Optical fiber sensor, battery module and battery abnormity identification method

Abstract

The invention provides an optical fiber sensor, a battery module and a battery abnormity identification method. The optical fiber sensor comprises a first distributed Bragg reflector (DBR); the first DBR is arranged on one side of the transition metal layer; the second DBR is arranged on the other side of the transition metal layer; one side, far away from the transition metal layer, of the second DBR is arranged at one end of the optical fiber; an optical fiber coupling end of the optical fiber coupler is connected with the other end of the optical fiber; the luminous source is connected with the light source connecting end of the optical fiber coupler; and the optical receiver is connected with the receiver connecting end of the optical fiber coupler. The technical problems that the electrolyte condition cannot be analyzed and the temperature detection timeliness is poor in the prior art are solved, and the technical effect of improving the electrolyte and temperature detection timeliness is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery anomaly identification, and in particular to a fiber sensor, a battery module and a battery anomaly identification method. BACKGROUND

[0002] At present, the battery management system (BMS) of an electric vehicle mainly performs state monitoring through sensors corresponding to voltage, current and temperature respectively, but there are certain limitations in sensor detection. First, the chemical information monitoring capability is insufficient. Traditional sensors such as thermocouples and NTC (NTC, Negative Temperature Coefficient) can only measure the surface temperature of the battery and cannot directly monitor the internal chemical changes such as volatilization and decomposition of the electrolyte, but these changes are often the precursor of battery performance degradation and thermal runaway. Second, there is a significant delay in thermal runaway warning. The existing temperature sensor usually needs to wait until the cell temperature rises significantly to trigger the warning, resulting in a response lag of 5 to 10 minutes. SUMMARY

[0003] Therefore, the purpose of the present application is to at least provide a fiber sensor, a battery module and a battery anomaly identification method, which solve the technical problems that the prior art cannot analyze the electrolyte condition and the temperature detection is not timely, and achieve the technical effect of improving the timeliness of detecting the electrolyte and temperature.

[0004] The present application mainly includes the following aspects: In a first aspect, the present application provides a fiber sensor, which comprises: a first distributed Bragg reflector (DBR); a transition metal layer, the first DBR being arranged on one side of the transition metal layer; a second DBR, the second DBR being arranged on the other side of the transition metal layer; an optical fiber, one end of the optical fiber being arranged on the side of the second DBR away from the transition metal layer; an optical fiber coupler, the optical fiber connection end of the optical fiber coupler being connected to the other end of the optical fiber; a light emitting source, the light emitting source being connected to the light source connection end of the optical fiber coupler; and a light receiver, the light receiver being connected to the receiver connection end of the optical fiber coupler.

[0005] Optionally, the fiber sensor further comprises a sensitive film for increasing the incident angle of the fiber sensor, wherein the sensitive film is arranged on the side of the first DBR away from the transition metal layer.

[0006] Optionally, the target DBR comprises a plurality of pairs of dielectric layers arranged in stacks, and the target DBR comprises the first DBR or the second DBR, wherein each pair of dielectric layers comprises a dielectric layer with a first refractive index and a dielectric layer with a second refractive index, and the first refractive index and the second refractive index are different.

[0007] In a second aspect, the embodiments of the present application further provide a battery module, comprising: a packaging shell; at least one battery cell, each battery cell being located inside the packaging shell; and at least one optical fiber sensor, which is the optical fiber sensor as described in the first aspect or any possible implementation manner of the first aspect, one optical fiber sensor corresponding to one battery cell, for each optical fiber sensor, the collection end of the mirror of the optical fiber sensor is located inside the packaging shell and placed in a preset surrounding area of an electrolyte vapor outlet outside the battery cell packaging of the corresponding battery cell, and the output end of the optical fiber coupler of the optical fiber sensor is located outside the packaging shell.

[0008] Optionally, the electrolyte vapor outlet comprises a tab of a preset electrode of the battery cell packaging or an electrolyte injection port of the battery cell.

[0009] Optionally, the battery module further comprises at least one bend-resistant optical fiber, wherein the at least one optical fiber sensor and the at least one bend-resistant optical fiber are bundled into an optical cable, and one end of the optical fiber coupler in the optical cable is arranged outside the packaging shell.

[0010] In a third aspect, the embodiments of the present application further provide a battery anomaly identification method, which is applied to the battery module as described in the second aspect or any possible implementation manner of the second aspect, and the method comprises: acquiring reflected light output by an output end of each optical fiber sensor in the battery module and determining a target reflected spectrum corresponding to each optical fiber sensor; for each optical fiber sensor, determining a first target center wavelength and a second target center wavelength of the optical fiber sensor from the target reflected spectrum corresponding to the optical fiber sensor, wherein the target center wavelength refers to a wavelength when an optical Tamm plasmon resonance is excited; determining an electrolyte refractive index and an electrolyte temperature corresponding to the first target center wavelength and the second target center wavelength of each optical fiber sensor according to a conversion relationship between the first target center wavelength and an ambient refractive index and an ambient temperature and a conversion relationship between the second target center wavelength and the ambient refractive index and the ambient temperature, which are obtained by simulation in advance; and determining whether the battery module is in an abnormal state according to the electrolyte refractive index and the electrolyte temperature.

