Totally-enclosed electrochemical device and control method

Abstract

This invention belongs to the field of electrochemical technology, specifically relating to a fully enclosed electrochemical device and its control method. The fully enclosed electrochemical device includes: a sealed housing, comprising a cathode bottom cover with cathode vent holes and an anode top cover with hydrophobic vent holes; a membrane electrode assembly fixed within an internal cavity, the edges of which are enclosed in a surrounding seal by insulating encapsulation ribs; the membrane electrode assembly comprises a cathode, a diaphragm, and an anode stacked sequentially, forming a tightly fitted structure with zero gaps. This invention uses insulating encapsulation ribs to surround and seal the zero-gap membrane electrode assembly, combined with a vent structure featuring a hydrophobic and breathable membrane. This macroscopically purely physical "fully enclosed" encapsulation design cuts off the macroscopic channels for electrolyte leakage, enabling the electrochemical device to adapt to extreme conditions such as tilting, inversion, and even microgravity, greatly expanding the application boundaries of deoxygenation / oxygenation equipment in aerospace and portable medical fields.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a fully enclosed electrochemical device and its control method. Background Technology

[0002] Electrochemical deoxygenation and oxygen generation technologies have extremely important application value in fields such as life support in confined spaces, aerospace, biochemical corrosion prevention, and portable medical devices. The core of these technologies lies in utilizing gas diffusion electrodes and membrane electrode assemblies to construct a stable gas-liquid-solid three-phase interface, thereby efficiently driving the reduction (deoxygenation) or evolution (oxygen generation) reaction of oxygen.

[0003] However, in the process of realizing this application, it was discovered that as application scenarios develop towards all-space orientation placement, extreme environment adaptation, and equipment miniaturization, existing electrochemical deoxygenation or oxygen generation devices have exposed many insurmountable technical bottlenecks, specifically in the following aspects:

[0004] First, the existing open-cavity structure severely restricts the device's orientation and poses a risk of physical leakage. Most conventional electrochemical devices employ open or semi-open electrolyte storage chambers, relying primarily on gravity to achieve gas-liquid separation and maintain the electrolyte's physical position. This structure necessitates maintaining a specific upright operating posture. If the device overturns, is inverted, or subjected to severe vibration or microgravity, the electrolyte is highly susceptible to physical leakage through vents or assembly gaps. This not only leads to device failure, but the leaked strong alkaline or acidic electrolyte can also corrode surrounding precision equipment, severely limiting its ability to operate in all orientations.

[0005] Second, conventional cathode layer arrangements are prone to microscopic capillary siphoning and flooding failure. Regarding the micro-electrode structure, traditional cathode fabrication processes, in pursuit of extremely low contact resistance, typically involve directly pressing a highly hydrophilic metallic conductive layer inside a hydrophobic layer, or physically mixing it with a catalyst layer. For example, the oxygen cathode structure disclosed in CN117543027A is formed by rolling a gas diffusion layer (i.e., a hydrophobic layer), a current collector layer (i.e., a metallic conductive layer), and a catalyst layer together. (The principle is explained in section

[0002] of the CN117543027A instruction manual: As a typical gas diffusion electrode, the oxygen cathode is widely used in various air batteries, chlor-alkali industry, electrochemical oxygen production and deoxygenation fields due to its special three-phase reaction site structure, and therefore it has been extensively studied. The most common oxygen cathode generally includes a gas diffusion layer, a current collector layer, and a catalyst layer. The reactant gas first passes through the pores of the gas diffusion layer and then enters the three-phase point region of the catalyst layer to carry out the three-phase reaction, while the current collector layer buried in the middle can better transfer electrons.) This conventional arrangement of the cathode has a fatal flaw in long-term operation: the built-in strongly hydrophilic metal conductive layer will form microscopic capillary channels, and the electrolyte will inevitably slowly penetrate along these channels and penetrate the outer hydrophobic layer (hydrophobic barrier), thereby blocking the air pores of the hydrophobic layer. This flooding phenomenon completely destroys the three-phase interface, causing gas diffusion to be blocked. The gas cannot pass smoothly through the pores of the hydrophobic layer to enter the three-phase point region of the catalyst layer for reaction, and the deoxygenation or oxygen production efficiency decreases significantly with the operating time.

[0006] Third, in the process of realizing this application, it was also discovered that the prior art lacks an overall asymmetric wetting gradient design, resulting in high mass transfer resistance and a high dependence on liquid electrolyte. Regarding the overall membrane electrode assembly, existing cathode, diaphragm, and anode combinations often lack an overall directional wetting design, and macroscopic physical gaps even exist between the plates. Conventional structures typically require the addition of a large amount of free electrolyte to fill the gaps and maintain the ion conduction path. Due to the failure to construct an asymmetric gradient structure transitioning from hydrophobic to hydrophilic, trace amounts of electrolyte cannot be effectively locked in the anode and diaphragm regions, and the cathode side cannot generate sufficient repulsive force against the free liquid. This leads to the device being prone to localized drying and lack of electrolyte under conditions of low electrolyte or trace amounts, which not only greatly increases the ohmic resistance of the system but also fails to achieve true zero-gap gas-liquid efficient separation.

[0007] Finally, conventional direct start-stop control logic accelerates the mechanical degradation of the three-phase interface. In terms of system operation control, existing electrochemical devices typically employ a crude control strategy of directly cutting off the power supply in standby or non-operating states. A complete power outage causes the electrochemical potential field on the electrode surface to disappear instantaneously, completely disrupting the gas-liquid interfacial tension balance maintained in the micropores of the catalyst layer by electrocapillary effects. Under static liquid pressure, the electrolyte gradually floods the hydrophobic pores of the cathode. When the device is cold-started again, the sudden increase in operating current triggers violent bubble nucleation and expansion, mechanically tearing the fragile catalyst layer, causing catalyst detachment, and ultimately resulting in a precipitous drop in the overall lifespan of the membrane electrode assembly.

