A method for detecting uniformity of current collecting plate and battery stack packaging force

Abstract

The present invention provides a current collector plate with partitioned piezoelectric ceramics. The surface of the current collector plate is divided into several zones. The lead zirconate titanate (PZT) piezoelectric ceramics are prepared by high-temperature sintering, and the oxidation-resistant layer, which also serves as the piezoelectric ceramic's upper electrode, is formed by nickel plating. The present invention also provides a method for detecting the uniformity of force applied to a battery stack package. The method comprises a current collector plate with partitioned piezoelectric ceramics. The upper and lower electrodes of the piezoelectric ceramics are combined with a multi-channel oscilloscope and a computer to form a detection circuit. By calculating the cumulative voltage of each zone during assembly and comparing the force uniformity of different zones, this method can quantify and online detect the force applied to the edges of different zones during battery stack packaging. The current collector plate of the present invention is easy to manufacture, and the PZT piezoelectric ceramics are not easily detached. When combined with a multi-channel oscilloscope and a computer to form a detection circuit, it can quantitatively analyze the force applied to different zones in the battery stack package, effectively detecting potential stress concentration in the stack and reducing the risk of stack leakage and failure.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell production and processing, and more specifically to a method for detecting the uniformity of a current collecting plate and a fuel cell stack packaging force. Background Art

[0002] A fuel cell is a power generation device that generates electricity through an electrochemical reaction between hydrogen and oxygen (from the air). Proton exchange membrane fuel cells are considered a promising new energy technology due to their high conversion efficiency, zero pollution, and strong environmental adaptability.

[0003] The fuel cell stack is the core of the fuel cell system, primarily consisting of a membrane electrode, bipolar plates, current collectors, insulators, end plates, seals, and fasteners. A typical stack structure, from top to bottom, consists of an upper end plate, an upper insulator, and an upper current collector. In the middle is a repeating unit of membrane electrode and bipolar plates, followed by a symmetrical lower current collector, lower insulator, and lower end plate. Screws or bolts are also used for fastening.

[0004] Stack packaging involves applying a longitudinal force to the stack's upper end plate using a stack packaging machine, sealing the components together with sealing rings. This prevents leakage of reactant gases or coolant and reduces interfacial contact resistance. Uneven stack packaging force can easily cause seal misalignment or stress concentration, leading to hydrogen, oxygen, or coolant leaks, potentially creating safety hazards and stack failure.

[0005] The commonly used method for checking the stress condition of the fuel cell stack is to use a pressure sensor to detect the stress condition of the fuel cell stack. For example, the utility model with the authorization announcement number CN 215220781U discloses a fuel cell packaging pressure test device, including an upper end plate and a lower end plate arranged in parallel, a fastening assembly for connecting the upper end plate and the lower end plate, a fuel cell unit accommodating portion between the upper end plate and the lower end plate, and multiple pressure sensors evenly arranged below the upper end plate. The utility model sets a pressure sensor between the upper end plate and the lower end plate. Although it can detect the pressure at different positions when the fuel cell is packaged and analyze the uniformity of the stress on the fuel cell stack. However, the pressure sensor of the device is an external component, and the number of components increases accordingly with the increase in partitions, and the arrangement is relatively cumbersome; and as the fuel cell stack is loaded onto a vehicle, the vibration on the vehicle can easily cause the pressure sensor to fall off, posing a safety hazard. In addition, the pressure sensor cannot be removed from the packaged fuel cell stack and cannot be reused, resulting in a waste of resources. Summary of the Invention

[0006] The present invention provides a method for detecting the uniformity of the packaging force of a battery stack, so as to solve the problems of the existing use of pressure sensors to detect the force condition of the battery stack, such as the pressure sensors are complicated to arrange, easy to fall off, and cannot be removed from the packaged battery stack and cannot be reused.

[0007] The present invention adopts the following technical solutions:

[0008] A current collecting plate includes a current collecting plate substrate, the surface of which is divided into several unconnected areas, each of which is uniformly coated with PZT raw material and formed into PZT piezoelectric ceramics through high-temperature sintering. The surface of the PZT piezoelectric ceramics is also provided with a nickel-plated layer to form an upper electrode, and the current collecting plate substrate serves as a lower electrode.

[0009] Furthermore, the bottom surface of the current collecting plate, each side surface of the current collecting plate, and the gap surfaces of each area on the surface of the current collecting plate are also provided with a nickel plating layer.

[0010] Preferably, the thickness of the PZT piezoelectric ceramic is controlled to be 100-1000 μm.

