An on-line detection method for the porosity of the electrodes of a dissolution-deposition type flow battery

Abstract

The present invention discloses an on-line detection method for the porosity of the electrodes of a dissolution-deposition type flow battery. The specific steps include: measuring the fiber diameter of the porous electrode, then assembling the flow battery and injecting the discharged-state electrolyte; recording the pressure of the electrode to be measured under the rated flow rate; calculating the electrode permeability according to the measured pressure, flow rate, as well as the geometric dimensions of the electrode and the viscosity of the electrolyte; calculating the electrode porosity according to the electrode permeability and in combination with the fiber diameter of the electrode; successively charging the battery to different state of charge and measuring the electrode permeability at each state; fitting a pressure-permeability equation according to the measured electrode permeability and pressure data; inputting the fitting equation into the battery management system to directly read the electrode permeability under the operating state, or reading the pressure and then calculating the real-time electrode permeability by using the fitting equation. This method has a convenient process, does not require complex equipment, has a low cost, and realizes the on-line measurement of the porosity of the electrodes of the dissolution-deposition type flow battery.

Description

Technical Field

[0001] The present invention relates to the field of on-line detection of flow batteries, and particularly to an on-line detection method for the porosity of the electrodes of a dissolution-deposition type flow battery. Background Art

[0002] As a new type of electrochemical energy storage system, flow batteries have the advantages of high efficiency, safety, and environmental friendliness, and have broad application prospects in the fields of large-scale power generation energy storage of renewable energy, power grid peak shaving, etc. The porous electrode is one of the key components of the flow battery and is also the carrier of the electrochemical reaction. Its porosity is one of the key influencing factors of the electrochemical behavior of the electrode and the flow resistance of the electrolyte, and is crucial for the performance of the battery.

[0003] The dissolution-deposition type flow battery is a new type of flow battery, and the phase change of the active substance occurs during the operation process. The solid-phase active substance is deposited on the electrode surface, resulting in the real-time change of the electrode porosity with the progress of charge and discharge. Therefore, obtaining the on-line data of the porosity of the dissolution-deposition type flow battery is of great significance for the research and application of such flow batteries.

[0004] At present, the detection of the electrode porosity mostly adopts the methods of "ultrasound" or "image scanning + 3D reconstruction". The former obtains the porosity data by using the relationship between the ultrasonic attenuation, sound pressure distribution, etc. and the material and its porosity; the latter uses a scanning electron microscope (SEM) or a computed tomography (CT) to obtain the microscopic image of the porous electrode, and then performs 3D reconstruction and analysis on the image by a computer, and calculates to obtain the porosity.

[0005] Although the above methods can be applied to the detection of the porosity of the porous electrode, they highly depend on the detection equipment and computer processing technology, and the process is very complicated; more importantly, due to the extrusion of the electrode after assembly, the pore structure changes, and this method adopts an off-line measurement method, which cannot reflect the electrode porosity under the actual use state, and cannot obtain the real-time change of the electrode porosity of the dissolution-deposition type flow battery. Summary of the Invention

[0006] Object of the Invention: Aiming at the problems in the prior art that the test process is complicated, the cost is high, and the real-time data of the electrode porosity during the charge and discharge of the dissolution-deposition type flow battery cannot be obtained, the present invention proposes an on-line detection method for the porosity of the electrodes of a dissolution-deposition type flow battery, which provides data support for the performance analysis and research of the flow battery cheaply and conveniently.

[0007] Technical Solution: To achieve the object of the present invention, the technical solution adopted by the present invention is: an on-line detection method for the porosity of the electrodes of a dissolution-deposition type flow battery, comprising the following steps:

[0008] Step 1: Measure the fiber diameter of the porous electrode, then assemble the flow battery and inject the discharged electrolyte;

[0009] Step 2: Operate the battery at the rated flow rate and record the pressure ΔP of the electrode to be measured;

[0010] Step 3: Calculate the electrode permeability κ based on the measured pressure, flow rate, electrode geometric dimensions, and electrolyte viscosity;

[0011] Step 4: Calculate the electrode porosity ε based on the calculated electrode permeability κ and the electrode fiber diameter;

[0012] Step 5: Charge the battery, increase the charging capacity by ΔC in sequence and repeat Steps 2 to 4 until the current capacity plus ΔC is greater than the rated capacity, where ΔC is the capacity step;

[0013] Step 6: Fit the pressure-porosity equation according to the electrode porosity and pressure data in Steps 1 to 5 to obtain the real-time change curve of the electrode porosity with pressure;

[0014] Step 7: Input the fitting equation into the battery management system to directly read the electrode porosity under the operating state, or read the pressure and then calculate the real-time electrode porosity using the fitting equation.

