Lithium battery internal state monitoring system and method

Abstract

The invention belongs to the technical field of battery monitoring, and discloses a lithium battery internal state monitoring system and method. The lithium battery internal state monitoring system provided by the invention comprises an optical fiber sensing unit, a demodulator and a data processing unit, the optical fiber sensing unit comprises three parallel optical fiber links arranged in the lithium battery, and the three optical fiber links are respectively used for acquiring temperature information, strain information and gas information in the lithium battery; the demodulator is connected with the optical fiber sensing unit and is used for receiving and demodulating the temperature information, the strain information and the gas information and sending the obtained demodulated information to the data processing unit; the data processing unit is used for obtaining monitoring information according to the demodulation information. According to the invention, real-time monitoring of multiple parameters of the lithium battery can be realized, the monitoring precision can be improved, and the system also has the advantages of electromagnetic interference resistance, corrosion resistance, simple arrangement mode and small occupied space.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery monitoring, and more specifically, relates to a lithium battery internal state monitoring system and method. Background Art

[0002] The battery management system (BMS) is a vital part of the battery energy supply system. Its role is to reflect the actual operating efficiency and safety of the battery. Therefore, the reliability of the BMS depends on an efficient and easy-to-implement battery sensing system. Traditional BMS mainly estimates the battery status by monitoring the functional status of the battery (such as voltage, current and temperature) and manages the battery during the charging and discharging process. However, the existing monitoring methods can often only measure a few parameters, and have limited understanding of the actual operation of the battery. It is difficult to accurately monitor the battery status and effectively control it, which seriously affects the battery life. At present, traditional monitoring methods for various battery parameters: such as thermocouples, resistance sensors, thermal imaging and other monitoring methods are still used today. Although these solutions can monitor the battery status, they have great limitations: poor anti-electromagnetic interference ability, insufficient spatial resolution, and complex electrical layout process. On the one hand, these methods can only monitor the temperature of the battery surface or shallow surface, and cannot further monitor the battery operation. On the other hand, the current new energy industry has a huge demand for batteries, and battery safety accidents occur frequently. These vulnerable electrical sensors cannot survive in abnormal situations. In addition, from an economical perspective, traditional monitoring equipment also places high demands on monitoring costs relative to the large monitoring range. Therefore, there is an urgent need to develop a device that can monitor multiple parameters inside the battery in real time and accurately, so as to more comprehensively monitor the operation of the battery. Summary of the invention

[0003] The present invention provides a lithium battery internal state monitoring system and method to solve the problem in the prior art that the comprehensiveness and accuracy of battery monitoring need to be improved.

[0004] The present invention provides a lithium battery internal state monitoring system, comprising: an optical fiber sensing unit, a demodulator and a data processing unit; the optical fiber sensing unit comprises three parallel optical fiber links arranged inside the lithium battery, and the three optical fiber links are respectively used to obtain temperature information, strain information and gas information inside the lithium battery; the demodulator is connected to the optical fiber sensing unit, and is used to receive and demodulate the temperature information, the strain information and the gas information, and send the obtained demodulated information to the data processing unit; the data processing unit is used to obtain monitoring information according to the demodulated information.

[0005] Preferably, the three optical fiber links are all arranged between the negative electrode layer and the lithium strip layer inside the lithium battery.

[0006] Preferably, the optical fibers of the three optical fiber links are optical fibers comprising a UV-transparent coating layer, and the optical fibers are impregnated with a silane coupling agent; the three optical fiber links are fixed to the surface of the negative electrode layer using electrolyte-resistant acrylate glue; and the optical fibers of the optical fiber links used to obtain gas information inside the lithium battery are attached with a hydrogen-sensitive film.

[0007] Preferably, a plurality of reflection grating nodes connected in series are arranged on each optical fiber link, and the central wavelengths responded to by different reflection grating nodes on each optical fiber link are different from each other.

[0008] Preferably, the number and spacing of reflection grating nodes arranged on the three optical fiber links are the same, and the grating sensitivity of multiple reflection grating nodes in the same optical fiber link is the same; the two optical fiber links used to obtain temperature information and strain information inside the lithium battery have different grating sensitivities, and the grating sensitivity difference is greater than the set grating sensitivity threshold.

[0009] Preferably, three reflection grating nodes are arranged on each optical fiber link, and the three reflection grating nodes are respectively located in the positive ear area, the negative ear area and the central area of ​​the lithium battery.

