Battery chemical stress in-situ monitoring method

Abstract

The invention provides a battery chemical stress in-situ monitoring method, which comprises the following steps that: a sensing optical fiber covers the upper surface of an anode plate of a battery in a snakelike routing mode in a first direction, the sensing optical fiber completely covers the anode plate, and every two adjacent first optical fiber sections are connected through a corresponding second optical fiber section; the two ends, located outside the anode plate, of each first optical fiber section are fixed to a protective shell below the anode plate, so that each first optical fiber section is always kept in a stretching state in the monitoring process; connecting the sensing optical fiber with a strain measurement and analysis system, and respectively carrying out pressing test on two ends of each first optical fiber section so as to carry out position calibration on each first optical fiber section; and the strain measurement and analysis system obtains a three-dimensional strain field of the anode plate according to the scattering signals reversely transmitted back by the first optical fiber sections, the calibrated two-end positions of the first optical fiber sections and the arrangement relation between the first optical fiber sections. The strain field monitoring of the whole surface of the anode plate can be realized.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber sensing, and in particular relates to an in-situ monitoring method for battery chemical stress. Background Art

[0002] In recent years, the field of electric vehicles driven by new energy has become a global focus. Lithium-ion batteries have become a key research area due to their high energy density, high efficiency and environmental friendliness. In addition, they are widely used in portable electronic devices, energy storage systems and medical devices. However, along with these advances come challenges in the research, testing and use of lithium-ion batteries, which requires attention to the working state inside the battery. Understanding these issues is crucial for a deep understanding of the battery operating state and effective management of battery systems. The choice of anode materials is crucial to influencing the performance of lithium-ion batteries, and silicon-containing anode materials are the first choice for preparing high-specific capacity batteries. However, their significant expansion effect poses challenges to cycling and life. As the battery undergoes cyclic charge and discharge processes, the anode material may experience residual strain, affecting its long-term stability and performance. Therefore, strain monitoring of the battery is crucial to predict its operating state. To date, there is no effective method that can achieve distributed in-situ monitoring inside lithium batteries. Summary of the invention

[0003] The present invention provides a battery chemical stress in-situ monitoring method to solve the problem that the strain field of a battery anode plate cannot be reconstructed in a distributed real-time manner.

[0004] According to a first aspect of an embodiment of the present invention, a method for in-situ monitoring of chemical stress of a battery is provided, comprising: step S100, covering the upper surface of the anode plate of the battery with a sensing optical fiber in a serpentine manner in a first direction, wherein the sensing optical fiber is bent each time and is routed in a second direction as a first optical fiber segment, and each adjacent two first optical fiber segments are connected via a corresponding second optical fiber segment, and the first direction is perpendicular to the second direction;

[0005] Step S200: for each first optical fiber segment, two ends of the first optical fiber segment outside the anode plate are respectively fixed to the protective shell under the anode plate, so that the first optical fiber segment is applied with corresponding prestress to ensure that the first optical fiber segment is always in a stretched state during the monitoring process;

[0006] Step S300, connecting one end of the sensing optical fiber to a strain measurement and analysis system, and performing a press test on both ends of each first optical fiber segment to calibrate the position of each first optical fiber segment;

[0007] Step S400, the strain measurement and analysis system determines the strain amount at each measuring point on the first optical fiber segment according to the scattered signal transmitted back by each first optical fiber segment and the calibrated positions of both ends of the first optical fiber segment; reconstructs the two-dimensional strain field of the first optical fiber segment according to the strain amount at each measuring point on the first optical fiber segment; and obtains the three-dimensional strain field of the anode plate composed of the two-dimensional strain fields of the first optical fiber segments according to the layout relationship between the first optical fiber segments.

[0008] In an optional implementation, when the battery is charged and discharged, the anode plate undergoes a chemical reaction, causing the anode plate to shrink or expand, thereby causing the first optical fiber segment covering the anode plate to be compressed or stretched axially, generating axial strain of the optical fiber.

