CN117387686A - Lithium battery multi-physical-quantity measuring system - Google Patents

Lithium battery multi-physical-quantity measuring system Download PDF

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Publication number
CN117387686A
CN117387686A CN202311262207.1A CN202311262207A CN117387686A CN 117387686 A CN117387686 A CN 117387686A CN 202311262207 A CN202311262207 A CN 202311262207A CN 117387686 A CN117387686 A CN 117387686A
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coupler
lithium battery
optical fiber
circulator
detector
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刘飞
崔飞
王本章
周娴
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University of Science and Technology Beijing USTB
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University of Science and Technology Beijing USTB
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
    • G01D5/35312—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Fabry Perot
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35383—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/171—Systems in which incident light is modified in accordance with the properties of the material investigated with calorimetric detection, e.g. with thermal lens detection

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  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

The invention provides a lithium battery multi-physical-quantity measuring system in the field of lithium battery physical quantity measurement, which specifically comprises: the system comprises an optical fiber to be tested, a pump laser, an optical amplifier, a detection light path, an intensity modulator, a fourth coupler, a wavelength division multiplexer, a measurement interferometer, an auxiliary interferometer, a data acquisition card and an upper computer: the invention combines the optical fiber photo-thermal spectrum system and the OFDR together, the two sets of systems share the pumping laser, and the data upper computer also shares the pumping laser; the FP cavity for measuring the gas concentration is connected with the FUT in series, wherein the photo-thermal spectrum system for measuring the gas concentration usually uses 1550nm light waves for detection, the OFDR system adopts a pump light system for detection, and the light wave ranges of the FP cavity and the FUT do not interfere with each other.

Description

Lithium battery multi-physical-quantity measuring system
Technical Field
The invention relates to the field of lithium battery physical quantity measurement, in particular to a lithium battery multi-physical quantity measurement system.
Background
Lithium batteries are receiving increasing attention as key devices. Compared with other chemical power sources, the lithium battery has the advantages of long storage and cycle life, large charge and discharge multiplying power, high energy density, small environmental pollution, wide working range and the like, and is widely applied to the fields of new energy automobiles, smart phones, intelligent robots and the like, and has a wide prospect. However, lithium batteries have been challenged during use with thermal runaway, which is triggered for three reasons including mechanical abuse, electrical abuse, and thermal abuse. Particularly in the application fields of new energy automobiles and the like requiring high-capacity and large-volume batteries, the high-rate charge and discharge of the lithium battery inevitably generates a large amount of heat, and in a narrow space, the heat is extremely easy to accumulate to cause thermal runaway of the battery. And further causes battery failure, burning and even explosion, resulting in huge property loss and personal injury. Therefore, monitoring the thermal effect of the lithium battery and early warning the thermal runaway condition of the lithium battery are important in the safe use of the lithium battery.
In lithium battery modules currently in commercial use, battery management systems (Battery Management System, BMS) are mainly relied upon to monitor the batteries. The method relies on various embedded electrical sensors to acquire parameter information such as voltage, current, temperature and the like of partial nodes in a lithium battery module, and then combines a specific signal processing algorithm to judge the State of charge (SOC) and the State of Health (SOH) of the battery, so as to judge the thermal effect State of the whole battery. When the BMS system judges that the battery is thermally abnormal, corresponding measures can be taken in time, including power supply shutdown, cooling system startup and the like. However, the BMS system of the current lithium battery system has some limitations. For example, only voltage, current and temperature information of a limited number of points can be obtained, and it is difficult to obtain state information of the whole lithium battery; the monitored information is only the state of the surface of the battery, and key information in the battery cannot be monitored for the battery with the earliest thermal runaway; the physical quantity monitored is single, for example, the gas composition and concentration sensing which are the most important for predicting the thermal runaway of the battery are not related to the existing BMS. Therefore, researchers have proposed that one of the directions of development of the future intelligent lithium battery BMS system is an internal in-situ, multi-dimensional and multi-point monitoring method.
