An apparatus and control method for delaying capacity degradation of an all-vanadium redox flow battery

Abstract

The application discloses a device and a control method for delaying capacity attenuation of a full-vanadium redox flow battery, and relates to the technical field of flow batteries. The device and the control method can directly mix the positive and negative electrode side reaction gases of the flow battery to perform a chemical reaction, and the reaction products can be distributed back to the electrolyte storage tank according to the amount of the reactant gas, thereby solving the consumption of the byproduct gas, avoiding the loss of the electrolyte acid radical ions, slowing down the rate of electrolyte valence imbalance, and slowing down the capacity attenuation rate of the battery system.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a device and a control method for delaying capacity attenuation of an all-vanadium liquid flow battery. Background Art

[0002] All-vanadium liquid flow battery system has the characteristics of high safety, long life and long duration, and is suitable for large-scale energy storage technology. Conventional all-vanadium liquid flow battery system such as Figure 1 As shown in the figure, the capacity of the all-vanadium flow battery also decays during its use. There are two main reasons for the capacity decay of the all-vanadium flow battery system. Reason one: the migration of vanadium ions in the positive and negative electrodes leads to a difference in the total amount of vanadium ions in the positive and negative electrodes, so that the total discharge capacity is determined by the side with lower total amount of vanadium ions in the positive and negative electrodes, resulting in capacity decay of the all-vanadium flow battery; Reason two: caused by the valence imbalance of vanadium ions in the positive and negative electrodes, that is, a series of side reactions will lead to valence imbalance of vanadium ions in the positive and negative electrodes, such as hydrogen (H2) side reaction at the negative electrode, oxygen (O2) and chlorine (Cl2) side reactions at the positive electrode, etc.

[0003] After searching, invention patent CN110858659B discloses a method for treating waste gas from a liquid flow battery and a liquid flow battery system. The method includes mixing the oxidizing waste gas generated by overcharging the positive electrode electrolyte with the negative electrode electrolyte to perform an oxidation-reduction reaction. This method can absorb the oxidizing waste gas generated by overcharging the positive electrode without causing the electrolyte to lose acid ions, effectively maintaining the balance of the electrolyte, and helping to maintain the capacity of the battery during long-term operation. However, this method only solves the problem of treating the positive electrode side reaction gas and cannot effectively solve the problem of treating the negative electrode side reaction gas H2. In addition, although the ignition method can consume the side reaction gas according to the stoichiometric ratio, due to the insufficient purity of the positive and negative electrode side reaction gases of the liquid flow battery, there is a risk of explosion when ignited. Therefore, a device and control method for delaying the capacity decay of an all-vanadium liquid flow battery are proposed. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art and to propose a device and a control method for delaying the capacity decay of an all-vanadium redox flow battery.

[0005] A device for delaying capacity attenuation of an all-vanadium liquid flow battery comprises a positive electrode storage tank, a negative electrode storage tank and a fuel cell, wherein the tank tops of the positive electrode storage tank and the negative electrode storage tank are respectively connected to a positive electrode gas pipe and a negative electrode gas pipe, the other ends of the positive electrode gas pipe and the negative electrode gas pipe are connected to the fuel cell, the bottom of the fuel cell is connected to an agitator via a conduit, the bottom of the agitator is connected to a positive electrode return pipe and a negative electrode return pipe, the other ends of the positive electrode return pipe and the negative electrode return pipe are respectively connected to the positive electrode storage tank and the negative electrode storage tank.

[0006] Preferably, an air pump, an air intake filter, a compressor, a gas storage tank and an air intake valve are provided on the paths of the positive electrode gas supply pipe and the negative electrode gas supply pipe. The air pump, the air intake filter, the compressor, the gas storage tank and the air intake valve are arranged in sequence, and the air pump is close to one end of the positive electrode storage tank. The two air intake valves are connected to a controller through wires.

[0007] Preferably, the positive electrode return pipe and the negative electrode return pipe are both provided with a liquid return valve, and the two liquid return valves are electrically connected to the controller.

[0008] Preferably, a gas concentration detector is provided on the top of each of the positive electrode storage tank and the negative electrode storage tank, and the two gas concentration detectors are electrically connected to the controller.

[0009] Preferably, a pressure sensor is provided in each of the gas storage tanks, and the two pressure sensors are electrically connected to the controller.

[0010] Preferably, a gas flow sensor is provided on one end of the positive electrode gas supply pipe and the negative electrode gas supply pipe close to the fuel cell, and the two gas flow sensors are electrically connected to the controller.

