Electrochemical Device Monitoring

Abstract

A system is disclosed that includes an electrochemical device that generates a magnetic field and a sensing device that includes a magneto-optical medium, an electromagnetic radiation source configured to emit polarized electromagnetic radiation through the magneto-optical medium, and a sensor configured to receive the polarized electromagnetic radiation that has passed through the magneto-optical medium, the sensing device being positioned relative to the electrochemical device such that the magnetic field of the electrochemical device passes through the magneto-optical medium.

Description

[Technical field]

[0001] The present invention relates to the monitoring of electrochemical devices, and in particular, but not exclusively, to a system suitable for monitoring the properties of electrochemical devices utilizing the Faraday effect. Aspects of the invention relate to the system, monitoring methods, and various sensor configurations. [Background technology]

[0002] Current distribution measurements in electrochemical devices are crucial to the operation and durability of those devices. These measurements can result from manufacturing defects (e.g., inhomogeneous mixing or deposition of active materials) or concentration gradients at high current densities (e.g., flooding or oxygen starvation in fuel cells). Furthermore, some electrochemical devices used in various industries are moving towards higher power output and therefore require higher current densities.

[0003] Currently, power management systems monitor electrochemical devices such as fuel cells, batteries, or electrolysers by measuring individual cell voltages across hundreds of cells. The measured current (or reaction rate) is not uniformly distributed across the cells, especially at high current rates where small areas of the electrodes may operate at significantly higher current densities than other areas of the electrodes. Standard techniques are unable to detect these changes. Because the cells are assembled into stacks and modules, the failure of one of these cells can affect and disrupt adjacent cells and potentially the entire battery module or stack of cells. More importantly, if one of the cells begins to experience thermal runaway, this can propagate and cause catastrophic failure of the entire system. Despite rigorous quality control and inspection of each electrochemical cell (e.g., battery) in the assembly, catastrophic failures and battery fires still occur in electric vehicles starting from one failed battery.

[0004] It is possible to measure the current distribution within cells in an electrode array. This requires subdividing a cell into an array of small cells and recording the temperature change at various locations across the electrode array. When building a cell electrode from an array of smaller electrodes, the resolution is limited by the size of the unit cell. Furthermore, this method is complex and expensive. Furthermore, monitoring the current distribution in this way increases the possibility of leakage current and resistance within the electrode array, which can reduce the effectiveness of the electrodes. Also, the use of temperature changes has practical limitations, since batteries and cells are usually cooled to ensure a uniform temperature.

[0005] WO2021 / 019405A1 describes a sensing device that may chemically sample a battery by extracting the battery fluid. The extracted fluid is then analyzed using known spectroscopic methods to determine the health of the battery. This is further discussed in Gray, C. and Baumberg, J., "In-operando battery chemistry monitoring." [online], University of Cambridge Enterprise, [retrieved October 27, 2021], URL: https: / / www.enterprise.cam.ac.uk / opportunities / commercial-opportunity-in-operando-battery-chemistry-monitoring / . Thus, the method requires fluid extraction to perform battery health monitoring. It would be beneficial to provide a method for non-invasively determining the health of any electrochemical device, including non-fluidic batteries. Such a non-invasive method may be used in an operating system as a real-time monitoring of the health of the battery, but may also be used after battery manufacture for quality control verification prior to stack / module assembly. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 019405 [Non-patent literature]

[0007] [Non-Patent Document 1] Gray, C. and Baumberg, J., "In-operando battery chemistry monitoring.", [online], University of Cambridge Enterprise, [Retrieved October 27, 2021], <URL: https: / / www.enterprise.cam.ac.uk / opportunities / commercial-opportunity-in-operando-battery-chemistry-monitoring / > Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of some embodiments of the present invention to at least partially solve, mitigate, or avoid at least one of the problems or disadvantages associated with the prior art. Some embodiments aim to achieve at least one of the advantages set forth below. [Means for solving the problem]

[0009] Aspects of the present invention provide systems, methods and sensors as claimed in the accompanying claims.

[0010] According to one aspect of the invention, there is provided a system comprising an electrochemical device generating a magnetic field and a sensing device comprising a magneto-optical medium, an electromagnetic radiation source configured to emit polarized electromagnetic radiation through the magneto-optical medium, and a sensor configured to receive the polarized electromagnetic radiation that has passed through the magneto-optical medium, the sensing device being positioned relative to the electrochemical device such that the magnetic field of the electrochemical device passes through the magneto-optical medium.

[0011] The system may include a magneto-optical medium positioned such that a magnetic field of the electrochemical device interacts with the magneto-optical medium to rotate the plane of polarization of the polarized electromagnetic radiation based on a characteristic of the electrochemical device.

[0012] The system may include an electromagnetic radiation source positioned relative to the electrochemical device such that the emitted polarized electromagnetic radiation is parallel to the generated magnetic field of the electrochemical device.

[0013] The system may include a magneto-optical medium integral with the electromagnetic radiation source.

[0014] The system may include the aforementioned magneto-optical medium as a layer bonded to the electrochemical device.

[0015] The magneto-optic medium may comprise a thin film magneto-optic crystal.

[0016] The sensing device may further comprise a protective layer of insulating polymer or glass film to protect the thin film magneto-optic crystal. The magneto-optic crystal may be embedded in a polymer or glass fiber to protect the thin film magneto-optic crystal.

[0017] The magneto-optic crystal may have a high Verdet constant or low optical absorption.

[0018] The magneto-optical crystal may include at least one of barium hexaferrite, terbium gallium garnet, bismuth-substituted rare earth iron garnet, Na2Ce(MoO4)2, or CeAlO3.

[0019] The electrochemical device generating the magnetic field may be a battery comprising a plurality of cells, and the system may comprise a plurality of electromagnetic radiation sources each associated with one of the plurality of cells. The system may further comprise a plurality of magneto-optical media each associated with one of the plurality of cells.

[0020] The system may be configured to operate multiple electromagnetic radiation sources sequentially.

[0021] The sensor may be configured to receive polarized electromagnetic radiation from each of the electromagnetic radiation sources that has passed through one of the plurality of magneto-optical media.

[0022] The system may further include a plurality of sensors associated with the plurality of electromagnetic radiation sources.

[0023] The system may include a control module configured to determine a first plane of polarization of the emitted electromagnetic radiation or store a predetermined plane of polarization of the emitted electromagnetic radiation, determine a second plane of polarization of the electromagnetic radiation passed through the magneto-optical medium, determine a rotation angle between the first and second planes of polarization, determine a magnetic field strength of the electrochemical device based on the determined rotation angle, and determine a current distribution of the electrochemical device based on the determined magnetic field strength.