[0008] To address at least one of the above problems, this invention is proposed. Summary of the Invention

[0009] This invention discloses a fully enclosed electrochemical device and control system. The device includes a cathode bottom cover 4 with cathode vent holes 4a and an anode top cover 5 with hydrophobic vent holes 5b. A membrane electrode assembly, with its edges surrounded and encapsulated by insulating ribs 6, is sealed and fixed inside the device. The membrane electrode assembly is composed of a cathode 1, a diaphragm 2, and an anode 3 stacked in a zero-gap manner. The cathode 1, from its outer periphery to its inner side, is provided with a first hydrophobic layer 1a, a hydrophobic framework layer 1b, a second hydrophobic layer 1c, a cathode catalytic layer 1d, and a hydrophilic conductive layer 1f, thereby constructing a directional wetting mass transfer gradient.

[0010] The supporting control system applies a small sustaining current when the device is in standby mode and employs flexible, gradual start-stop control. This invention, through the innovative arrangement of an asymmetric external conductive layer 1f and a purely hydrophobic outer barrier, combined with a fully sealed physical encapsulation and electrocapillary tension maintenance strategy, completely cuts off the capillary siphon and leakage paths of the electrolyte. This enables the device to be placed in a fully enclosed space with minimal electrolyte, exhibiting leak-free operation and extremely low attenuation over a long period with high stability.

[0011] The aforementioned sealing refers to the barrier against liquid.

[0012] In the prior art, the conductive layer is placed between the gas diffusion layer and the hydrophobic catalytic layer, and the left and right sides of the conductive layer can be considered as a symmetrical connection structure of hydrophobic and gas-permeable layers.

[0013] In this application, the asymmetric external placement of the conductive layer 1f refers to the arrangement order of the first hydrophobic layer 1a, the hydrophobic framework layer 1b, the second hydrophobic layer 1c, the cathode catalyst layer 1d, and the hydrophilic conductive layer 1f. The conductive layer 1f is located outside the first hydrophobic layer 1a, the hydrophobic framework layer 1b, the second hydrophobic layer 1c, and the cathode catalyst layer 1d.

[0014] The specific technical solution of this application is as follows:

[0015] The first aspect of this application provides a fully enclosed electrochemical device, the fully enclosed electrochemical device comprising:

[0016] A sealed housing with an internal cavity, the sealed housing including a cathode bottom cover 4 with a cathode vent hole 4a and an anode top cover 5 with a hydrophobic vent hole 5b;

[0017] A membrane electrode assembly is sealed and fixed in the internal cavity, and the edges of the membrane electrode assembly are surrounded and sealed by insulating encapsulation ribs 6.

[0018] The membrane electrode assembly includes a cathode 1, a diaphragm 2, and an anode 3 stacked sequentially, forming a tightly fitted structure with zero gaps.

[0019] The cathode 1 comprises, in a series of layers stacked from the side near the cathode bottom cover 4 to the side near the diaphragm 2: a porous composite liquid-blocking framework, a cathode catalytic layer 1d, and a conductive layer 1f.

[0020] The conductive layer 1f is directly adjacent to and bonded to the diaphragm 2;

[0021] In the membrane electrode assembly, from cathode 1 to anode 3, the hydrophilicity of the five components—the porous composite liquid-blocking framework, the cathode catalytic layer 1d, the conductive layer 1f, the diaphragm 2, and the anode 3—gradually increases.

[0022] A hydrophobic and breathable barrier layer is provided inside the hydrophobic and breathable hole 5b of the anode cover 5 for gas permeability and liquid resistance. The static water contact angle of the hydrophobic and breathable barrier layer is not less than 90°. The hydraulic pressure resistance is not less than 0.01 kPa.

[0023] Preferably, the porous composite liquid-blocking framework comprises, in sequence, a first hydrophobic layer 1a, a hydrophobic framework layer 1b, and a second hydrophobic layer 1c. The first hydrophobic layer 1a and the second hydrophobic layer 1c are both porous material layers with hydrophobic and breathable functions, a static water contact angle of not less than 90 degrees, a porosity of 5%-98%, and an average pore size of 0.001μm-1000μm.

[0024] The hydrophobic framework layer 1b is a hydrophobic porous support material with a three-dimensional interconnected pore structure, a static water contact angle of not less than 90 degrees, a porosity of 30%-95%, and a thickness of 1μm-20mm.

[0025] The anode 3 and the diaphragm 2 are configured to be hydrophilic, and the cathode 1 is configured to be hydrophobic.

[0026] Preferably, the conductive layer 1f extends and is connected to a cathode tab 1g, and the anode 3 extends and is connected to an anode tab 3b;

[0027] The cathode tab 1g and the anode tab 3b extend from the joint between the insulating encapsulation rib 6 and the sealing housing to the outside of the device, and the extension does not have a liquid leakage channel.

[0028] Preferably, the average pore size of the hydrophobic and breathable barrier layer is 0.001μm-500μm, the porosity is 10%-95%, and the thickness is 0.1μm-10mm.

[0029] Preferably, the sealing housing and the membrane electrode assembly together form a leak-proof structure:

[0030] The membrane electrode assembly is embedded in the insulating encapsulation rib 6. The insulating encapsulation rib 6 is tightly connected to the edges of the cathode bottom cover 4 and the anode top cover 5 by adhesive, hot melting or welding to form a physical seal.

[0031] Preferably, the static water contact angle of the anode 3 is not greater than 90°, and the overall thickness is 0.01mm-50mm.

[0032] Preferably, the membrane 2 is a separator material with ion conduction function, with a thickness of 0.001mm-50mm and an ion conductivity of not less than 0.01S / cm; the material of the separator is selected from ion exchange membranes, porous polymer membranes, inorganic porous membranes, organic-inorganic composite membranes, or composite structures of the above materials.

[0033] A second aspect of this application provides a fully enclosed electrochemical control system, the system comprising the fully enclosed electrochemical device as described in any one of the first aspects; and a power control system;

[0034] The power control system is electrically connected to the cathode tab 1g and anode tab 3b of the fully enclosed electrochemical device to apply a controllable current or a controllable voltage to the electrochemical device.

