A miniature, purely passive direct methanol fuel cell and its operating method

Abstract

This disclosure relates to the field of fuel cell technology, and proposes a miniature pure passive direct methanol fuel cell and its operating method. The fuel cell includes an anode end plate, a uniformly distributed porous plate, a methanol permeate evaporation membrane, an anode current collector, a membrane electrode assembly (MEA), and a cathode current collector connected in sequence. A liquid storage chamber is provided within the anode end plate for storing pure methanol fuel. A proton exchange membrane is disposed in the middle of the MEA. An anode catalyst layer and an anode diffusion layer are sequentially disposed on the anode side of the MEA, and a cathode catalyst layer and a cathode diffusion layer are sequentially disposed on the cathode side of the MEA. A microporous water-retaining layer is disposed on the side of the cathode diffusion layer closest to the cathode catalyst layer. Through improvements to the anode and cathode structures, a purely passive fuel supply can be achieved through self-breathing on both the anode and cathode sides, thus enabling normal operation of the battery without the need for auxiliary equipment and achieving miniaturization of the battery.

Description

Technical Field

[0001] This disclosure relates to the field of fuel cell technology, specifically to a micro-sized, purely passive direct methanol fuel cell and its operating method. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] The rapid proliferation of microelectronic devices has accelerated the urgent demand for micro batteries. Micro fuel cells have high specific energy and energy conversion efficiency, enabling fuel cells to be miniaturized and providing a more reliable power supply for various miniaturized electronic devices.

[0004] Direct methanol fuel cells (DFCs), as a green energy device, use methanol as fuel. Methanol is stable and extremely safe, with a theoretical energy density as high as 4780 Wh / L, exhibiting exceptional safety and reliability. Currently, DFCs are used as power sources in small portable devices. These devices require DFCs with output power in the tens or even hundreds of watts range, necessitating the use of a low-concentration methanol aqueous solution as the anode-side fuel supply (approximately 3–5 wt%) to reduce performance degradation caused by methanol permeation. Furthermore, the relatively fast electrochemical reaction rate necessitates the transport of reactants (methanol solution and air) and the emission of reaction byproducts (water and carbon dioxide), requiring auxiliary equipment such as water pumps and fans. This results in complex structures and large volumes, making it difficult to adapt such small DFCs for miniaturized electronic devices.

[0005] The inventors discovered in their research that current small batteries require auxiliary equipment, and it is impossible to directly miniaturize them according to the battery structure of small batteries, such as to achieve the size of a button cell. This presents significant technical challenges and limits the application prospects of methanol fuel cells as a new type of micro-energy. Summary of the Invention

[0006] To address the aforementioned issues, this disclosure proposes a miniature, purely passive direct methanol fuel cell and its operating method. Through improvements to the cathode and anode structures, a purely passive fuel supply can be achieved through self-breathing on both sides of the cathode and anode, thus enabling the battery to operate normally without the need for auxiliary equipment and realizing the miniaturization of the battery.

[0007] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0008] One or more embodiments provide a micro-sized, purely passive, direct methanol fuel cell, comprising an anode end plate, a uniformly distributed porous plate, a methanol permeate evaporation membrane, an anode current collector, a membrane electrode assembly (MEA), and a cathode current collector connected in sequence.

[0009] A liquid storage chamber is provided inside the anode plate for storing pure methanol fuel;

[0010] A proton exchange membrane is disposed in the middle of the membrane electrode (MEA). An anode catalytic layer and an anode diffusion layer are disposed sequentially on the anode side of the proton exchange membrane, and a cathode catalytic layer and a cathode diffusion layer are disposed sequentially on the cathode side of the proton exchange membrane. A microporous water-retaining layer is disposed on the side of the cathode diffusion layer closest to the cathode catalytic layer.

[0011] The above-described method for operating a micro-passive direct methanol fuel cell includes an anode self-breathing process and a cathode self-breathing process, wherein the anode self-breathing provides fuel, and the process is as follows:

[0012] The pure methanol supplied from the anode side of the battery is evenly distributed on a porous plate within the storage chamber.

[0013] Methanol on a uniformly distributed porous plate diffuses through a permeate evaporation membrane under the action of a gradient and then vaporizes to obtain methanol vapor.

[0014] Methanol vapor diffuses through the gas diffusion holes on the anode current collector to the surface of the anode diffusion layer of the membrane electrode (MEA), and then diffuses to the anode catalyst layer to undergo the anode reaction.