[0011] The present invention also proposes a control method for delaying capacity decay of an all-vanadium redox flow battery, comprising the following steps:

[0012] S1, using a gas concentration detector to detect the concentration and gas type of the side reaction gas in the upper layer of the positive electrode storage tank and the negative electrode storage tank in real time, and transmit the detection results to the controller;

[0013] S2. When the side reaction gases in the upper layers of the positive and negative electrode storage tanks do not reach the threshold, or only one gas reaches the threshold, the controller does not send a signal; when the side reaction gases in the upper layers of the positive and negative electrode storage tanks both reach the threshold, the controller sends a signal, the air pump starts working, and the side reaction gases in the upper layers of the positive and negative electrode storage tanks are pumped into the gas storage tanks;

[0014] S3. The pressure sensor inside the gas storage tank transmits the signal to the controller. When the pressure value reaches the designed stop threshold, the compressor is controlled to stop running.

[0015] S4. After the compressor stops running, the controller issues an opening command for the intake valve, and the compressed gas inside the gas storage tank enters the fuel cell for reaction;

[0016] S5. Based on the signal from the gas flow sensor on the gas pipeline, the controller adjusts the opening of the intake valve in real time, thereby adjusting the reaction rate inside the fuel cell;

[0017] S6. The reaction products generated during the reaction of the side reaction gas in the fuel cell until the reaction stops are temporarily stored in the agitator;

[0018] S7. The controller adjusts the opening of the liquid return valve according to the type and stoichiometric ratio of the reactants to ensure that the reaction products are distributed in the liquid return according to the amount of the reactants.

[0019] Compared with the existing technology, the advantages of the present invention are:

[0020] 1. The device and control method of the present invention can directly mix the positive and negative side reaction gases of the liquid flow battery to carry out a chemical reaction, and the reaction products can be distributed and returned to the electrolyte storage tank according to the amount of reactant gas. On the one hand, it solves the problem of absorbing the by-product gas, and on the other hand, it avoids the loss of electrolyte acid ions.

[0021] 2. The present invention reacts the by-product gases of the positive and negative electrodes in strict accordance with the stoichiometric ratio, thereby slowing down the rate of valence imbalance of the electrolyte and thus slowing down the capacity decay rate of the battery system.

[0022] 3. The present invention improves the purity and concentration of positive and negative electrode by-products through an intake filter, a compressor and a gas storage tank, thereby improving the safety and reliability of the reaction of positive and negative electrode by-products in the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a conventional all-vanadium liquid flow battery system.

[0024] Figure 2 It is a structural schematic diagram of the device part in the present invention.

[0025] Figure 3 Schematic diagram of the control method of the present invention.

[0026] In the figure: 1 positive electrode storage tank, 101 positive electrode gas supply pipe, 102 positive electrode return pipe, 2 negative electrode storage tank, 201 negative electrode gas supply pipe, 202 negative electrode return pipe, 3 fuel cell, 4 stirrer, 5 controller, 6 air pump, 7 intake filter, 8 compressor, 9 gas storage tank, 10 pressure sensor, 11 intake valve, 12 gas flow sensor, 13 liquid return valve, 14 gas concentration detector. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0028] Reference Figure 2As shown, a device for delaying the capacity decay of an all-vanadium liquid flow battery includes a positive electrode storage tank 1, a negative electrode storage tank 2 and a fuel cell 3. The tank tops of the positive electrode storage tank 1 and the negative electrode storage tank 2 are respectively connected to a positive electrode gas pipe 101 and a negative electrode gas pipe 201, and the other ends of the positive electrode gas pipe 101 and the negative electrode gas pipe 201 are connected to the fuel cell 3. The bottom of the fuel cell 3 is connected to an agitator 4 through a conduit, and the bottom of the agitator 4 is connected to a positive electrode return pipe 102 and a negative electrode return pipe 202, and the other ends of the positive electrode return pipe 102 and the negative electrode return pipe 202 are respectively connected to the positive electrode storage tank 1 and the negative electrode storage tank 2.

[0029] The positive electrode gas delivery pipe 101 and the negative electrode gas delivery pipe 201 are both provided with an air pump 6, an air intake filter 7, a compressor 8, a gas storage tank 9 and an air intake valve 11. The air pump 6, the air intake filter 7, the compressor 8, the gas storage tank 9 and the air intake valve 11 are arranged in sequence, and the air pump 6 is close to one end of the positive electrode storage tank 1. The two air intake valves 11 are connected to the controller 5 through a wire.

