Bipolar plates made of plain weave carbon/epoxy composite for proton exchange membrane fuel cell

Kim, M.,Yu, H.N.,Lim, J.W.,Lee, D.G. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.5

Polymer electrolyte membrane fuel cell or proton exchange membrane fuel cell (PEMFC) is composed of bipolar plates, end plates, membrane electrode assemblies (MEAs) and gas diffusion layers (GDLs). Among the constituents of PEMFCs, the bipolar plate is a key component that collects and conducts the current from cell to cell. The electrical resistance of the bipolar plate, which consists of the bulk material resistance and interfacial contact resistance between the GDLs and the bipolar plates, should be reduced to improve the performance of the fuel cell. In the present study, a bipolar plate made of plain weave carbon fiber epoxy composite is developed to increase the manufacturing productivity of the fuel cell and to decrease the bulk electric resistance. A graphite coating method is performed on the bipolar plate to reduce the interfacial contact resistance between the GDLs and the bipolar plates and to limit the transport of gases through the bipolar plates. The experimental results show that the bulk resistance of the plain weave carbon composite bipolar plate is about 50% less than that of a carbon composite bipolar plate made of unidirectional carbon fiber epoxy composites with the same thickness. Moreover, a 2μm graphite coating on the bipolar plate effectively prevent gas transport through the bipolar plate.

2SK-8 Role of Conductive Fillers on Properties of Polypropylene Composites for PEMFC Bipolar plates

( Rungsima Yeetsorn ),( Michael W. Fowler ),( Costas Tzoganakis ),( Chaiwat Prapainainar ),( Walaiporn Prissanaroon Ouajai ) 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

Due to increasing environmental concerns and escalating oil prices, increasing attention is being paid to fuel cell technologies. One of the current barriers to their commercialization is the cost of the components and manufacturing, specifically bipolar plates. Conductive thermoplastic composites are thought to be one of the most promising candidate materials to substitute for metallic and graphite materials in bipolar plates for low temperature fuel cells, such as Proton Exchange Membrane Fuel Cell (PEMFC) or Direct Methanol Fuel Cell (DMFC). Bipolar plates made from thermoplastic carbon composites are light in weight and can be shaped in mold. Research work on bipolar plate materials will bring about the next significant improvement in fuel cell performance by lowering the size, weight and cost of stacks. Our research group focuses on using polypropylene/conductive filler composites with low filler loading as materials for bipolar plate production. The selected conductive fillers used in our work are graphite, carbon fiber, carbon black, and graphene. These composites have a major advantage in that they can be produced by a conventional low-cost injection or compression molding techniques. However, it is difficult to meet desirable conductivity when using the composite plates while maintaining processability. Surface, contact, and volume resistance occurring in fuel cells causes low efficiency fuel cells containing the composite bipolar plates compared to fuel cells containing metallic or graphite bipolar plates. In this regard, several approaches, such as introducing small amounts of polypyrrole to the composites, coating polypyrrole via chemical polymerization or coating copper via electroless deposition on a bipolar plate surface, and inserting metal sheet into the composite plates, were created for reducing the resistance.

Preparation and properties on the graphite/polypropylene composite bipolar plates with a 304 stainless steel by compression molding for PEM fuel cell

Lee, Yang-Bok,Lee, Choong-Hyun,Kim, Kyung-Min,Lim, Dae-Soon Elsevier 2011 International journal of hydrogen energy Vol.36 No.13

<P><B>Abstract</B></P><P>Graphite/polymer composites have high corrosion resistance, low contact resistance and low fabrication cost but low cell efficiency and mechanical strength. This study examined the electrical and mechanical properties of graphite/polypropylene composite bipolar plates. Carbon nanotubes (CNTs) were used to improve the electrical properties of the graphite/PP composites. Although the electrical properties increased when excess conducting filler was added to the composite, the mechanical strength decreased significantly. 304 stainless steel (304 SS) plates with different thicknesses were used as the support material of a graphite/PP composite bipolar plate. The 304 SS-supported graphite/PP composite bipolar plate had an optimum CNTs/graphite/PP composite composition of 1.2, 83 and 17 wt.%, respectively. The flexural strength of the 304 SS-supported graphite/PP composites increased from 35 to 58 MPa with increasing 304 SS thickness from 0.5 to 1 mm. The power density of the graphite bipolar plate and 304 SS-supported graphite/PP composite bipolar plate were 968 and 877 mW cm<SUP>−2</SUP>, respectively. The 304 SS complemented the mechanical strength of the graphite/PP composite bipolar plate as well as the cell efficiency.</P> <P><B>Highlights</B></P><P>► The 304 SS-supported graphite/PP composite bipolar plate was fabricated by conventional compression molding method. ► 304 SS plates with different thicknesses were used as the support material of a graphite/PP composite bipolar plate. ► The electrical, mechanical and corrosional properties and single cell performance were evaluated. ► The 304 SS improved the mechanical strength of the graphite/PP composite bipolar plate as well as the cell efficiency.</P>