[0015] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0016] In this disclosure, the fuel cell performs a methanol anode reaction in the anode catalyst layer and a cathode electrochemical reaction in the cathode catalyst layer. The water required for the anode reaction in this embodiment comes from the water generated in the cathode reaction. Through the proton exchange membrane and the cathode diffusion layer with a water-retaining layer, a water concentration diffusion gradient is constructed on both sides of the proton exchange membrane to allow water to "flow back" to the anode, providing the water required for the methanol anode reaction, ensuring the smooth progress of the reaction, realizing the supply of water during the reaction process, and achieving efficient utilization of water.

[0017] The advantages of this disclosure, as well as its additional advantages, will be described in detail in the following specific embodiments. Attached Figure Description

[0018] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute a limitation thereof.

[0019] Figure 1 This is a schematic diagram of the battery structure of Embodiment 1 of this disclosure;

[0020] Figure 2 This is a schematic diagram of the working principle of the methanol battery according to Embodiment 1 of this disclosure;

[0021] Figure 3 This is a schematic diagram of the overall structure of the assembled battery according to Embodiment 1 of this disclosure;

[0022] The components are: 1. Methanol filling port, 2. Anode end plate, 3. Liquid storage chamber, 4. Evenly distributed perforated plate, 5. Gasket, 6. Methanol permeate evaporation membrane, 7. Anode current collector, 8. Anode side sealing ring, 9. Membrane electrode (MEA), 10. Cathode current collector, 11. Fixing hole, 12. Bolt, 13. Negative terminal, 14. Positive terminal.

[0023] 31. Guide groove; 91. Proton exchange membrane; 92. Anode catalyst layer; 93. Anode diffusion layer; 94. Cathode catalyst layer; 95. Cathode diffusion layer. Detailed Implementation

[0024] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0026] It should be noted that the terminology used herein is for descriptive purposes only and is not intended to limit the exemplary embodiments according to this disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. It should be noted that, without conflict, the various embodiments and features within those embodiments can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0027] Example 1

[0028] In one or more of the technical solutions disclosed in the embodiments, such as Figures 1 to 3 As shown, a micro-sized passive direct methanol fuel cell includes: an anode end plate 2, a uniformly distributed porous plate 4, a methanol permeate evaporation membrane 6, an anode current collector 7, a membrane electrode assembly (MEA) 9, and a cathode current collector 10 connected in sequence.

[0029] A liquid storage chamber 3 is provided inside the anode plate 2, and a perforated plate 4 is evenly distributed inside the liquid storage chamber 3 for storing pure methanol fuel.

[0030] A proton exchange membrane 91 is disposed in the middle of the membrane electrode MEA9. An anode catalyst layer 92 and an anode diffusion layer 93 are disposed sequentially on the anode side of the proton exchange membrane 91. A cathode catalyst layer 94 and a cathode diffusion layer 95 are disposed sequentially on the cathode side of the proton exchange membrane 91. A microporous water-retaining layer is disposed on the side of the cathode diffusion layer 95 near the cathode catalyst layer.

[0031] In this embodiment, the fuel cell performs a methanol anode reaction in the anode catalyst layer 92 and a cathode electrochemical reaction in the cathode catalyst layer 94. The water required for the anode reaction in this embodiment comes from the water generated in the cathode reaction. Through the proton exchange membrane 91 and the cathode diffusion layer 95 with a water-retaining layer, a water concentration diffusion gradient is constructed on both sides of the proton exchange membrane 91 to allow water to "flow back" to the anode, providing the water required for the methanol anode reaction, ensuring the smooth progress of the reaction, realizing the supply of water during the reaction process, and achieving efficient water utilization.

[0032] In some embodiments, the built-in liquid storage cavity 3 of the anode plate 2 is a slot provided on the plate surface of the anode plate 2; the shape of the slot can be any shape, such as polygon, circle, etc.

[0033] Optionally, the male end plate 2 can be manufactured by machining, and a slot of a set shape can be directly milled on the end plate surface with thickness.

[0034] In this embodiment, the liquid storage cavity 3 is a circular cavity, and radially radiating guide grooves 31 are uniformly arranged from the center to the edge of the circular cavity. The arrangement of the guide grooves 31 is conducive to the uniform distribution of liquid in the liquid storage cavity 3, thereby facilitating the uniform diffusion and transmission of fuel liquid to the next layer of structure.

[0035] Furthermore, the width of the guide groove 31 increases sequentially from the center position to the edge.

[0036] To facilitate fuel refueling, a methanol refueling port 1 is provided on the side of the anode plate 2, through which pure methanol fuel can be directly refueled.

