TWI524585B - Electrochemical flow cell assembly and bipolar plate thereof - Google Patents

Description

Electrochemical flow battery unit assembly and bipolar plate thereof

This invention relates to an electrochemical flow cell technology, and more particularly to an electrochemical flow battery cell assembly and bipolar plates thereof.

An electrochemical flow battery, also known as a redox flow battery, is an electrochemical energy storage device, which is a storage battery that utilizes an ion number change of an oxidation-reduction reaction in an electrolyte (positive electrolyte, negative electrolyte) .

The electrochemical flow battery is generally composed of an ion exchange membrane, a fine porous positive electrode and a negative electrode on both sides of the ion exchange membrane, a positive electrode bipolar plate on the positive electrode side, and a negative electrode bipolar plate on the negative electrode side. A single cell structure is generally used to stack a plurality of cell structures into a stack in order to obtain a high voltage. Then, the positive and negative electrolytes respectively form a circulation loop through the positive and negative electrodes to discharge the electrochemical flow battery; or externally charge the battery.

At present, electrochemical flow batteries are commonly used with different valences of vanadium ion sulfuric acid aqueous solution, and the electrochemical reactions of V(IV)/V(V) and V(II)/V(III) redox couples are as follows: Positive electrode reaction: VO ²⁺ +2H ⁺ +e ^- ←→VO ²⁺ +H ₂ O

Negative reaction: V ²⁺ ←→V ³⁺ +e ^-

Full reaction formula: VO ²⁺ +2H ⁺ +V ²⁺ ←→VO ²⁺ +H ₂ O+V ³⁺

The redox electrochemical flow battery has high safety, complete charge and discharge, high energy efficiency, long battery life, less electrolyte degradation, no harmful gas emissions, and increased electrolyte storage tank to increase system storage capacity. The characteristics can be used to solve the intermittent characteristics of renewable energy, so that the uncertainty of renewable energy supply to the power grid is improved.

However, the above electrochemical flow battery often has a phenomenon that the contact resistance between the electrode and the bipolar plate is too high, the electrolyte is stagnant and the concentration is polarized, which may affect the proton and electron transmission efficiency inside the battery, and the overall efficiency of the battery is not good, so it is necessary to improve. The battery structure enhances the contact between the bipolar plate and the electrode interface and increases the distribution of the electrolyte in the flow field, and can improve the charge transfer, thereby improving the current density and energy efficiency and the storage capacity of the redox battery.

The present invention provides a bipolar plate for an electrochemical flow battery to increase the distribution of electrolyte flow in the flow field.

The invention further provides an electrochemical flow battery unit assembly, which can improve the contact between the bipolar plate and the electrode interface, thereby improving the current density and energy efficiency of the battery. And storage capacity.

The bipolar plate of the electrochemical flow battery of the present invention includes a non-conductive portion and a conductive portion. The non-conducting portion is a frame structure having a hollow region, wherein the frame structure includes a plurality of distribution channels and a plurality of manifold holes. The conductive portion is disposed in the hollow region and is in close contact with the non-conductive portion to form an accommodating space, wherein the conductive portion has a plurality of island structure to form a plurality of electrolyte flow paths in the accommodating space, and the non-conductive portion The distribution flow path can direct electrolyte flow into and out of the conductive portion.

The electrochemical flow battery cell assembly of the present invention comprises a proton exchange membrane, a pair of electrodes on either side of the proton exchange membrane, and a pair of bipolar plates on either side of the counter electrode, wherein each bipolar plate The non-conductive portion and the conductive portion are included. The non-conducting portion is a frame structure having a hollow region, wherein the frame structure includes a plurality of distribution channels and a plurality of manifold holes. The conductive portion is disposed in the hollow region and is in close contact with the non-conductive portion to form an accommodating space, and the distribution channel of the non-conductive portion can guide the electrolyte to flow into and out of the conductive portion. The conductive portion has a plurality of island structure to form a plurality of electrolyte flow paths in the accommodating space, and the electrodes are embedded in the accommodating space and are in contact with the island structure.

