A split type liquid flow battery system and control method thereof

Abstract

The present invention relates to the field of liquid flow batteries, and provides a split liquid flow battery system and a control method thereof. The split liquid flow battery system includes a first battery module and a second battery module that can operate independently or synchronously and can be switched to a series mode, and the first battery module and the second battery module are connected to an electrolyte storage device; the split liquid flow battery system also includes a control module, and the control module is used to control the first battery module and / or the second battery module to a simultaneous charging mode, a simultaneous discharging mode, a decoupling mode or a monitoring mode. The split liquid flow battery system and the control method thereof provided by the present invention have good adaptability of the battery in different situations, are conducive to the improvement of key performance, can flexibly adjust the operating mode according to demand during operation, and have good application effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow batteries, and in particular relates to a split liquid flow battery system and a control method thereof. Background Art

[0002] As a new type of electrochemical energy storage technology, flow batteries have the advantages of independent energy and power design, long cycle life, and rapid response. They have developed large-capacity, low-cost, and high-efficiency electrochemical energy storage technologies to achieve temporal and spatial decoupling of renewable energy generation and grid loads, and have attracted much attention in the field of large-scale energy storage. Compared with traditional secondary batteries, flow batteries use external liquid electrolytes as active materials to store electrical energy through the redox reaction of ions between positive and negative electrodes. The electrolyte is driven by a pump to circulate inside the battery, completing charge transfer and generating current. Currently, representative flow battery systems include all-vanadium flow batteries (VRFBs), iron-chromium flow batteries (ICFBs), polysulfide bromine flow batteries, and new organic system flow batteries.

[0003] At present, the core performance indicators of flow batteries, such as power density and cycle life, still cannot fully meet the needs of practical applications, and their commercialization process is subject to certain constraints. Researchers started from different levels such as electrodes and ion exchange membranes. In terms of electrodes, new electrode materials such as nanocarbon materials, metal oxides, and nitrogen-doped carbon have been developed, which greatly improved the reaction kinetics and catalytic activity; in terms of ion exchange membranes, key diaphragm materials such as Nafion membranes and PBI membranes have been optimized to improve ion selectivity and mass transfer characteristics; a new aqueous solution electrolyte system has been introduced to inhibit cross-contamination of active substances. In terms of electrolytes, the capacity of the battery can be restored by mixing or updating the electrolyte.

[0004] Although these works have promoted the progress of liquid flow battery technology from different aspects and continuously improved its performance, there are still problems with liquid flow batteries. The operating parameters during battery operation, including the state of charge of the positive and negative half-cells, the standard electrode potential difference between the positive and negative batteries, etc., cannot be detected. On the other hand, it is difficult for the same electrode to meet the requirements of some different requirements during the charging and discharging processes. For example, there is a more obvious hydrogen evolution phenomenon on the negative electrode side during the charging process, so some catalysts that inhibit hydrogen evolution are needed, such as lead metal, and such catalysts are easier to dissolve in the electrolyte during the discharge process. On the other hand, during the operation of the battery, according to the variable requirements of the load, there are occasional situations where the charging power or discharge power exceeds the requirements. Once it exceeds the design requirements of the battery discharge or charging, the electrode will burn out or the battery will not operate normally.

[0005] In addition, during the battery charging process, the migration of water and ions is generally concentrated from the negative electrode to the positive electrode. During the discharge process, the migration of water and ions is concentrated from the positive electrode to the negative electrode, but the speeds of the two do not match. The amount of migration during the charging process is greater than the amount of migration during the discharge process. Therefore, after a long period of cycling, there will be a significant increase in volume and ion concentration on the positive electrode side. This leads to a mismatch in capacity between the positive and negative electrode sides. In response to these problems, traditional liquid flow batteries usually use a fixed battery structure and electrolyte ratio. Parameters such as electrode area and electrolyte volume are determined during the design, and it is difficult to flexibly adjust according to different power and capacity requirements. For the problems mentioned above, this integrated design method cannot bring out the greatest advantages of liquid flow batteries.

[0006] Compared with traditional solid-state batteries, flow batteries use flowable electrolytes instead of traditional solid active materials. Therefore, the electrolyte is separated from the power module as an active material, so that it can be optimized separately during the charging and discharging process. And the electrolyte after charging and discharging is collected to obtain key information such as the open circuit voltage of the battery and the charge state of the positive and negative active materials. Although the traditional integrated charging and discharging design of batteries can save the cost of the battery stack, it is often impossible to obtain key status information of the battery in some specific cases. It limits the adaptability of the battery in different situations and the improvement of key performance, and the operating mode cannot be flexibly adjusted according to demand during operation. Summary of the invention

[0007] The purpose of the present invention is to overcome at least one of the deficiencies of the above-mentioned prior art, and to provide a split liquid flow battery system and a control method thereof. The battery has good adaptability in different situations, is conducive to the improvement of key performance, can flexibly adjust the operating mode according to demand during operation, and has good application effect.

[0008] The technical solution of the present invention is: a split liquid flow battery system, comprising a first battery module and a second battery module that can operate independently or synchronously and can be switched to a series mode, wherein the first battery module and the second battery module are connected to an electrolyte storage device;

[0009] The split liquid flow battery system also includes a control module, which is used to control the first battery module and / or the second battery module to a simultaneous charging mode, a simultaneous discharging mode, a decoupling mode or a monitoring mode.

