Novel europium-cerium flow battery electrolyte and preparation method thereof

Abstract

The invention discloses a novel europium-cerium flow battery electrolyte and a preparation method thereof, and belongs to the technical field of flow battery energy storage. The theoretical voltage of the novel europium-cerium flow battery is 1.9 V, and the novel europium-cerium flow battery has higher energy density and power density. According to the synthesis strategy, a chelating agent is added into a solution containing europium or cerium, the molecular size of the formed chelate is large, and cross contamination caused by active ion transmembrane is avoided. The chelating agent can stabilize the reduction state of metal ions and slow down the oxidation reaction between the electrolyte and oxygen. The electrolyte is low in cost and suitable for being used in a neutral environment, europium and cerium are rare earth metals, have rich resource reserves, a complete industrial chain, advanced technical accumulation and policy support of the government in China, are matched with a chelating agent to improve oxidation-reduction kinetics, can be applied to a photovoltaic energy storage system on a large scale, and has a wide application prospect. Wide application prospects are also realized in the aspect of novel power automobiles.

Description

Technical Field

[0001] The present invention relates to the field of liquid flow battery energy storage technology, and specifically to a method for preparing a novel europium-cerium liquid flow battery electrolyte. The electrolyte has low cost, is suitable for use in a neutral environment, can be widely used in photovoltaic energy storage systems, and also has broad application prospects in new power vehicles. Background Art

[0002] Limited fossil fuel resources and global climate change have stimulated great interest in generating electrical energy from renewable resources. Among them, solar and wind energy are the most abundant and readily available energy sources. Capturing a small portion of the potential solar and wind energy can greatly contribute to meeting the world's electrical energy needs. However, solar and wind energy are not constant and reliable energy sources, but are decentralized and intermittent. To ensure the stability and reliability of the power grid, it is becoming increasingly important to seek efficient and large-scale electrical energy storage systems. Redox flow batteries are considered suitable for large-scale applications due to their modular design, good scalability and flexible operation.

[0003] At present, all-vanadium liquid flow batteries have entered the commercial operation stage, are relatively mature, and have been widely studied. However, the demand for liquid flow battery energy storage is large, and the development of a new preparation method for liquid flow electrolyte can better meet the demand for energy storage. China has rich reserves of rare earth resources, a complete industrial chain, advanced technology accumulation, and government policy support, which can be applied to photovoltaic energy storage systems on a large scale.

[0004] The europium-cerium flow battery is an all-rare earth flow battery with a high theoretical voltage, which improves the power density and energy density of the battery. However, after the negative electrode electrolyte is charged, the divalent europium ions in the solution will be oxidized by the air, the battery will self-discharge, decay quickly, and it will be difficult to operate continuously. In addition, europium-cerium batteries generally have slow oxidation kinetics, resulting in low coulombic efficiency and short cycle life. After adding a chelating agent to the electrolyte, it not only accelerates the reaction kinetics and migrates the electrochemical window, but also stabilizes the reduced state of europium ions and slows down the capacity decay caused by reaction with oxygen. Summary of the invention

[0005] The present invention develops a novel method for preparing an electrolyte for a europium-cerium liquid flow battery. A chelating agent is added to the electrolyte, and the chelating agent forms a stable coordination structure with active ions, which is expected to solve the deactivation of europium ions and improve the stability and cycle life of the battery.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing a novel europium-cerium liquid flow battery electrolyte, characterized in that the negative electrode electrolyte is an aqueous solution of europium, which contains trivalent europium ions and a chelate formed by one or more of the chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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 their derivative chemicals, and also contains a supporting electrolyte and an auxiliary electrolyte.

[0008] The positive electrode electrolyte is an aqueous solution of cerium, which contains trivalent cerium ions and a chelate formed by one or more of the chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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, and also contains supporting electrolytes and auxiliary electrolytes.

[0009] In the negative electrode electrolyte: the molar concentration of trivalent europium ions is 0 to 2.0 mol / L and is not 0, preferably 0.1 to 1.0 mol / L; the molar concentration of the chelating agent aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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 is 0 to 4.0 mol / L and is not 0, preferably 0.5 to 2.0 mol / L; the molar concentration of the supporting electrolyte is 0 to 8.0 mol / L, preferably 1.0 to 4.0 mol / L; the molar concentration of the auxiliary electrolyte is 0 to 3.0 mol / L, preferably 0.5 to 1.5 mol / L; oxygen-free deionized water is used as the solvent.