[0011] In a preferred embodiment, the edges of the PZT piezoelectric ceramic are rounded.

[0012] The present invention also provides a method for detecting the uniformity of the stack packaging force. Based on the above-mentioned current collecting plate, the specific method includes:

[0013] 1. Preparation of partitioned piezoelectric ceramic current collector plates

[0014] S101, separating one side surface of the current collecting plate substrate into several unconnected areas by using adhesive strips, and then evenly coating each area with the prepared mixed PZT raw material, with a thickness controlled to be 100-1000 μm;

[0015] S102, tearing off the rubber strip in step S101, and then placing the current collecting plate in a high-temperature furnace for sintering to form a PZT piezoelectric ceramic;

[0016] S103, nickel-plating the current collecting plate obtained in step S102. Except for the side walls of each PZT piezoelectric ceramic, the rest of the current collecting plate surface is nickel-plated to enhance the oxidation resistance of the current collecting plate and to add an upper electrode to the PZT piezoelectric ceramic. The current collecting plate substrate serves as the lower electrode.

[0017] 2. Stack packaging and force uniformity testing

[0018] S201. Assemble the stack on a stack press in the order of the lower end plate, lower insulating plate, lower current collecting plate, bipolar plate, and membrane electrode repeating unit. The surface of the topmost monopolar plate that directly contacts the upper current collecting plate is a plane. Place several different electrode wires at the edge of this plane, corresponding to the respective areas on the upper surface of the current collecting plate prepared in step 1, and record them as negative electrodes. Then, place the partitioned piezoelectric ceramic current collecting plate prepared in step 1 as the upper current collecting plate, and place several wires on the upper electrode surface of the upper current collecting plate for lead-out, which are recorded as positive electrodes. Finally, place the upper insulating plate and upper end plate, and insert the screw to manually pre-tighten.

[0019] S202. Connect the wires drawn out in step S201 to a multi-channel oscilloscope, and connect the multi-channel oscilloscope to a computer to automatically record and calculate data. First, clear the voltage change in each area and record the initial state of the voltage in each area. Then, the packaging machine slowly applies pressure to the stack until the preload force reaches the design value. The force in each area will not be completely uniform. Due to the piezoelectric effect, the PZT deformation is proportional to the cumulative voltage. By calculating and comparing the cumulative voltage, the force conditions in different areas can be quantitatively determined.

[0020] S203: After the test is completed, the external wires are removed to complete the overall packaging.

[0021] Furthermore, the preparation of the partitioned piezoelectric ceramic current collecting plate further includes step S104: polarizing the current collecting plate after the nickel plating treatment in step S103 to enhance the piezoelectric effect.

[0022] In a preferred embodiment, when coating each region with the PZT raw material in the above step S101, the edges of each region are coated into rounded corners.

[0023] In a preferred embodiment, during the high-temperature sintering in step S102 , the temperature is uniformly increased to above 1200° C. and maintained for at least 30 minutes.

[0024] In a preferred embodiment, when the current collecting plate is nickel plated in step S103, a rubber strip is used to cover the sidewalls of the piezoelectric ceramic to avoid deposition of an upper nickel plated layer and direct conduction between the upper and lower electrodes.

[0025] In a preferred embodiment, if the PZT deformation variable of a certain area is different from that of an adjacent area or a design value, pressure compensation needs to be considered in that area; if the deformation variable of a certain area is different from that of an adjacent area or a design value by more than a threshold, repackaging should be considered.

[0026] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0027] 1. The surface of the current collector plate of the present invention is divided into several discrete regions, each of which is coated with PZT raw material and sintered at high temperature to form a PZT piezoelectric ceramic. The PZT piezoelectric ceramic is then nickel-plated to form an oxidation-resistant layer, which serves as the upper electrode of the PZT piezoelectric ceramic. The current collector plate substrate serves as the lower electrode. This current collector plate with a PZT piezoelectric ceramic structure is easy to manufacture and the PZT piezoelectric ceramic is not easily detached. Combined with a multi-channel oscilloscope and a computer to construct a detection circuit, it quantitatively analyzes the stress conditions in different regions of the stack, effectively detecting stress concentration that may occur in the stack package and reducing the risk of stack leakage and failure.

[0028] 2. The detection method of the present invention cleverly converts the packaging force into a voltage value based on the piezoelectric effect. By calculating the cumulative voltage value in different areas and then simply comparing them, the force uniformity in different areas can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a front view of the current collecting plate of the present invention.

