Battery pack and energy storage device

Abstract

The invention discloses a battery pack and an energy storage device, and belongs to the technical field of batteries. The battery pack comprises a plurality of battery cells arranged in a row and a first optical fiber sensor; the first optical fiber sensor comprises a sensing optical fiber and a plurality of gratings formed on the sensing optical fiber, and the plurality of gratings are distributed at intervals along the extension direction of the sensing optical fiber; the sensing optical fiber is fixed to the side walls of at least part of the battery cells in the multiple battery cells in the arrangement direction of the multiple battery cells, a grating is arranged between the sensing optical fiber and two adjacent fixing points in the multiple fixing points of the at least part of battery cells, and a gap is formed between two opposite surfaces of two adjacently arranged battery cells in the multiple battery cells in the arrangement direction; at least a portion of the plurality of slits is at least partially covered by the grating. The battery pack can improve the monitoring sensitivity of the first optical fiber sensor to the battery deformation state.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to battery packs and energy storage devices. Background Technology

[0002] Battery packs are commonly used in power supply scenarios such as new energy vehicles and energy storage power stations. It is difficult to completely avoid thermal runaway in battery packs. Therefore, it is essential to identify abnormal faults in battery packs in advance to understand their working status and prevent thermal runaway.

[0003] By monitoring the expansion state of the battery pack, not only can early warnings of thermal runaway risks be provided, but structural risks can also be identified. In related technologies, fiber optic sensors are laid on the large surface of the battery cell, with the axis of the sensors parallel to the surface of the cell. These sensors are used to identify cell deformation and thus determine the degree of expansion.

[0004] However, the aforementioned arrangement of the fiber optic sensor causes the expansion direction of the battery cell to be along the normal direction of the fiber optic sensor, resulting in low sensitivity of the fiber optic sensor to the degree of battery cell expansion, thereby reducing the monitoring accuracy. Summary of the Invention

[0005] This disclosure provides a battery pack and energy storage device, which can solve the technical problems existing in related technologies. The technical solution is shown below.

[0006] On one hand, a battery pack is provided, the battery pack comprising: a plurality of battery cells arranged in a row and a first optical fiber sensor; the first optical fiber sensor comprising: a sensing optical fiber and a plurality of gratings formed on the sensing optical fiber, the plurality of gratings being spaced apart along the extension direction of the sensing optical fiber; along the arrangement direction of the plurality of battery cells, the sensing optical fiber is fixed to the sidewall of at least some of the battery cells, the gratings being provided between two adjacent fixing points of the sensing optical fiber and the at least some of the battery cells, a gap being provided between two opposite faces of two adjacent battery cells arranged in the arrangement direction, at least a portion of the gaps being at least partially covered by the gratings.

[0007] The battery pack provided in this disclosure has a sensing optical fiber fixed to the sidewall of at least a portion of the multiple battery cells along the arrangement direction of the cells. This ensures that the extension direction of the first optical fiber sensor is perpendicular to the large surface of the cell and aligned with the expansion direction of the cell, thereby improving the sensitivity of the first optical fiber sensor to cell deformation. Furthermore, a grating is placed between two adjacent fixing points of the sensing optical fiber and the multiple fixing points of the cell, at least a portion of the multiple slits are at least partially covered by the grating. This allows the reflected wavelength of the grating to change accordingly in response to the deformation of the slit, enabling monitoring of the deformation state of the cells on both sides of the slit. Compared to attaching the grating to the outer wall (e.g., sidewall, large surface, etc.) of the cell to monitor the deformation of the cell casing, the slits are more sensitive to the deformation state of the cell, improving the sensitivity of the first optical fiber sensor to battery deformation.

[0008] In some possible implementations, the slit is at least partially covered by the grating to ensure that the monitored slit is effectively monitored at any position along the extension direction of the sensing fiber.

[0009] In some possible implementations, the tension of the sensing optical fiber located between the fixed points and along the gap is greater than a certain value, enabling synchronous monitoring of the cell's stress and temperature.

[0010] In some possible implementations, the tension of the sensing fiber located between the fixed points and along the slit is 0.5N-1.5N, ensuring that the grating on it can detect any dimensional changes in the slit, thereby improving monitoring accuracy and sensitivity.

[0011] In some possible implementations, along the arrangement direction of the plurality of cells, there is a gap between at least two adjacent fixing points among the plurality of fixing points, and the number of gaps between the at least two adjacent fixing points is one or more; when the number of gaps between the at least two adjacent fixing points is more than one, at least a portion of the gaps are covered by the grating.

[0012] In some possible implementations, the sensing fiber is fixed to each of the plurality of battery cells, and there is a gap between the sensing fiber and the fixing point of any two adjacent battery cells' sidewalls, and each gap is covered by the grating, ensuring that the plurality of battery cells in the battery pack are effectively monitored.

[0013] In some possible implementations, a portion of the sensing fiber in the first fiber optic sensor, fixed to the wall of the plurality of battery cells, is in a tensioned state while another portion is in a relaxed state. The tensioned state is defined as a tension greater than zero, and the relaxed state as a tension equal to zero. A grating formed on the tensioned sensing fiber is used to measure stress and temperature; a grating formed on the relaxed sensing fiber is used to measure temperature. This decoupling facilitates the acquisition of a single stress data point, making the monitoring of the battery cell deformation state more accurate and intuitive.

[0014] As an example, the plurality of gratings cover the corresponding slits, and some of the gratings are formed on the taut sensing fiber, while the remaining gratings are formed on the slack sensing fiber.

[0015] As another example, some of the plurality of gratings cover the corresponding gaps and are formed on the tensioned sensing fiber; the remaining portion of the plurality of gratings covers the wall of the cell and is formed on the relaxed sensing fiber, wherein the two fixing points corresponding to the relaxed sensing fiber are located on the same wall of the cell.

[0016] In some possible implementations, the sensing fiber in the first fiber optic sensor, which is fixed to the sidewalls of the plurality of battery cells, is in a state of tension. The first fiber optic sensor is used to measure stress and temperature. The state of tension is defined as the tension of the sensing fiber being greater than 0.

[0017] Furthermore, the battery pack also includes a second fiber optic sensor, which comprises a sensing fiber and a plurality of gratings formed on the sensing fiber, the plurality of gratings being spaced apart along the extension direction of the sensing fiber; the sensing fiber of the second fiber optic sensor is fixed to the sidewalls of the two outermost of the plurality of battery cells and is in a relaxed state, wherein the relaxed state means that the tension of the sensing fiber is equal to 0; the positions of the plurality of gratings of the fiber optic sensor correspond one-to-one, enabling the second fiber optic sensor to be used for temperature measurement. This facilitates decoupling to obtain a single stress data point, making the monitoring of the deformation state of the battery cells more accurate and intuitive.

[0018] In some possible implementations, the sensing optical fiber is fixed to the sidewall of the battery cell by a fastener.

[0019] In some possible implementations, the battery pack further includes a support member fixedly connected to the sidewall of the battery cell, and the support member supports the grating.

[0020] In some possible implementations, signal cables and cable ties are provided on the plurality of battery cells, and the first fiber optic sensor is integrated into at least one of the signal cables and the cable ties.

[0021] In some possible implementations, the battery pack further includes a battery management unit, which is used to calculate the deformation state of the battery pack based on stress and temperature data of the battery pack measured by the first fiber optic sensor or the second fiber optic sensor.