[0010] In the positive electrode electrolyte: the molar concentration of trivalent cerium ions is 0-2.0 mol / L and not 0, preferably 0.1-1.0 mol / L; the molar concentration of chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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 is 0-4.0 mol / L and not 0, preferably 0.5-2.0 mol / L; the molar concentration of supporting electrolyte is 0-8.0 mol / L, preferably 1.0-4.0 mol / L; the molar concentration of auxiliary electrolyte is 0-3.0 mol / L, preferably 0.5-1.5 mol / L; oxygen-free deionized water is used as solvent.

[0011] The active substance corresponding to the trivalent europium ion is one or more of europium phosphonate, europium chloride, europium nitrate, europium acetate, europium sulfate, and europium carbonate.

[0012] The substance corresponding to the trivalent cerium ion is one or more of cerium chloride, cerium phosphonate, cerium nitrate, cerium carbonate, cerium acetate, and cerium sulfate.

[0013] The supporting electrolyte is one or more of potassium carbonate, sodium bicarbonate, potassium bicarbonate, lithium hydroxide, potassium hydroxide, and sodium hydroxide. The auxiliary electrolyte is one or more of potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, potassium nitrate, and sodium nitrate to improve the conductivity of the electrolyte.

[0014] The novel method for preparing the europium-cerium liquid flow battery electrolyte is prepared according to the following process: in a reactor, add the corresponding europium active material or cerium active material, then add a chelating agent, add deionized water after mixing, heat, add supporting electrolyte and auxiliary electrolyte at 20°C to 90°C, stir well for 3 to 24 hours to make a uniform solution, and use it after standing for 6 hours.

[0015] Furthermore, the pH of the negative electrode electrolyte or the positive electrode electrolyte is 4 to 9, which is neutral.

[0016] The suitable operating temperature of the novel europium-cerium liquid flow battery electrolyte is 10-80°C.

[0017] Beneficial results of the present invention:

[0018] 1. The present invention coordinates cerium salt or europium salt with a chelating agent to form a stable coordination structure that is difficult to oxidize in the air, thereby improving the stability and cycle life of the battery.

[0019] 2. The positive and negative electrolytes of the present invention are rare earth metal ions, which are coordinated by the same chelating agent. The chelate molecules formed are large in size, which solves the cross-contamination caused by the transmembrane transport of active ions and improves the efficiency of the battery.

[0020] 3. The positive and negative electrolytes of the present invention have slow kinetics. After modification by the chelating agent, the redox kinetics are accelerated. Compared with the europium-cerium liquid flow battery without the addition of the chelating agent, a large current density can be used, and the current density can be doubled, thereby stably improving the battery performance.

[0021] 4. The positive and negative electrolytes used in the present invention are low-cost and easy to operate. Europium and cerium are rare earth metals with abundant reserves in China. They can be widely used in urban energy storage systems to reduce energy costs and improve energy utilization. They also have broad application prospects in the development of new power vehicles.

[0022] 5. The positive and negative electrolytes used in the present invention are suitable for use under mild conditions, are non-corrosive, have low equipment requirements, and effectively improve the operating stability of the battery. The theoretical voltage of the new europium-cerium liquid flow battery is 1.9V, which improves the energy density and power density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The positive and negative electrolytes of Example 2 are at 50mV·s -1 Cyclic voltammograms.

[0024] Figure 2 The coulombic efficiency-cycle curve of the comparative example within 1 to 10 cycles.

[0025] Figure 3 It is the charge and discharge capacity-cycle curve of the comparative example within 1 to 10 cycles.

[0026] Figure 4 The charge and discharge efficiency and capacity-cycle curves of Example 1 within 1 to 10 cycles.

[0027] Figure 5 The charge and discharge efficiency and capacity-cycle curves of Example 2 within 1 to 40 cycles. DETAILED DESCRIPTION

[0028] 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.

[0029] Comparative Example:

[0030] In this comparative example, the main components of the negative electrode electrolyte include: europium chloride, methanesulfonic acid, sodium chloride, and the solvent is oxygen-free deionized water, wherein the concentration of europium chloride is 0.2 mol / L, the concentration of methanesulfonic acid is 1.0 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0031] The positive electrode electrolyte mainly comprises: cerium chloride, methanesulfonic acid, sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of europium chloride is 0.2 mol / L, the concentration of methanesulfonic acid is 1.0 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0032] The specific steps for preparing the negative electrode electrolyte are as follows:

[0033] 7.3 g of europium chloride, 9.6 g of methanesulfonic acid and 2.9 g of sodium chloride were added in sequence, mixed, and deionized water was added. The mixture was stirred for 6 hours to make a uniform solution, and the volume was fixed to 100 mL. The solution was allowed to stand for 24 hours before use.

