Electrolyte modification method for delaying capacity fading of all-vanadium redox flow battery

Abstract

The invention belongs to the technical field of electrochemistry, and particularly relates to an electrolyte modification method for delaying capacity fading of an all-vanadium redox flow battery. The modification method comprises the following steps: adding an additive chromium chloride into the sulfuric acid electrolyte with active substances consisting of V3 + ions and VO < 2 + > ions, and adjusting the concentration of the additive to adjust the capacity fading of the all-vanadium redox flow battery. On the basis of the all-vanadium redox flow battery electrolyte based on V < 3 + > / VO < 2 + > (1: 1) and H2SO4, the problem of capacity fading of the all-vanadium redox flow battery is delayed by adding the additive into the electrolyte and adjusting the concentration. The selected additive is chromium chloride, and different concentrations of the additive are adjusted. The process is simple and easy to implement, the cost is low, and development, popularization and application of the high-power-density all-vanadium redox flow battery are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemistry, and in particular relates to an electrolyte modification method for delaying capacity decay of an all-vanadium liquid flow battery. Background Art

[0002] Renewable energy such as wind and solar energy is discontinuous and unstable, making it difficult to use them directly. Therefore, using energy storage technology to achieve continuous supply of renewable energy has become the key to solving the above problems. Liquid flow batteries have become one of the most promising technologies in the large-scale energy storage market due to their flexible design (separate design of capacity and power), good safety, and long design life.

[0003] The more mature liquid flow systems currently include all-vanadium liquid flow batteries, zinc-bromine liquid flow batteries, sodium polysulfide bromine, iron-chromium liquid flow batteries, manganese-based liquid flow batteries, etc. At present, the most widely used industrial battery is the all-vanadium liquid flow battery, but it has a capacity decay problem, which is an important problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide an electrolyte modification method for delaying the capacity decay of all-vanadium redox flow batteries, and the obtained electrolyte is mainly used in all-vanadium redox flow batteries. 3+ / VO 2+ Based on the all-vanadium liquid flow battery electrolyte of (1:1) and H2SO4, the capacity decay problem of the all-vanadium liquid flow battery is delayed by adding additives to the electrolyte and adjusting the concentration.

[0005] In order to achieve the above invention object, the technical solution of the present invention is as follows:

[0006] A method for modifying an electrolyte for delaying capacity decay of an all-vanadium liquid flow battery comprises the following steps: 3+ Ions and VO 2+ The additive chromium chloride is added to the sulfuric acid electrolyte composed of ions, and the capacity decay of the all-vanadium liquid flow battery is regulated by adjusting the concentration of the additive.

[0007] Furthermore, the electrolyte modification method is characterized in that the concentration of the additive chromium chloride is 0.1M to 0.5M (specifically 0.1M, 0.2M, 0.3M, 0.4M, 0.5M, etc.).

[0008] Furthermore, the electrolyte modification method is characterized in that: in the sulfuric acid electrolyte, V 3+ Ions and VO 2+ The molar ratio of the ions is 1:1.

[0009] Furthermore, the electrolyte modification method is characterized in that: in the sulfuric acid electrolyte, the concentration range of vanadium ions is 1.5-1.8M (specifically 1.5M, 1.55M, 1.6M, 1.65M, 1.7M, 1.75M, 1.8M, etc.).

[0010] Furthermore, the electrolyte modification method is characterized in that the sulfuric acid electrolyte is 98% (i.e., an electrolyte with a sulfuric acid content of 98%) and the concentration is 3M.

[0011] Furthermore, in the electrolyte modification method, the chemical purity level of the chromium chloride additive is> 99%, and the molecular formula is H 12 C l3 CrO6.

[0012] The present invention also protects a modified electrolyte obtained by any of the above methods for delaying the capacity decay of an all-vanadium liquid flow battery.

[0013] The present invention also protects the use of a modified electrolyte as described above for delaying the capacity decay of an all-vanadium liquid flow battery, wherein the electrolyte is charged and discharged to obtain electrolytes of various valence combinations as positive or negative electrolytes of the all-vanadium liquid flow battery.

[0014] Furthermore, an all-vanadium liquid flow battery contains a modified electrolyte obtained by any of the above methods for delaying the capacity decay of the all-vanadium liquid flow battery.