[0015] Further, in Step 3, the calculation method of the electrode permeability is as follows:

[0016]

[0017] where κ is the electrode permeability, μ is the electrolyte viscosity, l is the length of the porous electrode, Q is the flow rate, ΔP is the pressure, and A is the cross-sectional area of the electrode.

[0018] Further, in Step 4, the electrode porosity is calculated according to the Kozeny-Carman equation, and the method is as follows:

[0019]

[0020] where ε is the electrode porosity, d is the electrode fiber diameter, and K is the Kozeny-Carman coefficient.

[0021] Further, the dissolution-deposition type flow battery includes a zinc-based flow battery, a tin-based flow battery, an iron-based flow battery, a manganese-based flow battery, a lead-based flow battery, a nickel-based flow battery, and combinations of the above batteries.

[0022] Further, the porous electrode includes a carbon felt electrode, a graphite felt electrode, a carbon fiber electrode, or an electrode obtained by modifying, decorating, or compounding the above electrodes.

[0023] Further, the electrolyte includes alkaline, neutral, and acidic electrolytes.

[0024] Advantageous effects: Compared with the prior art, the technical solution of the present invention has the following advantageous technical effects:

[0025] The online detection method for the porosity of the dissolution-deposition type flow battery electrode provided by the present invention does not use large equipment, is convenient to operate, has low cost, and more importantly, can obtain the electrode porosity under the actual use state and the real-time change of the porosity of the dissolution-deposition type flow battery electrode. Description of the Drawings

[0026] Figure 1 is the flowchart of the method of the present invention. Detailed Embodiments

[0027] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0028] The online detection method for the porosity of the dissolution-deposition type flow battery electrode of the present invention has a process as Figure 1 , and the specific implementation is as follows:

[0029] Step 1: Measure the fiber diameter of the graphite felt electrode, d = 19.0 μm; then assemble a tin-vanadium flow battery with an effective area of 4500 cm 2 , and the number of monomers is 30; inject the discharged-state electrolyte, 0.5 mol / L SnSO4 + 3 mol / L H2SO4 at the negative electrode, and 1 mol / L VOSO4 + 3 mol / L H2SO4 at the positive electrode, 200 L each.

[0030] Step 2: Operate the battery at the rated flow rate and record the pressure ΔP of the electrode to be measured.

[0031] Step 3: Based on the measured pressure, flow rate, electrode geometric dimensions, and electrolyte viscosity, calculate the permeability κ of the porous electrode according to Darcy's law ΔP = μlQ / κA:

[0032]

[0033] where κ is the electrode permeability, μ is the electrolyte viscosity, l is the length of the porous electrode, Q is the flow rate, ΔP is the pressure, and A is the cross-sectional area of the electrode.

[0034] In this embodiment, the rated flow rate is 2 m 3 / h, the pressure to be measured is recorded as 190 kPa, the flow rate is 2 / 30 m 3 / h, the electrode geometric dimensions are 90 cm × 50 cm × 3.5 mm, and the electrolyte viscosity is 4.928 × 10 -3 Pa·s; the calculated result is: κ = 6.65 × 10-11 m 2 。

[0035] Step 4. According to the calculated electrode permeability κ, combined with the electrode fiber diameter, calculate the electrode porosity ε based on the Kozeny-Carman equation. The method is as follows:

[0036]

[0037] where ε is the electrode porosity, d is the electrode fiber diameter, and K is the Kozeny-Carman coefficient (4.28). In this embodiment, ε = 96.35% is calculated.