[0022] On the other hand, an energy storage device is provided, the energy storage device comprising: a power converter and at least one battery pack as described above; the at least one battery pack is connected in series to output to the power converter or connected in parallel to output to the power converter; the power converter is used to perform power conversion on the voltage output by the at least one battery pack.

[0023] The energy storage device provided in this disclosure has all the advantages of the battery pack mentioned above, which will not be repeated here.

[0024] In some possible implementations, the energy storage device further includes a battery control unit, which is configured to receive battery pack deformation state information output by the battery management unit of the battery pack, and to control the at least one battery pack according to the deformation state information of each battery pack in the at least one battery pack.

[0025] When the battery pack is in a high-risk state of thermal runaway or a high-risk state of structure, the battery control unit can control the battery pack to cut off power or issue an alarm signal.

[0026] In some possible implementations, the energy storage device further includes a calibration module for calibrating at least one of the following states of the battery pack based on the stress inflection point data of the battery pack: state of charge, state of energy, state of health, state of power, and temperature state; wherein the stress inflection point data of the battery pack is obtained by measuring the first fiber optic sensor of the battery pack.

[0027] Furthermore, this disclosure also provides a battery deformation state monitoring device, which includes any of the battery packs mentioned above.

[0028] Furthermore, this disclosure also provides a battery deformation state monitoring method, which is applied to any of the aforementioned battery packs or battery deformation state monitoring devices. The battery deformation state monitoring method includes:

[0029] The grating of the first fiber optic sensor receives laser pulse signals from the laser emitter and outputs wavelength signals, which are used to indicate stress and temperature information of at least some of the multiple battery cells.

[0030] The wavelength signal is demodulated by an optical fiber demodulator to obtain stress and temperature information of at least some of the multiple battery cells.

[0031] Based on the stress and temperature information of at least some of the cells, obtain the deformation state of at least some of the cells and the deformation state of the battery pack in which they are located. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a first exemplary battery deformation state monitoring device provided in an embodiment of this disclosure;

[0033] Figure 2 This is a schematic diagram of the structure of an exemplary fiber optic sensor provided in an embodiment of the present disclosure;

[0034] Figure 3 This is a schematic diagram of the structure of a second exemplary battery deformation state monitoring device provided in an embodiment of this disclosure;

[0035] Figure 4 This is a schematic diagram of the structure of a third exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0036] Figure 5 This is a schematic diagram of the structure of the fourth exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0037] Figure 6 This is a schematic diagram of the structure of the fifth exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0038] Figure 7 This is a schematic diagram of the structure of the sixth exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0039] Figure 8 This is a schematic diagram of the structure of the seventh exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0040] Figure 9 This is a schematic diagram of the structure of the eighth exemplary battery deformation state monitoring device provided in the embodiments of this disclosure;

[0041] Figure 10 A schematic diagram illustrating the arrangement of an exemplary battery deformation state monitoring device in a battery pack, provided in an embodiment of this disclosure;

[0042] Figure 11This is a schematic diagram illustrating the arrangement of another exemplary battery deformation state monitoring device in a battery pack, as provided in this embodiment of the disclosure.

[0043] Figure 12 This is a schematic diagram of the structure of the ninth exemplary battery deformation state monitoring device provided in the embodiments of this disclosure.

[0044] It should be noted that the diagonal lines in the above figures are used to illustrate the grating 112. The size of the grating 112 in the figures is enlarged to highlight the position and arrangement of the grating 112, and does not mean that the actual size of the grating 112 is larger than the actual size of the sensing fiber.

[0045] The reference numerals in the attached figures represent:

[0046] 101. First fiber optic sensor; 102. Second fiber optic sensor;

[0047] 111. Sensing fiber; 1110. Fixed point; 1111. Fiber segment; 1112. Fixture; 112. Grating;

[0048] 12. Laser emitter;

[0049] 13. Fiber optic demodulator;

[0050] 14. Connect the optical fiber;

[0051] 15. Support components;

[0052] 20. Battery cell; 201. Side wall of battery cell; 202. Large surface of battery cell; 21. Gap in battery cell; 22. Buffer material layer;

[0053] 200. Battery cell assembly unit. Detailed Implementation

[0054] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0055] In the description of the embodiments of this disclosure, it should be understood that the terms "axial", "radial", "length", "width", "thickness", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0056] To monitor the operating status of battery packs and prevent risks such as thermal runaway caused by abnormal battery pack malfunctions, real-time monitoring of battery pack operating parameters, including current, voltage, and temperature, is typically required. However, with the increasing number of battery packs used and the diversification of their application scenarios, it is difficult to accurately monitor the battery's operating state based solely on operating parameters such as current, voltage, and temperature. Currently, monitoring the battery's expansion state using fiber optic sensors can provide early warnings of thermal runaway risks and identify structural risks associated with the battery.

[0057] Fiber optic sensors can sense the deformation of the battery cell, causing it to stretch or contract. Therefore, fiber optic sensors can monitor the expansion state of the battery, thereby monitoring and issuing warnings about the risk of thermal runaway, mechanical abuse, or other abnormal malfunctions.

[0058] Related technologies typically employ fiber optic sensors embedded in the large surfaces of multiple battery cells within a battery pack to identify cell deformation. For square cells, the large surface refers to the area defined by the length and height sides of the cell. However, since cell expansion is primarily concentrated perpendicular to the large surface, this fiber optic sensor arrangement results in the expansion direction being along the normal direction of the sensor. This leads to lower sensitivity of the fiber optic sensor in detecting cell expansion, thus reducing monitoring accuracy. Furthermore, some battery packs use buffer layers composed of insulating foam, U-shaped frames, or aerogel between the large surfaces of the cells to absorb stress, minimizing deformation along the direction perpendicular to the large surface. This further deteriorates the monitoring of cell deformation.

[0059] To address the aforementioned technical problems, this disclosure provides a novel battery pack, as shown in the attached figure. Figure 1 As shown, the battery pack includes a plurality of battery cells 20 arranged in a row and a first fiber optic sensor 101. The first fiber optic sensor 101 includes a sensing fiber 111 and a plurality of gratings 112 formed on the sensing fiber 111, the plurality of gratings 112 being spaced apart along the extension direction of the sensing fiber 111. Along the arrangement direction of the plurality of battery cells 20, the sensing fiber 111 is fixed to the sidewall 201 of at least a portion of the battery cells 20. A grating 112 is provided between two adjacent fixing points 1110 of the plurality of fixing points 1110 of the sensing fiber 111 and at least a portion of the battery cells 20. A gap 21 is provided between two adjacent battery cells 20 on opposite sides in the arrangement direction, and at least a portion of the gap 21 is at least partially covered by the gratings 112.

[0060] Taking cell 20 as an example, which is a square cell, as shown in the attached diagram. Figure 1As shown, the length direction of the square battery cell 20 is along the X direction, the width direction is along the Y direction, and the height direction is along the Z direction. In this embodiment, the "sidewall 201 of the battery cell 20" refers to the surface defined by the width side and the height side of the battery cell 20, and the large surface 202 of the battery cell 20 refers to the surface defined by the length side and the height side of the battery cell 20. It can be seen that along the arrangement direction of the plurality of battery cells 20, the large surfaces 202 of any two adjacent battery cells 20 are opposite each other, and a gap 21 is formed between the large surfaces 202 of the battery cells 20.