[0010] Specifically, the first battery module has an electrolyte outlet, the second battery module has an electrolyte inlet, the electrolyte outlet and the electrolyte inlet have connecting pipelines and a control valve, and the control valve is connected to the control module.

[0011] Specifically, the control valve is a multi-way valve and is connected to the electrolyte storage device.

[0012] Specifically, the electrolyte storage device includes a first storage device and a second storage device, the first battery module includes a first positive electrode portion, a first diaphragm and a first negative electrode portion, and the second battery module includes a second positive electrode portion, a second diaphragm and a second negative electrode portion; the first diaphragm is arranged between the first positive electrode portion and the first negative electrode portion, and the second diaphragm is arranged between the second positive electrode portion and the second negative electrode portion.

[0013] Specifically, the liquid outlet end of the first liquid storage device is connected to one side of the first negative electrode portion through a first liquid outlet pipe, the other side of the first negative electrode portion is connected to one side of the second negative electrode portion through a first pipeline, and the other side of the second negative electrode portion is connected to the first liquid storage device through a first reflux pipe;

[0014] The liquid outlet end of the second liquid storage device is connected to one side of the first positive electrode part through a second liquid outlet pipe, the other side of the first positive electrode part is connected to one side of the second positive electrode part through a second pipeline, and the other side of the second positive electrode part is connected to the second liquid storage device through a second reflux pipe.

[0015] Specifically, the liquid outlet end of the first liquid storage device is connected to one side of the first negative electrode portion and one side of the second negative electrode portion through a three-way valve, and the other side of the first negative electrode portion and the other side of the second negative electrode portion are connected to the first liquid storage device through a three-way valve;

[0016] The liquid outlet end of the second liquid storage device is connected to one side of the first positive electrode portion and one side of the second positive electrode portion through a three-way valve, and the other side of the first positive electrode portion and the other side of the second positive electrode portion are connected to the second liquid storage device through a three-way valve.

[0017] Specifically, the first battery module and / or the second battery module are connected to a voltage sensor, a current sensor, a temperature sensor, a flow sensor and a pressure sensor.

[0018] The present invention also provides a control method for a split liquid flow battery system, using the above-mentioned split liquid flow battery system;

[0019] By controlling the switching unit, one of the first battery module and the second battery module is switched to a battery module in a working state, and the load or power supply is connected to the battery module in the working state. The switching unit is controlled to switch the other of the first battery module and the second battery module to a battery module in an idle state, and the battery module in the idle state is used as a monitoring module.

[0020] Specifically, the switching unit is controlled to switch one of the first battery module and the second battery module to a battery module in a charging state, and the power source is connected to the battery module in the charging state; the switching unit is controlled to switch the other of the first battery module and the second battery module to a battery module in a discharging state, and the load is connected to the battery module in the discharging state;

[0021] Alternatively, the first battery module and the second battery module are switched to series-connected battery modules in a charging state or a discharging state by controlling the switching unit.

[0022] Specifically, the first battery module and the second battery module are switched to a battery performance research mode with a constant SOC by controlling the switching unit;

[0023] Alternatively, the first battery module and the second battery module are switched to a constant current fast charging and constant voltage trickle slow charging parallel mode by controlling the switching unit.

[0024] The present invention provides a split liquid flow battery system and a control method thereof. The liquid flow battery adopts a main battery and an auxiliary battery (backup battery) to be separately designed, including two battery modules with similar structures, the same or different materials and can work independently. The two battery modules can share a fluid electrolyte, and the electrolyte can circulate between the battery and the liquid storage tank. A control module (battery control switching unit) is set between the two batteries to realize flexible switching and multi-mode operation of the main battery and the auxiliary battery. The battery management and monitoring system controls the switching unit to perform the operation mode of the main battery and the auxiliary battery according to the working condition requirements. The two can be connected in parallel (high power mode) or in series (high capacity mode). The two can also realize the operation of the main battery, and the auxiliary battery can be switched to act as a monitoring battery. The two can also realize the operation of the rechargeable battery, the discharge of the auxiliary battery, and the separate optimization of charging and discharging according to the requirements. Compared with the traditional liquid flow battery, the present invention can optimize the structure, material and operation mode of the main battery and the auxiliary battery respectively, reduce the maintenance cost; the multiple working modes are flexibly switched, the operation efficiency and key performance are improved, and the application effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a connection diagram of a split liquid flow battery system provided by an embodiment of the present invention;

[0027] Figure 2Schematic diagram of voltage and charge-discharge capacity in Example 1 of the present invention;

[0028] Figure 3 is a schematic diagram of SOC in Example 1 of the present invention;

[0029] Figure 4 is a schematic diagram of voltage and charge-discharge capacity in Example 2 of the present invention;

[0030] Figure 5 Schematic diagram of charge and discharge curves in Example 2 of the present invention;

[0031] Figure 6 is a schematic diagram of voltage and charge-discharge capacity in Example 3 of the present invention;

[0032] Figure 7 is a schematic diagram of charging and discharging power and charging and discharging time in Example 3 of the present invention;

[0033] Figure 8 is a schematic diagram of the relationship between voltage, current density and power density in Example 4 of the present invention;

[0034] Fig. 9 It is a schematic diagram of voltage and charge-discharge capacity in Example 5 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] It should be noted that the terms “setting” and “connecting” should be understood in a broad sense. For example, it can be directly setting or connecting, or it can be indirectly setting or connecting through a central component or a central structure.