[0037] In some embodiments, the uniformly distributed porous plate 4 may adopt a three-dimensional multi-layer mesh structure, such as a sponge-like or honeycomb-like multi-layer mesh structure.

[0038] The size of the uniformly distributed porous plate 4 is adapted to the size of the liquid storage cavity 3 so that the uniformly distributed porous plate 4 can fit inside the liquid storage cavity 3.

[0039] Furthermore, in order to achieve a sealed connection between the uniformly distributed porous plate 4, the anode end plate 2, and the pervaporation membrane 6, an annular rubber gasket 5 is provided between the anode end plate 2 and the pervaporation membrane 6. The inner diameter of the rubber gasket 5 is adapted to the size of the uniformly distributed porous plate 4, so that the uniformly distributed porous plate 4 can be fixedly pressed into the liquid storage chamber 3.

[0040] In some embodiments, the pervaporation membrane 6 may be an organic polymer membrane, which can slowly release methanol vapor to provide fuel for the anode through the permeation and diffusion rate of methanol molecules through the membrane.

[0041] In this embodiment, the pure methanol in the storage chamber 3 is uniformly absorbed by the evenly distributed porous plate 4, and then absorbed by the permeate evaporation membrane 6 and evaporated. The methanol vapor is then uniformly diffused through the anode diffusion layer 93 of the membrane electrode MEA9 to the anode catalyst layer 92 for reaction.

[0042] In some embodiments, the anode current collector 7 is provided with gas diffusion holes and a positive terminal 14.

[0043] Optionally, the gas diffusion holes provided in the anode current collector 7 can be equidistant circular through holes provided on concentric rings at equal intervals on the surface of the anode current collector 7, serving as channels for gas autonomous diffusion to achieve gas diffusion.

[0044] Optionally, the anode current collector 7 can be made of millimeter-sized pure stainless steel or conductive material with a coating of precious metals such as gold or platinum.

[0045] In this embodiment, equidistant circular through holes are provided on the concentric rings with equal spacing on the plate surface. The advantage of this arrangement is that it facilitates the uniform distribution of reactants and reduces concentration polarization.

[0046] Furthermore, an anode-side sealing ring 8 is provided on the anode current collector 7 and is located on the side opposite to the membrane electrode MEA9.

[0047] The anode-side sealing ring 8 creates a certain gap between the anode current collector 7 and the membrane electrode MEA9, which can serve as a gas containment space to ensure the balance of internal and external pressures.

[0048] In some embodiments, the membrane electrode MEA9 is an ultrathin proton exchange membrane 91 with a thickness that can be set to 8–30 μm.

[0049] Optionally, an ultra-thin proton exchange membrane 91 is used, specifically a proton exchange membrane with high ion exchange capacity to ensure the membrane's proton conduction capability.

[0050] Among them, the anode catalyst layer 92 and the cathode catalyst layer 94 of the membrane electrode MEA9 can be made of carbon nanomaterials with high specific surface area carbon supported by platinum and ruthenium and platinum noble metals, respectively, to ensure that the catalyst layer has more reaction sites and has a high electrochemical active area.

[0051] Both the anode diffusion layer 93 and the cathode diffusion layer 95 of the membrane electrode MEA9 can be made of carbon paper.

[0052] A further technical solution involves setting a microporous water-retaining layer on the outer side of the cathode diffusion layer 95. Specifically, a microporous layer is set on the surface of the carbon paper layer of the cathode. The method of setting is as follows: carbon powder and binder are mixed in an organic solution and sprayed onto the carbon paper that serves as the cathode diffusion layer 95 to form a microporous structure. That is, the microporous water-retaining layer is a carbon powder layer.

[0053] In some embodiments, the cathode current collector 10 is provided with gas diffusion holes and negative terminal 13.

[0054] Optionally, the gas diffusion holes provided in the cathode current collector 10 can be equidistant circular through holes provided on concentric rings at equal intervals on the surface of the cathode current collector 10, serving as channels for gas autonomous diffusion and realizing gas diffusion.

[0055] Optionally, the cathode current collector 10 is made of a current-collecting conductive material, specifically millimeter-level pure stainless steel or a conductive material with a coating of precious metals such as gold or platinum.