[0015] The sulfuric acid electrolyte is prepared by: in a vanadium ion concentration of 1.5 to 1.8 M V 3+ / VO 2+ In the vanadium redox flow battery electrolyte of 3M H2SO4 (molar ratio 1:1), H2SO4 with a concentration range of 0.1 to 0.8M was added. 12 CrCl3O6 was uniformly stirred at 600-800 rpm for 2 h at room temperature to obtain an all-vanadium liquid flow battery electrolyte.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (i) The present invention modifies the electrolyte of the all-vanadium redox flow battery by adding an additive, chromium chloride, to the electrolyte, thereby effectively improving the capacity attenuation phenomenon of the all-vanadium redox flow battery during the charge and discharge process.

[0018] (ii) The present invention reduces the capacity decay rate by adding chromium chloride and adjusting the concentration, thereby greatly saving costs and improving battery performance.

[0019] (III) The process of the present invention is simple and easy to implement, and the cost is low. The prepared modified electrolyte for delaying the capacity decay of the all-vanadium liquid flow battery is applied to the liquid flow battery, which is beneficial to the development and promotion of high power density battery stacks and has the characteristics of high capacity retention rate and simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the battery system;

[0021] Among them, 1 is the positive terminal plate; 2 is the negative terminal plate; 3 is the positive electrode; 4 is the negative electrode; 5 is the membrane; 6 is the positive electrode circulation pump; 7 is the negative electrode circulation pump; 8 is the positive electrode electrolyte storage tank; 9 is the negative electrode electrolyte storage tank.

[0022] Figure 2 for Figure 1 Schematic diagram of the battery in the battery system;

[0023] Among them, 1 is the positive end plate; 2 is the negative end plate; 3 is the positive bipolar plate; 4 is the negative bipolar plate; 5 is the positive electrode frame; 6 is the negative electrode frame; 7 is the positive electrode; 8 is the negative electrode; 9 is the membrane;

[0024] Figure 3 This is a curve chart showing the effect of the amount of chromium chloride added on the capacity retention rate of the battery system. DETAILED DESCRIPTION

[0025] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0026] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0027] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0028] The battery systems used in all embodiments and comparative examples are as follows Figure 1 As shown: it includes a single cell, a positive electrolyte storage tank 8, a negative electrolyte storage tank 9, a positive circulation pump 6, and a negative circulation pump 7; the positive electrolyte storage tank 8 is connected to the positive terminal plate 1 through the positive circulation pump 6, and the negative electrolyte storage tank 9 is connected to the negative terminal plate 2 through the negative circulation pump 7. The structure of the single cell is the positive terminal plate 1, the positive electrode 3 (3cm x3cm 3mm thick graphite felt), the diaphragm 5 (Nafion212), the negative electrode 4 (3cm x 3cm 3mm thick graphite felt), and the negative terminal plate 2; the structure of the single cell is as follows Figure 2As shown, the electrolyte flow rate is 50 ml / min, the charge and discharge voltage range is 1-1.15 V, and the current density is 100 mA cm -2 .

[0029] Embodiment 1:

[0030] All-vanadium redox flow battery, containing 80mL of positive electrolyte and 80mL of negative electrolyte.

[0031] The positive and negative electrolytes both contain 1.6 M vanadium ions, 3 M sulfuric acid and 0.1 M chromium chloride. 3+ / VO 2+ The concentration ratio is 1:1.

[0032] Embodiment 2:

[0033] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0034] The positive and negative electrolytes contain 1.6 M vanadium ions, 3 M sulfuric acid and 0.4 M chromium chloride, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0035] Embodiment 3:

[0036] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0037] The positive and negative electrolytes contain 1.8 M vanadium ions, 3 M sulfuric acid and 0.1 M chromium chloride, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0038] Embodiment 4:

[0039] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0040] The positive and negative electrolytes contain 1.8 M vanadium ions, 3 M sulfuric acid and 0.4 M chromium chloride, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0041] Embodiment 5:

[0042] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0043] The positive and negative electrolytes contain 1.8 M vanadium ions, 3 M sulfuric acid and 0.5 M chromium chloride, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0044] Embodiment 6:

[0045] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0046] The positive and negative electrolytes contain 1.8 M vanadium ions, 3 M sulfuric acid and 0.8 M chromium chloride, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0047] Comparative Example 1:

[0048] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0049] Both the positive and negative electrolytes contain 1.6 M vanadium ions, 3 M sulfuric acid, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0050] Comparative Example 2:

[0051] All-vanadium redox flow battery, positive electrolyte 80mL, negative electrolyte 80mL.

