Bipolar plate for fuel cell and preparation method thereof
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a bipolar plate for a fuel cell and a preparation method thereof.
Background
A Fuel Cell (FC) is a power generation device that directly converts chemical energy stored in a Fuel and an oxidant into electrical energy with high efficiency. Fuel cells are receiving more and more attention due to their high energy conversion efficiency and non-pollution characteristics.
The bipolar plate is one of the core components of a fuel cell, and has functions of separating an oxidant and a reductant, collecting current, distributing fluid, supporting electrodes, and the like. In the fuel cell, the weight of the bipolar plate accounts for 70-80% of the total weight of the cell, and the manufacturing cost accounts for 40-50% of the total cost; meanwhile, the bipolar plate is also a key factor for limiting the service life of the cell, so that the performance of the bipolar plate has an important influence on the performance of the fuel cell.
An ideal bipolar plate should have a small thickness, as well as good electrical conductivity, corrosion resistance and mechanical strength. The bipolar plates widely used at present mainly include graphite bipolar plates, metal and graphite composite bipolar plates, bipolar plates formed by injection molding of polymer resin and graphite doping, and the like. The graphite bipolar plate has good conductivity and corrosion resistance, but the graphite is a brittle substance and is not easy to thin, so that the power density of a galvanic pile is influenced, and the graphite bipolar plate can be cracked due to road jolt when applied to an electric automobile. The metal bipolar plate is generally made of stainless steel, has high mechanical strength, can realize thinner thickness and has good electrical conductivity compared with a graphite bipolar plate, but is easy to corrode or passivate in the internal environment of the battery, so that the electrical conductivity is reduced sharply. The metal and graphite composite bipolar plate is generally only used for simply bonding two materials, combines the advantages of the two materials, but also combines the disadvantages of the two materials, and has the disadvantages of complicated manufacturing process and high cost. Other composite bipolar plates have the problems of poor electrical conductivity and mechanical strength although being light in weight and good in corrosion resistance. In order to accelerate the realization of large-scale application of fuel cells, the development of novel bipolar plates is an important research direction.
Disclosure of Invention
The invention aims to provide a novel bipolar plate for a fuel cell and a preparation method thereof, which can improve the performances of the bipolar plate such as conductivity, corrosion resistance and the like.
In order to achieve the purpose, the invention adopts the following technical solutions:
a bipolar plate for a fuel cell, comprising: the bipolar plate comprises a bipolar plate base body formed by tightly weaving fiber wires, wherein a flow field is constructed on the surface of one side or two sides of the bipolar plate base body.
More specifically, the fiber yarn is a single yarn or a plied yarn formed by twisting a plurality of single yarns.
More specifically, the fiber wire is a single-strand wire having a cross-sectional diameter of 1 μm to 1000. mu.m.
More specifically, the fiber yarn is a plied yarn with the cross-sectional diameter of 2-1000 μm.
More specifically, the bipolar plate substrate is formed by closely weaving one or more fiber threads.
More specifically, the fiber wire is a metal fiber wire or a nonmetal fiber wire, the metal fiber wire is an iron-based alloy fiber wire or a nickel-based alloy fiber wire or an aluminum fiber wire or a silver fiber wire or a platinum fiber wire or a gold fiber wire, and the nonmetal fiber wire is a carbon fiber wire.
More specifically, the flow field is a bulge formed by weaving fiber wires on the surface of the bipolar plate substrate.
Preferably, at least one layer of coating is coated on the surface of the convex part, and the coating is a silver layer or a platinum layer or a gold layer or a titanium-based alloy layer or a tungsten-based alloy layer.
Preferably, the surface of the fiber line is coated with at least one protective layer, and the protective layer is a silver layer, a platinum layer or a gold layer.
Preferably, at least one layer of coating is coated on at least one side surface of the bipolar plate substrate, and the coating is a silver layer or a platinum layer or a gold layer or a titanium-based alloy layer or a tungsten-based alloy layer.