[0037] In addition, in the embodiments of the present invention, if there are terms indicating orientation or positional relationships such as "longitudinal", "transverse", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., they are based on the orientation or positional relationships or conventional placement states or usage states shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure, feature, device or element referred to must have a specific orientation or positional relationship, nor must it be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] The various specific technical features and embodiments described in the specific implementation methods can be combined in any suitable manner unless there is any contradiction. For example, different implementation methods can be formed by combining different specific technical features / embodiments. In order to avoid unnecessary repetition, the various possible combinations of the specific technical features / embodiments in the present invention will not be described separately.

[0039] like Figure 1 As shown, a split liquid flow battery system provided by an embodiment of the present invention includes a first battery module 10 and a second battery module 20 that can operate independently or synchronously and can be switched to a series mode. The first battery module 10 and the second battery module 20 can be divided into a main battery and an auxiliary battery. The first battery module 10 and the second battery module 20 are connected to an electrolyte storage device (liquid storage tank); the split liquid flow battery system also includes a control module, which is used to control the first battery module 10 or / and the second battery module 20 to a simultaneous charging mode, a simultaneous discharging mode, a decoupling mode or a monitoring mode. The previous single battery design has been changed, and a split arrangement is adopted as a split battery. The electrolyte of the split battery can be connected in series through the main battery and the auxiliary battery. During the operation, the operation mode can be flexibly adjusted according to the needs to meet the requirements of different scenarios. The battery has good adaptability in different situations, which is conducive to the improvement of key performance and has a good application effect.

[0040] Specifically, the first battery module 10 has an electrolyte outlet, the second battery module 20 has an electrolyte inlet, and the electrolyte outlet and the electrolyte inlet have connecting pipes and a control valve, so that the first battery module 10 and the second battery module 10 can be switched to a series mode, and the control valve is connected to the control module.

[0041] Specifically, the control valve is a multi-way valve and is connected to the electrolyte storage device. The control module can be used to control the multi-way valve. Specifically, the electrolyte storage device includes a first storage device 31 and a second storage device 32, the first battery module 10 includes a first positive electrode portion 11, a first diaphragm 12 and a first negative electrode portion 13, and the second battery module 20 includes a second positive electrode portion 21, a second diaphragm 22 and a second negative electrode portion 23. The first diaphragm 12 is arranged between the first positive electrode portion 11 and the first negative electrode portion 13, and the second diaphragm 22 is arranged between the second positive electrode portion 21 and the second negative electrode portion 23.

[0042] Specifically, the liquid outlet of the first liquid storage device 31 is connected to one side of the first negative electrode portion 13 through a first liquid outlet pipe, the other side of the first negative electrode portion 13 is connected to one side of the second negative electrode portion 23 through a first pipeline, and the other side of the second negative electrode portion 23 is connected to the first liquid storage device 31 through a first reflux pipe; the liquid outlet of the second liquid storage device 32 is connected to one side of the first positive electrode portion 11 through a second liquid outlet pipe, the other side of the first positive electrode portion 11 is connected to one side of the second positive electrode portion 21 through a second pipeline, and the other side of the second positive electrode portion 21 is connected to the second liquid storage device 32 through a second reflux pipe. To share the electrolyte.

[0043] In a specific application, the liquid outlet end of the first liquid storage device 31 is connected to one side of the first negative electrode portion 13 and one side of the second negative electrode portion 23 through a three-way valve, and the other side of the first negative electrode portion 13 and the other side of the second negative electrode portion 23 are connected to the first liquid storage device 31 through a three-way valve; the liquid outlet end of the second liquid storage device 32 is connected to one side of the first positive electrode portion 11 and one side of the second positive electrode portion 21 through a three-way valve, and the other side of the first positive electrode portion 11 and the other side of the second positive electrode portion 21 are connected to the second liquid storage device 32 through a three-way valve. By switching the three-way valve, the operating mode of the first battery module 10 and the second battery module 20 can also be controlled.

[0044] Specifically, the first battery module 10 and / or the second battery module 20 are connected to a voltage sensor, a current sensor, a temperature sensor, a flow sensor and a pressure sensor to enhance the adaptability of the flow battery to different working conditions, improve the operating performance of the battery, realize the regulation of different battery states, and monitor the electrolyte and electrode states.