[0052] Both the positive and negative electrolytes contain 1.8 M vanadium ions, 3 M sulfuric acid, and V 3+ / VO 2+ The concentration ratio is 1:1.

[0053] Test 1:

[0054] according to Figure 1 Battery systems and Figure 2 The batteries in the test were assembled at room temperature (25°C). The test results are shown in Table 1:

[0055] Table 1 Performance comparison between Examples 1-6 and Comparative Examples 1-2

[0056]

[0057] As can be seen from the table above, after adding chromium chloride in this application, under the condition of the same current density, the average energy efficiency is improved, the cycle life is also greatly improved, and the capacity retention rate is good. This is because in this application, adding chromium chloride to improve the capacity attenuation of all-vanadium liquid flow batteries has the following four advantages:

[0058] 1. Electrochemical stability: Chromium chloride can enhance the electrochemical stability of the electrolyte and reduce the side reactions of the battery during charging and discharging. This helps maintain the performance of the battery and extend its service life.

[0059] 2. Inhibit side reactions: During battery operation, some adverse side reactions may occur (for example, incomplete redox reaction of vanadium ions). Chromium chloride can inhibit these side reactions by forming a stable complex, thereby reducing capacity decay.

[0060] 3. Improved ionic conductivity: Chromium chloride may increase the ionic conductivity of the electrolyte, allowing the battery to conduct ions more efficiently during operation, thereby improving overall performance.

[0061] 4. Formation of a protective film: On the surface of the electrode, the presence of chromium chloride can form a protective film, reducing the corrosion and degradation of the electrode material and further slowing down capacity decay.

[0062] Test 2:

[0063] The all-vanadium redox flow battery in Example 1 was tested at room temperature (25°C) to see the effect of the amount of chromium chloride added on the battery system capacity retention rate. Figure 3 .

[0064] Depend on Figure 3 It can be seen that as the concentration of chromium chloride increases, the capacity retention first increases and then decreases. The decrease is because a large increase in the concentration of chromium chloride will increase the viscosity of the electrolyte, increase concentration polarization, and cause capacity decay.

[0065] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0066] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A method for modifying an electrolyte for delaying capacity decay of an all-vanadium redox flow battery, characterized in that The following steps are involved: The active material is V 3+ Ions and VO 2+ The additive chromium chloride is added to the sulfuric acid electrolyte composed of ions, and the capacity decay of the all-vanadium liquid flow battery is regulated by adjusting the concentration of the additive.

2. The electrolyte modification method according to claim 1, characterized in that: The concentration of the additive chromium chloride is 0.1M to 0.5M.

3. The electrolyte modification method according to claim 1 or 2, characterized in that: In the sulfuric acid electrolyte, V 3+ Ions and VO 2+ The molar ratio of the ions is 1:

1.

4. The electrolyte modification method according to claim 3, characterized in that: In the sulfuric acid electrolyte, the concentration of vanadium ions ranges from 1.5 to 1.8M.

5. The electrolyte modification method according to claim 1 or 4, characterized in that: The sulfuric acid electrolyte is 98% and the concentration is 3M.

6. The electrolyte modification method according to claim 5, characterized in that: The purity level of chromium chloride additive is >99%, and the molecular formula is H 12 C l3 CrO6.

7. A modified electrolyte for delaying the capacity decay of an all-vanadium redox flow battery obtained by the method as claimed in claim 1, 2, 4 or 6.

8. The use of the modified electrolyte for delaying capacity decay of all-vanadium redox flow battery according to claim 7, characterized in that: The electrolyte is charged and discharged to obtain electrolytes with various valence combinations as the positive electrode or negative electrode electrolyte of the all-vanadium redox flow battery.

9. An all-vanadium liquid flow battery, characterized in that: A modified electrolyte for delaying capacity decay of an all-vanadium redox flow battery as described in claim 7.

Images