[0035] A third aspect of this application provides a fully enclosed electrochemical control method, wherein the control method uses the fully enclosed electrochemical control system described in the second aspect:

[0036] The control method includes:

[0037] The power control system controls the electrochemical device to be in a gas production mode or a standby mode by controlling the controllable current or controllable voltage applied to the electrochemical device.

[0038] When the electrochemical device is in standby maintenance mode, the power supply is not completely cut off, but a small maintenance current is continuously applied to the electrochemical device. The small current is 0.1%-50% of the operating current, in order to maintain the electrocapillary tension balance of the gas-liquid interface inside the cathode.

[0039] Preferably, when the electrochemical device switches between the gas production mode and the standby maintenance mode, a gradual transition control is adopted;

[0040] The gradual transition control includes at least one of the following: current ramp change, step change, exponential change, sinusoidal change or piecewise linear change; or voltage ramp change, step change, exponential change, sinusoidal change or piecewise linear change.

[0041] The transition time of the gradual transition control is 0.1 seconds to 1000 seconds.

[0042] Compared with the prior art, the present invention has the following significant advantages:

[0043] 1. Overcoming attitude limitations to achieve true "all-space attitude" leak-free operation.

[0044] This invention abandons the traditional open liquid cavity design, and uses insulating encapsulation ribs 6 to enclose the zero-gap membrane electrode assembly in a surrounding seal, seamlessly fused to the edges of the cathode bottom cover 4 and the anode top cover 5, while incorporating a venting structure with a hydrophobic and breathable membrane. This macroscopically purely physical "fully enclosed" encapsulation design cuts off the macroscopic channels for electrolyte leakage, enabling the electrochemical device to withstand extreme conditions such as tipping, inversion, severe vibration, and even microgravity, greatly expanding the application boundaries of deoxygenation / oxygenation equipment in aerospace and portable medical fields.

[0045] 2. Overturning conventional layout, completely eradicating the persistent problems of cathode "capillary siphon" and "flooding".

[0046] In traditional electrochemical oxygen removal devices, the air cathode faces a high risk of electrolyte leakage and "flooding" after long-term operation. The main reasons are as follows: First, under the operating electric field, electrowetting easily occurs at the cathode interface. Furthermore, the reactive oxygen free radicals generated during the oxygen reduction reaction continuously attack and degrade hydrophobic materials (such as PTFE) in the hydrophobic permeable layer, causing a sharp increase in surface energy and irreversible degradation of hydrophobicity, leading to the gradual intrusion of electrolyte into the hydrophobic micropores. Second, traditional technologies typically embed a metal conductive layer (or current collector) between the cathode catalyst layer and the permeable layer. Since metal materials have higher surface energy and hydrophilicity than carbon materials, once the electrolyte breaks through the surface hydrophobic barrier and contacts the embedded metal layer, the metal network provides a "high-speed hydrophilic pathway" for the electrolyte to permeate outward through capillary action. In addition, with the continuous leakage of electrolyte and water evaporation, internal solutes undergo salting-out and crystallization. The mechanical stress from crystal growth further physically expands the micropore channels and forms highly absorbent "salt bridges" within the pores, ultimately leading to irreversible and severe leakage problems, which seriously restrict the lifespan and reliability of the device. To address the shortcomings of traditional technologies that embed the metal conductive layer, resulting in easy leakage, this invention innovatively proposes an "asymmetric external current collection" cathode 5 structure. A hydrophilic metal conductive layer 1f is placed externally on the innermost side, directly bonded to the diaphragm 2. On the side near the external gas path, a first hydrophobic layer 1a, a hydrophobic framework layer 1b, and a second hydrophobic layer 1c are continuously arranged to form a porous composite liquid-blocking framework, constructing an extremely thick pure hydrophobic liquid-blocking barrier. This porous composite liquid-blocking framework not only meets the requirements for excellent electron conduction and current collection but also completely cuts off the "capillary siphon channel" for electrolyte creep at the microscopic physical level, effectively preventing catalyst layer flooding, ensuring gas diffusion channels, and guaranteeing long-term stability of deoxygenation / oxygenation efficiency.

[0047] 3. Constructing an asymmetric wetting gradient significantly reduces dependence on liquid electrolyte and system internal resistance.

[0048] The membrane electrode assembly of this invention exhibits an overall wettability gradient that increases from the outer cathode 1 (strongly hydrophobic) to the inner diaphragm 2 and anode 3 (hydrophilic). This directional gas-liquid mass transfer gradient generates a strong internal self-locking effect: it firmly adsorbs and locks extremely small amounts of liquid electrolyte into the anode and diaphragm regions, while simultaneously repelling it from entering the cathode pores. Combined with a zero-gap pressing process, this invention completely eliminates macroscopic liquid layer resistance, achieving truly "lean electrolyte (trace amount)" high-efficiency operation, effectively eliminating localized drying hotspots, significantly reducing ohmic internal resistance, and substantially reducing the overall size and weight of the device.

[0049] 4. Soft and hard synergistic control, utilizing the "electrocapillary effect" to extend the life of the electrode plates by multiple times.

[0050] The system control method accompanying this invention breaks away from the conventional, crude management approach of "directly cutting off power." By applying a small sustaining current during standby, the "electrocapillary effect" generated by the electrochemical potential field firmly locks the three-phase interface, preventing static hydraulic pressure from intruding into the cathode pores; simultaneously, it is supplemented by gradual, flexible start-stop current control. This combined hardware and software control strategy effectively avoids the mechanical tearing effect on the catalyst layer caused by the violent expansion of bubbles generated by the instantaneous high current during cold start, preventing catalyst shedding and resulting in an exponential leap in the operating life of the electrochemical device. Attached Figure Description

[0051] Figure 1 This is a three-dimensional exploded structural diagram of the fully enclosed electrochemical device provided in Embodiment 1 of the present invention.

[0052] Figure 2 This is a schematic diagram of the microscopic cross-sectional hierarchy of the membrane electrode assembly (focusing on the asymmetric gradient cathode) provided in Embodiment 1 of the present invention.