[0011] Optionally, the conversion relationship between the center wavelength and the environmental refractive index is determined by the following method: after the simulation structure of the collection end of the optical fiber sensor and the reference temperature thereof are built, the collection end of the optical fiber sensor is changed to be in different environmental refractive indexes, and the reflection spectrum under each environmental refractive index is collected; the first preset center wavelength of the reflection spectrum corresponding to each environmental refractive index is subjected to data fitting to determine a first refractive index conversion relationship between the first preset center wavelength and the environmental refractive index, and the second preset center wavelength of the reflection spectrum corresponding to each environmental refractive index is subjected to data fitting and a second refractive index conversion relationship between the second preset center wavelength and the environmental refractive index.

[0012] Optionally, the conversion relationship between the center wavelength and the environmental temperature is determined by the following method: after the simulation structure of the collection end of the optical fiber sensor and the reference refractive index thereof are built, the collection end of the optical fiber sensor is changed to be in different environmental temperatures, and the reflection spectrum under each environmental temperature is collected; the third preset center wavelength of the reflection spectrum corresponding to each environmental temperature is subjected to data fitting to determine a first temperature conversion relationship between the third preset center wavelength and the environmental temperature, and the fourth preset center wavelength of the reflection spectrum corresponding to each environmental temperature is subjected to data fitting to determine a second temperature conversion relationship between the fourth preset center wavelength and the environmental temperature.

[0013] Optionally, the electrolyte refractive index and the electrolyte temperature corresponding to the first target center wavelength and the second target center wavelength of each optical fiber sensor are determined by the following method: the conversion relationship between the first target center wavelength and the environmental refractive index and the environmental temperature and the conversion relationship between the second target center wavelength and the environmental refractive index and the environmental temperature are obtained by pre-simulation, and a cross-sensitivity matrix is established; the difference between the first target center wavelength and the second target center wavelength of each optical fiber sensor and the reference center wavelength is calculated, and the cross-sensitivity matrix is combined to calculate the refractive index variable of each optical fiber sensor for the reference refractive index and the temperature variable of each optical fiber sensor for the reference temperature; the electrolyte refractive index of each optical fiber sensor is calculated by the refractive index variable of each optical fiber sensor and the reference refractive index, and the electrolyte temperature of each optical fiber sensor is calculated by the temperature variable of each optical fiber sensor and the reference temperature.

[0014] The optical fiber sensor, the battery module and the battery abnormality identification method provided by the embodiment of the application, the optical fiber sensor comprises: a first distributed Bragg reflector (DBR); a transition metal layer, the first DBR is arranged on one side of the transition metal layer; a second DBR, the second DBR is arranged on the other side of the transition metal layer; an optical fiber, one end of the optical fiber is arranged on the side of the second DBR away from the transition metal layer; an optical fiber coupler, the optical fiber connecting end of the optical fiber coupler is connected to the other end of the optical fiber; a light emitting source, the light emitting source is connected to the light source connecting end of the optical fiber coupler; and a light receiver, the light receiver is connected to the receiver connecting end of the optical fiber coupler. By integrating the optical fiber sensor in the battery module, and placing the collection end of the mirror of the optical fiber sensor around the electrolyte vapor outlet outside the cell package, the temperature and the refractive index of the electrolyte vapor are analyzed by the reflected spectrum processed by the optical fiber sensor, so that whether the battery generates temperature abnormity or electrolyte abnormity is analyzed, and the technical problems that the electrolyte condition cannot be analyzed and the temperature detection is not timely in the prior art are solved, and the technical effect of improving the timeliness of detecting the electrolyte and the temperature is achieved.

[0015] In order to make the above objectives, characteristics and advantages of the application more apparent, clear and easy to understand, the following will specifically describe the preferred embodiments of the application with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0017] Figure 1 The structure of the optical fiber sensor provided by the embodiment of the application is shown Figure 1 .

[0018] Figure 2 The structure of the optical fiber sensor provided by the embodiment of the application is shown Figure 2 .

[0019] Figure 3 The structure of the battery module provided by the embodiment of the application is shown.

[0020] Figure 4 The flowchart of the battery abnormality identification method provided by the embodiment of the application is shown. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. It should be understood that the accompanying drawings in the present application only serve the purpose of illustration and description, and are not used to limit the protection scope of the present application. In addition, it should be understood that the schematic drawings are not drawn according to the actual proportions. The flowcharts used in the present application show the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowcharts can not be implemented in sequence, and the steps without logical context relationship can be reversed in sequence or implemented simultaneously. In addition, one or more other operations can be added to the flowcharts or one or more operations can be removed from the flowcharts under the guidance of the content of the present application.

