A seawater metal-air battery state of charge monitoring system based on optical fiber sensing and a preparation method and application thereof

Abstract

The application relates to a seawater metal-air battery state of charge monitoring system based on optical fiber sensing and a preparation method and application thereof, and belongs to the technical field of battery monitoring. The monitoring system comprises a seawater metal-air battery monomer, an optical fiber sensing unit, a mounting structure and a spectrum demodulation module. The seawater metal-air battery monomer comprises a metal electrode consumed in a discharge reaction. The optical fiber sensing unit comprises at least one optical fiber, and a fiber Bragg grating is arranged on the optical fiber. The mounting structure is arranged on the metal electrode and is used for fixing at least a part of the optical fiber in a pre-stretched or bent state in the interior or surface of the metal electrode and arranging the fiber Bragg grating in the fixing area. The spectrum demodulation module is connected with the optical path of the optical fiber. The monitoring system provided by the application overcomes the challenge that traditional electrical monitoring means is prone to failure in a high-corrosion seawater environment and cannot directly reflect the consumption of a metal electrode entity, and realizes in-situ, real-time and accurate monitoring of SOC.

Description

Technical Field

[0001] This application relates to the field of battery monitoring technology, and in particular to a state-of-charge monitoring system for seawater metal-air batteries based on fiber optic sensing, its preparation method, and its application. Background Technology

[0002] Seawater metal-air batteries (SMABs) are a novel type of electrochemical energy storage device that uses seawater as the electrolyte, active metals such as magnesium, aluminum, and zinc as the anode, and oxygen as the cathode active material. These batteries offer advantages such as high energy density, simple structure, low cost, and environmental friendliness, making them particularly suitable as power supply units for underwater unmanned vehicles, marine observation networks, and emergency power sources. They have broad application prospects in the field of marine power supply systems. In practical applications, the state of charge (SOC) is a key parameter for measuring the remaining battery capacity and a core monitoring indicator for ensuring reliable system operation and preventing sudden power outages. For seawater metal-air batteries, the discharge process involves the continuous electrochemical dissolution of the anode metal (e.g., Mg → Mg). 2+ + 2e - When the metal electrodes are completely depleted, the battery reaction terminates, and the charge returns to zero. Therefore, the ability to accurately and in real-time monitor SOC is directly related to the operational safety and energy management efficiency of marine equipment. Currently, traditional battery SOC monitoring technologies are mainly based on electrical parameter measurements, such as the ampere-hour integration method, open-circuit voltage method, and electrochemical impedance spectroscopy. However, in the specific application scenario of seawater metal-air batteries, the above methods face severe challenges: First, seawater is a complex electrolyte solution with high salinity, high corrosiveness, and dynamic changes in conductivity. Traditional electrical sensors (such as voltage probes and current transformers) are prone to electrochemical corrosion under long-term immersion conditions, leading to signal drift or even failure, making it difficult to guarantee system reliability. Second, the discharge process of seawater metal-air batteries involves the physical consumption and geometric changes of electrode materials. Traditional electrical parameter methods can only indirectly estimate the charge and cannot directly reflect the essential physical quantity of "remaining metal," resulting in cumulative errors, especially at the end of the discharge phase where the critical point of charge depletion cannot be accurately indicated.

[0003] In recent years, some studies have attempted to assess metal consumption using physical methods such as ultrasonic detection and weighing. However, the former is limited by the complex seabed environment and bubble interference, while the latter is difficult to achieve in-situ, real-time monitoring, and neither has been widely applied in practical engineering. Fiber optic sensing technology, due to its resistance to electromagnetic interference, corrosion resistance, and small size, has been widely used in structural health monitoring. However, its application in monitoring the metal electrode consumption process of seawater metal-air batteries, particularly using the fiber optic stress changes caused by electrode consumption to invert SOC (State of Charge), has not yet been publicly reported. Summary of the Invention

[0004] In view of this, this application provides a state of charge (SOC) monitoring system for seawater metal-air batteries based on fiber optic sensing, its preparation method, and its application. This monitoring system overcomes the challenges of traditional electrical monitoring methods being prone to failure in highly corrosive seawater environments and failing to directly reflect the physical consumption of metal electrodes. It utilizes fiber optic sensing technology to achieve in-situ, real-time, and accurate SOC monitoring, thereby improving the reliability of energy management for seawater metal-air batteries and effectively overcoming the shortcomings of the aforementioned prior art.