[0061] For grating 112, see attached Figure 2 As shown, it can be obtained by etching a specific part of the sensing fiber 111. Along the extension direction of the sensing fiber 111, multiple gratings 112 can be etched on a single sensing fiber 111. The multiple gratings 112 are distributed at intervals along the extension direction of the sensing fiber 111, so that the first fiber optic sensor 101 has the characteristics of small size and multiplexing.

[0062] The grating 112 is sensitive to stress and temperature changes, enabling it to measure stress and temperature. The principle of stress and temperature measurement using the fiber optic sensor based on the grating 112 is as follows: When the grating 112 is subjected to stress and temperature changes, its refractive index changes accordingly, causing a shift in its reflected wavelength. Therefore, by acquiring the wavelength signal output by the grating 112, information on the stress and temperature changes experienced by the grating 112 can be obtained. Combined with the initial state of the measured battery cell 20, this stress and temperature change information is calibrated, allowing the acquisition of the stress and temperature values ​​of the battery cell 20.

[0063] The structure of grating 112 can be cylindrical, conical, or other shapes. In some examples, grating 112 is a Fiber Bragg Grating (FBG). A Bragg grating is a reflective structure formed in the core of an optical fiber with periodic perturbations to the effective refractive index. When light waves pass through the Bragg grating, diffraction occurs according to Bragg's law, causing light waves of specific wavelengths to be reflected while other wavelengths are transmitted. Thus, the Bragg grating effectively acts as a selective reflector for light waves, possessing advantages such as high precision, high sensitivity, strong anti-interference capability, and long lifespan.

[0064] In this embodiment, the gap 21 is formed between two adjacent cells 20, and it simultaneously reflects the deformation state of the two adjacent cells 20. That is, the grating 112 covering the gap 21 measures the stress and temperature of the cells 20 on both sides of the gap 21. When gratings 112 are set at multiple gaps 21, the stress and temperature of the cells 20 on both sides of each gap 21 can be measured. Thus, not only can the deformation state of these cells 20 be known, but also the deformation state of the battery pack in which these cells 20 are located can be further known. In addition, in this embodiment, the stress measured by the grating 112 can be regarded as the expansion force of the cell 20.

[0065] The battery pack provided in this embodiment fixes a sensing optical fiber 111 to the sidewall 201 of at least a portion of the multiple battery cells 20 along the arrangement direction of the multiple battery cells 20. This ensures that the extension direction of the first optical fiber sensor 101 is perpendicular to the large surface 202 of the battery cell 20 and consistent with the expansion direction of the battery cell 20, which improves the sensitivity of the first optical fiber sensor 101 to detecting the deformation of the battery cell 20. Furthermore, a grating 112 is disposed between two adjacent fixing points 1110 of the multiple fixing points 1110 of the sensing optical fiber 111 and the battery cell 20, at least a portion of the multiple slits 21 are at least partially covered by the grating 112. Thus, the reflected wavelength of the grating 112 can change accordingly in response to the deformation of the slit 21, enabling monitoring of the deformation state of the battery cells 20 on both sides of the slit 21. Compared with the grating 112 being attached to the outer wall of the cell 20 (e.g., side wall 201, large surface 202, etc.) to monitor the deformation of the cell casing, the gap 21 is more sensitive to the deformation state of the cell 20, thereby improving the monitoring sensitivity of the first fiber optic sensor 101 to the deformation state of the battery.

[0066] As mentioned above, the gap 21 is more sensitive to the deformation state of the battery cell 20, such as expansion, compared to the battery cell housing. This is because the size change of the gap 21 corresponds to the relative change in deformation between two adjacent battery cells 20. Once either of the two battery cells 20 deforms (e.g., expands), the gap 21 can quickly respond to the expansion of the battery cell and reflect a relatively accurate size change. However, in the case of placing the fiber grating on the surface of the battery cell housing to monitor its surface deformation, during the expansion of the battery cell 20, the battery cell housing usually does not deform as a whole, but rather locally. This not only leads to a mismatch between the monitoring position and the deformation position, but also, since the deformation of the battery cell housing itself is usually small, the deformation signal it generates is usually weak. In particular, some gaps 21 of multiple battery cells 20 are filled with a buffer material layer 22 composed of thermal insulation foam, U-shaped frame, aerogel, etc. (see...). Figure 1The buffer material layer 22 increases the difficulty of cell deformation testing and places higher demands on the sensitivity of cell expansion force monitoring. However, by monitoring the size change of the gap 21, the above problems can be avoided. Therefore, by ensuring that at least some of the gaps 21 are at least partially covered by the grating 112, the response to the battery deformation state is more sensitive and the signal sensitivity is higher.

[0067] It should be noted that, as shown in the attached document... Figure 1 As shown, the battery pack also includes a laser emitter 12 and an optical fiber demodulator 13 connected to the optical fiber sensor. The laser emitter 12 is used to emit laser pulse signals into the first optical fiber sensor 101, and the optical fiber demodulator 13 is used to demodulate the signals from the first optical fiber sensor 101. In application, a laser pulse signal is emitted into the sensing optical fiber 111 through the laser emitter 12. The laser pulse signal undergoes a characteristic change when passing through the grating 112, forming a wavelength signal that responds to the deformation of the slot 21. The optical fiber demodulator 13 demodulates the wavelength signal to obtain the deformation information of the two battery cells 20 corresponding to the slot 21. For example, when some of the multiple battery cells 20 expand, the size of the corresponding slot 21 will increase, causing the grating 112 to stretch along its axial direction, thereby increasing the reflected wavelength of the grating 112. In this way, by monitoring the wavelength change of the grating 112 and demodulating it with the optical fiber demodulator 13, the deformation information of the two battery cells 20 corresponding to the slot 21 can be monitored in a timely and effective manner.

[0068] As mentioned above, the sensing fiber 111 is fixed to the sidewall 201 of at least a portion of the battery cells 20, so that at least a portion of the gaps 21 are at least partially covered by the grating 112 (that is, the grating 112 is arranged opposite to the gaps 21). Based on this concept, it is not excluded that, provided that the grating 112 covers the gaps 21, the sensing fiber 111 may also be fixed to the top or bottom surface of at least a portion of the battery cells 20, wherein the top surface of the battery cell 20 refers to the surface on which the electrode post is arranged, and the bottom surface of the battery cell 20 is the surface opposite to its top surface.

[0069] When the battery expands during charging and discharging, the deformation at the middle position of the cell 20 along the height direction is relatively large. This allows the sensing fiber 111 to be fixed to the middle region or near the middle region of the side wall 201 of the cell 20, so that the grating 112 can sense a more concentrated change in expansion force.

[0070] In this embodiment of the disclosure, at least a portion of the plurality of slits 21 are at least partially covered by the grating 112, including the following situations: the slits 21 are completely covered by at least a portion of the grating 112; or at least a portion of the slits 21 are covered by the grating 112. Figure 1The example shows that the slit 21 is partially covered by the grating 112 to ensure that the monitored slit 21 is effectively monitored at any position in the extension direction of the sensing fiber 111, thereby improving the monitoring accuracy.

[0071] As mentioned above, the grating 112 simultaneously senses the stress change (i.e., expansion force change) and temperature change of the battery cell 20. By keeping the grating 112 in a tensioned state, it achieves the purpose of simultaneously detecting stress and temperature. By keeping the grating 112 in a relaxed state, it achieves the purpose of detecting only temperature.

[0072] In this embodiment, the tension of the sensing fiber 111 located between fixed points 1110 and in the path gap 21 is greater than 0. In this way, the grating 112 formed on the sensing fiber 111 and covering the gap 21 is also in a tensioned state, so as to realize the synchronous monitoring of the stress and temperature of the battery cell 20, while ensuring the monitoring sensitivity of the grating 112.

