阅读说明：本技术 所有钒液流电池的先进电解液混合方法 (Advanced electrolyte mixing method for all vanadium flow batteries ) 是由 安吉洛·丹齐 卡洛·阿尔贝托·布罗韦罗 詹卢卡·皮拉齐尼 毛里齐奥·塔皮 于 2018-03-27 设计创作，主要内容包括：液流电池具有电化学电池组、正极电解液、负极电解液、正极电解液槽和负极电解液槽。所述正极电解液和所述负极电解液分别储存在所述正极槽和负极槽中。正极电解液泵、负极电解液泵、混合泵嵌入旁路管道或专用回路中。所述正极槽和所述负极槽借助于连接管相互连接,所述连接管嵌入紧靠电解液液面的正上方。(The flow battery has an electrochemical cell stack, a positive electrolyte, a negative electrolyte, a positive electrolyte tank, and a negative electrolyte tank. The positive electrode electrolyte and the negative electrode electrolyte are stored in the positive electrode tank and the negative electrode tank, respectively. The positive electrolyte pump, the negative electrolyte pump and the mixing pump are embedded into a bypass pipeline or a special loop. The positive electrode tank and the negative electrode tank are connected to each other by means of a connecting pipe, which is inserted immediately above the electrolyte level.)

1. A flow battery of the type comprising at least an electrochemical cell stack 1, a positive electrolyte 5, a negative electrolyte 4, a positive electrolyte tank 3 and a negative electrolyte tank 2, wherein the positive electrolyte 5 is stored in the positive electrolyte tank 3 and wherein the negative electrolyte 4 is stored in the negative electrolyte tank 2; and the flow battery further comprises a positive electrolyte pump 6, a negative electrolyte pump 7, a bypass pipe 13 embedded below the electrolyte level, and a mixing pump 14 arranged in the bypass pipe 13, the bypass pipe 13 connecting the positive electrolyte tank 3 to the negative electrolyte tank 2; and wherein the positive electrode tank 3 and the negative electrode tank 2 are connected to each other by means of a connecting pipe 15, the connecting pipe 15 being embedded immediately above the electrolyte level.

2. A flow battery according to claim 1, wherein the positive electrode tank 3 and the negative electrode tank 2 are connected to each other by means of a connecting pipe 15 immediately above the electrolyte level, e.g. 2cm above, in order to return excess electrolyte accumulated during mixed mode.

3. A flow battery of the type comprising at least an electrochemical cell stack 1, a positive electrolyte 5, a negative electrolyte 4, a positive electrolyte tank 3 and a negative electrolyte tank 2, wherein the positive electrolyte 5 is stored in the positive electrolyte tank 3 and wherein the negative electrolyte 4 is stored in the negative electrolyte tank 2; the improvement comprises a mixing pump 14 embedded in a dedicated pipe 16 having a suction end 18 and a discharge end 17, and wherein said suction end 18 is arranged deep in said negative electrolyte tank 2, and wherein said discharge end 17 is positioned to contact the top of said positive electrolyte at a set level in said positive electrolyte tank 3.

Technical Field

The present invention relates to a flow battery, and in particular to a novel flow battery module in which the balance of the equipment is strongly simplified.

Background

A flow battery is a type of rechargeable battery in which an electrolyte containing one or more dissolved electroactive species flows through an electrochemical cell that converts chemical energy directly into electrical energy. The electrolyte is stored in an external tank and pumped through the cells of the reactor.

Redox flow batteries have the advantages of flexible layout (due to the separation between power and energy components), long life cycle, fast response time, no need for smooth charging, and no harmful emissions.

Flow batteries are used in stationary applications with energy requirements between 1kWh and several MWh: they are used to smooth the load of the grid, during the night, where the battery is used to accumulate energy at low cost and return it to the grid when it is more expensive, and also to accumulate power from renewable sources (such as solar and wind energy) and then provide it during energy demand peak periods.

In particular, vanadium redox batteries comprise a set of electrochemical cells in which two electrolytes are separated by a proton exchange membrane. Both electrolytes are based on vanadium: the electrolyte in the positive half cell contains VO4< + > and VO 5 < + > ions, and the electrolyte in the negative half cell contains V <3+ > and V <2+ > ions. The electrolyte can be prepared in several ways, for example by electrolytic dissolution of vanadium pentoxide (V2O5) in sulfuric acid (H2SO 4). The solution used remains strongly acidic. In a vanadium flow battery, the two half-cells are furthermore connected to a reservoir containing a very large volume of electrolyte which is circulated through the cells by means of a pump. This circulation of liquid electrolyte requires a certain space occupation and limits the possibility of using vanadium flow batteries in mobile applications, in fact limiting them to large fixed installations.