[0005] The first aspect of this application provides a state-of-charge monitoring system for seawater metal-air batteries based on fiber optic sensing, including a seawater metal-air battery cell, a fiber optic sensing unit, an installation structure, and a spectral demodulation module;

[0006] The seawater metal-air battery cell includes an electrochemical reaction system using seawater as the electrolyte, and the electrochemical reaction system includes a metal electrode consumed in the discharge reaction.

[0007] The fiber optic sensing unit includes at least one fiber optic cable, on which a fiber Bragg grating is provided;

[0008] The mounting structure is disposed on the metal electrode and is used to fix at least a portion of the optical fiber in a pre-stretched or bent state to the interior or surface of the metal electrode, and to place the fiber Bragg grating in the fixed area;

[0009] The spectral demodulation module is connected to the optical path of the optical fiber and is used to receive and analyze the wavelength signal of the reflected light;

[0010] When the metal electrode is consumed to the installation position of the fiber Bragg grating as the discharge reaction in seawater proceeds, the installation structure fails, causing the optical fiber to change from a pre-stretched or bent state to a relaxed state, which in turn causes the reflected wavelength of the fiber Bragg grating to shift. The spectral demodulation module determines the state of charge of the seawater metal-air battery by detecting the wavelength shift.

[0011] Preferably, the metal electrode has a plate-like or block-like structure, and the material of the metal electrode is selected from magnesium, zinc, and aluminum.

[0012] Specifically, the seawater metal-air battery cell includes seawater as the electrolyte and at least one metal anode consumed in the discharge reaction. The cathode uses a commercially available 20% Pt / C catalyst supported on commercial carbon paper. The metal anode is made of magnesium, zinc, or aluminum. The seawater is collected directly from the sea and filtered to remove sediment before use.

[0013] Preferably, the mounting structure includes a channel pre-formed inside the metal electrode, the optical fiber passes through the channel, and the path of the channel is non-linear, so that the optical fiber remains bent within the channel and generates a preload.

[0014] The aperture of the channel is 0.1~0.5 mm; the non-linear shape is serpentine and / or U-shaped. The diameter of the optical fiber is smaller than the aperture to facilitate insertion. Preferably, the aperture is 0.2~0.3 mm, which ensures both free insertion of the optical fiber and effective support of the channel wall for the optical fiber.

[0015] Preferably, the mounting structure further includes a microgroove formed on the surface of the metal electrode, the optical fiber being fixed in the microgroove by an encapsulation layer or a clamping sheet, the microgroove having a channel diameter of 0.3 mm, and bending the optical fiber to generate a preload.

[0016] Specifically, the pre-stretch strain of the optical fiber within the mounting structure is 1000~3000 με to ensure that the optical fiber is in a fully stretched state, so that a sufficiently significant wavelength shift signal is generated when the metal is consumed to the critical point.

[0017] Preferably, the fiber optic sensing unit includes multiple fiber Bragg gratings; the mounting structure has multiple fixed points at different depths of the metal electrode, with each fiber Bragg grating correspondingly positioned at a fixed point at a different depth, used to sequentially generate wavelength shift signals as the metal electrode is consumed layer by layer, thereby achieving graded or continuous monitoring of the state of charge. Considering the gradual nature of metal electrode consumption, it is more preferable to use an array of multiple fiber Bragg gratings arranged along the electrode thickness direction, but other distributed arrangements are also applicable to this application.

[0018] Preferably, the spectral demodulation module includes a spectral analyzer or a fiber Bragg grating demodulator for real-time tracking of the peak reflection wavelength change of the fiber Bragg grating. A high-resolution spectral analyzer is preferred to capture minute wavelength shift signals.

[0019] Preferably, the fiber Bragg grating is a chirped fiber grating or a long-period fiber grating to enhance sensitivity to spectral changes during stress release.