[0022] In addition, the described embodiments are only some of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] The optical fiber sensors in the prior art are mostly used only for temperature monitoring, and the refractive index change detection of the electrolyte state is not fully utilized. Although some lithium analysis detection technologies use optical fiber spectrum analysis, they rely on stress signal decoupling and are easily disturbed by mechanical vibration. The traditional optical fiber grating sensor also faces the problem of cross-influence of temperature and strain, and needs additional compensation algorithm, and the detection sensitivity of some refractive index sensors for high refractive index liquids is insufficient. In terms of integration and cost, the existing solutions often need to implant sensors in the battery, which may affect the battery sealing and safety, and the multi-sensor system leads to complex wiring and increases the calculation load of the battery management system (BMS). Based on this, the embodiments of the present application provide an optical fiber sensor, a battery module and a battery abnormality identification method, which integrate the optical fiber sensor in the battery module, and place the collection end of the mirror of the optical fiber sensor around the electrolyte vapor outlet outside the battery package, so as to analyze the temperature and refractive index of the electrolyte vapor through the reflected spectrum processed by the optical fiber sensor, and analyze whether the battery produces temperature abnormality or electrolyte abnormality, solving the technical problems that the electrolyte situation cannot be analyzed and the temperature detection timeliness is poor in the prior art, and achieving the technical effect of improving the timeliness of detecting the electrolyte and temperature. Specifically as follows: Please refer to Figure 1 and Figure 2 , Figure 1 The structure of an optical fiber sensor provided by the embodiments of the present applicationFigure 1 , Figure 2 A structure diagram of a fiber sensor provided by an embodiment of the present application Figure 2 . As shown in Figure 1 and Figure 2 , the fiber sensor provided by the embodiment of the present application comprises: a first DBR (Distributed Bragg Reflector); a transition metal layer MoS2, the first DBR being arranged on one side of the transition metal layer; a second DBR, the second DBR being arranged on the other side of the transition metal layer; an optical fiber 101, the side of the second DBR away from the transition metal layer being arranged at one end of the optical fiber; an optical fiber coupler 102, the optical fiber connecting end of the optical fiber coupler being connected to the other end of the optical fiber; a light emitting source 103, the light source connecting end of the optical fiber coupler being connected to the light emitting source; and a light receiver 104, the receiver connecting end of the optical fiber coupler being connected to the light receiver.

[0024] That is, the transition metal layer MoS2 is arranged between the first DBR and the second DBR, one side of the optical fiber is in contact with the side of the second DBR away from the transition metal layer, the other side of the optical fiber is connected to the optical fiber connecting end of the optical fiber coupler, the light source connecting end of the optical fiber coupler is connected to the light emitting source, and the receiver connecting end of the optical fiber coupler is connected to the light receiver. Thus, the light signal generated by the light emitting source is transmitted to the one side of the optical fiber through the other side of the optical fiber, and is refracted in turn by the second DBR, the transition metal layer MoS2 and the first DBR and then transmitted to the environment where the first DBR is located, reflected by the environment where the first DBR is located, and then transmitted to the light receiver in turn through the first DBR, the transition metal layer MoS2, the second DBR and the optical fiber. The light receiver can receive the reflected light to form a reflection spectrum.

[0025] In the reflection spectrum, the wavelength of each light source in the spectrum range generated by the light emitting source is taken as the abscissa, and the reflectivity of each light source wavelength received by the light receiver is taken as the ordinate.

[0026] For example, the optical fiber is a hollow optical fiber, the hollow part inside the optical fiber is filled with air or inert gas, and the light signal propagates in the hollow area by the principle of total reflection.

[0027] The transition metal layer forms a Tamm plasmon polariton (TPP) with the first DBR and the second DBR, respectively, that is, a special coupling mode of surface plasmon polariton and metal surface electron collective oscillation, and the local surface plasmon resonance is excited through the metal and dielectric interface local field enhancement effect, and the change of the environment refractive index at which the first DBR and the second DBR are located will cause the change of the reflection spectrum, so as to identify the change of the environment refractive index.

[0028] The target DBR includes a plurality of pairs of dielectric layers arranged in stacks, and the target DBR includes the first DBR or the second DBR, each pair of dielectric layers includes a dielectric layer with a first refractive index and a dielectric layer with a second refractive index, and the first refractive index and the second refractive index are different.

[0029] That is, for each pair of dielectric layers of the first DBR or the second DBR, the pair of dielectric layers includes a first dielectric layer with a first refractive index and a second dielectric layer with a second refractive index, the materials of the first dielectric layer and the second dielectric layer are different, and the first refractive index and the second refractive index are different. And the dielectric layers of the first DBR or the second DBR are alternately arranged, that is, the first dielectric layer and the second dielectric layer are alternately arranged in sequence, so that the two first dielectric layers are sandwiched by the second dielectric layer, and the two second dielectric layers are sandwiched by the first dielectric layer, that is, the same kind of dielectric layer is sandwiched by the different dielectric layer. Further, the first DBR and the second DBR are composed of alternately arranged first dielectric layers and second dielectric layers.

[0030] For example, the number of pairs of the first DBR can be set to 10 pairs, or 15 pairs, or 20 pairs, and the number of pairs of the second DBR can be set to 10 pairs, or 15 pairs, or 20 pairs. The number of pairs of the first DBR and the second DBR can be the same or different, which can be selected according to the space in the battery pack, or the highest accuracy can be selected through simulation results, which is not limited in the application.