[0056] The assembly of the aforementioned battery involves first placing the anode end plate 2 inside a methanol storage chamber and then placing a uniformly distributed porous plate 4 inside. Next, a leak-proof sealing gasket 5, a permeate evaporation membrane 6, an anode current collector 7, an anode-side sealing ring 8, a membrane electrode assembly (MEA) 9, and a cathode current collector 10 are placed sequentially. These components are then assembled together using bolts 12 and fixed with holes 11 to form a micro fuel cell device. Figure 3 The figure shown is the overall assembly diagram of this embodiment. The overall assembly of this embodiment is fixed by tightening the bolts 12 around the perimeter with a certain force to prevent leakage and excessive contact resistance.

[0057] The battery structure of this embodiment enables the miniaturization of the methanol fuel cell, achieving a self-breathing supply of oxygen and methanol without the need for external auxiliary equipment. This results in a small methanol fuel cell size, reducing fuel cell volume and eliminating the system's own power consumption.

[0058] Example 2

[0059] Based on Example 1, this embodiment provides a method for operating a micro-sized, purely passive, direct methanol fuel cell, including an anode self-breathing process and a cathode self-breathing process, wherein the anode self-breathing provides fuel, and the process is as follows:

[0060] Step A1: Distribute the pure methanol supplied from the anode side of the battery evenly on the evenly distributed porous plate 4 in the storage chamber 3.

[0061] Step A2: Methanol on the uniformly distributed porous plate 4 diffuses through the permeate evaporation membrane 6 under the action of gradient and then vaporizes to obtain methanol vapor.

[0062] Step A3: Methanol vapor diffuses through the gas diffusion holes on the anode current collector 7 to the surface of the anode diffusion layer 93 of the membrane electrode MEA9, and then diffuses to the anode catalyst layer 92 for the anode reaction to occur;

[0063] Specifically, the battery anode side is supplied with 100% methanol as fuel. The pure methanol fuel required for the anode enters the methanol storage chamber 3 built into the anode end plate 2 through the methanol filling port 1. A methanol uniformly distributed porous plate 4 is placed at the opening of the methanol storage chamber 3 to distribute the methanol. The methanol on the uniformly distributed porous plate 4 is vaporized after passing through the permeate evaporation membrane 6, and diffuses directly to the surface of the anode diffusion layer 93 of the membrane electrode MEA9 through the through holes on the anode current collector, and then reaches the anode catalyst layer 92 to undergo the anode reaction.

[0064] In this embodiment, the methanol pervaporation rate is controlled on the anode side through the combined action of the methanol-distributed porous plate 4 and the pervaporation membrane 6. Pure methanol enters the storage chamber 3 through the filling port 1 and is stored in the sponge-like porous methanol distribution plate. The pure methanol on the distribution plate first permeates and dissolves on the surface of the pervaporation membrane 6, thereby controlling the rate at which pure methanol permeates into the pervaporation membrane 6. Under the influence of a gradient, it diffuses through the membrane and finally evaporates on the other side of the pervaporation membrane 6. The pervaporation membrane 6, with its specific methanol diffusion rate, ensures the slow release of methanol vapor on the anode side to provide fuel, effectively improving fuel utilization. The anode can achieve self-fuel supply without external auxiliary equipment.

[0065] The cathode provides moisture and oxygen through self-respiration, including the following steps:

[0066] Step B1: Oxygen passes through the gas diffusion holes on the cathode-side current collector 10 to the cathode diffusion layer 95 on the membrane electrode MEA9.

[0067] Step B2: Oxygen passes through the cathode diffusion layer 95 to the porous cathode catalyst layer 94, completing the electrochemical reaction. The water generated in the reaction diffuses towards the anode catalyst layer 92 under the action of the water-retaining layer, forming a gradient for the anode reaction.

[0068] The reaction equation for a direct methanol fuel cell is:

[0069] Anode: CH3OH + H2O → CO2 + 6H + +6e -

[0070] Cathode: 1.5O2 + 6e - +6H + →3H2O

[0071] The overall reaction of the battery is: CH3OH + 1.5O2 → 2H2O + CO2

[0072] Specifically, the battery cathode is connected to the air, and the oxygen required for the reaction comes from the air. The oxygen reaches the cathode diffusion layer 95 through the cathode current collector 10, which is made of conductive material. The machined equidistant circular through-holes distributed on the concentric equidistant rings on the current collector 10 are channels for the autonomous diffusion of oxygen. Through the circular through-holes, the oxygen reaches the cathode diffusion layer 95, which covers the channels of the cathode current collector 10, thus ensuring the uniformity of oxygen concentration distribution on the cathode diffusion layer 95 and reducing cathode polarization. Finally, the oxygen reaches the porous cathode catalyst layer 94 through the diffusion layer to complete the electrochemical reaction at the reaction site. Based on the above self-breathing feeding method of the anode and cathode fuel, the liquid and gas feeding can be achieved without an external power source, realizing the miniaturization of the passive direct methanol fuel cell power generation device.

