CN110581291B

CN110581291B - Use of silicon in fuel cells

Info

Publication number: CN110581291B
Application number: CN201810577217.7A
Authority: CN
Inventors: 施正荣; 朱景兵
Original assignee: Shanghai Shangli Investment Co ltd
Current assignee: Zhejiang Haihao New Energy Technology Co ltd
Priority date: 2018-06-07
Filing date: 2018-06-07
Publication date: 2021-12-03
Anticipated expiration: 2038-06-07
Also published as: CN110581291A

Abstract

The invention discloses an application of silicon in a fuel cell, wherein the fuel cell comprises 1 or more fuel cell units; the fuel cell unit comprises an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode and a cathode plate which are sequentially stacked into a whole; the cathode plate and the anode plate are silicon electrode plates made of doped conductive crystalline silicon materials; the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet-outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage; compared with a metal polar plate, a graphite polar plate or a composite material polar plate in the prior art, the silicon polar plate provided by the invention has better advantages in service life, cost, efficiency and power density, and has great significance and core propulsion undoubtedly for the large-scale industrialization process of fuel cells.

Description

Use of silicon in fuel cells

Technical Field

The invention belongs to the field of fuel cells, and particularly relates to application of silicon in fuel cells.

Background

A fuel cell is a chemical device that directly converts chemical energy of fuel into electrical energy, and is also called an electrochemical generator. The fuel cell converts the Gibbs free energy in the chemical energy of the fuel into electric energy through electrochemical reaction, is not limited by Carnot cycle effect, and has high energy conversion rate; the reaction product of the fuel cell which adopts hydrogen as fuel is water, so that the method is environment-friendly and can realize zero-pollution emission theoretically; in addition, the fuel cell has no mechanical transmission part, few moving parts and low noise during working; the fuel cell has the advantages of high specific energy, high reliability, wide fuel range, short starting time, small volume, convenient carrying and the like. It follows that fuel cells are currently the most promising power generation technology from the viewpoint of energy conservation and ecological environment conservation.

Structurally, a fuel cell generally includes an Electrode (Electrode), an Electrolyte Membrane (Electrolyte Membrane), and a Current Collector (Current Collector); among them, the electrode of the fuel cell is an electrochemical reaction site where oxidation reaction of fuel and reduction reaction of oxidant occur, and in order to promote the reaction, a catalyst is generally further provided on the electrode; the main function of the electrolyte membrane is to separate the oxidant and the reductant and to conduct ions; the current collector, also commonly called Bipolar Plate (Bipolar Plate), is an important performance element in the fuel cell stack, and the Bipolar Plate is responsible for distributing fuel and air to the surfaces of the cathode and anode and for dissipating heat of the stack, and is also a key component responsible for connecting the single cells in series to form the stack, and mainly plays a role in dividing the oxidant, the reducing agent and the coolant and collecting current, and has a great weight on the aspects of the mass, the volume, the cost, the reliability, the power density and the like of the fuel cell stack, and the cost occupies 20-60% of the cost of the whole fuel cell. Therefore, the development of high-performance, low-cost bipolar plate materials is of great significance for large-scale commercial application of fuel cells. The development of the bipolar plate material occupies 40-60% of the development cost of the fuel cell, and on the other hand, the bipolar plate is proved to be the key factor determining the industrialization of the fuel cell.

The research proves that the bipolar plate has the following characteristics: good air blocking function; better heat-conducting property; lower bulk and contact resistance; the corrosion resistance is strong; light weight, high strength, suitability for batch processing and the like.

In the prior art, the bipolar plate of the fuel cell mainly comprises a graphite plate or a metal plate, wherein the graphite plate is mainly prepared by pressing carbon powder or graphite powder mixed with graphitizable resin, and mainly has the defects of large volume, small power density and small strength; the metal plate is generally directly processed by stainless steel, titanium alloy, aluminum alloy and the like, mainly has the defect of easy corrosion, generally needs various surface modifications, and further brings the problems of complex preparation process and high cost; the composite plate is made of composite material, which is prepared through mixing thermoplastic or thermosetting resin with graphite powder reinforced fiber to form prefabricated material, curing, graphitizing and other steps, and has poor conducting effect and high cost.

Therefore, a suitable bipolar plate material is sought as a bipolar plate of a fuel cell and satisfies a good gas barrier function required for the bipolar plate; better heat-conducting property; lower bulk and contact resistance; the corrosion resistance is strong; the fuel cell has the characteristics of light weight, high strength, suitability for batch processing and the like, and has undoubtedly great significance and core propulsion effect on the mass industrialization process of the fuel cell.

Disclosure of Invention

In view of the above, the present invention is directed to provide an application of silicon in a fuel cell, and provides a bipolar plate of a fuel cell directly using a silicon plate, which not only satisfies the requirement of the bipolar plate for a good gas blocking function; better heat-conducting property; lower bulk and contact resistance; the corrosion resistance is strong; light weight, high strength, suitability for batch processing and the like; compared with the metal polar plate, the graphite polar plate or the composite material polar plate in the prior art, the invention has better advantages in service life, cost, efficiency and power density, and undoubtedly has great significance and core propulsion effect on the large-scale industrialization process of the fuel cell.

Before the technical scheme of the invention is proposed, the applicant finds some suspected prior technical schemes close to the invention through careful batch search, and the applicant performs careful reading and key analysis:

the literature on periodicals describes: the material silicon has the characteristics of low gas permeability, high heat conductivity coefficient, easy processing and the like, is an ideal substrate material in the manufacture of micro fuel cells, and can obtain electric conductivity and better stability and corrosion resistance by plating metal (usually noble metal) on the surface of the silicon. In 2000, Kelly and Meyers first published relevant literature for fabricating micro fuel cells on silicon. Silicon has since been a major development in micro fuel cells. The Kim uses silicon as a substrate to manufacture a micro fuel cell, the size of a flow channel of the micro fuel cell is 400 micrometers (width) and 230 micrometers (depth), and heat-resistant glass with the thickness of 500 micrometers is added on the back of a silicon micro bipolar plate, so that the physical strength of the micro fuel cell is enhanced, and the defect that a silicon wafer is fragile is overcome; and gold is plated on the silicon bipolar plate, so that the silicon bipolar plate has better stability, and the actual power density is 203mW/cm when the output voltage is 0.6V²The maximum power density can reach 261mW/cm²The volume specific power density of the battery is 360mW/cm³However, the silicon material as the bipolar plate material has some disadvantages, such as the need of plating with noble metal to collect the current, which not only increases the production process, but also increases the material cost. Through careful analysis by the applicant, it has been found that these techniques exploit the hermetic, heat-transfer and delicate characteristics of silicon, and thereforeThe silicon chip is directly used as a substrate of the fuel cell, a metal layer for collecting current is formed on the silicon substrate, the current generated by the electrode is collected and flows out of the cell along the direction parallel to the surface of the silicon substrate, and the structure can only be made into the fuel cell with a small area because the current is conducted along the metal layer film and cannot be stacked in a multi-layer manner; meanwhile, because a structure for providing cooling medium flow cannot be arranged inside the silicon substrate structure, the technical scheme of adopting silicon material as the fuel cell polar plate substrate can only be applied to micro fuel cell products for a long time.