[0030] Figure 2 for Figure 1 Cross-sectional view in the AA direction. DETAILED DESCRIPTION

[0031] The following describes specific embodiments of the present invention with reference to the accompanying drawings. Numerous details are provided below to provide a comprehensive understanding of the present invention, but those skilled in the art will appreciate that the present invention can be practiced without these details. Well-known components, methods, and processes are not described in detail below.

[0032] Example 1

[0033] A collector plate, referring to Figure 1 , comprising a current collecting plate base 10, the surface of which is divided into a plurality of unconnected regions 11. The number of regions can be determined according to actual needs. This embodiment specifically illustrates six regions, but the present invention is not limited to six regions. More regions can be used to achieve more precise pressure differentiation.

[0034] Reference Figure 1 and Figure 2 Each area is evenly coated with PZT raw material and sintered at high temperature to form a PZT piezoelectric ceramic 21. The thickness of the PZT piezoelectric ceramic 21 is controlled to be 100-1000 μm. The edges of the PZT piezoelectric ceramic 21 are rounded instead of right-angled.

[0035] Reference Figure 2The surface of the PZT piezoelectric ceramic 21 is also coated with a nickel layer 22, forming the upper electrode. The current collector substrate serves as the lower electrode. To enhance the current collector's oxidation resistance, the current collector shown in this embodiment is also nickel-plated on its bottom surface, side surfaces, and the gaps between various areas on its upper surface. This means that except for the sidewalls of the PZT piezoelectric ceramic 21, the rest of the current collector surface is nickel-plated.

[0036] Example 2

[0037] This embodiment provides a method for detecting the uniformity of packaging force of a battery stack. The method is based on the above-mentioned current collecting plate and includes:

[0038] 1. Preparation of partitioned piezoelectric ceramic current collector plates

[0039] S101. Separate the surface of one side of the collector plate substrate into 6 unconnected areas by using adhesive strips, and then evenly coat the mixed prepared PZT raw material in each area with a thickness of 100-1000 μm. It is best to coat the edges of each area into rounded corners to avoid using right angles.

[0040] S102, tear off the rubber strip in step S101, and then place the current collecting plate in a high-temperature furnace for sintering to form PZT piezoelectric ceramics. During sintering, the temperature should be evenly increased to above 1200° C. and maintained for at least 30 minutes.

[0041] S103: Nickel-plating the current collector plate from step S102. Except for the sidewalls of each PZT piezoelectric ceramic, the remaining surface of the current collector plate is nickel-plated. This not only enhances the oxidation resistance of the current collector plate, but also adds an upper electrode to the PZT piezoelectric ceramic. The lower electrode is the current collector plate itself. It is important to note that the PZT does not need to be plated with an electrode at this point. Instead, a rubber strip should be used to cover it to prevent the deposition of a nickel coating, allowing direct electrical connection between the upper and lower electrodes.

[0042] S104 , polarizing the current collecting plate after the nickel plating treatment in step S103 to enhance the piezoelectric effect, thereby completing the production of the current collecting plate with partitioned PZT piezoelectric ceramics.

[0043] 2. Stack packaging and force uniformity testing

[0044] S201. Assemble the battery stack on the battery stack press in sequence according to the lower end plate, lower insulating plate, lower current collecting plate, bipolar plate and membrane electrode repeating unit. The surface of the top monopolar plate that is in direct contact with the upper current collecting plate is a plane. Six different electrode wires are placed on the edge of the plane, corresponding to the various areas on the upper surface of the current collecting plate prepared in step 1, which are recorded as negative electrodes; then place the partitioned piezoelectric ceramic current collecting plate prepared in step 1 as the upper current collecting plate, and place six wires on the upper electrode surface of the upper current collecting plate, which are recorded as positive electrodes; finally, place the upper insulating plate and the upper end plate, and insert the screw to pre-tighten manually.

[0045] S202. Connect the wires drawn out in step S201 to a multi-channel oscilloscope, and connect the multi-channel oscilloscope to a computer to realize automatic data recording and calculation. Due to the gravity of the upper end plate and the upper insulating plate, the six electrode sheets may produce voltage changes at this time. Therefore, the voltage changes in each area are first reset to zero, and the initial state of the voltage in each area is recorded as Va0, Vb0, Vc0, Vd0, Ve0, and Vf0. Then, the packaging machine slowly applies pressure to the stack until the end of the preload design value. The force on the six areas will not be completely uniform. Due to the piezoelectric effect, the PZT deformation is proportional to the cumulative voltage. By calculating and comparing the cumulative voltage and 、 、 、 、 、 , we can quantitatively know the stress conditions in different areas.

[0046] S203: After the test is completed, the external wires are removed to complete the overall packaging.

