A high-concentration vanadium battery stack operation strategy

Abstract

The application discloses a high-concentration all-vanadium battery electric pile operation strategy and relates to the technical field of high-concentration all-vanadium battery electrolyte operation. The application adopts all-vanadium electrolyte with a concentration greater than 2 mol / L; and further comprises an electric pile anti-blocking step: the electric pile anti-blocking step is composed of one-time small-current deep discharge, one to four times of small-current charging deep discharge, one-time small-power charging and discharging and one-time full-power charging and discharging in sequence.

Description

Technical Field

[0001] This invention relates to the field of high-concentration all-vanadium battery electrolyte operation technology, specifically, a stack operation strategy for high-concentration all-vanadium batteries. Background Technology

[0002] Vanadium redox batteries, with their high energy conversion efficiency, long lifespan, adjustable capacity according to user requirements, high safety, and environmental friendliness, have become one of the most promising methods for large-scale energy storage, including wind and solar power, as well as peak shaving and valley filling. Vanadium redox batteries typically consist of an electrolyte, electrodes, and a storage tank. Many factors influence their performance, but the electrolyte's performance has the most significant impact. As vanadium redox batteries increasingly move towards large-scale, high-capacity production, the electrolyte concentration is also being developed accordingly.

[0003] However, when the concentration of pentavalent vanadium ions in the electrolyte is high, on the one hand, the charging and discharging process generates more heat, which promotes the self-polymerization of pentavalent vanadium ions, leading to crystallization and affecting the stability of the electrolyte; on the other hand, during the use of high-concentration all-vanadium electrolyte, due to the excessively high concentration of pentavalent vanadium ions, a large amount of rust-yellow deposits will adhere to the pipes near the positive electrode at high temperatures, and green gel-like substances will form on the carbon felt and flow channels of the battery stack, thereby causing a significant reduction in the electrolyte flow rate of the entire battery system and affecting the charging and discharging efficiency.

[0004] In actual use of high-concentration vanadium electrolyte, in order to ensure that the electrolyte is kept at a low temperature and to avoid the electrolyte flow rate being reduced due to blockage, the cooling method is increased. This inevitably causes the cooling equipment to consume more energy, resulting in increased energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a stack operation strategy for high-concentration vanadium-ion batteries to solve the problem that existing high-concentration vanadium-ion electrolytes, when operating at temperatures above 45°C, will experience electrolyte precipitation, resulting in reduced electrolyte flow during charging and discharging.

[0006] To solve the above problems, the present invention employs the following technical means: A stack operation strategy for a high-concentration all-vanadium battery, using an all-vanadium electrolyte with a concentration greater than 2 mol / L; It also includes a stack anti-blocking procedure: consisting of a low-current deep discharge, one to four low-current deep discharges, a low-power charge-discharge, and a full-power charge-discharge.

[0007] Preferably, the low-current deep discharge is performed using a current of 3~10A, and the discharge termination voltage is 0V.

[0008] Furthermore, the low-current charging deep discharge uses a constant voltage charging current of 60 mA / cm2-80 mA / cm2.

[0009] Furthermore, the low-current charging deep discharge achieves a charging degree of 50% to 60% of the normal capacity.

[0010] Furthermore, the discharge process of the low-current charging deep discharge uses a discharge current of 10A and a cutoff voltage of 0V.

[0011] Furthermore, before performing low-power charging and discharging, it is necessary to level the electrolyte levels at both the positive and negative electrodes.

[0012] Furthermore, the low-power charging and discharging is performed using a constant voltage at 70% to 75% of the maximum current density, and discharging is performed using 55% to 65% of the full power.

[0013] Furthermore, the full-power charging and discharging process uses a constant voltage of 313V, the full-power charging and discharging process uses maximum power discharge, the termination voltage is set to 192V, and the electrolyte temperature is maintained at 40℃~43℃ during the discharge process.

[0014] Furthermore, a backwashing operation is provided between the low-power charge / discharge and the full-power charge / discharge, which includes sequential air backwashing and deionized water washing.

[0015] Furthermore, the air backwashing is carried out using an air compressor with an exhaust volume of 2 m³ / min and an exhaust pressure of 80 kPa; The deionized water washing is carried out using a magnetic pump with a head of 15m and a flow rate of 60L / min.