[0030] The positive electrode return pipe 102 and the negative electrode return pipe 202 are both provided with a return liquid valve 13, and the two return liquid valves 13 are electrically connected to the controller 5. The tops of the positive electrode storage tank 1 and the negative electrode storage tank 2 are both provided with a gas concentration detector 14, and the two gas concentration detectors 14 are electrically connected to the controller 5. Each of the gas storage tanks 9 is provided with a pressure sensor 10, and the two pressure sensors 10 are electrically connected to the controller 5. The positive electrode gas supply pipe 101 and the negative electrode gas supply pipe 201 are both provided with a gas flow sensor 12 on one end of the pipeline close to the fuel cell 3, and the two gas flow sensors 12 are electrically connected to the controller 5.

[0031] Reference Figure 3 As shown, a control method for delaying the capacity decay of an all-vanadium redox flow battery comprises the following steps:

[0032] S1, using the gas concentration detector 14 to detect the concentration and gas type of the side reaction gas in the upper layer of the positive electrode storage tank 1 and the negative electrode storage tank 2 in real time, and transmit the detection results to the controller 5;

[0033] S2. When the amount of the side reaction gas in the upper layers of the positive electrode storage tank 1 and the negative electrode storage tank 2 does not reach the threshold, or only one gas reaches the threshold, the controller 5 does not send a signal; when the amount of the side reaction gas in the upper layers of the positive electrode storage tank 1 and the negative electrode storage tank 2 both reach the threshold, the controller 5 sends a signal, the air pump 6 starts working, and the side reaction gas in the upper layers of the positive electrode storage tank 1 and the negative electrode storage tank 2 is pumped into the gas storage tank 9;

[0034] S3, the pressure sensor 10 inside the gas storage tank 9 transmits a signal to the controller 5, and when the pressure value reaches the designed stop threshold, the compressor 8 is controlled to stop running;

[0035] S4: After the compressor 8 stops running, the controller 5 issues an opening command for the air inlet valve 11, and the compressed gas inside the gas storage tank 9 enters the fuel cell 3 for reaction;

[0036] S5. Based on the signal from the gas flow sensor 12 on the gas pipeline, the controller 5 adjusts the opening of the intake valve 11 in real time, thereby adjusting the reaction rate inside the fuel cell 3;

[0037] S6. The reaction products generated during the reaction of the side reaction gas in the fuel cell 3 until the reaction stops are temporarily stored in the agitator 4, so as to achieve rapid removal of the products of the fuel cell 3, promote the increase of the forward reaction rate, and at the same time ensure sufficient mixing of the reaction products during the entire reaction process;

[0038] S7. The controller 5 adjusts the opening of the liquid return valve 13 according to the type and stoichiometric ratio of the reactants to ensure that the reaction products are distributed in the liquid return according to the amount of the reactants.

[0039] Example

[0040] Example 1: A representative sulfuric acid system electrolyte; the negative electrode side reaction gas is H2, and the positive electrode side reaction gas is O2. In the sulfuric acid system electrolyte, the negative electrode side reaction is mainly the hydrogen evolution reaction, and the positive electrode side reaction is mainly the oxygen evolution reaction. The reaction equation of the side reaction gas in the fuel cell is: 2H2+O2=2H2O, and the stoichiometric ratio of the positive and negative electrode by-product gases in the fuel cell is 1:2.

[0041] Example 2: Representative hydrochloric acid system electrolyte; the negative electrode side reaction gas is H2, and the positive electrode side reaction gas is Cl2. In the hydrochloric acid system electrolyte, the negative electrode side reaction is mainly hydrogen evolution reaction, and the positive electrode side reaction is mainly chlorine evolution reaction. The reaction equation of the side reaction gas in the fuel cell is: H2+Cl2=2HCl, and the stoichiometric ratio of the positive and negative electrode by-product gases in the fuel cell is 1:1.

[0042] Example 3: represents a mixed acid system electrolyte; the negative electrode side reaction gas is H2, and the positive electrode side reaction gas is a mixture of O2 and Cl2. In the mixed acid system electrolyte, the negative electrode side reaction is mainly a hydrogen evolution reaction, and the positive electrode side reaction is mainly a chlorine evolution reaction, accompanied by a small amount of oxygen evolution reaction. The reaction equation of H2 and Cl2 in the fuel cell is: H2+Cl2=2HCl, and the stoichiometric ratio of the positive and negative electrode by-product gases in the fuel cell is 1:1; the reaction equation of H2 and O2 in the fuel cell is: 2H2+O2=2H2O, and the stoichiometric ratio of the positive and negative electrode by-product gases in the fuel cell is 1:2.