[0053] Figure 3 This is a three-dimensional structural schematic diagram of the zero-gap membrane electrode assembly provided in Embodiment 1 of the present invention.

[0054] Figure 4 This is a three-dimensional schematic diagram of a membrane electrode assembly with edge insulating encapsulation ribs 6 provided in Embodiment 2 of the present invention.

[0055] Figure 5 This is a test curve of the oxygen removal performance of the fully enclosed electrochemical device in Embodiment 3 of the present invention under specific operating conditions.

[0056] Figure 6 This is a performance comparison test chart of the hydrophilic anode in Embodiment 3 of the present invention under different electrolyte injection conditions.

[0057] Figure 7 This is a comparison chart of the electrochemical performance of the membrane electrode with a superhydrophilic / superhydrophobic gradient structure in Example 3 of the present invention and the conventional structure without gradient.

[0058] Figure 8 This is a comparison test diagram of the stability of the gradient wettability cathode and the conventional cathode under long-term operation in Embodiment 3 of the present invention.

[0059] Figure 9 This is a comparison test chart of the system operation stability using the "micro-current maintenance + flexible start-stop" collaborative control strategy of Embodiment 3 of the present invention and the conventional power-off start-stop strategy.

[0060] Figure 10 This is the connection method between the power control system and the electrochemical device in Embodiment 3 of the present invention.

[0061] List of reference numerals

[0062] 1. Cathode; 1a. First hydrophobic layer; 1b. Hydrophobic framework layer; 1c. Second hydrophobic layer; 1d. Cathode catalyst layer; 1f. Conductive layer; 1g. Cathode tab; 2. Separator layer; 3. Anode; 3a. Hydrophilic anode; 3b. Anode tab; 4. Cathode bottom cover; 4a. Cathode vent hole; 4b. Assembly tank; 4c. Cathode housing; 5. Anode top cover; 5a. Assembly line; 5b. Hydrophobic vent hole; 5c. Top cover housing; 6. Encapsulation rib. Detailed Implementation

[0063] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in the manual, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials used in the following embodiments and comparative examples are all commercially available.

[0064] In order to solve the above-mentioned technical problems in the background art, the purpose of this invention is to provide a fully enclosed electrochemical device and electrochemical control system. Through the synergistic effect of macroscopic sealing structure, microscopic electrode layer, directional wetting gradient and dynamic microcurrent control, the physical and capillary leakage paths of electrolyte are completely blocked, realizing the device's full-space posture placement and long-term stable operation under micro-electrolyte conditions.

[0065] To achieve the above objectives, the present invention adopts the following technical solution:

[0066] The present invention provides a fully enclosed electrochemical device, comprising: a sealed housing having an internal cavity, the sealed housing including a cathode bottom cover 4 having a cathode vent 4a and an anode top cover 5 having a hydrophobic vent 5b, and a membrane electrode assembly sealed and fixed in the internal cavity.

[0067] The edges of the membrane electrode assembly are sealed around the perimeter by insulating encapsulation ribs 6; the membrane electrode assembly includes a cathode 1, a diaphragm 2, and an anode 3 stacked sequentially. The cathode 1, diaphragm 2, and anode 3 form a tightly fitted structure with zero gaps.

[0068] The cathode 1 comprises, in sequence from the side near the cathode bottom cover 4 to the side near the diaphragm 2, a first hydrophobic layer 1a, a hydrophobic framework layer 1b, a second hydrophobic layer 1c, a cathode catalyst layer 1d, and a conductive layer 1f. The conductive layer 1f is directly adjacent to and bonded to the diaphragm 2; the conductive layer 1f extends and is connected to a cathode tab 1g, and the anode 3 extends and is connected to an anode tab 3b.

[0069] Preferably, the sealing housing and the membrane electrode assembly together form a leak-proof structure: the membrane electrode assembly is embedded in the insulating encapsulation rib 6, and the insulating encapsulation rib 6 is tightly connected to the edges of the cathode bottom cover 4 and the anode top cover 5 by adhesive, hot melting or welding to form a physical seal;

[0070] The cathode tab 1g and the anode tab 3b extend from the joint between the insulating encapsulation rib 6 and the sealing housing to the outside of the device, and the extension does not have a liquid leakage channel.

[0071] The surface of the cathode 1 is positioned opposite to the cathode vent 4a, and a hydrophobic and breathable membrane is fixedly provided inside the hydrophobic vent 5b of the anode cover 5.

[0072] Preferably, a directional gas-liquid mass transfer gradient is constructed within the membrane electrode assembly: the membrane electrode assembly as a whole exhibits a hydrophilicity increasing gradient from cathode 1 to anode 3; wherein the anode 3 and the membrane 2 are configured to be hydrophilic, and the cathode 1 is configured to be hydrophobic. Further, within the cathode 1, a wettability increasing gradient is formed from the first hydrophobic layer 1a to the conductive layer 1f, wherein the first hydrophobic layer 1a is strongly hydrophobic, and the conductive layer 1f is hydrophilic.

[0073] Strong hydrophobicity refers to a static water contact angle of not less than 90°. Hydrophilicity refers to a static water contact angle of not more than 90°.

[0074] Preferably, each layer in the cathode 1 satisfies the following parameter limitations:

[0075] The first hydrophobic layer 1a and the second hydrophobic layer 1c are both porous material layers with hydrophobic and breathable functions, with a static water contact angle of not less than 90°, a porosity of 5%-98%, and an average pore size of 0.001μm-1000μm.

[0076] Preferably, the porous material layer is selected from any one or more combinations of fluoropolymers, hydrocarbon polymers, organosilicon polymers, inorganic hydrophobic porous materials, carbon-based porous materials, or composite materials of the above. The thickness of the porous material layer is 0.1 μm-10 mm, and the structural form includes a single layer, a multilayer composite layer, or a functional layer with a gradient change in pore size / hydrophobicity.

