• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.180-183
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• 2009

Composite bipolar plates offer several advantages of low cost, light weight, and ease of manufacturing compared to traditional graphite plate. However, it is difficult to achieve both high electrical conductivity and high flexural strength. In this study, the hybrid carbons filled epoxy composite bipolar plates were fabricated to test electrical conductivity and flexural properties. Graphite powders were used as the main conducting filler and continuous carbon fiber fabrics were inserted to improve the mechanical properties of the composite. This hybrid composite showed improved in-plane electrical conductivity and flexural property. The moldability of the hybrid composite was also improved comparing to the continuous prepreg composite. This study suggested that the continuous carbon fiber inserted graphite/epoxy composites can be a potential candidate material to overcome the disadvantages of conventional graphite composite or continuous prepreg composite bipolar plates.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.3
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• pp.221-232
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• 2017

In this study, bipolar plates in fuel cells are formed using rubber forming process. The effects of important parameters in rubber forming such as hardness and thickness of rubber pad, speed and pressure of punch that compress blank, and physical property of materials on the channel depth were analyzed. In the soft material sheet Al1050, deeper channels are formed than in materials STS304 and Ti-G5. Formed channel depth was increased when hardness of rubber pad was lower, thickness of rubber pad was high, and speed and pressure of punch were high. It was found the deepest channel was achieved when forming process condition was set with punch speed and pressure at 30 mm/s and 55 MPa, respectively using rubber pad having hardness Shore A 20 and thickness 60 mm. The channel depths of bipolar plates formed with Al1050, STS304 and Ti-G5 under the above process condition were 0.453, 0.307, and 0.270 mm, respectively. There were no defects such as wrinkle, distortion, and crack found from formed bipolar plates.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.4
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• pp.313-320
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• 2002

The characteristics of the AISI bipolar plates have been investigated to replace the expensive graphite bipolar plates. It was found from the contact resistance evaluation of graphites, composites, and AISI that the contact resistance of AISI was the lowest, but it could approach to that of composites at higher compression forces. The single cell operation using the AISI bipolar plates revealed that the lower performance of the AISI single cell compared to the graphite one was due to not only the higher contact resistance but the flooding effect caused by high wettability of AISI. The performance of the AISI single cell could be improved if the channels were modified appropriately. The large size AISI single cell was operated to investigated the size effect on the performance.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.172-175
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• 2009

A bipolar plate is an important component in a fuel cell in the sense of cost and weight. This study aimed at developing highly conductive, lightweight, and low cost bipolar plates. Hybrid carbons filled poly(phenylene sulfide)(PPS) composite bipolar plates were prepared by using the compression molding technique. Various types and amounts of conducting carbon fillers such as graphite, carbon black, carbon fibers, and carbon nanotubes (CNTs) were adopted for the composites. Electrical conductivity and mechanical properties of the composites were measured in order to investigate effects of each components of fillers. When the graphite is only used as a conducting filler, the electrical conductivity of the composites increases with increasing the content, but the flexural strength decreases dramatically. However, for CNTs and carbon fibers, the flexural strength initially increases and then decreases with increasing the amount of the conducting fillers. The amount of graphite corresponding to the peak of flexural strength was moved to lower content with increasing the amount of CNTs or carbon fiber. When hybrid conducting fillers such as fibrous and particulate fillers were used, the synergy effect in mechanical and electrical properties was observed.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3589-3592
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• 2012

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.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.146-149
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• 2007

The 2-step manufacturing method consisting of preforming and stamping processes was developed to manufacture composite bipolar plates for PEMFCs. The preform was composed of expanded graphite, graphite flake and phenol resin. Precuring conditions were optimized by checking the electrical conductivity, flexural strength and microstructure. Precuring temperature ($100^{\circ}C$) slightly above the melting point of phenol powders ($90^{\circ}C$) induced moderate curing, but also prevented excessive curing. Preforms utilizing the tangled structure of expanded graphite were easily fabricated at low pressure of 0.07-0.28MPa. The proper precuring time, 5min, was determined to fabricate the preform stably because insufficient and excessive precuring deteriorated the flexural strength of composite bipolar plates.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.722-727
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• 2009

The bipolar plates are not only the major part of the polymer electrolyte membrane fuel cell (PEMFC) stack in weight and volume, but also a significant contributor to the stack costs. Stainless steels are considered to be good candidates for bipolar plate materials of the PEMFC due to their low cost, high strength and easy machining, as well as corrosion resistance. In this paper, 316L stainless steel with and without nitrogen ion implantation were tested in simulated PEMFC environments for application as bipolar plates. The results showed that the nitride formed by nitrogen ion implantation contributed the decrease of the interfacial contact resistance without degradation of corrosion property. The combination of excellent properties indicated that nitrogen ion implanted stainless steel could be potential candidate materials as bipolar plates in PEMFC. Current efforts have focused on optimizing the condition of ion implantation.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.283-291
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• 2011

Polymer electrolyte membrane fuel cells (PEMFCs) use the bipolar plate of various materials between electrolyte and contact electrode for the stable hydrogen ion exchange activation. The bipolar plate of various materials has representatively graphite and stainless steel. Specially, stainless steels have advantage for low cost and high product rate. In this study, SUS 316 was effectively coated with 600 nm thick F-doped tin oxide (SnOx:F) by electron cyclotron resonance-metal organic chemical vapor deposition and investigated in simulated fuel cell bipolar plates. The results showed that an F-doped tin oxide (SnOx:F) coating enhanced the corrosion resistance of the alloys in fuel cell bipolar plates, though the substrate steel has a significant influence on the behavior of the coating. Coating SUS 316 for fuel cell bipolar plates steel further improved the already excellent corrosion resistance of this material. After coating, the increased ICR values of the coated steels compared to those of the fresh steels. The SnOx:F coating seems to add an additional resistance to the native air-formed film on these stainless steels.

• New & Renewable Energy
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• v.3 no.4
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• pp.3-7
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• 2007

Graphite/polymer composite bipolar plates for PEMFC are successfully developed, and their typical properties are superior to commercially available ones. Thermal property of the developed bipolar plate was evaluated by dynamic mechanical analyzer, and the results were compared to commercial ones. The specimens were immersed into the deionized water bath at $80^{\circ}$... for 1500hrs to evaluate dimensional stability and durability. Dimension, weight of the specimens as well as extraction conductivity was measured as each 500hrs. Fully molded bipolar plates without any machining or milling were also prepared using a specially developed mold, and they were applied to the fuel cell performance test. Results were compared to the machined commercial bipolar plate.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.5-7
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• 2007

Graphite/polymer composite bipolar plates for PEMFC are successfully developed, and their typical properties are superior to commercially available ones. Thermal property of the developed bipolar plate was evaluated by dynamic mechanical analyzer, and the results were compared to commercial ones. The specimens were immersed into the deionized water bath at $80^{\circ}C$ for 1500hrs to evaluate dimensional stability and durability. Dimension, weight of the specimens as well as extraction conductivity was measured as each 500hrs. Fully molded bipolar plates without any machining or milling were also prepared using a specially developed mold, and they were applied to the fuel cell performance test. Results were compared to the machined commercial bipolar plate.