The BMS at present has the following defects when monitoring the lithium battery: (1) limited measurement data points. In many cases, thermal runaway initially occurs in a localized area and then extends to the entire battery pack, and limited measurement points cannot find thermal runaway in time; (2) the sensors of the BMS can be disposed only on the surface of the battery. Most thermal runaway problems occur first inside the battery with some hysteresis or inability to conduct to the surface of the battery; (3) the BMS acquires multidimensional electrical quantity information. In thermal runaway, mechanical quantity changes can also provide useful information. It has been shown that prior to the occurrence of thermal runaway, the lithium battery surface strain values are abnormal, are linearly related to SOH, and can be predicted earlier than the temperature data.
Disclosure of Invention
The embodiment of the invention provides a lithium battery multi-physical-quantity measuring system, which aims to solve one of the technical problems in the related art at least to a certain extent, improves the efficiency of measuring the physical quantity of a lithium battery, and adopts the following scheme:
a lithium battery multi-physical measurement system, comprising:
the optical fiber to be measured is connected with the lithium battery to be measured;
the output end of the pumping laser is respectively connected with the optical amplifier and the fourth coupler through the third coupler;
the output end of the optical amplifier is connected with the intensity modulator;
the detection light path is used for emitting detection light and is respectively connected with the wavelength division multiplexer, the intensity modulator and the upper computer;
the output end of the intensity modulator is sequentially connected with an isolator, a first coupler and a wavelength division multiplexer, and the intensity modulator modulates the intensity of received light waves through a modulation signal output by the detection light path, wherein the isolator is used for unidirectionally transmitting the light waves output by the intensity modulator into the wavelength division multiplexer;
the output end of the fourth coupler is respectively connected with the measuring interferometer and the auxiliary interferometer; the measuring interferometer transmits the received light waves to the wavelength division multiplexer through a first coupler, the measuring interferometer transmits the light waves transmitted back from the wavelength division multiplexer to a third detector, and the output end of the third detector is connected with the data acquisition card;
the output end of the auxiliary interferometer is connected with the fourth detector, and the output end of the fourth detector is connected with the data acquisition card;
the wavelength division multiplexer is used for combining the detection light wave emitted by the detection light path, the pump light wave modulated by the intensity modulator and the light wave emitted by the measurement interferometer, transmitting the combined light wave into the optical fiber to be measured for acting, and enabling the light wave acted in the optical fiber to be measured to be transmitted to the detection light path and the measurement interferometer in a branching way through the wavelength division multiplexer;
the data acquisition card is connected with the upper computer, and the upper computer outputs the internal gas concentration information of the lithium battery to be tested, the temperature of the lithium battery to be tested and the stress change of the lithium battery to be tested according to the received data.
Preferably, the optical fiber to be measured includes: bare optical fiber, loose tube and FP cavity;
one end of the bare optical fiber is connected with the wavelength division multiplexer, the other end of the bare optical fiber is provided with the FP cavity, and the FP cavity is arranged in the lithium battery to be tested;
and one part of the bare optical fiber is directly spirally wound on the outer wall of the lithium battery to be tested, and the other part of the bare optical fiber is spirally wound on the outer wall of the lithium battery to be tested after being mounted on the loose tube.
Preferably, the detection light path includes:
the detection laser is used for emitting laser and is respectively connected with the first circulator and the servo controller;
the first interface of the first circulator is connected with the detection laser, the second interface of the first circulator is connected with the wavelength division multiplexer, and the third interface of the first circulator is connected with the second coupler;
the second coupler divides the light wave signals output by the third interface of the first circulator into two paths, one path of light wave signals output by the third interface of the first circulator is transmitted to the first detector by the second coupler, and the other path of light wave signals output by the third interface of the first circulator is transmitted to the second detector by the second coupler;
the first detector converts the received light wave signals into electric signals and then transmits the electric signals to the servo controller;
the second detector converts the received light wave signal into an electric signal and then transmits the electric signal to the lock-in amplifier;
the phase-locked amplifier is respectively connected with the intensity modulator and the upper computer, and after the phase-locked amplifier demodulates the phase modulation generated by the gas photo-thermal effect in the lithium battery to be detected, the phase-locked amplifier transmits signals to the upper computer, and the upper computer processes the signals to obtain the concentration of the gas in the lithium battery to be detected.
