CN110911704A

CN110911704A - Iron-chromium flow battery electrolyte and application thereof

Info

Publication number: CN110911704A
Application number: CN201911169592.9A
Authority: CN
Inventors: 王绍亮; 刘建国; 严川伟
Original assignee: Institute of Metal Research of CAS
Current assignee: Institute of Metal Research of CAS
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2020-03-24

Abstract

The invention discloses an iron-chromium flow battery electrolyte and application thereof, and belongs to the technical field of flow battery energy storage. The electrolyte is prepared by adding one or more of potassium ions, sodium ions, magnesium ions or ammonium ions into low-acid electrolyte; the concentration of the added ions in the electrolyte is 0.01-3 mol/L. The electrolyte used by the invention can maintain the conductivity of the electrolyte under the condition of reducing the acid concentration, and can reduce the hydrogen evolution amount of the negative electrode electrolyte, thereby improving the efficiency of the battery and simultaneously slowing down the performance attenuation. The electrolyte is simple to obtain and operate, low in cost and capable of achieving stable operation of the electrolyte in the battery.

Description

Iron-chromium flow battery electrolyte and application thereof

Technical Field

The invention relates to the technical field of energy storage of flow batteries, in particular to an iron-chromium flow battery electrolyte and application thereof.

Background

With the continuous consumption of fossil energy and the increasing severity of environmental pollution, renewable energy sources such as solar energy, wind energy and the like are widely applied. However, the instability and discontinuity of these renewable energy power generation have restricted their further development. In order to improve the power quality and reliability of renewable energy power generation, a large-scale energy storage technology is one of effective solutions. The iron-chromium flow battery has the advantages of mutual independence of system energy and power, high response speed, safety, reliability, long cycle life, high energy efficiency and the like, so that the iron-chromium flow battery becomes one of the most promising technologies in the large-scale energy storage of renewable energy power generation and the like.

As a key component of an iron-chromium flow battery, the electrolyte determines the performance and stability of the battery to a large extent. In the actual operation process, the iron-chromium flow battery generally adopts hydrochloric acid aqueous solution containing iron ions and chromium ions, and in order to improve the conductivity of the electrolyte, higher-concentration hydrochloric acid aqueous solution is generally adopted. However, since the electrode potential of the chromium ion reaction in the cathode electrolyte is close to the hydrogen evolution potential, the hydrogen evolution reaction in the charging process is aggravated by the higher hydrogen ion concentration, and the performance of the battery is directly reduced. In addition, the iron-chromium flow battery usually adopts higher working temperature, and the hydrogen evolution reaction is aggravated, so that the capacity of the battery is quickly attenuated in multi-cycle operation. Therefore, it is particularly important to reduce the hydrogen evolution side reactions.

Disclosure of Invention

The invention aims to provide an iron-chromium flow battery electrolyte and application thereof, wherein the electrolyte is used for improving the performance of an iron-chromium current battery, reducing hydrogen evolution side reactions and improving the circulation stability of the electrolyte, so that the aim of efficiently and stably operating the iron-chromium flow battery is fulfilled.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

an iron-chromium flow battery electrolyte is obtained by adding an M ion source into a low-acid-concentration electrolyte, wherein the M ion is one or more of potassium ions, sodium ions, magnesium ions and ammonium ions; the low-acid-concentration electrolyte comprises the following components:

the preferred composition of the low acid concentration electrolyte is as follows:

in the low-acid-concentration electrolyte, iron ions are Fe³⁺And/or Fe²⁺The chromium ion is Cr³⁺、Cr²⁺、CrO₄ ^2-、CrO₂ ^-And Cr₂O₇ ^2-One ofOne or more of them.

The concentration of M ions in the iron-chromium flow battery electrolyte is 0.01-3 mol/L, and the concentration of M ions is preferably 0.1-2 mol/L.

The M ion source is one or more of a potassium ion source, a sodium ion source, a magnesium ion source and an ammonium ion source; the potassium ion source is KCl or KNO₃、K₂SO₄KClO, KBr, KI and KCH₃COO, wherein the source of sodium ions is NaCl or NaNO₃、Na₂SO₄NaClO, NaBr, NaI and NaCH₃One or more of COO, and the magnesium ion source is MgCl₂、Mg(NO₃)₂、MgSO₄、Mg(ClO)₂、MgBr₂、MgI₂And Mg (CH)₃COO)₂The source of ammonium ions is one or more of NH₄Cl、NH₄NO₃、(NH₄)₂SO₄、NH₄ClO、NH₄Br、NH₄I and NH₄CH₃COO or a plurality of COOs.

The electrolyte of the iron-chromium flow battery is used as a negative electrode electrolyte and/or a positive electrode electrolyte and applied to the iron-chromium flow battery, the service temperature of the electrolyte of the iron-chromium flow battery is 0-80 ℃, and the preferred service temperature is 40-70 ℃.

Compared with the prior art, the invention has the beneficial effects that:

1) the electrolyte used by the invention can be simultaneously added with one or more of potassium ions, sodium ions, magnesium ions and ammonium ions with proper concentration under the condition of reducing the acid concentration, thereby maintaining the conductivity of the electrolyte.

2) The electrolyte used in the invention can reduce the hydrogen evolution amount of the cathode electrolyte by reducing the acid concentration, thereby improving the efficiency of the battery and simultaneously slowing down the performance attenuation.

3) The electrolyte is simple to obtain and operate, low in cost and capable of guaranteeing long-term efficient and stable operation of the battery.

