A flow battery stack structure

Abstract

The present invention provides a structure for a flow battery stack. This structure increases the length of the common pipelines between parallel-connected cells in the stack by increasing the number of common pipelines within the stack, while also ensuring that the positive or negative electrodes of adjacent cells are not connected to the same common electrolyte pipeline. The increased common pipeline resistance reduces leakage loss and improves stack efficiency. The common pipeline resistance can be flexibly designed based on the number of cells in the stack to regulate leakage current. Furthermore, the added common electrolyte pipeline actually increases the effective flow cross-sectional area of ​​the common pipeline, reduces pipeline flow resistance, increases electrolyte flow, and reduces concentration polarization in the stack.

Description

Technical Field

[0001] The present invention relates to a liquid flow battery stack structure, and in particular to a flow mode of electrolyte in the stack and a stack structure. Background Art

[0002] As environmental pollution worsens, countries around the world are increasingly aware of its significant impact on human society. Large-scale utilization of renewable energy has become a top priority in adjusting the energy mix. However, renewable energy suffers from intermittent, unstable, and uncontrollable characteristics. Rashly integrating it onto the grid on a large scale will inevitably impact the power grid, and in severe cases, even cause it to collapse. Therefore, a highly reliable and safe device is needed to improve the quality of renewable energy power, significantly increase its utilization rate, and reduce the widespread curtailment of wind and solar power. Energy storage technology has emerged as a result. Common technologies such as pumped hydro storage, flywheel storage, and lead-acid and lithium-ion battery storage have all developed. However, these technologies are hindered by geographical constraints and safety concerns, hindering their widespread adoption. Flow batteries, with their high efficiency, deep charge and discharge capabilities, independent power and capacity design, long life, inherent safety, and cost-effective lifecycle, have gradually become the technology of choice for large-scale, long-duration energy storage and have made significant progress over the past two decades.

[0003] A flow battery system primarily consists of batteries, electrolyte storage tanks, electrolyte, and piping systems. Batteries are the most critical component in a flow battery system, determining system performance and reliability and serving as the key location for chemical reactions. High-performance stacks require high power density while maintaining high energy efficiency, requiring improvements in both the stack's Coulombic efficiency and voltage efficiency. Voltage efficiency is primarily affected by cell polarization; Coulombic efficiency is affected by discharge caused by contact between the positive and negative electrolytes within the stack through seals or ion membranes, resulting in a decrease in discharge capacity. Coulombic efficiency is also affected by stack leakage current, which is primarily determined by the number of cells, current, and the resistance of the electrolyte supply main line and electrolyte distribution lines within the electrode frame. For high-power flow battery stacks, the high current, the number of cells reaching hundreds or even hundreds, and the reduction in pipe resistance due to thinner electrode thickness all have a greater impact on the stack's Coulombic efficiency. If not properly controlled, the Coulombic efficiency of the battery stack can be significantly reduced. In severe cases, it can cause the electrolyte to overheat and damage the battery stack and electrolyte pipelines. Summary of the Invention

[0004] To control the impact of stack leakage current on stack performance and reliability, the present invention provides a flow battery stack structure. The stack comprises two left and right end plates, and single cells located between the two end plates and separated from left to right by bipolar plates. The single cells comprise a positive electrode located within a through-hole in the center of a positive electrode frame, an ion-conducting membrane, and a negative electrode located within a through-hole in the center of a negative electrode frame, stacked sequentially from left to right.

[0005] The number of cells separated by the bipolar plates is M, where M is an integer greater than or equal to 4.

[0006] At corresponding positions on the left end plate and the bipolar plate, there are N through holes as the positive electrode electrolyte inlet, N through holes as the positive electrode electrolyte outlet, N through holes as the negative electrode electrolyte inlet, and N through holes as the negative electrode electrolyte outlet. The number of positive electrode electrolyte inlets, positive electrode electrolyte outlets, negative electrode electrolyte inlets and negative electrode electrolyte outlets on the left end plate and the bipolar plate are the same; if M is an even number, N is 2 to M / 2; if M is an odd number, N is 2 to (M+1) / 2.