[0010] Preferably, the data processing unit includes a data demodulation module and a real-time monitoring module; the data demodulation module is used to decouple the demodulated information to obtain temperature data, strain data and gas composition data; the real-time monitoring module is used to draw the local or overall temperature field image, strain field image and gas field image of the lithium battery according to the temperature data, the strain data and the gas composition data, and display them in real time.

[0011] Preferably, the data demodulation module performs decoupling according to the difference in grating sensitivities of two optical fiber links used to obtain the temperature information and strain information inside the lithium battery, thereby obtaining the temperature data and the strain data.

[0012] Preferably, the real-time monitoring module is also used to determine whether the lithium battery is abnormal based on the temperature data, the strain data, the gas composition data and preset standard information, and to alarm if abnormal.

[0013] On the other hand, the present invention provides a method for monitoring the internal state of a lithium battery, which is implemented by using the above-mentioned lithium battery internal state monitoring system, and the method for monitoring the internal state of a lithium battery comprises the following steps:

[0014] Use optical fiber sensing units to obtain temperature information, strain information, and gas information inside lithium batteries;

[0015] Using a demodulator to receive and demodulate the temperature information, the strain information, and the gas information, and sending the obtained demodulated information to a data processing unit;

[0016] The data processing unit is used to obtain monitoring information according to the demodulated information.

[0017] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0018] The lithium battery internal state monitoring system provided by the present invention includes a fiber optic sensing unit, a demodulator and a data processing unit. The fiber optic sensing unit includes three parallel fiber optic links arranged inside the lithium battery. The three fiber optic links are respectively used to obtain temperature information, strain information and gas information inside the lithium battery. The present invention uses a demodulator to receive temperature information, strain information and gas information and demodulates them, sends the obtained demodulated information to the data processing unit, and uses the data processing unit to obtain monitoring information according to the demodulated information. That is, the present invention can synchronously monitor the temperature, strain and gas production during the operation of the lithium battery in real time, and thus can more comprehensively evaluate the use status of the lithium battery. The present invention distributes the three fiber optic links in different positions or areas of the battery pack to cover the multi-parameter scenarios of temperature, strain and gas in the space. Each fiber optic transmission path is physically isolated from each other, avoiding signal interference that may occur in the same fiber optic link, while expanding the number of nodes in the sensor network, which can improve the monitoring accuracy. In addition, combined with the characteristics of optical fiber sensing itself, the present invention also has the advantages of anti-electromagnetic interference, anti-corrosion, simple deployment, and small space occupation. It can penetrate deep into the lithium battery and realize real-time monitoring of multiple parameters of the lithium battery, which helps to improve the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of module connections of a lithium battery internal state monitoring system provided in Example 1 of the present invention;

[0020] Figure 2 A schematic diagram of the layout of an optical fiber sensing unit in a lithium battery internal state monitoring system provided in Example 1 of the present invention;

[0021] Figure 3 This is the simulation result diagram of the internal temperature field of the lithium battery. DETAILED DESCRIPTION

[0022] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] Embodiment 1:

[0024] The monitoring object of the lithium battery internal state monitoring system provided by the present invention is a lithium battery, see Figure 1 , specifically, it can be a power lithium battery pack 1, and the sensor device is installed inside a single lithium battery in the power lithium battery pack 1. The lithium battery internal state monitoring system provided by the present invention is specifically described below.

[0025] Example 1 provides a lithium battery internal state monitoring system, see Figure 1 to Figure 2 , including: an optical fiber sensing unit, a demodulator 2 and a data processing unit; the optical fiber sensing unit includes three parallel optical fiber links arranged inside the lithium battery, and the three optical fiber links are respectively used to obtain temperature information, strain information and gas information inside the lithium battery; the demodulator 2 is connected to the optical fiber sensing unit, and is used to receive and demodulate the temperature information, the strain information and the gas information, and send the obtained demodulated information to the data processing unit; the data processing unit is used to obtain monitoring information according to the demodulated information.