[0031] And the thickness of the first dielectric layer and the second dielectric layer should satisfy the following formula: (1) In formula (1), refers to the thickness of the first dielectric layer or the second dielectric layer, refers to the light source wavelength of the light source, which can be randomly selected in the spectral range, or the center value of the spectral range can be directly selected, This refers to the refractive index of either the first or second dielectric layer, with a spectral range typically set between 300 and 800 nanometers. Since the materials of both the first and second dielectric layers are known, their thicknesses can be calculated using formulas. In other words, in... Calculated when the refractive index of the first dielectric layer is... The thickness of the first dielectric layer is... Calculated when the refractive index of the second dielectric layer is... The thickness of the second dielectric layer.

[0032] In this process, a first dielectric layer and a second dielectric layer are deposited at one end of the optical fiber using methods such as Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). For example, one of the first and second dielectric layers can be made of Si3N4 (silicon tetranitride) optical material, and the other can be made of SiO2 (silicon dioxide) optical material. Alternatively, one of the first and second dielectric layers can be made of Ta2O5 (tantalum pentoxide) optical material, and the other can be made of SiO2 (silicon dioxide) optical material. Furthermore, there should be a significant difference in refractive index between the first and second dielectric layers. The DBR constructed in this way can utilize this refractive index difference to achieve multiple reflections of light, so that the reflection spectrum can form a reflection peak when the optical Tamm state plasmon resonance is excited.

[0033] Furthermore, since the wavelength of the light source is known, and the materials of the first and second dielectric layers are known, the refractive indices of the first and second dielectric layers are also known. The thicknesses of the first and second dielectric layers can be calculated using formula (1). Moreover, the thicknesses of the first dielectric layer of the first DBR and the second dielectric layer of the second DBR are the same.

[0034] For example, the fiber optic sensor further includes a sensitive membrane for increasing the incident angle of the fiber optic sensor, wherein the sensitive membrane is disposed on the side of the first DBR away from the transition metal layer.

[0035] The material of the sensitive film can be any one of Al2O3 (alumina), ZnO (zinc oxide) and graphene. The material of the sensitive film only needs to increase the incident angle of the optical fiber sensor. The sensitive film should increase the incident angle of the refraction of the environment passing through the DBR of the optical fiber sensor, thereby increasing the detection sensitivity of the optical fiber sensor, so that the determined reflection spectrum is more accurate. For example, the thickness of Al2O3 (alumina) can be 50 nm (nanometer), and the thickness of ZnO (zinc oxide) can be 20 nm.

[0036] Please refer to Figure 3 , Figure 3 The structure of the battery module provided by the embodiment of the application is shown in the figure. Figure 3 As shown in the figure, the battery module comprises a packaging shell 301, at least one battery cell 302, each battery cell being located inside the packaging shell, and at least one optical fiber sensor 303, which refers to the optical fiber sensor as described in the above embodiment. One optical fiber sensor corresponds to one battery cell. For each optical fiber sensor, the collection end of the DBR of the optical fiber sensor is located inside the packaging shell and placed in a preset surrounding area of the electrolyte vapor outlet outside the battery cell packaging of the corresponding battery cell. The output end of the optical fiber coupler of the optical fiber sensor is arranged outside the packaging shell.

[0037] The electrolyte vapor outlet comprises the tab of the preset electrode of the battery cell packaging or the electrolyte injection inlet of the battery cell.

[0038] That is, N battery cells are placed in the packaging shell, and n target battery cells (n≥N) on which the optical fiber sensor is placed are selected from the N battery cells. One optical fiber sensor corresponds to only one target battery cell. In this way, the optical fiber sensor is placed around the tab of the preset electrode of the battery cell packaging of the target battery cell or the electrolyte injection inlet of the battery cell. The collection end of the DBR of the optical fiber sensor should be placed outside the battery cell packaging to avoid affecting the sealing and safety of the battery.

[0039] The tab of the preset electrode outside the battery cell packaging and the electrolyte injection inlet of the battery cell are the positions of the battery cell for sealing, so that the electrolyte vapor of the battery cell will overflow from these positions during use. Therefore, the optical fiber sensor can be placed at the preset surrounding area of the electrolyte vapor outlet of the battery cell to facilitate the analysis of the state of the electrolyte vapor by the optical fiber sensor.

[0040] Further, the collection end of the optical fiber sensor is arranged at the preset surrounding area of the electrolyte vapor outlet outside the cell package, so that the DBR of the optical fiber sensor is exposed to the environment where the electrolyte vapor is located, so that the light receiver of the optical fiber sensor can receive reflected light and correspondingly obtain a reflection spectrum. Moreover, the output end of the optical fiber coupler of the optical fiber sensor is led out of the packaging shell of the battery module, that is, the packaging shell of the battery module is provided with a wire outlet, and the optical fiber sensor is led out of the wire outlet, and the output end of the optical fiber coupler of the optical fiber sensor is led out of the battery module.

