An ion energy power generation device based on deep-sea hydrostatic pressure driving

Abstract

The application relates to a kind of ion energy power generation devices based on deep-sea hydrostatic pressure driving, including titanium alloy sealed cavity, gradient multilayer nanocomposite ion selective membrane, magnetic coupling piston pressure transmission mechanism, platinized titanium mesh inner electrode, titanium mesh outer electrode and suspended anchoring system. High concentration salt solution is preloaded in the cavity, and deep-sea pressure is transmitted to the internal solution by magnetic coupling piston, drives cation selective transmembrane outward migration to form continuous ion current, and external power supply is collected after electrode. Membrane assembly adopts gradient composite structure of high-strength porous support layer combined with MOF / GO functional layer, maintains high ion selectivity and structural integrity under 10MPa hydrostatic pressure. Theoretical model is based on irreversible thermodynamics phenomenological equation, and ion flux and output power under pressure assistance are derived. Experiments prove that the power density of single module can reach 0.36mW / cm², and multiple modules can provide milliwatt to watt level power for deep-sea communication beacon through series and parallel combination, and maintenance is free within several years after deployment.

Description

Technical Field

[0001] This invention relates to the field of deep-sea energy and electrochemical power generation technology, and in particular to an ion energy power generation device driven by deep-sea hydrostatic pressure. Background Technology

[0002] The long-term energy supply for deep-sea exploration and operation equipment is one of the core bottlenecks restricting the development of marine technology. Current mainstream solutions rely on high-energy-density primary batteries or periodically rechargeable secondary batteries. Primary batteries are limited by their total energy capacity and cannot support deployment cycles measured in years; secondary batteries require expensive and high-risk underwater recovery operations, resulting in extremely high operation and maintenance costs. Utilizing marine environmental energy for in-situ power generation is an ideal way to solve these problems.

[0003] Currently proposed technological approaches include ocean current turbine power generation, thermoelectric power generation, wave energy power generation, and salinity gradient power generation. Ocean current turbine power generation faces three major obstacles in the deep-sea environment: typical deep-sea current velocities are only 0.1-0.5 m / s, far lower than the starting current velocity of traditional water turbines; the direction of deep-sea currents is random and variable, requiring complex yaw mechanisms; and rotating dynamic seals are prone to leakage and failure under pressures exceeding 10 MPa. Thermoelectric power generation utilizes the temperature difference between surface warm water and deep-sea cold water to drive heat engines or thermoelectric materials, but the vertical temperature difference in the deep sea is typically no more than 25°C, resulting in low thermoelectric conversion efficiency and requiring large cold seawater pipelines, leading to a bulky system. Wave energy generation relies on sea surface fluctuations and is not suitable for the quiet environment of the deep sea.

[0004] Salinity gradient energy (SGR) power generation utilizes the osmotic pressure difference between freshwater and seawater, generating electricity through pressure-delayed osmosis (PDOS) or reverse electrodialysis. This technology has been extensively studied since the 1970s, but large-scale commercialization has yet to be achieved. Its main bottlenecks are: the concentration gradient in natural estuarine environments is unstable and spatially limited; both PDOS and reverse electrodialysis rely on externally pumped solutions to maintain the concentration gradient, resulting in significant parasitic energy consumption; and the mechanical strength of existing ion exchange membranes can only withstand pressures of 0.2 MPa to 2 MPa, far lower than the 10 MPa hydrostatic pressure in the deep sea.