[0024] According to one aspect of the invention, there is provided a method of sensing comprising the steps of providing a system as described above, emitting polarized electromagnetic radiation from an electromagnetic radiation source through a magneto-optical medium, and receiving the polarized electromagnetic radiation that has passed through the magneto-optical medium with a sensor.

[0025] The method may further include determining an angle of rotation of the plane of polarization of the reflected electromagnetic radiation.

[0026] The method may further include determining a magnetic field strength of the electrochemical device based on the determined rotation angle, and determining a current distribution of the electrochemical device based on the determined magnetic field strength.

[0027] The method may further include repeating the step of determining the current distribution of the electrochemical device periodically or for multiple locations on the electrochemical device, and determining temporal or spatial changes in the current distribution information of the electrochemical device.

[0028] The step of emitting polarized electromagnetic radiation through a magneto-optical medium may include emitting the electromagnetic radiation from a plurality of fiber optic cables.

[0029] Electromagnetic radiation may be emitted individually from multiple fiber optic cables over a period of time so as to be incident on the magneto-optic medium in a pattern or sequentially.

[0030] Electromagnetic radiation may be emitted simultaneously from multiple fiber optic cables, and the multiple fiber optic cables may be configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

[0031] The system may include a control module configured to receive the change in current distribution information, and the control module may be configured to alter a parameter of the electrochemical device based on the change in current distribution information. The control module may be configured to activate an alarm based on the change in current distribution information.

[0032] According to one aspect of the invention, a sensing device is provided that includes a magneto-optical medium, an electromagnetic radiation source configured to emit polarized electromagnetic radiation through the magneto-optical medium, and a sensor configured to receive polarized electromagnetic radiation reflected from the electromagnetic radiation source through the magneto-optical medium, where the electromagnetic radiation source includes a first plurality of fiber optic cables or the sensor includes a second plurality of fiber optic cables.

[0033] The sensing device may further comprise at least one of a reflective layer or a protective medium.

[0034] The first plurality of fiber optic cables and the second plurality of fiber optic cables may be arranged in a mesh or woven array.

[0035] At least one of the first plurality of fiber optic cables or the second plurality of fiber optic cables may be configured to be embedded within the electrochemical device.

[0036] The first plurality of fiber optic cables may be configured to individually emit electromagnetic radiation over a period of time such that the electromagnetic radiation is incident on the magneto-optical medium in a pattern or sequentially.

[0037] Electromagnetic radiation may be emitted simultaneously from a first plurality of fiber optic cables, the first plurality of fiber optic cables being configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

[0038] According to one aspect of the invention, there is provided a sensing device comprising an electromagnetic radiation source comprising a first plurality of fiber optic cables for emitting polarized electromagnetic radiation, and a sensor configured to receive the polarized electromagnetic radiation, the sensor comprising a magneto-optical medium through which the polarized electromagnetic radiation from the electromagnetic radiation source passes.

[0039] The sensor may include a second plurality of fiber optic cables, which may include a magneto-optic medium.

[0040] At least one of the fiber optic cables may include a reflective layer.

[0041] The first plurality of fiber optic cables may be configured to individually emit electromagnetic radiation over a period of time.

[0042] The electromagnetic radiation may be emitted simultaneously from a first plurality of fiber optic cables, and the first plurality of fiber optic cables may be configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

[0043] According to one aspect of the present invention, there is provided the use of a sensing device for determining a change in current in an electrochemical device.

[0044] Examples of the invention will now be further described with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 is a schematic diagram of an example system for monitoring an electrochemical device. [Diagram 2] FIG. 2 is a schematic diagram of another example system for monitoring an electrochemical device. [Diagram 3] FIG. 1 is a schematic diagram of an example of an optical fiber array. [Figure 4] FIG. 2 is a schematic diagram of another example system for monitoring an electrochemical device using optical fibers. [Diagram 5] FIG. 2 is a schematic diagram of another example system for monitoring an electrochemical device using optical fibers. [Figure 6] FIG. 2 is a schematic diagram of yet another example system for monitoring an electrochemical device using optical fibers. [Figure 7]FIG. 1 illustrates an example method for monitoring an electrochemical device. [Figure 8] FIG. 8 illustrates the method of FIG. 7 further including determining a rotation angle. [Figure 9] FIG. 9 illustrates the method of FIG. 8 further including determining the current distribution of the electrochemical device. [Figure 10A] FIG. 13 shows example results of current non-uniformity in a 2000 mAh lithium pouch cell. [Figure 10B] FIG. 13 shows example results of current non-uniformity in a 4000 mAh lithium pouch cell. [Figure 11A] FIG. 10 shows an example of a magnetic field map determined using the methodology of FIG. [Figure 11B] FIG. 13 shows the time course of magnetic field mapping during the first discharge cycle of a 20.5 mm×15.5 mm small section of a 4000 mAh lithium-ion battery at a discharge rate of 2C (8 A) or equivalently 99.7, 91.7, 83.3, and 77.8% state of charge after 10, 300, 600, and 800 seconds. [Figure 11C] FIG. 13 shows the time course of magnetic field mapping of a 20.5 mm×15.5 mm small section of a 4000 mAh lithium-ion battery at a discharge rate of 2C (8 A) after 10, 300, 600, and 800 seconds during the 40th discharge cycle. [Figure 11D] FIG. 13 shows a comparison of magnetic field maps for the 1st and 40th discharge cycles of a 20.5 mm×15.5 mm small section of a 4000 mAh lithium-ion battery at an 8 A discharge rate after 60, 120, and 180 seconds. [Figure 12] FIG. 14 shows a comparison of the 1st and 40th discharge cycles of a 4000mAh Li-ion battery at 8A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Like numbers indicate like functions.

[0047] It will be appreciated that examples of the present invention may be realized in the form of hardware, software, or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage, such as a storage device, e.g., a ROM, whether erasable or rewritable, or in the form of memory, e.g., a RAM, memory chip, device, or integrated circuit, or on an optically or magnetically readable medium, e.g., a CD, DVD, magnetic disk, or magnetic tape. It will be appreciated that the storage devices and storage media are examples of machine-readable storage suitable for storing one or more programs that include instructions that, when executed, implement examples of the present invention.

[0048] Thus, some examples provide a program including code for implementing an apparatus or method as claimed in any one of the claims herein, and a machine-readable storage device for storing such a program. Further, such a program may be transmitted electronically via any medium, such as, for example, a communication signal transmitted over a wired or wireless connection, and some examples encompass these, as appropriate.

[0049] Throughout this specification, reference is made to electrochemical devices, which are intended to encompass any device that can generate electricity from a chemical reaction or utilize electrical energy to drive a chemical reaction, including, but not limited to, batteries and their cells, electrolyzers, sensors, fuel cells, water electrolyzers, and the like.