Preferably, the measurement interferometer comprises:
a sixth coupler, the sixth coupler transmitting the received optical wave component stream transmitted by the fourth coupler to a second circulator and an intrinsic optical path;
the first interface of the second circulator is connected with the sixth coupler, the second interface of the second circulator is connected with the first coupler through a sensing light path, and the third interface of the second circulator is connected with the seventh coupler;
the output end of the intrinsic optical path is connected with a seventh coupler;
and a seventh coupler connected with the third detector.
Preferably, the auxiliary interferometer includes:
a fifth coupler, which transmits the received light wave component stream transmitted by the fourth coupler into two Faraday rotary mirrors;
a delay optical fiber is arranged between one Faraday rotator mirror and the fifth coupler;
and the optical wave original paths processed by the two Faraday rotary mirrors return to the fifth coupler, and the fifth coupler transmits the optical wave processed by the Faraday rotary mirrors to the fourth detector.
Preferably, the FP cavity diameter is less than 2mm.
Preferably, the bare fiber has a diameter of less than 250 μm.
Preferably, the spectral coefficient of the third coupler is 50%:50%.
Preferably, the spectral coefficient of the fourth coupler is 1%:99%, wherein 1% of the light waves enter the auxiliary interferometer.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
1) Combining the optical fiber photo-thermal spectrum system and the OFDR together, wherein the two sets of systems share a sweep frequency light source (also referred to as a 'pump laser') and the data processing system (namely a computer in FIG. 1) at the same time;
2) The FP cavity for measuring the gas concentration is connected with the FUT in series, wherein the photo-thermal spectrum system for measuring the gas concentration usually uses 1550nm light waves for detection, the OFDR system adopts a pump light system as a detection light source, and the light wave ranges of the FP cavity and the FUT do not interfere with each other, so that simultaneous measurement of multiple physical quantities can be realized simultaneously;
3) In order to realize the measurement of multiple physical quantities of the lithium battery, the invention designs a specific optical fiber arrangement mode, divides the optical fiber to be measured into three sections, and simultaneously realizes the measurement of the external strain of the battery, the internal and external temperature of the battery and the internal gas concentration of the battery. The bare optical fiber has the advantages of small diameter (250 mu m), corrosion resistance, electromagnetic interference resistance and the like, and meanwhile, the diameter of the FP cavity of the optical fiber manufactured by the bare optical fiber can be very small (2 mm), so that the bare optical fiber is very suitable for monitoring the internal physical quantity of a lithium battery. Meanwhile, the OFDR system can be used for forming distributed temperature and strain measurement, and multidimensional data are provided for monitoring the thermal effect of the lithium battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a device according to the present invention;
fig. 2 (a) is a schematic diagram of an external arrangement of an optical fiber to be measured on a lithium battery to be measured;
fig. 2 (b) is a schematic diagram of the arrangement of the optical fiber to be measured inside the lithium battery to be measured.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without creative efforts, based on the described embodiments of the present invention fall within the protection scope of the present invention.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first," "second," and the like, as used herein, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a," "an," or "the" and similar terms do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
It should be noted that "upper", "lower", "left", "right", "front", "rear", and the like are used in the present invention only to indicate a relative positional relationship, and when the absolute position of the object to be described is changed, the relative positional relationship may be changed accordingly.