[0026] Among them, see Figure 2 The lithium battery includes a battery housing 5, a positive current collecting sheet 6, a positive electrode sheet 7, a lithium strip layer 8 and a negative electrode sheet 9 from the outside to the inside. The lithium battery also includes a positive electrode tab 10 and a negative electrode tab 11. The three optical fiber links in the present invention are all arranged between the negative electrode sheet 9 and the lithium strip layer 8 inside the lithium battery. A plurality of reflection grating nodes connected in series are arranged on each optical fiber link, and the central wavelengths responded to by different reflection grating nodes on each optical fiber link are different from each other.

[0027] See also Figure 2 The three optical fiber links are respectively a strain sensing link 12, a temperature sensing link 13 and a gas production sensing link 14. The strain sensing link 12 is provided with a plurality of strain sensing gratings 15, the temperature sensing link 13 is provided with a plurality of temperature sensing gratings 16, and the gas production sensing link 14 is provided with a plurality of gas production sensing gratings 17.

[0028] The optical fibers of the three optical fiber links are optical fibers containing ultraviolet-transmitting coatings. That is, the present invention uses optical fibers with ultraviolet-transmitting coatings to make grating arrays to obtain ultra-weak grating sensing arrays. Optical fibers made of ultraviolet-transmitting optical fiber coatings can improve the strength of the optical fibers and improve the stability of monitoring.

[0029] Specifically, the ultra-weak grating sensor array (i.e., ultra-low reflectivity fiber grating array) in the present invention is made of optical fiber with a UV-transmitting coating, which can be manufactured at one time according to the number of batteries required. There are no fusion points between the fiber Bragg gratings (FBGs), which not only reduces losses but also greatly improves the reliability and long-term stability of the system.

[0030] The optical fibers of the three optical fiber links can be impregnated with silane coupling agents to enhance their adhesion at the interface. Silane coupling agents can improve the bonding properties between glass fiber and resin, greatly improving the strength of glass fiber reinforced composite materials. Silane coupling agents can specifically be vinyl silane, amino silane, methacryloxy silane, etc.

[0031] See also Figure 2 The three optical fiber links are fixed on the surface of the negative electrode layer 9 by using electrolyte-resistant acrylic glue 18, and several reflection grating nodes in the three optical fiber links constitute a cascaded grating array. The electrolyte-resistant acrylic glue 18 is an anti-corrosion material with good anti-corrosion and high temperature resistance, so it is very suitable for use in the monitoring system of lithium batteries.

[0032] The optical fiber of the optical fiber link used to obtain gas information inside the lithium battery can be attached with a hydrogen-sensitive film to improve the sensitivity of the optical fiber to hydrogen. The hydrogen-sensitive film can be specifically a Pd / Ni hydrogen-sensitive film, an Au / Pd hydrogen-sensitive film, a Pd / Ag film, etc.

[0033] The number and spacing of the reflection grating nodes arranged on the three optical fiber links are the same, that is, multiple reflection gratings are evenly distributed inside the single lithium battery along the three optical fibers to form a grating array.

[0034] The grating sensitivities of multiple reflection grating nodes in the same optical fiber link are the same. The two optical fiber links used to obtain the temperature information and strain information inside the lithium battery have different grating sensitivities, and the grating sensitivity difference is greater than the set grating sensitivity threshold, that is, the grating sensitivities of the two optical fiber links used to obtain the temperature information and strain information inside the lithium battery have a large difference.

[0035] It can be understood that the fiber optic sensing unit provided by the present invention includes an ultra-weak reflection grating sensor array (hereinafter referred to as a grating array), forming three fiber optic links, on which a plurality of grating temperature sensors, a plurality of grating strain sensors and a plurality of grating gas production sensors are provided. That is, the grating array in the present invention can adopt a wavelength division multiplexing method to cascade a plurality of grating sensors on three fiber optic links to achieve quasi-distributed multi-parameter measurement. The grating array is located inside each single lithium battery in the lithium battery pack, and the grating array can be used to obtain relevant information on temperature, strain and gas production in different areas inside the lithium battery. As a passive sensor, the grating sensor is particularly suitable for use in the narrow internal space of a large-capacity lithium battery and in harsh environments with chemical corrosion.

[0036] In a preferred embodiment of the present invention, three reflection grating nodes are arranged on each optical fiber link, and the three reflection grating nodes are respectively located in the positive ear area, the negative ear area and the central area of ​​the lithium battery.

[0037] The arrangement of the reflection grating nodes is determined based on the thermal coupling model of the single battery. The present invention uses COMSOL to simulate the heat generation inside the battery, and then determines the arrangement area and number of gratings of the grating array.