The method for preparing the bipolar plate for the fuel cell comprises the following steps:
tightly weaving fiber wires to form a sheet-shaped fabric, and cutting the sheet-shaped fabric to obtain a bipolar plate substrate;
and pressing the surface of the bipolar plate substrate to form a flow field, or weaving a convex part on the surface of the bipolar plate substrate by using a fiber wire to form the flow field.
More specifically, the bipolar plate substrate is edge-sealed by a fiber line.
More specifically, the fiber wires are woven into the bipolar plate substrate in a transverse and longitudinal alternate wiring manner.
According to the technical scheme, the bipolar plate is formed by tightly weaving fiber wires, the selection of the fiber materials can be adjusted according to different requirements of the conductivity, the corrosion resistance and the volume of the bipolar plate, and if the bipolar plate needs higher conductivity, a metal fiber can be used for weaving a bipolar plate substrate; when long service life is required, noble metal fibers or carbon fibers can be selected to weave the bipolar plate substrate; when a bipolar plate with smaller thickness is needed, fiber materials with smaller section diameter and the like can be selected, and the bipolar plate with corresponding characteristics can be prepared by weaving fiber wires with different characteristics together. The bipolar plate substrate is prepared by a weaving method, has air tightness and certain toughness, and can be made into a flexible bipolar plate for a flexible fuel cell.
Drawings
Fig. 1 is a schematic view of a bipolar plate substrate according to example 1 of the present invention;
FIG. 2 is a schematic view of a bipolar plate according to example 1 of the present invention;
fig. 3 is a schematic view of a bipolar plate substrate according to embodiment 2 of the present invention.
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
Detailed Description
In the fuel cell, the bipolar plate must have airtightness because oxidizing gas and reducing gas are respectively present on both sides of the bipolar plate and these two gases cannot be brought into direct contact with each other. In different application occasions, the requirements on the conductivity, the service life, the volume and the flexibility of the bipolar plate are different, and the problem to be solved by the invention is how to obtain the novel bipolar plate with different material characteristics.
The basic idea of the method of the invention is as follows: the bipolar plate matrix is formed by tightly weaving fiber wires, and the bipolar plate obtained by tightly weaving has air tightness and can isolate two gases. The bipolar plate substrate can be woven by one type of fiber wires, and can also be woven by different types of fiber wires alternately; the fiber wire may be a metal fiber wire such as iron-based alloy, nickel-based alloy, aluminum, silver, platinum, gold, or the like, or a non-metal fiber wire such as a carbon fiber wire. After the fiber wires are tightly woven to form the flaky fabric with a certain area, the flaky fabric is cut into required sizes, and the bipolar plate substrate is obtained. If the sheet fabric forming the bipolar plate substrate has plasticity, the sheet fabric can be further pressed into a specific shape to construct a flow field, and if the plasticity of the sheet fabric is poor, the surface of one side or two sides of the fabric can be woven by fiber threads to form convex parts to construct the flow field.
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. It is to be noted that the drawings are in simplified form and are not to precise scale for the purpose of facilitating and clearly aiding in the description of the embodiments of the invention, and that the drawings showing the structure of the device are not to scale but are to be partly exaggerated for the purpose of facilitating the description, and that the schematic drawings are only examples and should not be taken as limiting the scope of the invention.
Example 1
The bipolar plate of the present embodiment is formed by tightly weaving stainless steel fiber wires 1 and carbon fiber wires 2. As shown in fig. 1, the stainless steel fiber wires 1 and the carbon fiber wires 2 are woven in a 1:1 horizontal-longitudinal alternating wiring mode, that is, one stainless steel fiber wire 1 and one carbon fiber wire 2 in the same direction are arranged adjacently. The stainless steel fiber wire 1 and the carbon fiber wire 2 can be single-stranded wires or a plied wire formed by twisting a plurality of single-stranded wires; when the fiber wire is a single strand, the fiber wire may have a section diameter of 1 μm to 1000 μm, and when the fiber wire is a plied yarn formed by twisting a plurality of single strands, the fiber wire may have a section diameter of 2 μm to 1000 μm.