Fiber optic sensors are considered as a potentially effective means of lithium battery thermal runaway monitoring. Compared with the traditional electronic sensor, the lithium battery in-situ monitoring device has the advantages of high sensitivity, small volume, electromagnetic interference resistance, good electrical insulation and the like, and is very suitable for lithium battery in-situ monitoring. Meanwhile, the optical fiber sensor can easily use a single optical fiber to finish multiplexing and distributed measurement, can provide multi-point information of the lithium battery and the module, and helps the BMS system to judge more accurate thermal effects. At the same time, multiplexing and distribution capabilities are also beneficial to reduce the cost of a single measurement point. At present, a plurality of research groups try to apply the optical fiber sensor to the thermal effect monitoring of the lithium battery at home and abroad. For example, in the prior art, in actual operation, a femtosecond etching FBG is adopted, and temperature data with higher signal to noise ratio is obtained by being built in a lithium battery, so that in-situ and continuous monitoring is realized.
For the above reasons, the present invention aims to provide a lithium battery multi-physical-quantity measurement system, as shown in fig. 1, specifically including: the system comprises an optical fiber to be tested, a pump laser, an optical amplifier, a detection light path, an intensity modulator, a fourth coupler, a wavelength division multiplexer, a measurement interferometer, an auxiliary interferometer, a data acquisition card and an upper computer:
the optical fiber to be measured is connected with the lithium battery to be measured; the output end of the pump laser is respectively connected with the optical amplifier and the fourth coupler through the third coupler; the output end of the optical amplifier is connected with the intensity modulator; the detection light path is used for emitting detection light and is respectively connected with the wavelength division multiplexer, the intensity modulator and the upper computer; the output end of the intensity modulator is sequentially connected with an isolator, a first coupler and a wavelength division multiplexer, the intensity modulator modulates the intensity of received light waves through a modulation signal output by the detection light path, and the isolator is used for unidirectionally transmitting the light waves output by the intensity modulator into the wavelength division multiplexer; the output end of the fourth coupler is respectively connected with the measurement interferometer and the auxiliary interferometer; the measuring interferometer transmits the received light waves to the wavelength division multiplexer through a first coupler, the measuring interferometer transmits the light waves transmitted back from the wavelength division multiplexer to a third detector, and the output end of the third detector is connected with the data acquisition card; the output end of the auxiliary interferometer is connected with the fourth detector, and the output end of the fourth detector is connected with the data acquisition card; the wavelength division multiplexer combines the detection light wave emitted by the detection light path, the pumping light wave modulated by the intensity modulator and the light wave emitted by the measurement interferometer, the combined light wave is transmitted to the optical fiber to be measured for action, and the light wave acted in the optical fiber to be measured is transmitted to the detection light path and the measurement interferometer in a branching way through the wavelength division multiplexer; the data acquisition card is connected with the upper computer, and the upper computer outputs the internal gas concentration information of the lithium battery to be tested, the temperature of the lithium battery to be tested and the stress change of the lithium battery to be tested according to the received data.
Wherein, the optical fiber to be measured includes: the device comprises a bare optical fiber, a loose tube and an FP cavity, wherein one end of the bare optical fiber is connected with a wavelength division multiplexer, the other end of the bare optical fiber is provided with the FP cavity, and the FP cavity is arranged in the lithium battery to be tested; and one part of the bare optical fiber is directly spirally wound on the outer wall of the lithium battery to be tested, and the other part of the bare optical fiber is spirally wound on the outer wall of the lithium battery to be tested after being mounted on the loose tube.
The detection light path includes: the device comprises a detection laser, a first circulator, a second coupler, a first detector, a second detector and a lock-in amplifier, wherein the detection laser is used for emitting laser, and the detection laser is respectively connected with the first circulator and a servo controller; the first interface of the first circulator is connected with the detection laser, the second interface of the first circulator is connected with the wavelength division multiplexer, and the third interface of the first circulator is connected with the second coupler; the second coupler divides the light wave signals output by the third interface of the first circulator into two paths, one path of light wave signals output by the third interface of the first circulator is transmitted to the first detector by the second coupler, and the other path of light wave signals output by the third interface of the first circulator is transmitted to the second detector by the second coupler; the first detector converts the received light wave signals into electric signals and then transmits the electric signals to the servo controller; the second detector converts the received light wave signal into an electric signal and then transmits the electric signal to the lock-in amplifier; the phase-locked amplifier is respectively connected with the intensity modulator and the upper computer, and after the phase-locked amplifier demodulates the phase modulation generated by the gas photo-thermal effect in the lithium battery to be detected, the phase-locked amplifier transmits signals to the upper computer, and the upper computer processes the signals to obtain the concentration of the internal gas of the lithium battery to be detected.