As described above, the applicant has found through further search that the prior art solution of applying silicon material to fuel cell is suspected to be disclosed, and in order to better illustrate the technical solution of the present invention, the applicant further specifically lists the following patent documents to illustrate the difference between the technical solutions and the present invention:

1. if the chinese patent with the publication number of CN100397687C discloses a cathode flow field plate of a self-breathing micro proton exchange membrane fuel cell and a manufacturing method thereof, a new structure processed by the MEMS technology is adopted, and specifically, the following are proposed: the flow field plate is structurally characterized in that a cathode flow field is processed into a double-layer composite hollow structure on a silicon sheet material with the thickness of about 300-; the silicon polar plate of the method is used as a cathode substrate structure of the micro fuel cell, a precious metal conducting layer is required to be arranged on the silicon substrate to realize the current collecting function required by the polar plate structure, the preparation process is complex, the material cost is high, a cooling water flow channel cannot be arranged, and only the micro fuel cell can be manufactured;

2. the invention patent with the publication number of CN101894954B discloses a method for packaging a microminiature fuel cell based on a normal temperature bonding technology, which provides a method for manufacturing a cathode plate and an anode plate.A thermal oxidation method is used for growing 50nm silicon dioxide on two sides of a crystal orientation double-sided polished silicon wafer as a stress buffer layer, then LPCVD is used for depositing 160nm silicon nitride as a masking layer, 20nm Cr is sputtered on the front side as an adhesion layer, 0.2 micron Au is sputtered on the front side as a current collection layer, then the exposed silicon nitride is removed by reactive ion etching after a flow field structure pattern is photoetched, and a photoresist colloid is removed; then, using KOH solution and ultrasonic wave to corrode the silicon wafer, and stopping when corrosion surfaces on two sides meet to form a through inlet, outlet and through hole; finally, removing the silicon nitride exposed on the front surface by reactive ion etching, and removing the silicon dioxide bonded on the front surface by hydrofluoric acid aqueous solution; the silicon electrode plate of the method is also used as an electrode plate substrate structure of the micro fuel cell, a precious metal conducting layer (Au or Pt, and Cr is also needed to be arranged as an adhesion layer) is needed to be arranged on the silicon substrate to realize the current collecting function required by the electrode plate structure, the preparation process is complex, the material cost is high, a cooling water flow channel cannot be arranged, and only the micro fuel cell can be manufactured;

3. the invention patent with publication number CN101867052A discloses a spoke type self-breathing micro fuel cell and a preparation method thereof, wherein silicon wafers are used as a cathode plate and an anode plate, and the specific process is as follows: cleaning a silicon wafer, preparing a silicon nitride film serving as a corrosion mask on the surface of the silicon wafer by using a low-pressure chemical vapor deposition method, and forming a mask pattern on the film by using a photoetching technology so as to realize the purpose of selective corrosion; carrying out anisotropic corrosion on a silicon wafer by adopting a 40% KOH solution, removing a residual silicon nitride film on the surface of the silicon wafer by utilizing a reactive ion etching method, forming an inlet and outlet channel with steep side walls on the surface of the silicon wafer by adopting a laser processing technology, and forming a Ti/Au metal layer on the corrosion surface of the silicon wafer by utilizing a magnetron sputtering technology for collecting and conducting current; similarly, the silicon plate of the method is also used as a plate substrate structure of the micro fuel cell, and not only a precious metal conducting layer (Ti/Au) is required to be arranged on the silicon substrate to realize the current collecting function required by the plate structure, the preparation process is complex, the material cost is high, but also a cooling water flow channel cannot be arranged, and only the micro fuel cell can be manufactured;

4. the invention patent with the publication number of CN100483829C discloses a stacked silicon-based micro fuel cell set and a manufacturing method thereof, wherein a silicon substrate is adopted, and specifically an etching method of a silicon polar plate is disclosed, silicon dioxide grows on two sides of a crystal-oriented double-sided polished silicon wafer by a thermal oxidation method, then LPCVD0.1 micron silicon nitride is used as a masking layer, and photoetching exposed silicon nitride is removed by reactive ion etching after a flow field structure pattern is photoetched, and a photoresist is removed; then, using KOH solution and ultrasonic wave to corrode the silicon wafer, and stopping when corrosion surfaces on two sides meet to form a through inlet, outlet and through hole; similarly, the silicon electrode plate of the method is also used as a substrate structure of the micro fuel cell, and not only a precious metal conducting layer (Ti/Pt) is required to be arranged on the silicon substrate to realize the current collecting function required by the electrode plate structure, the preparation process is complex, the material cost is high, but also a cooling water flow channel cannot be arranged, and only the micro fuel cell can be manufactured;

5. the invention patent with the publication number of CN100369304C discloses a preparation method of a catalytic electrode for a silicon-based micro direct methanol fuel cell, and particularly discloses a method for preparing a catalytic electrode for a silicon-based micro direct methanol fuel cell, which comprises the steps of cleaning a silicon wafer with the resistivity of 0.012-0.013 omega cm and the P-type or N-type crystal orientation of <100>, oxidizing to generate a silicon dioxide layer with the thickness of 1.0-1.5 microns, forming a flow field pattern by adopting a photoetching technology, and corroding a channel flow field on the silicon wafer by adopting a wet corrosion technology, wherein the corrosion depth is 150-240 microns; and finally, forming porous silicon on the surface of the silicon wafer by an electrochemical method, and greatly increasing the effective reaction area of the catalyst on the surface of the porous silicon after the catalyst is deposited on the surface of the porous silicon. In the fuel cell, a silicon chip is used as a carrier of a catalytic electrode material of the micro fuel cell, and the technical problem to be solved by using crystalline silicon to manufacture a polar plate and the technical scheme adopted by the invention are different.

In conjunction with the above, these prior doubts propose the technical solutions of using silicon material for fuel cells, the applicant found that these technical solutions either only use the silicon plate as the substrate support of the plate component thereof, and need to coat the silicon plate with a material such as noble metal to be actually used for current collection of the plate component of the fuel cell, as described in the above-mentioned journal, 1.CN100397687C, 2.CN101894954B, 3.CN101867052A, 4, CN 100483829C; or the silicon wafer is made into a porous silicon structure and used as a catalyst carrier and an electrode material of a fuel cell, such as 5.CN 100483829C; the prior arts have a common feature that the technical solutions that silicon is used as a substrate of a polar plate or an electrode material are all limited to be applied to micro fuel cells, the micro fuel cells generally adopt 1 or at most 2 fuel cell units, the output power is generally between milliwatt and dozens of watt, and the silicon substrate structure cannot be provided with a cooling water channel, so that the heat dissipation performance cannot be guaranteed; the applicant finds that none of the technical proposals of applying the technical solution concept to the non-micro-scale industrial fuel cell has been proposed, and after the deep analysis of the applicant, the inspiration of the technical methods for making the silicon substrate by using the silicon wafer proposed by the prior art comes from the silicon chip processing technology in the electronic industry, in particular, the MEMS processing technology, which is applied to the micro-scale industrial fuel cell for making the silicon substrate or the porous silicon electrode, while the non-micro-scale industrial fuel cell has a stack structure in which a plurality of fuel cell units are connected in series, firstly the silicon substrate cannot provide enough mechanical supporting force, secondly, precious metal is plated on the silicon electrode plate substrate to realize the current collecting function, and if the non-micro-scale industrial fuel cell is made by using the MEMS processing technology, the cost is too high, has no competitive advantage with metal polar plates or graphite polar plates; more importantly, as mentioned above, these solutions collect the current generated by the electrodes and flow out of the cell in the direction parallel to the silicon substrate, and this structure can only be made into a fuel cell with a small area because it conducts the current along the metal layer film, and cannot be stacked in multiple layers; and the electric pile structure can generate heat in the working process due to high output power, so the polar plate needs to be provided with a cooling water channel besides an oxidant channel and a reducing agent channel. On this basis, therefore, the person skilled in the art would not have any motivation to apply silicon materials to industrial fuel cells on a non-miniature scale.

Through the understanding of the fuel cell and the research, exploration and analysis experiences of the silicon material for decades, the inventor of the present application finds that the silicon material can be completely directly used as a silicon pole plate of the fuel cell after specific selection and design, and compared with a metal pole plate, a graphite pole plate or a composite material pole plate in the prior art, the silicon pole plate of the present invention obtains a surprisingly prominent technical effect, and the main adopted technical scheme is as follows:

use of silicon in a fuel cell comprising 1 or more fuel cell units; the fuel cell unit comprises an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode and a cathode plate which are sequentially stacked into a whole; the cathode plate and the anode plate are silicon electrode plates made of doped conductive crystalline silicon materials; the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage.

Preferably, the silicon electrode plate may serve as both a cathode plate of a single fuel cell unit and an anode plate of a single fuel cell unit adjacent thereto.

Preferably, the silicon plate comprises 2 or more than 2 silicon wafers, wherein the silicon wafers are provided with single-sided or double-sided flow channels; the surface areas of the silicon wafers, which do not cover the flow channels, are connected and stacked into a whole by adopting a conductive material in a composite mode, an internal flow channel located in the silicon polar plate is formed through the composite connection, and the internal flow channel is used as the internal cooling medium flow channel; and the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel.

Preferably, the doped conductive crystalline silicon material is a monocrystalline or polycrystalline doped silicon wafer, and the resistivity of the doped conductive crystalline silicon material is not higher than 0.1 omega.

