High-stability iron-cerium flow battery and preparation method of electrolyte

Abstract

The invention discloses a high-stability iron-cerium flow battery and a preparation method of electrolyte, and belongs to the technical field of flow batteries. A positive electrolyte and a negative electrolyte are cerium salt and ferric salt, and are respectively mixed with nitrilotriacetic acid, ethylenediamine tetraacetic acid, trans-1, 2-cyclohexanediamine tetraacetic acid, 1, 3-propane diamine tetraacetic acid, N-(2-ethoxyl) ethylenediamine-N, N ', N'-triacetic acid, iminodiacetic acid, iminodisuccinic acid, succinic acid, N, N '-bis (2-hydroxyethyl)-N, N', N '-triacetic acid and N, N'-bis (2-hydroxyethyl)-N, N '-bis (2-hydroxyethyl)-N, N'-bis (2-hydroxyethyl)- N, N '-ethylenediamine disuccinic acid, aspartic acid or a derivative chemical thereof are coordinated to form an aqueous solution of the coordination compound. The positive electrolyte and the negative electrolyte are prepared from the same and equal chelating agent and supporting electrolyte, and the matching degree of the acid-base property of the positive electrolyte and the negative electrolyte is maintained; the auxiliary electrolyte is added, so that the viscosity difference between the positive electrolyte and the negative electrolyte is reduced, the transmembrane migration of water is reduced, and the conductivity is improved. The selected chelating agent is stably combined with iron and cerium, transmembrane transportation of active substances is inhibited, ion cross contamination among different electrolytes is reduced, and meanwhile side reactions are reduced. The price is low, and the charge-discharge performance and the cycle life of the iron-cerium flow battery are effectively improved at relatively low cost.

Description

Technical Field

[0001] The present invention relates to the field of liquid flow battery energy storage technology, specifically a method for preparing a high-stability iron-cerium liquid flow battery and an electrolyte. The battery assembled using the electrolyte can be used in a neutral environment, and can not only be used as a supporting energy storage device in the process of solar and wind power generation, but can also be used in the energy management of smart cities and combined with new power vehicles. Background Art

[0002] Due to the intermittent nature of renewable energy, energy storage devices become necessary to balance the uneven supply and demand. With the development of low-cost, high-efficiency and long-cycle life energy storage technology, the application of renewable energy in the power grid will increase significantly. Among the feasible grid energy storage technologies, redox flow batteries are widely regarded as the most suitable choice. A flow battery is an electrochemical cell that converts chemical energy into electrical energy by flowing an electrolyte solution over the surface of an electrode. On the electrode surface, redox substances undergo oxidation and reduction reactions. The flow battery is divided into two half-cells by an ion exchange membrane, which allows specific ions to pass through to balance the charge while preventing the passage of active substances. In the half-cell containing the positive electrode, the electrolyte is called the positive electrolyte, while in the half-cell containing the negative electrode, it is called the negative electrolyte. Through the flow of electrolytes, redox reactions and ion exchange, electrons are driven through an external circuit to achieve the storage and release of electrical energy.

[0003] Liquid flow batteries have the characteristics of high safety, independent design of output power and energy storage capacity, and environmental friendliness. The currently more mature all-vanadium liquid flow batteries still have disadvantages such as high one-time investment, serious crossover of active substances, and rapid performance decay. Other zinc, iron and other mixed liquid flow batteries have defects such as metal dendrites and serious side reactions. Moreover, during the charging and discharging process, there is an asymmetric water crossover, and water molecules migrate across the membrane to dilute the electrolyte of one half of the battery, thereby increasing the ion concentration in the other half of the battery, ultimately causing an imbalance in the electrolyte and reducing the stability and cycle life of the battery. Summary of the invention

[0004] In view of the problems existing in the above-mentioned flow batteries, the present invention provides a method for preparing a high-stability iron-cerium flow battery and an electrolyte, selects a chelating agent with strong chelating ability and low price, uses the same amount of chelating agent to combine the positive and negative electrode active substances, the chelate molecular size is large, and cross contamination is reduced, and the same amount of supporting electrolyte is used to adjust the acid-base matching, and the same auxiliary electrolyte is used to improve the conductivity. This can reduce the transmembrane migration of water, greatly improve the cycle stability of the flow battery, and maintain a high energy efficiency. The high-stability iron-cerium flow battery can be used as a supporting energy storage device in the process of solar and wind power generation, and can also be used in the energy management of smart cities and combined with new power vehicles.