[0016] The present invention has the following beneficial effects during use: During operation with high-concentration electrolytes, the system temperature rises due to the exothermic charging and discharging. After a period of use, rust-yellow vanadium pentoxide precipitate appears near the pipes through which the positive electrode electrolyte flows. Meanwhile, after the negative electrode electrolyte flows through the fuel cell stack, a large amount of colloidal vanadium oxysulfate precipitate is generated in the carbon felt and flow channels, thus clogging the carbon felt and flow channels in the fuel cell stack. The combination of these two factors significantly reduces the electrolyte flow rate at both the positive and negative electrodes, affecting charging and discharging efficiency. This application, however, can completely dissolve the aforementioned precipitates after deep discharge with a small current. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0020] A stack operation strategy for a high-concentration all-vanadium battery, using an all-vanadium electrolyte with a concentration greater than 2 mol / L; It also includes a stack anti-blocking procedure: consisting of a low-current deep discharge, one to four low-current deep discharges, a low-power charge-discharge, and a full-power charge-discharge.

[0021] The aforementioned anti-clogging steps involve dissolving the precipitates generated by the electrolyte during operation through specific procedures after the battery has been running for a period of time, thereby preventing blockage caused by the electrolyte becoming non-crystallized due to high-temperature operation.

[0022] During the low-current deep discharge process, the covalent bonds formed by the conversion of ionic bonds in the positive electrode vanadium ions due to high-temperature charging are broken during the low-current deep discharge, transforming them back into ionic bonds. Then, in the second step of low-current charging and discharging, the ionic bonds formed in the first step, which were broken into covalent bonds, gain electrons and change from pentavalent to tetravalent, thus eliminating the precipitate formed in the positive electrode electrolyte. In the third step of low-power charging and discharging, the colloidal vanadium oxysulfate mixture blocking the carbon felt and pipes in the stack is activated. After activation, the colloidal vanadium oxysulfate is dissolved using the fourth step of full-power discharge. Simultaneously, vanadium trioxide generated at the negative electrode due to operation also loses electrons to form trivalent vanadium ions. Through the final two charging and discharging processes, the large amount of colloidal vanadium oxysulfate and the small amount of vanadium trioxide generated in the negative electrode electrolyte due to operation are completely dissolved, thus clearing the entire battery system.

[0023] Specifically, the low-current deep discharge uses a current of 3A to 10A for discharge, with a discharge termination voltage of 0V. The optimal discharge current is selected as 3A, and its main function is to activate the descaling system.

[0024] Then, the low-current deep discharge is performed using a constant voltage charging current of 60 mA / cm²-80 mA / cm², and the charging degree of the aforementioned low-current deep discharge is 50% to 60% of the normal capacity. Preferably, the low-current deep discharge is performed using a constant voltage charging current of 70 mA / cm², and charged to 60% of the normal capacity. The discharge current used in the low-current deep discharge process is 10 A, and the cutoff voltage is 0 V.

[0025] In practice, currents less than 60 mA / cm² are insufficient to activate the system in high-concentration environments because they cannot break the aforementioned covalent bonds, resulting in poor precipitate removal. However, currents greater than 80 mA / cm² are less effective. 2 At high concentrations of vanadium ions, complexation occurs in the positive electrode electrolyte, leading to the formation of numerous flocculent substances. Specifically, this accelerates the conversion of pentavalent vanadium ions to tetravalent vanadium ions, resulting in flocculent precipitation. When the current exceeds 100 mA / cm², the resulting complexes dissolve. However, when the current exceeds 100 mA / cm², it severely hinders the disruption of covalent bonds by the low current, causing preferential conversion of the existing pentavalent vanadium ions in the system. Consequently, the system fails to effectively dissolve and precipitate the vanadium ions, thus disrupting the covalent bonds within the system.

[0026] Furthermore, before performing low-power charging and discharging, it is necessary to level the electrolyte levels at both the positive and negative electrodes.