[0045] Specifically, the first battery module 10 and the second battery module 20, each battery module can be composed of a single or several single cells connected in series, and the single cells are filled with porous electrodes and ion exchange membranes. The first battery module 10 and the second battery module 20 are respectively connected to their own independent electrolyte storage tanks, and the electrolyte can circulate between the battery module and the storage tank through a pump. At the same time, the outlet of the first battery module 10 is connected to the inlet of the second battery module 20, and the electrolyte can flow from the storage tank to the first battery module 10, then flow out of the first battery module 10 and flow to the second battery module 20, and finally flow out of the second battery module 20 and flow to the storage tank. A battery switching unit (switching valve) is installed between the first battery module 10 and the second battery module 20, such as a plurality of three-way valves or multi-way valves are set on the electrolyte delivery pipeline, and the flow path of the electrolyte is changed by controlling the switch state of the valve. In the single-battery mode, the control valve makes the first battery module 10 and the second battery module 20 connected to their respective liquid storage tanks; in the charge-discharge decoupling mode, the control valve makes the first battery module 10 and the second battery module 20 connected in series, and at the same time cuts off the connection between the second battery module 20 and its liquid storage tank. The switch operation of the valve can be instructed by the battery control system (control module) and implemented by the fluid control system (such as pumps, actuators, etc.), so as to realize the flexible switching between the first battery module 10 and the second battery module 20. When switched to the single-battery mode, the first battery module 10 and the second battery module 20 are only connected to their respective liquid storage tanks, and the two batteries are not connected to each other, and each performs the charging and discharging process; when switched to the charge-discharge decoupling mode, the first battery module 10 is connected to the second battery module 20 in addition to its own liquid storage tank (first liquid storage device 31), but is not connected to the liquid storage tank (second liquid storage device 32) of the second battery module 20.

[0046] In specific applications, the split flow battery system has a variety of operating modes, such as:

[0047] (1) Mode 1: Monitoring mode. The first battery module 10 is the main battery, responsible for charging and discharging. The first battery module 10 can be connected to a battery tester 41 (for detecting battery charging and discharging). The second battery module 20 is an auxiliary battery, responsible for monitoring the operating status of the battery, and is connected to a battery tester 41 (for OCV measurement). After the first battery module 10 is charged and discharged, the electrolyte does not flow directly into the liquid storage tank, but returns to the liquid storage tank after passing through the auxiliary battery. At this time, the open circuit voltage of the flow battery is detected by monitoring the open circuit voltage flowing through the auxiliary battery. The SOC state of the battery can be obtained through the value of the open circuit battery and the SOC-battery voltage diagram formulated based on the previous experimental data. The auxiliary battery actually measures the open circuit voltage when no current is applied. The state of charge of the electrolyte can be inferred from the open circuit voltage when no current is applied. At the same time, by using a non-operating battery to monitor parameters such as SOC and OCV in the charge and discharge state, the regulation of the battery operation process can be enhanced; in addition, when the battery has severe capacity decay, the system maintenance can be simplified by pumping new electrolyte in another storage tank into the first battery module 10 and the second battery module 20, without the need to shut down for replacement.

[0048] (2) Mode 2: The first battery module 10 is a rechargeable battery, and the second battery module 20 is a discharge battery. The electrodes and diaphragms of the first battery module 10 can regulate and optimize the charging process. The diaphragm can be designed to have high ion selectivity, preferentially allowing charge carrier ions (such as H+, etc.) to pass through, while blocking the penetration of other active substances. This can improve the charging efficiency and reduce the cross-contamination of active substances; the use of electrode materials with high catalytic activity, the electrodes are provided with precious metal nanoparticles, transition metal compounds, etc., can reduce the activation energy barrier during the charging process, accelerate charge transfer and electrochemical reaction kinetics, thereby improving the battery efficiency and capacity during the charging process; and the materials of the second battery module 20 are optimized according to the needs of the discharge process, such as surface modification of the diaphragm, introducing hydrophilic groups and catalytic layers into the second diaphragm 22, etc., can improve the wettability and catalytic activity of the electrode / electrolyte interface, and improve the discharge performance; or the use of electrode materials with high catalytic activity, such as precious metal nanoparticles, transition metal oxides, etc., can accelerate the electrochemical reaction kinetics during the discharge process, thereby improving the efficiency and capacity during the discharge process.

[0049] (3) Mode 3: simultaneous charging mode and simultaneous discharging mode. The two batteries are connected in series. When the load power is detected to be too high, the data acquisition system controls the battery charging and discharging instrument to start, and the second battery module 20 is charged while only the first battery module 10 is charged. The valve is controlled to allow the electrolyte to flow through the first battery module 10 and the second battery module 20 in sequence, forming a series flow path, so that the two batteries can be connected in series at the same time to increase the power of charging and discharging. For example, during the charging process, the electrolyte that has been charged by the battery flowing through the first battery module 10 can continue to be charged after flowing through the second battery module 20. On the one hand, the charging power can be increased, and on the other hand, the utilization rate of the charged electrolyte can be increased. Similarly, during the discharging process, the electrolyte that has been discharged by the battery flowing through the first battery module 10 can continue to be discharged after flowing through the second battery module 20. On the one hand, the discharge power can be increased, and on the other hand, the utilization rate of the discharged electrolyte can be increased.

[0050] (4) Mode 4: Constant SOC battery performance research mode. For liquid flow batteries, it is sometimes necessary to study the performance of the battery at certain specific SOCs. However, after the charge and discharge currents are applied, the SOC state of charge of the battery will inevitably change. Therefore, for constant SOC research, it is often necessary to prevent the electrolyte from returning to the battery storage tank after charging and discharging, resulting in a huge waste of electrolyte. In order to maintain the stability of the entire charge and discharge state, it is often necessary to configure a lot of electrolyte. For some liquid flow battery systems with relatively expensive electrolytes, such as all-vanadium or organic liquid flow batteries, the cost of the entire test will be extremely expensive. In the present invention, a symmetrical reverse current test method can be used. For example, when the first battery module 10 is a rechargeable battery, the second battery module 20 applies a completely opposite and equal discharge current. After the SOC increased after charging in 1 passes through the equal current discharge of the second battery module 20, the increased SOC will be reduced to the state of the storage tank before entering the first battery module 10, so that the battery state of charge is completely restored.