Based on the above, the present invention improves the interface contact between the bipolar plate and the electrode by the design of the bipolar plate, and increases the distribution of the electrolyte in the flow field, thereby effectively reducing the interface impedance, improving the fluid distribution and reducing the electrolyte flow. The flow resistance, and thereby improving the charge transfer, can increase the current density, energy efficiency, and storage capacity of the electrochemical flow battery.

In order to make the above features and advantages of the present invention more apparent, the following is a special The embodiments are described in detail below in conjunction with the drawings.

100, 500‧‧‧ bipolar plates

102, 502‧‧‧ non-conducting parts

102a‧‧‧ hollow area

103, 408‧‧‧ sealing elements

104, 504‧‧‧Electrical Department

106, 200, 506‧‧ ‧ distribution of runners

108a~d, 508a, 508b‧‧‧ manifold holes

110, 300, 302, 304, 306‧‧‧ island structure

110a‧‧‧Dome

112‧‧‧ accommodating space

114‧‧‧ Electrolyte flow path

202‧‧‧蜿蜒

400‧‧‧Electrochemical flow battery unit assembly

402‧‧‧Proton exchange membrane

404, 406‧‧‧ electrodes

H, H’, H”‧‧‧ length

l , W, W', W" ‧ ‧ width

L‧‧‧ spacing

T‧‧‧ Height

T, T', T", Te, Te'‧‧‧ thickness

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of a bipolar plate of an electrochemical flow battery in accordance with a first embodiment of the present invention.

Fig. 2A is a plan view of the bipolar plate of the first embodiment.

Figure 2B is a cross-sectional view of the B-B line segment of the bipolar plate of Figure 2A.

3A to 3D are plan views of variations of various island structures of the bipolar plate of Fig. 2B.

4A is a front elevational view of an electrochemical flow battery unit assembly in accordance with a second embodiment of the present invention.

4B is a schematic view of the electrochemical flow battery cell assembly of FIG. 4A assembled.

Fig. 5 is a perspective view of a bipolar plate in an experimental example.

Fig. 6 is a graph comparing the charge and discharge performance of the experimental example and the comparative example.

Fig. 7 is a graph comparing the energy efficiency and the storage capacity of the experimental example and the comparative example.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of a bipolar plate of an electrochemical flow battery in accordance with a first embodiment of the present invention. Fig. 2A is a plan view of the bipolar plate of the first embodiment. Figure 2B is a cross-sectional view of the B-B line segment of the bipolar plate of Figure 2A.

In the first embodiment, the bipolar plate 100 of the electrochemical flow battery includes no The conductive portion 102 and the conductive portion 104. Figure 1 shows the structure before assembly to facilitate explanation and explanation. The non-conductive portion 102 is a frame structure having a hollow region 102a having an outer length dimension of H, a width dimension W, and a thickness dimension T, the hollow region 102a having a length dimension of H", a width dimension of W", and a thickness dimension of T". The material of the non-conductive portion 102 is, for example, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene (PTFE). The polymer structure of the non-conductive portion 102 includes a plurality of distribution channels 106 and a plurality of manifold holes 108a-d. The distribution channel 106 can guide the electrolyte (not shown) to the hollow region 102a. Flowing in and out, and the manifold holes 108a-d allow electrolyte (not shown) to pass therethrough, such as when the positive electrolyte flows from the manifold hole 108a into the hollow region 102a and flows out of the manifold hole 108d. The electrolyte can move through the manifold holes 108b or 108c to the negative electrode; vice versa.