As shown in fig. 1, the system mainly comprises a photothermal spectrum system and an optical frequency domain reflection (Optical Frequency Domain Reflectometry, OFDR) system, wherein the photothermal spectrum system is mainly used for measuring the concentration of gas in a lithium battery, and can be further divided into the following pumping light part, detection light part, and air chamber part, and the composition and functions of each part are as follows: (1) a pump light portion: and selecting a pumping laser with a proper wave band according to the type of the gas in the lithium battery to be detected. The wavelength of the pumping laser can be scanned near the gas absorption line, and the scanning range is about 1 nm-2 nm. In order to achieve a certain detection precision, an optical amplifier can be used for amplifying an optical wave signal output by a pump laser, and after the amplified optical wave passes through an intensity modulator and an isolator, the optical wave is combined with detection light in an OFDR system through a coupler 1, and then the combined beam passes through a Wavelength division multiplexer (Wavelength DivisionMultiplexer, WDM) and the detection light to enter a small air chamber formed by a Fabry-Perot (FP) cavity; the amplified light wave is subjected to intensity modulation, a modulation signal is from a phase-locked amplifier, and the purpose of adding modulation is to improve gas detection; (2) detecting a light portion: the probe light is typically a commercial near infrared narrow linewidth laser, such as a fiber laser at a wavelength around 1550 nm. The detection light is output from the second port after passing through the first port of the first circulator, enters the air chamber after being combined with the pumping light through WDM, returns from the air chamber and passes through the third port of the first circulator, is divided into two paths by the second coupler after passing through the third port of the first circulator, is received by the two detectors (the first detector and the second detector) respectively, and is converted into an electric signal. After the signal output by the first detector is sent to a servo controller, the output voltage of the servo controller adjusts the wavelength of the detection laser to enable the detection laser to work on the orthogonal working point of the return interference signal; the output signal of the second detector enters a phase-locked amplifier, the phase-locked amplifier demodulates the output signal to obtain the phase modulation generated by the gas photo-thermal effect, and then the modulation signal is sent into an upper computer for processing to obtain the concentration of the gas in the battery; (3) a plenum portion: the gas cell portion is shown in the graph (b) of fig. 2, and the gas cell is formed by an extrinsic optical fiber FP interferometer (i.e., FP cavity) which can be smaller than 1mm in diameter, thus being capable of being placed inside a lithium battery to detect the concentration of the internal gas; meanwhile, the diaphragm can be adopted outside the interferometer to enable gas in electrolyte inside the lithium battery to enter the FP cavity, so that pumping light and gas to be detected interact in the FP cavity to generate a photo-thermal signal, and the phase of an optical path is modulated. Note that the plenum is after the bare Fiber portion that is connected in the Fiber Under Test (FUT).
In a preferred embodiment, the measurement interferometer comprises: a sixth coupler, a second circulator, an intrinsic optical path, and a seventh coupler; the sixth coupler transmits the received light wave component stream transmitted by the fourth coupler to a second circulator and an intrinsic light path; the first interface of the second circulator is connected with the sixth coupler, the second interface of the second circulator is connected with the first coupler through a sensing light path, and the third interface of the second circulator is connected with the seventh coupler; the output end of the intrinsic optical path is connected with a seventh coupler; the seventh coupler is connected with the third detector.