[0051] (5) Mode 5: Parallel mode of constant current fast charging and constant voltage trickle charging, and constant current fast discharge + constant voltage slow discharge. The energy density of liquid flow batteries is low, while the price of active materials is high. In order to improve the utilization rate of the electrolyte of the battery, it is generally necessary to charge the electrolyte to a full state as much as possible during the charging process, and to completely release the chemical energy carried by the electrolyte during the discharge process. During the charging process, if a large current is used for charging throughout the process, a significant hydrogen evolution reaction will occur in the later stage of charging. If a constant current is used first, and then the electrolyte is allowed to flow back to the liquid storage tank, and then pumped from the liquid storage tank into the battery by a pump, it will not only increase the charging time, but also increase the pumping work from the liquid storage tank to the inside of the battery. Therefore, the first battery module 10 can be charged with a large current constant current, and the charged electrolyte enters the second battery module 20 for constant voltage trickle charging. In this way, after passing through the first battery module 10 and the second battery module 20, the electrolyte can basically reach a full charge state. Also during the discharge process, the first battery module 10 performs a large-current constant-current discharge, and after entering the second battery module 20, performs a constant-voltage trickle discharge, so that after passing through the second battery module 20, the energy carried by the electrolyte can be basically completely released.

[0052] It can be understood that a split liquid flow battery system provided in an embodiment of the present invention may also include multiple battery modules, that is, the battery modules may be two or more. When three or more battery modules are provided, each battery module may operate independently or synchronously and may be switched to a series mode. The control module may control each battery module and may switch or independently control each battery module to a charging mode, a discharging mode, a decoupling mode or a monitoring mode.

[0053] Compared with the traditional flow battery design, the present invention has the following advantages:

[0054] (1) First, the traditional liquid flow battery uses a single battery, and the parameters such as electrode type, electrolyte volume, and ratio are determined during the design, which is difficult to adjust according to different power and capacity conditions. The present invention adopts a dual-battery design or multiple batteries, which can regulate two different batteries according to different working conditions, such as optimizing and regulating the charging and discharging processes separately, and different batteries output different powers, etc., which enhances the battery performance while improving the battery's adaptability to different working conditions;

[0055] (2) The split battery design and independent battery structure are also conducive to the rapid isolation and diagnosis of faults, which improves the maintainability of the battery. When capacity decay or failure occurs, traditional flow batteries need to shut down the battery system and disassemble and assemble all components, which is quite cumbersome. By utilizing the split battery design, it is possible to switch to another battery to continue operation, and the faulty battery can be removed and repaired, realizing non-stop battery maintenance;

[0056] (3) Compared with the traditional battery structure, which can only monitor performance indicators such as current, voltage, efficiency, and capacity, but cannot monitor the open circuit voltage and SOC status of the electrolyte during charging and discharging, the split battery design can measure the characteristics of the electrolyte on another battery and monitor the health status of the electrolyte in real time to regulate the operation of the battery;

[0057] (4) The present invention utilizes a split battery structure, and new electrolyte or electrolyte stabilizer can be introduced through another battery when the battery is running, thereby slowing down the capacity decay of the battery, improving the capacity retention rate of the battery, and extending the operating life of the battery.

[0058] The present invention also provides a control method for a split liquid flow battery system, using the above-mentioned split liquid flow battery system;

[0059] By controlling the switching unit, one of the first battery module 10 and the second battery module 20 is switched to a battery module in a working state, and the load or power supply is connected to the battery module in the working state. The switching unit is controlled to switch the other of the first battery module 10 and the second battery module 20 to a battery module in an idle state, and the battery module in the idle state is used as a monitoring module.

[0060] Specifically, the switching unit is controlled to switch one of the first battery module 10 and the second battery module 20 to a battery module in a charging state, and the power source is connected to the battery module in the charging state. The switching unit is controlled to switch the other of the first battery module 10 and the second battery module 20 to a battery module in a discharging state, and the load is connected to the battery module in the discharging state.

[0061] Alternatively, the first battery module 10 and the second battery module 20 are switched to series-connected battery modules in a charging state or a discharging state by controlling the switching unit.

[0062] Specifically, the first battery module 10 and the second battery module 20 are switched to a battery performance research mode with a constant SOC by controlling the switching unit;

[0063] Alternatively, the first battery module 10 and the second battery module 20 are switched to a constant current fast charging and constant voltage trickle slow charging parallel mode by controlling the switching unit.

[0064] Under normal operating conditions, the control module (battery management system) controls the switching unit to connect the load or power supply to the working battery module according to the operating requirements, and switches the other battery module to the idle state. The idle battery can enter the monitoring mode, and measure the key parameters such as OCV and SOC of the electrolyte in real time by connecting to a battery tester or electrochemical workstation. When the working battery module has performance degradation or failure, the switching unit can quickly switch the load or power supply to another battery module to ensure uninterrupted operation of the battery module. In addition, the battery module can adopt other operating modes. According to the performance status of each battery module, the battery module with better performance can be used for charging or charging first. The other battery module enters the regeneration mode, and additives or new electrolytes can be introduced to restore performance.