[0073] In this embodiment, the water required for the methanol anode reaction comes from the water generated by the cathode reaction. A water concentration diffusion gradient is constructed on both sides of the ultrathin proton exchange membrane 91 to allow water to "flow back" to the anode, providing the water required for the reaction and ensuring its smooth progress.

[0074] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

[0075] While the specific embodiments of this disclosure have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of this disclosure. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this disclosure are still within the scope of protection of this disclosure.

Claims

1. A miniature, purely passive, direct methanol fuel cell, characterized in that: It includes a positive end plate, a uniformly distributed porous plate, a methanol permeation evaporation membrane, an anode current collector, a membrane electrode assembly (MEA), and a cathode current collector connected in sequence. A liquid storage chamber is provided inside the anode plate for storing pure methanol fuel; The uniformly distributed perforated plate adopts a three-dimensional multi-layer mesh structure; A proton exchange membrane is disposed in the middle of the membrane electrode MEA. An anode catalytic layer and an anode diffusion layer are disposed sequentially on the anode side of the proton exchange membrane, and a cathode catalytic layer and a cathode diffusion layer are disposed sequentially on the cathode side of the proton exchange membrane. A microporous water-retaining layer is disposed on the side of the cathode diffusion layer close to the cathode catalytic layer. Among them, a water-retaining layer with a microporous structure is set on the outside of the cathode diffusion layer. The method of setting is to mix carbon powder and binder in an organic solution and spray it onto the carbon paper that serves as the cathode diffusion layer to form a microporous structure.

2. The micro-passive direct methanol fuel cell as described in claim 1, characterized in that: A uniformly distributed perforated plate is placed inside the liquid storage chamber.

3. A miniature, purely passive, direct methanol fuel cell as described in claim 2, characterized in that: The uniformly distributed porous plate adopts a multi-layered mesh structure that resembles a sponge or a honeycomb.

4. A miniature, purely passive, direct methanol fuel cell as described in claim 1, characterized in that: Both the anode diffusion layer and the cathode diffusion layer of the membrane electrode (MEA) are made of carbon paper.

5. A miniature, purely passive, direct methanol fuel cell as described in claim 1, characterized in that: A ring-shaped rubber pad is also provided between the anode end plate and the pervaporation membrane. The inner diameter of the rubber pad is adapted to the size of the uniformly distributed porous plate, which is used to fix and press the uniformly distributed porous plate into the liquid storage cavity.

6. A miniature, purely passive, direct methanol fuel cell as described in claim 1, characterized in that: The anode current collector is equipped with gas diffusion holes and positive terminal blocks; The gas diffusion holes in the anode current collector are equidistant circular through holes set on concentric rings with equal spacing on the surface of the anode current collector. Alternatively, the cathode current collector is provided with gas diffusion holes and negative terminal blocks; The gas diffusion holes in the cathode current collector are equidistant circular through holes set on concentric rings with equal spacing on the surface of the cathode current collector.

7. A miniature, purely passive, direct methanol fuel cell as described in claim 1, characterized in that: An anode-side sealing ring is provided on the anode current collector and is located on the side opposite to the membrane electrode MEA9.

8. A method for operating a micro-sized, purely passive, direct methanol fuel cell according to any one of claims 1-7, characterized in that, This includes both anode self-breathing and cathode self-breathing processes. Anode self-breathing provides fuel, and the process is as follows: The pure methanol supplied from the anode side of the battery is evenly distributed on a porous plate within the storage chamber. Methanol on a uniformly distributed porous plate diffuses through a permeate evaporation membrane under the action of a gradient and then vaporizes to obtain methanol vapor. Methanol vapor diffuses through the gas diffusion holes on the anode current collector to the surface of the anode diffusion layer of the membrane electrode (MEA), and then diffuses to the anode catalyst layer to undergo the anode reaction.

9. The working method as described in claim 8, characterized in that: The cathode provides moisture and oxygen through self-respiration, including the following processes: Oxygen diffuses through the gas diffusion holes on the cathode-side current collector to the cathode diffusion layer on the membrane electrode (MEA); Oxygen passes through the cathode diffusion layer to the porous cathode catalyst layer, where it completes the electrochemical reaction. The water generated in the reaction diffuses into the anode catalyst layer in a gradient under the action of the water-retaining layer, and is used to carry out the anode reaction.

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