In a preferred embodiment, the auxiliary interferometer comprises: the optical fiber coupler comprises a fifth coupler, a delay optical fiber and two Faraday rotary mirrors, wherein the fifth coupler transmits the received light wave component flow transmitted by the fourth coupler into the two Faraday rotary mirrors; a delay optical fiber is arranged between one Faraday rotator mirror and the fifth coupler; and the optical wave original paths processed by the two Faraday rotary mirrors return to the fifth coupler, and the fifth coupler transmits the optical wave processed by the Faraday rotary mirrors to the fourth detector.
In particular one embodiment. The pump light in the photothermal spectrum gas concentration detection system is subjected to linear scanning, and the light source can be further used for measuring the temperature and stress of a lithium battery. The composition and function of the various parts of the OFDR system of the present invention are described below. (1) A sweep light source part, namely a pump laser of the photo-thermal spectrum system, which needs to use a wavelength scanning light source, so that the part can be shared, and a third coupler can be used for dividing light waves output by the scanning light source into a photo-thermal spectrum system and an OFDR system (the light splitting coefficient is suggested to be 50%: 50%); (2) The auxiliary interferometer part, the sweep frequency light source light wave output by the third coupler passes through the fourth coupler (the spectral coefficient is suggested to be 1 percent to 99 percent) and then enters a Mach-Zehnder (MZ) interferometer (1 percent of light wave of one path), and the MZ interferometer consists of a fifth coupler, two Faraday gyros (Faraday Rotation Mirror, FRM) at the tail end and a section of delay optical fiber. The auxiliary interferometer can be used for obtaining the instantaneous optical frequency output by the sweep frequency light source and is used for nonlinear correction of the sweep frequency light source in the OFDR system. The optical signal output by the auxiliary interferometer is converted into an electrical signal by the PD4, and then the electrical signal is sent into the acquisition card to be processed by the computer; (3) And the measuring interferometer part is used for enabling the sweep frequency light source light waves output by the third coupler to enter the measuring interferometer through the other path after passing through the fourth coupler, and the measuring interferometer consists of a sixth coupler, a seventh coupler, a second circulator and the like. The second circulator reaches the seventh coupler to form a light path to be detected through the sixth coupler, and in the light path to be detected, light waves are output by the first port of the second circulator, and then are combined with detection light and pumping light in the photothermal spectrum system through the first coupler and the wavelength division multiplexer, and finally output to the FUT together. The optical signal output by the measuring interferometer is converted into an electric signal by the third detector, and then is sent into the acquisition card to be processed by the upper computer, and the upper computer can be a computer.
Fig. 2 shows a special arming design of FUT inside and outside the battery in order to monitor the internal gas concentration, internal and external temperatures, and external stress of the lithium battery simultaneously. FUT is divided into three parts, part 1 is a bare fiber plus loose tube, which can be fixed outside the lithium battery due to the isolation of the loose tube, which is only sensitive to temperature, as shown by the grey line segment in fig. 2 (a); part 2 is a bare fiber, sensitive to both temperature and strain, as shown by the black line segment in diagram (a) in fig. 2. The optical fibers of the 1 st part and the 2 nd part are fixed outside the battery side by side, so that the decoupling effect on temperature and strain can be realized. Part 3 is a cell internal measurement part, which is composed of a length of bare fiber and an optical fiber FP cavity at the end thereof, as shown in fig. 2 (b), where the length of bare fiber can be used for measurement of the cell internal temperature, and the optical fiber FP cavity is used for measurement of the cell internal gas concentration. Summarizing, the bare optical fiber or the sheath feeding part of the bare optical fiber utilizes the Rayleigh scattering effect in the optical fiber to acquire the temperature and strain information of each point inside and outside the battery through the OFDR system; the fiber FP cavity forms an air chamber and is connected in series with the tail end of the FUT, and specific gas concentration information in the battery is obtained through a photothermal spectrum system. In some cases, in order to increase the signal-to-noise ratio of the received light wave in the OFDR and improve the measurement accuracy of temperature and strain, fiber grating strings may be continuously etched on the FUT, and it should be noted that the reflection center wavelengths of the fiber gratings should be located in the wavelength range of the swept-frequency light source.
