIDA and PAMG or their derivative chemicals is the negative electrode electrolyte, which is assembled with electrodes, diaphragms, storage tanks, pumps and pipelines to form an iron-cerium flow battery. At the same time, the positive and negative electrodes of the present invention use the same ligand, which enhances the cycle stability of the battery and increases the service life of the battery. Summary of the invention

[0005] In this method, a proper chelating agent is added and the coordination environment is adjusted. PMIDA and the carboxylic acid, phosphonic acid and amino groups in PAMG have good water solubility and can react in the aqueous phase to make them react with Ce.3+ / Ce 4+ , Fe 3+ / Fe 2+ The coordination compounds are formed. PMIDA and PAMG have multiple functional groups such as (carboxylic acid, phosphonic acid and amino group), which can form stable multidentate coordination with metal ions, which can enhance the stability of the coordination compounds.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A water-based iron-cerium liquid flow battery electrolyte, characterized in that the solute of the positive electrode electrolyte includes a cerium salt, a chelating agent, a supporting electrolyte, and an auxiliary electrolyte; the solute of the negative electrode electrolyte includes an iron salt, a chelating agent, a supporting electrolyte, and an auxiliary electrolyte; the chelating agents described in the positive and negative electrode electrolytes are selected from one or more of N-(phosphonomethyl)iminodiacetic acid hydrate (PMIDA) and its derivative chemicals, N-bis(phosphinohydroxymethyl)glycine (PAMG) or its derivative chemicals.

[0008] The concentrations of the iron salt and the cerium salt are both 0.001 to 2 mol / L, preferably 0.2 to 1.5 mol / L; the concentrations of the chelating agent are both 0.001 to 4 mol / L, preferably 0.4 to 2 mol / L; the concentrations of the supporting electrolyte are both 0.001 to 8 mol / L, preferably 1 to 4 mol / L; the concentrations of the auxiliary electrolyte are both 0.001 to 2 mol / L, preferably 0.2 to 1 mol / L.

[0009] The cerium salt is Ce 3+ or / and Ce 4+ The salt is preferably one or more of cerium sulfate, cerium acetate, cerium nitrate, cerium trichloride, and cerium oxalate.

[0010] The iron salt is Fe 3+ or / and Fe 2+ The salt is preferably one or more of ferric sulfate, ferric nitrate, ferric chloride and ferric acetate.

[0011] The derivatives of PMIDA include dihexyl N-(phosphonomethyl)iminodiacetate, sodium N-(phosphonomethyl)iminodiacetate, potassium N-(phosphonomethyl)iminodiacetate; the derivatives of PAMG include sodium N-bis(phosphonomethyl)glycinate, potassium N-bis(phosphonomethyl)glycinate.

[0012] The supporting electrolyte includes, but is not limited to, one or more of potassium carbonate, sodium carbonate, lithium carbonate, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0013] The auxiliary electrolyte includes, but is not limited to, one or more of potassium chloride, potassium nitrate, sodium nitrate, sodium chloride, ammonium chloride, potassium sulfate, sodium sulfate, and ammonium sulfate.

[0014] The method for configuring an electrolyte solution is characterized in that the negative electrode electrolyte configuration method comprises the following steps:

[0015] Nitrogen was introduced into the reactor to exhaust the air, and iron salt, chelating agent, supporting electrolyte and auxiliary electrolyte were added. After mixing, deionized water was added and stirred for 3 to 6 hours to make a uniform solution. The solution was transferred to a volumetric flask and allowed to stand for 24 hours before use.

[0016] The method of preparing the positive electrode electrolyte is the same as above, except that the iron salt is replaced with a cerium salt.

[0017] The pH of the positive and negative electrolytes mentioned above are both 6-8.

[0018] The operating temperature of the positive and negative electrolytes is 10-70°C.

[0019] Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

[0020] 1. Chelating agents PMIDA and PAMG Due to the asymmetry of their structures, the molecules can form multiple hydrogen bonds and other interactions (such as van der Waals forces) with the surrounding water molecules, which enhances the interaction with water and thus improves solubility.