[0005] In summary, existing technologies cannot achieve long-term, maintenance-free, stable power generation in the complex environment of deep-sea high pressure, low flow velocity, multi-directional flow, and silt deposition. There is an urgent need for a new power generation principle and device that can overcome the above bottlenecks. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an ion energy power generation device driven by deep-sea hydrostatic pressure. The device uses the hydrostatic pressure at a depth of 500-1000 meters in the deep sea as an energy source to drive the selective transmembrane migration of ions in a high-concentration salt solution to form a continuous ion current, which in turn generates direct current through electrode reaction. The device has no moving parts, is not affected by the direction and velocity of ocean currents, and can be suspended above the silt layer for long-term maintenance-free operation.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is: an ion energy power generation device driven by deep-sea hydrostatic pressure, the innovation of which lies in: including A pressure-resistant sealed cavity is filled with a first electrolyte solution, the ion concentration of which is higher than that of the seawater outside the pressure-resistant sealed cavity. At least one ion-selective membrane module is installed on the wall of the pressure-resistant sealed cavity, allowing selective transmembrane migration of cations in the first electrolyte solution; The magnetically coupled piston pressure transmission mechanism transmits the hydrostatic pressure of external seawater to the pressure-resistant sealed cavity, so that the first electrolyte solution is subjected to a pressure not greater than that of the external seawater, thereby driving the ions to migrate across the membrane. The first electrode is disposed inside the pressure-resistant sealed cavity and is in electrical contact with the first electrolyte solution; The second electrode is located outside the pressure-resistant sealed cavity and is in electrical contact with seawater. An external circuit, connecting the first electrode and the second electrode, is used to collect the current generated by ion migration.

[0008] Furthermore, the ion-selective membrane assembly is a gradient multilayer nanocomposite membrane, which includes, from bottom to top, a high-strength porous support layer, an intermediate transition layer, and a functional separation layer; the functional separation layer is assembled by covalent cross-linking of metal-organic framework nanocrystals and graphene oxide nanosheets, and has regular sub-nanometer ion channels.

[0009] Furthermore, the metal-organic framework is UiO-66-NH2; the thickness of the functional separation layer is 50 nm to 500 nm, and the channel size is 0.3 nm to 1.0 nm.

[0010] Furthermore, it also includes a concentration regeneration subsystem, consisting of an auxiliary electrode, a programmable power supply, and a control unit, which is used to pump ions from external seawater back into the cavity through reverse electrodialysis when the internal concentration decreases, thereby restoring the concentration gradient.

[0011] Furthermore, it also includes a suspended mooring system, which consists of a buoyancy carrier and a counterweight, allowing the entire device to be suspended at a depth of 500 to 1000 meters.

[0012] A method for generating electricity using deep-sea hydrostatic pressure-driven ion energy, applied to a device for generating electricity using deep-sea hydrostatic pressure-driven ion energy; its innovation lies in the following steps: The pressure-resistant sealed cavity is placed in a deep-sea environment, so that the external hydrostatic pressure acts on the internal high-concentration electrolyte solution through the magnetic coupling piston pressure transmission mechanism. Driven by the superposition of pressure and osmotic pressure, cations in the internal solution selectively migrate to the external seawater through an ion-selective membrane. The selective transmembrane migration of cations creates a potential difference across the membrane, which is extracted through electrodes immersed in the internal solution and external seawater, and outputs direct current.

[0013] Furthermore, it also includes a concentration regeneration step: when the output voltage drops to a preset threshold, a reverse voltage is applied to the auxiliary electrode for a short time through an external circuit to electromigrate ions in the external seawater back into the cavity.

[0014] Furthermore, the concentration of the first electrolyte solution is 6M NaCl, the depth of the deep-sea environment is greater than 500 meters, and the hydrostatic pressure is greater than 5MPa.

[0015] An innovative deep-sea communication beacon incorporates an ion energy power generation device driven by deep-sea hydrostatic pressure as its in-situ power source.

[0016] The advantages of this invention are: 1) No moving parts; the entire power generation process does not rely on any rotating or reciprocating machinery, there is no wear or risk of dynamic seal leakage, and it can operate without maintenance for more than ten years in the deep sea environment; 2) Unaffected by ocean currents and water quality; utilizing deep-sea hydrostatic pressure rather than uncertain environmental parameters such as wind, waves, and currents, deployment locations are not restricted; 3) Avoiding silt damage; the device is suspended in a clean water layer, with no bottom contact and no external mechanical structure, fundamentally solving the problem of deep-sea silt accumulation; 4) Modular and scalable; the output power of a single module is in the hundreds of milliwatts range, and can be expanded to the watts or even kilowatts range through multi-module series and parallel arrays, suitable for different needs from micro beacons to large base stations; 5) Low cost and small size; the core materials are membranes and electrodes, without expensive large mechanical parts, and the mass production cost is lower than that of a water turbine or thermoelectric power generation system of the same power. 6) Environmentally friendly; no emissions, no noise, no electromagnetic interference, and negligible changes in ion concentration in seawater. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1This is a schematic diagram of the structure of an ion energy power generation device driven by deep-sea hydrostatic pressure according to the present invention.