During charging of the battery, vanadium is oxidized in the positive half-cell, converting VO4< + > to VO <5+ >. The removed electrons are transferred to the negative half-cell where they reduce vanadium from V <3+ > to V <2+ >. During operation, the process occurs in reverse, and a potential difference of 1.41V is obtained in an open circuit at 25 ℃.

Vanadium redox cells are the only cells that accumulate electrical energy in an electrolyte and not on a plate or electrode (as commonly occurs in all other cell technologies).

Unlike all other batteries, in vanadium redox batteries, the electrolyte contained in the cell, once charged, is not subject to auto-discharge, whereas the part of the electrolyte fixed within the electrochemical core is subject to auto-discharge over time.

The amount of electrical energy stored in the cell is determined by the volume of electrolyte contained in the cell.

According to a particular constructive solution that is particularly effective, vanadium redox batteries comprise a set of electrochemical cells in which two electrolytes, separated from each other by a polymer membrane, flow. Both electrolytes consist of an acidic solution of dissolved vanadium. The positive electrolyte contains V <5+ > and V <4+ > ions, and the negative electrolyte contains V <2+ > and V <3+ > ions. During charging of the battery, in the positive half-cell, vanadium is oxidized, while in the negative half-cell, vanadium is reduced. During the discharge step, the process is reversed. Connecting a plurality of cells in electrical series allows increasing the voltage across the battery, which is equal to the number of cells multiplied by 1.41V.

During the charging phase, the pump is opened to flow the electrolyte in the electrochemically relevant cell in order to store energy. The electrical energy applied to the electrochemical cell facilitates proton exchange by means of the membrane, thereby charging the battery.

During the discharge phase, the pump is turned on, causing the electrolyte to flow inside the electrochemical cell, creating a positive pressure in the relevant cell, thus releasing the accumulated energy.

During operation of the battery, there is migration of electrolyte, promoted by the electromotive force of the process, from one compartment to another compartment in the stack of cells making up the battery pack. This causes a change in the level of electrolyte in the tanks, with the level in one tank rising and the level in the other tank falling.

The purpose is to keep the level of electrolyte in the tanks balanced, and to place a bypass line connecting the two tanks below the level.

When the battery is operated for a long period of time, concentration imbalance of vanadium species constituting the electrolyte occurs. Therefore, it is necessary to mix the two electrolytes at predetermined periodic intervals to ensure equal concentrations of vanadium in the anode and cathode. It is evident that by mixing the two electrolytes, the cell goes into a non-operating state and the voltage delivered is equal to zero (no difference in potential across the cell) since both compartments contain vanadium in the oxidation state 3.5. To return to the discharged battery state of V3+ and V4+, the energy consumption must equal half the charge to condition the electrolyte in both tanks. Only after conditioning is it possible to recharge the battery.

In order to perform such electrolyte mixing operations, it is necessary to have an embedded hydraulic circuit that interconnects the inlet and outlet of the cell in order to allow the electrolyte flows to mix together.

The hydraulic hybrid circuit is constituted by several valves, manually or electrically operated, which can be subject to faults indeed resulting from their limited use and, in addition, it increases the overall cost of the battery.

The object of the present invention is to solve the problems described above, designing a flow battery that completely eliminates valves and includes a limited hydraulic circuit. This design is also less expensive than batteries of known technology and is less likely to be subject to failure and malfunction.

Disclosure of Invention

The object of the present invention is to provide a vanadium redox flow battery module having an electrochemical cell stack 1, a positive electrolyte 5, a negative electrolyte 4, a positive electrolyte tank 3, and a negative electrolyte tank 2, the positive electrolyte 5 and the negative electrolyte 4 being stored in the tanks 2 and 3, respectively. At the same time, the anolyte 5 and the catholyte 4 each pass through the electrochemical cell stack 1 via a connecting duct to form a respective circuit, which is also indicated by arrows in fig. 3. The pumps 6 and 7 are typically mounted on connecting pipes to continuously feed the respective electrolytes to the electrodes in the battery 1. The bypass pipe 13 is inserted below the liquid level of the electrolytic solution to connect the positive electrode electrolytic solution tank 3 to the negative electrode electrolytic solution tank 2 in order to maintain the liquid level balance of the two electrolytic solutions contained in the respective tanks 2 and 3. In the bypass pipe 13, a mixing pump 14 is inserted, which is turned off in the operation mode, and in the mixing mode, the mixing pump 14 is turned on, and the negative electrode electrolyte 4 contained in the negative electrode electrolyte tank 2 is pumped into the positive electrode electrolyte tank 3 in the direction indicated by the arrow pointing to the right in fig. 3, and the two electrolytes are mixed together. During this mixing phase, an increase in the electrolyte level in the positive electrolyte tank 3 occurs. The positive electrode tank 3 and the negative electrode tank 2 are connected to each other by a connection pipe 15, and the connection pipe 15 is arranged immediately above the electrolyte liquid surface, for example, 2cm above the electrolyte liquid surface.