The conductive portion 104 has a plurality of island structure 110, and the conductive portion 104 has an apparent length dimension of H', a width dimension of W', and a thickness dimension of T'. The conductive portion 104 is an acid-base resistant polymer composite conductive material such as a conductive graphite plate or a composite conductive carbon plate. The dimensional relationship between the non-conductive portion 102 and the conductive portion 104 is such that the length dimension: H>H'>H", the width dimension: W>W'>W", and the thickness dimension T>T' and T>T", via two In the case of matching the non-conducting portion 102 and the conductive portion 104, the conductive portion 104 can be embedded in the hollow region 102a of the non-conductive portion 102 and adhered to the non-conductive portion 102 to form the accommodating space 112, as shown in FIG. 2A and FIG. 2B, the accommodating space 112 has a length dimension of H", a width dimension of W", and a thickness dimension of T", and a non-conductive portion 102 and the conductive portion 104 are permeable to a substance such as a sealant. The form is tightly overlapped by means of a sealing element 103, such as a member such as a gasket. In FIG. 2A, the distribution channel 200 of the non-conducting portion 102 is slightly different from that of FIG. 1, and having the crucible portion 202 can effectively increase the electrolyte distribution effect and increase the current impedance to reduce the shunt current between the respective battery cells (shunt current). Loss) However, the present invention is not limited thereto, as long as the distribution flow path 200 can guide the electrolyte to flow into and out of the conductive portion 104.

In addition, the island structure 110 of the conductive portion 104 can be disposed in the accommodating space 112. A plurality of electrolyte flow paths 114 are formed. In the present embodiment, the island structure 110 is a hexagonal protrusion and is integrally formed with the conductive portion 104. However, the present invention is not limited thereto, and the island structure 110 may be a protrusion of other shapes. .

Referring to FIG. 2B, if the planar portion of the conductive portion 104 is regarded as the electrolyte flow path 114, the height t of the island structure 110 is the size from the plane of the electrolyte flow path 114, and the pitch L of the island structure 110 is two. The distance between the tops of the two island mound structures 110. In the present embodiment, the ratio between the height t of the island structure 110 and the thickness T" of the accommodating space 112 is, for example, 0.1 to 0.5; in another embodiment, 0.15 to 0.3. The pitch of the island structure 110 is L. The ratio between the width l of the electrolyte flow path 114 is, for example, 0.2 to 0.8; in another embodiment, 0.4 to 0.6. The width l of the electrolyte flow path 114 is, for example, 0.5 mm to 2.5 mm; in another embodiment, 1 mm. Further, the top of the island structure 110 may be the dome 110a, and the radius of curvature of the dome 110a is, for example, 0.1 mm to 5 mm; in another embodiment, 0.15 mm to 1.5 mm.

In addition to the island structure 110 shown in FIG. 2A, the conductive portion 104 can also There are various modifications, and as shown in Fig. 3A, the island hill structure 300 is also hexagonal, but is arranged differently from the misalignment of Fig. 2A and belongs to the array arrangement. In addition, the conductive portion 104 in FIG. 3B has a circular island structure 302 which is arranged in a misaligned arrangement; the conductive portion 104 in FIG. 3C has a quadrangular island structure 304 which is misaligned; and the conductive portion 104 in FIG. 3D has a misaligned arrangement. A triangular island structure 306. The island hill structures in Figs. 3A to 3D each have a different shape or arrangement, but any configuration capable of improving the interface contact between the bipolar plate itself and the electrode and increasing the distribution of the electrolyte in the flow field is suitable for the present invention.

4A and 4B are schematic cross-sectional views showing the assembly of an electrochemical flow battery unit assembly in accordance with a second embodiment of the present invention, and the same reference numerals as those of the first embodiment are used to denote the same or similar members.