[0019] Figure 2 This is a cross-sectional view of the gradient multilayer composite membrane of an ion energy power generation device driven by deep-sea hydrostatic pressure according to the present invention.

[0020] Figure 3 This is a schematic diagram illustrating the principle of pressure-driven ion transport in an ion energy power generation device based on deep-sea hydrostatic pressure according to the present invention.

[0021] Figure 4 The simulated curves of ion current and output voltage as a function of deep-sea pressure are shown for an ion energy power generation device driven by deep-sea hydrostatic pressure according to the present invention.

[0022] Figure 5 This is a circuit connection diagram of a module array combination of an ion energy power generation device driven by deep-sea hydrostatic pressure according to the present invention.

[0023] Figure 6 This is an architectural diagram illustrating an application example of an ion energy power generation device driven by deep-sea hydrostatic pressure in a deep-sea beacon according to the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] like Figures 1 to 6 The illustrated ion energy power generation device based on deep-sea hydrostatic pressure includes... The pressure-resistant sealed cavity is filled with a first electrolyte solution, the ion concentration of which is higher than that of the seawater outside the pressure-resistant sealed cavity.

[0027] At least one ion-selective membrane assembly is installed on the wall of the pressure-resistant sealed cavity, allowing selective transmembrane migration of cations in the first electrolyte solution.

[0028] The magnetically coupled piston pressure transmission mechanism transmits the hydrostatic pressure of external seawater to the pressure-resistant sealed cavity, ensuring that the pressure of the first electrolyte solution is no greater than that of the external seawater, thereby driving ions to migrate across the membrane.

[0029] The first electrode is disposed inside the pressure-resistant sealed cavity and is in electrical contact with the first electrolyte solution.

[0030] The second electrode is located outside the pressure-resistant sealed cavity and is in electrical contact with seawater.

[0031] An external circuit, connecting the first electrode and the second electrode, is used to collect the current generated by ion migration.

[0032] The ion-selective membrane module is a gradient multilayer nanocomposite membrane, which includes a high-strength porous support layer, an intermediate transition layer and a functional separation layer from bottom to top. The functional separation layer is assembled by covalent cross-linking of metal-organic framework nanocrystals and graphene oxide nanosheets, and has regular sub-nanometer ion channels.

[0033] The metal-organic framework is UiO-66-NH2; the thickness of the functional separation layer is 50 nm to 500 nm, and the channel size is 0.3 nm to 1.0 nm.

[0034] It also includes a concentration regeneration subsystem, consisting of an auxiliary electrode, a programmable power supply, and a control unit, which is used to pump ions from the external seawater back into the cavity through reverse electrodialysis when the internal concentration decreases, thereby restoring the concentration gradient.

[0035] It also includes a suspended mooring system, which consists of a buoyancy carrier and counterweights, allowing the entire device to be suspended at a depth of 500 to 1000 meters.

[0036] A method for generating electricity using deep-sea hydrostatic pressure-driven ion energy, applied to a device for generating electricity using deep-sea hydrostatic pressure-driven ion energy; comprising the following steps: The pressure-resistant sealed cavity is placed in a deep-sea environment, so that the external hydrostatic pressure acts on the internal high-concentration electrolyte solution through the magnetic coupling piston pressure transmission mechanism. Driven by the superposition of pressure and osmotic pressure, cations in the internal solution selectively migrate to the external seawater through an ion-selective membrane. The selective transmembrane migration of cations creates a potential difference across the membrane, which is extracted through electrodes immersed in the internal solution and external seawater, and outputs direct current.

[0037] It also includes a concentration regeneration step: when the output voltage drops to a preset threshold, a reverse voltage is applied to the auxiliary electrode for a short time through an external circuit to electromigrate ions from the external seawater back into the cavity.