[0005] The present invention adopts the following technical solution:

[0006] A high-stability iron-cerium liquid flow battery and a method for preparing an electrolyte, characterized in that: the positive electrode electrolyte comprises a cerium salt, a chelating agent, a supporting electrolyte, an auxiliary electrolyte, and oxygen-free deionized water. The negative electrode electrolyte comprises an iron salt, a chelating agent, a supporting electrolyte, an auxiliary electrolyte, and oxygen-free deionized water.

[0007] The selected cerium salt is one or more of cerium sulfate, cerium carbonate, cerium acetate, cerium nitrate, cerium trichloride, and cerium oxalate, and the selected iron salt is one or more of ferric chloride, ammonium ferric sulfate, ferric sulfate, ferric nitrate, and ferric acetate. The selected chelating agent is at least one of aminotriacetic acid, ethylenediaminetetraacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, 1,3-propylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, iminodiacetic acid, iminodisuccinic acid, succinic acid, N,N'-ethylenediaminedisuccinic acid, aspartic acid, or its derivative chemicals.

[0008] The selected supporting electrolyte is one or more of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, potassium hydroxide, sodium hydroxide and lithium hydroxide.

[0009] The selected auxiliary electrolyte is one or more of sodium chloride, sodium sulfate, sodium nitrate, potassium chloride, potassium sulfate, potassium nitrate, ammonium chloride, ammonium sulfate, and ammonium carbonate.

[0010] A high-stability iron-cerium liquid flow battery and a method for preparing an electrolyte, characterized in that the concentration of the selected iron salt and cerium salt is 0.01 to 1.5 mol / L, preferably 0.2 to 1.0 mol / L.

[0011] The molar ratio of the selected chelating agent to the iron salt and the cerium salt is (1-3):1, preferably 2:1.

[0012] The selected electrolyte concentration is 0.01 to 8 mol / L, preferably 1.0 to 4 mol / L.

[0013] The selected auxiliary electrolyte concentration is 0-1.5 mol / L, preferably in the range of 0.3-0.8 mol / L.

[0014] A high-stability iron-cerium liquid flow battery and a method for preparing an electrolyte, characterized in that the pH of the electrolyte is 4 to 9, preferably 6.5 to 7.5.

[0015] The concentration of cerium in the positive electrode electrolyte is the same as the concentration of iron in the negative electrode electrolyte. The chelating agent, supporting electrolyte and auxiliary electrolyte in the positive electrode electrolyte are the same as the chelating agent, supporting electrolyte and auxiliary electrolyte in the negative electrode electrolyte and have the same corresponding concentrations. The volume of the positive electrode electrolyte is the same as that of the negative electrode electrolyte.

[0016] The iron-cerium liquid flow battery negative electrode electrolyte is characterized in that the preparation method comprises the following steps:

[0017] 1) Add iron salt and chelating agent into a reactor containing oxygen-free deionized water, heat to 20-100° C., and stir for 2-10 hours.

[0018] 2) After that, the supporting electrolyte and the auxiliary electrolyte are added into the reactor, heated to 20-100°C, stirred for 2-10 hours, fixed to volume, and allowed to stand.

[0019] 3) Adjust the pH to obtain the required electrolyte.

[0020] The positive electrode electrolyte of the iron-cerium liquid flow battery according to claim 1 is characterized in that the preparation method comprises the following steps:

[0021] 1) Add cerium salt and chelating agent into a reactor containing oxygen-free deionized water, heat to 20-100° C., and stir for 2-10 hours.

[0022] 2) Afterwards, the supporting electrolyte and the auxiliary electrolyte are added into the reactor, heated to 20 to 100° C., and stirred for 2 to 10 hours.

[0023] 3) Adjust the pH to obtain the required electrolyte.