[0050] The present invention utilizes the Faraday effect (or Faraday rotation) to map the current distribution in an electrochemical device. An electrochemical device has a magnetic field in a plane perpendicular to the direction of current flow. When polarized electromagnetic radiation passes through a material, the plane of polarization is rotated by an angle proportional to the magnetic field strength. The relationship between the angle of rotation of the polarized light and the magnetic field within the material is expressed by Becquerel's formula: Equation 1 β=VBd where β is the angle of rotation (radians), B is the magnetic flux density (tesla) in the direction of propagation, d is the path length (meters) over which the electromagnetic radiation and the magnetic field interact, and V is the Verdet constant of the material. This empirical proportionality constant (units: radians / tesla / meter) varies with wavelength and temperature and is tabulated for various materials. A positive Verdet constant corresponds to an L rotation (counterclockwise direction) when the direction of propagation is parallel to the magnetic field, and an R rotation (clockwise direction) when the direction of propagation is antiparallel. Thus, when a ray of electromagnetic radiation passes through a material and is reflected back through it, the rotation is doubled.

[0051] Materials with a high Verdet constant (positive or negative) result in a large angle of rotation. The Verdet constant has a positive value for diamagnetic materials and a negative value for paramagnetic materials. Absolute values ​​are used throughout this specification. Examples of materials with high Verdet constants include barium hexaferrite, terbium gallium garnet, and bismuth-substituted rare earth iron garnet. For example, the Verdet constant of terbium gallium garnet (TGG) is approximately -134 rad / (T*m) for 632 nm electromagnetic radiation. The Verdet constant of CeAlO3 is 270 rad / (T*m) for 632 nm electromagnetic radiation, and the Verdet constant of NaCe(MoO4)2 is 204 rad / (T*m) for 632 nm electromagnetic radiation. For ferromagnetic or ferrimagnetic materials with internal magnetization, the total Faraday rotation of a light wave traveling through such a material over a distance l is given by the following equation:

[0052]

number

[0053] M 0z is the existing magnetization in the material, and M s is the saturation magnetization of the material.

[0054] The Faraday rotation is determined by the surrounding magnetic field that magnetizes the magneto-optic layer, and is maximum when the material is magnetized to its saturation magnetization.

[0055] Absolute value of Faraday specific rotation P F is 216° / cm for yttrium iron garnet at 1550 nm electromagnetic radiation, and y Bi x Y 3-x- yFeO 12 The absolute value of the Faraday specific rotation P F is 6500° / cm for (Bi,Y,Gd,Tm,Lu,Ca)3(Fe,Si)5O12 at 725 nm, 5000° / cm for (YYbBi)3Fe5O12 at 800 nm, and 20,000° / cm for bismuth yttrium iron garnet at 590 nm. Bismuth yttrium iron garnet has a spectral density of 2.7 dBcm at 1550 nm. -1 It has the lowest absorption coefficient of .

[0056] 1 and 2 show schematic examples of systems 100, 200 for monitoring current distribution in an electrochemical device using the Faraday effect. The direction of the current is indicated by arrow 112 and the corresponding magnetic field direction is indicated by arrow 114. The system includes an electromagnetic radiation source 120, a sensor 122, 222, and a magneto-optical medium 130.

[0057] The electromagnetic radiation source 120 is configured to transmit polarized electromagnetic radiation 124 through the magneto-optical medium 130. In other words, the electromagnetic radiation source 120 emits polarized electromagnetic radiation 124 toward the magneto-optical medium 130. In the example shown in FIG. 1, the electromagnetic radiation passes through the magneto-optical medium 130 and is reflected back through the magneto-optical medium to the sensor 122. Thus, the system 100 may include a reflective layer 132, and in some examples the electrochemical device 110 may be reflective, or the reflective layer 132 and the electrochemical device 110 may be integral. The reflective layer 132 may be formed from any reflective material, such as aluminum, for example.

[0058] The electromagnetic radiation 124 may be emitted from the electromagnetic radiation source 120 in a direction parallel to the direction of the magnetic field 114 generated by the electrochemical device 110. The electromagnetic radiation 124 may be polarized as it is generated. In some examples, the electromagnetic radiation source 120 may include a polarizing filter (not shown) for polarizing the electromagnetic radiation 124. The electromagnetic radiation 124 may be linearly polarized.

[0059] Polarized electromagnetic radiation 124 passes through the magneto-optical medium 130 and its plane of polarization is rotated by the Faraday effect as described above. Local changes in the current 112 of the electrochemical device 110 result in proportional changes in the magnetic field 114. These changes in the magnetic field therefore have an effect on the angle of rotation of the plane of polarization of the electromagnetic radiation passing through the magneto-optical medium 130.

[0060] In the example system 100 shown in Figure 1, electromagnetic radiation 124 is reflected to the sensor 122, which receives the reflected electromagnetic radiation that has passed through the magneto-optical medium 130, and therefore has its plane of polarization rotated. The sensor 122 or a control system (not shown) can then determine a characteristic of the electrochemical device based on the received electromagnetic radiation 126 that has passed through the magneto-optical medium 130, as will be described in more detail below with reference to the methodology described in Figures 7-9.

[0061] The system 100 may include a reflective layer 132. In some examples, the magneto-optical medium 130 may include the reflective layer 132, or a reflective surface may be otherwise applied to the electrochemical device 110. In some examples, the electrochemical device 110 may be reflective, such that the reflective layer 132 may not be required.

[0062] Figure 2 illustrates an example system 200 having an alternative layout to that of Figure 1. In this example, the system 200 has a sensor 222 positioned between the magneto-optical medium 130 and the electrochemical device 110. In this example, the electromagnetic radiation 124 travels through the magneto-optical medium to the sensor 222; that is, in the system illustrated in Figure 2, the electromagnetic radiation 124 is not reflected.

[0063] 1 and 2, the magneto-optical medium 130 is positioned such that the magnetic field 114 of the electrochemical device 110 can interact with the magneto-optical medium 130 to rotate the plane of polarization of the polarized electromagnetic radiation 124. For example, the distance between the magneto-optical medium and the electrochemical device 110 may be between 0.1 μm and 1000 μm. Suitably, the distance may be between 1 μm and 750 μm, and more suitably between 5 μm and 500 μm.

[0064] In some examples, the magneto-optical medium 130 may be coupled to the electrochemical device 110. For example, the magneto-optical medium 130 can be a layer adhered to a surface of the electrochemical device 110 or the reflective layer 132. In other examples, the magneto-optical medium 130 may be integral with the electrochemical device. In this example, the polarized electromagnetic radiation 124 passes through a portion of the electrochemical device 110 that functions as the magneto-optical medium 130 and is then received by the sensor 122.