[0065] By adopting a dual / multi-battery split design, the battery structure parameters, such as electrode specific surface area, catalyst type and loading, electrolyte flow rate, etc., can be independently optimized according to the respective needs of charging and discharging, so that they can adapt to high-capacity or high-power conditions respectively, and combined with the control module and switching unit, the different states of the battery module can be optimized and regulated, which is conducive to the realization of adaptive adjustment of the battery under all working conditions. The split battery realizes intelligent monitoring of the battery electrolyte charge state, improves safety and reliability, and the collected data is synchronized with the battery data. The system integrates multi-parameter sensors such as voltage, current, temperature, flow, pressure, etc., and introduces electrolyte charge and open circuit voltage estimation models, which can facilitate the dynamic monitoring of all parameters of the battery charging and discharging process.

[0066] Moreover, the series mode can better adapt to the needs of variable power charging and discharging. When the input power increases, the second battery module 20 can switch from the electrolyte charge state monitoring mode to an additional charging or discharging battery, so as to better adapt to the conditions of variable power operation. The split battery structure is conducive to the replacement and maintenance of key battery components. When a failure occurs, it can be switched to another battery in time to continue operation, realizing uninterrupted maintenance and replacement, and reducing battery maintenance. The split battery can adopt the opposite charging and discharging mode of the dual battery, and can maintain the constant SOC of the electrolyte when the amount of electrolyte is small, meeting the needs of the mechanism research of the flow battery. The dual battery can adopt a high current + trickle charging mode of constant current and then constant voltage after the electrolyte enters the battery. After a cycle of the electrolyte entering the battery system, it can be fully charged or release electrical energy, which reduces the charging time and the pump work of the whole process, and the application effect is good.

[0067] The present invention is further described below in conjunction with specific embodiments.

[0068] Embodiment 1:

[0069] In this embodiment, the first battery module 10 and the second battery module 20 adopt the same design, the ion exchange membrane used is Nafion 212, the electrode is graphite felt, and the area of ​​the active electrode is 2 cm×2 cm. In the first battery module 10, 100 mA·cm -2 The current density is 5 mL min -1 cm -2 , the second battery module 20 is in an open circuit state, and the charge and discharge voltage of the battery and the open circuit voltage are detected. Figure 2 and Figure 3 As shown in the figure, it can be seen that by matching the actual battery charge and discharge voltage with the OCV voltage, the SOC state corresponding to the actual battery charge and discharge capacity can be obtained. The charge and discharge voltage of the first battery module 10 and the voltage of the second battery module 20 can be synchronized in real time. According to the voltage of detection 2, we compared it with the SOC of the battery and found that according to Figure 2 and Figure 3 As shown, the one-to-one correspondence between the battery voltage and the battery state of charge, that is, the electrolyte concentration in the battery, at any charging and discharging time can be obtained.

[0070] Embodiment 2:

[0071] In this embodiment, the first battery module 10 is defined as a rechargeable battery, and the second battery module 20 is defined as a discharge battery. The ion exchange membrane used in the first battery module 10 is Nafion 212, and the electrode is a graphite felt loaded with a catalyst of metal lead nanoparticles. The ion exchange membrane used in the second battery module 20 is Nafion 211, and the electrode is graphite felt loaded with a catalyst of metal bismuth particles. For comparison, the first battery module 10 and the second battery module 20 were tested in which both the catalyst graphite felt electrode loaded with metal lead nanoparticles and the Nafion 212 ion exchange membrane and the catalyst graphite felt electrode loaded with metal bismuth nanoparticles and the Nafion 211 ion exchange membrane were used. All batteries were charged at 100 mA cm -2 The current density was 5 mL min-1 and the flow rate was 5 mL min-1. -1 cm -2 , the area of ​​the active electrode is 2 cm×2 cm. Figure 4As shown in the figure, when both the charging battery and the discharging battery use catalyst graphite felt electrodes loaded with metal lead nanoparticles, the charging capacity is 583.14 mAh and the discharging capacity is 433.80 mAh; when both the charging battery and the discharging battery use catalyst graphite felt electrodes loaded with metal bismuth nanoparticles, the charging capacity is 511.24 mAh and the discharging capacity is 500.37 mAh. When the charging battery uses catalyst graphite felt electrodes loaded with metal lead nanoparticles and the discharging battery uses catalyst graphite felt electrodes loaded with metal bismuth nanoparticles, as shown in the figure, the charging capacity is 583.14 mAh and the discharging capacity is 433.80 mAh; when both the charging battery and the discharging battery use catalyst graphite felt electrodes loaded with metal lead nanoparticles and the discharging battery uses catalyst graphite felt electrodes loaded with metal bismuth nanoparticles, as shown in the figure, the charging capacity is 511.24 mAh and the discharging capacity is 500.37 mAh. Figure 5 As shown, at this time, the battery charging capacity is 576.45 mAh and the discharge capacity is 511.23 mAh. By comparison, it is shown that decoupling the charging and discharging process, regulating and optimizing them separately, and using catalyst graphite felt electrodes with lead nanoparticles with higher charging capacity and catalyst graphite felt electrodes with bismuth nanoparticles with higher discharge capacity can effectively improve the battery's charge and discharge capacity compared to graphite felt electrodes with lead nanoparticles or bismuth nanoparticles.

