Method for inhibiting zinc corrosion of zinc-based flow battery

Abstract

The invention discloses a method for inhibiting zinc corrosion of a zinc-based flow battery. The method comprises the following steps: arranging a conductive diaphragm between a negative electrode and a diaphragm in the zinc-based flow battery; and metal zinc is deposited on the surface of the conductive diaphragm in the charging process of the zinc-based flow battery. The conductive diaphragm physically separates metal zinc generated in the charging process of the zinc-based flow battery from a negative electrode, so that zinc corrosion in the battery shelving process can be inhibited, the battery shelving performance is improved, the accumulation of positive active substances is reduced, and the battery cycling stability is improved.

Description

Technical Field

[0001] The present application relates to a method for inhibiting zinc corrosion in a zinc-based flow battery, belonging to the technical field of flow batteries. Background Art

[0002] Renewable energy sources such as wind energy and solar energy are discontinuous and unstable. This characteristic will cause an impact on the power grid during the grid connection process, affecting the safe and stable operation of the power grid. Energy storage technology can ensure the efficient and stable operation of renewable energy power generation during grid connection. Energy storage technology is mainly divided into two categories: physical energy storage and chemical energy storage. Among chemical energy storage, redox flow batteries suitable for large-scale and high-capacity energy storage have received wide attention due to their advantages such as independent battery power and capacity, rapid response, simple structure, and easy design. Among them, zinc-based flow batteries have received wide attention due to their high energy density, rich raw material reserves, and low price. Zinc-based flow batteries mainly include zinc-bromine flow batteries, zinc-iron flow batteries, zinc-iodine flow batteries, zinc-nickel flow batteries, etc. During the charge and discharge process of the battery, the negative electrode undergoes a deposition and dissolution reaction of metallic zinc.

[0003] In traditional zinc-based flow batteries, in order to obtain a higher power density, carbon felt is generally used as the electrode material to reduce the ion transport distance and lower the battery internal resistance. However, due to the good electrolyte wettability of carbon felt, there is a problem of corrosion during the storage of zinc-based flow batteries. The zinc corrosion reactions in alkaline and acidic zinc-based flow batteries are as follows:

[0004] Zn―2e ― +4OH ― →ZnO+H2O

[0005]

[0006] The existence of the zinc corrosion problem will lead to a decrease in the discharge capacity of the zinc-based battery after storage, a decline in the storage performance of the battery, and an impact on the overall efficiency of the battery. At the same time, it causes the accumulation of positive active substances, resulting in battery capacity attenuation. Summary of the Invention

[0007] According to one aspect of the present application, a method for inhibiting zinc corrosion in a zinc-based flow battery is provided, which solves the problem of corrosion existing in the zinc-based flow battery during storage in the prior art.

[0008] The present application adopts the following technical solutions:

[0009] A method for inhibiting zinc corrosion in a zinc-based flow battery, the method comprising:

[0010] Providing a conductive separator between the negative electrode and the separator in the zinc-based flow battery;

[0011] During the charging process of the zinc-based flow battery, metallic zinc is deposited on the surface of the conductive separator.

[0012] The conductive separator physically separates the metallic zinc generated during the charging process of the zinc-based flow battery from the negative electrode.

[0013] Optionally, the conductive separator is selected from a composite membrane formed by one or at least two of a conductive microfiltration membrane, a conductive ultrafiltration membrane, a conductive nanofiltration membrane, and a conductive reverse osmosis membrane.

[0014] Optionally, the conductive separator is preferably a composite membrane formed by one or two of a conductive microfiltration membrane and a conductive ultrafiltration membrane.

[0015] Since metallic zinc mainly deposits on the electrode surface near the separator side during the deposition process following the principle of the shortest ion transport path, in this application, by placing a conductive separator between the carbon felt electrode and the separator, metallic zinc is deposited on the conductive separator, so that the metallic zinc generated during the charging process is physically separated from the carbon felt electrode during the storage process, thereby reducing the corrosion of zinc by the electrolyte.

[0016] Optionally, the thickness of the conductive separator is 50 - 100 μm.

[0017] Optionally, the thickness of the conductive separator is selected from any value of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range value between any two of them.

[0018] Optionally, the thickness of the conductive separator is 50 - 80 μm.

[0019] Optionally, the thickness of the conductive separator is 50 - 60 μm.

[0020] Optionally, the materials of the positive electrode and the negative electrode in the zinc-based flow battery are both carbon felt or graphite felt.