[0038] The concentration of the first electrolyte solution is 6M NaCl, and the deep-sea environment is at a depth greater than 500 meters and a hydrostatic pressure greater than 5 MPa.

[0039] A deep-sea communication beacon includes an ion energy power generation device driven by deep-sea hydrostatic pressure as an in-situ power source.

[0040] Specifically: 1. Pressure-resistant sealed cavity system The pressure-resistant sealed cavity is made of TC4 titanium alloy and has an internal volume of 0.5L to 5L. The cavity is filled with a first electrolyte solution, NaCl, with an ion concentration of 6M, higher than that of the external seawater. The cavity is equipped with a magnetically coupled piston pressure transmission mechanism to transfer the external deep-sea hydrostatic pressure to the internal solution, maintaining a dynamic balance between the internal solution pressure and the external seawater pressure. A titanium alloy bracket is located at the bottom of the cavity, on which a solid NaCl crystal block is placed. The bracket has through holes to ensure free flow of the solution. The solid NaCl crystal block is insulated from the electrodes.

[0041] During normal power generation, the Na in the internal solution + Due to the continuous consumption caused by selective transmembrane migration, the solution tends to become unsaturated, and solid NaCl continuously dissolves, replenishing the consumed Na. + This allows the internal solution to maintain a concentration near saturation for an extended period. For every 1 mole of Na that migrates... + (Corresponding to 96485 coulombs of electricity), that is, 1 mole of solid NaCl dissolves into the solution. This process is a purely physical dissolution, which does not consume electrical energy and can significantly extend the single regeneration cycle.

[0042] Once the solid NaCl crystal block is completely consumed, the system automatically switches to electrodialysis regeneration mode, applying a reverse voltage through the auxiliary electrode to remove NaCl from the external seawater. + The pump returns the material to the chamber, restoring the concentration gradient. These two mechanisms work together to achieve long-term maintenance-free operation.

[0043] 2. Gradient multilayer nanocomposite ion-selective membrane module At least one membrane module is mounted on the cavity wall. The membrane module adopts a gradient multilayer composite structure, which includes, from bottom to top (from outside to inside): a high-strength porous support layer made of PTFE nanofiber mesh, an intermediate transition layer composed of cross-linked polyvinyl alcohol and nano-silica, and a top functional separation layer.

[0044] The functional separation layer is assembled from metal-organic framework UiO-66-NH2 nanocrystals and graphene oxide nanosheets via covalent cross-linking, forming a continuous thin film with regular sub-nanometer ion channels. The thickness of the functional separation layer ranges from 50 nm to 500 nm, and the channel size is precisely controlled within the range of 0.3 nm to 1.0 nm by selecting the MOF pore size and GO interlayer spacing, achieving the desired Na+ ion channel size. + Selective permeability to Mg 2+ and Ca 2+ The retention rate is greater than 90%.

[0045] The gradient structure is prepared by a combination of layer-by-layer spraying or spin coating and in-situ interfacial polymerization, so that the overall film thickness does not exceed 50 μm and the ion selectivity decreases by no more than 20% under 10 MPa hydrostatic pressure.

[0046] 3. Electrodes and Current Harvesting System The first electrode is located inside the sealed cavity and is completely immersed in the first electrolyte solution. The electrode material is a platinum-plated titanium mesh.

[0047] The second electrode, made of titanium mesh, is positioned outside the sealed cavity and in direct contact with seawater. The external circuit connects the first and second electrodes via a watertight connector to a load or energy storage device. A voltage regulator module and a maximum power point tracking controller are connected in series in the circuit.

[0048] 4. Pressure Equilibrium and Concentration Regeneration Module One end of the magnetically coupled piston pressure transmission mechanism is connected to the external seawater, while the other end acts on the first electrolyte solution, uniformly transmitting the deep-sea pressure to the internal solution and preventing excessive instantaneous pressure difference shocks across the membrane.