[0020] A second aspect of this application also provides a method for monitoring the state of charge (SOC) of a seawater metal-air battery based on fiber optic sensing, applied to the aforementioned fiber optic sensing-based seawater metal-air battery SOC monitoring system, comprising the following steps:

[0021] (1) Before the seawater metal-air battery discharges, the reflection wavelength λ0 of the fiber Bragg grating in the initial state is calibrated to correspond to a state of charge of 100%;

[0022] (2) During the discharge process of the seawater metal-air battery, the reflection wavelength λ of the fiber Bragg grating is monitored in real time;

[0023] (3) When the reflected wavelength is detected to change abruptly from λ0 to λ1 and the offset exceeds the preset threshold, it is determined that the metal electrode at the location of the fiber Bragg grating has been exhausted and the corresponding state of charge value is output.

[0024] (4) Calculate the remaining battery capacity based on the preset wavelength offset-state of charge mapping relationship.

[0025] Preferably, in step (3), the preset threshold is a wavelength offset exceeding 0.1 nm. Considering the typical resolution of the fiber optic demodulator, 0.05 nm is more preferably used as the preset threshold, but other preset threshold settings are also applicable to this application.

[0026] In step (4), the wavelength offset-state of charge mapping relationship is established through a pre-calibration experiment: the metal electrodes with different consumption levels are weighed, and the wavelength offset of the corresponding fiber Bragg grating is recorded. The correspondence between the wavelength offset and the metal consumption is then fitted.

[0027] The third aspect of this application also provides the application of the aforementioned fiber optic sensing-based seawater metal-air battery state-of-charge monitoring system in marine equipment energy management.

[0028] Compared with the prior art, this application has the following advantages:

[0029] 1. The core of this application lies in using fiber optic sensing technology to convert the physical consumption of metal electrodes during the discharge process of seawater metal-air batteries into wavelength shift signals caused by fiber optic stress release, thereby achieving direct, in-situ monitoring of the state of charge.

[0030] 2. This application uses optical fiber as the sensing element. The optical fiber itself is an insulating silicon dioxide material, which is completely unaffected by the high salt and high corrosion environment of seawater. This solves the technical problem that traditional electrical sensors are prone to corrosion and failure in marine environments, and significantly improves the long-term reliability and stability of the monitoring system.

[0031] 3. This application uses a prefabricated installation structure to keep the optical fiber in a bent state. When the metal electrode is consumed to this position, the stress in the optical fiber is suddenly released, and the wavelength signal changes abruptly. This "trigger-based" monitoring principle directly reflects the physical consumption of the metal electrode, avoiding the cumulative errors caused by traditional indirect calculation methods such as the ampere-hour integration method. In particular, it can accurately indicate the critical point of power depletion at the end of the discharge.

[0032] 4. By deploying multiple fiber Bragg gratings at different depths of the metal electrode, this application can achieve graded or continuous monitoring of the metal consumption process, thereby obtaining a more refined SOC change curve and providing richer data support for battery management.

[0033] 5. The system structure of this application is simple, and the fiber optic sensing unit is easy to deploy and network. It can realize distributed monitoring of a single cell or a battery stack composed of multiple cells, and has good engineering application prospects.

[0034] 6. In summary, this application overcomes the challenges of battery monitoring in seawater environments, enhances the energy management reliability of seawater metal-air batteries, and promotes the practical application of seawater metal-air batteries in marine equipment. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the state-of-charge monitoring system for seawater metal-air batteries based on fiber optic sensing, as described in this application.

[0037] Figure 2 This is a schematic diagram of the assembly of the seawater metal-air battery of this application;

[0038] Figure 3 A schematic diagram of a magnesium electrode structure with prefabricated serpentine channels constructed according to Embodiment 1 of this application;

[0039] Figure 4 This is a schematic diagram of a magnesium electrode structure with prefabricated U-shaped channels constructed according to Embodiment 2 of this application;

[0040] Figure 5 A schematic diagram of a magnesium electrode structure with pre-fabricated channels of different depths constructed for Embodiment 3 of this application;

[0041] Figure 6 A schematic diagram of the magnesium electrode structure for the fiber optic deployment method without pretension constructed in Comparative Example 1 of this application;

[0042] Figure 7 This is a structural diagram of the seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing, as described in this application.

[0043] Explanation of reference numerals in the attached figures:

[0044] 1. Seawater metal-air battery cell;

[0045] 11. Cathode placement area; 12. Flowing electrolyte; 13. Anode placement area;

[0046] 2. Optical fiber;

[0047] 21. Magnesium metal anode with pre-formed channels; 22. Fiber optic sensing; 23. Fiber optic FBG segment;

[0048] 3. Installation structure;

[0049] 4. Spectral demodulation module. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.