[0021] 2. The present invention improves the stability of the electrolyte under mild pH conditions, keeps the solution in a uniform state, and does not precipitate iron hydroxide, thereby effectively improving the operating stability and cycle life of the battery.

[0022] 3. The iron and cerium used in the present invention are both relatively abundant and low-cost materials. Compared with the raw materials of all-vanadium liquid flow batteries, the raw materials of iron-cerium liquid flow batteries are easier to obtain, and the electrolyte configuration method is simple, thereby reducing production costs.

[0023] In summary, the iron-cerium liquid flow battery of the present invention has low cost and exhibits good cycle stability, can withstand multiple charges and discharges, prolongs service life, reduces maintenance and replacement costs, and is suitable for large-scale energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the cyclic voltammetry curve of the positive electrode electrolyte in Example 1.

[0025] Figure 2 This is the cyclic voltammetry curve of the negative electrode electrolyte of Example 1.

[0026] Figure 3 The charge and discharge capacity-cycle curve of Example 1 within 330 cycles.

[0027] Figure 4 This is the charge and discharge efficiency-cycle curve within 330 cycles of Example 1.

[0028] Table 1 is a comparison of the battery test results of various embodiments. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through specific examples, but the use and purpose of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, nor limit the protection scope of the present invention to these.

[0030] Embodiment 1:

[0031] This embodiment provides a novel method for preparing an aqueous iron-cerium liquid flow battery electrolyte, wherein the solute of the positive electrode electrolyte includes cerium chloride with a concentration of 0.2 mol / L, PMIDA with a concentration of 1 mol / L, anhydrous potassium carbonate with a concentration of 1.5 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; wherein the solute of the negative electrode electrolyte includes ferric chloride with a concentration of 0.2 mol / L, PMIDA with a concentration of 1 mol / L, anhydrous potassium carbonate with a concentration of 1.5 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; the configuration method of the positive electrode electrolyte is as follows:

[0032] The configuration method of the positive electrode electrolyte is as follows:

[0033] Weigh 7.45g of cerium chloride, 22.7g of PMIDA, 20.75g of anhydrous potassium carbonate, and 3g of potassium chloride into a reactor, add 90ml of deionized water, stir at 20°C for 1h to make a solution, make the volume to 100ml, transfer to a volumetric flask, and let it stand for 24h before use.

[0034] The configuration method of the negative electrode electrolyte is as follows:

[0035] Weigh 5.4 g of ferric chloride, 22.7 g of PMIDA, 20.75 g of anhydrous potassium carbonate, and 3 g of potassium chloride and put them into a reactor. Add 90 ml of deionized water and stir at 20 °C for 1 h to make a solution. Make the solution up to 100 ml and transfer it to a volumetric flask. Let it stand for 24 h before use.

[0036] The above electrolyte was subjected to electrochemical testing, and the results were as follows: Figure 1 , Figure 2 As shown, it has good reversibility.

[0037] Add the positive and negative electrolytes to the corresponding liquid storage tanks of the liquid flow battery. The liquid flow battery system mainly consists of batteries, positive and negative liquid storage tanks, positive and negative peristaltic pumps, corrosion-resistant circulation pipelines, and battery testing systems. The battery components include: aluminum end plates, polytetrafluoroethylene gaskets, collector plates, graphite bipolar plates, fluororubber gaskets, proton exchange membranes, and graphite felt electrodes. The graphite felt electrode is 3cm×3cm, and the proton exchange membrane is Nafion 212.

[0038] After the above components are assembled, inert gas is circulated in the battery system to prevent the active substances from being deactivated. Then the battery test system is connected to start the test.

[0039] The volume of positive and negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 Porous carbon felt electrode, proton membrane is Nafion 212 membrane. At 40mA / cm 2 The current density was charged to 0.9V at 40mA / cm 2 Discharge to 0.01V at a current density of .