[0041] For example, the connection line of the processor of the battery module is connected to the inside of the packaging shell of the battery module from the wire outlet, for collecting the cell voltage value, the cell current value, the battery voltage value, the battery current value and other related battery module parameters of each cell of the battery module. The optical fiber coupler, the light emitting source and the light receiver of the optical fiber sensor can be integrated on the processor of the battery module, which refers to the battery management system (BMS) or the battery pack circuit breaking unit (BDU) of the battery module.

[0042] For example, the battery module further comprises at least one anti-bending optical fiber, wherein the at least one optical fiber sensor is bundled with the at least one anti-bending optical fiber into an optical cable, and one end of the optical cable where the optical fiber coupler is arranged outside the packaging shell.

[0043] That is, at least one anti-bending optical fiber is bundled with all the optical fiber sensors in the battery module into an optical cable, and the output side of the optical cable is led out of the wire outlet on the packaging shell to prevent the bending of the optical fiber sensor from affecting the propagation of light through the anti-bending optical fiber.

[0044] For example, six cells at different positions in one battery module can be selected to be equipped with optical fiber sensors, each optical fiber sensor has a diameter of 80 μm (microns), and two anti-bending optical fibers are selected to be bundled into an optical cable with a thickness of 0.3 mm (millimeters), so that the optical fiber sensors can be arranged in a high density in a limited space.

[0045] Further, in the application applied in the battery module, the refractive index of the electrolyte vapor permeating into the environment can be detected in real time. When the decomposition products (such as HF and carbonate solvents) of the electrolyte change, the refractive index will change, so that the decomposition of the electrolyte can be analyzed to determine whether there is an abnormality, so that the electrolyte can be detected without direct contact with the electrolyte, and the response is faster than the traditional electrochemical method, avoiding sensor contamination or failure.

[0046] Please refer to 4, Figure 4A flowchart of a battery abnormality identification method provided by an embodiment of the present application is shown in FIG. 4. The battery abnormality identification method is applied to the battery module described in the above embodiment. For example, the battery abnormality identification method is configured in the processor of the battery module. As shown in FIG. 4, the battery abnormality identification method includes the following steps. Figure 4 S401: obtaining the reflected light output by the output end of each optical fiber sensor in the battery module, and determining the target reflection spectrum corresponding to each optical fiber sensor.

[0047] That is, the reflected light output by the output end of each optical fiber sensor is received in real time, and the reflectivity at each light source wavelength of the reflected light is analyzed to obtain the continuous target reflection spectrum of each optical fiber sensor.

[0048] S402: for each optical fiber sensor, determining the first target center wavelength and the second target center wavelength of the optical fiber sensor from the target reflection spectrum corresponding to the optical fiber sensor.

[0049] The target center wavelength refers to the wavelength when the optical Tamm plasmon resonance is excited. In the present application, the first DBR and the second DBR are arranged on the two sides of the transition metal layer, and the transition metal layer and the first DBR and the second DBR form two metal-dielectric interfaces, i.e., the first DBR and the transition metal layer belong to one metal-dielectric interface, and the second DBR and the transition metal layer belong to another metal-dielectric interface. Due to the coupling effect of the metal-dielectric interface, low-frequency reflection peaks and high-frequency reflection peaks are formed at the two interfaces, and the two modes have different optical characteristics and responses. This phenomenon can be observed in the reflection spectrum as two peaks, and each peak corresponds to a different Tamm plasmon mode.

[0050] That is, both reflection peaks are produced when the optical Tamm plasmon resonance is excited, and the two reflections correspond to different target center wavelengths.

[0051] S403: determining the electrolyte refractive index and the electrolyte temperature corresponding to the first target center wavelength and the second target center wavelength of each optical fiber sensor according to the conversion relationship between the first target center wavelength and the ambient refractive index and the ambient temperature and the conversion relationship between the second target center wavelength and the ambient refractive index and the ambient temperature obtained by pre-simulation.

[0052] ​The conversion relationship between the center wavelength and the environmental refractive index is determined by the following manner: after the simulation structure of the collection end of the optical fiber sensor and the reference temperature thereof are built, the collection end of the optical fiber sensor is changed to be in different environmental refractive indexes, and the reflection spectrum under each environmental refractive index is collected; the first preset center wavelength of the reflection spectrum corresponding to each environmental refractive index is subjected to data fitting to determine a first refractive index conversion relationship between the first preset center wavelength and the environmental refractive index, and the second preset center wavelength of the reflection spectrum corresponding to each environmental refractive index is subjected to data fitting and a second refractive index conversion relationship between the second preset center wavelength and the environmental refractive index.

[0053] Specifically, the conversion relationship between the center wavelength and the environmental temperature is determined by the following manner: after the simulation structure of the collection end of the optical fiber sensor and the reference refractive index thereof are built, the collection end of the optical fiber sensor is changed to be in different environmental temperatures, and the reflection spectrum under each environmental temperature is collected; the third preset center wavelength of the reflection spectrum corresponding to each environmental temperature is subjected to data fitting to determine a first temperature conversion relationship between the third preset center wavelength and the environmental temperature, and the fourth preset center wavelength of the reflection spectrum corresponding to each environmental temperature is subjected to data fitting to determine a second temperature conversion relationship between the fourth preset center wavelength and the environmental temperature.