[0007] From left to right, a positive electrode electrolyte inlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte inlet channels; from left to right, a positive electrode electrolyte outlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte outlet channels; from left to right, a negative electrode electrolyte inlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte inlet channels; from left to right, a negative electrode electrolyte outlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte outlet channels.

[0008] From left to right, one end of the positive electrode in the 1st to Mth single cells is connected to one channel of the N positive electrolyte inlet channels, and the other end is connected to one channel of the N positive electrolyte outlet channels; and the positive electrodes of adjacent single cells are respectively connected to different channels of the N positive electrolyte inlet channels, and the positive electrodes of adjacent single cells are respectively connected to different channels of the N positive electrolyte outlet channels; and the other end of the single cell connected to a positive electrolyte inlet channel is connected to a positive electrolyte outlet channel.

[0009] From left to right, one end of the negative electrode in the 1st to Mth single cells is connected to one channel of the N negative electrode electrolyte inlet channels, and the other end is connected to one channel of the N negative electrode electrolyte outlet channels; and the negative electrodes of adjacent single cells are respectively connected to different channels of the N negative electrode electrolyte inlet channels, and the negative electrodes of adjacent single cells are respectively connected to different channels of the N negative electrode electrolyte outlet channels; and the other end of the single cell connected to a negative electrode electrolyte inlet channel is connected to a negative electrode electrolyte outlet channel.

[0010] A similar flow battery stack structure includes two left and right end plates, and single cells located between the two end plates and separated by bipolar plates from left to right.

[0011] The single cell comprises a positive electrode located in a through hole in the middle of a positive electrode frame, an ion conducting membrane, and a negative electrode located in a through hole in the middle of a negative electrode frame, which are stacked in sequence from left to right.

[0012] The number of cells separated by bipolar plates is M*N;

[0013] At corresponding positions on the left end plate and the bipolar plate, there are N through holes serving as the positive electrode electrolyte inlet, N through holes serving as the positive electrode electrolyte outlet, N through holes serving as the negative electrode electrolyte inlet, and N through holes serving as the negative electrode electrolyte outlet. The number of positive electrode electrolyte inlets, positive electrode electrolyte outlets, negative electrode electrolyte inlets, and negative electrode electrolyte outlets on the left end plate and the bipolar plate are the same.

[0014] From left to right, a positive electrode electrolyte inlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte inlet channels; from left to right, a positive electrode electrolyte outlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte outlet channels; from left to right, a negative electrode electrolyte inlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte inlet channels; from left to right, a negative electrode electrolyte outlet at the corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte outlet channels.

[0015] From left to right, one end of the positive electrode in the Kth cell and the N+Kth cell is connected to the Kth channel of the N positive electrode electrolyte inlet channels, and the other end is connected to the Kth channel of the N positive electrode electrolyte outlet channels; from left to right, one end of the negative electrode in the Kth cell and the N+Kth cell is connected to the Kth channel of the N negative electrode electrolyte inlet channels, and the other end is connected to the Kth channel of the N negative electrode electrolyte outlet channels; K represents an integer from 1 to N.

[0016] In the above-mentioned stack structure, N positive electrolyte inlet channels and N positive electrolyte outlet channels are respectively connected to the positive electrolyte storage tank outside the stack; N negative electrolyte inlet channels and N negative electrolyte outlet channels are respectively connected to the negative electrolyte storage tank outside the stack.

[0017] In the above-mentioned battery stack structure, M is an integer greater than or equal to 5; N is an integer greater than or equal to 3.

[0018] The present invention has the following advantages:

[0019] 1. The stack structure proposed by the present invention increases the number of common electrolyte conduits, which originally had only one. The positive or negative electrodes of adjacent cells are not connected to the same common electrolyte conduit, increasing the resistance of the common electrolyte conduit and reducing leakage current. Furthermore, the common conduit resistance can be flexibly designed according to the number of cells in the stack to achieve the purpose of regulating leakage current.