[0024] A high-stability iron-cerium liquid flow battery and a method for preparing an electrolyte, wherein the electrolyte has a use temperature of 10 to 70°C.

[0025] A high-stability iron-cerium liquid flow battery comprises the positive and negative electrolytes, the positive electrode, the negative electrode and the diaphragm. The electrodes and the electrolyte are separated by the diaphragm into two positive and negative chambers, and the electrolyte is transported and circulated by a pump.

[0026] A high-stability iron-cerium liquid flow battery, wherein the positive electrode or negative electrode material is a porous carbon material electrode, selected from one of carbon felt, graphite felt, graphite plate, graphite paper, carbon paper, and carbon cloth inert materials. The diaphragm is a Nafion membrane, selected from one of Nafion117, Nafion115, Nafion212, and Nafion211.

[0027] Beneficial results of the present invention:

[0028] 1. The chelating agent in the present invention has low cost, strong chelating ability, and stabilizes the two active substances of iron and cerium. The formed chelate molecule has a highly efficient coordination structure with reversibility and stability. This inhibits the crossover of active ions and improves the cycle stability and energy efficiency of the battery.

[0029] 2. In the present invention, the positive and negative electrolytes are prepared with the same amount of chelating agent and supporting electrolyte, and the auxiliary electrolyte is used to improve the conductivity. This helps to reduce the viscosity difference between the positive and negative electrolytes, ensure the matching degree of the acidity and alkalinity of the positive and negative electrolytes, and reduce the transmembrane migration of water.

[0030] 3. The iron-cerium liquid flow battery of the present invention has a high capacity retention rate in terms of cycle stability, can be used in a neutral environment, and has low requirements for equipment and materials. At low cost, it can not only be used as a supporting energy storage device in the process of solar and wind power generation, but also can be used in the energy management of smart cities and combined with new power vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The negative electrode electrolyte of Example 1 is 10-50 mV·s -1 Cyclic voltammetry curves inside.

[0032] Figure 2 The positive electrode electrolyte of Example 1 is 10-50 mV·s -1 Cyclic voltammetry curves inside.

[0033] Figure 3 The charge and discharge efficiency-cycle curve of Example 1 within 1 to 200 cycles.

[0034] Figure 4 The charge and discharge capacity-cycle curves of Example 1 within 1 to 200 cycles.

[0035] Table 1 is a comparison of the battery test results of various embodiments. DETAILED DESCRIPTION

[0036] 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.

[0037] Embodiment 1:

[0038] In this embodiment, the main components of the negative electrode electrolyte include: ferric chloride, aminotriacetic acid, the supporting electrolyte is potassium carbonate, the auxiliary electrolyte is sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of ferric chloride is 0.2 mol / L, the concentration of aminotriacetic acid is 0.4 mol / L, the concentration of potassium carbonate is 0.6 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0039] The specific steps for configuring the negative electrode electrolyte are as follows:

[0040] Nitrogen was introduced into the reactor to exhaust the air, 5.4 g of ferric chloride and 7.7 g of aminotriacetic acid were mixed and added to the reactor containing oxygen-free deionized water, heated and stirred, and the heating temperature was set to 90°C for 2 hours. 8.3 g of potassium carbonate and 2.9 g of sodium chloride were mixed and added, and oxygen-free deionized water was added after mixing, and stirred for 6 hours to make a uniform solution, which was fixed to 100 mL, left to stand for 24 hours, and the pH was adjusted to about 7.

[0041] The main components of the positive electrode electrolyte include: cerium chloride, aminotriacetic acid, supporting electrolyte is potassium carbonate, auxiliary electrolyte is sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of cerium chloride is 0.2 mol / L, the concentration of aminotriacetic acid is 0.4 mol / L, the concentration of potassium carbonate is 0.6 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0042] The specific steps for configuring the positive electrode electrolyte are as follows:

[0043] Nitrogen was introduced into the reactor to exhaust the air, 7.5g of cerium chloride and 7.7g of aminotriacetic acid were mixed and added to the reactor containing oxygen-free deionized water, heated and stirred, and the heating temperature was set to 90°C for 2 hours. 8.3g of potassium carbonate and 2.9g of sodium chloride were mixed and added, and oxygen-free deionized water was added after mixing, and stirred for 6 hours to make a uniform solution, which was fixed to 100mL, left to stand for 24 hours, and the pH was adjusted to about 7.