[0049] The concentration regeneration subsystem consists of an auxiliary electrode and a programmable power supply. When the internal concentration decreases, causing the output voltage to fall below a threshold, the controller briefly applies a reverse voltage, using the electrodialysis effect to remove Na+ from the external seawater. + The pump returns the material to the chamber, restoring the concentration gradient. This regeneration process is performed every few weeks to months, with each cycle consuming less than 5% of the unit's total output in energy.

[0050] 5. Suspension anti-siltation and mooring system The entire device is mounted on a streamlined buoyancy carrier made of glass microsphere composite foam deep-sea buoyancy material, providing net buoyancy to suspend the device at depths of 500 to 1000 meters. It utilizes the permanent density gradient present in this depth range to achieve passive vertical stability. The device automatically aligns with ocean currents through its streamlined shape to reduce drag, and a streamlined counterweight suspended below lowers the center of gravity and provides attitude damping. It is independent of seabed anchor points and allows for limited horizontal drift to adapt to changes in ocean currents.

[0051] Example 1: Single-module prototype device (laboratory scale) (1) Device construction The cavity is a titanium alloy cylinder with an inner diameter of 60mm, a length of 100mm, and a wall thickness of 5mm. One end is equipped with a flange for installing the membrane module, and the other end is equipped with a magnetically coupled piston pressure transmission mechanism. The internal volume is approximately 280mL.

[0052] The internal solution is a 6M NaCl solution with a conductivity of approximately 0.2 S / cm.

[0053] The membrane module has an effective area of ​​12.5 cm² and a diameter of 40 mm. The membrane structure is a three-layer composite. The support layer is a PTFE nanofiber membrane with a thickness of 25 μm, a porosity of 80%, and a tensile strength of 50 MPa. The middle layer is a glutaraldehyde-crosslinked PVA / SiO₂ membrane with a thickness of 5 μm. The functional layer is a UiO-66-NH₂@GO composite membrane with a thickness of 200 nm, where the UiO-66-NH₂ particles are approximately 50 nm in size, and the GO interlayer spacing is achieved through Li₂. + The intercalation was fixed at 0.45 nm. The preparation method was as follows: GO and UiO-66-NH2 were mixed at a mass ratio of 1:3 and ultrasonically dispersed, then vacuum filtered onto the support layer, vacuum dried at 80℃ for 12 hours, and then soaked in 1M LiCl solution for exchange.

[0054] The internal electrode is a platinum-plated titanium mesh, 35 mm in diameter and 0.5 mm thick, with a platinum layer thickness of 1 μm. The external electrode is a titanium mesh, exposed to seawater.

[0055] Place the device in a high-pressure autoclave, fill it with artificial seawater, pressurize it to 10 MPa, and maintain the pressure.

[0056] (2) Test results Under conditions of 10MPa and 5℃, the open-circuit voltage remained stable between 0.75V and 0.82V, consistent with the theoretical value of 0.79V. The measured short-circuit current density was approximately 1.2mA / cm². The maximum output power point occurred at 0.45V and 0.8mA / cm², corresponding to a power density of 0.36mW / cm², with a total output power of approximately 4.5mW for a single module.

[0057] After 500 hours of continuous operation, the output power dropped to 92% of the initial value, and no obvious cracks or delamination were observed on the membrane surface, proving that the gradient composite structure has good mechanical stability under a high pressure of 10 MPa.

[0058] (3) Conclusion This embodiment verifies the feasibility of pressure-driven ion energy power generation and proves that the gradient multilayer MOF / GO composite membrane can withstand 10MPa hydrostatic pressure, initially meeting the requirements for deep-sea use.

[0059] Example 2: Integrated power supply for deep-sea communication beacons (1) System Design To provide continuous power to a deep-sea dual-resonant magnetically coupled communication beacon with an average power consumption of 150mW, 12 single modules from Example 1 are connected in a 4-series-3-parallel configuration, with a total output capacity of approximately 3.0V open-circuit voltage and a maximum power of approximately 1.5W.

[0060] The power management circuitry includes an MPPT controller based on the perturbation-observation method, a 3.7V / 10Ah lithium-ion battery pack, and 3.3V and 5V regulated outputs.