[0073] The tensioning of the fiber segment of the sensing fiber 111 is achieved by fixing the sensing fiber 111 to the sidewalls of the multiple battery cells 20. For the tensioned sensing fiber 111, the extension direction of the sensing fiber 111 can be the same as the extension direction of the slot 21 (i.e.,...). Figure 1 The vertical direction (up and down) can be perpendicular, or not perpendicular (for example, in...). Figure 1 The horizontal arrangement shown is moderately tilted, i.e., obliquely arranged. For the scheme where the extension direction of the sensing fiber 111 is perpendicular to the extension direction of the slot 21, the monitoring resolution is relatively higher. For the oblique arrangement, the monitoring resolution will decrease to some extent, but it can effectively increase the range of the fiber for stress signals. The arrangement scheme of the sensing fiber 111 can be selected according to actual needs. In the monitoring device involved in the embodiments of this disclosure, a vertical scheme is used as an example.

[0074] Considering that the battery cell 20 typically stores a certain amount of charge at the factory, approximately 30% of its state of charge (SOC), this causes the battery cell 20 to be in an expanded state, and the expansion force is not at its minimum. In this situation, if the tension of the grating 112 is set to a low value, the deformation signal may not be detected when the gap 21 becomes smaller.

[0075] To prevent the grating 112 from failing to detect the size change of the slit 21, the tension of the sensing fiber 111 located between the fixed points 1110 and the path slit 21 can be 0.5N-1.5N. For example, it can be point values ​​such as 0.5N, 0.6N, 0.7N, 0.8N, 0.9N, 1N, 1.1N, 1.2N, 1.3N, 1.4N, 1.5N, or any range formed by any two point values.

[0076] In this way, the taut sensing fiber 111 further possesses pre-tension, ensuring that the grating 112 on it can detect any dimensional changes in the gap 21, thus improving monitoring accuracy and sensitivity. Regardless of whether the size of the gap 21 increases or decreases, even if the change is very small, the grating 112 can accurately detect it. For example, during the first few cycles of the battery cell 20 after leaving the factory, even though the overall expansion force of the battery cell 20 is still low, the expansion state of the battery cell 20 can still be effectively monitored because the grating 112 is in a pre-tensioned state.

[0077] The tension of the sensing fiber 111 can be set to 0.5N-1.5N, which can be achieved by pre-positioning the multiple fixing points 1110 on the sensing fiber 111 and the multiple battery cells 20, and then applying a pre-tension force of 0.5N-1.5N to the sensing fiber 111 using a tension gauge. Then, the sensing fiber 111 is fixed to the multiple battery cells 20 and the pre-tension force is released. In this way, the sensing fiber 111 has pre-tension force while completing the assembly. For example, the sensing fiber 111 can be initially positioned using adhesive dispensing, then a pre-tension force can be applied, and after the adhesive has cured, the pre-tension force can be released.

[0078] In this embodiment of the present disclosure, the sensing optical fiber 111 is fixed to the sidewall of at least a portion of the multiple battery cells 20. That is, the sensing optical fiber 111 is fixed to the sidewall of all the multiple battery cells 20, or to the sidewall of a portion of the multiple battery cells 20. It is not excluded that, in addition to being fixed to the sidewall of the battery cell 20, the sensing optical fiber 111 may also be fixed to the end plate or other structural components on the outside of the multiple battery cells 20.

[0079] As attached Figure 3 As shown, along the arrangement direction of the multiple cells 20, the sensing optical fiber 111 has multiple fixed points 1110. The portion of the sensing optical fiber 111 located between any two adjacent fixed points 1110 can be called an optical fiber segment 1111. The multiple fixed points 1110 divide the sensing optical fiber 111 into multiple optical fiber segments 1111.

[0080] A grating 112 is provided on the optical fiber segment 1111 between any two adjacent fixed points 1110. The number of gratings 112 can be set to one or more. The way the sensing optical fiber 111 is fixed on multiple cells 20 determines the arrangement of the gratings 112. Some feasible implementation methods are as follows:

[0081] In some examples, such as the attached Figure 3 and appendix Figure 4 As shown, along the arrangement direction of the plurality of battery cells 20, there is a gap 21 between any two adjacent fixing points 1110 among the plurality of fixing points 1110. (See attached diagram) Figure 3 As shown, the number of gaps 21 between two adjacent fixed points 1110 can be one. With this scheme, each gap 21 can be covered by a grating 112. (See attached image.) Figure 4 As shown, the number of gaps 21 between two adjacent fixed points 1110 can also be multiple. For this scheme, one gap 21 can be covered by the grating 112, or multiple gaps 21 can be covered by the grating 112.

[0082] Appendix Figure 4 The example illustrates that the number of gratings 112 is less than the number of slots 21 formed by the multiple battery cells 20. Thus, the gratings 112 cover a portion of the slots 21. This simplifies the arrangement of the gratings 112 in the first fiber optic sensor 101 and simplifies the demodulation operation. For example, along the arrangement direction of the multiple battery cells 20, the multiple battery cells 20 are divided into multiple battery cell units. The number of battery cells 20 contained in each battery cell unit can be the same or different, and the number of battery cells 20 contained in a battery cell unit can be one, two, three, or more. A grating 112 is set for each battery cell unit, and the grating 112 can be arranged opposite to any slot 21 in the current battery cell unit to realize the monitoring of the deformation state of the battery cell unit.

[0083] In other examples, such as the appendix Figure 6 As shown, along the arrangement direction of the plurality of battery cells 20, a gap 21 is formed between some adjacent fixing points 1110, and correspondingly, the remaining adjacent fixing points 1110 are separated by the sidewall 201 of the battery cell 20. For this scheme, the number of gaps 21 between two adjacent fixing points 1110 can be one (see...). Figure 6 There can be multiple (not shown in the figure).

[0084] A typical implementation plan is attached. Figure 3 As shown, an example illustrates that a sensing fiber 111 is fixed to each of a plurality of battery cells 20. A gap 21 exists between the sensing fiber 111 and the fixing point 1110 of any two adjacent battery cells 20 on their sidewalls, and each gap 21 is covered by a grating 112. This implementation can monitor the expansion information of all battery cells 20 in the battery pack, achieving higher monitoring accuracy.

[0085] Since the grating 112 is sensitive to both stress and temperature changes, when the grating 112 is in a tensioned state, the wavelength signal output by the grating 112 is usually a composite signal of stress and temperature signals. When the grating 112 is in a relaxed state, the wavelength signal output by the grating 112 is a composite signal of a single temperature signal.

[0086] In some implementation schemes (1), stress and temperature information are measured by gratings 112 formed on the tensioned sensing optical fibers 111. (See attached...) Figure 3 and attached Figure 4 As shown, the sensing fiber 111 fixed to the sidewalls of multiple battery cells 20 in the first fiber optic sensor 101 is in a tensioned state (the gratings 112 of the sensing fiber 111 in the tensioned state are also in a tensioned state accordingly). The first fiber optic sensor 101 is used to measure stress and temperature. That is, the first fiber optic sensor 101 measures the stress and temperature information of the battery cells 20 located on both sides of any gap 21 between adjacent fixed points 1110; wherein, the tensioned state is that the tension of the sensing fiber 111 is greater than 0.