[0020] 2. The stack structure proposed by the present invention increases the number of common electrolyte pipelines, which actually increases the effective flow cross-sectional area of ​​the common pipelines, reduces the pipeline flow resistance, increases the electrolyte flow rate, and can reduce the concentration polarization of the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The stack structure of a conventional flow battery, from left to right:

[0022] 1. Left end plate; 2. Bipolar plate; 3. Positive electrode; 4. Positive electrode frame; 5. Ion conduction membrane; 6. Negative electrode; 7. Negative electrode frame; 8. Right end plate;

[0023] Figure 2 The battery stack structure proposed by the present invention is:

[0024] Among them, 9. A left end plate having three positive electrolyte inlets, three positive electrolytes, three negative electrolyte inlets, and three negative electrolyte outlets; 10. A bipolar plate having six electrolyte through-holes corresponding to the electrolyte inlet and outlet positions on 19; 11. A positive electrode frame connected to the first positive electrolyte inlet channel and the first positive electrolyte outlet channel; 12. An ion membrane having six electrolyte through-holes corresponding to the electrolyte inlet and outlet positions on 19; 13. A negative electrode frame connected to the first negative electrolyte inlet channel and the first negative electrolyte outlet channel; 14. A positive electrode frame connected to the second positive electrolyte inlet channel and the second positive electrolyte outlet channel; 15. A negative electrode frame connected to the second negative electrolyte inlet channel and the second negative electrolyte outlet channel; 16. A positive electrode frame connected to the third positive electrolyte inlet channel and the third positive electrolyte outlet channel; 17. A negative electrode frame connected to the third negative electrolyte inlet channel and the third negative electrolyte outlet channel. DETAILED DESCRIPTION

[0025] Comparative Example:

[0026] A conventional flow battery stack structure is as follows Figure 1As shown. The stack includes a left end plate 1 and a right end plate 8, and single cells located between the two end plates, separated from left to right by bipolar plates 2. These single cells include a positive electrode 3 located within a central through-hole in a positive electrode frame 4, an ion-conducting membrane 5, and a negative electrode 6 located within a central through-hole in a negative electrode frame 7, stacked sequentially from left to right. The bipolar plate 2, positive electrode frame 4, ion-conducting membrane 5, and negative electrode frame 7 are each provided with through-holes corresponding to the positive electrolyte inlet, positive electrolyte outlet, negative electrolyte inlet, and negative electrolyte outlet 12 on the left end plate 1. The above-mentioned corresponding positive electrode electrolyte inlet through-holes are connected to form a positive electrode electrolyte inlet channel with one end closed and the other end open, and the channel is connected to the electrolyte positive electrode storage tank in the battery system; the above-mentioned corresponding positive electrode electrolyte outlet through-holes are connected to form a positive electrode electrolyte outlet channel with one end closed and the other end open, and the channel is connected to the electrolyte positive electrode storage tank in the battery system; the above-mentioned corresponding negative electrode electrolyte inlet through-holes are connected to form a negative electrode electrolyte inlet channel with one end closed and the other end open, and the channel is connected to the electrolyte negative electrode storage tank in the battery system; the above-mentioned corresponding negative electrode electrolyte outlet through-holes are connected to form a negative electrode electrolyte outlet channel with one end closed and the other end open, and the channel is connected to the electrolyte negative electrode storage tank in the battery system. The through hole on the positive electrode frame 4 serving as the positive electrolyte inlet is connected to the positive electrode 3 via a distribution pipeline; the through hole on the positive electrode frame 4 serving as the positive electrolyte outlet is connected to the positive electrode 3 via a distribution pipeline; the through hole on the negative electrode frame 7 serving as the negative electrolyte inlet is connected to the negative electrode 6 via a distribution pipeline; the through hole on the negative electrode frame 7 serving as the negative electrolyte outlet is connected to the negative electrode 6 via a distribution pipeline.