Preferably, the fuel cell comprises a stack structure, wherein the stack structure comprises end fuel cell units and 1 or more middle fuel cell units, the end fuel cell units are connected in series and stacked into a whole, the end fuel cell units are positioned at two ends, and the middle fuel cell units are positioned in the middle; and the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage.

Preferably, the output power of the pile structure is not lower than 0.1 KW.

Preferably, the end fuel cell unit includes an end silicon plate and the middle silicon plate; the end silicon polar plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage or a back oxidizing agent flow passage; and the internal cooling medium flow passage, the front reducing agent flow passage or the back oxidant flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage or the back oxidant flow passage.

Preferably, the middle silicon plate comprises a first middle silicon wafer and a second middle silicon wafer, wherein the first middle silicon wafer is provided with a first internal cooling medium flow passage on the back side, a reducing agent flow passage on the front side and a first inlet-outlet combination, and the second middle silicon wafer is provided with a second internal cooling medium flow passage on the front side, an oxidizing agent flow passage on the back side and a second inlet-outlet combination; the back surface area of the first middle silicon wafer, which does not cover the first internal cooling medium flow channel, and the front surface area of the second middle silicon wafer, which does not cover the second internal cooling medium flow channel, are compositely connected and stacked into a whole by adopting a conductive material, and the first internal cooling medium flow channel is correspondingly matched with the second internal cooling medium flow channel and forms the internal cooling medium flow channel through the composite connection; and the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form the silicon electrode plate inlet and outlet combination through the composite connection.

Preferably, the end silicon plate comprises an end silicon wafer and a middle silicon wafer, wherein the end silicon wafer is provided with a first internal cooling medium flow passage and a first inlet-outlet combination on the front side or the back side, and the middle silicon wafer is provided with a second internal cooling medium flow passage on the back side or the front side, a reducing agent flow passage on the front side or an oxidizing agent flow passage on the back side and a second inlet-outlet combination; the front side or the back side area of the end silicon wafer, which is not covered by the first internal cooling medium flow channel, and the back side or the front side area of the middle silicon wafer, which is not covered by the second internal cooling medium flow channel, are compositely connected and stacked into a whole by adopting a conductive material, and the first internal cooling medium flow channel is correspondingly matched with the second internal cooling medium flow channel and forms the internal cooling medium flow channel through the composite connection; and the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form the silicon electrode plate inlet and outlet combination through the composite connection.

Preferably, the silicon wafer has a thickness in the range of 0.2 to 5 mm.

Preferably, the silicon wafer has a size in the range of 50-300 mm.

Preferably, in the present invention, the thickness of the conductive material used for composite connection between silicon wafers is in the micron range, and may be 1-100 microns, or 1-50 microns, or 1-20 microns, and in terms of material selection, the conductive material may be a conductive metal material or a conductive non-metal material such as conductive adhesive, and since the conductive non-metal material of conductive adhesive is difficult to process to the micron thickness, and in the composite connection process, organic solvent generally needs to be removed, which is not beneficial to the implementation of the process, therefore, preferably, the conductive material of the present invention is a metal conductive material; in order to facilitate good composite connection between metal conductive materials and between the metal conductive materials and silicon wafers, preferably, the conductive materials of the invention are metal conductive materials having eutectic bonding effect with silicon materials, that is, when the temperature is equal to or close to eutectic temperature (the eutectic temperature is the temperature when the silicon and the corresponding metal conductive materials are subjected to eutectic reaction), the metal conductive materials and the silicon can be subjected to good eutectic reaction, so that a metal conductive material layer between the silicon wafers and a silicon wafer surface layer in contact with the metal conductive material layer are mutually fused and bonded, and an integral silicon-metal conductive alloy composite structure with firm bonding is formed after cooling, and finally, the excellent composite connection effect between the silicon wafers is realized; particularly preferably, these metallic conductive materials may be in particular: nickel Ni, gold Au, silver Ag, copper Cu, aluminum Al and other materials; the eutectic temperature of silicon and these metal conductive materials is usually significantly lower than the melting temperature of silicon itself or the metal conductive materials themselves, and the eutectic temperature range is usually 500-1000 ℃, and the eutectic temperature with silicon can be determined according to the type of the metal conductive material actually used, and these can be obtained by referring to the related prior art information.

Preferably, the flow channel or the inlet and outlet combination is processed on one side or both sides of the silicon wafer by adopting an etching process or a laser process or a screen printing process.

Preferably, the depth of the reducing agent flow channel and/or the oxidizing agent flow channel ranges from 50 to 300 micrometers, and the width ranges from 500 to 3000 micrometers.

The invention provides a silicon polar plate directly taking a doped conductive crystalline silicon material as a fuel cell on the basis of dozens of years of research, exploration and analysis experiences of the inventor of the applicant on a silicon material, and provides the structural design of the silicon polar plate, specifically, the silicon polar plate is formed by stacking and compounding two or more than two silicon wafers, an internal flow channel is formed by stacking and compounding, and the internal flow channel can be directly used as a cooling medium flow channel; the silicon pole plate provided by the invention is used as a framework structure in the fuel cell, so that enough mechanical supporting force can be provided, and the silicon pole plate is directly used as a current collecting plate to transmit current in the stacking direction of the fuel cell, so that a metal film layer is not required to be additionally arranged, and a multi-layer stacking structure required by the fuel cell with a galvanic pile structure is realized; the internal flow channel of the silicon polar plate is directly used as a cooling medium flow channel, so that heat generated in the working process of the fuel cell is further effectively and timely conveyed to the outside; therefore, the silicon polar plate provided by the invention can completely meet the requirement of a fuel cell bipolar plate on good gas resistance function; better heat-conducting property; lower bulk and contact resistance; the corrosion resistance is strong; compared with the metal polar plate, the graphite polar plate or the composite material polar plate in the prior art, the silicon polar plate provided by the invention has better advantages in service life, cost, efficiency and power density, and has great significance and core propulsion undoubtedly for the large-scale industrialization process of the fuel cell.

The invention further provides a preferable preparation method of the silicon polar plate, wherein a conductive material layer is manufactured on the surface of the silicon chip, the conductive material layer is preferably made of base metal materials such as nickel, copper and the like, the conductive material layer is used as a mask layer structure in the subsequent corrosion process of the silicon chip, and simultaneously, two silicon chips are compositely connected and stacked into a whole transition bonding structure, the process is the simplest and most effective, the implementation is easy, the process cost is the lowest, and the method is suitable for batch manufacturing and application.

The invention further provides a preferable conductive material for composite connection between silicon wafers, and particularly provides a method for sintering a metal conductive material which has a eutectic bonding effect with a silicon material at a eutectic temperature to be used as a composite material for connecting the silicon wafers, so that the metal conductive material layer between the silicon wafers and the surface layer of the silicon wafer contacted with the metal conductive material layer are mutually fused and bonded, an integral silicon-metal conductive alloy composite structure with firm bonding is formed after cooling, and finally, the excellent composite connection effect between the silicon wafers is realized.

It should be noted that the silicon electrode plate provided by the invention has the excellent characteristics, so that the silicon electrode plate is particularly suitable for being applied to the field of non-miniature fuel cell products with a galvanic pile structure (especially non-miniature fuel cells with output power not lower than 0.1 KW), and has better performance advantages compared with a metal electrode plate, a graphite electrode plate or a composite material electrode plate in the prior art; of course, those skilled in the art can directly apply the silicon plate to the field of micro fuel cells (generally, only 1-2 fuel cell units) according to actual needs, which has some obvious technical advantages in material cost, preparation process, mechanical strength and cooling performance compared with the existing micro fuel cells using silicon as the plate substrate, and these should also fall within the protection scope of the present invention.

It should be noted that the expressions of the front and the back in the entire text of the present invention are only for explaining the position distribution relationship of various flow channels distributed on different surfaces of the silicon wafer, and the front and the back are relative, and the actual directions are different according to different references, which is not taken as the limitation of the present invention on the specific directions.