[0034] The specific steps for preparing the positive electrode electrolyte are as follows:

[0035] 7.5 g of cerium chloride, 9.6 g of methanesulfonic acid and 2.9 g of sodium chloride were added in sequence, mixed, and deionized water was added. The mixture was stirred for 6 hours to make a uniform solution, and the volume was fixed to 100 mL. The solution was allowed to stand for 24 hours before use.

[0036] 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.

[0037] Battery Test:

[0038] The volume of positive and negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 The porous carbon felt electrode and the proton membrane are Nafion 212 membrane. At 20 mA / cm 2 The current density is charged to 50 mAh at 20 mA / cm 2 The battery was discharged to 0.1 V at a current density of 2.5 %.

[0039] Without the protection of inert gas, the electrolyte will come into contact with air. Figure 2 In 1 to 10 cycles, the battery coulombic efficiency drops from 80% in the first cycle to 20%. Figure 3 In the 1 to 10 cycles, the battery capacity decays rapidly. This is because during the charging process, the trivalent europium ions are reduced to divalent europium ions, which are quickly oxidized by the air and cannot be discharged.

[0040] Embodiment 1:

[0041] In this embodiment, the main components of the negative electrode electrolyte include: europium chloride, diethylenetriaminepentaacetic acid, potassium carbonate, sodium chloride, and the solvent is oxygen-free deionized water. The concentration of europium chloride is 0.2 mol / L, the concentration of diethylenetriaminepentaacetic acid is 0.2 mol / L, the concentration of potassium carbonate is 0.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0042] The main components of the positive electrode electrolyte include: cerium chloride, diethylenetriaminepentaacetic acid, potassium carbonate, sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of europium chloride is 0.2mol / L, the concentration of diethylenetriaminepentaacetic acid is 0.2mol / L, the concentration of potassium carbonate is 0.5mol / L, and the concentration of sodium chloride is 0.5mol / L.

[0043] The specific steps for preparing the negative electrode electrolyte are as follows:

[0044] In the reactor, add 7.3g of europium chloride and 7.9g of diethylenetriaminepentaacetic acid in sequence, add deionized water after mixing, heat, add 6.91g of potassium carbonate and 2.9g of sodium chloride at 90°C, stir well for 3 hours to make a uniform solution, transfer to a 100ml volumetric flask, make up to volume, and let stand for 6 hours before use.

[0045] The specific steps for preparing the positive electrode electrolyte are as follows:

[0046] In the reactor, add 7.5g cerium chloride and 7.9g diethylenetriaminepentaacetic acid in sequence, add deionized water after mixing, heat, add 6.91g potassium carbonate and 2.9g sodium chloride at 90°C, stir well for 3 hours to make a uniform solution, transfer to a 100ml volumetric flask, make up to volume, and let stand for 6 hours before use.

[0047] Battery Test:

[0048] The volume of positive and negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 The porous carbon felt electrode and the proton membrane are Nafion 212 membrane. At 20 mA / cm 2 The current density is charged to 50 mAh at 20 mA / cm 2 The battery was discharged to 0.1 V at a current density of 2.5 %.

[0049] Without the protection of inert gas, the electrolyte will come into contact with air. Figure 4 In 1 to 10 cycles, the coulombic efficiency of the battery is maintained at about 90%, the voltage efficiency and energy efficiency can be stabilized at about 70% and 60%, and the capacity of the battery will not decay. After adding the chelating agent, the divalent europium ions are not easily oxidized, and the performance indicators of the battery in Example 1 are higher than those in the comparative example.

[0050] Embodiment 2:

[0051] In this embodiment, the main components of the negative electrode electrolyte include: europium chloride, aminotriacetic acid, potassium carbonate, sodium chloride, and the solvent is oxygen-free deionized water. The concentration of europium chloride is 0.2 mol / L, the concentration of aminotriacetic acid is 0.2 mol / L, the concentration of potassium carbonate is 0.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0052] The main components of the positive electrode electrolyte include: cerium chloride, diaminotriacetic acid, potassium carbonate, sodium chloride, and the solvent is oxygen-free deionized water. Among them, the concentration of europium chloride is 0.2 mol / L, the concentration of diaminotriacetic acid is 0.2 mol / L, the concentration of potassium carbonate is 0.5 mol / L, and the concentration of sodium chloride is 0.5 mol / L.