[0009] In another optional implementation, the anode plate, the isolation layer and the cathode plate are sequentially arranged on the protective shell from top to bottom.

[0010] In another optional implementation, the second optical fiber segment is laid on the protective shell under the anode plate. In the step S400, before reconstructing the two-dimensional strain field of the first optical fiber segment according to the strain at each measuring point on the first optical fiber segment, it also includes: the strain measurement and analysis system determines the strain of the second optical fiber segment according to the scattered signal transmitted back by each second optical fiber segment and the calibrated two end positions of the first optical fiber segment; determines the corresponding temperature of the second optical fiber segment according to the strain of the second optical fiber segment; adds the temperatures of each second optical fiber segment and takes an average value to obtain the average temperature of the battery; converts the average temperature into the corresponding strain; and subtracts the strain corresponding to the average temperature from the strain at each measuring point on the first optical fiber segment.

[0011] In another optional implementation, each second optical fiber segment completely covers the protective shell on the corresponding side in the second direction, and the lengths of the second optical fiber segments are equal.

[0012] In another optional implementation, the method further includes: determining the thickness uniformity of the anode plate according to the three-dimensional strain field of the anode plate.

[0013] In another optional implementation, the method further includes: determining the adaptability of the manufacturing process for manufacturing anode plates of different materials according to the thickness uniformity of anode plates of different materials manufactured under the corresponding manufacturing process.

[0014] In another optional implementation, the method further includes: for anode plates made of different materials, taking the anode plate of the corresponding material with a smaller corresponding strain amount in the initial three-dimensional strain field as the anode plate with better performance.

[0015] In another optional implementation, the method further includes: for each anode plate of different materials, plotting a trend curve of the sum of the strains versus time, with time as the horizontal coordinate and the sum of the strains of each first optical fiber segment relative to its initial state as the vertical coordinate; determining the time when the slope of the curve decreases and the slope of the curve after the decrease in the change trend curve; determining the initial slope of the change trend curve; and based on the change trend curves corresponding to the anode plates of different materials, screening out the anode plates of the corresponding materials with a higher initial slope, a later time when the slope of the curve decreases, and a higher slope of the curve after the decrease as the anode plates with better performance.

[0016] In another optional implementation, the sum of the strain amounts is: first, for each first optical fiber segment, the strain amounts of each measurement point on the first optical fiber segment relative to its initial state are added to obtain the strain amounts of each first optical fiber segment relative to its initial state; and then the strain amounts of each first optical fiber segment relative to its initial state are added.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention covers the anode plate of the battery with the sensing optical fiber in the first direction and in the second direction perpendicular to the first direction, so that the strain of the entire anode plate can be monitored, so that the uniformity of the anode plate of the corresponding material can be determined, and the anode plate material or manufacturing process can be adjusted according to the uniformity, and a better anode plate material can be selected according to the overall change of the strain of the anode plate of the corresponding material during use; when arranging the first optical fiber segment located directly above the anode plate, the two ends of the first optical fiber segment are respectively fixed on the protective shell under the anode plate, and prestress is applied to the first optical fiber segment, so that the first optical fiber segment is always kept in a stretched state during the monitoring process, so that the first optical fiber segment can accurately detect the deformation of the anode plate during the monitoring process; the present invention can realize the three-dimensional strain field reconstruction of the anode plate according to the calibrated two-end positions of each first optical fiber segment, the scattered signals transmitted back by each first optical fiber segment, and the arrangement relationship between each first optical fiber segment; the present invention implants the sensing optical fiber into the battery, and does not affect the battery performance while realizing in-situ monitoring; and the present invention adopts distributed monitoring, which can obtain the strain field of the entire surface of the lithium battery anode material instead of the strain information of a single point position compared with a single point sensor, and has higher reliability;