[0021] Optionally, the zinc-based flow battery is selected from one of a zinc-bromine flow battery, a zinc-iron flow battery, a zinc-iodine flow battery, and a zinc-nickel flow battery.

[0022] The beneficial effects that can be achieved by this application include:

[0023] The method for inhibiting zinc corrosion in a zinc-based flow battery provided by this application, by placing a conductive separator between the negative carbon felt electrode and the separator of the zinc-based flow battery, inhibits zinc corrosion during the storage process of the battery, improves the storage performance of the battery, reduces the accumulation of positive active substances, improves the cycle stability of the battery, and the method of this application is simple to operate and easy to implement. Detailed implementation manners

[0024] The following describes this application in detail with reference to embodiments, but this application is not limited to these embodiments.

[0025] Unless otherwise specified, the raw materials in the embodiments of this application are all purchased through commercial channels.

[0026] Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all the settings recommended by the manufacturers.

[0027] The test method for battery performance is to use an Arbin charge-discharge instrument to perform battery charge-discharge tests.

[0028] Example 1

[0029] A zinc-bromine flow battery cycle performance experiment was carried out with 2M ZnBr2 + 3M KCl + 0.8M N-ethyl-N-methylpyrrolidinium bromide (MEP) as the electrolyte, a graphite plate as the current collector, carbon felt as the positive and negative electrodes of the battery, a PE membrane as the separator, and a conductive microfiltration membrane was placed between the negative carbon felt electrode and the separator, with a thickness of 50 μm for the conductive microfiltration membrane. The electrolyte flow rate was 60 ml / min, and the current density was 20 mA / cm 2 , charged for 2 h and discharged to 0.1 V. The electrode area was 48 cm 2 . After the battery was fully charged, it was left standing for 10 h and then discharged.

[0030] After the battery was left standing and then discharged, the Coulombic efficiency (CE) of the battery was 90%, the voltage efficiency (VE) was 85%, and the energy efficiency (EE) was 77%. The battery operated stably for 500 cycles, and the battery capacity did not decay.

[0031] Comparative Example 1

[0032] A zinc-bromine flow battery cycle performance experiment was carried out with 2M ZnBr2 + 3M KCl + 0.8M N-ethyl-N-methylpyrrolidinium bromide (MEP) as the electrolyte, a graphite plate as the current collector, carbon felt as both the positive and negative electrodes of the battery, a PE membrane as the separator, the electrolyte flow rate was 60 ml / min, and the current density was 20 mA / cm 2 , charged for 2 h and discharged to 0.1 V. The electrode area was 48 cm 2 . After the battery was fully charged, it was left standing for 10 h and then discharged.

[0033] After the battery was left standing and then discharged, the Coulombic efficiency (CE) of the battery was 80%, the voltage efficiency (VE) was 85%, and the energy efficiency (EE) was 68%.

[0034] Compared with the battery in Example 1 with a conductive film added, the Coulombic efficiency (CE) of the battery decreases by 10% after storage. This is mainly because by placing a conductive separator between the carbon felt electrode and the diaphragm, metallic zinc is deposited on the conductive separator, so that the metallic zinc generated during the charging process is physically separated from the carbon felt electrode during storage, thereby reducing the corrosion of zinc by the electrolyte and improving the storage performance of the battery. In addition, due to the accumulation of the positive electrode active material caused by zinc corrosion, the polarization of the battery increases, the voltage efficiency (VE) of the battery decreases, the battery performance deteriorates, and the voltage efficiency (VE) of the battery decreases from the initial 85% to 79% after 200 cycles of battery operation, with the voltage efficiency (VE) decreasing by 6%. As the number of cycles increases, the battery reaches the protection voltage during the charging process after 250 cycles, and the charging capacity of the battery gradually decreases. After 300 cycles, the battery capacity drops to 75% of the initial capacity.

[0035] Examples 2 - 7

[0036] The zinc-bromine flow battery and the cycle performance experiment are the same as those in Example 1, except that the thicknesses of the conductive microfiltration membranes are 40um, 60um, 70um, 80um, 90um, and 100um respectively. The battery performance results are shown in Table 1. As the thickness of the conductive film increases, the voltage efficiency (VE) of the battery decreases, which is mainly due to the increase in the internal resistance of the battery as the thickness of the conductive film increases. When the thickness of the conductive film is 40um, the Coulombic efficiency (CE) of the battery is relatively low after storage, which is mainly because metallic zinc is deposited within a certain thickness on the surface of the conductive film, and the conductive film is too thin to pierce the diaphragm, resulting in increased corrosion of metallic zinc.