[0027] The positive electrolyte flows from the positive electrolyte inlet through-hole on the left end plate 1 of the stack into the positive electrolyte inlet channel, flows into the positive electrode 3 in the positive electrode frame 4 of each cell, reacts, and then flows out of the positive electrolyte outlet through-hole on the left end plate 1 through the positive electrolyte outlet channel. The negative electrolyte flows from the negative electrolyte inlet through-hole on the left end plate 1 of the stack into the negative electrolyte inlet channel, flows into the negative electrode 6 in the negative electrode frame 7 of each cell, reacts, and then flows out of the negative electrolyte outlet through-hole on the left end plate 1 through the negative electrolyte outlet channel.

[0028] For a battery stack with this structure, when the number of single cells reaches more than 20 and the positive electrode frame 4 and the negative electrode frame 7 are very thin, the lengths of the positive electrolyte inlet channel, the positive electrolyte outlet channel, the negative electrolyte inlet channel and the negative electrolyte outlet channel inside the battery stack will all decrease, and the corresponding resistance will decrease, and the leakage current will increase, which will reduce the coulombic efficiency of the battery stack. In this comparative example, the number of single cells in a conventional liquid flow battery stack is 60. After testing, the coulombic efficiency is 94.1%, the voltage efficiency is 83.2%, and the energy efficiency is 78.3% under a 15kW constant power charge and discharge test, and the flow rate is 3.7m 3 A low Coulomb efficiency indicates that the stack has serious leakage, and a low flow rate indicates that the stack has a large flow resistance.

[0029] Example

[0030] The present invention proposes a flow battery stack structure as follows Figure 2 The stack includes a stacked left end plate 9 and a right end plate 8, with cells separated from left to right by bipolar plates 10. The cells include a positive electrode 3 located in a through-hole in the center of the positive electrode frame, an ion-conducting membrane 12, and a negative electrode 6 located in a through-hole in the center of the negative electrode frame, stacked from left to right.

[0031] The number of cells separated by bipolar plates in the stack is 20*3=60 (M=20, N=3);

[0032] At corresponding positions on the left end plate 9 and the bipolar plate 10, there are respectively provided three through holes as the positive electrode electrolyte inlet, three through holes as the positive electrode electrolyte outlet, three through holes as the negative electrode electrolyte inlet, and three through holes as the negative electrode electrolyte outlet.

[0033] From left to right, a positive electrode electrolyte inlet at a corresponding position on the left end plate 9 and the bipolar plate 10 is connected in series in sequence, forming a total of three positive electrode electrolyte inlet channels. From the outside to the inside of the length direction of the electrode frame, there are the first positive electrolyte inlet channel, the second positive electrolyte inlet channel and the third positive electrolyte inlet channel; from left to right, a positive electrolyte outlet at the corresponding position on the left end plate 9 and the bipolar plate 10 is connected in series in sequence, forming a total of 3 positive electrolyte outlet channels. From the outside to the inside of the length direction of the electrode frame, there are the first positive electrolyte outlet channel, the second positive electrolyte outlet channel and the third positive electrolyte outlet channel; from left to right, a negative electrolyte inlet at the corresponding position on the left end plate 9 and the bipolar plate 10 is connected in series in sequence, forming a total of 3 negative electrolyte inlet channels. From the outside to the inside of the length direction of the electrode frame, there are the first negative electrolyte inlet channel, the second negative electrolyte inlet channel and the third negative electrolyte inlet channel; from left to right, a negative electrolyte outlet at the corresponding position on the left end plate 9 and the bipolar plate 10 is connected in series in sequence, forming a total of 3 negative electrolyte outlet channels. From the outside to the inside in the length direction of the electrode frame, there are the first negative electrode electrolyte outlet channel, the second negative electrode electrolyte outlet channel and the third negative electrode electrolyte outlet channel.