[0019] 2. The present invention uses the sum of the strains of all the measuring points on the second optical fiber segment as the strain of the second optical fiber segment, and determines the corresponding temperature of the second optical fiber segment by establishing the relationship between the strain of the second optical fiber segment and the temperature. Since the strain of the second optical fiber segment is large, the accuracy of reflecting its temperature based on the strain of the second optical fiber segment is higher; after determining the temperature of each second optical fiber segment, the temperature of each second optical fiber segment is added and then divided by the number of second optical fiber segments to obtain the average temperature of the battery, and the accuracy of the average temperature of the battery obtained in this way is also higher; the present invention subtracts the strain caused by the average temperature of the battery from the strain detected on the first optical fiber segment, and can obtain the accurate strain caused by the deformation of the anode plate on the first optical fiber segment, thereby improving the accuracy of the reconstruction of the three-dimensional strain field of the anode plate;

[0020] 3. The present invention enables each second optical fiber segment to completely cover the protective shell on the corresponding side in the second direction. Since the contact length between the second optical fiber segment and the protective shell is longer, it is easier for the heat to quickly reach thermal equilibrium, thereby reducing the difference in the impact of temperature on the first optical fiber segment and the second optical fiber segment. The present invention enables the lengths of each second optical fiber segment to be equal, so that a unified standard can be used to determine the corresponding temperature of the second optical fiber segment based on the relationship between the strain of the second optical fiber segment and the temperature.

[0021] 4. The present invention can determine the thickness uniformity of the anode plate according to the three-dimensional strain field of the anode plate, and can also select the anode plate material corresponding to the manufacturing process or the manufacturing process corresponding to the anode plate material according to the thickness uniformity of the anode plate;

[0022] 5. The present invention uses the anode plates of different materials, and uses the anode plates of the corresponding materials with smaller initial three-dimensional strain field corresponding to the strain as the anode plates with better performance, so as to avoid the anode materials from cracking due to excessive strain, thus affecting the battery life;

[0023] 6. The present invention monitors the three-dimensional strain field of the anode plate in real time, draws a curve for reflecting the overall strain change trend of the anode plate, and can screen out anode plates of corresponding materials with better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of an embodiment of the method for in-situ monitoring of battery chemical stress of the present invention;

[0025] Figure 2 It is the layout circuit diagram of the sensing optical fiber of the present invention;

[0026] Figure 3 is a cross-sectional view of the arrangement of the sensing optical fiber of the present invention;

[0027] Figure 4 is a schematic diagram of the reconstruction of the three-dimensional strain field of the anode plate of the present invention;

[0028] Figure 5 It is a schematic structural diagram of an embodiment of a battery chemical stress in-situ monitoring system of the present invention. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0030] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] See also Figure 1 , is a flow chart of an embodiment of the method for in-situ monitoring of battery chemical stress of the present invention. Figures 2 to 4 As shown, the method may include:

[0032] Step S100, the sensing optical fiber is arranged to cover the upper surface of the anode plate 2 of the battery in a serpentine manner in the first direction, and each time the sensing optical fiber 1 bends and routes along the second direction is the first optical fiber segment 11, and each adjacent two first optical fiber segments 11 are connected by a corresponding second optical fiber segment 12, and the first direction is perpendicular to the second direction.

[0033] In this embodiment, the first direction can be the length direction of the anode plate 2, and the second direction can be the width direction of the anode plate 2. The sensing optical fiber is composed of a plurality of first optical fiber segments 11 parallel to the second direction and arranged at intervals, and a plurality of second optical fiber segments 12 for connecting each adjacent first optical fiber segment. The first optical fiber segment 12 completely covers the anode plate in the second direction (i.e., the width direction of the anode plate), and the layout interval of the mutually parallel second optical fiber segments 12 is greater than 1 mm. The second optical fiber segments 12 are located on both sides of the anode plate 2, and the second optical fiber segments 12 on both sides can be staggered. The sensing optical fiber can be packaged in the protective shell of the battery together with the anode plate 2. The sensing optical fiber should have a high temperature resistant coating layer, such as a polyimide coating, a gold coating, etc., to ensure that the optical fiber to be tested will not break when the battery is packaged. When the battery is charged and discharged, the anode plate 2 will undergo a chemical reaction, causing the anode plate to shrink or expand, so that the first optical fiber segment covering the anode plate is compressed or stretched in the axial direction of the optical fiber, generating an axial strain of the optical fiber.