The electrochemical flow battery cell assembly 400 in the second embodiment includes a proton exchange membrane 402 and a pair of electrodes 404 on both sides of the proton exchange membrane 402 in addition to the pair of bipolar plates 100 of the first embodiment. 406. The electrodes 404 and 406 are, for example, porous material conductive graphite felt, conductive carbon felt or conductive carbon paper. The electrodes 404 and 406 before assembly have a thickness Te, respectively, and the thickness of the electrodes 404 and 406 after being assembled by members such as the sealing member 408 may become Te'; and when the electrodes 404 and 406 are compressed to closely contact the bipolar plate 100 When the conductive portion 104 is formed, the thickness Te' is equivalent to the thickness T" of the accommodating space 112. The non-conductive portion 102 can guide the electrolyte to smoothly and uniformly flow into and out of the conductive portion 104, and can be combined with a seal such as a gasket. The element 408 can completely seal the electrolyte inside the battery cell assembly 400 for a complete electrochemical reaction without causing electrolyte leakage or mutual electrolyte and negative electrolyte interaction. The conductive portion 104 can direct electrons into (charging) or derivate (discharge) the interior of the battery cell assembly 400, and uniformly distribute the electrolyte through the electrodes 404 and 406 for a complete electrochemical reaction procedure. It is calculated that the thickness compression ratio ((Te-Te')/Te) before and after the assembly of the electrodes 404 and 406 is, for example, 10% to 75%; in another embodiment, it may be between 20% and 40%.

The electrochemical flow battery cell assembly 400 of the second embodiment may be used alone or in combination of a plurality of components, and may be combined into a single cell or a battery stack by an additional collector member and fastening member.

The experiments are enumerated below to verify the efficacy of the present invention, but the scope of the present invention is not limited to the following experiments.

A bipolar plate 500 as shown in FIG. 5 is combined as an experimental example, in which the non-conductive portion 502 (material is polyvinyl chloride (PVC)) has a distribution flow path 506 for guiding the electrolyte to smoothly and uniformly flow into and out of the conductive portion 504, A manifold hole 508a through which the electrolyte flows and a manifold hole 508b through which the electrolyte flows. The conductive portion 504 (material is a composite carbon plate) adopts a straight-type island structure (having a height of 1 mm, a pitch of 2 mm, and a radius of curvature of the dome of 0.5 mm), so that the electrolyte is evenly distributed and flows through the electrode for completeness. The electrolyte flow path (width 1 mm) of the electrochemical reaction program also belongs to the long straight-through type.

Then, the bipolar plate group of Fig. 5 was assembled into a battery cell to perform redox battery performance verification, and compared with the battery of the flat bipolar plate (comparative example), the results of charging and discharging were compared. The results are shown in Fig. 6. The comparative example has the same configuration as the experimental example, but has no island structure at the conductive portion. As can be seen from Fig. 6, the charge and discharge performance between each cycle of the experimental example using the technique of the present invention is more stable than that of the comparative example. When the current density was 80 mA/cm ² , FIG. 7 showed that the energy efficiency of the experimental example was greatly increased by about 10% compared with the comparative example; and the storage capacity of the experimental example was about 3.5 times that of the comparative example.

In summary, the present invention adopts the design of the island hill structure in the bipolar plate, and cooperates with the non-conducting portion to guide the electrolyte to smoothly and evenly flow into and out of the distribution flow channel, so as to improve the interface contact between the bipolar plate and the electrode. It can also increase the distribution of electrolyte flow in the flow field, effectively reduce the interface impedance and improve the fluid distribution and reduce the flow resistance of the electrolyte, thereby improving the charge transfer inside the battery, and improving the current density and energy efficiency of the redox battery and storage. capacitance.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧ bipolar plates

102‧‧‧No Conductive Department

102a‧‧‧ hollow area

104‧‧‧Electrical Department

106‧‧‧Distributed runners

108a~d‧‧‧Management holes

110‧‧‧ island structure

H, H’, H”‧‧‧ length

T, T', T" ‧ ‧ thickness

W, W’, W” ‧ ‧ width

Claims (20)