Drawings

FIG. 1 is a schematic cross-sectional view of a stack structure 100 in accordance with an embodiment of the present invention;

fig. 2 is a schematic sectional structure view of the middle

fuel cell units

100b, 100c, 100d and the end

fuel cell units

100a, 100e of example 1 of the invention;

FIG. 3 is a schematic cross-sectional view of the middle silicon plate 110 and the end silicon plates 130 and 130' in example 1 of the present invention;

FIG. 4 is a schematic structural diagram of a reducing agent passage 111 in a silicon plate 110 in the middle of example 1 of the present invention;

FIG. 5 is a flow chart of a process for preparing the silicon plate 110 in the middle of example 1;

FIG. 6 is a flow chart of a process for preparing a middle silicon plate 210 according to example 2 of the present invention;

FIG. 7 is a flow chart of a process for preparing a middle silicon plate 310 according to example 3 of the present invention;

FIG. 8 is a flow chart of a process for preparing a silicon plate 410 in the middle of example 4;

FIG. 9 is a schematic sectional view showing a fuel cell unit 10 of a micro fuel cell in example 5 of the invention;

fig. 10 is a schematic sectional view showing the structure of

fuel cells

20a, 20b of a micro fuel cell in example 6 of the invention.

Detailed Description

The embodiment of the invention discloses an application of silicon in a fuel cell, wherein the fuel cell comprises 1 or more fuel cell units; the fuel cell unit comprises an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode and a cathode plate which are sequentially stacked into a whole; wherein, the negative plate and the positive plate adopt silicon plates made of doped conductive crystalline silicon materials; the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Example 1:

referring to a fuel cell stack structure 100 shown in fig. 1, the stack structure 100 includes fuel cell units that are connected in series and stacked integrally with each other, and the number of the fuel cell units is not less than 3, specifically, in the present embodiment, the number of the fuel cell units is 5; preferably, the output power of the stack structure 100 is not lower than 0.1KW, however, in other embodiments of the present invention, the skilled person can select the number of fuel cell units according to the power requirement of the product field of the actual application, and the present invention is not limited to this.

As shown in fig. 1, the stack structure of the present embodiment 1 includes end

fuel cell units

100a, 100e at both ends and 3 middle

fuel cell units

100b, 100c, 100d in the middle, each fuel cell unit including an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode, and a cathode plate, which are stacked in sequence as a whole, the cathode plate and the anode plate being silicon plates made of a doped conductive crystalline silicon material, wherein the silicon plates serve as the cathode plate of a single fuel cell unit and the anode plate of a single fuel cell unit adjacent thereto at the same time;

preferably, in the embodiment, the doped conductive crystalline silicon material is a monocrystalline or polycrystalline doped silicon wafer; preferably, in this embodiment, the silicon wafer has a resistivity of not higher than 0.1 Ω · cm, more preferably, the silicon wafer has a resistivity in the range of 0.0005 to 0.05 Ω · cm;

it should be noted that, in the specific implementation of the present invention, the preparation method of the silicon plate may be selected according to the type of the crystal silicon to which the specifically selected silicon wafer belongs, which will be described in detail later herein.

Preferably, in the present embodiment, the silicon wafer has a thickness ranging from 0.2 to 5mm and a size ranging from 50 to 300 mm; the shape of the silicon wafer can be square, circular or other shapes as required, and the specific implementation of the invention is not limited specifically;

particularly preferably, in this embodiment, the silicon wafers used are N-type single crystal phosphorus-doped silicon wafers, which are square, and the crystal orientation is not a <111> crystal orientation, and specifically may be a <100> crystal orientation, a <110> crystal orientation, or another crystal orientation having an obvious angle with the <111> crystal orientation, which is beneficial to the subsequent alkali solution etching process adopted in this embodiment; the resistivity of the N-type single crystal phosphorus-doped silicon wafer is about 0.01 omega cm; the thickness of the silicon chip is 0.5mm, and the size is about 150 mm;

preferably, in the embodiment of the present invention, the silicon electrode plate has an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet and outlet assembly communicated therewith; preferably, the silicon plate specifically comprises 2 or more than 2 silicon wafers, wherein each silicon wafer is provided with a single-sided or double-sided flow channel; the surface areas of the silicon wafers, which do not cover the flow channels, are connected and stacked into a whole by adopting a conductive material in a composite mode, an internal flow channel located inside the silicon polar plate is formed through composite connection, and the internal flow channel is used as an internal cooling medium flow channel; the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel;

more specifically, preferably, in this embodiment 1, please further refer to fig. 2 and fig. 3, the middle fuel cell units 100b, 100c, and 100d include a middle silicon plate 110, the middle silicon plate 110 is formed by two silicon wafers through composite processing, and has an internal cooling medium channel 112, a front reducing agent channel 111, and a back oxidizing agent channel 113; and the internal cooling medium flow passage 112, the front reducing agent flow passage 111 and the back oxidant flow passage 113 are respectively provided with a silicon plate inlet and outlet combination (shown in fig. 4) communicated with them, specifically, the internal cooling medium flow passage 112, the front reducing agent flow passage 111 and the back oxidant flow passage 113, and the internal cooling medium flow passage, the front reducing agent flow passage 111 and the back oxidant flow passage 113 are respectively communicated with three groups of silicon plate inlet and outlet combinations, and at the same time, cooling medium, reducing agent and oxidant are respectively introduced into the inlets of the three groups of silicon plate inlet and outlet combinations, and the outlets of the three groups of silicon plate inlet and outlet combinations are respectively used for discharging the cooling medium, the redundant reducing agent and oxidant and reaction products thereof after passing through the respective flow passages;

in the practice of the present invention, the reducing agent can be hydrogen or natural gas or coal gas or purified gas or methanol, etc., and the oxidizing agent can be oxygen or air, and those skilled in the art can specifically select the type of the reducing agent and the type of the oxidizing agent according to the technical content of the present invention and the field of application; particularly preferably, in this embodiment, the reducing agent is hydrogen, the oxidizing agent is oxygen, the reaction product is water, the anode electrode, the electrolyte membrane and the cathode electrode adopt the MEA membrane electrode assembly 120, the electrolyte membrane is a proton exchange membrane, and the cooling medium is water, which is beneficial to the efficiency, the power density and the cost saving of the fuel cell stack structure provided by the present invention, and is easy to operate, apply and implement, and the reaction product in this embodiment is water, which does not generate any hazardous substance, and is very environment-friendly; the MEA membrane electrode assembly 120 and the proton exchange membrane of the present embodiment may directly adopt any one of the technical solutions in the prior art, and may be easily purchased in the market, and belong to the well-known technology with mature industrialization, and the detailed description of the part is not provided in the present invention;

in order to ensure the safety of the insulated installation of the fuel cell of this embodiment, a certain safe packaging edge distance is set between the MEA membrane electrode assembly 120 of each fuel cell unit and the two sides of the silicon plate thereof, and the distance is generally set to be in millimeter level, such as 5-15 mm; the safe packaging joint edge distance is used for subsequent insulating packaging.

As shown in fig. 4, in order to realize the uniqueness of the flow guidance between the inlet and outlet combinations and the corresponding flow channels, flow guide channels are disposed between the inlet and outlet combinations and the corresponding flow channels, and the flow guide channels and the flow channels can be prepared together in the preparation process, wherein the silicon plate inlet and outlet combination corresponding to the front reducing agent flow channel 111 includes an inlet 114a and an outlet 114a ' shown in fig. 4 (the silicon plate inlet and outlet combinations corresponding to the remaining flow channels are shown but not labeled, and the flow guide channels corresponding to the inlet 114a and the outlet 114a ' are an inlet flow guide channel 115a and an outlet flow guide channel 115a ', respectively;

the shape design of the specific flow channel, inlet and outlet on the middle silicon plate 110 in the embodiment of the present invention may refer to the design of fig. 4, or may adopt any one of the prior art, and the present invention is not particularly limited;

more specifically, referring to fig. 5 in a further combination manner, in the present embodiment, the middle silicon plate 110 includes a first middle silicon wafer and a second middle silicon wafer, wherein the first middle silicon wafer has a first internal cooling medium flow channel on the back side, a reducing agent flow channel on the front side 111, and a first inlet/outlet combination, and the second middle silicon wafer has a second internal cooling medium flow channel on the front side, an oxidizing agent flow channel on the back side 113, and a second inlet/outlet combination; the back side area of the first middle silicon wafer, which is not covered by the first internal cooling medium flow channel, and the front side area of the second middle silicon wafer, which is not covered by the second internal cooling medium flow channel, are compositely connected and stacked into a whole by adopting a conductive material, and the back side first internal cooling medium flow channel is correspondingly matched with the front side second internal cooling medium flow channel and forms an internal cooling medium flow channel 112 through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection. The specific flow channel structures and shapes of the back side first internal cooling medium flow channel, the front side second internal cooling medium flow channel and the back side oxidant flow channel 113 in this embodiment can be directly referred to the front side reductant flow channel 111 shown in fig. 4, and for the sake of brevity, the description will not be repeated;