Development of Carbon Composite Bipolar Plates for Vanadium Redox Flow Batteries

Lee, Nam Jin,Lee, Seung-Wook,Kim, Ki Jae,Kim, Jae-Hun,Park, Min-Sik,Jeong, Goojin,Kim, Young-Jun,Byun, Dongjin Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.11

Carbon composite bipolar plates with various carbon black contents were prepared by a compression molding method. The electrical conductivity and electrochemical stability of the bipolar plates have been evaluated. It is found that the electrical conductivity increases with increasing carbon black contents up to 15 wt %. When the carbon black contents are greater than 15 wt %, the electrical conductivity decreases because of a poor compatibility between epoxy resin and carbon black, and a weakening of compaction in the carbon composite bipolar plate. Based on the results, it could be concluded that there are optimum carbon black contents when preparing the carbon composite bipolar plate. Corrosion tests show that the carbon composite bipolar plate with 15 wt % carbon black exhibits better electrochemical stability than a graphite bipolar plate under a highly acidic condition. When the optimized carbon composite bipolar plate is applied to vanadium redox flow cells, the performance of flow cells with the carbon composite bipolar plate is comparable to that of flow cells with the graphite bipolar plate.

Development of Carbon Composite Bipolar Plates for Vanadium Redox Flow Batteries

Nam Jin Lee,Seung-Wook Lee,Ki Jae Kim,김재헌,Min-Sik Park,Goojin Jeong,김영준,변동진 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.11

Carbon composite bipolar plates with various carbon black contents were prepared by a compression molding method. The electrical conductivity and electrochemical stability of the bipolar plates have been evaluated. It is found that the electrical conductivity increases with increasing carbon black contents up to 15 wt %. When the carbon black contents are greater than 15 wt %, the electrical conductivity decreases because of a poor compatibility between epoxy resin and carbon black, and a weakening of compaction in the carbon composite bipolar plate. Based on the results, it could be concluded that there are optimum carbon black contents when preparing the carbon composite bipolar plate. Corrosion tests show that the carbon composite bipolar plate with 15 wt % carbon black exhibits better electrochemical stability than a graphite bipolar plate under a highly acidic condition. When the optimized carbon composite bipolar plate is applied to vanadium redox flow cells, the performance of flow cells with the carbon composite bipolar plate is comparable to that of flow cells with the graphite bipolar plate.

고분자연료전지용 분리판 상용화 기술개발

김정헌 한국수소및신에너지학회 2011 한국수소 및 신에너지학회논문집 Vol.22 No.3

To promote the industry of PEMFC, the commercialization of its parts especially bipolar plate is needed. The bipolar plate is one of key parts for PEMFC, which occupies cost portion of 5~8% in the system. To replace the bipolar plate of machined graphite highly costly, the stamped thin matal or the molded carbon composite has been developed. According to the merits and demerits of each material and its forming process,the stamped metallic plate has been considered to the bipolar plate of PEMFC for automotive, and on the other hand, the molded composite plate has been considered to one for building applications. Hankook Tire Co., Ltd. has developed the carbon composite material and the manufacturing process for the bipolar plates. The developed bipolar plates were proved to be fully applicable to PEMFC of building applications in characteristics and performance, and so government strategic project to develop the mass-production technology for bipolar plates was started and is being conducted by the company. Through the government project for obtaining both the commercialization technology and production capacity for the bipolar plates, the price and the performance of domestic PEMFCs are expected to become competitive in international market.