[0087] In this scheme, the information output by the first fiber optic sensor 101 is a composite information reflecting stress and temperature, and is output in the form of a wavelength signal. By analyzing this composite information, the deformation state of at least some of the multiple cells 20 can be known, and correspondingly, the deformation state of the battery pack in which the multiple cells 20 are located can also be known.

[0088] In other implementations (2), stress and temperature information of the battery cells 20 located on both sides of the gap 21 between adjacent fixed points 1110 are measured by gratings 112 formed on the sensing optical fibers 111 in the tensioned state, and temperature information of the battery cells 20 located on both sides of the gap 21 between adjacent fixed points 1110 are measured by gratings 112 formed on the sensing optical fibers 111 in the relaxed state, so as to obtain a single stress data through decoupling, making the monitoring of the deformation state of the battery cells more accurate and intuitive.

[0089] Implementation scheme (2) can be further implemented through the following schemes:

[0090] In some implementation schemes (2.1), as shown in the appendix Figure 5 -Appendix Figure 7 As shown, in the first fiber optic sensor 101, a portion of the sensing fiber 111 fixed to the wall of the plurality of battery cells 20 is in a tensioned state while another portion is in a relaxed state. The tensioned state is defined as the tension of the sensing fiber 111 being greater than 0, and the relaxed state as the tension of the sensing fiber 111 being equal to 0. A grating 112 formed on the tensioned sensing fiber 111 is used to measure the stress information and temperature of the battery pack; the grating 112 formed on the relaxed sensing fiber 111 is used to measure the temperature of the battery pack. The "wall of the battery cell 20" mentioned here includes the sidewall 201 of the battery cell 20, and may further include the large surface 202 of the battery cell 20.

[0091] Appendix Figure 5The example illustrates multiple gratings 112 covering corresponding slits 21, with some gratings 112 formed on a tensioned sensing fiber 111 and the remaining gratings 112 formed on a relaxed sensing fiber 111. That is, the fiber segment 1111 formed by any two adjacent fixed points 1110 passes through the slit 21. Some fiber segments 1111 are in a tensioned state, and correspondingly, the gratings 112 connected to the tensioned fiber segments 1111 are also in a tensioned state. The remaining fiber segments 1111 are in a relaxed state, and correspondingly, the gratings 112 connected to the relaxed fiber segments 1111 are also in a relaxed state.

[0092] In some implementation schemes (2.2), as shown in the appendix Figure 6 and attached Figure 7 As shown, some of the multiple gratings 112 cover the corresponding slits 21 and are formed on the tensioned sensing fiber 111; the remaining gratings 112 cover the wall of the cell 20 and are formed on the relaxed sensing fiber 111. The two fixing points 1110 corresponding to the relaxed sensing fiber 111 are located on the same wall of the cell 20. That is, some of the multiple fiber segments 1111 are connected to the slits 21, while the remaining fiber segments are not connected to the slits 21. Among them, the fiber segments 1111 connected to the slits 21 are in a tensioned state, and correspondingly, the gratings 112 connected to the relaxed fiber segments 1111 are also in a tensioned state. The fiber segments 1111 not connected to the slits 21 are in a relaxed state, and correspondingly, the gratings 112 connected to the relaxed fiber segments 1111 are also in a relaxed state.

[0093] Implementation schemes (2.1) and (2.2) achieve decoupling of single stress data by placing different parts of the first fiber optic sensor 101 in two states: tension (force measurement + temperature measurement) and relaxation (temperature measurement). Moreover, these implementation schemes have high tolerance for the thickness and assembly tolerance of the battery cell 20 because the length of the relaxed sensing fiber 111 can be arbitrarily adjusted.

[0094] For implementation scheme (2.2), the relaxed sensing fiber 111 and the grating 112 disposed thereon can be arranged at any position of the plurality of cells 20, for example, they can be arranged at the attached Figure 6 The sidewall 201 of the battery cell 20 shown can also be arranged as shown in the attached figure. Figure 7The large surface 202 of the battery cell 20 shown is positioned, for example, at the center of the large surface. Temperature is more reliable at the center of the large surface of the battery cell 20, and compared to other larger temperature sensors, the grating 112, due to its smaller size, is easier to place at the center of the large surface of the battery cell 20. When the sensing fiber 111 is placed at multiple different locations on the battery cell 20, the sensing fiber 111 may need to be bent. The radius of the bend should be as large as possible to increase the bending radius of the fiber and avoid breakage due to right-angle bends.

[0095] Regarding the aforementioned implementation schemes (2.1) and (2.2), the grating 112 formed on the relaxed sensing fiber 111 and the grating 112 formed on the tensioned sensing fiber 111 can be made as close as possible to achieve a more accurate stress decoupling effect. The implementation can be as follows: by winding a single sensing fiber 111, the relaxed grating 112 and the tensioned grating 112 are brought close together; for example, they are arranged opposite each other. Alternatively, by attaching... Figure 6 As shown, each relaxed grating 112 is arranged adjacent to each tightened grating 112 so that the temperature information measured by the two gratings 112 is closer.

[0096] In some implementation schemes (2.3), as shown in the appendix Figure 8 As shown, the battery pack also includes a second fiber optic sensor 102, which includes a sensing fiber 111 and a plurality of gratings 112 formed on the sensing fiber 111. The plurality of gratings 112 are spaced apart along the extension direction of the sensing fiber 111. The sensing fiber 111 of the second fiber optic sensor 102 is fixed to the sidewalls of the two outermost cells 20 of the plurality of cells 20 and is in a relaxed state, wherein the relaxed state means that the tension of the sensing fiber 111 is equal to 0. The positions of the plurality of gratings 112 of the fiber optic sensor 102 correspond one-to-one with the positions of the plurality of gratings 112 of the fiber optic sensor 101, so that the second fiber optic sensor 102 is used to measure the temperature of the battery pack.

[0097] The implementation scheme (2.3) illustrates that force and temperature measurement can be achieved by arranging the first fiber optic sensor 101, and temperature measurement can be achieved by arranging the second fiber optic sensor 102, thereby achieving decoupling of single stress data. This implementation scheme has higher operational flexibility.

[0098] The second fiber optic sensor 102 and the first fiber optic sensor 101 can be the same type of fiber optic sensor, the difference being that they are arranged differently on the multiple cells 20.

[0099] In this design, the positions of the multiple gratings 112 of the second fiber optic sensor 102 correspond one-to-one with the positions of the gratings 112 of the first fiber optic sensor 101, ensuring that the temperature data monitored by both are as close as possible. The spacing between the second fiber optic sensor 102 and the first fiber optic sensor 101 can be minimized; for example, the second fiber optic sensor 102 and the first fiber optic sensor 101 can be arranged in a nearly parallel manner.

[0100] In this embodiment of the disclosure, the sensing optical fiber 111 and the wall (including the sidewall 201, and may also include) of the battery cell 20 are connected. Figure 7 The connection between the large surfaces 202 shown can be achieved through bonding (e.g., using adhesive dispensing) or by fastener connection, for example, Figure 1 An example is shown where the sensing fiber 111 is bonded to the side surface of the cell 20 using an adhesive dispensing method.

