Method for reducing surface microdefects of titanium metal bipolar plate of fuel cell

Abstract

A method for reducing surface microdefects of a titanium metal bipolar plate of a fuel cell comprises the following steps: firstly, carrying out ultrasonic oil removal on the titanium metal bipolar plate, then adding an H2SO4 solution with the concentration of 30-60g / L, an HF solution with the concentration of 2-10g / L and methanol with the concentration of 20-40g / L into distilled water, uniformly stirring and mixing to prepare a polishing solution, and then carrying out electrochemical polishing on the titanium metal bipolar plate to obtain the surface microdefects of the titanium metal bipolar plate. The purpose of micro-leveling the surface of the titanium metal bipolar plate gradually is achieved, micro-defects on the surface of the titanium metal bipolar plate can be reduced, such as micro-cracks generated in the rolling process or defects of a conductive corrosion-resistant carbon coating on the surface of the bipolar plate, the service life of the bipolar plate coating is remarkably prolonged, and the reliability of the bipolar plate coating is remarkably improved. A specially-made polishing solution is used during electrochemical polishing, the polishing solution is simple in component, stable in performance and good in effect, the polishing process is reasonably set, and the method is suitable for large-scale production and application.

Description

technical field [0001] The invention relates to the field of fuel cell titanium metal bipolar plates, in particular to a method for reducing microscopic defects on the surface of fuel cell titanium metal bipolar plates. Background technique [0002] Proton exchange membrane fuel cell (PEMFC) is a device that directly converts the chemical energy in hydrogen fuel and oxidant into electrical energy through electrode reaction. The product is only water, which has high energy conversion efficiency, no pollution, quick start, and long life. and high power density. As one of the key components of the proton exchange membrane fuel cell, the bipolar plate accounts for 40-50% of the total cost of the entire stack and 70-80% of the total mass. It plays the role of collecting and conducting current, separating The role of oxidant and fuel gas, conducting transport gas, heat transfer and supporting the entire stack skeleton. [0003] Bipolar plates need to have good electrical and ther...

AI Technical Summary

Problems solved by technology

As a traditional bipolar plate, graphite bipolar plate has good electrical conductivity and corrosion resistance, but graphite itself has a large porosity, which makes it unable to block reaction gas well, and it is easy to cause water penetration; poor mechanical properties, High brittleness, which brings great difficulty to its processing, and cannot withstand the vibration of the car when it is used in the car

Metal bipolar plates (titanium, stainless steel, etc.) have good mechanical properties and electrical conductivity, but it is easy to form a passivation film when in contact with the electrolyte solution in the service environment (pH = 2 ~ 3, T = 65 ° C ~ 90 ° C) , so that the contact resistance between the bipolar plate and the diffusion layer increases, resulting in a decrease in the output power and service life of the fuel cell; and the metal bipolar plate will undergo localized corrosion and dissolution in the electrolyte solution, and the dissolution of metal ions will pollute the membrane electrode. Poison the catalyst and greatly reduce battery life, so ordinary metal bipolar plates cannot directly meet the service requirements of PEMFC

Compared with stainless steel, titanium metal has better corrosion resistance, and titanium metal bipolar plate has longer service life and better reliability; but the elongation of titanium metal is only 25% to 30%, which is much lower than that of stainless steel ( The elongation rate is more than 40%), so it is inevitable that there are many microscopic defects on the surface of the titanium bipolar plate during the rolling and stamping process. These defects have an important impact on the preparation process of the bipolar plate coating, so it must be minimized or eliminate these microscopic defects