[0038] Specifically, from the working principle of lithium-ion batteries, it can be known that the temperature change of the battery during the charging and discharging process of lithium-ion power batteries is mainly caused by the heat generated during the charging and discharging process. The actual heat generated is mainly caused by the chemical reaction heat Q r , polarization reaction heat Q p 、Ohm heat Q j and the side reaction heat Q generated by electrolyte decomposition s The heat generation Q is expressed as: Q = Q r +Q p +Q j +Q s The present invention uses a heat generation rate calculation model to analyze the changes in battery heat generation and temperature: In the above formula, I is the current, V is the battery volume, and E is oc is the equilibrium electromotive force of the battery, U is the operating voltage of the battery, T is the battery temperature, and is the current density J = I / V. The Joule heat generated by the equivalent polarization internal resistance is used to replace the polarization heat. Combined with the heat generation rate calculation model, the heat generation rate calculation model is established, which is: In the above formula, R p is the equivalent polarization internal resistance. Based on the law of conservation of energy and Fourier transform, a thermal coupling model of a single battery can be established by comprehensively considering the battery potential and current density model. According to the above method, a battery simulation model can be obtained, and then the key hot spots inside the battery can be determined.

[0039] like Figure 3 As shown, the present invention analyzes the internal temperature field of the lithium battery through a simulation method. The main temperature rise locations are near the positive and negative ears and the center of the battery, and the temperature rise at the positive ear and the center is more obvious. The temperature rise is usually proportional to the strain, so three areas near the positive and negative ears and the center of the battery are selected as grating layout points, which are respectively called positive ear area point A, center area point B, and negative ear area point C.

[0040] The solid electrolyte interface (SEI layer) on the surface of the negative electrode determines the intensity of the lithium precipitation process inside the battery and also serves as a serious gas production layer. Based on this, the fiber optic link layout method in the present invention is as follows: three fiber optic links are built between the negative electrode layer and the lithium belt layer inside the single lithium battery, and the three optical fibers are sequentially laid out along the directions of points A, B, and C. Three gratings are fixed at points A, B, and C, and fixed at both ends with electrolyte-resistant acrylic glue.

[0041] That is, in the preferred solution, the number of gratings on the three optical fiber links inside the battery is three, which are arranged on the positive and negative ears and the center area of ​​the battery respectively. The above arrangement can ensure the accuracy of monitoring to a great extent, while reducing the number of gratings and the system cost.

[0042] The demodulator 2 in the present invention is a grating demodulator. The data processing unit receives the optical wavelength data sent by the demodulator 2, and decouples the data to obtain temperature data, strain data and gas composition data. Specifically, the data processing unit includes a data demodulation module 3 and a real-time monitoring module 4.

[0043] The data demodulation module 3 is used to decouple the demodulated information to obtain temperature data, strain data and gas composition data.

[0044] The demodulator 2 is connected to the data demodulation module 3, which is mainly used to process the array wavelength signal to decouple the temperature parameter, strain parameter and gas production parameter. The data demodulation module 3 can simultaneously determine the positioning of each grating in the array, distinguish the independent areas of the grating, and determine the temperature parameters and strain parameters of the matching independent areas.

[0045] The data demodulation module 3 performs decoupling according to the difference in grating sensitivity of two optical fiber links (respectively denoted as the first optical fiber link and the second optical fiber link) used to obtain the temperature information and strain information inside the lithium battery, and obtains the temperature data and the strain data. In addition, the data demodulation module can also compensate for the grating in the optical fiber link (denoted as the third optical fiber link) used to obtain the gas information inside the lithium battery according to the decoupled temperature signal, and decouple the gas composition.

[0046] Specifically, the present invention decouples the cross sensitivity of temperature and strain, and uses the sensitivity difference between the first optical fiber link and the second optical fiber link to obtain:

[0047] Δλ1=K ε1 Δε+K T1 ΔT

[0048] Δλ2=K ε2 Δε+K T2 ΔT

[0049] Wherein, Δλ1 is the change in the central wavelength of each grating in the first optical fiber link, Δλ2 is the change in the central wavelength of each grating in the second optical fiber link, and K ε1 is the strain sensitivity of the first optical fiber link, K ε2 is the strain sensitivity of the second optical fiber link, Δε is the strain of each grating in the optical fiber link, K T1 is the temperature sensitivity of the first optical fiber link, K T2 is the temperature sensitivity of the second optical fiber link, and ΔT is the temperature change of each grating in the optical fiber link.