[0034] From left to right, the 1st cell, the 4th cell, the 7th cell┉the 58th cell, a total of 20 cells, one end of the positive electrode is connected to the first of the three positive electrode electrolyte inlet channels, and the other end is connected to the first of the three positive electrode electrolyte outlet channels; from left to right, the 1st cell, the 4th cell, the 7th cell┉the 58th cell, a total of 20 cells, one end of the negative electrode is connected to the first of the three negative electrode electrolyte inlet channels, and the other end is connected to the first of the three negative electrode electrolyte outlet channels.

[0035] From left to right, the 2nd cell, the 5th cell, the 8th cell┉the 59th cell, a total of 20 cells, one end of the positive electrode is connected to the second channel of the three positive electrode electrolyte inlet channels, and the other end is connected to the second channel of the three positive electrode electrolyte outlet channels; from left to right, the 2nd cell, the 5th cell, the 8th cell┉the 59th cell, a total of 20 cells, one end of the negative electrode is connected to the second channel of the three negative electrode electrolyte inlet channels, and the other end is connected to the second channel of the three negative electrode electrolyte outlet channels.

[0036] From left to right, the 3rd cell, the 6th cell, the 9th cell┉the 60th cell, a total of 20 cells, one end of the positive electrode is connected to the third channel of the three positive electrode electrolyte inlet channels, and the other end is connected to the third channel of the three positive electrode electrolyte outlet channels; from left to right, the 3rd cell, the 6th cell, the 9th cell┉the 60th cell, a total of 20 cells, one end of the negative electrode is connected to the third channel of the three negative electrode electrolyte inlet channels, and the other end is connected to the third channel of the three negative electrode electrolyte outlet channels.

[0037] The three positive electrode electrolyte inlet channels and the three positive electrode electrolyte outlet channels in the fuel cell stack are respectively connected to the positive electrode electrolyte storage tank outside the fuel cell stack; the three negative electrode electrolyte inlet channels and the three negative electrode electrolyte outlet channels are respectively connected to the negative electrode electrolyte storage tank outside the fuel cell stack.

[0038] The positive electrolyte is drawn from the positive electrolyte storage tank by a magnetic pump and pumped into the three positive electrolyte inlet channels of the left end plate 9, flowing into the positive electrodes in the positive electrode frames of the 20 connected single batteries to react, and then flows out of the battery stack through the three positive electrolyte outlet channels and into the positive battery storage tank.

[0039] The negative electrolyte is drawn from the negative electrolyte storage tank by a magnetic pump and pumped into the three negative electrolyte inlet channels of the left end plate 9, flowing into the negative electrodes in the negative electrode frames of the 20 connected single batteries to react, and then flows out of the battery stack through the three negative electrolyte outlet channels and into the negative battery storage tank.

[0040] The battery stack using this structure is Figure 1 Under the same material conditions of the CEC stack, the number of single battery cells is 60. After testing, the coulomb efficiency is 98.6%, the voltage efficiency is 84.7%, the energy efficiency is 83.5% under the 15kW constant power charge and discharge test, and the flow rate is 5.2m 3 / h. The significantly increased Coulombic efficiency indicates that the stack structure effectively reduces leakage current and improves stack performance. At the same stack pressure, the stack structure proposed in this invention achieves a higher flow rate, indicating a lower stack resistance, sufficient electrolyte supply, and reduced concentration polarization.