[0072] Embodiment 3:

[0073] In this embodiment, the first battery module 10 is defined as the main battery, and the second battery module 20 is defined as the backup battery. The ion exchange membrane used is Nafion 212, the electrode is graphite felt, and the area of ​​the active electrode is 2 cm×2 cm. Under low load conditions, 100 mA·cm -2 The first battery module 10 is charged and discharged with a current density of 5 mL min -1 cm -2 The second battery module 20 is not operated, and only the electrolyte flows. The test results are as follows Figure 6 and Figure 7 As shown. At this time, the battery charging time is 1198 s, the battery discharging time is 1193 s, and the battery output power is 2.64 W; under high load conditions, the second battery module 20 is connected, and the first battery module 10 and the second battery module 20 are operated in series, the battery charging time is shortened to 523 s, the battery discharging time is shortened to 598 s, and the battery output power is 5.28 W. The comparison shows that the simultaneous operation of two batteries in series can effectively increase the charging and discharging power, shorten the charging and discharging time, flexibly deal with the situation where the load is unstable and the power is too high, and ensure the stable operation of the battery.

[0074] Embodiment 4:

[0075] In this embodiment, the first battery module 10 is defined as a rechargeable battery, and the second battery module 20 is defined as a discharge battery. Nafion 212 ion exchange membrane is used, the electrode is graphite felt, and the area of ​​the active electrode is 2 cm×2 cm. 100 mA·cm -2The first battery module 10 is charged with a current density of 100 mA·cm -2 The second battery module 20 is discharged at a current density of 5 mL min -1 cm -2 , measure the power density of the battery at SOC=0.5. Figure 8 As shown in the figure, for comparison, the SOC state of charge of the ordinary charge-discharge battery changes due to the electrolyte flowing back to the storage tank for mixing. The power density of the battery is measured to be 1.24 W / cm 2 When the split flow battery system was used, the battery power density was measured to be 2.54 W / cm 2 , which is comparable to the power density of 2.58 W / cm measured using a large amount of electrolyte. 2 The deviation is small, indicating that the split battery system can directly detect the power density of the battery under a constant SOC state.

[0076] Embodiment 5:

[0077] In this embodiment, the first battery module 10 is defined as a constant current charge-discharge battery, and the second battery module 20 is defined as a constant voltage charge-discharge battery. Nafion 212 ion exchange membrane is used, the electrode is graphite felt, and the area of ​​the active electrode is 2 cm×2 cm. Under low load conditions, 100 mA·cm -2 The first battery module 10 is charged and discharged at a constant current density of 1.65 V, and the second battery module 20 is charged and discharged at a constant voltage of 5 mL min -1 cm -2 .like Fig. 9 As shown, for comparison, the charging capacity of the ordinary charge-discharge battery is 490 mAh, the discharging capacity is 481 mAh, the charging time is 1038 s, and the discharging time is 1011 s; while the charging capacity of the split battery is 545 mAh, the discharging capacity is 527 mAh, the charging time is 1321 s, and the discharging time is 1146 s. Compared with the ordinary battery, the charging capacity is increased by 10.1%, and the discharging capacity is increased by 8.72%, while the total charge and discharge time is only increased by about 4 min, indicating that by adopting the constant current + constant voltage trickle charge and discharge method, the utilization rate of the electrolyte can be effectively improved, and the battery charge and discharge capacity can be increased. At the same time, by running 20 cycles and using gas chromatography to detect the hydrogen concentration, it was found that under constant current charging and discharging, the hydrogen concentration was 746 ppm, while under constant current + constant voltage trickle charging and discharging, the hydrogen concentration was 124 ppm, indicating that this charging and discharging method can effectively reduce the concentration of hydrogen and inhibit the occurrence of side reactions.