[0077] Preferably, the hydrophobic framework layer 1b is a hydrophobic porous support material with a three-dimensional interconnected pore structure, a static water contact angle of not less than 90°, a porosity of 30%-95%, and a thickness of 1μm-20mm.

[0078] Preferably, the hydrophobic porous support material is selected from hydrophobically modified inorganic porous materials, hydrophobic polymer porous materials, hydrophobically modified fiber braids or non-woven fabrics, or composite structures of the above materials.

[0079] Preferably, the cathode catalytic layer 1d is composed of electrocatalytic active material, binder and hydrophobic additive, with a static water contact angle of not less than 80° and a thickness of 0.01μm-500μm.

[0080] Preferably, the electrocatalytic active material is selected from at least one of noble metal catalysts, non-noble metal catalysts, metal-nitrogen-carbon coordination catalysts, metal oxide catalysts, metal sulfide catalysts, metal phosphide catalysts, single-atom catalysts, or complexes of the above catalysts.

[0081] Preferably, the binder is selected from at least one of fluoropolymer binders, sulfonic acid polymer binders, hydrocarbon polymer binders, or inorganic binders. The hydrophobic additive is selected from at least one of fluoropolymers, organosilicon compounds, long-chain alkyl compounds, or hydrophobic nanoparticles.

[0082] Preferably, the conductive layer 1f is a current collector material with electronic conductivity, a conductivity of not less than 10³ S / m, and a thickness of 1 μm-5 mm. The current collector material is selected from metallic materials, conductive alloys, conductive polymers, carbon-based conductive materials, or composite materials of the above. The structural form of the current collector is selected from metal mesh, metal foil, metal felt, metal foam, carbon fiber cloth, carbon paper, conductive coating, or a composite of the above structures.

[0083] Preferably, the anode 3 includes a conductive substrate and an electrocatalytic active layer supported thereon. The surface of the anode 3 has hydrophilic properties, with a static water contact angle of no more than 90° and an overall thickness of 0.01 mm to 50 mm.

[0084] The conductive substrate is made of a material selected from metallic materials, conductive alloys, carbon-based materials, conductive polymers, or composite materials of the above.

[0085] The structure of the conductive substrate is selected from any one of the following: mesh structure, porous foam structure, fiber felt structure, sheet structure, or three-dimensional skeleton structure.

[0086] The electrocatalytic active layer is composed of an oxygen evolution reaction catalyst, which is selected from at least one of transition metal oxides, transition metal hydroxides, transition metal phosphides, transition metal sulfides, transition metal nitrides, noble metal oxides, perovskite oxides, spinel oxides, layered bimetallic hydroxides, or complexes of the above catalysts.

[0087] Preferably, the separator 2 is a separator material with ion conduction function, with a thickness of 0.001 mm to 50 mm and an ionic conductivity of not less than 0.01 S / cm. The separator material is selected from ion exchange membranes, porous polymer membranes, inorganic porous membranes, organic-inorganic composite membranes, or composite structures of the above materials. Specifically, the ion exchange membrane is selected from at least one of anion exchange membranes, cation exchange membranes, zwitterionic exchange membranes, or bipolar membranes. The porous polymer membrane is selected from at least one of polyolefin separators, fluoropolymer separators, polyarylene ether separators, cellulose separators, or modified membranes of the above materials. The inorganic porous membrane is selected from at least one of ceramic porous membranes, glass fiber membranes, metal oxide porous membranes, or composite membranes of the above materials.

[0088] Preferably, the cathode vent 4a of the cathode bottom cover 4 is a through-type ventilation channel, and its cross-sectional shape is selected from any one of the following: circular, elliptical, polygonal, slit-shaped, grid-shaped, or irregular. The equivalent opening size of the ventilation channel is 0.01mm-500mm, and the opening ratio is 5%-95%. The ventilation channels are distributed uniformly, in a gradient, or in zones on the surface of the device.

[0089] Preferably, a hydrophobic and breathable barrier layer is provided inside the hydrophobic and breathable hole 5b of the anode cover 5. The hydrophobic and breathable barrier layer is a porous material with selective air permeability and liquid blocking function, with a static water contact angle of not less than 90° and hydraulic pressure resistance of not less than 0.01KPa.

[0090] The material of the hydrophobic and breathable barrier layer is selected from at least one of fluoropolymers, polyolefin polymers, organosilicon polymers, hydrophobically modified cellulose, hydrophobically modified inorganic porous materials, or composite materials of the above materials;

[0091] The average pore size of the hydrophobic and breathable barrier layer is 0.001 μm-500 μm, the porosity is 10%-95%, and the thickness is 0.1 μm-10 mm. The structure of the hydrophobic and breathable barrier layer can be a single-layer membrane, a multi-layer composite membrane, a gradient pore size membrane, or a superhydrophobic membrane with a micro-nano rough structure on the surface.

[0092] Another object of the present invention is to provide an electrochemical control system, comprising: a fully enclosed electrochemical device as described above; and a power control system;

[0093] The power control system is electrically connected to the cathode tab 1g and anode tab 3b of the fully enclosed electrochemical device, and is used to apply a controllable current or a controllable voltage to the electrochemical device.

[0094] The power control system is configured to execute the following control logic:

[0095] The power control system controls the electrochemical device to be in a gas production mode or a standby mode by controlling the controllable current or controllable voltage applied to the electrochemical device.

[0096] When the electrochemical device is in standby maintenance mode, i.e., non-gas production working state, the power supply is not completely cut off, but a small maintenance current of 0.1%-50% of the working current is continuously applied to the device to maintain the electrocapillary tension balance of the gas-liquid interface inside the cathode.

[0097] The power control system is further configured to employ a gradual, flexible transition control with a transition time of 0.1 seconds to 1000 seconds when switching between the gas production mode and the standby mode. The gradual transition control includes at least one of the following: a ramp change, a step change, an exponential change, a sinusoidal change, or a piecewise linear change in current; or at least one of the following: a ramp change, a step change, an exponential change, a sinusoidal change, or a piecewise linear change in voltage.

[0098] In the gas production mode, the power control system controls the controllable current applied to the electrochemical device to be the operating current.