[0065] Electromagnetic radiation source 120 may be any device capable of emitting polarized electromagnetic radiation. In some examples, electromagnetic radiation source 120 may be a fiber optic cable that transmits electromagnetic radiation 124 from an external source. In some examples, these fiber optic cables may be equipped with polarizing filters.

[0066] The sensor 122 may be any device capable of receiving polarized electromagnetic radiation and obtaining therefrom a characteristic of the magnetic field 114. For example, the sensor 122 may be a camera device. In another example, the sensor 122 may be a transmission device that captures data, such as the polarized electromagnetic radiation 126 that has passed through the magneto-optical medium 130, and transmits it to a control device (not shown), such as a fiber optic cable.

[0067] The sensor 122 may be capable of determining a characteristic of the electrochemical device 110, for example the sensor 122 may be capable of implementing the methods described hereinafter to determine the current distribution across the electrochemical device 110. To this end, the sensor 122 may include an integrated control device that may obtain magnetic field data based on the received polarized electromagnetic radiation 126.

[0068] The magneto-optical medium 130 is a medium through which electromagnetic radiation can propagate. For example, the magneto-optical medium 130 may be a transparent material. In some examples, the magneto-optical medium 130 may be a layer bonded to an electrochemical device. In other examples, the magneto-optical medium 130 may be part of a core of a fiber optic cable. The magneto-optical medium 130 may have a thickness between 0.01 μm and 750 μm. Suitably, the magneto-optical medium 130 may be between 0.1 μm and 500 μm thick, and more suitably between 0.6 μm and 10 μm thick.

[0069] In some examples, the magneto-optical medium 130 may comprise thin-film magneto-optical crystals. The magneto-optical crystals may be embedded in a transparent material, such as a polymer or fiberglass. These thin-film magneto-optical crystals may be crystals with a high Verdet constant. In examples where the magneto-optical medium 130 is a ferromagnetic or ferrimagnetic material, the magneto-optical medium 130 may have a high specific rotation and a low optical absorption coefficient, or a high figure of merit ratio of the former to the latter, greater than 10. In some examples, the magneto-optical crystals include at least one of barium hexaferrite, terbium gallium garnet, and bismuth-substituted rare earth iron garnet. Further alternative materials include Na2Ce(MoO4)2 or CeAlO3. Iron garnet materials can be used because they have high sensitivity compared to other known materials.

[0070] In some examples, the systems 100, 200 may further include one or more protective layers 134 as shown in FIG. 1. This protective layer 134 may be configured to cover the magneto-optical medium 130 to provide additional protection. Thus, the protective layer 134 may be transparent to the electromagnetic radiation 124. In some examples, the protective layer 134 may have a low Verdet constant such that rotation of the plane of polarization of the electromagnetic radiation 124 within the protective layer 134 is negligibly low.

[0071] The protective layer 134 may be an insulating polymer or glass film. In the example where the magneto-optical medium includes magneto-optical crystals, the magneto-optical crystals may be embedded in a polymer or glass fiber. In other words, the protective layer 134 may be integral with the magneto-optical medium 130.

[0072] The electromagnetic radiation source 120 may emit radiation at a predetermined wavelength. The wavelength of the radiation may be determined depending on the magneto-optical medium 130 used. Suitably, the electromagnetic radiation 124 may be within the visible spectrum. Examples of suitable wavelengths include, but are not limited to, 400 nm to 800 nm, suitably 500 nm to 700 nm, and more suitably 550 nm to 600 nm. For example, an electromagnetic wavelength of 590 nm may be used.

[0073] Further, in some examples, the electrochemical device 110 may be a battery with multiple cells. Each of the multiple cells may have an associated electromagnetic radiation source 120 and magneto-optical medium 130. In this manner, the system 100, 200 may include multiple electromagnetic radiation sources 120, each associated with one of the multiple cells and multiple magneto-optical media, each of the multiple magneto-optical media associated with one of the multiple cells. In these examples, a single sensor 122 may be capable of receiving electromagnetic radiation 124 from each electromagnetic radiation source 120 that has passed through one of the multiple magneto-optical media 130. Alternatively, each of the multiple cells may have an associated sensor 122. The system 100, 200 may sequentially operate the multiple electromagnetic radiation sources 120 such that each cell is individually monitored to build an image of the current distribution through the battery. Similarly, the systems 100, 200 may comprise multiple cells with associated sensors 122 and magneto-optical media 130, and a single electromagnetic radiation source. These configurations allow mapping of different cells in a very short period of time.

[0074] In some examples, one or both of the electromagnetic radiation source 320 or the sensor 322 may be a plurality of fiber optic cables 340, 342. An example of the configuration of the fiber optic cables 340, 342 is shown in FIG. 3. In this example, the electromagnetic radiation source 320 is a first plurality of fiber optic cables 340 and the sensor 322 is a second plurality of fiber optic cables 342. For example, the first plurality of fiber optic cables 340 may be configured to connect to an external electromagnetic radiation source and transmit polarized electromagnetic radiation to the system. Similarly, the second plurality of fiber optic cables 342 may be configured to transmit polarized electromagnetic radiation that has passed through the magneto-optic medium 330 to an external sensor.

[0075] The first and second plurality of fiber optic cables 340, 342 may be arranged in a mesh or woven array. The fiber optic cables 340, 342 may be positioned adjacent to the magneto-optical medium 330 and the electrochemical device 310.

[0076] The fiber optic cables 340, 342 may be arranged such that the magneto-optical medium 330 is sandwiched between the electromagnetic radiation source 320 (first plurality of fiber optic cables 340) and the sensor 322 (second plurality of fiber optic cables 342). Alternatively, the electromagnetic radiation source 320 (first plurality of fiber optic cables 340) and the sensor 322 (second plurality of fiber optic cables 342) may be an interwoven mesh array or a woven array. In some examples, one or both of the first plurality of fiber optic cables 340 or the second plurality of fiber optic cables 342 can be embedded inside the electrochemical device 310.

[0077] In some examples, the fiber optic cables 340, 342 may be partially or completely coated with a reflective layer, which is effective to minimize electromagnetic radiation loss to the environment, thereby ensuring that most of the captured electromagnetic radiation travels back along the optical fiber to an external sensor.

[0078] In yet another example configuration, the magneto-optical medium 330 may comprise a magneto-optical crystal. In this example, the fiber optic cables 340, 342 and the magneto-optical crystal may be embedded in an electrochemical cell separator or solid electrolyte. The magneto-optical medium 330 may also be contained within the fiber optic cable of the sensor 322 (see Figures 5 and 6).