[0054] That is, the first target center wavelength, the first preset center wavelength and the third preset center wavelength are all in the same Tamm plasmon mode, and the Tamm plasmon mode corresponds to one of the low-frequency reflection peak and the high-frequency reflection peak; the second target center wavelength, the second preset center wavelength and the fourth preset center wavelength are all in the same Tamm plasmon mode, and the Tamm plasmon mode corresponds to the other of the low-frequency reflection peak and the high-frequency reflection peak.

[0055] Exemplarily, a simulation structure of a collection end of an optical fiber sensor is built by FDTD Solutions simulation software, and the simulation structure of the first DBR and the simulation structure of the first DBR are simulated by building the simulation structure of the first dielectric layer and the second dielectric layer layer by layer. The reference temperature of the collection end of the optical fiber sensor is set to be unchanged, the environmental refractive index is changed to obtain the reflection spectrum corresponding to different environmental refractive indexes. Then, for each environmental refractive index, the first preset center wavelength corresponding to the low-frequency reflection peak and the second preset center wavelength corresponding to the high-frequency reflection peak are identified on the reflection spectrum corresponding to the environmental refractive index.

[0056] Exemplarily, the first preset central wavelength corresponding to the low-frequency reflection peak under each environment refractive index is taken as the dependent variable to perform data fitting with the environment refractive index as the independent variable, so as to determine a first refractive index conversion relationship between the first preset central wavelength and the environment refractive index; and the second preset central wavelength corresponding to the high-frequency reflection peak under each environment refractive index is taken as the dependent variable to perform data fitting with the environment refractive index as the independent variable, so as to determine a second refractive index conversion relationship between the second preset central wavelength and the environment refractive index.

[0057] Exemplarily, after the simulation structure of the first DBR and the simulation structure of the first DBR are built, the reference refractive index in which the collection end of the fiber sensor is located is set to be unchanged, and the reflection spectrum corresponding to different environment temperatures is obtained by changing the environment temperature. Further, for each environment temperature, the third preset central wavelength corresponding to the low-frequency reflection peak and the fourth preset central wavelength corresponding to the high-frequency reflection peak are identified on the reflection spectrum corresponding to the environment temperature. Thus, the third preset central wavelength corresponding to the low-frequency reflection peak under each environment temperature is taken as the dependent variable to perform data fitting with the environment temperature as the independent variable, so as to determine a first temperature conversion relationship between the third preset central wavelength and the environment temperature; and the fourth preset central wavelength corresponding to the high-frequency reflection peak under each environment temperature is taken as the dependent variable to perform data fitting with the environment temperature as the independent variable, so as to determine a second temperature conversion relationship between the fourth preset central wavelength and the environment temperature.

[0058] Specifically, the electrolyte refractive index and the electrolyte temperature corresponding to the first target central wavelength and the second target central wavelength of each fiber sensor are determined by the following manner: the conversion relationship between the first preset central wavelength and the environment refractive index and the conversion relationship between the second preset central wavelength and the environment temperature obtained by pre-simulation are used to establish a cross-sensitivity matrix; the refractive index variable for the reference refractive index and the temperature variable for the reference temperature of each fiber sensor are calculated according to the difference between the first target central wavelength and the second target central wavelength of each fiber sensor and the reference central wavelength, and in combination with the cross-sensitivity matrix; the electrolyte refractive index of each fiber sensor is calculated by the refractive index variable of each fiber sensor and the reference refractive index, and the electrolyte temperature of each fiber sensor is calculated by the temperature variable of each fiber sensor and the reference temperature.

[0059] Exemplarily, the cross-sensitivity matrix is represented by the following manner: (2) In formula (2), is the difference between the dependent variables of the fitting functions of the first refractive index conversion relationship and the first temperature conversion relationship corresponding to the low-frequency reflection peak, a slope of a fitting function of a first temperature conversion relationship corresponding to the low-frequency reflection peak, a slope of a fitting function of a first temperature conversion relationship corresponding to the low-frequency reflection peak, a dependent variable difference of fitting functions of a second temperature conversion relationship and a second refractive index conversion relationship corresponding to the high-frequency reflection peak, a slope of a fitting function of a second temperature conversion relationship corresponding to the high-frequency reflection peak, a slope of a fitting function of a second temperature conversion relationship corresponding to the high-frequency reflection peak, a refractive index variable for a reference refractive index, a temperature variable for a reference temperature. Since the slope of the fitting function mainly affects the identification accuracy of the optical fiber sensor, the intercept of the fitting function is selected to be ignored here, and only the slope of the fitting function is considered to construct the cross-sensitivity matrix.

[0060] For example, the reference temperature can be a conventional room temperature, and the reference refractive index can refer to the electrolyte refractive index of the battery when not in use. In this way, the refractive index variable and the temperature variable can be calculated by formula (2), and the sum of the reference refractive index and the refractive index variable is the electrolyte refractive index analyzed by the optical sensor, and the sum of the reference temperature and the temperature variable is the electrolyte temperature analyzed by the optical sensor.

