CN-121994690-A - Method for predicting service life of composite graphite bipolar plate

Abstract

The invention belongs to the technical field of battery energy storage, and discloses a method for predicting the service life of a composite graphite bipolar plate, which uses the surface roughness of the graphite bipolar plate as a durability evaluation index, sets a life end index, sequentially establishes a function of the surface roughness and time of the bipolar plate in a battery actual measurement process and an offline acceleration test, and a time acceleration mapping model between the actual measurement of a bipolar plate reference sample battery and the offline acceleration test, measures the time when a roughness index value of a bipolar plate sample to be detected reaches a service life end point in the offline acceleration process, and predicts the practical service time of the sample in a galvanic pile. The method effectively solves the problem that the service life of the graphite bipolar plate cannot be predicted, overcomes the defects that the electrochemical corrosion predicted service life of different types of graphite bipolar plates is low in differentiation degree and cannot be compared with the service life of the graphite bipolar plates transversely or longitudinally, can be used as an important supporting tool for forward development and iterative upgrading of the graphite bipolar plates and long-term maintenance of the flow battery, has the characteristics of simplicity, high operability and the like, and is suitable for wide popularization.

Inventors

• WEI XUEWEN
• CHU HANLIN
• NI SHENGLAN
• WANG HAO
• SUN JIANJUN
• WANG CHANGMING
• MA ZONGREN
• WANG YUWEI
• WANG HUI
• LIU ZHEN
• FENG WEI

Assignees

• 三峡新能源吉木萨尔发电有限公司

Dates

Publication Date

20260508

Application Date

20260114

Claims (10)

1. 1. The service life prediction method of the composite graphite bipolar plate is characterized by comprising the following steps of: S1, determining an evaluation index, namely setting a life end index by taking the surface roughness of the composite graphite bipolar plate as a durability evaluation index; S2, measuring the actual measurement linear relation of a reference sample, namely measuring roughness values of the composite graphite bipolar plate under different time nodes in the actual running environment of the battery, taking the time required by the roughness of the sample to reach the end-of-life index value as the reference actual measurement end-of-life to establish a function of surface roughness (or roughness change) and time of the bipolar plate in the actual measurement process of the battery, wherein F (Sa) =f (t) or DeltaF (Sa) =f (t); S3, measuring the surface roughness value of the reference sample at different acceleration time nodes, taking the time required by the roughness of the sample to reach the end-of-life index value as the reference acceleration end-of-life ta, and establishing a function of the surface roughness (or roughness variation) and time of the bipolar plate in the offline acceleration test, wherein G (Sa) =g (t) or delta G (Sa) =g (t); S4, determining an acceleration mapping relation, namely establishing a time acceleration mapping model between the battery actual measurement of the bipolar plate reference sample and the offline acceleration test by comparing the surface roughness value (or roughness variation) of the reference sample in the battery actual measurement and the offline acceleration test; and S5, life prediction, namely determining the time ta ՛ when the roughness index value of the bipolar plate sample to be detected reaches the life end point in offline acceleration, and predicting the practical service time of the sample in a galvanic pile by utilizing a time acceleration function.
2. 2. The method for predicting the service life of a composite graphite bipolar plate according to claim 1, wherein in the step S1, the surface roughness of the bipolar plate is measured by using an optical 3D profiler.
3. 3. The method for predicting the service life of a composite graphite bipolar plate according to claim 1, wherein in the step S1, no baking intervention treatment is required to be performed on the sample before the roughness of the sample is measured.
4. 4. The method according to claim 1, wherein in the step S1, the bipolar plate life end index node is a decrease in battery voltage efficiency to 90% or less of the initial value.
5. 5. The method for predicting the service life of a composite graphite bipolar plate according to claim 1, wherein in the step S3, a constant temperature glass electrolytic tank is used as a test platform, corrosive acid electrolyte is used as a test medium, and the surface roughness values of the reference sample at different acceleration time nodes are measured under an electrochemical acceleration strategy of a three-electrode system.
6. 6. The method for predicting the service life of a composite graphite bipolar plate according to claim 5, wherein in the step S3, the temperature of the constant-temperature glass electrolytic cell is 50-60 ℃.
7. 7. The method for predicting the service life of a composite graphite bipolar plate according to claim 5, wherein in the step S3, the etching electrolyte is a mixed solution prepared from H 2 SO 4 and HCl.
8. 8. The method for predicting the service life of a composite graphite bipolar plate according to claim 7, wherein in the step S3, the concentrations of H 2 SO 4 and HCl in the etching electrolyte are C (H 2 SO 4 ) =1 to 4 mol/L, and C (HCl) =0 to 5 mol/L.
9. 9. The method for predicting the service life of a composite graphite bipolar plate according to claim 5, wherein in the step S3, the auxiliary electrode in the three-electrode system is a platinum electrode, the reference electrode is a saturated calomel electrode or a mercurous sulfate electrode, and the working electrode is a bipolar plate sample to be detected.
10. 10. The method for predicting the service life of a composite graphite bipolar plate according to claim 5, wherein in the step S3, the acceleration strategy is cyclic voltammetry curve scanning, the acceleration test condition is scanning voltage range adjustment, the scanning voltage range is +/-0.2-1 v of the actual working electrode voltage of the corresponding flow battery, and the scanning speed is 0.05-30 mV/S.