[0061] All modules are integrated into a titanium alloy spherical shell with a diameter of 200 mm and a height of 300 mm. The shell is equipped with multiple magnetically coupled piston pressure transmission mechanisms. External seawater contacts the outer electrodes and the outside of the membrane assembly through reserved channels.

[0062] (2) Deployment plan The device is suspended at a target depth of 500 to 1000 meters by buoyancy balance between a buoyant carrier and a counterweight. The outer shell is coated with a superhydrophobic coating of fluorinated carbon nanotubes and is equipped with a low-frequency vibration of 10 seconds per week to prevent biofouling, driven by an internal eccentric motor.

[0063] (3) Life expectancy Without active concentration regeneration, the output voltage drops by approximately 35% when the internal 6M NaCl solution concentration decreases to approximately 2.0M. Initial Na... + The total number of moles is 0.28 L × 6 mol / L = 1.68 mol. The steady-state outward flux Jc is approximately 2 × 10⁻⁶. -5 12 modules with a flux of mol / (cm²·s) × 12.5cm², total flux approximately 3 × 10⁻⁶ -3 mol / s. The Na required to reduce the concentration from 6 M to 2.0 M is [amount missing]. + The amount is 4 mol / L × 0.28 L = 1.12 mol, and it is calculated that the concentration will drop to this level in approximately 94 days. In actual intermittent operation mode, the beacon does not continuously discharge at full load, and its actual lifespan can reach 10 to 21 months. For a longer lifespan, the concentration regeneration function can be enabled. Reverse powering for 2 hours per month consumes an additional 0.5 Wh of energy, which is less than 0.05% of the device's monthly power generation and can be ignored.

[0064] Adding solid NaCl compression blocks in the initial state can further extend the service life. Taking a 6M NaCl solution with a volume of 0.28L as an example, if the concentration is increased from 6M to the saturation concentration of 6.1M, each module needs to be replenished with approximately 0.1mol / L × 0.28L = 0.028mol NaCl (approximately 1.6g), and 12 modules will require approximately 19g in total. If the NaCl consumed throughout the entire working cycle needs to be...+ (Approximately 1.12 mol / module × 12 ≈ 13.44 mol, approximately 786 g) If all components are pre-placed in solid form, a single salt addition can support a complete discharge cycle from 6 M to 2.0 M without the need to initiate electrodialysis regeneration midway.

[0065] (4) Cost and competitiveness A single power module comprises 12 sub-modules, control circuitry, and a battery. Its mass production BOM cost is lower than that of traditional deep-sea battery packs with equivalent power. Traditional deep-sea battery packs require annual recycling and replacement, while the device of this invention requires no maintenance for five years after deployment, demonstrating a significant life-cycle cost advantage.

[0066] Example 3: A method for large-scale preparation of gradient multilayer composite films (1) Pretreatment of support layer A PTFE nanofiber membrane with a width of 30 cm and a thickness of 25 μm was ultrasonically cleaned in anhydrous ethanol for 10 minutes, and then hydrophilically modified by treating it with 100 W O2 plasma for 5 minutes in a plasma treatment instrument.

[0067] (2) Coating of intermediate transition layer A 5wt% polyvinyl alcohol aqueous solution with a polyvinyl alcohol degree of 98% was prepared. 2wt% nano-silica (particle size 20nm) and 0.5wt% glutaraldehyde were added, and the mixture was stirred until homogeneous and allowed to stand to remove bubbles. The solution was then coated onto a PTFE support layer using a slit coating head, resulting in a wet film thickness of 50μm. The film was dried on a hot plate at 80℃ for 30 minutes to obtain a cross-linked PVA / SiO2 interlayer with a dry film thickness of approximately 5μm.

[0068] (3) MOF / GO functional layer assembly Weigh 0.3 g of UiO-66-NH2 nanocrystals with an average particle size of 50 nm and 0.1 g of graphene oxide with a sheet diameter of 1 μm to 5 μm and 1 to 3 layers, disperse them in 100 mL of deionized water, and sonicate for 2 hours to form a uniform dispersion. Add 1 mL of 1M NaOH to adjust the pH to 10, and then sonicate for another 30 minutes.