[0079] In the example where the electromagnetic radiation source 320 is a plurality of fiber optic cables 340, the magneto-optical medium 330 (and the electrochemical device 310) may be sequentially illuminated. For example, the electromagnetic radiation source 320 may be a plurality of optical fibers 340a-340h. The sensor 322 may be a plurality of optical fibers 342a-342f arranged perpendicular to the plurality of optical fibers 340a-340h forming the electromagnetic radiation source 320. These optical fiber cables 340a-340h, 342a-342f cover the magneto-optical medium 330. The electromagnetic radiation source 320 may then emit electromagnetic radiation from the first fiber optic cable 340a, then from the second fiber optic cable 340b, and so on. In this way, portions of the magneto-optical medium 330 are sequentially illuminated across the entire surface. The sensor 322 then receives the electromagnetic radiation and the current distribution on the electrochemical device may be mapped.

[0080] This sequential illumination may be in any order, for example multiple cables may illuminate simultaneously or only a single cable may illuminate. A controller (not shown) may be provided with the system that can control the illumination order.

[0081] In another example, the magneto-optical medium 330 (and electrochemical device 310) may be illuminated by fiber optic cables 340a-340h, where one or more of the fiber optic cables 340a-340h are configured to emit electromagnetic radiation at different wavelengths. For example, the electromagnetic radiation source 320 may emit electromagnetic radiation at one wavelength from a first fiber optic cable 340a and at the same time emit electromagnetic radiation at a different wavelength from a second fiber optic cable 340b. These different wavelengths may thus enable improved positional mapping of the current distribution.

[0082] In some examples, groups of fiber optic cables 340a-340h may be sequentially illuminated, each with a different wavelength. For example, five adjacent fiber optic cables 340a-340h may be simultaneously illuminated, each with a different wavelength, then illumination may be stopped, and then the next five may be illuminated, again with different wavelengths, etc.

[0083] The plurality of optical fiber cables 340, 342 may have a diameter of 1 μm to 100 μm, suitably 3 μm to 75 μm, more suitably 5 μm to 50 μm. The plurality of optical fiber cables 340, 342 may be arranged such that 1 to 10,000 optical fiber cables 340, 342 are included in a surface area of ​​1 cm of the magneto-optical medium, suitably 10 to 1000 optical fiber cables 340, 342 are included in a surface area of ​​1 cm of the magneto-optical medium. For example, if an optical resolution of 10 μm is required, 1000 fibers having a diameter of 10 μm are arranged in a surface area of ​​1 cm of the magneto-optical medium.

[0084] By using fiber optic cables for either or both of the electromagnetic radiation source 320 or the sensor 322, it is possible to construct a detailed map of the magnetic field, and therefore the current distribution, of the electrochemical device 310. Furthermore, in instances where the system is comprised of multiple electrochemical devices 310, such as battery cells or electrolyzer stacks, the use of fiber optic cables allows the installation of the monitoring system without significantly increasing the overall size of the device.

[0085] 4-6, there are shown schematic diagrams of exemplary configurations of fiber optic cable-equipped systems 400, 500, 600. The figures depict a single fiber optic cable 442, 542, 642 for clarity, however, it should be understood that multiple fiber optic cables may be used for each illustrated embodiment.

[0086] In the example shown in Fig. 4, the system 400 comprises an electromagnetic radiation source 420, which may be an electromagnetic radiation source or a fiber optic cable array as described above. The electromagnetic radiation source 420 is configured to emit polarized electromagnetic radiation 424 towards a magneto-optical medium 430. In this case, the magneto-optical medium 430 is adjacent to an electrochemical device 410, which has a current 412 flowing across the device 410, thus generating a perpendicular magnetic field 414. In the example of Fig. 4, the magneto-optical medium 430 is coupled to the electrochemical device 410. A reflective layer 432 is sandwiched between the magneto-optical medium 430 and the electrochemical device 410. The reflective layer 432 reflects the polarized electromagnetic radiation 424 back through the magneto-optical medium 430, such that the polarized electromagnetic radiation 424 passes through the magneto-optical medium 430 twice. The reflected polarized electromagnetic radiation 426 is received by a sensor 422, which is a fiber optic cable 442.

[0087] In the example shown in Figure 5, the system 500 comprises a similar configuration to that of Figure 4. However, in this example, the sensor 422 is a fiber optic cable 542 comprising a magneto-optical medium 530. In this example, the electromagnetic radiation source 420 emits polarized electromagnetic radiation 424 to a reflective layer 432 coupled to the electrochemical device 410. The reflected polarized electromagnetic radiation 426 passes through the magneto-optical medium 530 in the fiber optic cable 542. That is, the polarized electromagnetic radiation 424 passes through the magneto-optical medium 530 only once (after reflection).

[0088] In the example shown in Figure 6, the sensor 422 is a fiber optic cable 642 that includes a magneto-optical medium 630, as in Figure 5. Additionally, the fiber optic cable 642 includes a reflective layer 632 that may partially cover the fiber optic cable 642. In this example, the electromagnetic radiation source 420 emits polarized electromagnetic radiation 424 toward the reflective layer 432, which partially covers the fiber optic cable 642.

[0089] The reflected polarized electromagnetic radiation 426 passes through the magneto-optical medium 630 in the fiber optic cable 642. In this manner, the fiber optic cable 642 need only be located in the vicinity of the electrochemical device 410. That is, the fiber optic cable 642 must be positioned close enough to the electrochemical device 410 such that the magneto-optical medium 630 interacts with the magnetic field 414 such that the plane of polarization of the polarized electromagnetic radiation 424 may be rotated. A reflective layer 432 may be positioned above the magneto-optical medium 630. In this manner, the electromagnetic radiation passes through the magneto-optical medium 630 twice, once as an incident beam and a second time as a reflected beam.

[0090] The reflective layer 432 may be provided on the fiber optic cable 642 by coating the outer portion of the fiber with a reflective coating. This improves the efficiency of returning electromagnetic radiation to the sensor 422 and reduces the amount of electromagnetic radiation radiated elsewhere. In other words, the section of the fiber optic cable 642 facing the electrochemical device 410 does not have a reflective coating, and the section facing away from the electrochemical device 410 has the reflective layer 432.

[0091] Referring to FIG. 7, an example method utilizing the above-described system is shown. A first step S750 includes emitting polarized electromagnetic radiation from an electromagnetic radiation source through a magneto-optical medium. The magneto-optical medium is positioned relative to an electrochemical device through which a current is flowing such that the magnetic field generated by the current interacts with the magneto-optical medium. The magneto-optical medium causes the plane of polarization of the electromagnetic radiation to be rotated by the Faraday effect. This rotation is proportional to the magnetic field strength of the electrochemical device. Then, in step S752, a sensor receives the polarized electromagnetic radiation that has passed through the magneto-optical medium (and thus been rotated). The amount of rotation of the polarized electromagnetic radiation will change in response to changes in the current distribution across the electrochemical device. This method can be performed simultaneously at multiple locations on the electrochemical device, and in some cases the method may be repeated at multiple locations on the electrochemical device.