[0044] The above negative electrode and positive electrode electrolytes were subjected to electrochemical tests, and the results are as follows: Figure 1 , 2 The cyclic voltammetry curve is scanned at a scan rate of 10 to 50 mV / s. The curve is symmetrical, the peak ratio of the oxidation peak to the reduction peak is close to 1, and it has good reversibility, and the peak potential difference is small, and the activation energy required for the reaction is less.

[0045] The above-mentioned negative electrode and positive electrode electrolytes were subjected to battery testing.

[0046] The components of a single cell include aluminum end plates, polytetrafluoroethylene gaskets, collector plates, graphite bipolar plates, graphite felt electrodes, fluororubber gaskets, and proton exchange membranes. Assemble the single cell and form a battery test system with the positive and negative electrode storage tanks, positive and negative electrode peristaltic pumps, and circulation pipelines.

[0047] Prior to testing, an inert gas is circulated through the battery system to prevent deactivation of the active substances.

[0048] The volume of positive and negative electrolyte is 30ml 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 2The battery was discharged to 0.01V at a current density of . After 200 cycles, the charge and discharge were still stable. Figure 3 As shown: In 200 cycles, the CE of the battery remains at about 95%, and the VE and EE remain at about 80%, and the decay is very slow. Figure 4 As shown: After 200 cycles, the capacity dropped from 0.15Ah to 0.10Ah, which is 67% of the original capacity, and the decay is very slow.

[0049] Embodiment 2:

[0050] In this embodiment, the negative electrode electrolyte mainly comprises: ferric chloride, aminotriacetic acid, a supporting electrolyte of potassium carbonate, an auxiliary electrolyte of sodium chloride, and a solvent of oxygen-free deionized water. The concentration of ferric chloride is 0.5 mol / L, the concentration of aminotriacetic acid is 1.0 mol / L, the concentration of potassium carbonate is 1.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0051] The main components of the positive electrode electrolyte include: cerium chloride, aminotriacetic acid, supporting electrolyte is potassium carbonate, auxiliary electrolyte is sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of cerium chloride is 0.5 mol / L, the concentration of aminotriacetic acid is 1.0 mol / L, the concentration of potassium carbonate is 1.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0052] Configuration process reference example 1

[0053] The above electrolytes were subjected to electrochemical and battery tests.

[0054] The volume of positive and negative electrolyte is 30ml each, and the positive and negative electrodes are 3×3cm 2 Porous carbon felt electrode, proton membrane is Nafion 117 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 2.5 %.

[0055] Embodiment 3:

[0056] In this embodiment, the main components of the negative electrode electrolyte include: ferric chloride, ethylenediaminetetraacetic acid, a supporting electrolyte of potassium carbonate, an auxiliary electrolyte of sodium chloride, and a solvent of oxygen-free deionized water. Among them, the concentration of ferric chloride is 0.5 mol / L, the concentration of aminotriacetic acid is 1.0 mol / L, the concentration of potassium carbonate is 1.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0057] The main components of the positive electrode electrolyte include: cerium chloride, ethylenediaminetetraacetic acid, supporting electrolyte is potassium carbonate, auxiliary electrolyte is sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of cerium chloride is 0.5 mol / L, the concentration of aminotriacetic acid is 1.0 mol / L, the concentration of potassium carbonate is 1.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0058] Configuration process reference example 1

[0059] The above electrolytes were subjected to electrochemical and battery tests.

[0060] The volume of positive and negative electrolyte is 30ml each, and the positive and negative electrodes are 3×3cm 2 Porous carbon felt electrode, proton membrane is Nafion 117 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 2.5 %.

[0061] Table 1 is a comparison of the battery test results of each embodiment (first round)

[0062] sample CE / % VE / % EE / % Example 1 93.4 84.2 78.6 Example 2 95.6 74.1 70.8 Example 3 90.6 77.2 69.9 .