[0034] Step S200, for each first optical fiber segment 11, the two ends 13 of the first optical fiber segment 11 located outside the anode plate 2 are respectively fixed to the protective shell 3 under the anode plate 2 (fixing can be carried out using ear glue, etc.), so that the first optical fiber segment 11 is applied with corresponding prestress to ensure that the first optical fiber segment 11 always remains in a stretched state during the monitoring process.

[0035] In this embodiment, combined with Figure 3 As shown, the protective shell 3 is provided with the anode plate 2, the isolation layer 4 and the cathode plate 5 in order from top to bottom, and another protective shell may be provided on the anode plate 2. The battery may be a lithium battery, and the protective shell 3 may be an aluminum plastic shell for packaging the battery and ensuring that the electrolyte does not leak out; the cathode plate 5 may be a lithium electrode; the isolation layer may be a piece of diaphragm paper, firstly to ensure that the anode and cathode materials are separated and do not react, and secondly to ensure that the anode strain of the lithium battery is not interfered by the cathode; the anode plate 3 may be replaced with various materials, such as a mixed electrode of silicon dioxide (SiO) and graphite (C).

[0036] Step S300 , connecting one end of the sensing optical fiber to a strain measurement and analysis system, and performing a press test on both ends 13 of each first optical fiber segment 11 to calibrate the position of each first optical fiber segment 11 .

[0037] Step S400, the strain measurement and analysis system can determine the strain amount at each measuring point on the first optical fiber segment 11 according to the scattered signal transmitted back by each first optical fiber segment 11 and the calibrated two-end positions of the first optical fiber segment 11; reconstruct the two-dimensional strain field of the first optical fiber segment 11 according to the strain amount at each measuring point on the first optical fiber segment 11; and obtain the three-dimensional strain field of the anode plate 2 composed of the two-dimensional strain fields of each first optical fiber segment according to the layout relationship between each first optical fiber segment 11.

[0038] In this embodiment, combined with Figure 5 As shown, the strain measurement and analysis system may include an OFDR system (e.g., a phase-type optical frequency domain reflectometer φ-OFDR) and a data processing device, wherein the OFDR system can detect the axial strain generated on the sensing optical fiber based on the scattered signal transmitted back by the sensing optical fiber, and the data processing unit reconstructs the three-dimensional strain field of the battery based on the detected strain, thereby realizing distributed in-situ monitoring of the anode plate in the battery.

[0039] As can be seen from the above embodiments, the present invention covers the anode plate of the battery with the sensing optical fiber in a first direction and in a second direction perpendicular to the first direction, so that the strain of the entire anode plate can be monitored, thereby determining the uniformity of the anode plate of the corresponding material, adjusting the anode plate material or manufacturing process according to the uniformity, and selecting a better anode plate material according to the overall change in the strain of the anode plate of the corresponding material during use; when the present invention arranges the first optical fiber segment located directly above the anode plate, the two ends of the first optical fiber segment are respectively fixed on the protective shell under the anode plate, and prestress is applied to the first optical fiber segment, so that the first optical fiber segment The segment is always kept in a stretched state during the monitoring process, so that the first optical fiber segment can accurately detect the deformation of the anode plate during the monitoring process; the present invention can realize the three-dimensional strain field reconstruction of the anode plate according to the calibrated two end positions of each first optical fiber segment, the scattered signals transmitted back by each first optical fiber segment and the layout relationship between each first optical fiber segment; the present invention implants the sensing optical fiber into the battery, which will not affect the battery performance while realizing in-situ monitoring; and the present invention adopts distributed monitoring, which can obtain the strain field of the entire surface of the lithium battery anode material instead of the strain information of a single point position compared with a single point sensor, and has higher reliability.

