Preparation and properties of graphite/polypropylene composite material reinforced by chopped carbon fibers for proton‐exchange membrane fuel cell bipolar plates

Abstract

In this work, chopped carbon fibers (CCFs) with different lengths were added to graphite/polypropylene (PP) composite materials to achieve high conductivity and flexural strength performances, which are required for use in proton exchange membrane fuel cells. The effects of CCF length (2-4 mm), CCF content (0-5 wt.%), graphite type-natural flake graphite (NFG) and synthetic graphite (SG), and graphite particle size (18-106 µm) on the graphite/PP/CCFs composites are examined. The conductivities of the composites decrease significantly with increasing CCF length above 3 wt.%. CCFs improve the composite's strength, with a maximum strength of 45.8 MPa being achieved with 5 wt.% of 4 mm long CCFs. Composite with NFG exhibits superior conductivity to the one with SG but lacks flexural strength. The NFG particle size significantly affects the conductivity of the composite at high graphite contents, with a particle diameter of 75 µm resulting in maximum conductivity. An optimal composition with 38 µm/82 wt.% NFG and 2 mm/3 wt.% CCF, electrical conductivity, and flexural strength of 189.4 S/cm and 30.2 MPa, respectively, were achieved. Also, this composite exhibited interfacial contact resistance 2.52 mΩ ⋅ cm 2 and contact angles of 111 • , which showed favorable interfacial conductivity and hydrophobicity performances.

Current status of research on composite bipolar plates for proton exchange membrane fuel cells (PEMFCs): nanofillers and structure optimization

“…2 Bipolar plate performance needs and research directions at a glance. 36,37,[47][48][49][50][51][55][56][57][58][59][60][61][62][63][64][65][66][67] composite bipolar plates due to their small particle size, which gives them a high surface energy. In addition, because most of the carbon-based nanollers have poor compatibility with resins, [86][87][88] excessive addition of nanollers can not be wetted by resin.…”

“…As a kind of new type of bipolar plate with increased research heat in recent years, it combines the advantages of metal bipolar plate and graphite bipolar plate: easy to be processed, 54 good corrosion resistance, and low cost, 36,55,56 but due to the problems of poor compatibility between the resin and the graphite, the electrical conductivity and the mechanical properties are difficult to be balanced, and the porosity is large. In order to solve the problem of poor performance of composite bipolar plates, 57,58 the current primary use by adding conductive llers, such as carbon nanotubes (CNTs), 59,60 graphene, 60 carbon bers, [61][62][63] carbon black, [64][65][66][67] etc. Among these conductive llers, nanollers have become the main second conductive ller due to their excellent performance and signicant effect, oen used together with graphite to enhance the performance of composite bipolar plates.…”

Progress in the study of bipolar plates/conductive fillers

“…Dhakate et al [12] developed expanded graphite-based nanocomposites by compression molding technique and obtained the samples with a packing density of 1.5-1.55 g/cm -3 . Compared with graphite resin-based composite (>12 GPa) plates, the Expanded graphite (3-8 GPa) composites have lower modulus values.Wei et al [13] prepared graphite/PP/CCFs composites using two different types of graphite powders as primary conductive fillers and PP as binder. The experimental results showed that the NFG-containing composites had higher electrical conductivity than the SG-containing composites for the same graphite particle size.…”

Development of novel composite bipolar plates using surface‐modified conductive carbon filler materials for polymer electrolyte membrane fuel cells

“…As an energy source for electric automobiles, PEMFC is advantageous because of its minimal emission of environmental pollutants and higher energy conversion rate. [12][13][14] Electric motors in fuel cell electric vehicles are operated by electricity produced from PEMFC. This system produces only water as a byproduct with high efficiency.…”

“…Proton exchange membrane fuel cell (PEMFC) is a prominent fuel cell for applications in electric vehicles. As an energy source for electric automobiles, PEMFC is advantageous because of its minimal emission of environmental pollutants and higher energy conversion rate 12–14 . Electric motors in fuel cell electric vehicles are operated by electricity produced from PEMFC.…”