[0052] In the following examples and comparative examples, unless otherwise specified, all raw materials can be prepared by commercial purchase or conventional methods.

[0053] like Figure 7 As shown, this application provides a state-of-charge (SOC) monitoring system for seawater metal-air batteries based on fiber optic sensing. First, a magnesium anode 21 with pre-formed channels is prepared. Then, a fiber Bragg grating (FBG) is inserted into the micro-channels, and the fiber optic cable 2 (including a fiber optic sensor 22 and a fiber optic FBG segment 23) is kept in a pre-tightened bent state. Subsequently, the metal electrodes with the fiber optic cable 2 are assembled into a seawater metal-air battery cell 1 (including a cathode placement 11, a flowing electrolyte 12, and an anode placement 13). Finally, the fiber optic cable 2 is connected to a spectral demodulation module 4 to monitor the reflected wavelength signal in real time. During battery discharge, the metal electrodes are gradually consumed. When the metal electrodes are consumed to the fiber placement position, the fiber changes from a bent and taut state to a relaxed state, causing a shift in the reflected wavelength of the fiber Bragg grating. The SOC of the battery can be determined by detecting the wavelength shift.

[0054] The "installation structure 3" can be selected according to actual needs and is not limited to the micro-channels selected in the following embodiments. Furthermore, based on the monitoring method proposed in this application, those skilled in the art can select different electrode materials and structures according to actual needs, and are not limited to the specific metal materials and channel parameters used in the following embodiments.

[0055] State of Charge (SOC) monitoring refers to the use of fiber Bragg gratings (FBGs) to detect strain and convert the physical loss of metal electrodes into wavelength shifts in optical signals. In the initial state (SOC = 100%), the optical fiber remains bent and pre-stressed within a pre-fabricated channel, and the FBG reflects light of a specific wavelength (λ0). As discharge progresses, the metal electrode gradually dissolves and thins. When the metal is consumed down to the channel wall, the constraint supporting the fiber bending disappears, and the fiber stress is released instantaneously, causing a change in the FBG pitch and a sudden change in the reflected wavelength (λ1). This design directly converts the degree of electrode material consumption into a quantitatively detectable optical signal, avoiding the corrosion and signal drift problems inherent in traditional electrical monitoring methods in seawater environments. Unlike traditional methods that rely on voltage and current to indirectly calculate SOC, this application directly monitors the remaining physical weight of the metal electrode, fundamentally solving the problem of accumulated errors. It is particularly suitable for accurately determining SOC = 0% at the end of discharge and has great potential to improve the energy management reliability of seawater metal-air batteries.

[0056] Example 1: SOC monitoring system based on magnesium electrode and FBG sensing

[0057] I. Methods for Building a Monitoring System

[0058] i. Preparation of pre-drilled channels in magnesium 21 metal anodes

[0059] Take a piece of pure magnesium metal plate (dimensions: 75 mm long × 25 mm wide × 2 mm thick; the actual reaction area of ​​the battery is 4.5 cm²). 2 A circular region was used as the anode of the seawater metal-air battery. A serpentine microchannel was pre-fabricated along the thickness direction of the magnesium plate using a mechanical drilling process. The channel diameter was 0.3 mm, and the channel path length was approximately 30 mm. The two ends of the channel opened onto the two sides of the magnesium plate to facilitate the insertion and exit of optical fibers. The processed magnesium plate was then sequentially sanded with sandpaper and ultrasonically cleaned with deionized water for 10 minutes to remove surface metal oxides and debris, and then dried for later use. Figure 3 This is a schematic diagram of a magnesium electrode structure with prefabricated serpentine channels constructed according to Embodiment 1 of this application.

[0060] ii. Deploy fiber optic sensors 22

[0061] Take a 100 mm long single-mode optical fiber with a fiber Bragg grating (FBG) marked in its middle (FBG segment 23, 20 mm long, initial center wavelength 1549.9 nm). Insert the fiber into one end of a hole in the magnesium plate surface and exit from the other end, positioning the FBG in the middle of the hole. During fiber insertion, apply a certain axial tension to keep the fiber taut and bent within the hole. Then, fix both ends of the fiber to the magnesium plate surface to prevent loosening or slippage.