[0053] The electrolyte preparation method is referred to Example 1.

[0054] The positive and negative electrolytes were at 50 mV·s -1 Perform cyclic voltammetry tests such as Figure 1 The theoretical voltage of a single cell is 1.9V, which can provide higher power density and energy density.

[0055] Battery Test:

[0056] The volume of positive and negative electrolyte is 20ml each, and the positive and negative electrodes are 3×3cm 2 The porous carbon felt electrode and the proton membrane are Nafion 212 membranes. After modification with chelating agents, the reaction kinetics of the electrolyte are accelerated, and the current density in the comparative battery test is doubled to 40 mA / cm 2 The current density is charged to 50 mAh at 40 mA / cm 2 The battery was discharged to 0.1 V at a current density of 2.5 %.

[0057] Without the protection of inert gas, the electrolyte will come into contact with air. Figure 5 Within 1 to 40 cycles, the battery coulombic efficiency is about 80%, the voltage efficiency and energy efficiency can be stabilized at about 80% and 60%, and the battery capacity will not decay.

Claims

1. A novel europium-cerium liquid flow battery electrolyte, characterized in that: The negative electrode electrolyte is an aqueous solution of europium, which contains trivalent europium ions and a chelate formed by one or more of the chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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, and also contains a supporting electrolyte and an auxiliary electrolyte; The positive electrode electrolyte is an aqueous solution of cerium, which contains trivalent cerium ions and a chelate formed by one or more of the chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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, and also contains supporting electrolytes and auxiliary electrolytes.

2. A novel europium-cerium liquid flow battery electrolyte according to claim 1, characterized in that: In the negative electrode electrolyte: the molar concentration of trivalent europium ions is 0 to 2.0 mol / L and is not 0, preferably 0.1 to 1.0 mol / L; the molar concentration of the chelating agent aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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 is 0 to 4.0 mol / L and is not 0, preferably 0.5 to 2.0 mol / L; the molar concentration of the supporting electrolyte is 0 to 8.0 mol / L, preferably 1.0 to 4.0 mol / L; the molar concentration of the auxiliary electrolyte is 0 to 3.0 mol / L, preferably 0.5 to 1.5 mol / L; oxygen-free deionized water is used as the solvent.

3. A novel europium-cerium liquid flow battery electrolyte according to claim 1, characterized in that: In the positive electrode electrolyte: the molar concentration of trivalent cerium ions is 0-2.0 mol / L and not 0, preferably 0.1-1.0 mol / L; the molar concentration of chelating agents aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic 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 is 0-4.0 mol / L and not 0, preferably 0.5-2.0 mol / L; the molar concentration of supporting electrolyte is 0-8.0 mol / L, preferably 1.0-4.0 mol / L; the molar concentration of auxiliary electrolyte is 0-3.0 mol / L, preferably 0.5-1.5 mol / L; oxygen-free deionized water is used as solvent.

4. A novel europium-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The active substance corresponding to the trivalent europium ion is one or more of europium phosphonate, europium chloride, europium nitrate, europium acetate, europium sulfate, and europium carbonate.

5. A novel europium-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The substance corresponding to the trivalent cerium ion is one or more of cerium chloride, cerium phosphonate, cerium nitrate, cerium carbonate, cerium acetate, and cerium sulfate.

6. A novel europium-cerium liquid flow battery electrolyte according to claim 1, characterized in that: The supporting electrolyte is one or more of potassium carbonate, sodium bicarbonate, potassium bicarbonate, lithium hydroxide, potassium hydroxide, and sodium hydroxide; the auxiliary electrolyte is one or more of potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, potassium nitrate, and sodium nitrate.

7. A method for preparing a novel europium-cerium liquid flow battery electrolyte according to any one of claims 1 to 6, characterized in that: It is prepared according to the following process: in a reactor, add the corresponding europium active substance or cerium active substance, then add a chelating agent, add deionized water after mixing, heat, add supporting electrolyte and auxiliary electrolyte at 20°C to 90°C, stir well for 3 to 24 hours to make a uniform solution, and use it after standing for 6 hours.

8. The method according to claim 7, characterized in that The pH of the negative electrode electrolyte or the positive electrode electrolyte is 4-9.

9. The method according to claim 7, characterized in that The electrolyte operates at a temperature of 10 to 80°C.

10. A europium-cerium flow battery, characterized in that: A novel europium-cerium liquid flow battery electrolyte comprising any one of claims 1 to 6; the novel europium-cerium liquid flow battery has a theoretical voltage of 1.9V.

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