Description

Method for predicting service life of composite graphite bipolar plate Technical Field The invention relates to the technical field of battery energy storage, in particular to a method for predicting the service life of a composite graphite bipolar plate. Background The bipolar plate plays roles of supporting the frame structure, blocking electrolyte, providing a conduction path for electrons in the galvanic pile and the like in the flow battery structure. Currently, composite graphite bipolar plates are widely used in the market due to their good chemical stability, excellent workability and low cost advantages. However, the conductive carbon material exposed on the surface layer of the bipolar plate is easy to be corroded and damaged by electrochemical oxygen evolution in the long-term use process, so that the high-efficiency transfer of electrons among internal components of the battery is affected, and the operation efficiency of the battery is reduced. Meanwhile, because the self-body density of the composite graphite bipolar plate is far lower than the theoretical value of pure graphite, a large number of unfilled structural gaps exist in the composite graphite bipolar plate, and the side reaction of gassing (hydrogen, oxygen, chlorine and the like) generated in the operation process of the battery can physically damage the composite graphite bipolar plate in a gas enrichment, expansion and other modes. As such, the aging behavior of the composite graphite bipolar plate will seriously affect the operation efficiency, reliability and durability of the flow battery, and becomes a primary factor for the development and long-term use of the balanced bipolar plate. In the existing bipolar plate detection means, the corrosion potential and the corrosion current of the bipolar plate are obtained by measuring the bipolar plate electrokinetic potential polarization curve in an acidic medium, so that the initial corrosion resistance of the bipolar plate is evaluated. However, the strategy does not have time attribute, and cannot effectively reflect the long-term stability of the bipolar plate in the actual running environment of the flow battery. Meanwhile, electrochemical corrosion behavior generated in the test process belongs to intrinsic properties of graphite materials, and the performance evaluation mode cannot be used for carrying out transverse or longitudinal comparison on composite graphite bipolar plates prepared by different types of graphite raw materials and different processes, so that forward development and iterative upgrading of the composite graphite bipolar plates are seriously affected. In summary, a rapid and accurate life prediction means for the composite graphite bipolar plate is urgently needed, material and process barriers are broken, service life of the composite graphite bipolar plate is estimated, and long-term operation and maintenance arrangement of the flow battery and forward development requirements of a novel composite bipolar plate are assisted to be completed. Disclosure of Invention In the aging test process of the graphite bipolar plate, electrochemical indexes such as electrochemical corrosion potential, corrosion current and the like are intrinsic properties of the graphite, and are not changed along with the aging of the bipolar plate. In addition, the test results of the graphite bipolar plate such as hardness, thermal expansion coefficient, contact resistance and the like do not have time attribute, and have no obvious change or no regularity in the aging process. Therefore, finding a suitable graphite bipolar plate evaluation index becomes a difficulty in predicting the service life of the graphite bipolar plate, and is also a core of the invention. Aiming at the defects and shortcomings in the prior art, the invention provides a service life testing method of a composite graphite bipolar plate, which is characterized in that through introducing apparent evaluation index judgment, functional relations between evaluation indexes and time in reference sample actual measurement and offline electrochemical acceleration test are respectively established, a service life prediction mapping model of the graphite bipolar plate is established on the basis of the functional relations, and in a short time, service life predictions of composite graphite bipolar plates made of different materials and by different processes in a flow battery operation environment can be accurately, efficiently and at low cost, and technical requirements of bipolar plate iteration upgrading, battery operation maintenance and the like are effectively met. The invention adopts the following technical means to realize the aim of the invention: A method for predicting the service life of a composite graphite bipolar plate comprises the following steps: S1, determining an evaluation index, namely setting a life end index by taking the surface roughness of the composite graphite bipolar plate as a durab