Method for exposing carbon fibers on composite bipolar plates

Lee, Dongyoung,Lim, Jun Woo,Nam, Soohyun,Choi, Ilbeom,Lee, Dai Gil Elsevier 2015 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.134 No.-

<P><B>Abstract</B></P> <P>The carbon/epoxy composite bipolar plate is an ideal substitute for the brittle graphite bipolar plate for proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs) because of its high mechanical properties and easy manufacturing. However, due to the resin-rich area that forms on its surface, the carbon/epoxy composite bipolar plate requires an expanded graphite coating to decrease the areal specific resistance (ASR). The expanded graphite coating not only increases the manufacturing costs but also has very low mechanical properties.</P> <P>In this work, an innovative manufacturing method that exposes carbon fibers on the surface of the carbon/epoxy composite bipolar plate was developed. Soft release films were inserted between the mold and the composite to prevent the formation of a resin-rich area and to expose carbon fibers on the surface of the bipolar plate. The developed method considerably decreased the ASR of the carbon composite bipolar plate without an expanded graphite coating, which satisfied the target established by the Department of Energy (DOE) of United States. The effects of the soft layer on the mechanical and electrical properties of the carbon composite bipolar plate were investigated.</P>

A Low-Density Graphite-Polymer Composite as a Bipolar Plate for Proton Exchange Membrane Fuel Cells

S.R. Dhakate,S. Sharma,R.B. Mathur 한국탄소학회 2013 Carbon Letters Vol.14 No.1

The bipolar plate is the most important and most costly component of proton exchange membrane fuel cells. The development of a suitable low density bipolar plate is scientif-cally and technically challenging due to the need to maintain high electrical conductivity and mechanical properties. Here, bipolar plates were developed from different particle sizes of natural and expanded graphite with phenolic resin as a polymeric matrix. It was observed that the particle size of the reinforcement significantlyinfluencesthe mechanical and electri-cal properties of a composite bipolar plate. The composite bipolar plate based on expanded graphite gives the desired mechanical and electrical properties as per the US Department of Energy target, with a bulk density of 1.55 g.cm-3 as compared to that of ~1.87 g.cm-3 for a composite plate based on natural graphite (NG). Although the bulk density of the expanded-graphite-based composite plate is ~20% less than that of the NG-based plate, the I-V perfor-mance of the expanded graphite plate is superior to that of the NG plate as a consequence of the higher conductivity. The expanded graphite plate can thus be used as an electromagnetic interference shielding material.

Fabrication of Aluminum Bipolar Plates by Semi‐solid Forging Process and Performance Test of TiN Coated Aluminum Bipolar Plates

Jin, C. K.,Jung, M. G.,Kang, C. G. WILEY-VCH 2014 Fuel Cells Vol. No.

<P><B>Abstract</B></P><P>Aluminum bipolar plates that can replace graphite bipolar plates for PEM fuel cells are made by applying a semi‐solid forging process. A semi‐solid slurry is made using electromagnetic stirring (EMS), and the resulting slurry is injected into a forging die attached to a 200 ton hydraulic press. The slurry is then compressed with a punch, flowed into a die cavity, and solidified into the bipolar plate form. A356 (cast Al alloy), A6061 (wrought Al alloy), and A1100 (pure Al) are used to make the plates. Titanium nitride (TiN) coating is deposited on the aluminum bipolar plates. An atomic force microscope (AFM) is used to measure the surface roughness of the plates. TiN coated A356 and A1100 plates have a surface roughness of <I>R</I><SUB>a</SUB> < 1.2 μm. The plate thickness is 1.2 mm. The active area of the channel is 70 mm × 70 mm, with a depth and width of 0.3 and 1.0 mm, respectively. The three TiN‐coated aluminum plates are combined with a unit cell for a performance test. Our results show that a current density value of 473 mA cm<SUP>–2</SUP> (about 41% of the current density value of commercial graphite plates) can be obtained.</P>

Electrical contact resistance between anode and cathode bipolar plates with respect to surface conditions

Kim, Minkook,Lim, Jun Woo,Lee, Dai Gil Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.189 No.-

<P><B>Abstract</B></P> <P>Proton exchange membrane fuel cells (PEMFCs) are one of the most popular alternative power sources for next-generation automobile applications. A bipolar plate is a multifunctional component that performs various roles in the PEMFC stack. Recently, thin (<200 μm) bipolar plates made from a continuous carbon fiber reinforced composite (CFRP) have been developed to reduce the mass and cost of the PEMFC stacks. The electrical contact resistance (ECR) between the CFRP bipolar plates is much higher than the ECR between the gas diffusion layer (GDL) and bipolar plate. However, until now, only the ECR between the GDL and bipolar plate has been considered the most important technical target.</P> <P>In this study, the ECR between bipolar plates without bulk resistance were measured to present a standard contact resistance value. The ECR of various types of carbon-based materials for bipolar plate was investigated with respect to hardness and resistivity. A mechanical abrasion method using sandpaper was applied to the surface of CFRPs to remove the resin-rich area and control the surface topology. As a result, the ECR between bipolar plates was quantified with respect to the surface hardness, resistivity and roughness, and optimum surface treatment conditions were obtained to minimize the ECR.</P>