[0040] Figure 3 The charge and discharge capacity-cycle curve of this embodiment within 330 cycles is gradually stable; Figure 4 This is the charge and discharge efficiency-cycle curve within 330 cycles of this embodiment. The coulomb efficiency (CE) is stable at about 90%, and the voltage efficiency (VE) and energy efficiency (EE) are stable at about 60%.

[0041] Embodiment 2:

[0042] This embodiment provides a novel method for preparing an aqueous iron-cerium liquid flow battery electrolyte, wherein the solute of the positive electrode electrolyte includes cerium chloride with a concentration of 0.4 mol / L, PMIDA with a concentration of 1.5 mol / L, anhydrous potassium carbonate with a concentration of 3 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; wherein the solute of the negative electrode electrolyte includes ferric chloride with a concentration of 0.4 mol / L, PMIDA with a concentration of 1.5 mol / L, anhydrous potassium carbonate with a concentration of 3 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; the configuration method of the positive electrode electrolyte is as follows:

[0043] The configuration method of the positive electrode electrolyte is as follows:

[0044] Weigh 14.9 g of cerium chloride, 34.07 g of PMIDA, 41.46 g of anhydrous potassium carbonate, and 3 g of potassium chloride into a reactor, add 90 ml of deionized water, stir at 20°C for 1 h to make a solution, make the volume to 100 ml, transfer to a volumetric flask, and let it stand for 24 h before use.

[0045] The configuration method of the negative electrode electrolyte is as follows:

[0046] Weigh 10.8 g of ferric chloride, 37.07 g of PMIDA, 41.46 g of anhydrous potassium carbonate, and 3 g of potassium chloride and put them into a reactor. Add 90 ml of deionized water and stir at 20 °C for 1 h to make a solution. Make the solution up to 100 ml and transfer it to a volumetric flask. Let it stand for 24 h before use.

[0047] After the battery system is assembled, other reference conditions are the same as those in Example 1. To prevent the active material from being deactivated, wait until the inert gas fills the entire battery system. Connect to the battery test system and start testing.

[0048] The volume of the negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 Porous carbon felt electrode, proton membrane is Nafion212 membrane. At 80mA / cm 2 The current density was charged to 0.9V at 80mA / cm 2 The battery was discharged to 0.01 V at a current density of . The efficiency results are shown in Table 1.

[0049] Embodiment 3:

[0050] This embodiment provides a novel method for preparing an aqueous iron-cerium liquid flow battery electrolyte, wherein the solute of the positive electrode electrolyte includes cerium chloride with a concentration of 0.2 mol / L, PAMG with a concentration of 1 mol / L, anhydrous potassium carbonate with a concentration of 1.5 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; wherein the solute of the negative electrode electrolyte includes ferric chloride with a concentration of 0.2 mol / L, PAMG with a concentration of 1 mol / L, anhydrous potassium carbonate with a concentration of 1.5 mol / L, and potassium chloride with a concentration of 0.4 mol / L, and the solvent is deionized water; the configuration method of the positive electrode electrolyte is as follows:

[0051] The configuration method of the positive electrode electrolyte is as follows:

[0052] Weigh 7.45g of cerium chloride, 26.31g of PAMG, 20.75g of anhydrous potassium carbonate, and 3g of potassium chloride into a reactor, add 90ml of deionized water, stir at 20°C for 1h to make a solution, dilute to 100ml, transfer to a volumetric flask, and let stand for 24h before use.

[0053] The configuration method of the negative electrode electrolyte is as follows:

[0054] Weigh 5.4 g of ferric chloride, 26.31 g of PAMG, 20.75 g of anhydrous potassium carbonate, and 3 g of potassium chloride and put them into a reactor. Add 90 ml of deionized water and stir at 20 °C for 1 h to make a solution. Make the solution up to 100 ml and transfer it to a volumetric flask. Let it stand for 24 h before use.

[0055] After the battery system is assembled, other reference conditions are the same as those in Example 1. To prevent the active material from being deactivated, wait until the inert gas fills the entire battery system. Connect to the battery test system and start testing.