[0038] Step 5. Charge the battery, increase the charging capacity by ΔC in sequence and repeat Steps 2 to 4 until the current capacity plus ΔC is greater than the rated capacity, where ΔC is the capacity step, and the ratio of ΔC to the rated capacity is 0.1% - 20%.

[0039] Step 6. Fit the pressure-porosity equation ε = f(ΔP) according to the electrode porosity and pressure data in Steps 1 to 5 to obtain the real-time change curve of the electrode porosity with pressure. Under non-rated flow, ε = f(ΔP / a), where a is the ratio of the actual flow to the rated flow. In this embodiment, the electrode porosity data at different pressures are shown in Table 1.

[0040] Table 1

[0041] Pressure / kPA Porosity / % Pressure / kPA Porosity / % Pressure / kPA Porosity / % 190 96.35 410 92.83 680 89.34 223 95.82 438 92.37 718 88.86 253 95.31 477 91.80 761 88.35 284 94.82 518 91.37 805 87.87 315 94.38 556 90.89 844 87.32 346 93.86 598 90.40 889 86.81 375 93.34 633 89.84 939 86.36

[0042] Perform polynomial fitting on the data in Table 1 to obtain the pressure-porosity fitting equation, and then obtain the real-time change of the electrode porosity. The fitting equation is as follows:

[0043] ε = 100.13 - 2.16×10 -5 ΔP + 1.11×10 -11 ΔP 2 - 4.02×10 -18 ΔP 3

[0044] Step 7. Input the fitting equation into the battery management system to directly read the electrode porosity under the operating state, or read the pressure and then calculate the real-time electrode porosity using the fitting equation.

[0045] The above method is used for detecting the electrode porosity of a dissolution-deposition type tin-vanadium flow battery. The process is convenient, without the need for complex equipment, and has low cost. It realizes the on-line measurement of the electrode porosity and obtains the real-time data of the electrode porosity during the operation of the battery.

Claims

1. An on-line detection method for the porosity of electrodes of a dissolution-deposition type flow battery, characterized in that: It includes the following steps: Step 1: Measure the fiber diameter of the porous electrode, then assemble the flow battery and inject the discharged electrolyte; Step 2: Operate the battery at the rated flow rate and record the pressure ΔP of the electrode to be measured; Step 3: Calculate the electrode permeability κ according to the measured pressure, flow rate, electrode geometric dimensions, and electrolyte viscosity; Step 4: Calculate the electrode porosity ε according to the calculated electrode permeability κ and the electrode fiber diameter; Step 5: Charge the battery, increase the charge capacity by ΔC in sequence and repeat Steps 2 to 4 until the current capacity plus ΔC is greater than the rated capacity, where ΔC is the capacity step; Step 6: Fit the pressure-porosity equation according to the electrode porosity and pressure data in Steps 1 to 5 to obtain the real-time change curve of the electrode porosity with pressure; Step 7: Input the fitting equation into the battery management system to directly read the electrode porosity under the operating state, or read the pressure and then calculate the real-time electrode porosity using the fitting equation.

2. The online detection method according to claim 1, characterized in that: In Step 3, the calculation method of the electrode permeability is as follows: Among them, κ is the electrode permeability, μ is the electrolyte viscosity, l is the length of the porous electrode, Q is the flow rate, ΔP is the pressure, and A is the cross-sectional area of the electrode.

3. The online detection method according to claim 1, wherein: In Step 4, calculate the electrode porosity according to the Kozeny-Carman equation, and the method is as follows: Among them, ε is the electrode porosity, d is the electrode fiber diameter, and K is the Kozeny-Carman coefficient.

4. The online detection method according to any one of claims 1-3, characterized in that: The dissolution-deposition type flow battery described includes a zinc-based flow battery, a tin-based flow battery, an iron-based flow battery, a manganese-based flow battery, a lead-based flow battery, a nickel-based flow battery, and combinations of the above batteries.

5. The online detection method according to any one of claims 1-3, characterized in that: The porous electrode described includes a carbon felt electrode, a graphite felt electrode, a carbon fiber electrode, or an electrode obtained by modifying, decorating, or compounding the above electrodes.

6. The online detection method according to any one of claims 1-3, characterized in that: The electrolyte described includes alkaline, neutral, and acidic electrolytes.

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