Drawings

FIG. 1 is a graph showing a comparison of discharge capacities when a battery was assembled using an A electrolyte containing 0.5M NaCl and 2.5M HCl and a B electrolyte containing 3M HCl as a negative electrode electrolyte in example 1.

FIG. 2 is a graph showing a comparison of energy efficiencies when a battery was assembled using the A electrolyte containing 0.5M NaCl and 2.5M HCl and the B electrolyte containing 3M HCl as the negative electrode electrolyte in example 1.

Detailed Description

The following examples are further illustrative of the present invention and are not intended to limit the scope of the present invention.

In the following examples, "M" means "mol/L".

Example 1

Respectively preparing electrolyte A and electrolyte B, wherein the electrolyte A comprises the following components: 1.0MFeCl₂、1.0MCrCl₃2.5MHCl, 0.5MNaCl and the balance of water; the composition of B electrolyte is 1.0MFeCl₂、1.0MCrCl₃3MHCl, the balance being water, and B electrolyte as a comparative solution. And respectively taking 70mL of electrolyte A to be detected and electrolyte B to be detected as negative electrolyte and 70mL of electrolyte B as positive electrolyte, and assembling the two iron-chromium flow batteries. Wherein the battery diaphragm is a 60 μm perfluorosulfonic acid membrane (purchased from Chaoyang Huading energy storage technology Co., Ltd.), and the effective area of the diaphragm is 50cm²The electrode is graphite felt, the bipolar plate is graphite plate, and the current density is 160mA/cm². The cell was subjected to constant current charge and discharge at 65 ℃ and the cut-off voltage was 0.7V to 1.2V, thereby obtaining the cell discharge capacity curve and the energy efficiency curve as shown in fig. 1 and 2. In the charging and discharging processes, the electrode potential of the chromium ion reaction in the contrast solution is close to the hydrogen evolution potential, the hydrogen evolution is serious, the battery performance is lower, and the capacity attenuation is faster. It can be seen from the figure that, when the electrolyte a obtained by adding NaCl with a certain concentration into the comparative solution and reducing the concentration of hydrochloric acid is charged and discharged, although the initial capacity and the energy efficiency are slightly lower than those of the battery with high concentration, the precipitation amount of hydrogen is effectively reduced along with the progress of charging and discharging, the decay of the discharge capacity and the energy efficiency is effectively slowed down, the stability of the electrolyte in long-term operation is obviously improved, and the more stable operation of the iron-chromium flow battery is realized.

Example 2

The operation was the same as that of example 1, except that the negative electrode electrolyte used was composed of: 1.0MFeCl₂、1.0MCrCl₃2.5m hcl, 0.5m kcl, and the balance water, it was found that the cell had significantly higher discharge capacity and energy efficiency after 5 cycles of operation than the comparative solution in example 1, and was able to operate stably.

Example 3

The operation was the same as that of example 1, except that the negative electrode electrolyte used was composed of: 1.0MFeCl₂、1.0MCrCl₃、2.5MHCl、0.5MNH₄Cl and the balance of water, and the result shows that the discharge capacity and the energy efficiency of the battery after 3 times of operation cycle are obviously higher than those of the comparative solution in the example 1, and the battery can stably operate.

Claims

1. The iron-chromium flow battery electrolyte is characterized in that: the iron-chromium flow battery electrolyte is obtained by adding an M ion source into a low-acid-concentration electrolyte, wherein the M ion is one or more of potassium ions, sodium ions, magnesium ions and ammonium ions; the low-acid-concentration electrolyte comprises the following components:

2. the iron-chromium flow battery electrolyte of claim 1, wherein: the low-acid-concentration electrolyte comprises the following components:

3. the iron-chromium flow battery electrolyte of claim 1 or 2, wherein: in the low-acid-concentration electrolyte, iron ions are Fe³⁺And/or Fe²⁺The chromium ion is Cr³⁺、Cr²⁺、CrO₄ ^2-、CrO₂ ^-And Cr₂O₇ ^2-One or more of them.

4. The iron-chromium flow battery electrolyte of claim 1 or 2, wherein: the concentration of M ions in the iron-chromium flow battery electrolyte is 0.01-3 mol/L.

5. The iron-chromium flow battery electrolyte of claim 4, wherein: the concentration of M ions in the iron-chromium flow battery electrolyte is 0.1-2 mol/L.

6. The iron-chromium flow battery electrolyte of claim 1 or 2, wherein: the M ion source is one or more of a potassium ion source, a sodium ion source, a magnesium ion source and an ammonium ion source; the potassium ion source is KCl or KNO₃、K₂SO₄KClO, KBr, KI and KCH₃COO, wherein the source of sodium ions is NaCl or NaNO₃、Na₂SO₄NaClO, NaBr, NaI and NaCH₃One or more of COO, and the magnesium ion source is MgCl₂、Mg(NO₃)₂、MgSO₄、Mg(ClO)₂、MgBr₂、MgI₂And Mg (CH)₃COO)₂The source of ammonium ions is one or more of NH₄Cl、NH₄NO₃、(NH₄)₂SO₄、NH₄ClO、NH₄Br、NH₄I and NH₄CH₃COO or a plurality of COOs.

7. Use of an iron-chromium flow battery electrolyte according to claim 1 or 2, characterized in that: the iron-chromium flow battery electrolyte is used as a negative electrode electrolyte and/or a positive electrode electrolyte and is applied to the iron-chromium flow battery.

8. The use of an iron-chromium flow battery electrolyte as claimed in claim 7, wherein: the service temperature of the iron-chromium flow battery electrolyte is 0-80 ℃.