[0078] In the present invention, the flow battery adopts a separate design of the main battery and the auxiliary battery, including two battery modules with similar structures but different materials and working independently. The two batteries share a fluid electrolyte, and the electrolyte can circulate between the battery and the liquid storage tank. A battery control switching unit is set between the two batteries to realize flexible switching and multi-mode operation of the main battery and the auxiliary battery. The battery management and monitoring system controls the switching unit to perform the operation mode of the main battery and the auxiliary battery according to the working conditions. The two can be connected in parallel (high power mode), in series (high capacity mode), and the two can also realize the operation of the main battery, and the auxiliary battery acts as a monitoring battery. The two can also realize the operation of the rechargeable battery, the discharge of the auxiliary battery, and the separate optimization of charging and discharging according to the needs. Compared with the traditional flow battery, the present invention can optimize the structure, material and operation mode of the main battery and the auxiliary battery respectively, reduce the maintenance cost; multiple working modes can be flexibly switched to improve the operation efficiency.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A split liquid flow battery system, characterized in that: It includes a first battery module and a second battery module that can be operated independently or synchronously and can be switched to a series mode, wherein the first battery module and the second battery module are connected to an electrolyte storage device; The split liquid flow battery system further includes a control module, which is used to control the first battery module and / or the second battery module to a simultaneous charging mode, a simultaneous discharging mode, a decoupling mode or a monitoring mode; In the monitoring mode, the first battery module is the main battery, responsible for charging and discharging. The first battery module is connected to a battery tester for detecting battery charging and discharging. The second battery module is the auxiliary battery, responsible for monitoring the operating status of the battery. It is connected to a battery tester for OCV measurement. After the first battery module is charged and discharged, the electrolyte returns to the liquid storage tank after passing through the auxiliary battery. The open circuit voltage of the flow battery is detected by monitoring the open circuit voltage of the auxiliary battery. The SOC state of the battery is obtained through the value of the open circuit battery and the SOC-battery voltage diagram formulated according to the previous experimental data. In the simultaneous charging mode and the simultaneous discharging mode, the first battery module and the second battery module are operated in series. When it is detected that the load power is too high, the data acquisition system controls the battery charging and discharging instrument to start, and the second battery module is charged on the basis of charging only the first battery module, and the valve is controlled to make the electrolyte flow through the first battery module and the second battery module in sequence to form a series flow path, so that the two batteries are operated in series at the same time. During the charging process, the electrolyte that has been charged by the battery flowing through the first battery module flows through the second battery module to continue charging. During the discharging process, the electrolyte that has been discharged by the battery flowing through the first battery module flows through the second battery module to continue discharging. In the charge-discharge decoupling mode, the first battery module is connected to the second battery module in addition to the first liquid storage device, but is not connected to the second liquid storage device of the second battery module; The control module is also used to control the first battery module and / or the second battery module to a constant current fast charging and constant voltage trickle slow charging parallel mode, a constant current fast discharge and a constant voltage slow discharge discharge mode: the first battery module performs a large current constant current charging, and the charged electrolyte enters the second battery module for constant voltage trickle charging. During the discharge process, the first battery module performs a large current constant current discharge, and after the electrolyte enters the second battery module, a constant voltage trickle discharge is performed.

2. A split liquid flow battery system as claimed in claim 1, characterized in that: The first battery module has an electrolyte outlet, the second battery module has an electrolyte inlet, the electrolyte outlet and the electrolyte inlet have connecting pipelines and a control valve, and the control valve is connected to the control module.

3. A split liquid flow battery system as claimed in claim 2, characterized in that: The control valve is a multi-way valve and is connected to the electrolyte storage device.

4. A split liquid flow battery system as claimed in claim 2 or 3, characterized in that: The electrolyte storage device includes a first storage device and a second storage device, the first battery module includes a first positive electrode portion, a first diaphragm and a first negative electrode portion, and the second battery module includes a second positive electrode portion, a second diaphragm and a second negative electrode portion; the first diaphragm is arranged between the first positive electrode portion and the first negative electrode portion, and the second diaphragm is arranged between the second positive electrode portion and the second negative electrode portion.

5. A split liquid flow battery system as claimed in claim 4, characterized in that: The liquid outlet end of the first liquid storage device is connected to one side of the first negative electrode portion through a first liquid outlet pipe, the other side of the first negative electrode portion is connected to one side of the second negative electrode portion through a first pipeline, and the other side of the second negative electrode portion is connected to the first liquid storage device through a first reflux pipe; The liquid outlet end of the second liquid storage device is connected to one side of the first positive electrode part through a second liquid outlet pipe, the other side of the first positive electrode part is connected to one side of the second positive electrode part through a second pipeline, and the other side of the second positive electrode part is connected to the second liquid storage device through a second reflux pipe.

6. A split liquid flow battery system as claimed in claim 4, characterized in that: The liquid outlet end of the first liquid storage device is connected to one side of the first negative electrode portion and one side of the second negative electrode portion through a three-way valve, and the other side of the first negative electrode portion and the other side of the second negative electrode portion are connected to the first liquid storage device through a three-way valve; The liquid outlet end of the second liquid storage device is connected to one side of the first positive electrode portion and one side of the second positive electrode portion through a three-way valve, and the other side of the first positive electrode portion and the other side of the second positive electrode portion are connected to the second liquid storage device through a three-way valve.

7. A split liquid flow battery system as claimed in claim 1, characterized in that: The first battery module and / or the second battery module are connected to a voltage sensor, a current sensor, a temperature sensor, a flow sensor and a pressure sensor.

8. A control method for a split liquid flow battery system, characterized in that: A split liquid flow battery system according to any one of claims 1 to 7; By controlling the switching unit, one of the first battery module and the second battery module is switched to a battery module in a working state, and the load or power supply is connected to the battery module in the working state. The switching unit is controlled to switch the other of the first battery module and the second battery module to a battery module in an idle state, and the battery module in the idle state is used as a monitoring module.

9. A control method for a split liquid flow battery system as claimed in claim 8, characterized in that: By controlling the switching unit, one of the first battery module and the second battery module is switched to a battery module in a charging state, and a power source is connected to the battery module in the charging state; and the switching unit is controlled to switch the other of the first battery module and the second battery module to a battery module in a discharging state, and a load is connected to the battery module in the discharging state; Alternatively, the first battery module and the second battery module are switched to series-connected battery modules in a charging state or a discharging state by controlling the switching unit.

10. The control method of a split liquid flow battery system according to claim 8, characterized in that: Switching the first battery module and the second battery module to a battery performance research mode with a constant SOC by controlling the switching unit; Alternatively, the first battery module and the second battery module are switched to a constant current fast charging and constant voltage trickle slow charging parallel mode by controlling the switching unit.

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