A type of integrally molded graphite electrode plate for flow batteries

Abstract

This utility model relates to the technical field of bipolar plate structure for batteries, and provides an integrally molded graphite electrode plate for a flow battery, including an electrode plate body. A first flow channel is fixedly provided on one side of the electrode plate body, and a second flow channel is fixedly provided on the other side of the electrode plate body. Both the first and second flow channels include multiple sequentially connected flow channel grooves. A flow channel ridge is formed between the bottom surface of the flow channel groove and the side surface of the electrode plate body. At least two levels of draft surfaces are provided along the direction from the bottom surface of the flow channel ridge to the top surface of the flow channel ridge to ensure demolding integrity. Compared with the original electrode plate bonding structure, the electrode plate's electrical conductivity is improved.

Description

Technical Field

[0001] This utility model relates to the technical field of battery bipolar plate structure, specifically to an integrally molded graphite electrode plate for a flow battery. Background Technology

[0002] Bipolar plates, also known as current collectors, use designed and manufactured flow channels to evenly distribute fluid to the reaction layer of the electrodes for electrode reactions. The flow channels on the surface of the bipolar plate ensure uniform penetration and flow of electrolyte on the electrodes, avoiding uneven distribution of electrolyte on the electrodes, thereby improving the charge and discharge performance of the battery and the system capacity.

[0003] The inventors discovered the following problems with existing bipolar plate structures in terms of conductivity and fabrication integrity:

[0004] (1) The processing of bipolar plate flow channels generally includes milling and engraving. The cutting force of milling and engraving will produce micro-cracks, chipping or tearing on the graphite surface, destroying the crystal structure of graphite and reducing its mechanical strength, conductivity and corrosion resistance. Therefore, in order to ensure performance, bipolar plate manufacturers mainly use molding process. Molding is a plastic forming process that applies uniform pressure, which can maintain the integrity of the internal structure of graphite and make the surface smoother and denser. However, since the existing mold has a square cross section reserved for the flow channel ridge, the graphite and the mold side wall will generate huge friction after molding. In particular, the brittle material graphite may get stuck. When demolding, the core and graphite form a "mechanical lock" due to the negative angle effect. Forced demolding will cause chipping or micro-cracks at the top edge of the flow channel ridge, thereby reducing the impact on demolding integrity and reducing the strength of the plate structure.

[0005] (2) In terms of structure, existing bipolar plates use double-sided tape or dispensing method, and the flow channel is fixed on the bipolar plate manually with the help of a fixture. The double-sided tape or some sealant itself is an insulator. Even if conductive adhesive is used, its conductivity is much lower than that of metal bipolar plates or graphite-based bipolar plates. The adhesive layer exists on the contact interface between the bipolar plate and the adjacent battery cell, which will significantly increase the interface contact resistance, thereby affecting the conductivity between the plate and the flow channel. Utility Model Content

[0006] The purpose of this invention is to provide a one-piece molded graphite electrode plate for flow batteries, which can improve the technical problem of demolding integrity.

[0007] To achieve the above objectives, an integrally molded graphite electrode plate for a flow battery includes an electrode plate body. A first flow channel is fixedly provided on one side of the electrode plate body, and a second flow channel is fixedly provided on the other side of the electrode plate body. Both the first and second flow channels include multiple flow channel ridges connected in sequence. A flow channel groove is formed between the side of the flow channel ridge and the side of the electrode plate body. At least two levels of draft surfaces are provided along the direction from the bottom surface of the flow channel ridge to the top surface of the flow channel ridge.

[0008] Further configured, the draft surface includes a primary draft surface, a secondary draft surface and a tertiary draft surface, wherein the primary draft surface forms a first angle with the bottom surface of the electrode body, the secondary draft surface forms a second angle with the bottom surface of the electrode body, and the tertiary draft surface forms a third angle with the bottom surface of the electrode body.

[0009] Further configured, the first included angle is greater than the second included angle, and the second included angle is greater than the third included angle.

[0010] Further, the junction of the first-level draft surface and the bottom surface of the runner channel is provided with an inner rounded corner, and the junction of the third-level draft surface and the top surface of the runner ridge is provided with an outer rounded corner.

[0011] A further setting is that the angle of the outer fillet is greater than the angle of the inner fillet.

[0012] Further configured such that the first flow channel and the second flow channel are alternately arranged on both sides of the electrode body.