[0047] If the PZT deformation in a certain area is different from that in the adjacent area or the design value, pressure compensation should be considered in that area; if the deformation in a certain area is different from that in the adjacent area or the design value by more than a threshold, repackaging should be considered.

[0048] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A current collecting plate, comprising a current collecting plate substrate, characterized in that: The surface of the collector plate substrate is divided into several unconnected areas, each area is evenly coated with PZT raw material and formed into PZT piezoelectric ceramics through high-temperature sintering. The surface of the PZT piezoelectric ceramics is also provided with a nickel plating layer to form an upper electrode, and the collector plate substrate is the lower electrode.

2. A current collecting plate according to claim 1, characterized in that: The bottom surface of the current collecting plate, each side surface of the current collecting plate and the gap surface of each area of ​​the surface of the current collecting plate are also provided with a nickel plating layer.

3. The current collecting plate according to claim 1, wherein: The thickness of the PZT piezoelectric ceramic is controlled to be 100-1000 μm.

4. The current collecting plate according to claim 1, wherein: The edges of the PZT piezoelectric ceramics are rounded.

5. A method for detecting the uniformity of stack packaging force, based on the current collecting plate according to claim 1, characterized in that: Specific methods include:

1. Preparation of partitioned piezoelectric ceramic current collector plates S101, separating one side surface of the current collecting plate substrate into several unconnected areas by using adhesive strips, and then evenly coating each area with the prepared mixed PZT raw material, with a thickness controlled to be 100-1000 μm; S102, tearing off the rubber strip in step S101, and then placing the current collecting plate in a high-temperature furnace for sintering to form a PZT piezoelectric ceramic; S103, nickel-plating the current collecting plate obtained in step S102. Except for the side walls of each PZT piezoelectric ceramic, the rest of the current collecting plate surface is nickel-plated to enhance the oxidation resistance of the current collecting plate and to add an upper electrode to the PZT piezoelectric ceramic. The current collecting plate substrate serves as the lower electrode.

2. Stack packaging and force uniformity testing S201. Assemble the stack on a stack press in the order of the lower end plate, lower insulating plate, lower current collecting plate, bipolar plate, and membrane electrode repeating unit. The surface of the topmost monopolar plate that directly contacts the upper current collecting plate is a plane. Place several different electrode wires at the edge of this plane, corresponding to the respective areas on the upper surface of the current collecting plate prepared in step 1, and record them as negative electrodes. Then, place the partitioned piezoelectric ceramic current collecting plate prepared in step 1 as the upper current collecting plate, and place several wires on the upper electrode surface of the upper current collecting plate for lead-out, which are recorded as positive electrodes. Finally, place the upper insulating plate and upper end plate, and insert the screw to manually pre-tighten. S202. Connect the wires drawn out in step S201 to a multi-channel oscilloscope, and connect the multi-channel oscilloscope to a computer to automatically record and calculate data. First, clear the voltage change in each area and record the initial state of the voltage in each area. Then, the packaging machine slowly applies pressure to the stack until the preload force reaches the design value. The force in each area will not be completely uniform. Due to the piezoelectric effect, the PZT deformation is proportional to the cumulative voltage. By calculating and comparing the cumulative voltage, the force conditions in different areas can be quantitatively determined. S203: After the test is completed, the external wires are removed to complete the overall packaging.

6. The method for detecting uniformity of stack packaging force according to claim 5, characterized in that: The preparation of the partitioned piezoelectric ceramic current collecting plate further includes step S104: polarizing the current collecting plate after the nickel plating treatment in step S103 to enhance the piezoelectric effect.

7. The method for detecting uniformity of stack packaging force according to claim 5, characterized in that: When the PZT raw material is coated on each region in step S101, the edge of each region is coated into a rounded corner.

8. The method for detecting uniformity of stack packaging force according to claim 5, wherein: During the high-temperature sintering in step S102 , the temperature is uniformly increased to above 1200° C. and maintained for at least 30 minutes.

9. The method for detecting uniformity of stack packaging force according to claim 5, wherein: When the current collecting plate is nickel plated in step S103, the side walls of the piezoelectric ceramic are covered with adhesive strips to avoid deposition of an upper nickel plated layer and direct conduction between the upper and lower electrodes.

10. The method for detecting uniformity of packaging force of a battery stack according to claim 5, wherein: If the PZT deformation in a certain area is different from that in the adjacent area or the design value, pressure compensation is performed in that area; if the deformation in a certain area is different from that in the adjacent area or the design value by more than a threshold, repackaging is performed.

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