[0101] For fastener connection schemes, see attached... Figure 5 As shown, the sensing optical fiber 111 can be fixed to the side wall 201 of the battery cell 20 by means of a fixing member 1112. The fixing member 1112 can be pre-arranged on the side wall 201 of the battery cell 20 or pre-arranged on the sensing optical fiber 111. For example, during the production of the first optical fiber sensor 101, the fixing member 1112 can be pre-arranged on the sensing optical fiber 111 at the position corresponding to the fixing point 1110. In application, it can be fixed to the side wall 201 of the battery cell 20 using the fixing member 1112, which simplifies the assembly process between the sensing optical fiber 111 and the battery cell 20. For example, the fixing member 1112 can be a metal sheet, which can be easily fixed to the side wall of the battery cell 20 by welding. For example, during the production of the battery cell 20, a fastener 1112 can be pre-arranged on the side wall 201 of the battery cell 20. For example, the fastener 1112 can be a snap fastener. In application, the sensing fiber 111 can be snapped into the snap fastener 1112. This also helps to simplify the assembly process between the sensing fiber 111 and the battery cell 20.

[0102] For any of the aforementioned battery packs, the grating 112 of the first fiber optic sensor 101 and the optional second fiber optic sensor 102 can be exposed. However, considering that the exposed grating 112 is relatively fragile and easily broken, the battery pack also includes a support member 15. The support member 15 is fixedly connected to the side wall of the cell 20 and supports the grating 112, thus protecting the grating 112.

[0103] For the grating 112 formed on the sensing fiber 111 in a taut state, the corresponding support 15 can be made of strain material. For example, the first type of support 15 based on strain material is sheet-like and can be called a strain gauge. The first type of support 15 spans the gap 21 and its two ends are attached and fixed to the wall of the cell 20 (e.g., by bonding or welding). The grating 112 is attached to the surface of the first type of support 15 or embedded in the receiving groove provided on the first type of support 15.

[0104] In some examples, the first type of support 15 is a metal strain gauge made of metals such as copper, steel, or aluminum, which can provide stable mechanical protection for the grating 112. To prevent the strain gauge from masking the stress signal, the thickness of the strain gauge can be made as small as possible; for example, the thickness of the strain gauge can be less than 1 mm.

[0105] For the grating 112 formed on the sensing fiber 111 in a relaxed state, which is used to measure a single temperature information, a support 15 based on a high thermal conductivity material can be used to encapsulate it in a sensitizing manner, which can effectively improve the temperature sensitivity of the grating 112.

[0106] For example, the second type of support 15 based on a high thermal conductivity material is capillary-shaped and can be called a capillary. The capillary can be made of a high thermal conductivity metal, such as aluminum. The second type of support 15 is welded or bonded to the housing of the cell 20 and the capillary is sleeved on the outside of the corresponding relaxed grating 112. The Bragg fiber can be arranged coaxially with the second type of support 15. In this way, the second type of support 15 can protect the relaxed grating 112 from mechanical damage. At the same time, the high thermal conductivity of the second type of support 15 will not affect the temperature monitoring of the relaxed grating 112. On the contrary, it will enhance the temperature sensitivity of the grating 112.

[0107] Furthermore, a fixing material, such as epoxy resin, can be filled in the gap between the second type of support tube 15 and the grating 112 to enhance the stress shielding and protection effect on the relaxed grating 112.

[0108] For any of the aforementioned battery packs, the stress and temperature information of the battery cell 20 measured by the grating 112 in the first fiber optic sensor 101 and the optional second fiber optic sensor 102 is actually achieved by the grating 112 responding to the stress and temperature changes of the battery cell 20 and outputting corresponding stress change information (i.e., expansion force change information) and temperature change information, which are output in the form of wavelength signals. The fiber optic demodulator 13 demodulates the wavelength signal from the sensing fiber 111, and demodulates the drift of each reflection peak of the corresponding grating 112 based on the position of each grating 112, and outputs an electrical signal for analyzing the expansion state of the battery cell 20 monitored by each grating 112. Furthermore, this electrical signal can also be processed (e.g., calibrated in conjunction with the initial state of the battery cell 20) to obtain the actual expansion force and temperature values ​​of the battery cell 20 monitored by each grating 112, and used to analyze the expansion state of the battery cell 20.

[0109] In this embodiment, the stress and temperature information measured by the grating 112 are the stress and temperature information of the cells 20 on both sides of the gap 21 between adjacent fixed points 1110. Specifically, it is the relative stress change value and the relative temperature change value of the two cells 20 on both sides of the gap 21, and the overall expansion state of the current battery pack can be inferred from this. When the multiple gaps 21 formed by multiple cells 20 are all covered by the grating 112, that is, the stress and temperature information of each cell 20 are measured by two gratings 112 at the same time, the stress and temperature information of each cell 20 can be calculated from this.

[0110] In this embodiment of the disclosure, the laser emitter 12 and the fiber demodulator 13 can be integrated (e.g., Figures 1-12 Examples of laser transmitter 12 integrated into fiber demodulator 13 are provided, or laser transmitter 12 and fiber demodulator 13 may be arranged independently.

[0111] When the laser emitter 12 and the fiber optic demodulator 13 are integrated, a laser emission and demodulation device can be formed (see [reference]). Figures 1-12 This allows one end of the sensing fiber 111 to be connected to the laser emission and demodulation equipment, while the other end of the sensing fiber 111 can be freely arranged.

[0112] When the laser transmitter 12 and the fiber demodulator 13 are arranged independently, one end of the sensing fiber 111 can be connected to the laser transmitter 12, and the other end of the sensing fiber 111 can be connected to the fiber demodulator 13.

[0113] Furthermore, the fiber optic demodulator 13 can be further integrated into the battery pack or other components of the energy storage system in which the battery pack is located, such as the wall of the cell 20, the end plates on the outside of multiple cells 20, the battery management unit (BMU), the battery control unit (BCU), or the battery management system (BMS).

[0114] When there are multiple first fiber optic sensors 101 and multiple optional second fiber optic sensors 102, they can share a laser transmitter 12 and a fiber optic demodulator 13. In this way, the wavelength signals output by multiple first fiber optic sensors 101 can be demodulated using a single fiber optic demodulator 13, which significantly reduces demodulation costs.

[0115] In this embodiment of the disclosure, the multiple battery cells 20 arranged in a row mentioned above are defined as a battery cell assembly unit 200, and each battery cell assembly unit 200 is provided with one or more first fiber optic sensors 101. Figures 1-9 Examples of the battery packs include a cell assembly unit 200 and each cell assembly unit 200 is provided with a first fiber optic sensor 101.

[0116] As attached Figure 10 and attached Figure 11 As shown, the battery pack may include multiple cell assembly units 200, which are arranged in a row along another direction. The sidewalls 201 of the cells 20 of any two adjacent cell assembly units 200 are arranged opposite each other. One or more first fiber optic sensors 101 may be arranged in each cell assembly unit 200, thereby increasing the number of first fiber optic sensors 101 in this type of battery pack.

[0117] When there are multiple first fiber optic sensors 101, at least some of the multiple first fiber optic sensors 101 can be connected in series or in parallel.

[0118] For example, Figure 10 For example, a first fiber optic sensor 101 is provided for each cell assembly unit 200, and all the first fiber optic sensors 101 are connected in series. Any two adjacent first fiber optic sensors 101 are connected in series through a connecting fiber optic cable 14 (for example, by means of fusion splicing). Furthermore, these first fiber optic sensors 101 are connected to the same laser emitter 12 and the same fiber optic demodulator 13.

[0119] The position of the connecting optical fiber 14 among the multiple battery cells 20 is designed to minimize bending, for example... Figure 10 The example shows that the first fiber optic sensor 101 and the connecting fiber 14 are both arranged at the top end plate position of the plurality of cells 20, so that the connecting fiber 14 avoids bending and avoids going around the large surface of the cell 20.