The stainless steel carbon fiber wire 1 and the carbon fiber wire 2 of the present embodiment each have a cross-sectional diameter of 0.5mm and are each formed by twisting a plurality of single-stranded wires. The stainless steel fiber wires 1 and the carbon fiber wires 2 are tightly woven into a single-layer fabric with the thickness of 1.5mm, square pieces with the length of 5cm multiplied by the width of 5cm are cut, and the carbon fiber wires with the section diameter of 0.5mm are used for edge sealing to obtain the bipolar plate substrate 3. As shown in fig. 2, in the present embodiment, the projections 4 having a height of 1mm and a width of 2mm are symmetrically woven on both side surfaces of the bipolar plate substrate 3 using carbon fiber wires having a cross-sectional diameter of 0.5mm, respectively, and the projections 4 are used to form a U-shaped flow field. Similarly, the fiber yarn for forming the protrusions may be a single fiber yarn or a twisted fiber yarn of a plurality of single yarns having a cross-sectional diameter of 1 μm to 1000 μm, and a fiber yarn of a twisted plurality of single yarns having a cross-sectional diameter of 2 μm to 1000 μm. The projections may be woven using one or more types of fiber yarns, which may or may not be the same type of fiber yarn used for the bipolar plate substrate. When the bipolar plate substrate has projections formed of fiber threads on both side surfaces, the types of the fiber threads of the projections on the different side surfaces may be the same or different.
The bipolar plate formed by weaving the stainless steel fiber wires and the carbon fiber wires has the advantages of both the metal material and the carbon material, and the contact resistance with the carbon paper is about 7.0m omega/cm under the pressure of 0.6MPa2The flexible conductive membrane has good conductivity and mechanical strength, small thickness, light weight and certain flexibility, and can be used for manufacturing flexible fuel cells.
Example 2
This example differs from example 1 in that: the bipolar plate substrate is woven by stainless steel fiber wires 1 and carbon fiber wires 2 in a 2:1 horizontal-longitudinal alternating wiring mode, namely two stainless steel fiber wires 1 and one carbon fiber wire 2 in the same direction are arranged adjacently (figure 3).
When the fuel cell works, the bipolar plate is in a high-temperature, strong oxidation reduction and acid environment, and metal materials such as stainless steel and the like are easy to corrode and passivate in the environment, so that the conductivity is greatly reduced. In order to improve the corrosion resistance of the fiber wires and prolong the service life of the bipolar plate, at least one protective layer can be coated on the outer surface of the fiber wires used for weaving the bipolar plate matrix and/or used for weaving the convex parts, and the protective layer can be made of silver, platinum or gold. Or at least one layer of coating is coated on the surface of one side or two sides of the bipolar plate substrate with the flow field built, and the coating can be made of silver, platinum, gold, titanium-based alloy or tungsten-based alloy and is used for protecting the bipolar plate. When the bipolar plate substrate has coatings on both surfaces, the coatings on both sides of the bipolar plate substrate may be the same or different. The surface of the projections may also be coated with one or more of the aforementioned coatings, and the coatings of the projections on the different side surfaces may be the same or different.
In this embodiment, after the weaving of the protrusions is completed, gold is sputtered on both surfaces of the bipolar plate substrate to form a protective coating, and the thickness of the gold layer is 50 nm. The bipolar plate prepared in the example has a contact resistance of about 5.3m omega/cm with carbon paper under a pressure of 0.6MPa2。
In the foregoing embodiment, the bipolar plate is formed by tightly weaving the fiber threads in a criss-cross manner, but other conventional weaving manners may be used, for example, weaving in a manner that the fiber threads are bent into loops and then sleeved with each other, as long as an airtight fabric is formed.
In the description, each part is described in a progressive manner, each part is emphasized to be different from other parts, and the same or similar parts among the parts are referred to each other. The combination of each component is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and the foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.