[0040] During the battery charging and discharging process, the anode plate undergoes chemical reactions, which not only deforms the anode plate but also generates a certain amount of heat. Therefore, the first optical fiber segment 11 in the sensing optical fiber will not only be strained due to the deformation of the anode plate, but also strained due to the temperature. In order to eliminate the interference of temperature, the second optical fiber segment is laid on the protective shell under the anode plate. In the step S400, before reconstructing the two-dimensional strain field of the first optical fiber segment according to the strain at each measurement point on the first optical fiber segment, it can also include:

[0041] The strain measurement and analysis system determines the strain of each second optical fiber segment based on the scattered signal transmitted back by each second optical fiber segment and the calibrated two end positions of the first optical fiber segment; determines the corresponding temperature of the second optical fiber segment based on the strain of the second optical fiber segment; adds the temperatures of each second optical fiber segment and takes an average value to obtain the average temperature of the battery; converts the average temperature into the corresponding strain; and subtracts the strain corresponding to the average temperature from the strain at each measuring point on the first optical fiber segment.

[0042] The strain of the sensing fiber affected by temperature is usually small. If, when determining the average temperature of the battery, the strain at each measuring point on all the second optical fiber segments is added and then divided by the number of all measuring points to obtain the average strain, and the average temperature is determined by establishing a relationship between the average strain and the average temperature, then due to the small average strain, the accuracy of reflecting the average temperature based on the average strain is not high. However, the present invention uses the sum of the strains of all measuring points on the second optical fiber segment as the strain of the second optical fiber segment, and determines the corresponding temperature of the second optical fiber segment by establishing a relationship between the strain of the second optical fiber segment and the temperature. Since the strain of the second optical fiber segment is large, the accuracy of reflecting its temperature based on the strain of the second optical fiber segment is high; after determining the temperature of each second optical fiber segment, the temperature of each second optical fiber segment is added and then divided by the number of second optical fiber segments to obtain the average temperature of the battery, and the accuracy of the average temperature of the battery obtained in this way is also high; the present invention subtracts the strain caused by the average temperature of the battery from the strain detected on the first optical fiber segment, and can obtain the accurate strain caused by the deformation of the anode plate on the first optical fiber segment, thereby improving the accuracy of the reconstruction of the three-dimensional strain field of the anode plate. In addition, when eliminating the influence of temperature corresponding variable measurement, the present invention establishes two types of corresponding relationships related to temperature. One type of temperature relationship is to associate the total strain of the second optical fiber segment and the temperature of the area where the second optical fiber segment is located on the protective shell on both sides under the anode plate. The other type of temperature relationship is to associate the average temperature of the protective shell on both sides under the anode plate and the strain of the first optical fiber segment on the anode plate caused by the average temperature. Both of these relationships establish the relationship between the optical fiber and the temperature of the protective shell. The relationship is simple to establish, and when a parameter in one of the relationships changes (for example, the coverage of the corresponding area on the protective shell by the second optical fiber segment, etc.), only the relationship needs to be adjusted without having to re-establish the entire relationship. Therefore, the temperature elimination has higher flexibility.