[0120] Figure 11 For example, a first fiber optic sensor 101 is provided for each cell assembly unit 200, and all the first fiber optic sensors 101 are connected in parallel. Furthermore, these multiple first fiber optic sensors 101 are connected to the same laser transmitter 12 and the same fiber optic demodulator 13.

[0121] The cell assembly unit 200, in which multiple cells 20 are located, is typically provided with signal cables, such as signal cables for a cell contact system (CCS), for signal transmission between cells 20. In some examples, a first fiber optic sensor 101 can be integrated into the signal cable, which not only simplifies the structural layout of the cell assembly unit 200, but also enables more accurate real-time measurement of the temperature of the signal cable.

[0122] The cell assembly unit 200, in which multiple cells 20 are located, is also typically provided with binding straps, such as steel cable ties, to bind the multiple cells 20 together for positioning. In some examples, the first fiber optic sensor 101 can also be integrated into the binding straps to simplify the structural layout of the cell assembly unit 200.

[0123] The accompanying drawings of the embodiments disclosed herein illustrate battery packs composed of square cells 20. Based on the same principle, as shown in the attached drawings... Figure 12 As shown, for a battery pack composed of cylindrical cells 20, the first fiber optic sensor 101 can still be arranged around the stacking direction of multiple cylindrical cells 20 (e.g., in a ring or S-shape), while the grating 112 covers the gap 21, thus enabling stress monitoring.

[0124] For any of the aforementioned battery packs, it further includes a battery management unit (BMU). In some examples, the BMU is used to calculate the deformation state of the battery pack based on stress and temperature data of at least a portion of the cells 20 measured by a first fiber optic sensor and an optional second fiber optic sensor, wherein the deformation state of the battery pack may be an expansion state.

[0125] In this example, both the fiber optic demodulator 13 and the laser emitter 12 are connected to the battery management unit (BMU). The BMU determines the deformation state of at least some of the multiple cells 20 based on the stress and temperature data of at least some of the cells 20 output by the fiber optic demodulator 13, and thereby obtains the deformation state of the battery pack in which the multiple cells 20 are located.

[0126] In some examples, the battery management unit (BMU) determines whether the expansion state of the battery pack is a high-risk state for thermal runaway by judging whether the expansion force or the rate of increase of expansion force of at least some of the multiple cells 20 exceeds a corresponding threshold. If there is data exceeding the threshold, the expansion state of the battery pack is considered to be a high-risk state for thermal runaway.

[0127] For cell 20, it may also experience a certain degree of expansion during normal operation. Therefore, to improve the accuracy of thermal runaway risk prediction, an expansion force threshold can be set based on the current operating state of cell 20. For example, the expansion force threshold can be set as follows: when cell 20 is in a normal charging state and discharging state, the expansion force of the cell casing is measured respectively to obtain the maximum expansion force of the cell casing when charging and the maximum expansion force of the cell casing when discharging, and the larger of these two maximum expansion forces is determined as the expansion force threshold.

[0128] It should be noted that the normal expansion of cell 20 is divided into reversible expansion (charge and discharge breathing expansion) and irreversible expansion (aging expansion). Therefore, the threshold of this expansion force can change throughout the entire battery life cycle. Thus, the expansion force threshold may be set by combining the change pattern of cell 20 in the last 10 cycles and making real-time corrections to the expansion force threshold.

[0129] On the other hand, this disclosure also provides an energy storage device, which includes: a power converter and at least one battery pack as described above; the at least one battery pack is connected in series to output to the power converter or connected in parallel to output to the power converter; the power converter is used to perform power conversion on the voltage output by the at least one battery pack.

[0130] The energy storage device provided in this disclosure has all the advantages of the battery pack mentioned above, which will not be repeated here.

[0131] In some examples, the energy storage device further includes a battery control unit, which is configured to receive battery pack deformation state information output by the battery management unit of the battery pack, and to control at least one battery pack based on the deformation state information of each battery pack in at least one battery pack.

[0132] For example, when the battery pack's deformation status information output by the battery management unit indicates that the battery pack is in a high-risk state of thermal runaway or a high-risk state of structure, the battery control unit can control the battery pack to cut off power or issue an alarm signal.

[0133] Taking lithium-ion batteries as an example, the frequent delithiation and insertion of lithium cause the expansion state of the battery cells to change periodically. This periodic expansion change of the cell can reflect both the battery's State of Charge (SOC) and its State of Health (SOH). This is because, as lithium-ion batteries age, the cells will expand to a certain extent.

[0134] Based on this, the energy storage device may further include a calibration module, which is used to calibrate at least one of the following states of the battery pack based on the stress inflection point data of the battery pack: State of Charge (SOC), State of Energy (SOE), State of Health (SOH), State of Power (SOP), and State of Temperature (SOT); wherein the stress inflection point data of the battery pack is measured by the first fiber optic sensor 101 of the battery pack. This enables accurate prediction of the battery pack's state and ensures its operational reliability.

[0135] For example, the calibration module is used to calibrate the State of Charge (SOC) of the battery pack based on the stress inflection point data. This is because, for lithium-ion batteries, the positive and negative electrode active materials exhibit periodic expansion force changes during the lithium insertion-deintercalation reaction during charging and discharging. Taking the lithium iron phosphate-graphite system cell 20 as an example, its voltage plateau is relatively flat, making SOC calibration difficult. Research has found that during charging, the reversible expansion force exhibits a characteristic trend of first rising, then falling, and then rising again. There is a first inflection point when the expansion force changes from rising to falling, and a second inflection point when it changes from falling to rising. These two inflection points can be called breathing expansion characteristic inflection points, which correspond to the phase transition sites of the negative electrode material and are strongly correlated with the battery's State of Charge (SOC). The first inflection point corresponds to approximately 30% SOC, and the second inflection point corresponds to approximately 60% SOC, and the SOC corresponding to these two inflection points remains almost unchanged as the cell ages. By collecting the inflection point of the breathing expansion characteristic, the SOC estimation algorithm can be effectively optimized and used as the input for SOC calibration. This solves the problem that the voltage platform of lithium iron phosphate-graphite system batteries is relatively flat and it is difficult to evaluate SOC through voltage.

[0136] The calibration module mentioned above can be integrated into the battery management unit (BMU) or the battery management system (BMS), depending on the actual needs.

[0137] Furthermore, this disclosure also provides a battery deformation state monitoring device, which includes any of the battery packs mentioned above.

[0138] The battery deformation state monitoring device provided in this disclosure has all the advantages of the battery pack mentioned above, and will not be repeated here.

[0139] Furthermore, this disclosure also provides a battery deformation state monitoring method, which is applied to any of the aforementioned battery packs or battery deformation state monitoring devices. The battery deformation state monitoring method includes:

[0140] The grating 112 of the first fiber optic sensor 101 receives laser pulse signals from the laser emitter 12 and outputs a wavelength signal, which is used to indicate stress and temperature information of at least some of the multiple cells 20.

[0141] The wavelength signal is demodulated by the fiber optic demodulator 13 to obtain stress and temperature information of at least some of the multiple battery cells 20.

[0142] Based on the stress and temperature information of at least some of the multiple battery cells 20, the deformation state of at least some of the battery cells 20 and the deformation state of the battery pack in which they are located are obtained.