[0099] Example 1: Fabrication of an asymmetric gradient film electrode assembly

[0100] This embodiment provides a membrane electrode assembly with a microscopic wettability gradient, combined with Figure 2 and Figure 3 As shown, its preparation process is as follows:

[0101] (1) Preparation of the cathode liquid-resistant support system:

[0102] Conductive carbon black, a volatile pore-forming agent (ammonium bicarbonate), and a PTFE (polytetrafluoroethylene) emulsion binder were mixed at a mass ratio of 60:20:20. An appropriate amount of anhydrous ethanol solvent was added, and the mixture was thoroughly stirred to prepare a semi-solid paste. The paste was then calendered into a 200 μm thick base film using a two-roll press hot rolling technique (rolling temperature approximately 80°C). Two layers of this base film were used as the first hydrophobic layer 1a and the second hydrophobic layer 1c. A 100 μm thick PTFE mesh with a 200-mesh pore size (as the hydrophobic framework layer 1b) was sandwiched between the two layers, and a second hot rolling composite was performed in a sandwich configuration. Subsequently, the composite layer was heated in a muffle furnace at 280°C for 2 hours to completely evaporate the pore-forming agent, forming a three-dimensional porous composite liquid-blocking framework with an internal pore size of approximately 100 nm.

[0103] (2) Preparation of the cathode catalyst layer:

[0104] A Fe-NC cathode catalyst with a particle size of approximately 1 μm was synthesized using formamide as a precursor. This preparation method is existing technology. The preparation method in this embodiment is as follows: Fe-NC catalyst was synthesized using formamide as a nitrogen source precursor. The materials were prepared according to the mass ratio of carbon source:pore-forming salt:iron source = 1:1:0.03, that is, 10.0 g of Ketjenblack EC-600JD conductive carbon, 10.0 g of ZnCl2, and 0.30 g of anhydrous FeCl3 (equivalent to a Fe / carbon source mass ratio of approximately 1.0 wt%) were added to 100 mL of formamide. The mixture was wet-milled at 400 rpm for 2 h using a planetary ball mill to obtain a uniform slurry. After desolvation in a rotary evaporator at 60℃, the slurry was dried in a vacuum oven at 60℃ for 12 h to obtain a solid precursor. The precursor was placed in a tube furnace and purged with nitrogen (200 mL / min). The temperature was increased to 950℃ at 5℃ / min and held for 1 h for carbonization. After cooling, the precursor was treated with 0.5... mol / L sulfuric acid (solid-liquid ratio 1:50 g / mL) was magnetically stirred and washed at 80℃ for 2 h to remove free metals and Zn species. After washing with deionized water until the pH of the filtrate was ≈7, it was vacuum dried at 60℃ for 12 h. Then, it was pulverized by air jet and passed through a 200-mesh sieve to obtain Fe and N co-doped porous carbon powder (Fe-NC). The D50 was ≈1.0 μm and the D90 was ≤3.0 μm as measured by a laser particle size analyzer.

[0105] Then, the Fe-NC cathode catalyst was mixed with Nafion perfluorosulfonic acid resin binder and isopropanol solvent, and ultrasonically dispersed to form a catalyst slurry. The catalyst slurry was then uniformly loaded onto one side of the above-mentioned composite liquid-blocking framework by a blade coating process to form a cathode catalyst layer with a thickness of approximately 50 μm.

[0106] (3) Preparation of hydrophilic anode 3a:

[0107] NiFe-LDH (nickel-iron layered double hydroxide) anode catalyst was prepared on a 500 μm thick nickel foam substrate using electrodeposition technology. Specifically, a mixed aqueous solution containing 0.1 mol / L nickel nitrate and 0.05 mol / L ferric nitrate was prepared, and electrodeposition was performed for 30 minutes at a constant current density of 10 mA / cm² using nickel foam as the working electrode. The prepared NiFe-LDH exhibited a nanoarray structure on its surface and displayed superhydrophilic properties with a contact angle of less than 40°, forming a hydrophilic anode 3a.

[0108] (4) Tab welding and zero-gap lamination of membrane electrode:

[0109] A stretched nickel mesh with a thickness of 150 μm is used as the cathode conductive layer 1f. Before use, a solid nickel sheet with a thickness of 200 μm is welded to the cathode conductive layer 1f and the substrate edge of the hydrophilic anode 3a respectively by ultrasonic metal welding technology to form the cathode tab 1g and the anode tab 3b.

[0110] A glass fiber diaphragm was used as the diaphragm. The glass fiber diaphragm was purchased from Shanghai Xinya Purification Equipment Factory.

[0111] Subsequently, the coated cathode semi-finished product, glass fiber diaphragm, hydrophilic anode 3a, and cathode conductive layer 1f with pre-welded tabs are stacked sequentially. Note that the cathode conductive layer 1f (hydrophilic metal) is placed directly between the cathode catalyst layer 1d and the diaphragm 2, completely exposing it to the hydrophobic system. Finally, hot-pressing composite is performed at 2MPa and 120℃ using a hot press to prepare a zero-gap membrane electrode assembly with an asymmetric gradient distribution of "strong hydrophobicity (three-dimensional porous composite liquid-blocking framework) - weak hydrophobicity (cathode catalyst layer 1d) - hydrophilicity (cathode conductive layer 1f, glass fiber diaphragm) - superhydrophilicity (hydrophilic anode 3a)".

[0112] Example 2: Packaging and Assembly of a Fully Enclosed Electrochemical Device

[0113] Combination Figure 1 and Figure 4 As shown, this embodiment performs a fully enclosed assembly of the membrane electrode assembly obtained in Example 1:

[0114] (1) Edge leak-proof sealing:

[0115] The entire membrane electrode assembly is placed in an injection mold. Corrosion-resistant, high-polymer insulating plastic PP is used for insert injection molding to form insulating encapsulation ribs 6 around the perimeter of the membrane electrode assembly. The injection molding process ensures that the edge pores of the membrane electrode are completely impregnated and filled with plastic, eliminating any liquid bypass channels. The cathode tab 1g and anode tab 3b extend seamlessly from the pre-drilled openings in the insulating encapsulation ribs 6.