[0013] A further configuration is made such that the width of the top surface of the flow channel ridge is greater than the width of the bottom surface of the flow channel groove.

[0014] Further configured, the first flow channel is S-shaped along the length of the electrode body, and the second flow channel is S-shaped along the length of the electrode body.

[0015] Further configured, mounting holes are provided on the outer periphery of the first flow channel and at the four corners of the electrode body.

[0016] Further configured, the electrode body, the first flow channel, and the second flow channel are made of the same material.

[0017] The beneficial effects of one or more of the above technical solutions:

[0018] (1) The sidewall of the formed flow channel ridge is provided with multiple levels of draft surfaces. The first-level draft surface, the second-level draft surface and the third-level draft surface are arranged from bottom to top so that when the mold core (the part forming the flow channel ridge) is pulled out from the compacted graphite blank, the direction of friction changes from the original pure vertical direction to the inclined direction. Part of the friction force is converted into a lateral component force that is conducive to demolding, which greatly reduces the required ejection force or core pulling force. The taper formed by the third-level draft surface on the flow channel ridge creates a small demolding gap between the core and the graphite, so that the two gradually separate during the separation process, avoiding chipping or micro-cracks at the top edge and protecting the integrity of the electrode plate.

[0019] (2) In this utility model, the electrode body, the first flow channel and the second flow channel are set as an integral structure. The integral molding structure eliminates the adhesive layer. There are no other media that increase resistance between the electrode body, the first flow channel and the second flow channel. The entire electrode plate maintains uniform low resistance and improves the power transmission. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation thereof.

[0021] Figure 1 This is a schematic diagram of the structure of this utility model;

[0022] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0023] Figure 3 This is a cross-sectional view of the present invention;

[0024] Figure 4 for Figure 3 Enlarged view of section B in the middle.

[0025] In the figure, 1 is the electrode plate body; 2 is the first flow channel; 3 is the second flow channel; 4 is the flow channel ridge; 5 is the flow channel groove; 6 is the first-level draft surface; 7 is the second-level draft surface; 8 is the third-level draft surface; 9 is the inner fillet; 10 is the outer fillet; 11 is the mounting hole; and 12 is the draft surface. Detailed Implementation

[0026] The specific implementation of this embodiment will now be described with reference to the accompanying drawings.

[0027] Reference Figure 1 and Figure 2 An integrally molded graphite electrode plate for a flow battery includes an electrode plate body 1. A first flow channel 2 is fixedly disposed on one side of the electrode plate body 1, and a second flow channel 3 is fixedly disposed on the other side of the electrode plate body 1. Due to the high bonding interface resistance of existing adhesive structures, the body and flow channel are integrally molded. Specifically, the first flow channel 2 and the second flow channel 3 each include multiple flow channel ridges 4 connected in sequence. A flow channel groove 5 is formed between the side of the flow channel ridge 4 and the side of the electrode plate body 1. At least two levels of draft surfaces 12 are provided along the direction from the bottom surface of the flow channel ridge 3 to the top surface of the flow channel ridge 3.

[0028] Considering that most mainstream runners on the market are deep and narrow, if a single draft angle is to ensure the top size, the bottom will be excessively reduced; if the bottom is to be maintained, the top will be too wide. Therefore, a multi-stage draft structure with progressively increasing angles is adopted. The small angle at the top maintains the functional size, while the large angle at the bottom ensures smooth demolding. The draft surface 12 includes a first-stage draft surface 6, a second-stage draft surface 7, and a third-stage draft surface 8. Specifically, the first-stage draft surface 6 forms a first angle with the bottom surface of the electrode body 1, the second-stage draft surface 7 forms a second angle with the bottom surface of the electrode body 1, and the third-stage draft surface 8 forms a third angle with the bottom surface of the electrode body 1. The first angle is greater than the second angle, and the second angle is greater than the third angle. The large angle of the first angle at the bottom significantly reduces the resistance of deep groove demolding. The medium angle of the second angle in the middle balances the demolding force and deformation. The small angle of the first angle at the top maintains the functional size of the runner groove 5.

[0029] An inner fillet 9 is provided at the junction of the first-level draft surface 6 and the bottom surface of the runner groove 5, and an outer fillet 10 is provided at the junction of the third-level draft surface 8 and the top surface of the runner ridge 4. The inner fillet 9 reduces the stress at the root of the mold protrusion, eliminates stress concentration at the bottom of the groove, and reduces the demolding breakage rate. The outer fillet 10 further reduces the demolding friction at the top of the ridge. The double fillets make the runner cross section transition smoothly, reduce the electrolytic pressure drop, and improve the uniformity of the electrolyte flow rate.