[0092] Then, as shown in FIG. 8, in step S754, the angle of rotation of the plane of polarization of the electromagnetic radiation may be determined. The angle of rotation of the plane of polarization may be determined by comparing the plane of polarization of the received electromagnetic radiation to the known plane of polarization emitted. The angle of rotation may also depend on the number of times the electromagnetic radiation passes through a magneto-optical medium. For example, in a system that utilizes reflection to a sensor, the magneto-optical medium may rotate the plane of polarization by a factor of two. Thus, the calculation of the angle of rotation will vary depending on the configuration of the system. In some examples, the system may include a controller to perform these calculations.

[0093] Thus, as shown in FIG. 9, in step S756, the strength of the magnetic field may be determined based on the angle of rotation of the plane of polarization. This magnetic field may be determined using Becquerel's law. Thus, the change in the magnetic field will be indicated by the difference in the angle of rotation. This allows for a system with a sensitivity of 0mT to 10mT, suitably with a sensitivity of 0mT to 5mT, and most suitably with a sensitivity of 0mT to 2.5mT. This change in the magnetic field may be mapped positionally across the electrochemical device. Advantageously, this allows for the generation of a magnetic flux density map of the electrochemical device as shown in FIGS. 10A-11D.

[0094] Then, in step S758, the corresponding local current in the mapped area can be calculated based on the determined magnetic field strength. This can then be converted into a current density distribution map. This conversion can be performed by scaling the magnetic flux density map by the ratio of the discharge (or charge) current to the recorded average magnetic field flux of the entire battery. In the example of Figures 11B and 11C, this is 40 times (4A / 0.1mT). The average magnetic flux density in this example can be obtained by analyzing a small section of the battery (using conventional methods) rather than the entire battery.

[0095] Alternatively, a more accurate conversion would be about 10% air / aluminum. -6 This can be achieved by converting the magnetic flux density to magnetic field strength using the material permeability in H / m. A magnetic flux density of 0.1 mT can be converted to 100 A / m. If the distance from the magneto-optical layer of the sensor to the battery electrode is found to be, for example, 220 μm, then an equivalent current of 22 mA can be said to be flowing into the electrode current collector in the mapping area where the magnetic flux density is detected. The current density can be calculated by dividing the current by the area where it is detected.

[0096] These current distribution maps can be generated over time, for example, Figures 11A and 11B show four current distribution maps at different time periods. Figure 11A shows the electrochemical device at the 1st discharge and Figure 11B shows the electrochemical device at the 40th discharge. As can be seen from these figures, the current distribution map changes as the battery ages and cycles progress. This shows a direct correlation between the non-uniformity of current density and the aging of the electrochemical device by comparing the highest data from the 1st cycle with the lowest data after the 40th cycle. This allows for the identification of current hotspots 1160, for example, as shown in Figure 11D. Hotspots 1160 may be considered as areas with very high local magnetic flux compared to the surroundings, for example, above 30% of the average value. Hotspot formation and dendrite formation indicate a thermal runaway risk, especially if detected continuously in the same area over a long period of time. These formations may also indicate defects in the battery manufacturing and can be used for quality control evaluation.

[0097] Thus, by monitoring this change in current density, it is possible to assess quality control of device manufacturing, detect aging, estimate useful life, predict failure modes, or take corrective action via system control. For example, this method can detect fuel cell flooding or battery aging if there is a direct correlation between local current density changes and battery aging. Furthermore, this method can highlight areas of very high or low current density that may correlate with impending failure. This information can be fed back to a control system, which can take mitigating action or trigger a service alarm, for example, for low battery charge or discharge rates. This information can also be used to locate failed cells from a large pack of cells and also locate areas within the cell itself, or for quality control assessment of batteries after manufacturing.

[0098] Working Example Two Li-ion pouch and prismatic cells were tested. Cells with capacities of 2000 mAh and 4000 mAh were tested. The 2000 mAh cell had external dimensions of 40 × 55 × 5.8 mm (height, width, thickness) and the total area of ​​the electrodes was 440 cm. 2 (80 × 5.5 cm, wrapped). As shown in Figure 10A, the magnetic flux density map could be detected from 2C (4A). This was 4 / 440 = 90 mA cm -2 Similarly, for the 4000mAh battery in FIG. 10B, the magnetic field mapping shows that the magnetic field increases from a current of 4A or more, i.e., a discharge rate of 1C or 4 / 870=46mAcm -2 The cell had dimensions of 50 × 100 × 5 mm (height, width, thickness) and the total area of ​​the electrodes was 870 cm. 2 (87 x 100 cm, wrapped).

[0099] The thickness of the external insulator of the prismatic cell was 220 μm. Anode active layers of graphene with a total thickness of 70 μm were separated on either side by 50 μm of copper foil. Cathode active layers of nickel-manganese-cobalt oxide layers with a total thickness of 45 μm were coated on either side by 25 μm of aluminum foil. The battery was charged and discharged at a rate of 1-4C.

[0100] A portion of a 4000 mAh battery was placed flat on the 20.5 mm x 15.5 mm sensor, which consists of a glass substrate coated with a thin magneto-optical coating (a 1-10 μm layer of bismuth-substituted rare earth iron garnet single crystal film with a Faraday specific rotation of PF>1° / μm (i.e., 10,000° / cm at 590 nm electromagnetic radiation) topped by a 5 μm aluminum reflective layer with a protective polymer surface). The substituted iron garnet film has the highest magnetic resolution of any magneto-optical material used as a visualization device, with magnetic fields down to 10 A / m or magnetic fluxes of 0.01 mT being detectable (MR Koblischka and RJ Wijngaarden, "Magneto-optical investigations of superconductors", Supercond. Sci. Technol., 8:199, 1995). The saturation range of the sensor is approximately 10 A / m with an operating range of 0.05-2.0 mT. -6 Considering a magnetic permeability of 1000 H / m (for air, copper, and aluminum), this was close to a magnetic flux density of 2 mT or a magnetic field strength of 2 kA / m.