preferably, in the embodiment of the present invention, the depth of the reducing agent channel 111 and the oxidizing agent channel 113 ranges from 50 to 300 micrometers, and the width ranges from 500 to 3000 micrometers; specifically, in the embodiment of the present invention, the depth of the reducing agent flow passage 111 and the oxidizing agent flow passage 113 is 100 ± 10 micrometers, and the width is 1000 ± 100 micrometers; the depth and width design schemes of the first internal cooling medium flow passage and the second internal cooling medium flow passage are the same as those of the reducing agent flow passage 111 and the oxidizing agent flow passage 113;

in this embodiment 1, please further refer to fig. 2 and fig. 3, the end fuel cell unit 100a includes an end silicon plate 130, an MEA membrane electrode assembly 120, and a middle silicon plate 110, and the end fuel cell unit 100e includes an end silicon plate 130', an MEA membrane electrode assembly 120, and a middle silicon plate 110, wherein the end silicon plate 130 is formed by two silicon wafers through composite processing, and has an internal cooling medium channel 131 and a reverse oxidant channel 132; and the internal cooling medium flow passage 131 and the back oxidant flow passage 132 are respectively provided with silicon electrode plate inlet and outlet combinations communicated with the internal cooling medium flow passage 131 and the back oxidant flow passage 132; the end silicon plate 130 'is formed by compounding and processing two silicon wafers and is provided with an internal cooling medium flow passage 131 and a front reducing agent flow passage 132'; and the internal cooling medium flow passage 131 and the front reducing agent flow passage 132 'are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage 131 and the front reducing agent flow passage 132'; the silicon plate inlet and outlet combination of the end silicon plates 130 and 130' of the present embodiment adopts the same technical scheme as the silicon plate inlet and outlet combination of the middle fuel cell units 100b, 100c, and 100d, and no explanation is specifically made;

more specifically, the end silicon plate 130 includes an end silicon wafer and a middle silicon wafer, wherein the end silicon wafer has a first internal cooling medium flow channel and a first inlet/outlet assembly on the back side, and the middle silicon wafer has a second internal cooling medium flow channel on the front side, a second oxidant flow channel 132 on the back side, and a second inlet/outlet assembly on the back side; the end silicon plate 130 'includes an end silicon wafer and a middle silicon wafer, respectively, wherein the end silicon wafer has a front first internal cooling medium channel and a first inlet/outlet assembly, and the middle silicon wafer has a back second internal cooling medium channel, a front reducing agent channel 132' and a second inlet/outlet assembly; the end silicon chip and the middle silicon chip are connected and stacked into a whole by adopting a conductive material in a composite mode, and the first internal cooling medium flow channel and the second internal cooling medium flow channel are correspondingly matched and are connected in a composite mode to form an internal cooling medium flow channel 131; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

In the embodiment of the present invention, according to the structural design characteristics of the middle silicon plate 110 and the end silicon plates 130 and 130 ', a person skilled in the art may use various process paths to prepare the middle silicon plate 110 and the end silicon plates 130 and 130' according to the embodiment of the present invention, and the typical method is as follows: processing a flow channel or an inlet-outlet combination on one side or two sides of a silicon wafer by adopting an etching process or a laser process or a screen printing process; and then adopting a conductive material to compositely connect and stack 2 or more than 2 silicon wafers into a whole, forming an internal flow channel positioned in the silicon polar plate through the composite connection, wherein the internal flow channel is used as an internal cooling medium flow channel of the silicon polar plate.

Because each

fuel cell unit

100a, 100b, 100c, 100d, 100e in the fuel cell stack structure 100 of the present invention is connected in series and stacked as a whole, the present invention stack structure realizes current collection and transmission in the stacking direction, and combination of silicon plate inlet and outlet through corresponding matching between each fuel cell unit in the stacking direction, and the internal cooling

medium flow passage

112, 131, the reducing agent flow passage 111,132' and the oxidizing agent flow passage 113,132 of each fuel cell unit are respectively communicated in the stacking direction;

in this embodiment, the thickness of the conductive material used for composite connection between the silicon wafers is in the micron order, and the conductive material may be a conductive metal material or a conductive non-metal material such as conductive adhesive; preferably, the conductive material is a metal conductive material; in order to facilitate good composite connection between metal conductive materials and between the metal conductive materials and silicon wafers, preferably, the conductive material of the embodiment is a metal conductive material having a eutectic bonding effect with a silicon material, that is, when the temperature is equal to or close to a eutectic temperature (the eutectic temperature is a temperature at which silicon and the corresponding metal conductive material perform a eutectic reaction), the metal conductive material and silicon can perform a good eutectic reaction, so that a metal conductive material layer between the silicon wafers and a silicon wafer surface layer in contact with the metal conductive material layer are fused and bonded with each other, and an integral silicon-metal conductive alloy composite structure with firm bonding is formed after cooling, so that an excellent composite connection effect between the silicon wafers is finally realized; particularly preferably, these metallic conductive materials may be in particular: nickel Ni, gold Au, silver Ag, copper Cu, aluminum Al and other materials; the eutectic temperature of silicon and these metal conductive materials is usually significantly lower than the melting temperature of silicon itself or the metal conductive materials themselves, and the eutectic temperature range is usually 500-1000 ℃, and the eutectic temperature with silicon can be determined according to the type of the metal conductive material actually used, and these can be obtained by referring to the related prior art information.

The expressions of the front side and the back side are presented only to illustrate the position distribution relationship that the various flow channels are distributed on different surfaces of the silicon wafer, the front side and the back side are relative, the actual direction is different according to different references, and the present embodiment is not limited to the specific direction.

Among these various process routes, the preferred preparation method is also provided in example 1 of the present invention, and the process is the simplest and most efficient, and easy to implement, and the process cost is the lowest, specifically as follows:

specifically, referring to fig. 5, embodiment 1 proposes a method for preparing the middle silicon plate 110, which includes the following steps:

A10) preparing a first silicon wafer and a second silicon wafer, wherein the silicon wafers are cleaned in advance, and further particularly preferably, the silicon wafers cut by diamond wires can be further subjected to chemical polishing or mechanical polishing to reduce the surface roughness, so that the process preparation effect of the subsequent steps is facilitated;

A20) the conductive material layer 116 is respectively manufactured on the two sides of the first silicon wafer and the second silicon wafer through a screen printing process, preferably, the thickness of the conductive material layer 116 is 1-15 micrometers, the conductive material is a base metal conductive material having a eutectic bonding effect with a silicon material, and since the flow channel is manufactured through an alkaline solution corrosion process in the embodiment, the conductive material in the embodiment 1 cannot react with the alkaline solution in selection, and certainly, in other embodiments of manufacturing the flow channel through a laser process or a screen printing process, the condition is not limited; in the present embodiment, the conductive material may be nickel or copper, specifically, the conductive material is nickel, and of course, in the present embodiment, as a less preferable solution in terms of cost, a noble metal conductive material may also be used, and other suitable conductive materials may also be used, which should not be construed as limiting the present invention;

A30) the conductive material layer 116 is simultaneously used as a mask layer, and a back-side first internal cooling medium runner and a front-side reducing agent runner 111 are respectively manufactured on the two sides of the first silicon wafer through an alkali solution (specifically, a KOH solution, a NaOH solution or a tetramethylammonium solution) corrosion process, and a front-side second internal cooling medium runner and a back-side oxidizing agent runner 113 are respectively manufactured on the two sides of the second silicon wafer;

A40) please refer to fig. 4, a first inlet-outlet combination and a second inlet-outlet combination are respectively manufactured on a first silicon chip and a second silicon chip by a laser process;