[0030] Reference Figure 3 and Figure 4 The outer fillet 10 has a larger angle than the inner fillet 9. The large curvature of the inner fillet 9 disperses the assembly stress at the bottom of the groove and improves the bending strength. The small curvature of the outer fillet 10 maintains the contact area at the top of the ridge while reducing the contact resistance.

[0031] The first flow channel 2 and the second flow channel 3 are staggered on both sides of the electrode body 1. After the first flow channel 2 and the second flow channel 3 are staggered and stacked with other electrode bodies 1, the staggered first flow channel 2 and the second flow channel 3 form a mesh support, which improves the electrode's resistance to deformation. At the same time, the first flow channel 2 and the second flow channel 3 are spatially misaligned, resulting in a more uniform distribution of electrolyte.

[0032] When installing the bipolar plate, anvils need to be placed on both sides of the bipolar plate to ensure that the electrolyte is evenly distributed on the flow channel ridge 4. Therefore, the width of the top surface of the flow channel ridge 4 is set to be greater than the width of the bottom surface of the flow channel groove 5 to increase the contact area between the electrode and the anvil and improve the uniformity of electrolyte distribution.

[0033] The first flow channel 2 is S-shaped along the length of the electrode body 1, and the second flow channel 3 is S-shaped along the length of the electrode body 1. The S-shaped path extends the residence time of the electrolyte.

[0034] Mounting holes 11 are provided on the outer periphery of the first flow channel 2 and at the four corners of the electrode body 1. The battery electrode plates are stacked and assembled into the battery casing through the mounting holes 11. The mounting holes 11 are far away from the flow channel reaction area to avoid deformation of the flow channel due to the locking force.

[0035] The electrode body 1, the first flow channel 2, and the second flow channel 3 are made of the same material, which is a mixture of graphite and PP resin. In order to ensure the synergy of conductivity and strength, 80wt% flake graphite + 20wt% modified PP can be used to reduce resistivity and improve bending strength.

[0036] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. An integrally formed flow battery graphite pole plate, characterized by, The device includes an electrode plate body, a first flow channel is fixedly provided on one side of the electrode plate body, and a second flow channel is fixedly provided on the other side of the electrode plate body. Both the first and second flow channels include multiple flow channel ridges connected in sequence. A flow channel groove is formed between the side of the flow channel ridge and the side of the electrode plate body. At least two levels of draft surfaces are provided along the direction from the bottom surface of the flow channel ridge to the top surface of the flow channel ridge.

2. The integrally formed flow battery graphite pole plate of claim 1, wherein, The draft surfaces include a primary draft surface, a secondary draft surface, and a tertiary draft surface. The primary draft surface forms a first angle with the bottom surface of the electrode body, the secondary draft surface forms a second angle with the bottom surface of the electrode body, and the tertiary draft surface forms a third angle with the bottom surface of the electrode body.

3. The integrally formed flow battery graphite pole plate of claim 2, wherein, The first included angle is greater than the second included angle, and the second included angle is greater than the third included angle.

4. The integrally formed flow battery graphite plate of claim 1, wherein, The first-level draft surface is provided with an inner rounded corner at the junction with the bottom surface of the runner groove, and the third-level draft surface is provided with an outer rounded corner at the junction with the top surface of the runner ridge.

5. The integrally formed flow battery graphite pole plate of claim 4, wherein, The angle of the outer fillet is greater than the angle of the inner fillet.

6. The integrally formed flow battery graphite plate of claim 1, wherein, The first flow channel and the second flow channel are alternately arranged on both sides of the electrode body.

7. The integrally formed flow battery graphite plate of claim 1, wherein, The width of the top surface of the flow channel ridge is greater than the width of the bottom surface of the flow channel groove.

8. The integrally formed flow battery graphite pole plate of claim 1, wherein, The first flow channel is S-shaped along the length of the electrode body, and the second flow channel is S-shaped along the length of the electrode body.

9. The integrally formed flow battery graphite plate of claim 1, wherein, Mounting holes are provided on the outer periphery of the first flow channel and at the four corners of the electrode body.

10. The integrally formed flow battery graphite plate of claim 1, wherein, The electrode body, the first flow channel, and the second flow channel are made of the same material.

Images