[0037] Table 1 Battery performance tested in Examples 1 - 7

[0038]

[0039] Note: The Coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are all averaged from the battery cycle efficiency.

[0040] The cycle performance of the batteries with different thickness conductive films in Examples 1 - 7 and the battery in Comparative Example 1 without a conductive film is shown in Table 2. After adding the conductive film, the VE of the battery decreases, which is mainly due to the increase in the internal resistance of the battery caused by the addition of the conductive film; as the thickness of the conductive film increases, the VE of the battery decreases during the cycle process, which is mainly due to the increase in the internal resistance and polarization of the battery as the thickness of the conductive film increases.

[0041] Table 2 Cycle performance of batteries with different thickness conductive films

[0042]

[0043] Example 8

[0044] The cycle performance experiment of the zinc-bromine flow battery was carried out with 2M ZnBr2 + 3M KCl + 0.8M N-ethyl-N-methylpyrrolidinium bromide (MEP) as the electrolyte. The graphite plate was used as the current collector, the positive and negative electrodes of the battery were carbon felt, the separator was a PE membrane, and a conductive microfiltration membrane, a conductive ultrafiltration membrane, a conductive nanofiltration membrane, and a conductive reverse osmosis membrane were placed between the negative carbon felt electrode and the separator as conductive membranes. The thickness of the conductive membranes was all 50um. The electrolyte flow rate was 60ml / min, and the current density was 20mA / cm 2 , charged for 2h and discharged to 0.1V. The electrode area was 48cm 2 . After the battery was fully charged, it was left for 10h and then discharged. The battery performance results are shown in Table 3. It can be seen from the shelf performance of different types of conductive membranes that as the pore size of the conductive membrane decreases, the CE of the battery increases and the VE decreases during the shelf process. This is mainly because as the pore size of the conductive membrane decreases, it helps to reduce the corrosion of zinc generated during charging by water in the electrolyte. Therefore, as the pore size of the conductive membrane decreases, the CE of the battery increases. However, as the pore size of the separator decreases, the ion transport resistance during the charge and discharge process increases, resulting in a decrease in the VE of the battery. Among them, the battery with the conductive microfiltration membrane has the best performance.

[0045] Table 3 The battery performance of different types of conductive membranes is as follows:

[0046] Types of conductive membranes CE / % VE / % EE / % Conductive microfiltration membrane 90 85 77 Conductive ultrafiltration membrane 91 83 76 Conductive nanofiltration membrane 92 78 72 Conductive reverse osmosis membrane 93 76 71

[0047] The cycle performance is shown in Table 4. It can be seen from the cycle performance of different types of conductive membranes that as the pore size of the conductive membrane decreases, the VE of the battery decreases during the cycle process. This is mainly because as the pore size of the separator decreases, the ion transport resistance during the charge and discharge process increases.

[0048] Table 4 The battery cycle performance of different types of conductive membranes.

[0049] Types of conductive membranes CE / % VE / % EE / % Conductive microfiltration membrane 98 87 85 Conductive ultrafiltration membrane 98 85 84 Conductive nanofiltration membrane 98 81 79 Conductive reverse osmosis membrane 98 79 77

[0050] The above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A method for inhibiting zinc corrosion in a zinc-based flow battery, characterized in that, The method includes: A conductive separator is disposed between the negative electrode and the separator in the zinc-based flow battery; During the charging process of the zinc-based flow battery, metallic zinc is deposited on the surface of the conductive separator.

2. The method according to claim 1, characterized in that, The conductive separator is selected from a composite membrane formed by one or at least two of a conductive microfiltration membrane, a conductive ultrafiltration membrane, a conductive nanofiltration membrane, and a conductive reverse osmosis membrane.

3. The method according to claim 2, characterized in that, The conductive separator is selected from a composite membrane formed by one or two of a conductive microfiltration membrane and a conductive ultrafiltration membrane.

4. The method according to claim 1, characterized in that, The thickness of the conductive separator is 50 to 100 μm.

5. The method according to claim 4, characterized in that, The thickness of the conductive separator is 50 to 80 μm.

6. The method according to claim 4, characterized in that, The thickness of the conductive separator is 50 to 60 μm.

7. The method according to claim 1, characterized in that, The materials of the positive electrode and the negative electrode in the zinc-based flow battery are both carbon felt or graphite felt.

8. The method according to claim 1, characterized in that, The zinc-based flow battery is selected from one of a zinc-bromine flow battery, a zinc-iron flow battery, a zinc-iodine flow battery, and a zinc-nickel flow battery.

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