[0069] The dispersion was deposited onto a membrane with an intermediate layer using a vacuum filtration device at a rate of 0.5 mL / min, with the deposition rate controlled to achieve the target thickness of 200 nm. After filtration, the membrane was dried in a vacuum oven at 80 °C for 12 hours.

[0070] (4) Post-treatment and ion activation The dried membrane was immersed in 1M LiCl solution for 24 hours to exchange Na between the GO layers. + For Li + Then rinse the surface with deionized water until neutral. Vacuum dry at 60°C for later use.

[0071] The gradient composite membrane prepared by the above method has a measured tensile strength of 68 MPa. After continuous testing under a hydrostatic pressure of 10 MPa for 72 hours, the Na... + Flux decrease less than 5%, Mg 2+ The retention rate remained above 92%.

[0072] The working principle of this invention is as follows: In the deep-sea environment, hydrostatic pressure is not only an environmental load that needs to be resisted, but can also be utilized as a pump source to drive directional ion transport. An electrolyte solution with a higher ion concentration than the external seawater is pre-placed within a sealed cavity, and a nanochannel membrane that allows only cations to pass through is installed. The deep-sea pressure forces cations to migrate outward across the membrane, while anions are blocked within the cavity, thereby forming a stable membrane potential across the membrane. This potential difference is extracted through electrodes immersed in the inner and outer solutions, thus providing external power.

[0073] Unlike reverse electrodialysis, the driving force of this invention comes from the superposition effect of external hydrostatic pressure and internal osmotic pressure, rather than simply relying on the initial concentration gradient. Unlike pressure-delayed osmosis, this invention directly outputs current instead of first converting it into mechanical energy to generate electricity, thus eliminating moving parts and parasitic energy consumption.

[0074] The above theoretical model and feasibility demonstration: For the cation exchange membrane in this device, under hydrostatic pressure difference and chemical potential difference Driven by both factors, cation flux and solvent flux It obeys the linear phenomenological relation in irreversible thermodynamics:

[0075]

[0076] in The ionic conductivity is... The hydraulic permeability coefficient, = This is the coupling coefficient (Onsager reciprocal relation). This represents the chemical potential difference of the cations.

[0077] When the external circuit is open, ion migration establishes a potential difference E (membrane potential) across the membrane. According to the extended form of the Nernst-Planck equation, the steady-state membrane potential can be expressed as:

[0078] in This represents the partial molar volume of water (approximately 18 cm³ / mol). At a depth of 1000 meters, ΔP ≈ 10 MPa, and the second contribution is approximately... Although this value is much smaller than the first term (approximately 59 mV per decade concentration ratio at room temperature), the key is that the pressure term persists, preventing ion transmembrane migration from reaching equilibrium and stopping—this is the essential innovation of this invention that distinguishes it from traditional static concentration cells.

[0079] 2. Estimation of steady-state current density and output power Under closed-loop conditions, the ion current density *i* and the overpotential *η* satisfy a Butler-Volmer type relationship. Neglecting electrode overpotential, the current density is approximately proportional to the net ion flux.

[0080] Where d is the membrane thickness. For general cation exchange membranes, / d is usually in 10 -4 -10 -3 On the order of S / cm. Typical parameters: , (seawater), (5℃) , ,but: Chemical potential term:

[0081] Stress item:

[0082] Total driving force: approximately 3898 J / mol, of which the pressure term contributes approximately 4.6%. Pick ,but Corresponding current density When the membrane area of ​​a single module is 100cm², it can output approximately 195mA, with an open-circuit voltage of approximately 0.8V and a theoretical output power of approximately 156mW.

[0083] 3. Quantitative gap in membrane pressure resistance The above theoretical estimation assumes that the membrane maintains structural integrity and ion selectivity under a hydrostatic pressure of 10 MPa. However, the burst strength of current general-purpose electrodialysis membranes is typically only 0.5-0.6 MPa, nearly two orders of magnitude lower than the requirements for deep-sea applications. This is precisely the core engineering challenge of this invention, and the objective that the gradient multilayer composite membrane technology proposed in this invention aims to overcome.