[0061] S404: According to the electrolyte refractive index and the electrolyte temperature, it is determined whether the battery module is in an abnormal state.

[0062] Further, whether the battery module produces electrolyte abnormality can be analyzed by judging whether the electrolyte refractive index falls into the electrolyte refractive index abnormal range in the fault case, and whether the battery module produces temperature abnormality can be analyzed by judging whether the electrolyte temperature falls into the electrolyte temperature abnormal range, so that whether the battery module is in an abnormal state and the actual abnormal state when in an abnormal state can be identified.

[0063] Exemplarily, in the process of simulation, the application can also modify various simulation parameters of the collection end of the optical fiber sensor to select the optimal simulation parameters for the actual production of the optical fiber sensor. The simulation parameters of the collection end of the optical fiber sensor can include the number of medium pairs of the first DBR, the number of medium pairs of the second DBR, the thickness of the transition metal layer, the material of the sensitive film, the thickness of the sensitive film, and the like. The application can also calculate the quality factor (Q value) of the optical fiber sensor through the ratio of the preset central wavelength corresponding to the low-frequency reflection peak to the wavelength range involved or through the ratio of the preset central wavelength corresponding to the high-frequency reflection peak to the wavelength range involved. The sensor with a high Q value is generally more stable and less affected by environmental factors such as temperature and humidity, and thus the Q value can be calculated by changing the number of medium pairs and the like during the simulation process to select the simulation parameters with a higher Q value to correspond to the design of the optical fiber sensor.

[0064] Further, the optical fiber sensor of the application can find that the central wavelength has drifted when the electrolyte has decomposed abnormally, and the response time is shortened to 30 ms (milliseconds). Compared with the traditional optical fiber sensor scheme, this structure can better control the manufacturing cost (without the need for noble metal deposition) while maintaining high sensitivity. Experiments show that when the wavelength range of the reflection peak is greater than 0.15 nm, the electrolyte can be warned to produce lithium precipitation, the response time is less than 200 ms, which is 10 times faster than ultrasonic detection, and the spatial resolution (the ability of the imaging system to distinguish between two adjacent objects) reaches 0.5 mm, which can accurately locate the lithium precipitation area. Further, when the electrolyte produces lithium precipitation, it will cause the refractive index of the electrolyte overflowing the battery to change, and the optical fiber sensor can identify the battery pack with a changed refractive index, so as to locate the battery pack with lithium precipitation in multiple battery packs.

[0065] Moreover, by integrating the optical fiber sensor with the bend-resistant optical fiber, and integrating the output end of the optical fiber sensor with the processor of the battery module through a flexible PCB, and since the first DBR and the second DBR are a layer-by-layer coating structure, they can be unaffected by mechanical vibration, i.e., they meet the requirements of vehicle-level vibration, the cost of a single node is reduced by 57%, and they support CAN bus access to the BMS system, realizing high-performance and cost-effective non-destructive real-time monitoring. Moreover, since the cladding of the first DBR and the second DBR is relatively thick, the influence of the core of the optical fiber itself on environmental factors such as temperature and strain can also be avoided.

[0066] Further, compared with the traditional method, the scheme can provide an early warning of 30 seconds in the 4C fast charging test, and provides an innovative solution for the safety of power battery fast charging. Moreover, the temperature stability is improved compared with the traditional single TPP structure, and a certain detection accuracy is maintained in a wide temperature range of-40 DEG C to 85 DEG C, and the problem of signal drift under complex working conditions is completely solved. And through the non-invasive installation mode, the micro-channel structure is spirally wound along the heat sealing edge of the aluminum plastic film of the battery cell, and the electrolyte vapor is guided to the sensing area. More breakthrough is that the system can synchronously obtain multi-dimensional data such as refractive index and temperature, and improve the accuracy of lithium precipitation warning.

[0067] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the foregoing method embodiment, which will not be repeated here. In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented by other ways. The device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some communication interface, device or unit, which can be electrical, mechanical or other forms.

[0068] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or they can be distributed on multiple network units. According to actual needs, part or all of the units can be selected to achieve the purpose of the embodiment scheme.

[0069] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0070] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a nonvolatile computer readable storage medium executable by a processor. Based on this understanding, the technical solutions of the present application or the parts of the present application that essentially contribute to the prior art or the parts of the technical solutions can be embodied in the form of software products. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0071] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An optical fiber sensor, characterized in that, The fiber optic sensor includes: First Distributed Bragg Mirror (DBR); A transition metal layer, wherein a first DBR is disposed on one side of the transition metal layer; The second DBR is disposed on the other side of the transition metal layer; An optical fiber, wherein the side of the second DBR away from the transition metal layer is disposed at one end of the optical fiber; An optical fiber coupler, wherein the optical fiber connector of the optical fiber coupler is connected to the other end of the optical fiber; A light source, wherein the light source is connected to the light source connection end of the optical fiber coupler; An optical receiver is connected to the receiver connection end of the optical fiber coupler.