[0101] The Faraday rotation when using polarized light with a wavelength of 590 nm corresponds to 1.5° / mT for one pass of the reflected light through the sensor at room temperature, or 3° / mT for two passes (effectively twice the travel distance or layer thickness). If the magnetic flux density at the lower limit of detection of the sensor used is 0.05 mT, a rotation of the polarized light of 0.15° will be detected. Polarized light with a wavelength of 590 nm was incident on the back surface of the glass substrate, i.e. the surface opposite to the surface on which the battery is located. This light passes through the glass and the magneto-optical layer, and is then reflected by the aluminum mirror layer to pass twice through the magneto-optical layer and the glass with different rotation angles depending on the local magnetic flux density. This reflected light then passes through an analyzer-polarizing filter module and then to a 5MP CCD camera to generate an intensity contrast image that displays the magnetic field distribution map of the battery with an optical resolution of 25 μm. The evolution of the magnetic flux density map with time and charge-discharge cycles (1 and 40) can be seen in Figures 11B and 11C. It can be seen that despite the moderate current density and charging rate of 2C, good detection of the magnetic flux density map could be obtained, reflecting the large changes in the current distribution at the battery electrodes.

[0102] For electric vehicles, much higher charging rates of 4-10C with fast charging are desirable. The map can be analyzed to identify areas of low flux density over time (less than 20% of the average) and areas of high flux density over time (more than 20% of the average). The analysis also shows the non-uniformity of the discharge or charge of the electrode in a given cycle, i.e. how the most active areas over time during the cycle start discharging (or charging) first and move over time to the less active areas first as the battery voltage drops (or rises). If small areas with very high local flux (more than 50% of the average) are continuously detected in the same area for an extended period of time, this may indicate hotspot formation and dendrite formation with associated thermal runaway risk. For example, in FIG. 11D, an area of ​​hotspot 1160 is detected at 60 seconds (40th discharge). This high activity was not detected earlier, at 10 seconds (FIG. 11C) or later, at 120 seconds (FIG. 11D), and is therefore not considered a risk for dendrite formation as anticipated here given that the battery is in the beginning of discharge state.

[0103] On the other hand, if hot spots are detected over a long period of time, over 100 seconds towards the end of the charging cycle, this may be a continuous indication of dendrite formation or impending major battery failure. Various analyses can be performed on the captured map / data, such as the minimum / maximum and average values ​​of magnetic flux density in the map. This can be done by selecting a particular area or line in the x-axis or y-axis. An example of a simple analysis is shown by selecting a line located midway in the y-axis, which shows the change in magnetic flux density in the x-axis direction. From the simple analysis shown in Figures 11C and 11D, it is clear that the standard deviation of the magnetic field flux density increases with the aging of the battery. More complex analyses of the entire mapping area would be even more useful. For example, from Figures 11B-11D, it is clear that aging leads to a non-uniform magnetic field distribution across the electrode, with a higher density towards the top and upper left side of the monitored area of ​​the electrode. In FIG. 12, it can be clearly seen that a significant capacity loss occurs between the 1st and 40th cycles from 3400mAh to 2200mAh at a discharge rate of 8A.

[0104] Although multiple system configurations have been described herein, any configuration capable of utilizing the Faraday effect to measure current distribution in an electrochemical device is contemplated as falling within the scope of the claims. Additionally, features described in connection with only a single example may be included in other examples unless otherwise specified.

[0105] Throughout the figures, current is shown flowing from left to right resulting in an upward magnetic field (as viewed on the page), however, it should be understood that the direction of this current can be in any direction and therefore the resulting magnetic field can be in any vertical direction.

[0106] The sensors described above may be retrofitted to the electrochemical device or may be provided separately for use with the electrochemical device.

[0107] Advantageously, the above-described systems, sensors, and methods provide improved monitoring methods that are non-invasive to electrochemical devices, and are capable of detecting changes in the electrochemical device, thus revealing problems that may otherwise remain undetected even when the electrochemical device has inhomogeneities.

[0108] Throughout this specification, the words "comprise" and "include" and variations thereof mean "including but not limited to" and are not intended to (and do not) exclude other elements, wholes, or steps. Throughout this specification, the singular includes the plural unless otherwise required by the context. In particular, when the indefinite article is used, the specification should be understood to contemplate the singular as well as the plural unless otherwise required by the context. Throughout this specification, the word "about" is used to provide flexibility to the endpoints of the range by indicating that a given numerical value may be "slightly above" or "slightly below" the endpoint. The flexibility of this term can be determined by its particular variables and can be determined based on experience and the relevant explanations in this specification.

[0109] It is to be understood that a feature, whole or characteristic described in combination with a particular embodiment or example of the invention is applicable to any other embodiment or example described herein, unless inconsistent. All features disclosed herein and / or all steps of any method or process disclosed herein may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the preceding examples. The invention extends to any novel feature or combination of features disclosed herein. It is also to be understood that throughout this specification, expressions of the general form "X for Y" (where Y is some act, activity, or step, and X is some means for performing such act, activity, or step) specifically but not exclusively encompass means X adapted or configured to perform Y.

[0110] Each feature disclosed in this specification, unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only one example in a generic series of equivalent or similar features.

[0111] The reader's attention is directed to all articles and documents related to this application that have been filed contemporaneously or prior to this application and that have been published herewith, the contents of all such articles and documents being incorporated herein by reference. [Explanation of symbols]

[0112] 100 Systems 110 Electrochemical Devices 112 Electric current, current direction 114 Magnetic field, magnetic field direction 120 Electromagnetic radiation sources 122 Sensors 124 Polarized Electromagnetic Radiation 126 Received Polarized Electromagnetic Radiation 130 Magneto-optical media 132 Reflective layer 134 Protective layer 200 Systems 222 Sensor 310 Electrochemical Devices 320 Electromagnetic Radiation Source 322 Sensors 330 Magneto-optical media 340 first plurality of optical fiber cables 342 second plurality of optical fiber cables 400 Systems 410 Electrochemical Devices 412 Current 414 Vertical magnetic field 420 Electromagnetic Radiation Source 422 Sensors 424 Polarized Electromagnetic Radiation 426 Polarized Electromagnetic Radiation 430 Magneto-optical media 432 Reflective layer 442 Fiber Optic Cable 500 Systems 530 Magneto-optical media 542 Fiber Optic Cable 630 Magneto-Optical Media 632 Reflective layer 642 Fiber Optic Cable 1160 Current Hotspot 340a Optical fiber, optical fiber cable 340b Optical fiber, optical fiber cable 340c optical fiber, optical fiber cable 340d optical fiber, optical fiber cable 340e Optical Fiber, Optical Fiber Cable 340f optical fiber, optical fiber cable 340g Optical fiber, optical fiber cable 340h Optical fiber, optical fiber cable

Claims

1. an electrochemical device that generates a magnetic field; A sensing device, comprising: Magneto-optical media, an electromagnetic radiation source configured to emit polarized electromagnetic radiation through the magneto-optical medium; and a sensor configured to receive polarized electromagnetic radiation that has passed through the magneto-optical medium; A sensing device comprising: Equipped with The system wherein the sensing device is positioned relative to the electrochemical device such that the magnetic field of the electrochemical device passes through the magneto-optical medium.