[0143] The battery deformation state monitoring method provided in this disclosure, by acquiring the deformation state of at least some of the cells 20 and the battery pack they belong to, can not only provide early warning of structural risks and thermal runaway risks of multiple cells 20, but also capture the inflection point of breathing expansion characteristics through subsequent algorithms, serving as an important input for SOC calibration, and calibrating various structural and life-related models of the battery pack. Furthermore, it possesses high monitoring sensitivity and accuracy.

[0144] In some examples, battery deformation state monitoring methods also include:

[0145] A grating 112 formed on a tensioned sensing fiber 111 receives laser pulse signals from a laser emitter 12 and outputs a first wavelength signal; and a grating 112 formed on a relaxed sensing fiber 111 receives laser pulse signals from a laser emitter 12 and outputs a second wavelength signal. The first wavelength signal is demodulated by an fiber optic demodulator 13 to obtain composite information of stress and temperature information for at least a portion of the plurality of battery cells 20. The second wavelength signal is also demodulated by the fiber optic demodulator 13 to obtain temperature information for at least a portion of the plurality of battery cells 20. The temperature information is removed from the composite information to obtain stress information for at least a portion of the plurality of battery cells 20.

[0146] This battery deformation state monitoring method can obtain single stress information, and is more intuitive for monitoring the deformation state of multiple cells 20 and the battery pack.

[0147] The above description is only for the purpose of enabling those skilled in the art to understand the technical solutions disclosed herein, and is not intended to limit the scope of this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A battery pack, characterized in that, The battery pack includes: a plurality of battery cells (20) arranged in a row and a first fiber optic sensor (101); The first optical fiber sensor (101) includes: a sensing optical fiber (111) and a plurality of gratings (112) formed on the sensing optical fiber (111), wherein the plurality of gratings (112) are spaced apart along the extension direction of the sensing optical fiber (111); Along the arrangement direction of the plurality of battery cells (20), the sensing optical fiber (111) is fixed to the sidewall of at least a portion of the battery cells (20). The sensing optical fiber (111) has a grating (112) between two adjacent fixing points (1110) of the plurality of fixing points (1110) of the at least a portion of the battery cells (20). There is a gap (21) between two adjacent battery cells (20) arranged in the plurality of battery cells (20) on two opposite surfaces in the arrangement direction. At least a portion of the gaps (21) are at least partially covered by the grating (112).

2. The battery pack according to claim 1, characterized in that, The slit (21) is completely covered by at least a portion of the grating (112).

3. The battery pack according to claim 1, characterized in that, The tension of the sensing fiber (111) located between the fixed points (1110) and along the slit (21) is greater than 0.

4. The battery pack according to claim 1, characterized in that, The tension of the sensing fiber (111) located between the fixed points (1110) and along the gap (21) is 0.5N-1.5N.

5. The battery pack according to any one of claims 1-4, characterized in that, Along the arrangement direction of the plurality of cells (20), at least two adjacent fixing points (1110) of the plurality of fixing points (1110) have the gap (21) between them, and the number of gaps (21) between the at least two adjacent fixing points (1110) is one or more. When there are multiple gaps (21) between two at least partially adjacent fixed points (1110), at least a portion of the gaps (21) are covered by the grating (112).

6. The battery pack according to claim 5, characterized in that, The sensing optical fiber (111) is fixed to each of the plurality of battery cells (20). There is a gap (21) between the sensing optical fiber (111) and the fixing point (1110) of any two adjacent battery cells (20). Each gap (21) is covered by the grating (112).

7. The battery pack according to any one of claims 1-6, characterized in that, In the first optical fiber sensor (101), part of the sensing optical fiber (111) fixed to the wall of the plurality of cells (20) is in a tensioned state and the other part is in a relaxed state, wherein the tensioned state is when the tension of the sensing optical fiber (111) is greater than 0, and the relaxed state is when the tension of the sensing optical fiber (111) is equal to 0. A grating (112) formed on the sensing fiber (111) under tension is used to measure stress and temperature; A grating (112) formed on the sensing fiber (111) in the relaxed state is used to measure temperature.

8. The battery pack according to claim 7, characterized in that, The plurality of gratings (112) all cover the corresponding gaps (21), and some of the gratings (112) are formed on the tensioned sensing fiber (111), while the remaining gratings (112) are formed on the relaxed sensing fiber (111).

9. The battery pack according to claim 7, characterized in that, A portion of the plurality of gratings (112) covers the corresponding slits (21) and is formed on the tensioned sensing fiber (111); The remaining portion of the plurality of gratings (112) covers the wall of the cell (20) and is formed on the relaxed sensing fiber (111), the two fixed points (1110) corresponding to the relaxed sensing fiber (111) being located on the same wall of the cell (20).

10. The battery pack according to any one of claims 1-6, characterized in that, The sensing fiber (111) in the first fiber optic sensor (101) is fixed to the side wall of the plurality of battery cells (20) and is in a tensioned state. The first fiber optic sensor (101) is used to measure stress and temperature. The tension state refers to the tension of the sensing optical fiber (111) being greater than 0.

11. The battery pack according to claim 10, characterized in that, The battery pack further includes a second optical fiber sensor (102), which includes a sensing optical fiber (111) and a plurality of gratings (112) formed on the sensing optical fiber (111), wherein the plurality of gratings (112) are spaced apart along the extension direction of the sensing optical fiber (111). The sensing fiber (111) of the second fiber optic sensor (102) is fixed to the sidewall of the two outermost cells (20) of the plurality of cells (20) and is in a relaxed state, wherein the relaxed state means that the tension of the sensing fiber (111) is equal to 0; the positions of the plurality of gratings (112) of the fiber optic sensor (102) correspond one-to-one with the positions of the plurality of gratings (112) of the fiber optic sensor (101), so that the second fiber optic sensor (102) is used to measure temperature.

12. The battery pack according to any one of claims 1-11, characterized in that, The sensing optical fiber (111) is fixed to the side wall of the battery cell (20) by a fastener (1112).

13. The battery pack according to any one of claims 1-12, characterized in that, The battery pack further includes a support member (15), which is fixedly connected to the side wall of the battery cell (20) and supports the grating (112).

14. The battery pack according to any one of claims 1-13, characterized in that, Signal cables and cable ties are provided on the plurality of battery cells (20), and the first fiber optic sensor (101) is integrated into at least one of the signal cables and the cable ties.

15. The battery pack according to any one of claims 1-14, characterized in that, The battery pack also includes a battery management unit, which is used to calculate the deformation state of the battery pack based on the stress and temperature data of the battery pack measured by the first fiber optic sensor (101) or the second fiber optic sensor (102).

16. An energy storage device, characterized in that, The energy storage device includes: a power converter and at least one battery pack as described in any one of claims 1-15; the at least one battery pack is connected in series to output to the power converter or connected in parallel to output to the power converter; The power converter is used to perform power conversion on the voltage output by the at least one battery pack.

17. The energy storage device according to claim 16, characterized in that, The energy storage device further includes a battery control unit, which is used to receive battery pack deformation state information output by the battery management unit of the battery pack, and to control the at least one battery pack according to the deformation state information of each battery pack in the at least one battery pack.

18. The energy storage device according to claim 16, characterized in that, The energy storage device further includes a calibration module, which is used to calibrate at least one of the following states of the battery pack based on the stress inflection point data of the battery pack: state of charge, state of energy, state of health, state of power, and temperature state. The stress inflection point data of the battery pack is obtained by measuring the first fiber optic sensor (101) of the battery pack.

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