As shown in fig. 4, in the mixed mode in which the mixing pump 14 is turned on, the electrolyte level in the positive electrode electrolyte tank 3 increases, and the excess electrolyte in the tank 3 is returned to the negative electrode electrolyte tank 2 by means of the connection pipe 15. The positive and negative electrolytes are distinguished by different shading, as seen in fig. 4. When the mixing mode is over and the pump 14 is switched off, an equilibrium of the liquid levels in the two tanks occurs by means of the bypass pipe 13, maintaining the electrolyte level equilibrium and providing an effective electrolyte mixture.

As shown in fig. 5, the mixing pump 14 may alternatively be embedded in a dedicated pipe loop 16 above the electrolyte level. The pipe loop 16 has one end 18 in the tank 2 and an opposite end 17 in the tank 3. During cell operation, the mixing pump 14 is turned off and the conduit loop 16 is not used as a bypass for electrolyte level balancing. In this view, end 18 serves as a suction end. The suction pipe end 18 as seen in fig. 5 is deeper in the electrolyte tank 2 than the discharge pipe end 17 in the tank 3, where the end 17 contacts the top of the electrolyte at a default liquid level.

As shown in fig. 6, after completion of the mixing mode when the mixing pump 14 is turned off, the equalization of the liquid level occurs via the pipe loop 16 as shown by the return arrow until the liquid level of the electrolyte 5 reaches the end 17 (conduit 17). Air will enter the conduit loop 16 causing evacuation and thus ending the electrolyte balance. The suction pipe end 18 as seen in fig. 6 is deeper in the electrolyte tank 2 than the discharge pipe end 17 in the tank 3, where the end 17 contacts the top of the electrolyte at a default liquid level.

It is another object of the present invention to provide a flow battery that is relatively simple and less expensive and safer in application.

Drawings

Further features and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of a flow battery according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

FIG. 1 is a schematic diagram showing a conventional vanadium redox flow battery in an operating mode;

FIG. 2 is a schematic diagram showing a conventional vanadium redox flow battery in a hybrid mode;

FIG. 3 is a schematic diagram of a vanadium flow battery according to the present invention in an operational mode wherein a mixing pump is embedded in the bypass;

FIG. 4 is a schematic diagram of a vanadium flow battery according to the present invention in a hybrid mode, wherein a hybrid pump is embedded in the bypass;

FIG. 5 is a schematic diagram of a vanadium flow battery according to the present invention having an overhead tube with two ends, one of which is a deeper suction tube near the bottom in the electrolyte tank 2, and a drain tube 17 in tank 3 contacts the top of the electrolyte at a default level; and is

Fig. 6 is a schematic diagram of a vanadium flow battery according to the present invention, wherein the leveling of the electrolyte occurs via another overhead pipe.

Detailed Description

In fig. 3, a flow battery module according to the invention is shown, said module comprising at least an electrochemical cell stack 1, a positive electrolyte 5, a negative electrolyte 4, a positive electrolyte tank 3 and a negative electrolyte tank 2. The positive electrode electrolyte 5 and the negative electrode electrolyte 4 are stored in the tank 3 and the tank 2, respectively. A positive electrolyte pump 6 and a negative electrolyte pump 7 are provided. The bypass pipe 13 is inserted below the electrolyte liquid level to connect the positive electrode electrolyte tank 3 to the negative electrode electrolyte tank 2, and the mixing pump 14 is inserted in the bypass pipe 13. The positive electrode tank 3 and the negative electrode tank 2 are connected to each other by means of a connecting pipe 15, wherein the connecting pipe 15 is arranged immediately above, for example 2cm above, the electrolyte level.

In the bypass pipe 13, a mixing pump 14 is inserted, which is turned off in the operation mode, and in the mixing mode, the mixing pump 14 is turned on, and the negative electrode electrolyte 4 contained in the negative electrode electrolyte tank 2 is pumped into the positive electrode electrolyte tank 3 in the direction indicated by the arrow pointing to the right in fig. 3, and the two electrolytes are mixed together. During this mixing phase, an increase in the electrolyte level in the positive electrolyte tank 3 occurs. The positive electrode tank 3 and the negative electrode tank 2 are connected to each other by a connection pipe 15, and the connection pipe 15 is arranged immediately above the electrolyte liquid surface, for example, 2cm above the electrolyte liquid surface.