A50) the first silicon wafer and the second silicon wafer are stacked and then placed in heating equipment to be sintered at high temperature, so that in order to avoid the condition that the silicon wafers are oxidized in the sintering process and are not beneficial to composite connection, inert gas can be introduced into the heating equipment to realize an oxygen-free atmosphere; the heating temperature is selected to be close to or equal to the eutectic temperature of silicon and nickel, and the conductive material layers of the first silicon wafer and the second silicon wafer which are contacted with each other are fused and then are compositely connected and stacked into a whole (at the moment, the conductive material layers between the two silicon wafers and the silicon surface layers contacted with the conductive material layers are mutually fused and bonded, and after cooling, an integral silicon-metal alloy composite structure with firm bonding is formed, so that the composite effect is very excellent); the first internal cooling medium flow channel on the back side and the second internal cooling medium flow channel on the front side are correspondingly matched and form an internal cooling medium flow channel 112 through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

In other embodiments of the present invention, the above step a40) may be performed before step a30) or before step a 20);

specifically, this embodiment 1 proposes a method for preparing the end silicon plate 130 as described above, which includes the following steps:

a10'), preparing a first silicon wafer and a second silicon wafer;

a20'), respectively manufacturing a conductive material layer on the single side of the first silicon wafer and the double sides of the second silicon wafer by a screen printing process;

a30'), the conductive material layer is simultaneously used as a mask layer, a first internal cooling medium flow channel on the back side is respectively manufactured on the single side of the first silicon chip by an alkali solution corrosion process, and a second internal cooling medium flow channel on the front side and an oxidant flow channel 132 on the back side are respectively manufactured on the double sides of the second silicon chip;

a40'), respectively manufacturing a first inlet-outlet combination and a second inlet-outlet combination on a first silicon chip and a second silicon chip by adopting a laser process;

a50'), laminating the first silicon wafer and the second silicon wafer, then placing the laminated first silicon wafer and the laminated second silicon wafer into heating equipment to be sintered at high temperature, wherein the heating temperature is selected to be close to or equal to the eutectic temperature of silicon and nickel, and compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers of the first silicon wafer and the second silicon wafer which are contacted with each other are melted; the first internal cooling medium flow channel on the back side is correspondingly matched with the second internal cooling medium flow channel on the front side and forms an internal cooling medium flow channel through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

In other embodiments of the invention, the above step a40 ') may be performed before step a30 ') or before step a20 ');

the preparation method of the end portion silicon plate 130' in this embodiment 1 is the same as that of the end portion silicon plate 130, and is not described again; the preparation method of the end silicon plates 130 and 130' of the embodiment 1 is substantially the same as the preparation method and principle of the middle silicon plate 110, and the difference is only that: since the end silicon plates 130 and 130 'are located at the ends and are connected to the external mounting end plates without adjacent fuel cell units, the front reducing agent channels 132' are no longer required to be disposed on the end silicon wafers of the end silicon plates 130 ', and the back oxidizing agent channels 132 are no longer required to be disposed on the end silicon wafers of the end silicon plates 130', so that there is a slight difference in the manufacturing method as described above.

In other embodiments of the present invention, all or part of the middle silicon electrode plate, and all or part of the middle silicon electrode plate end silicon electrode plates may also be made of more than 2 silicon wafers, for example, 3 silicon wafers or 4 silicon wafers, so that the effective area of the cooling medium flow channel 112 may be increased, which is further beneficial to improving the heat dissipation effect of the fuel cell, but obviously, the application of a larger number of silicon wafers may cause the volume of the fuel cell stack structure to increase, which further causes the reduction of power density, and therefore, those skilled in the art may specifically select the number of silicon wafers according to the characteristics of the actually applied fuel cell product, and finally obtain the optimum balance point of various performance performances.

Preferably, this embodiment 1 further proposes a fuel cell, which includes a stack structure, an encapsulating insulator (not shown in the drawings), and an external mounting component (not shown in the drawings), where the encapsulating insulator is mainly used to implement insulating encapsulation of the stack structure, and then is connected and matched with the external mounting component, so as to facilitate final fuel cell installation and power output, where the stack structure employs the fuel cell stack structure 100 as described above; the package insulator and the external mounting device according to the embodiments of the present invention may be directly combined with any one of the package insulators and the external mounting devices in the prior art, and specifically, the package insulator may be various insulators such as rubber, hot melt adhesive, thermal crosslinking, and ultraviolet crosslinking.

Preferably, the present embodiment 1 also provides the fuel cell application as described above, and is applied to an automobile product, and of course, in other embodiments of the present invention, the present invention can also be applied to a portable product (such as various auxiliary power supply devices), or a stationary power supply or heat device product (such as a large cogeneration device or a continuous power supply device), or other types of transportation products (such as various vehicles like a logistics van).

Example 2:

the rest of the technical solutions of this embodiment 2 are the same as those of embodiment 1, except that: in this example 2, the silicon wafer is a phosphorus-doped or boron-doped single crystal or polycrystalline silicon wafer, and preferably, the silicon wafer has a resistivity in the range of 0.0005-0.05 Ω · cm; referring to fig. 6, the method for manufacturing the middle silicon plate 210 includes the following steps:

B10) preparing a first silicon chip and a second silicon chip;

B20) respectively manufacturing a back side first internal cooling medium flow channel, a front side reducing agent flow channel 211 and a first inlet-outlet combination on the two sides of a first silicon wafer through a laser process, and respectively manufacturing a front side second internal cooling medium flow channel, a back side oxidizing agent flow channel 213 and a second inlet-outlet combination on the two sides of a second silicon wafer;

B30) respectively manufacturing a conductive material layer 216 on the two sides of the first silicon wafer and the second silicon wafer by adopting a screen printing process;

B40) laminating the first silicon wafer and the second silicon wafer, then placing the laminated first silicon wafer and the laminated second silicon wafer into heating equipment for sintering at high temperature, and compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers 216 of the mutually contacted first silicon wafer and the second silicon wafer are melted; the first internal cooling medium flow channel on the back side and the second internal cooling medium flow channel on the front side are correspondingly matched and form an internal cooling medium flow channel 212 through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

As in example 1, the end silicon plate in this embodiment is different from the middle silicon plate 210 only in that the end silicon wafer does not need to be provided with a reducing agent flow passage or an oxidizing agent flow passage, so that those skilled in the art can refer to the preparation method of the middle silicon plate 210 and the structural features of the end silicon plate in this embodiment to set the preparation method of the end silicon plate, which do not need to pay creative labor, and therefore, the preparation method of the end silicon plate in this embodiment 2 is not described in detail.

Example 3:

the rest of the technical solutions of this embodiment 3 are the same as those of embodiment 1, except that: in this example 3, the silicon wafer is a phosphorus-doped or boron-doped single crystal or polycrystalline silicon wafer, preferably, the silicon wafer has a resistivity in the range of 0.0005-0.05 Ω · cm; referring to fig. 7, a method for manufacturing the middle silicon plate 310 includes the following steps:

C10) preparing a first silicon chip and a second silicon chip;

C20) respectively manufacturing a conductive material layer 316 on the two sides of a first silicon wafer and a second silicon wafer by directly adopting a screen printing process (also called a positive plastic process), and forming the conductive material layer 316 so that the first silicon wafer can directly form a first internal cooling medium flow channel on the back side and a front reducing agent flow channel 311, and the second silicon wafer can directly form a second internal cooling medium flow channel on the front side and an oxidant flow channel 313 on the back side;

C30) respectively manufacturing a first inlet-outlet combination and a second inlet-outlet combination on a first silicon chip and a second silicon chip by adopting a laser process; in other embodiments, step C30) may be performed before step C20);

C40) laminating the first silicon wafer and the second silicon wafer, then placing the laminated first silicon wafer and the laminated second silicon wafer into heating equipment, sintering the laminated first silicon wafer and the laminated second silicon wafer at high temperature, preferably setting the heating temperature to be the eutectic temperature of silicon and a conductive material, and compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers 316 of the first silicon wafer and the second silicon wafer which are contacted with each other are melted; the first internal cooling medium flow channel on the back side and the second internal cooling medium flow channel on the front side are correspondingly matched and form an internal cooling medium flow channel 312 through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

In order to facilitate that the structure and shape of the flow channel are not affected as much as possible during high-temperature sintering, in other embodiments of the present invention, the material used in the screen printing process in step C20) may also be a carbon paste material, and since the melting point of carbon is high, the shape of the flow channel can be effectively protected, but since carbon is not easy to cause eutectic reaction with silicon, in order to achieve effective high-temperature melt compounding between silicon wafers, a step of manufacturing a conductive material layer needs to be added before step C40), and the process may also employ a screen printing process or other processes to finally achieve high-temperature sintering melt compounding in step C40), and specifically, reference may be made to the steps of manufacturing the conductive material layer in examples 1-3, so that the flow channel is protected, and compound connection between the silicon wafers is achieved, but obviously, the manufacturing process also becomes relatively complex.