The method for calculating the collected data by the computer to obtain the gas concentration inside the battery, the internal and external temperature and the strain parameter of the battery is the prior art, and is not described herein.
The invention skillfully utilizes the characteristic of carrying out linear scanning on the pump light in the optical fiber photothermal spectrum gas detection system, and uses the pump light which is originally only used for gas absorption for carrying out temperature and strain sensing, thereby realizing the simultaneous measurement of gas concentration, temperature and strain, and being the key point of the invention. To achieve this objective, in an embodiment of the present invention, a fiber optic photothermal spectroscopy system is combined with an OFDR, with both systems sharing a swept source (also "pump laser") and a data processing system (i.e., the computer in fig. 1); the FP cavity for measuring the gas concentration is connected with the FUT in series, wherein the photo-thermal spectrum system for measuring the gas concentration usually uses 1550nm light waves for detection, the OFDR system uses a pump light system for detection, and the light wave ranges of the FP cavity and the FUT are not mutually interfered, so that simultaneous measurement of multiple physical quantities can be realized simultaneously; in order to realize the measurement of multiple physical quantities of the lithium battery, the invention designs a specific optical fiber arrangement mode, divides the optical fiber to be measured into three sections, and simultaneously realizes the measurement of the external strain of the battery, the internal and external temperature of the battery and the internal gas concentration of the battery. The bare optical fiber has the advantages of small diameter (250 mu m), corrosion resistance, electromagnetic interference resistance and the like, and meanwhile, the diameter of the FP cavity of the optical fiber manufactured by the bare optical fiber can be very small (2 mm), so that the bare optical fiber is very suitable for monitoring the internal physical quantity of a lithium battery. Meanwhile, the OFDR system can be used for forming distributed temperature and strain measurement, and multidimensional data are provided for monitoring the thermal effect of the lithium battery.
The three points are combined with each other, so that a multi-physical-quantity and multi-point monitoring scheme can be provided for lithium battery monitoring; meanwhile, the scheme is also expected to reduce the cost of fine monitoring of multiple physical quantities of the lithium battery.
The following points need to be described:
(1) The drawings of the embodiments of the present invention relate only to the structures related to the embodiments of the present invention, and other structures may refer to the general designs.
(2) In the drawings for describing embodiments of the present invention, the thickness of layers or regions is exaggerated or reduced for clarity, i.e., the drawings are not drawn to actual scale. It will be understood that when an element such as a layer, film, region or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element or intervening elements may be present.
(3) The embodiments of the invention and the features of the embodiments can be combined with each other to give new embodiments without conflict.
The present invention is not limited to the above embodiments, but the scope of the invention is defined by the claims.

Claims (9)

1. A lithium battery multi-physical measurement system, comprising:
the optical fiber to be measured is connected with the lithium battery to be measured;
the output end of the pumping laser is respectively connected with the optical amplifier and the fourth coupler through the third coupler;
the output end of the optical amplifier is connected with the intensity modulator;
the detection light path is used for emitting detection light and is respectively connected with the wavelength division multiplexer, the intensity modulator and the upper computer;
the output end of the intensity modulator is sequentially connected with an isolator, a first coupler and a wavelength division multiplexer, and the intensity modulator modulates the intensity of received light waves through a modulation signal output by the detection light path, wherein the isolator is used for unidirectionally transmitting the light waves output by the intensity modulator into the wavelength division multiplexer;
the output end of the fourth coupler is respectively connected with the measuring interferometer and the auxiliary interferometer;
the measuring interferometer transmits the received light waves to the wavelength division multiplexer through a first coupler, the measuring interferometer transmits the light waves transmitted back from the wavelength division multiplexer to a third detector, and the output end of the third detector is connected with the data acquisition card;
the output end of the auxiliary interferometer is connected with the fourth detector, and the output end of the fourth detector is connected with the data acquisition card;
the wavelength division multiplexer is used for combining the detection light wave emitted by the detection light path, the pump light wave modulated by the intensity modulator and the light wave emitted by the measurement interferometer, transmitting the combined light wave into the optical fiber to be measured for acting, and enabling the light wave acted in the optical fiber to be measured to be transmitted to the detection light path and the measurement interferometer in a branching way through the wavelength division multiplexer;
the data acquisition card is connected with the upper computer, and the upper computer outputs the internal gas concentration information of the lithium battery to be tested, the temperature of the lithium battery to be tested and the stress change of the lithium battery to be tested according to the received data.