[0062] iii. Assembling seawater metal-air battery cells 1

[0063] The magnesium electrode with FBG prepared above was used as the anode, and an electrode composite substrate loaded with Pt / C catalyst (carbon paper, nickel foam, and air diffusion film, with the catalyst loaded on the carbon paper side; specifically, the carbon paper, nickel foam, and air diffusion film were stacked one on top of the other, and then hot-pressed for 8 minutes at 80°C. Subsequently, a catalyst slurry (catalyst slurry: 5 mg catalyst + 980 μL tetraethyl ortho-ethyl alcohol + 20 μL Nafion film solution, ultrasonicated for 30 min) was drop-coated onto the carbon paper side) was used as the air cathode. The battery casing material was acrylic sheet, with an effective reaction area of ​​1 cm². 2 The battery has a circular area. After assembly, natural seawater is injected into the casing as an electrolyte to ensure the electrodes are completely submerged. Figure 2 This is a schematic diagram of the assembly of the seawater metal-air battery of this application.

[0064] iv. Connect the spectral demodulation system

[0065] Connect the fiber optic cable to the OSA spectrometer via a fiber optic patch cord, setting the scan range to 1545 nm to 1555 nm and the resolution to 0.02 nm. Simultaneously connect a computer for data acquisition and recording.

[0066] II. Testing Methods for Monitoring Systems

[0067] The assembled seawater metal-air battery cell 1 was placed in a constant indoor environment (26 ℃) and subjected to constant current discharge testing using a LAND battery testing system. The discharge voltage change curve over time was recorded in real time, and the discharge current density was set to 10 mA / cm². 2 (Based on the effective electrode area of ​​1 cm²) 2The calculation corresponds to a discharge current of 10 mA. Simultaneously, during the discharge process, the reflection spectrum and center wavelength changes of the FBG are recorded in real time using a spectrometer. Before the battery is injected with seawater and the circuit is connected, the initial center wavelength λ0 of the FBG is recorded, which corresponds to a battery state of charge (SOC) of 100%. In this embodiment, λ0 = 1550.12 nm.

[0068] like Figure 1 As shown, this embodiment of the method for monitoring the state of charge of seawater metal-air batteries based on fiber optic sensing includes the following steps:

[0069] (1) Before the seawater metal-air battery discharges, the reflection wavelength λ0 of the fiber Bragg grating in the initial state is calibrated to correspond to a state of charge of 100%;

[0070] (2) During the discharge process of the seawater metal-air battery, the reflection wavelength λ of the fiber Bragg grating is monitored in real time;

[0071] (3) When the reflected wavelength is detected to change abruptly from λ0 to λ1 and the offset exceeds the preset threshold, it is determined that the metal electrode at the location of the fiber Bragg grating has been exhausted and the corresponding state of charge value is output.

[0072] (4) Calculate the remaining battery capacity based on the preset wavelength offset-state of charge mapping relationship.

[0073] Specifically, in step (3), the preset threshold is a wavelength offset exceeding 0.1 nm;

[0074] In step (4), the wavelength offset-state of charge mapping relationship is established through a pre-calibration experiment: the metal electrodes with different consumption levels are weighed, and the wavelength offset of the corresponding fiber Bragg grating is recorded. The correspondence between the wavelength offset and the metal consumption is then fitted.

[0075] Example 2

[0076] The monitoring system provided in this embodiment can be referred to in Embodiment 1, except that the shape of the channel is U-shaped. Figure 4 This is a schematic diagram of a magnesium electrode structure with prefabricated U-shaped channels constructed according to Embodiment 2 of this application.

[0077] Example 3

[0078] The monitoring system provided in this embodiment is similar to that in Embodiment 1, except that the fiber optic sensing unit includes three cascaded fiber FBG segments 23, which are respectively deployed at different depths of the magnesium electrode (0.5 mm, 1 mm, and 2 mm from the surface). During the discharge process, as the metal is consumed layer by layer, the three fiber FBG segments 23 undergo sequential wavelength abrupt changes, realizing graded monitoring of SOC and providing a more accurate indication of the remaining charge. Figure 5 This is a schematic diagram of a magnesium electrode structure with pre-fabricated channels of different depths constructed for Embodiment 3 of this application.