Claims

1. A flow battery stack structure, characterized in that: The stack includes two left and right end plates, and single cells located between the two end plates and separated by bipolar plates from left to right. The single cell comprises a positive electrode located in a through hole in the middle of a positive electrode frame, an ion conducting membrane, and a negative electrode located in a through hole in the middle of a negative electrode frame, which are stacked in sequence from left to right. The number of cells separated by the bipolar plates is M, where M is an integer greater than or equal to 4; N through-holes serving as positive electrode electrolyte inlets, N through-holes serving as positive electrode electrolyte outlets, N through-holes serving as negative electrode electrolyte inlets, and N through-holes serving as negative electrode electrolyte outlets are respectively provided at corresponding positions on the left end plate and the bipolar plate. The numbers of positive electrode electrolyte inlets, positive electrode electrolyte outlets, negative electrode electrolyte inlets, and negative electrode electrolyte outlets on the left end plate and the bipolar plate are the same; if M is an even number, N is 2 to M / 2; if M is an odd number, N is 2 to (M+1) / 2; From left to right, a positive electrode electrolyte inlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte inlet channels; from left to right, a positive electrode electrolyte outlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte outlet channels; from left to right, a negative electrode electrolyte inlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte inlet channels; from left to right, a negative electrode electrolyte outlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte outlet channels; From left to right, one end of the positive electrode in the 1st to Mth single cells is connected to one channel of the N positive electrolyte inlet channels, and the other end is connected to one channel of the N positive electrolyte outlet channels; and the positive electrodes of adjacent single cells are respectively connected to different channels of the N positive electrolyte inlet channels, and the positive electrodes of adjacent single cells are respectively connected to different channels of the N positive electrolyte outlet channels; and the other end of the single cell connected to a positive electrolyte inlet channel is connected to a positive electrolyte outlet channel; From left to right, one end of the negative electrode in the 1st to Mth single cells is connected to one channel of the N negative electrode electrolyte inlet channels, and the other end is connected to one channel of the N negative electrode electrolyte outlet channels; and the negative electrodes of adjacent single cells are respectively connected to different channels of the N negative electrode electrolyte inlet channels, and the negative electrodes of adjacent single cells are respectively connected to different channels of the N negative electrode electrolyte outlet channels; and the other end of the single cell connected to a negative electrode electrolyte inlet channel is connected to a negative electrode electrolyte outlet channel.

2. A flow battery stack structure, characterized in that: The stack includes two left and right end plates, and single cells located between the two end plates and separated by bipolar plates from left to right. The single cell comprises a positive electrode located in a through hole in the middle of a positive electrode frame, an ion conducting membrane, and a negative electrode located in a through hole in the middle of a negative electrode frame, which are stacked in sequence from left to right. The number of cells separated by bipolar plates is M*N; N through-holes serving as positive electrode electrolyte inlets, N through-holes serving as positive electrode electrolyte outlets, N through-holes serving as negative electrode electrolyte inlets, and N through-holes serving as negative electrode electrolyte outlets are respectively provided at corresponding positions on the left end plate and the bipolar plate. The number of positive electrode electrolyte inlets, positive electrode electrolyte outlets, negative electrode electrolyte inlets, and negative electrode electrolyte outlets on the left end plate and the bipolar plate are the same; From left to right, a positive electrode electrolyte inlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte inlet channels; from left to right, a positive electrode electrolyte outlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N positive electrode electrolyte outlet channels; from left to right, a negative electrode electrolyte inlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte inlet channels; from left to right, a negative electrode electrolyte outlet at a corresponding position on the left end plate and the bipolar plate is connected in series in sequence to form a total of N negative electrode electrolyte outlet channels; From left to right, one end of the positive electrode in the Kth cell and the N+Kth cell is connected to the Kth channel of the N positive electrode electrolyte inlet channels, and the other end is connected to the Kth channel of the N positive electrode electrolyte outlet channels; from left to right, one end of the negative electrode in the Kth cell and the N+Kth cell is connected to the Kth channel of the N negative electrode electrolyte inlet channels, and the other end is connected to the Kth channel of the N negative electrode electrolyte outlet channels; K represents an integer from 1 to N, M is an integer greater than or equal to 5; N is an integer greater than or equal to 3.

3. The stack structure according to claim 2, characterized in that: N positive electrode electrolyte inlet channels and N positive electrode electrolyte outlet channels are respectively connected to the positive electrode electrolyte storage tank outside the fuel cell stack; N negative electrode electrolyte inlet channels and N negative electrode electrolyte outlet channels are respectively connected to the negative electrode electrolyte storage tank outside the fuel cell stack.

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