2. The lithium battery multi-physical quantity measurement system according to claim 1, wherein the optical fiber to be measured includes: bare optical fiber, loose tube and FP cavity;
one end of the bare optical fiber is connected with the wavelength division multiplexer, the other end of the bare optical fiber is provided with the FP cavity, and the FP cavity is arranged in the lithium battery to be tested;
and one part of the bare optical fiber is directly spirally wound on the outer wall of the lithium battery to be tested, and the other part of the bare optical fiber is spirally wound on the outer wall of the lithium battery to be tested after being mounted on the loose tube.
3. The lithium battery multi-physical quantity measurement system according to claim 1, wherein the detection light path includes:
the detection laser is used for emitting laser and is respectively connected with the first circulator and the servo controller;
the first interface of the first circulator is connected with the detection laser, the second interface of the first circulator is connected with the wavelength division multiplexer, and the third interface of the first circulator is connected with the second coupler;
the second coupler divides the light wave signals output by the third interface of the first circulator into two paths, one path of light wave signals output by the third interface of the first circulator is transmitted to the first detector by the second coupler, and the other path of light wave signals output by the third interface of the first circulator is transmitted to the second detector by the second coupler;
the first detector converts the received light wave signals into electric signals and then transmits the electric signals to the servo controller;
the second detector converts the received light wave signal into an electric signal and then transmits the electric signal to the lock-in amplifier;
the phase-locked amplifier is respectively connected with the intensity modulator and the upper computer, and after the phase-locked amplifier demodulates the phase modulation generated by the gas photo-thermal effect in the lithium battery to be detected, the phase-locked amplifier transmits the modulation signal to the upper computer, and the upper computer processes the physique signal to obtain the concentration of the internal gas of the lithium battery to be detected.
4. The lithium battery multi-physical quantity measurement system according to claim 1, wherein the measurement interferometer comprises:
a sixth coupler, the sixth coupler transmitting the received optical wave component stream transmitted by the fourth coupler to a second circulator and an intrinsic optical path;
the first interface of the second circulator is connected with the sixth coupler, the second interface of the second circulator is connected with the first coupler through a sensing light path, and the third interface of the second circulator is connected with the seventh coupler;
the output end of the intrinsic optical path is connected with a seventh coupler;
and a seventh coupler connected with the third detector.
5. The lithium battery multi-physical quantity measurement system according to claim 1, wherein the auxiliary interferometer comprises:
a fifth coupler, which transmits the received light wave component stream transmitted by the fourth coupler into two Faraday rotary mirrors;
a delay optical fiber is arranged between one Faraday rotator mirror and the fifth coupler;
and the optical wave original paths processed by the two Faraday rotary mirrors return to the fifth coupler, and the fifth coupler transmits the optical wave processed by the Faraday rotary mirrors to the fourth detector.
6. The lithium battery multi-physical quantity measurement system according to claim 2, wherein the FP cavity diameter is less than 2mm.
7. The lithium battery multi-physical quantity measurement system according to claim 2, wherein the diameter of the bare optical fiber is less than 250 μm.
8. The lithium battery multi-physical quantity measurement system according to claim 1, wherein the third coupler has a spectral coefficient of 50%:50%.
9. The lithium battery multi-physical quantity measurement system according to claim 2, wherein the spectral coefficient of the fourth coupler is 1%:99%, wherein 1% of the light waves enter the auxiliary interferometer.
CN202311262207.1A 2023-09-27 2023-09-27 Lithium battery multi-physical-quantity measuring system Pending CN117387686A (en)

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