[0079] Comparative Example 1: Fiber optic cable deployment without pretension

[0080] The same magnesium electrode and FBG as in Example 1 were used, but the difference was that the optical fiber was threaded through a straight channel without any pre-tension strain, leaving the fiber in a relaxed state within the channel. Discharge test results showed that the center wavelength of the FBG did not exhibit significant abrupt changes throughout the discharge process, only showing minor fluctuations after the metal was completely consumed, failing to effectively indicate changes in SOC. This indicates that the presence of pre-tension force is crucial for achieving "trigger-based" monitoring. Figure 6 This is a schematic diagram of the magnesium electrode structure for the fiber optic cable routing method without pretension, as constructed in Comparative Example 1 of this application.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A state-of-charge monitoring system for seawater metal-air batteries based on fiber optic sensing, characterized in that, This includes seawater metal-air battery cells, fiber optic sensing units, mounting structures, and spectral demodulation modules; The seawater metal-air battery cell includes an electrochemical reaction system using seawater as the electrolyte, and the electrochemical reaction system includes a metal electrode consumed in the discharge reaction. The fiber optic sensing unit includes at least one fiber optic cable, on which a fiber Bragg grating is provided; The mounting structure is disposed on the metal electrode and is used to fix at least a portion of the optical fiber in a pre-stretched or bent state to the interior or surface of the metal electrode, and to place the fiber Bragg grating in the fixed area; The spectral demodulation module is connected to the optical path of the optical fiber and is used to receive and analyze the wavelength signal of the reflected light; When the metal electrode is consumed to the installation position of the fiber Bragg grating as the discharge reaction in seawater proceeds, the installation structure fails, causing the optical fiber to change from a pre-stretched or bent state to a relaxed state, which in turn causes the reflected wavelength of the fiber Bragg grating to shift. The spectral demodulation module determines the state of charge of the seawater metal-air battery by detecting the wavelength shift.

2. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The metal electrode has a plate-like or block-like structure, and the material of the metal electrode is selected from magnesium, zinc, and aluminum.

3. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The mounting structure includes a channel pre-formed inside the metal electrode, the optical fiber passing through the channel, and the path of the channel is non-linear. The diameter of the channel is 0.1~0.5 mm; the non-linear shape is serpentine and / or U-shaped.

4. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The mounting structure also includes microgrooves formed on the surface of the metal electrode, and the optical fiber is fixed in the microgrooves by an encapsulation layer or a clamping sheet. The diameter of the microgrooves is 0.3 mm.

5. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The fiber optic sensing unit includes multiple fiber Bragg gratings; the mounting structure has multiple fixing points at different depths of the metal electrode, and each fiber Bragg grating is correspondingly set at a fixing point at a different depth.

6. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The spectral demodulation module includes a spectral analyzer or a fiber optic demodulator.

7. The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing according to claim 1, characterized in that, The fiber Bragg grating is a chirped fiber grating or a long-period fiber grating.

8. A method for monitoring the state of charge of a seawater metal-air battery based on fiber optic sensing, characterized in that, The seawater metal-air battery state-of-charge monitoring system based on fiber optic sensing, as described in any one of claims 1 to 7, comprises the following steps: (1) Before the seawater metal-air battery discharges, the reflection wavelength λ0 of the fiber Bragg grating in the initial state is calibrated to correspond to a state of charge of 100%; (2) During the discharge process of the seawater metal-air battery, the reflection wavelength λ of the fiber Bragg grating is monitored in real time; (3) When the reflected wavelength is detected to change abruptly from λ0 to λ1 and the offset exceeds the preset threshold, it is determined that the metal electrode at the location of the fiber Bragg grating has been exhausted and the corresponding state of charge value is output. (4) Calculate the remaining battery capacity based on the preset wavelength offset-state of charge mapping relationship.

9. The method for monitoring the state of charge of seawater metal-air batteries based on fiber optic sensing according to claim 8, characterized in that, In step (3), the preset threshold is a wavelength offset exceeding 0.1 nm; In step (4), the wavelength offset-state of charge mapping relationship is established through a pre-calibration experiment: the metal electrodes with different consumption levels are weighed, and the wavelength offset of the corresponding fiber Bragg grating is recorded. The correspondence between the wavelength offset and the metal consumption is then fitted.

10. The application of the fiber optic sensing-based seawater metal-air battery state-of-charge monitoring system according to any one of claims 1 to 7 in marine equipment energy management.

Images