[0050] Create the matrix:

[0051]

[0052] Solve the matrix:

[0053]

[0054] Where: M = K ε2 K T1 -K T2 K ε1 .

[0055] To measure the gas production, mainly hydrogen, the wavelength of the grating in the third fiber link changes as follows:

[0056]

[0057] Where Δλ3 is the change in the center wavelength of each grating in the third optical fiber link, λ3 is the center wavelength of each grating in the third optical fiber link, and P e is the effective photoelastic constant, α M is the thermal expansion coefficient, β is the average expansion coefficient of the target parameter, ΔM is the normalized change of the target parameter, α and ξ are the thermal expansion coefficient and thermo-optic coefficient of the single-mode fiber, a and b are the cladding diameter of the fiber and the total diameter of the sensor, respectively, and Y C and Y F are the Young's modulus of the coating material and the silicon fiber, respectively, and ΔT is the temperature change. Where: Pe≈0.22, a≈5.5×10-7℃ -1 ,ξ≈6.67×10-6℃ -1 .

[0058] According to the decoupled Δε and ΔT of the first optical fiber link and the second optical fiber link, the gas production condition ΔM can be decoupled, wherein the strain has been attributed to ΔM, and M is changed by the stretching caused by the reaction between the gas and the optical fiber surface.

[0059] The present invention uses a method of decoupling different grating sensitivities to simplify the grating layout cost, and does not need to loosen or pre-tighten the grating for strain and temperature cross-sensitivity, which can greatly improve the layout freedom of the optical fiber link. The present invention uses the above method as a demodulation algorithm to quickly calculate the temperature signal, strain signal and gas production, and can also solve the problem of difficulty in demodulating large amounts of data.

[0060] Among them, the real-time monitoring module 4 is used to draw the local or overall temperature field image, strain field image and gas field image of the lithium battery according to the temperature data, the strain data and the gas composition data, and display them in real time to achieve real-time visualization of monitoring, so as to intuitively understand the real-time working status of the lithium battery.

[0061] Specifically, the real-time monitoring module 4 receives the temperature data, the strain data and the gas composition data, and combined with grating positioning, can display real-time images of the temperature field, stress field and gas production field of the lithium battery pack as a whole and the single cell, and perform real-time monitoring of the lithium battery charging and discharging process and display of the internal status, which can help users to promptly discover potential safety problems and avoid overcharging or over-discharging of the battery, thereby extending the battery life and improving the battery safety.

[0062] In addition, the real-time monitoring module 4 can also be used to determine whether the lithium battery is abnormal based on the temperature data, the strain data, the gas composition data and preset standard information, and to alarm if abnormal.

[0063] On the whole, the present invention provides an ultra-weak fiber Bragg grating (UFBG) reflective array system based on wavelength division multiplexing (WDM) technology, which specifically implements a parallel structure of three independent optical fiber links. Each optical fiber link sequentially connects multiple ultra-weak reflection grating nodes in series to form multiple physically isolated and parallel sensing paths. These optical fiber links realize parallel transmission and detection of multi-wavelength signals through wavelength division multiplexing technology. In this system, multiple ultra-weak reflection grating nodes are evenly arranged on each optical fiber link. For example, multiple grating nodes can be deployed on each link, and the distribution density of the grating nodes can be adjusted according to specific application requirements. The central wavelengths of the response of the reflection grating nodes in each optical fiber link are different from each other, and the effective distinction of the nodes can be achieved through the wavelength difference. In order to realize the excitation and transmission of multi-wavelength signals, the system can use a tunable laser source or a multi-wavelength laser source, and emit pulse signals of specific wavelengths at different time intervals. Each grating node has a unique reflection characteristic for optical signals of different wavelengths. Therefore, during the transmission of optical signals, only optical signals of specific wavelengths will be reflected at the corresponding position, thereby realizing the distinction of nodes. By adopting WDM technology, the system can simultaneously transmit multiple wavelength signals in the same optical fiber, and each wavelength signal corresponds to an independent grating node information. By demodulating the reflected signal with a demodulator, the system can accurately extract the reflection information of each grating node, thereby realizing the monitoring and processing of different sensing paths.