As in example 1, the end silicon plate in this embodiment is different from the middle silicon plate 310 only in that the end silicon wafer does not need to be provided with a reducing agent flow passage or an oxidizing agent flow passage, so that those skilled in the art can refer to the preparation method of the middle silicon plate 310 and the structural features of the end silicon plate in this embodiment to set the preparation method of the end silicon plate, which do not need to pay creative labor, and therefore, the preparation method of the end silicon plate is not described in detail in this embodiment 3.

Example 4:

the rest of the technical solutions of this embodiment 4 are the same as those of embodiment 1, except that: in this embodiment 4, please refer to fig. 8, the method for manufacturing the middle silicon plate 410 includes the following steps:

D10) preparing a first silicon chip and a second silicon chip;

D20) respectively manufacturing thermal oxidation silicon dioxide layers 414 on the two sides of the first silicon wafer and the second silicon wafer;

D30) designing the thermal oxidation silicon dioxide layer 414 into a mask layer by adopting a photoetching process or a laser process;

D40) respectively manufacturing a first inlet-outlet combination and a second inlet-outlet combination on a first silicon chip and a second silicon chip by adopting a laser process; in other embodiments, step D40) may be performed before step D30) or D20) or after step D50) or D60) or D70);

D50) respectively manufacturing a back first internal cooling medium channel and a front reducing agent channel 411 on the two sides of the first silicon wafer by adopting an alkali solution corrosion process, and respectively manufacturing a front second internal cooling medium channel and a back oxidant channel 413 on the two sides of the second silicon wafer;

D60) removing the residual silicon dioxide layers on the first silicon chip and the second silicon chip;

D70) respectively manufacturing a conductive material layer 416 on the two sides of the first silicon wafer and the second silicon wafer by adopting a screen printing process;

D80) laminating the first silicon wafer and the second silicon wafer, then placing the laminated first silicon wafer and the laminated second silicon wafer into heating equipment, sintering the laminated first silicon wafer and the laminated second silicon wafer at high temperature, preferably setting the heating temperature to be the eutectic temperature of silicon and a conductive material, and compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers 416 of the first silicon wafer and the second silicon wafer which are contacted with each other are melted; the first internal cooling medium flow channel on the back side is correspondingly matched with the second internal cooling medium flow channel on the front side and forms an internal cooling medium flow channel 412 through composite connection; the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form a silicon electrode plate inlet and outlet combination through composite connection.

As in example 1, the end silicon plate in this embodiment is different from the middle silicon plate 410 only in that the end silicon wafer does not need to be provided with a reducing agent flow passage or an oxidizing agent flow passage, so that those skilled in the art can refer to the preparation method of the middle silicon plate 410 and the structural features of the end silicon plate in this embodiment to set the preparation method of the end silicon plate, which do not need to pay creative labor, and therefore, the preparation method of the end silicon plate is not described in detail in this embodiment 4.

The present invention only lists the above embodiments, and those skilled in the art can select a specific preparation process and make sequence changes of some steps according to actual application requirements to obtain other embodiments, and these substitutions on the preparation process also belong to the protection scope of the present invention; since the specific preparation process steps (such as the etching process, the photolithography process, the laser process, and the screen printing process) provided by the present invention are all prior art, a person skilled in the art can select related technical parameters of the specific process steps according to actual situations, and the embodiments of the present invention are not specifically described.

It should be further noted that, in the manufacturing process flow diagrams shown in fig. 5 to fig. 8 in the embodiments of the present invention, the step diagrams before the composite connection of the two silicon wafers only show a single silicon wafer, because the step diagrams of the two silicon wafers are identical, and therefore, for the sake of brevity, only the step diagrams of the single silicon wafer are shown.

After a large number of embodiments, the invention proves that the silicon electrode plate is directly used as the silicon electrode plate of the fuel cell stack structure, and the good gas resistance function required by the fuel cell bipolar plate can be completely met; better heat-conducting property; lower bulk and contact resistance; the corrosion resistance is strong; the silicon polar plate has the characteristics of light weight, high strength, suitability for batch processing and the like, and has better advantages in service life, cost, efficiency and power density compared with a metal polar plate, a graphite polar plate or a composite material polar plate in the prior art; to better illustrate the excellent performance achieved by the embodiments of the present invention, please refer to the performance comparison of the fuel cell using the inventive silicon plate of table 1 with the important technical indexes of the existing various plate fuel cells:

TABLE 1

The performance of the important technical indexes of the silicon polar plate fuel cell of the invention is compared with that of the existing various polar plate fuel cells

Technical index	Graphite polar plate	Metal polar plate	Silicon polar plate
				Cost ($/kW)	300	400	250
Life (hours)	7000	5000	7000
				Volumetric power density (kW/L)	0.5-1.5	2-3.2	2-5
Gravimetric power density (kW/kg)	0.5-3	1.2-4	2-3.5

Supplementary further explanation:

1. with respect to cost:

firstly, silicon is the most abundant element in the earth, and with the development of integrated circuits and photovoltaic industries in which silicon materials are applied, the price of crystalline silicon materials is cheaper and cheaper, and as a polar plate of a fuel cell, silicon has lower cost than materials such as stainless steel and graphite, and has more space for reducing material cost;

furthermore, because the crystalline silicon has the characteristics of excellent fine processing (such as the etching process, the photoetching process, the laser process and the screen printing process mentioned in the invention), the depth and the width of the flow channels of the oxidant and the reducing agent can be greatly reduced, and further the stress on the electrolyte membrane, the cathode and the anode in the fuel cell stack structure is reduced, so that the fuel cell can adopt thinner electrode materials and dielectric membrane materials, the diffusion transport speed of the oxidant, the reducing agent and reaction products in the electrode is increased, and the diffusion length of ions in the dielectric membrane is reduced, so that the generated current of the fuel cell in unit area is increased, and the cost per watt of the electrolyte membrane, the cathode and the anode is indirectly and remarkably reduced;

2. with respect to lifetime:

because the crystalline silicon material has excellent chemical stability in acid-base and electrochemical environments, the defect that a metal polar plate fuel cell is not corrosion-resistant is avoided, therefore, the silicon polar plate can be used for a long time without failure, generally speaking, the service life of the applied silicon polar plate fuel cell is determined by other components, the service life data shown in the table 1 of the invention is based on the existing fuel cell data with long service life, and the service life of the silicon polar plate fuel cell can be prolonged along with the upgrading and optimization of the performances of other components; on the other hand, the long life of the silicon plate fuel cell further reduces the cost.

3. Regarding volumetric and gravimetric power densities:

the silicon plate fuel cell can generate higher current density, thereby increasing the volume power density of the electric pile structure:

because the crystalline silicon has the excellent characteristic of fine processing, a thin silicon electrode plate can be adopted to prepare a galvanic pile structure; for a stack structure in which the same number of single fuel cell units are stacked, the silicon plate stack structure has a minimum thickness; particularly, compared with a graphite electrode plate galvanic pile structure, the silicon electrode plate galvanic pile structure has particularly obvious advantages, so that the silicon electrode plate galvanic pile structure has the maximum volume power density;

silicon materials have a lower weight density than metal materials and are thinner than graphite materials, and thus silicon plate fuel cells have a higher weight power density.

The silicon plate fuel cell of the invention has high energy density which is even higher than that of a metal plate fuel cell, such as a metal plate fuel cell, and has excellent service life performance of a graphite plate fuel cell, and the silicon plate has the characteristics of low material cost and simple manufacturing process, so that the silicon plate fuel cell not only has lower cost than other material plate fuel cells, but also has obvious outstanding advantages in main technical indexes of the fuel cell such as durability, power density and the like. The technical effect breakthrough brought by the invention is beyond the imagination of ordinary technicians in the field of fuel cells, and the invention can not be obtained by obtaining any technical inspiration from the prior technical data. Therefore, the invention has no doubt great significance and core promotion effect on the mass industrialization process of the fuel cell.