[0043] In summary, the device and control method for managing the side reaction gas of the all-vanadium liquid flow battery proposed in the present invention can directly chemically react the positive and negative electrode side reaction gases, and the reaction products can be distributed and returned to the electrolyte storage tank according to the amount of reactant gas. On the one hand, it solves the problem of the disposal of the by-product gas, and on the other hand, it avoids the loss of electrolyte acid ions. In addition, the present invention strictly reacts the positive and negative electrode by-product gases according to the stoichiometric ratio, slowing down the rate of imbalance of the electrolyte valence state, thereby slowing down the capacity decay rate of the battery system.

[0044] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A device for delaying capacity decay of an all-vanadium redox flow battery, characterized by: The invention comprises a positive electrode storage tank (1), a negative electrode storage tank (2) and a fuel cell (3), wherein the tank tops of the positive electrode storage tank (1) and the negative electrode storage tank (2) are respectively connected to a positive electrode gas supply pipe (101) and a negative electrode gas supply pipe (201), the other ends of the positive electrode gas supply pipe (101) and the negative electrode gas supply pipe (201) are connected to the fuel cell (3), the bottom of the fuel cell (3) is connected to an agitator (4) via a conduit, the bottom of the agitator (4) is connected to a positive electrode return pipe (102) and a negative electrode return pipe (202), the other ends of the positive electrode return pipe (102) and the negative electrode return pipe (202) are respectively connected to the positive electrode storage tank (1) and the negative electrode storage tank (2); An air pump (6), an air intake filter (7), a compressor (8), a gas storage tank (9), and an air intake valve (11) are both provided on the paths of the positive electrode gas supply pipe (101) and the negative electrode gas supply pipe (201). The air pump (6), the air intake filter (7), the compressor (8), the gas storage tank (9), and the air intake valve (11) are arranged in sequence, and the air pump (6) is close to one end of the positive electrode storage tank (1). The two air intake valves (11) are connected to a controller (5) via a wire. The positive electrode return pipe (102) and the negative electrode return pipe (202) are both provided with a liquid return valve (13), and the two liquid return valves (13) are electrically connected to the controller (5).

2. The device for delaying capacity decay of an all-vanadium redox flow battery according to claim 1, characterized in that: A gas concentration detector (14) is provided on the top of each of the positive electrode storage tank (1) and the negative electrode storage tank (2), and the two gas concentration detectors (14) are electrically connected to the controller (5).

3. The device for delaying capacity decay of an all-vanadium redox flow battery according to claim 2, characterized in that: A pressure sensor (10) is provided in each gas storage tank (9), and the two pressure sensors (10) are electrically connected to the controller (5).

4. The device for delaying capacity decay of an all-vanadium redox flow battery according to claim 3, characterized in that: Gas flow sensors (12) are provided on one end of the positive electrode gas supply pipe (101) and the negative electrode gas supply pipe (201) close to the fuel cell (3), and the two gas flow sensors (12) are electrically connected to the controller (5).

5. A control method for delaying capacity decay of an all-vanadium redox flow battery, using the device for delaying capacity decay of an all-vanadium redox flow battery according to claim 4, characterized in that: The following steps are involved: S1, detecting the concentration and gas type of the side reaction gas in the upper layer of the positive electrode storage tank (1) and the negative electrode storage tank (2) in real time through the gas concentration detector (14), and transmitting the detection results to the controller (5); S2. When the side reaction gases in the upper layers of the positive electrode storage tank (1) and the negative electrode storage tank (2) do not reach the threshold, or only one gas reaches the threshold, the controller (5) does not send a signal; when the side reaction gases in the upper layers of the positive electrode storage tank (1) and the negative electrode storage tank (2) both reach the threshold, the controller (5) sends a signal, the air pump (6) starts working, and the side reaction gases in the upper layers of the positive electrode storage tank (1) and the negative electrode storage tank (2) are pumped into the gas storage tank (9); S3, the pressure sensor (10) inside the gas storage tank (9) transmits a signal to the controller (5), and when the pressure value reaches the designed stop threshold, the compressor (8) is controlled to stop running; S4, after the compressor (8) stops operating, the controller (5) issues an opening command for the air inlet valve (11), and the compressed gas inside the gas storage tank (9) enters the fuel cell (3) for reaction; S5. Based on the signal from the gas flow sensor (12) on the gas transmission pipeline, the controller (5) adjusts the opening of the intake valve (11) in real time, thereby adjusting the reaction rate inside the fuel cell (3); S6, the reaction products generated during the reaction of the side reaction gas in the fuel cell (3) until the reaction stops are temporarily stored in the stirrer (4); S7. The controller (5) adjusts the opening of the liquid return valve (13) according to the type and stoichiometric ratio of the reactants to ensure that the reaction products are distributed in the liquid return according to the amount of the reactants.

Images