2. The fiber optic sensor according to claim 1, characterized in that, The fiber optic sensor also includes a sensitive membrane for increasing the incident angle of the fiber optic sensor. The sensitive membrane is disposed on the side of the first DBR away from the transition metal layer.

3. The fiber optic sensor according to claim 1, characterized in that, The target DBR comprises multiple pairs of dielectric layers stacked together, and the target DBR includes either the first DBR or the second DBR. Each pair of dielectric layers includes a dielectric layer with a first refractive index and a dielectric layer with a second refractive index, wherein the first refractive index and the second refractive index are different.

4. A battery module, characterized in that, The battery module includes: Encapsulation shell; At least one battery cell, with each battery cell located inside the package housing; At least one fiber optic sensor, wherein the fiber optic sensor refers to the fiber optic sensor as described in any one of claims 1 to 3, one fiber optic sensor corresponds to one battery cell, and for each fiber optic sensor, the acquisition end where the reflector of the fiber optic sensor is located is located inside the package housing and placed in a predetermined surrounding area of ​​the electrolyte vapor outlet outside the battery cell package of the corresponding battery cell, and the output end where the fiber optic coupler of the fiber optic sensor is located is located outside the package housing.

5. The battery module according to claim 4, characterized in that, The electrolyte vapor outlet includes the tab of the preset electrode of the battery cell or the electrolyte injection port of the battery cell.

6. The battery module according to claim 4 or 5, characterized in that, The battery module also includes at least one bend-resistant optical fiber. In this configuration, at least one optical fiber sensor and at least one bend-resistant optical fiber are bundled together to form an optical cable, with one end of the optical cable containing the optical fiber coupler located outside the encapsulation housing.

7. A method for identifying battery anomalies, characterized in that, The method is applied to the battery module as described in any one of claims 4 to 6. The method includes: The reflected light output from the output end of each fiber optic sensor in the battery module is obtained, and the target reflection spectrum corresponding to each fiber optic sensor is determined. For each fiber optic sensor, the first target center wavelength and the second target center wavelength of the fiber optic sensor are determined from the target reflection spectrum corresponding to the fiber optic sensor. The target center wavelength refers to the wavelength at which optical Tahm state plasma resonance is excited. Based on the conversion relationships between the first target center wavelength and the ambient refractive index and ambient temperature obtained from the pre-simulation, and the conversion relationships between the second target center wavelength and the ambient refractive index and ambient temperature, the electrolyte refractive index and electrolyte temperature corresponding to the first target center wavelength and the second target center wavelength of each fiber optic sensor are determined. The battery module is determined to be in an abnormal state based on the refractive index and temperature of the electrolyte.

8. The method according to claim 7, characterized in that, The conversion relationship between the center wavelength and the ambient refractive index is determined in the following way: After constructing the simulation structure of the acquisition end of the fiber optic sensor and its reference temperature, the refractive index of the acquisition end of the fiber optic sensor is changed to different environments, and the reflection spectrum under each refractive index is acquired. Data fitting is performed on the first preset center wavelength of the reflection spectrum corresponding to each environmental refractive index to determine the first preset center wavelength and the first refractive index conversion relationship between the first preset center wavelength and the environmental refractive index. Data fitting is performed on the second preset center wavelength of the reflection spectrum corresponding to each environmental refractive index, and the second refractive index conversion relationship between the second preset center wavelength and the environmental refractive index is determined.

9. The method according to claim 7, characterized in that, The conversion relationship between the center wavelength and ambient temperature is determined in the following way: After constructing the simulation structure of the acquisition end of the fiber optic sensor and its reference refractive index, the acquisition end of the fiber optic sensor is subjected to different ambient temperatures, and the reflection spectrum at each ambient temperature is collected. Data fitting is performed on the third preset center wavelength of the reflectance spectrum corresponding to each ambient temperature to determine the first temperature conversion relationship between the third preset center wavelength and the ambient temperature. Data fitting is performed on the fourth preset center wavelength of the reflection spectrum corresponding to each ambient temperature to determine the second temperature conversion relationship between the fourth preset center wavelength and the ambient temperature.

10. The method according to claim 7, characterized in that, The electrolyte refractive index and electrolyte temperature corresponding to the first target center wavelength and the second target center wavelength of each fiber optic sensor were determined in the following manner: A cross-sensitivity matrix is ​​established by using the conversion relationships between the first target center wavelength and the environmental refractive index and environmental temperature obtained from pre-simulation, as well as the conversion relationships between the second target center wavelength and the environmental refractive index and environmental temperature. Based on the differences between the first target center wavelength and the second target center wavelength of each fiber optic sensor and the reference center wavelength, the refractive index variable and the temperature variable relative to the reference refractive index of each fiber optic sensor are calculated using the cross-sensitivity matrix. The electrolyte refractive index of each fiber optic sensor is calculated using the refractive index variable and the reference refractive index of each fiber optic sensor, and the electrolyte temperature of each fiber optic sensor is calculated using the temperature variable and the reference temperature of each fiber optic sensor.

Images