[0043] Among them, since the anode plate generates heat during the battery charging and discharging process, the heat can be transferred from the anode plate to the first sensing optical fiber segment and then to the second optical fiber segment. On the other hand, the heat can be transferred to the protective shell through the isolation layer and the cathode layer in sequence for heat dissipation. Since the second optical fiber segment is laid on the protective shell, the heat dissipation forms a closed-loop path, and the temperature has little effect on the first optical fiber segment and its corresponding second optical fiber segment. The present invention can also make each second optical fiber segment 12 completely cover the protective shell 3 on the corresponding side in the second direction. Since the contact length between the second optical fiber segment and the protective shell is longer, it is easier for the heat to quickly reach thermal equilibrium, reducing the difference in the effect of temperature on the first optical fiber segment and the second optical fiber segment. The lengths of the second optical fiber segments 12 of the present invention can also be equal, and the shapes of the second optical fiber segments can also be the same. In this way, a unified standard can be adopted to determine the corresponding temperature of the second optical fiber segment based on the relationship between the strain of the second optical fiber segment and the temperature.

[0044] In addition, combined Figure 4As shown, the method of the present invention may also include: determining the thickness uniformity of the anode plate according to the three-dimensional strain field of the anode plate, and determining the manufacturing qualification rate of the anode plate according to the thickness uniformity. The method of the present invention may also include: determining the adaptability of the manufacturing process for manufacturing anode plates of different materials according to the thickness uniformity of anode plates of different materials manufactured under the corresponding manufacturing process. It can be seen that the present invention can determine the thickness uniformity of the anode plate according to the three-dimensional strain field of the anode plate, and according to the thickness uniformity of the anode plate, can also select the anode plate material corresponding to the manufacturing process or the manufacturing process corresponding to the anode plate material.

[0045] When screening the materials of the anode plates, since for different anode plate materials, if the initial three-dimensional strain field corresponds to a large strain amount, the anode material may crack due to excessive strain, thereby affecting the battery life. Therefore, the method of the present invention may also include: for anode plates of different materials, the anode plate of the corresponding material with a smaller initial three-dimensional strain field corresponding to the strain amount is selected as the anode plate with better performance.

[0046] In addition, during the charge and discharge process of the battery, the ions in the battery will continue to move, but as time goes by, some of the ions may no longer move, which will cause the activity of the anode material to become lower and lower, thereby causing the strain to become smaller and smaller. By judging the change trend of the strain, the performance of the anode material can be reflected to a certain extent. To this end, the method of the present invention can also include, for each anode plate of different materials, taking time as the horizontal coordinate and the sum of the strains of each first optical fiber segment relative to its initial state as the vertical coordinate, drawing a change trend curve of the sum of the strains over time; determining the time when the slope of the curve in the change trend curve decreases and the slope of the curve after the decrease; determining the initial slope of the change trend curve; according to the change trend curve corresponding to each anode plate of different materials, screening out the corresponding material anode plate with a higher initial slope, a later time when the slope of the curve decreases, and a higher slope of the curve after the decrease as the anode plate with better performance. It can be seen that the present invention can screen out the anode plate of the corresponding material with better performance by real-time monitoring of the three-dimensional strain field of the anode plate and drawing a curve used to reflect the overall strain change trend of the anode plate.

[0047] The sum of the strain amounts can be obtained by: first, for each first optical fiber segment, adding the strain amounts of each measuring point on the first optical fiber segment relative to its initial state to obtain the strain amounts of each first optical fiber segment relative to its initial state; and then adding the strain amounts of each first optical fiber segment relative to its initial state.

[0048] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0049] It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims

1. A method for in-situ monitoring of battery chemical stress, characterized in that: include: Step S100, the sensing optical fiber is arranged to cover the upper surface of the anode plate of the battery in a serpentine manner in a first direction, the first optical fiber segment is arranged along the second direction after each bending of the sensing optical fiber, and each two adjacent first optical fiber segments are connected by a corresponding second optical fiber segment, and the first direction is perpendicular to the second direction; Step S200: for each first optical fiber segment, two ends of the first optical fiber segment outside the anode plate are respectively fixed to the protective shell under the anode plate, so that the first optical fiber segment is applied with corresponding prestress to ensure that the first optical fiber segment is always in a stretched state during the monitoring process; Step S300, connecting one end of the sensing optical fiber to a strain measurement and analysis system, and performing a press test on both ends of each first optical fiber segment to calibrate the position of each first optical fiber segment; Step S400, the strain measurement and analysis system determines the strain amount at each measuring point on the first optical fiber segment according to the scattered signal transmitted back by each first optical fiber segment and the calibrated positions of both ends of the first optical fiber segment; reconstructs the two-dimensional strain field of the first optical fiber segment according to the strain amount at each measuring point on the first optical fiber segment; and obtains the three-dimensional strain field of the anode plate composed of the two-dimensional strain fields of the first optical fiber segments according to the layout relationship between the first optical fiber segments.