[0116] (2) Shell assembly and electrolyte injection:

[0117] Both the anode top cover 5 and the cathode bottom cover 4 are obtained by injection molding. The anode top cover 5 has a rectangular top cover shell 5c, an assembly line 5a, and a hydrophobic vent 5b. The assembly line 5a is arranged along the long side of the top cover shell 5c.

[0118] The membrane electrode with insulating encapsulation ribs 6 is pressed into the assembly groove 4b of the cathode bottom cover 4 in an embedded manner. Multiple cathode vent holes 4a are evenly distributed on the bottom of the cathode bottom cover 4, and after assembly, the first hydrophobic layer 1a of the cathode is aligned with each vent hole 4a. The insulating encapsulation ribs 6 are completely sealed to the inner edge of the cathode bottom cover 4 by dispensing adhesive or ultrasonic welding.

[0119] Subsequently, the assembly line 5a on the injection-molded anode top cover 5 is aligned with the assembly groove 4b on the cathode bottom cover 4, and the two are fused together into a fully enclosed sealed shell using an ultrasonic plastic welding process. 100 mL of a high-concentration alkaline electrolyte (such as 30 wt% KOH) is injected into the device through a pre-reserved injection hole. Finally, a PTFE hydrophobic and breathable membrane is ultrasonically welded at the injection hole to form a hydrophobic and breathable pore 5b that allows air to pass through but not liquid, thus completing the manufacturing of the fully enclosed electrochemical device.

[0120] Example 3: Device Performance Verification and Comparative Analysis

[0121] To verify the unexpected technical effects brought about by the "asymmetric gradient structure" and "micro-current flexible control" of this invention, the following performance tests were conducted:

[0122] (1) Verification of the fully enclosed deoxygenation performance ( Figure 5 ):

[0123] The electrochemical device prepared in Example 2 of this invention was placed in a 20L sealed test chamber and operated. The initial oxygen concentration inside the chamber was 21% of the natural ambient oxygen concentration. Figure 5 As shown, under constant current operation of 5A, the oxygen concentration in the sealed chamber decreased to 7% with high linearity within 120 minutes. This indicates that the device can achieve extremely excellent deoxygenation function in an independent, fully enclosed state without external pumps or valves.

[0124] (2) Verification of the operational capability of micro-electrolyte Figure 6 ):

[0125] The core advantage of this invention, "gradient wettability," is demonstrated through testing. This is achieved by extracting electrolyte from the device to simulate a lean electrolyte condition. For example... Figure 6 As shown, when the electrolyte in the device is gradually reduced from 100 mL to 10 mL, the operating voltage of the device remains almost stable; the voltage only begins to rise (performance declines) when only 5 mL of electrolyte remains. This strongly demonstrates that, thanks to the powerful capillary self-adsorption effect of the hydrophilic anode 3a and the microscopic wetting gradient, even a very small amount of liquid electrolyte can completely spread within the electrode plate and maintain ion channels. This endows the invention with extremely strong resistance to drying out and greatly reduces the overall weight of the device.

[0126] (3) Performance comparison between gradient structure and conventional structure Figure 7 ):

[0127] A conventional cathode was prepared, with the following structure: an outer hydrophobic layer, an inner current collector metal mesh, an inner hydrophobic layer, and a catalyst layer. The specific fabrication method was as follows: the base film from step (1) of Example 1 was used as the outer and inner hydrophobic layers. The cathode conductive layer 1f from Example 1 was used as the inner current collector metal mesh. The catalyst layer was prepared in the same manner as in Example 1. After the outer hydrophobic layer, current collector metal mesh, and inner hydrophobic layer were rolled into a single unit using a hot rolling method, the cathode catalyst layer was loaded using a scraping method to form a four-in-one conventional cathode. The cathode and anode tabs were arranged in the same manner as in Example 1.

[0128] The conventional cathode, diaphragm 2, and hydrophilic anode 3a are stacked sequentially, and then hot-pressed together at 2 MPa and 120°C to prepare a conventional cathode assembly. This assembly is then packaged and assembled using the method described in Example 2 to form an electrochemical device containing a conventional cathode.

[0129] The electrochemical device prepared in Example 2 was compared with an electrochemical device containing a conventional cathode. For example... Figure 7 As shown, under the same operating conditions, the high-current discharge capability of the gradient wetting cathode device of the present invention far exceeds that of conventional devices. At a current of 400mA, the polarization voltage of the device of the present invention is about 100mV lower than that of conventional devices. This is because the gradient wetting structure of the present invention constructs a richer and more three-dimensional three-phase interface, reducing gas mass transfer resistance.

[0130] (4) Completely solve the lifespan verification of "capillary flooding" ( Figure 8 ):

[0131] The electrochemical device prepared in Example 2 and the electrochemical device containing a conventional cathode were subjected to long-term constant current stability tests. The test conditions were room temperature 25°C and constant current operation of 5A.

[0132] like Figure 8 As shown, in conventional electrochemical devices with cathodes, the hydrophilic current collector mesh is encased within a hydrophobic layer, inevitably leading to a capillary effect. This causes electrolyte to seep into the hydrophobic layer, triggering flooding. Within 900 hours, the voltage spikes from 1.14V to 1.55V, resulting in severe performance degradation of up to 410mV. In contrast, the asymmetric gradient cathode of this invention completely exposes the hydrophilic conductive layer 1f to the inside of the catalyst layer and establishes a thick liquid-blocking barrier supported by a hydrophobic framework, effectively cutting off the capillary path. Therefore, after 1700 hours of operation, the electrochemical device prepared in Example 2 only experiences a slight voltage increase from 1.07V to 1.12V (a minimal degradation of only 50mV), achieving long-term leak-proof operation.