A bipolar plate of an electrochemical flow battery, comprising: a non-conducting portion, being a single frame structure having a hollow region, wherein the single frame structure comprises a plurality of distribution channels and a plurality of manifold holes; and a conductive portion is disposed Forming an accommodating space in the hollow region of the single frame structure and in close contact with the non-conductive portion, wherein the conductive portion has a plurality of island structures, and the top of the island structure is a dome. A plurality of electrolyte flow paths are formed in the accommodating space, and the distribution flow path of the non-conductive portion can guide the electrolyte to flow into and out of the conductive portion. The bipolar plate of the electrochemical flow battery of claim 1, wherein the material of the non-conductive portion comprises polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyethylene (PE), Polypropylene (PP), polystyrene (PS) or polytetrafluoroethylene (PTFE). The bipolar plate of an electrochemical flow battery according to claim 1, wherein the conductive portion comprises a conductive graphite plate or a composite conductive carbon plate. The bipolar plate of the electrochemical flow battery of claim 1, wherein the non-conductive portion and the conductive portion are closely overlapped by a sealing member or a glue. The bipolar plate of an electrochemical flow battery according to claim 1, wherein the island hill structure comprises a polygonal, circular or straight strip structure. The bipolar plate of the electrochemical flow battery according to claim 1, Wherein the ratio of the height of the island hill structure to the thickness of the accommodating space is 0.1 to 0.5. The bipolar plate of an electrochemical flow battery according to claim 1, wherein a ratio between a pitch of the island hill structure and a width of the electrolyte flow path is 0.2 to 0.8. The bipolar plate of an electrochemical flow battery according to claim 1, wherein the electrolyte flow path has a width of 0.5 mm to 2.5 mm. The bipolar plate of an electrochemical flow battery according to claim 1, wherein the dome has a radius of curvature of 0.1 mm to 5 mm. An electrochemical flow battery cell assembly comprising a proton exchange membrane, a pair of electrodes on either side of the proton exchange membrane, and a pair of bipolar plates on either side of the counter electrode, wherein each of the bipolar plates The method includes: a non-conducting portion, which is a single frame structure having a hollow region, wherein the single frame structure includes a plurality of distribution flow channels and a plurality of manifold holes; and a conductive portion disposed in the hollow of the single frame structure a region is closely adhered to the non-conductive portion to form an accommodating space, and the conductive portion has a plurality of island structures, and the top of the island structure is a dome to form a majority in the accommodating space Electrolyte flow path, wherein the distribution flow channel of the non-conducting portion can guide electrolyte into and out of the conductive portion, and the electrode is embedded in the accommodating space and is opposite to the conductive portion The island hill structure is in contact. The electrochemical flow battery cell assembly of claim 10, wherein the electrode comprises a porous material conductive graphite felt, a conductive carbon felt or a conductive carbon paper. The electrochemical flow battery cell assembly of claim 10, wherein the electrode has a thickness compression ratio of 10% to 75% before and after assembly. The electrochemical flow battery cell assembly of claim 10, wherein the material of the non-conductive portion comprises polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyethylene (PE), polypropylene. (PP), polystyrene (PS) or polytetrafluoroethylene (PTFE). The electrochemical flow battery cell assembly of claim 10, wherein the conductive portion comprises a conductive graphite plate or a composite conductive carbon plate. The electrochemical flow battery unit assembly according to claim 10, wherein the non-conductive portion and the conductive portion are closely overlapped by a sealing member or a glue. The electrochemical flow battery cell assembly of claim 10, wherein the island hill structure comprises a polygonal, circular or straight strip structure. The electrochemical flow battery cell assembly of claim 10, wherein a ratio of a height of the island hill structure to a thickness of the accommodating space is 0.1 to 0.5. The electrochemical flow battery cell assembly of claim 10, wherein a ratio between a pitch of the island hill structure and a width of the electrolyte flow path is 0.2 to 0.8. The electrochemical flow battery cell assembly of claim 10, wherein the electrolyte flow path has a width of from 0.5 mm to 2.5 mm. The electrochemical flow battery cell assembly of claim 10, wherein the dome has a radius of curvature of from 0.1 mm to 5 mm.