[0056] The volume of positive and negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 Porous carbon felt electrode, proton membrane is Nafion 212 membrane. At 40mA / cm 2 The current density was charged to 0.9V at 40mA / cm 2 The battery was discharged to 0.01 V at a current density of . The efficiency results are shown in Table 1.

[0057] Table 1 Comparison of battery test results of various embodiments (330 cycles)

[0058] sample CE / % VE / % EE / % Example 1 92.2 64.1 59.1 Example 2 95.3 58.8 56.0 Example 3 88.3 63.9 56.4 .

Claims

1. An aqueous iron-cerium liquid flow battery electrolyte, characterized in that: The solutes of the positive electrode electrolyte include cerium salt, chelating agent, supporting electrolyte, and auxiliary electrolyte; the solutes of the negative electrode electrolyte include iron salt, chelating agent, supporting electrolyte, and auxiliary electrolyte; the chelating agents described in the positive and negative electrode electrolytes are selected from one or more of N-(phosphonomethyl)iminodiacetic acid hydrate (PMIDA) and its derivative chemicals, N-bis(phosphonohydroxymethyl)glycine (PAMG) or its derivative chemicals.

2. An aqueous iron-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The concentrations of the iron salt and the cerium salt are both 0.001 to 2 mol / L, preferably 0.2 to 1.5 mol / L; the concentration of the chelating agent is 0.001 to 4 mol / L, preferably 0.4 to 2 mol / L; the concentration of the supporting electrolyte is 0.001 to 8 mol / L, preferably 1 to 4 mol / L; the concentration of the auxiliary electrolyte is 0.001 to 2 mol / L, preferably 0.2 to 1 mol / L.

3. An aqueous iron-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The cerium salt is Ce 3+ or / and Ce 4+ The salt is preferably one or more of cerium sulfate, cerium acetate, cerium nitrate, cerium trichloride, and cerium oxalate.

4. The aqueous iron-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The iron salt is Fe 3+ or / and Fe 2+ The salt is preferably one or more of ferric sulfate, ferric nitrate, ferric chloride and ferric acetate.

5. The aqueous iron-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The derivatives of PMIDA include dihexyl N-(phosphonomethyl)iminodiacetate, sodium N-(phosphonomethyl)iminodiacetate, potassium N-(phosphonomethyl)iminodiacetate; the derivatives of PAMG include sodium N-bis(phosphonomethyl)glycinate, potassium N-bis(phosphonomethyl)glycinate.

6. The aqueous iron-cerium liquid flow battery electrolyte according to claim 1, characterized in that: Supporting electrolytes include, but are not limited to, one or more of potassium carbonate, sodium carbonate, lithium carbonate, lithium hydroxide, sodium hydroxide, and potassium hydroxide; The auxiliary electrolyte includes, but is not limited to, one or more of potassium chloride, potassium nitrate, sodium nitrate, sodium chloride, ammonium chloride, potassium sulfate, sodium sulfate, and ammonium sulfate. The pH of the positive and negative electrolytes mentioned above are both 6-8.

7. A method for preparing an aqueous iron-cerium liquid flow battery electrolyte according to any one of claims 1 to 6, characterized in that: The negative electrode electrolyte configuration method comprises the following steps: Into the reactor, nitrogen is introduced to exhaust the air, iron salt, chelating agent, supporting electrolyte, auxiliary electrolyte are added, deionized water is added after mixing, and the mixture is stirred for 3 to 6 hours to form a uniform solution, which is transferred to a volumetric flask and allowed to stand for 24 hours before use; The method of preparing the positive electrode electrolyte is the same as above, except that the iron salt is replaced with a cerium salt.

8. Use of an aqueous iron-cerium liquid flow battery electrolyte as described in any one of claims 1-6 for an aqueous iron-cerium liquid flow battery, wherein the operating temperature of the positive and negative electrolytes is 10 to 70°C.

9. An aqueous iron-cerium liquid flow battery, characterized in that: An aqueous iron-cerium liquid flow battery electrolyte comprising any one of claims 1-6.

Images