[0027] Furthermore, the low-power charging and discharging is performed using a constant voltage at 70%~75% of the maximum current density, and discharging at 55%~65% of full power. Preferably, it is performed using a constant voltage at 70% of the maximum current density and discharging at 65% of full power. Thus, in the process of treating the colloidal vanadium oxysulfate generated at the negative electrode, a low-current constant voltage charging is first performed, followed by low-power discharging. During this process, the colloidal vanadium oxysulfate is treated by activating the electrolyte with a low current, causing the covalent bonds in the formed colloidal vanadium oxysulfate and vanadium trioxide to break and form ionic bonds, and allowing the complexed ionic bonds to detach and form a free state.

[0028] After activation, it is then cleaned by full-power discharge. Specifically, the full-power charge-discharge process uses 313V constant voltage charging, the full-power discharge process uses maximum power discharge, the stop voltage is set to 192V, and the electrolyte temperature is maintained at 40℃~43℃ during the discharge process.

[0029] Additionally, a backwashing operation can be performed between low-power charging / discharging and full-power charging / discharging, as needed, using the following steps: Utilizing an exhaust volume of 2m 3The air compressor with an exhaust pressure of 80 kPa provides power output at a speed of / min.

[0030] Stop the battery system, disconnect the electrolyte inlet and outlet ports of the battery stack, connect the hoses, connect the electrolyte outlet hose to the air compressor, and connect the electrolyte inlet hose to the plastic container. Start the air compressor, control the exhaust volume, and allow air to slowly enter the battery stack to discharge the treatment fluid. Stop the air compressor when there is no more fluid flowing from the hoses.

[0031] Deionized water washing was performed using a magnetic pump with a head of 15m and a flow rate of 60L / min.

[0032] After the fuel cell stack undergoes air backwashing, the electrolyte inlet hose is connected to a magnetic pump, and the electrolyte outlet hose is connected to a plastic container. The magnetic pump is started, and the water flow is controlled to slowly enter the fuel cell stack for cleaning. Residual treatment solution is then discharged. The outlet hose is observed; once the water flow is clear, the magnetic pump is stopped. This completes the deionized water wash.

[0033] In the aforementioned steps, the fuel cell backwashing operation can be adaptively selected based on the degree of the aforementioned discharge steps. The technical solution of this invention can not only be completed without any fuel cell backwashing, but also perform fuel cell backwashing. It offers greater adaptability.

[0034] Furthermore, the electrolyte used in the aforementioned embodiments was purchased from Sichuan Energy Investment Yongfu Energy Storage Technology Co., Ltd., and is a 2.5 mol / L high-concentration vanadium electrolyte.

[0035] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stack operation strategy for a high-concentration all-vanadium battery, characterized in that: A vanadium-containing electrolyte with a concentration greater than 2 mol / L was used. It also includes a stack anti-blocking procedure: consisting of a low-current deep discharge, one to four low-current deep discharges, a low-power charge-discharge, and a full-power charge-discharge. The low-current deep discharge uses a current of 3~10A to discharge, and the discharge termination voltage is 0V. The low-current charge-discharge depth is 60 mA / cm. 2 -80 mA / cm 2 The current is used for constant voltage charging, and the charging degree of the low current charging deep discharge is 50% to 60% of the normal capacity. The discharge current used in the low current charging deep discharge process is 10A and the cutoff voltage is 0V. The low-power charging and discharging is performed using a constant voltage at 70% to 75% of the maximum current density, and discharging is performed using 55% to 65% of the full power. The full-power charging and discharging process uses a constant voltage of 313V for charging, and the full-power charging and discharging process uses maximum power discharge. The termination voltage is set to 192V, and the electrolyte temperature is maintained at 40℃~43℃ during the discharge process.

2. The stack operation strategy for a high-concentration all-vanadium battery according to claim 1, characterized in that: Before performing low-power charging and discharging, the electrolyte levels at the positive and negative electrodes need to be leveled.

3. The stack operation strategy for a high-concentration all-vanadium battery according to claim 1, characterized in that: Between the low-power charge / discharge and the full-power charge / discharge, a backwashing operation is also provided, which includes sequential air backwashing and deionized water washing.

4. The stack operation strategy for a high-concentration all-vanadium battery according to claim 3, characterized in that: The air backwash utilizes an exhaust volume of 2m³. 3 The air compressor operates at a discharge pressure of 80 kPa per minute. The deionized water washing is carried out using a magnetic pump with a head of 15m and a flow rate of 60L / min.