2. 2. The system of claim 1, wherein the magneto-optical medium is positioned such that the magnetic field of the electrochemical device interacts with the magneto-optical medium to rotate the plane of polarization of the polarized electromagnetic radiation based on a characteristic of the electrochemical device.

3. 3. The system of claim 1 or 2, wherein the electromagnetic radiation source is positioned relative to the electrochemical device such that the emitted polarized electromagnetic radiation is parallel to the generated magnetic field of the electrochemical device.

4. the magneto-optical medium is integral with the electromagnetic radiation source; or The system of claim 1 , wherein the magneto-optical medium is a layer bonded to the electrochemical device.

5. The system of claim 1 , wherein the magneto-optic medium comprises a thin film magneto-optic crystal.

6. 6. The system of claim 5, wherein the sensing device further comprises a protective layer of insulating polymer or glass film to protect the thin-film magneto-optic crystal, or the magneto-optic crystal is embedded in a polymer or glass fiber to protect the thin-film magneto-optic crystal.

7. the magneto-optical crystal has a high Verdet constant or low optical absorption, or The magneto-optical crystal is selected from the group consisting of barium hexaferrite, terbium gallium garnet, bismuth-substituted rare earth iron garnet, and Na ２ Ce(MoO ４ ) ２ or CeAlO ３ The system according to claim 1 , further comprising at least one of:

8. the electrochemical device that generates a magnetic field is a battery comprising a plurality of cells; the system includes a plurality of electromagnetic radiation sources, each associated with one of the plurality of cells; The system of claim 1 , further comprising a plurality of magneto-optical media each associated with one of the plurality of cells.

9. the system is configured to sequentially operate the plurality of electromagnetic radiation sources; The system of claim 8 , wherein the sensor is configured to receive polarized electromagnetic radiation from each of the electromagnetic radiation sources that has passed through one of the plurality of magneto-optical media.

10. The system of claim 8 , further comprising a plurality of sensors associated with the plurality of electromagnetic radiation sources.

11. The system includes a control module, the control module comprising: determining a first plane of polarization of the emitted electromagnetic radiation or storing a predetermined plane of polarization of the emitted electromagnetic radiation; determining a second plane of polarization of the electromagnetic radiation that has passed through the magneto-optical medium; determining a rotation angle between the first plane of polarization and the second plane of polarization; determining a magnetic field strength of the electrochemical device based on the determined rotation angle; determining a current distribution in the electrochemical device based on the determined magnetic field strength; The system according to any one of claims 1 to 10, configured to:

12. Providing the system of any one of claims 1 to 11; emitting polarized electromagnetic radiation from said electromagnetic radiation source through said magneto-optical medium; receiving, by the sensor, the polarized electromagnetic radiation that has passed through the magneto-optical medium; A sensing method comprising:

13. determining the angle of rotation of the plane of polarization of the reflected electromagnetic radiation. The method of claim 12 further comprising:

14. determining the magnetic field strength of an electrochemical device based on the determined rotation angle; determining a current distribution in the electrochemical device based on the determined magnetic field strength; The method of claim 13 further comprising:

15. 15. The method of claim 14, further comprising repeating the step of determining the current distribution of the electrochemical device periodically or for multiple locations on the electrochemical device, and determining temporal or spatial changes in current distribution information of the electrochemical device.

16. 16. The method of claim 15, wherein said step of projecting said polarized electromagnetic radiation through said magneto-optical medium comprises projecting said electromagnetic radiation from a plurality of fiber optic cables.

17. 17. The method of claim 16, wherein the electromagnetic radiation is emitted individually from the plurality of fiber optic cables over a period of time so as to be incident on the magneto-optic medium in a pattern or sequential manner.

18. 17. The method of claim 16, wherein the electromagnetic radiation is emitted simultaneously from the plurality of fiber optic cables, the plurality of fiber optic cables being configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

19. The system includes a control module configured to receive the change in current distribution information; the control module is configured to alter a parameter of the electrochemical device based on the change in current distribution information; or 19. The method of any one of claims 15 to 18, wherein the control module is configured to activate an alarm based on the change in current distribution information.

20. A magneto-optical medium; an electromagnetic radiation source configured to emit polarized electromagnetic radiation through the magneto-optical medium; a sensor configured to receive polarized electromagnetic radiation reflected from the electromagnetic radiation source through the magneto-optical medium; Equipped with A sensing device, wherein the electromagnetic radiation source comprises a first plurality of fiber optic cables or the sensor comprises a second plurality of fiber optic cables.

21. 20. The sensing device of claim 18, further comprising at least one of a reflective layer or a protective medium.

22. 20. The sensing device of claim 18, wherein the first plurality of fiber optic cables and the second plurality of fiber optic cables are arranged in a mesh or woven array.

23. The sensing device of claim 20 , wherein at least one of the first plurality of fiber optic cables or the second plurality of fiber optic cables is configured to be embedded within the electrochemical device.

24. the first plurality of fiber optic cables are configured to individually emit electromagnetic radiation over a period of time such that the electromagnetic radiation is incident on the magneto-optical medium in a pattern or sequential manner; or 22. The sensing device of claim 20 or 21, wherein the electromagnetic radiation is emitted simultaneously from the first plurality of fiber optic cables, the first plurality of fiber optic cables being configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

25. an electromagnetic radiation source comprising a first plurality of fiber optic cables for emitting polarized electromagnetic radiation; a sensor configured to receive polarized electromagnetic radiation, the sensor comprising a magneto-optical medium through which the polarized electromagnetic radiation from the electromagnetic radiation source passes; A sensing device comprising:

26. the sensor comprises a second plurality of fiber optic cables; The sensing device of claim 23 , wherein the second plurality of fiber optic cables includes the magneto-optic medium.

27. 25. The sensing device of claim 24, wherein the at least one fiber optic cable comprises a reflective layer.

28. 26. The sensing device of claim 23, wherein the first and second plurality of fiber optic cables are arranged in a mesh or woven array.

29. 27. The sensing device of claim 26, wherein at least one of the first plurality of fiber optic cables and the second plurality of fiber optic cables are configured to be embedded within the electrochemical device.

30. the first plurality of fiber optic cables are configured to individually emit electromagnetic radiation over a period of time; or 30. The sensing device of claim 25, wherein the electromagnetic radiation is emitted simultaneously from the first plurality of fiber optic cables, the first plurality of fiber optic cables being configured to emit electromagnetic radiation at different wavelengths than adjacent fiber optic cables.

31. 31. Use of a sensing device according to any one of claims 18 to 30 for determining current changes in an electrochemical device.

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