Claims

1. A high-stability iron-cerium liquid flow battery, characterized in that: The positive electrode electrolyte comprises cerium salt, chelating agent, supporting electrolyte, auxiliary electrolyte, and oxygen-free deionized water; the negative electrode electrolyte comprises iron salt, chelating agent, supporting electrolyte, auxiliary electrolyte, and oxygen-free deionized water; The selected chelating agent is at least one of aminotriacetic acid, ethylenediaminetetraacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, 1,3-propylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, iminodiacetic acid, iminodisuccinic acid, succinic acid, N,N'-ethylenediaminedisuccinic acid, aspartic acid or its derivative chemicals.

2. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The selected cerium salt is one or more of cerium sulfate, cerium carbonate, cerium acetate, cerium nitrate, cerium trichloride, and cerium oxalate; the selected iron salt is one or more of ferric chloride, ammonium ferric sulfate, ferric sulfate, ferric nitrate, and ferric acetate; The selected supporting electrolyte is one or more of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, potassium hydroxide, sodium hydroxide, and lithium hydroxide; The selected auxiliary electrolyte is one or more of sodium chloride, sodium sulfate, sodium nitrate, potassium chloride, potassium sulfate, potassium nitrate, ammonium chloride, ammonium sulfate, and ammonium carbonate.

3. A high stability iron-cerium liquid flow battery according to claim 1, characterized in that: The concentrations of the selected iron salt and cerium salt are both 0.01-1.5 mol / L, preferably 0.2-1.0 mol / L.

4. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The molar ratio of the chelating agent to the iron salt and the cerium salt is (1-3):1, preferably 2:

1.

5. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The selected electrolyte concentration is 0.01 to 8 mol / L, preferably 1.0 to 4 mol / L; The selected auxiliary electrolyte concentration is 0-1.5 mol / L, preferably in the range of 0.3-0.8 mol / L.

6. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The pH of the electrolyte is 4 to 9, preferably 6.5 to 7.5; the operating temperature of the electrolyte is 10 to 70°C.

7. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The concentration of cerium in the positive electrode electrolyte is the same as the concentration of iron in the negative electrode electrolyte. The chelating agent, supporting electrolyte and auxiliary electrolyte in the positive electrode electrolyte are the same as the chelating agent, supporting electrolyte and auxiliary electrolyte in the negative electrode electrolyte and have the same corresponding concentrations. The volume of the positive electrode electrolyte is the same as that of the negative electrode electrolyte.

8. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The method for preparing the negative electrode electrolyte of the iron-cerium liquid flow battery comprises the following steps: 1) adding iron salt and chelating agent into a reactor containing oxygen-free deionized water, heating the reactor to a temperature of 20 to 100° C., and stirring the reactor for 2 to 10 hours; 2) Then, the supporting electrolyte and the auxiliary electrolyte are added into the reactor, heated to 20 to 100° C., and stirred for 2 to 10 hours; 3) Adjust the pH to obtain the required electrolyte; The method for preparing the positive electrolyte comprises the following steps: 1) adding cerium salt and chelating agent into a reactor containing oxygen-free deionized water, heating the reactor to a temperature of 20 to 100° C., and stirring the reactor for 2 to 10 hours; 2) Then, the supporting electrolyte and the auxiliary electrolyte are added into the reactor, heated to 20 to 100° C., and stirred for 2 to 10 hours; 3) Adjust the pH to obtain the required electrolyte.

9. A high-stability iron-cerium liquid flow battery according to claim 1, characterized in that: The battery comprises the positive and negative electrolytes, the positive electrode, the negative electrode and the diaphragm; the electrodes and the electrolyte are separated into two positive and negative chambers by the diaphragm, and the electrolyte is transported and circulated by a pump.

10. A high-stability iron-cerium liquid flow battery according to claim 9, characterized in that: The positive electrode or negative electrode material is a porous carbon material electrode, selected from one of the inert materials of carbon felt, graphite felt, graphite plate, graphite paper, carbon paper, and carbon cloth; the diaphragm is a Nafion membrane, selected from one of Nafion117, Nafion115, Nafion212, and Nafion211.

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