As described above, the present invention can be applied to a fuel cell having a stack structure with a large number of fuel cell units, and can also be applied to a fuel cell (generally referred to as a micro fuel cell) including only 1 to 2 fuel cell units, specifically, see the following examples 5 and 6:

example 5:

the rest of the technical scheme of the embodiment 5 is the same as the embodiment 1, except that: in the present embodiment 5, referring to fig. 9, the fuel cell includes 1 fuel cell unit 10, including an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode, and a cathode plate, which are stacked in sequence; the cathode plate and the anode plate are both end silicon electrode plates made of doped conductive crystalline silicon materials, and the anode electrode, the electrolyte diaphragm and the cathode electrode are made of MEA (membrane electrode assembly) assemblies.

Example 6:

the rest of the technical solutions of this embodiment 6 are the same as those of embodiment 1, except that: in this embodiment 6, please refer to fig. 10, the fuel cell includes a first fuel cell unit 20a and a second fuel cell unit 20b connected in series and stacked as a whole, the first fuel cell unit 20a and the second fuel cell unit 20b respectively include an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode, and a cathode plate stacked as a whole in sequence, wherein the anode electrode, the electrolyte membrane, and the cathode electrode adopt MEA membrane electrode assemblies; the anode plate of the first fuel cell unit 20a and the cathode plate of the second fuel cell unit 20b both use end silicon plates made of doped conductive crystalline silicon material, and the cathode plate of the first fuel cell unit 20a uses a middle silicon plate made of doped conductive crystalline silicon material, which simultaneously serves as the anode plate of the second fuel cell unit 20 b.

The fuel cells proposed in embodiments 5 and 6 of the present invention are generally micro fuel cells with smaller output power, and compared to the existing micro fuel cells using silicon as a substrate of a polar plate, in embodiments 5 and 6, an additional metal film layer is not required to be provided as a conductive layer, so that the performance in terms of material cost and preparation process is more excellent, and in embodiments 5 and 6, two silicon wafers are used to composite-fabricate a silicon polar plate with an internal flow channel, the silicon polar plate is used as a skeleton structure of the fuel cell, the mechanical strength is good, and the internal flow channel can be directly used as a cooling medium flow channel, so that the cooling performance of the micro fuel cell is further improved, and the defect that the micro fuel cell using silicon as a substrate in the prior art cannot be cooled is overcome.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. Use of silicon in a fuel cell, wherein the fuel cell comprises a plurality of fuel cell units; the fuel cell unit comprises an anode plate, an anode electrode, an electrolyte membrane, a cathode electrode and a cathode plate which are sequentially stacked into a whole; wherein the content of the first and second substances,

the negative plate and the positive plate are silicon plates made of doped conductive crystalline silicon materials; the doped conductive crystalline silicon material adopts a monocrystalline or polycrystalline doped silicon wafer, and the resistivity of the doped conductive crystalline silicon material is not higher than 0.1 omega.cm;

the silicon electrode plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and/or a back oxidizing agent flow passage, and the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage are respectively provided with a silicon electrode plate inlet-outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and/or the back oxidizing agent flow passage;

the silicon polar plate comprises more than 2 silicon wafers, the crystal orientation of the silicon wafers is not the <111> crystal orientation, and the silicon wafers are provided with single-sided or double-sided runners; respectively manufacturing a conductive material layer on two sides of a silicon wafer, wherein the conductive material layer is a metal conductive material with a eutectic bonding effect with a silicon material, the conductive material layer is simultaneously used as a mask layer, and then processing a flow channel on one side or two sides of the silicon wafer by adopting an alkali solution corrosion process; stacking more than 2 silicon wafers, compositely connecting and stacking the silicon wafers into a whole after the conductive material layers of the silicon wafers which are mutually contacted are melted, and forming an internal flow channel positioned in the silicon pole plate through the composite connection, wherein the internal flow channel is used as an internal cooling medium flow channel of the silicon pole plate; and the flow channel positioned on the non-stacking surface of the silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel.

2. The use of silicon in a fuel cell according to claim 1, wherein the silicon plates simultaneously serve as cathode plates for a single fuel cell unit and anode plates for a single fuel cell unit adjacent thereto.

3. The use of silicon according to claim 1 or 2 in a fuel cell, wherein the fuel cell comprises a stack structure comprising end fuel cell units at both ends and 1 or more middle fuel cell units at the middle, which are connected in series with each other and stacked integrally, wherein,

the middle fuel cell unit comprises a middle silicon polar plate, wherein the middle silicon polar plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage and a back oxidizing agent flow passage; and the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage and the back oxidant flow passage.

4. Use of silicon in a fuel cell according to claim 3, wherein the end fuel cell units comprise end silicon plates and the central silicon plate; wherein the content of the first and second substances,

the end silicon polar plate is provided with an internal cooling medium flow passage, a front reducing agent flow passage or a back oxidizing agent flow passage; and the internal cooling medium flow passage, the front reducing agent flow passage or the back oxidant flow passage are respectively provided with a silicon electrode plate inlet and outlet combination communicated with the internal cooling medium flow passage, the front reducing agent flow passage or the back oxidant flow passage.

5. The use of silicon in a fuel cell according to claim 3, wherein said central silicon plate comprises a first central silicon slice and a second central silicon slice,

the first middle silicon wafer is provided with a first internal cooling medium flow passage on the back side, a reducing agent flow passage on the front side and a first inlet-outlet combination, and the second middle silicon wafer is provided with a second internal cooling medium flow passage on the front side, an oxidizing agent flow passage on the back side and a second inlet-outlet combination;

respectively manufacturing a conductive material layer on the two sides of the first middle silicon wafer and the second middle silicon wafer, wherein the conductive material layer is simultaneously used as a mask layer, and then respectively manufacturing a back-side first internal cooling medium flow channel and a front-side reducing agent flow channel on the two sides of the first middle silicon wafer by adopting an alkali solution corrosion process, and respectively manufacturing a front-side second internal cooling medium flow channel and a back-side oxidizing agent flow channel on the two sides of the second middle silicon wafer;

then stacking the first middle silicon wafer and the second middle silicon wafer, compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers of the first middle silicon wafer and the second middle silicon wafer which are mutually contacted are melted, and forming an internal cooling medium channel by correspondingly matching the first internal cooling medium channel on the back side with the second internal cooling medium channel on the front side through composite connection; a flow channel positioned on the non-stacking surface of the first middle silicon wafer and the second middle silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel; and the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form the silicon electrode plate inlet and outlet combination through the composite connection.

6. The use of silicon in a fuel cell according to claim 4, wherein said end silicon plates comprise end silicon pieces and middle silicon pieces,

the end silicon wafer is provided with a front side or back side first internal cooling medium flow passage and a first inlet-outlet combination, and the middle silicon wafer is provided with a back side or front side second internal cooling medium flow passage, a front side reducing agent flow passage or a back side oxidizing agent flow passage and a second inlet-outlet combination;

respectively manufacturing a conductive material layer on a single surface of the end silicon wafer and two surfaces of the middle silicon wafer of the end silicon polar plate, wherein the conductive material layers are simultaneously used as mask layers, then respectively manufacturing a first internal cooling medium flow passage on the back surface on the single surface of the end silicon wafer by adopting an alkali solution corrosion process, and respectively manufacturing a second internal cooling medium flow passage on the front surface and one of an oxidant flow passage or a reductant flow passage on the back surface on the two surfaces of the middle silicon wafer; then, stacking the end silicon wafer and the middle silicon wafer, compositely connecting and stacking the two silicon wafers into a whole after the conductive material layers of the end silicon wafer and the middle silicon wafer which are mutually contacted are melted, and forming an internal cooling medium channel by correspondingly matching a first internal cooling medium channel on the back side with a second internal cooling medium channel on the front side through composite connection; a flow channel positioned on the non-stacking surface of the middle silicon wafer is used as a reducing agent flow channel or an oxidizing agent flow channel; and the first inlet and outlet combination and the second inlet and outlet combination are respectively matched correspondingly and form the silicon electrode plate inlet and outlet combination through the composite connection.

7. Use of silicon as claimed in claim 1 or 5 or 6 in fuel cells, wherein the silicon wafer has a thickness in the range of 0.2 to 5 mm.