[0133] (5) Verification of the synergistic effect of system control strategies Figure 9 ):

[0134] To verify the advantages of the system control method in the claims, the electrochemical device prepared in Example 2 was used to compare the long-term performance of "conventional direct power-off start-stop control (constant current mode 5A current operation for 1 hour and shutdown for 1 hour)" and "the soft and hard collaborative control of the present invention (constant current mode 5A operation for 1 hour, with 5A flexibly reduced to 0.1A within 5 minutes to maintain operation for 1 hour, and then flexibly increased to 5A within 5 minutes)".

[0135] The flexibility was reduced to 0.1A within 5 minutes by using a step-by-step change in current, with a uniform change rate of 1A / min.

[0136] like Figure 9 As shown, after 900 hours of operation, the voltage in the conventional direct power-off mode rose from 1.12V to 1.56V. However, the voltage of the device using micro-current sustaining + flexible start-stop control only rose from 1.15V to 1.34V. The physical mechanism lies in the fact that applying a small sustaining current during standby maintains the tension balance of the "electrocapillary effect" within the micropores of the electrode, firmly locking the gas-liquid three-phase interface and preventing hydraulic fluid from entering the cathode. Simultaneously, the flexible stepped start-stop effectively avoids the mechanical erosion and stripping of the catalyst caused by instantaneous high-current boiling.

Claims

1. A fully enclosed electrochemical device, characterized in that, The fully enclosed electrochemical device includes: A sealed housing with an internal cavity, the sealed housing including a cathode bottom cover (4) with a cathode vent (4a) and an anode top cover (5) with a hydrophobic vent (5b). A membrane electrode assembly is sealed and fixed in the internal cavity, and the edge of the membrane electrode assembly is surrounded and sealed by insulating encapsulation ribs (6); The membrane electrode assembly includes a cathode (1), a diaphragm (2) and an anode (3) stacked in sequence, forming a tightly fitted structure with zero gaps; The cathode (1) comprises, in sequence from the side near the cathode bottom cover (4) to the side near the diaphragm (2): a porous composite liquid-blocking framework, a cathode catalytic layer (1d), and a conductive layer (1f); The conductive layer (1f) is directly adjacent to and bonded to the diaphragm (2); In the membrane electrode assembly, from the cathode (1) to the anode (3), the hydrophilicity of the five components—the porous composite liquid-blocking framework, the cathode catalyst layer (1d), the conductive layer (1f), the diaphragm (2), and the anode (3)—gradually increases. The anode cover (5) has a hydrophobic and breathable barrier layer inside the hydrophobic and breathable hole (5b) for air permeability and liquid blocking. The static water contact angle of the hydrophobic and breathable barrier layer is not less than 90°.

2. The fully enclosed electrochemical device according to claim 1, characterized in that, The porous composite liquid-blocking framework comprises, in sequence, a first hydrophobic layer (1a), a hydrophobic framework layer (1b), and a second hydrophobic layer (1c); The first hydrophobic layer (1a) and the second hydrophobic layer (1c) are both porous material layers with hydrophobic and breathable functions, with a static water contact angle of not less than 90 degrees, a porosity of 5%-98%, and an average pore size of 0.001μm-1000μm. The hydrophobic framework layer (1b) is a hydrophobic porous support material with a three-dimensional interconnected pore structure, a static water contact angle of not less than 90 degrees, a porosity of 30%-95%, and a thickness of 1μm-20mm.

3. The fully enclosed electrochemical device according to claim 1, characterized in that, The conductive layer (1f) extends and is connected to a cathode tab (1g), and the anode (3) extends and is connected to an anode tab (3b); The cathode tab (1g) and the anode tab (3b) extend from the joint between the insulating encapsulation rib (6) and the sealing housing to the outside of the device, and the extension does not have a liquid leakage channel.

4. The fully enclosed electrochemical device according to claim 1, characterized in that, The average pore size of the hydrophobic and breathable barrier layer is 0.001μm-500μm, the porosity is 10%-95%, and the thickness is 0.1μm-10mm.

5. The fully enclosed electrochemical device according to claim 1, characterized in that, The sealed housing and the membrane electrode assembly together form a leak-proof structure: The membrane electrode assembly is embedded in the insulating encapsulation rib (6), and the insulating encapsulation rib (6) is tightly connected to the edges of the cathode bottom cover (4) and the anode top cover (5) by adhesive, hot melting or welding to form a physical seal.

6. The fully enclosed electrochemical device according to claim 1, characterized in that, The static water contact angle of the anode (3) is no greater than 90°, and the overall thickness is 0.01mm-50mm.

7. The fully enclosed electrochemical device according to claim 1, characterized in that, The diaphragm (2) is a separating material with ion conduction function, with a thickness of 0.001mm-50mm and an ion conductivity of not less than 0.01S / cm; the material of the separating material is selected from ion exchange membrane, porous polymer membrane, inorganic porous membrane, organic-inorganic composite membrane or composite structure of the above materials.

8. A fully enclosed electrochemical control system, characterized in that, The system includes the fully enclosed electrochemical device according to any one of claims 1-7; and a power control system; The power control system is electrically connected to the cathode tab (1g) and anode tab (3b) of the fully enclosed electrochemical device to apply a controllable current or a controllable voltage to the electrochemical device.

9. A fully enclosed electrochemical control method, characterized in that, The control method uses the fully enclosed electrochemical control system described in claim 8: The control method includes: The power control system controls the electrochemical device to be in a gas production mode or a standby mode by controlling the controllable current or controllable voltage applied to the electrochemical device. When the electrochemical device is in standby maintenance mode, the power supply is not completely cut off, but a small maintenance current is continuously applied to the electrochemical device. The small current is 0.1%-50% of the operating current, in order to maintain the electrocapillary tension balance of the gas-liquid interface inside the cathode.

10. The fully enclosed electrochemical control method according to claim 9, characterized in that, When the electrochemical device switches between gas production mode and standby mode, a gradual transition control is used. The gradual transition control includes at least one of the following: current ramp change, step change, exponential change, sinusoidal change or piecewise linear change; or voltage ramp change, step change, exponential change, sinusoidal change or piecewise linear change. The transition time of the gradual transition control is 0.1 seconds to 1000 seconds.

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