In fig. 3, in a flow battery module according to the invention, in order to maintain electrolyte level equilibrium in the cell, a bypass conduit 13 can be placed below the liquid level, connecting both electrolyte tank 2 and electrolyte tank 3, allowing the flow of electrolyte in either of two opposite directions.

In fig. 3, in a flow battery module according to the invention, the mixing pump 14 is switched off during the operating mode.

As shown in fig. 4, in the mixed mode in which the mixing pump 14 is turned on, the electrolyte level in the positive electrode electrolyte tank 3 increases, and the excess electrolyte in the tank 3 is returned to the negative electrode electrolyte tank 2 by means of the connection pipe 15. The positive and negative electrolytes are distinguished by different shading, as seen in fig. 4. When the mixing mode is over and the pump 14 is switched off, an equilibrium of the liquid levels in the two tanks occurs by means of the bypass pipe 13, maintaining the electrolyte level equilibrium and providing an effective electrolyte mixture.

In fig. 4, in the flow battery module according to the present invention, the mixing pump 14 is turned on during the mixing mode, the negative electrolyte contained in the negative electrolyte tank 2 is pumped into the positive electrolyte tank 3, and the two electrolytes are mixed together.

In fig. 4, in a flow battery module according to the invention, during the hybrid mode, an increase in the electrolyte level in the positive electrolyte tank 3 occurs.

In fig. 4, in a flow battery module according to the invention, the positive electrode tank 3 and the negative electrode tank 2 are connected to each other by means of a connecting pipe 15, and the connecting pipe 15 is embedded immediately above, for example 2cm above, the electrolyte level.

In fig. 4, in a flow battery module according to the invention, during the mixing mode, the excess mixed electrolyte pumped in the positive electrolyte tank 3 is returned to the negative electrolyte tank 2 by means of the connecting pipe 15. When the mixing mode is over and the pump 14 is switched off, by means of the bypass 13, an equilibrium of the liquid levels in the two tanks occurs, maintaining the electrolyte level equilibrium and providing an effective electrolyte mixture.

As shown in fig. 5, the mixing pump 14 may alternatively be embedded in a dedicated pipe loop 16 above the electrolyte level. The pipe loop 16 has one end 18 in the tank 2 and an opposite end 17 in the tank 3. During cell operation, the mixing pump 14 is turned off and the conduit loop 16 is not used as a bypass for electrolyte level balancing. In this view, end 18 serves as a suction end. The suction pipe end 18 as seen in fig. 5 is deeper in the electrolyte tank 2 than the discharge pipe end 17 in the tank 3, where the end 17 contacts the top of the electrolyte at a default liquid level.

In fig. 5, in a flow battery module according to the invention, in an alternative, the mixing pump 14 is arranged in a dedicated pipe loop 16, not necessarily below the electrolyte level (in fig. 5, the horizontal part is arranged above the electrolyte level, and the two ends 17 and 18 are arranged near the top (end 17) and near the bottom (end 18), respectively, of the electrolyte level, the positive tank 3 and the negative tank 2 are connected to each other by means of a connecting pipe 15, the connecting pipe 15 is arranged immediately above the electrolyte level, for example 2cm above.

Further, the power conversion unit 11, for example, a DC/AC converter may be used in the vanadium redox flow battery, and the power conversion unit 11 is electrically connected to the battery pack 1 via the positive and negative connection lines, respectively, and the power conversion unit 11 may also be electrically connected to the external input power source 12 and the external load 10, respectively, so as to convert AC power generated by the external input power source 12 into DC power to charge the vanadium redox flow battery or convert DC power discharged by the vanadium redox flow battery into AC power to output to the external load 10.

As shown in fig. 6, after completion of the mixing mode when the mixing pump 14 is turned off, the equalization of the liquid level occurs via the pipe loop 16 as shown by the return arrow until the liquid level of the electrolyte 5 reaches the end 17 (conduit 17). Air will enter the conduit loop 16 causing evacuation and thus ending the electrolyte balance. The suction pipe end 18 as seen in fig. 6 is deeper in the electrolyte tank 2 than the discharge pipe end 17 in the tank 3, where the end 17 contacts the top of the electrolyte at a default liquid level. The electrolyte level will be maintained in equilibrium and an effective electrolyte mixture will also be provided.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Having thus described the invention, it will be obvious to those skilled in the art that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.