[0084] 4. Theoretical Conclusions Based on the fundamental equations of irreversible thermodynamics and electrochemistry, the pressure-driven ion energy generation described in this invention is physically self-consistent, with an expected power density reaching the milliwatt-per-square-centimeter level, sufficient to provide in-situ energy for low-power deep-sea beacons. The high-pressure resistance of the membrane material is the core problem this invention addresses.

[0085] Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. An ion energy power generation device driven by deep-sea hydrostatic pressure, characterized in that: include A pressure-resistant sealed cavity is filled with a first electrolyte solution, the ion concentration of which is higher than that of the seawater outside the pressure-resistant sealed cavity. At least one ion-selective membrane module is installed on the wall of the pressure-resistant sealed cavity, allowing selective transmembrane migration of cations in the first electrolyte solution; The magnetically coupled piston pressure transmission mechanism transmits the hydrostatic pressure of external seawater to the pressure-resistant sealed cavity, so that the first electrolyte solution is subjected to a pressure not greater than that of the external seawater, thereby driving the ions to migrate across the membrane. The first electrode is disposed inside the pressure-resistant sealed cavity and is in electrical contact with the first electrolyte solution; The second electrode is located outside the pressure-resistant sealed cavity and is in electrical contact with seawater. An external circuit, connecting the first electrode and the second electrode, is used to collect the current generated by ion migration.

2. The ion energy power generation device based on deep-sea hydrostatic pressure as described in claim 1, characterized in that: The ion-selective membrane assembly is a gradient multilayer nanocomposite membrane, which includes, from bottom to top, a high-strength porous support layer, an intermediate transition layer, and a functional separation layer; the functional separation layer is assembled by covalent cross-linking of metal-organic framework nanocrystals and graphene oxide nanosheets, and has regular sub-nanometer ion channels.

3. The ion energy power generation device based on deep-sea hydrostatic pressure as described in claim 2, characterized in that: The metal-organic framework is UiO-66-NH2; the thickness of the functional separation layer is 50 nm to 500 nm, and the channel size is 0.3 nm to 1.0 nm.

4. The ion energy power generation device based on deep-sea hydrostatic pressure as described in claim 1, characterized in that: It also includes a concentration regeneration subsystem, consisting of an auxiliary electrode, a programmable power supply, and a control unit, which is used to pump ions from the external seawater back into the cavity through reverse electrodialysis when the internal concentration decreases, thereby restoring the concentration gradient.

5. The ion energy power generation device based on deep-sea hydrostatic pressure as described in claim 1, characterized in that: It also includes a suspended mooring system, which consists of a buoyancy carrier and a counterweight, allowing the entire device to be suspended at a depth of 500 to 1000 meters.

6. A method for generating electricity using ion energy driven by deep-sea hydrostatic pressure, applied to the device according to any one of claims 1 to 5, characterized in that: Includes the following steps: The pressure-resistant sealed cavity is placed in a deep-sea environment, so that the external hydrostatic pressure acts on the internal high-concentration electrolyte solution through the magnetic coupling piston pressure transmission mechanism. Driven by the superposition of pressure and osmotic pressure, cations in the internal solution selectively migrate to the external seawater through an ion-selective membrane. The selective transmembrane migration of cations creates a potential difference across the membrane, which is extracted through electrodes immersed in the internal solution and external seawater, and outputs direct current.

7. A method for generating electricity using ion energy driven by deep-sea hydrostatic pressure according to claim 6, characterized in that: It also includes a concentration regeneration step: when the output voltage drops to a preset threshold, a reverse voltage is applied to the auxiliary electrode for a short time through an external circuit to electromigrate ions from the external seawater back into the cavity.

8. A method for generating electricity using ion energy driven by deep-sea hydrostatic pressure according to claim 6, characterized in that: The concentration of the first electrolyte solution is 6M NaCl, the deep-sea environment is at a depth greater than 500 meters, and the hydrostatic pressure is greater than 5MPa.

9. A deep-sea communication beacon, characterized in that: The power generation device comprising any one of claims 1 to 5 is used as an in-situ power source.

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