[0064] Embodiment 2:

[0065] Embodiment 2 provides a method for monitoring the internal state of a lithium battery, which is implemented by the lithium battery internal state monitoring system as described in Embodiment 1. The method for monitoring the internal state of a lithium battery provided in Embodiment 2 includes the following steps:

[0066] Use optical fiber sensing units to obtain temperature information, strain information, and gas information inside lithium batteries;

[0067] Using a demodulator to receive and demodulate the temperature information, the strain information, and the gas information, and sending the obtained demodulated information to a data processing unit;

[0068] The data processing unit is used to obtain monitoring information according to the demodulated information.

[0069] Since the steps of the lithium battery internal state monitoring method provided in Example 2 correspond to the functions of the components in the lithium battery internal state monitoring system provided in Example 1, they can be understood by referring to the description of Example 1 and will not be repeated here.

[0070] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A lithium battery internal state monitoring system, characterized in that: include: An optical fiber sensing unit, a demodulator and a data processing unit; the optical fiber sensing unit includes three parallel optical fiber links arranged inside a lithium battery, the three optical fiber links are respectively used to obtain temperature information, strain information and gas information inside the lithium battery; the demodulator is connected to the optical fiber sensing unit, and is used to receive and demodulate the temperature information, the strain information and the gas information, and send the obtained demodulated information to the data processing unit; the data processing unit is used to obtain monitoring information based on the demodulated information.

2. The lithium battery internal state monitoring system according to claim 1, characterized in that: The three optical fiber links are all set between the negative electrode layer and the lithium strip layer inside the lithium battery.

3. The lithium battery internal state monitoring system according to claim 2, characterized in that: The optical fibers of the three optical fiber links are optical fibers containing UV-transparent coating layers, and the optical fibers are impregnated with silane coupling agents; the three optical fiber links are fixed to the surface of the negative electrode layer with electrolyte-resistant acrylate glue; the optical fibers of the optical fiber links used to obtain gas information inside the lithium battery are attached with hydrogen-sensitive films.

4. The lithium battery internal state monitoring system according to claim 1, characterized in that: A plurality of reflection grating nodes connected in series are arranged on each optical fiber link, and the central wavelengths responded to by different reflection grating nodes on each optical fiber link are different from each other.

5. The lithium battery internal state monitoring system according to claim 4, characterized in that: The number and spacing of reflection grating nodes arranged on the three optical fiber links are the same, and the grating sensitivity of multiple reflection grating nodes in the same optical fiber link is the same; the two optical fiber links used to obtain temperature information and strain information inside the lithium battery have different grating sensitivities, and the difference in grating sensitivity is greater than the set grating sensitivity threshold.

6. The lithium battery internal state monitoring system according to claim 5, characterized in that: Three reflection grating nodes are arranged on each optical fiber link, and the three reflection grating nodes are respectively located in the positive ear area, negative ear area and center area of ​​the lithium battery.

7. The lithium battery internal state monitoring system according to claim 5, characterized in that: The data processing unit includes a data demodulation module and a real-time monitoring module; the data demodulation module is used to decouple the demodulated information to obtain temperature data, strain data and gas composition data; the real-time monitoring module is used to draw a local or overall temperature field image, strain field image and gas field image of the lithium battery according to the temperature data, the strain data and the gas composition data, and display them in real time.

8. The lithium battery internal state monitoring system according to claim 7, characterized in that: The data demodulation module performs decoupling according to the grating sensitivity difference of two optical fiber links used to obtain the temperature information and strain information inside the lithium battery, so as to obtain the temperature data and the strain data.

9. The lithium battery internal state monitoring system according to claim 7, characterized in that: The real-time monitoring module is also used to determine whether the lithium battery is abnormal based on the temperature data, the strain data, the gas composition data and preset standard information, and to alarm if abnormal.

10. A method for monitoring the internal state of a lithium battery, characterized in that: The lithium battery internal state monitoring system is implemented as described in any one of claims 1 to 9, and the lithium battery internal state monitoring method comprises the following steps: Use optical fiber sensing units to obtain temperature information, strain information, and gas information inside lithium batteries; Using a demodulator to receive and demodulate the temperature information, the strain information, and the gas information, and sending the obtained demodulated information to a data processing unit; The data processing unit is used to obtain monitoring information according to the demodulated information.

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