2. The battery chemical stress in-situ monitoring method according to claim 1, characterized in that: When the battery is charged and discharged, the anode plate undergoes a chemical reaction, causing the anode plate to shrink or expand, so that the first optical fiber segment covered on the anode plate is compressed or stretched in the axial direction of the optical fiber, generating an axial strain of the optical fiber.

3. The battery chemical stress in-situ monitoring method according to claim 1, characterized in that: The anode plate, the isolation layer and the cathode plate are arranged on the protective shell in sequence from top to bottom.

4. The method for in-situ monitoring of battery chemical stress according to any one of claims 1 to 3, characterized in that: The second optical fiber segment is laid on the protective housing under the anode plate. In the step S400, before reconstructing the two-dimensional strain field of the first optical fiber segment according to the strain amount at each measuring point on the first optical fiber segment, the step further includes: The strain measurement and analysis system determines the strain of each second optical fiber segment based on the scattered signal transmitted back by each second optical fiber segment and the calibrated two end positions of the first optical fiber segment; determines the corresponding temperature of the second optical fiber segment based on the strain of the second optical fiber segment; adds the temperatures of each second optical fiber segment and takes an average value to obtain the average temperature of the battery; converts the average temperature into the corresponding strain; and subtracts the strain corresponding to the average temperature from the strain at each measuring point on the first optical fiber segment.

5. The battery chemical stress in-situ monitoring method according to claim 4, characterized in that: Each second optical fiber segment completely covers the protective shell on the corresponding side in the second direction, and the lengths of the second optical fiber segments are equal.

6. The battery chemical stress in-situ monitoring method according to claim 1, characterized in that: The method further includes: determining the thickness uniformity of the anode plate according to the three-dimensional strain field of the anode plate.

7. The battery chemical stress in-situ monitoring method according to claim 6, characterized in that: The method further comprises: determining the adaptability of the manufacturing process for manufacturing anode plates of different materials according to the thickness uniformity of the anode plates of different materials manufactured under the corresponding manufacturing process.

8. The battery chemical stress in-situ monitoring method according to claim 1, 6 or 7, characterized in that: The method further comprises: for anode plates of different materials, taking the anode plate of the corresponding material with the smaller corresponding strain amount of the initial three-dimensional strain field as the anode plate with better performance.

9. The battery chemical stress in-situ monitoring method according to claim 8, characterized in that: The method further comprises: for each anode plate of different materials, taking time as the horizontal coordinate and the sum of the strains of each first optical fiber segment relative to its initial state as the vertical coordinate, drawing a trend curve of the sum of the strains over time; determining the time when the slope of the curve in the trend curve decreases and the slope of the curve after the decrease; determining the initial slope of the trend curve; According to the change trend curves corresponding to the anode plates of different materials, the anode plates of the corresponding materials with higher initial slope, later decreasing time of the curve slope and higher slope of the curve after decreasing are selected as the anode plates with better performance.

10. The battery chemical stress in-situ monitoring method according to claim 9, characterized in that: The sum of the strain amounts is: first, for each first optical fiber segment, the strain amounts of each measuring point on the first optical fiber segment relative to its initial state are added to obtain the strain amounts of each first optical fiber segment relative to its initial state; then the strain amounts of each first optical fiber segment relative to its initial state are added.

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