An optical fiber distributed lithium battery and its manufacturing process

Abstract

The present invention relates to a fiber optic distributed lithium battery and its manufacturing process. The lithium battery includes an internal measurement mechanism, a battery cell, electrode tabs, and an aluminum-plastic film; the internal measurement mechanism is located inside the battery cell, the electrode tabs include a positive electrode tab and a negative electrode tab, which are respectively welded to the positive and negative electrodes of the battery cell, and the aluminum-plastic film is wrapped outside the lithium battery. The manufacturing process includes the following steps: obtaining positive and negative electrode plates, and a porous lattice structure, inserting optical fibers into the porous lattice structure to form an internal measurement mechanism; inserting the internal measurement mechanism between the positive and negative electrode plates, and stacking the positive and negative electrode plates to form a battery cell; compared with the prior art, the present invention has the advantages of high reliability, strong accuracy, distributed measurement, compact structure, low cost, etc., and is of great significance for battery management based on the internal temperature distribution information of the battery.

Description

Technical Field

[0001] The present invention relates to the field of battery manufacturing and management, and particularly to an optical fiber distributed lithium battery and its manufacturing process. Background Art

[0002] With the global emphasis on clean energy and the adjustment of the social energy structure, lithium-ion batteries are widely used in energy storage, electric vehicles, consumer electronics, and transportation fields due to their high energy density, high Coulomb efficiency, long cycle life, and other advantages.

[0003] Currently, the perception of the internal state of lithium-ion batteries is a problem that the battery management system in the industry must face. Traditional battery management systems (BMS) mostly rely on limited information such as battery terminal voltage, current, and external temperature to estimate the internal state of the battery, which will cause problems such as inaccurate battery state estimation, lag in information acquisition, and long estimation time. Therefore, how to obtain the internal state information of the battery without affecting the battery performance is the key point and difficulty in the current development of lithium batteries.

[0004] Currently, soft-pack batteries are gradually becoming an important development direction for vehicle-mounted power batteries. They are mainly prepared by the stacking and winding methods. To ensure good contact between the electrodes, the internal electrode sheets of soft-pack batteries must be flat, and there needs to be electrolyte infiltration and good adhesion between the electrode sheets. This brings difficulties to implanting sensors inside the battery, especially for obtaining key information such as the internal temperature distribution of the battery.

[0005] At the same time, when current power batteries are used in vehicles, issues such as energy density and high-rate charge and discharge need to be considered. Rapid charge and discharge of large-capacity batteries under high-rate conditions will cause problems such as rapid temperature change and uneven distribution of the battery. How to implant sensors and accurately obtain the internal information of the battery without affecting the battery energy density is the current research focus. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide an optical fiber distributed lithium battery and its manufacturing process, which can solve the problems of performance loss of lithium-ion batteries caused by traditional direct sensor implantation methods and the inability to distributedly measure the internal temperature of the battery.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The internal measurement unit of the present invention is partially encapsulated inside the battery, and the internal signal is transmitted to the outside of the battery through an optical fiber. The measurement structure does not affect the sealing performance of the battery after encapsulation. Thus, the battery with the function of distributed internal temperature measurement includes a porous lattice structure and an optical fiber. The optical fiber is externally connected to a broadband light source, a spectral demodulator, an optical circulator, and a host computer. The specific solution is as follows:

[0009] An optical fiber distributed lithium battery, which includes an internal measurement mechanism, battery cells, electrode tabs, and an aluminum-plastic film; the internal measurement mechanism is located inside the battery cells, the electrode tabs include a positive electrode tab and a negative electrode tab, which are respectively welded to the positive and negative electrodes of the battery cells, and the aluminum-plastic film wraps around the outside of the lithium battery.

[0010] Furthermore, the internal measurement mechanism includes a porous lattice structure and optical fibers interspersed in the porous lattice structure.

[0011] The optical fibers are interspersed in the porous lattice structure three-dimensionally printed using a light-curing technique according to a specific serpentine path. The output end of the optical fiber is connected to an optical circulator, and the optical circulator serves as a conversion device between a broadband light source and a spectral decoupling device, and is simultaneously connected to the broadband light source and a spectral demodulator. Among them, the broadband light source provides a light source with a specific wavelength for measurement. Under the influence of the internal temperature of the battery, the grating pitch inside the optical fiber undergoes displacement, thereby changing the wavelength of the light wave reflected by the grating. By measuring and decoupling the optical wave information, the spectrometer can obtain the internal temperature information of the battery and transmit the decoupled signal to the host computer.

[0012] The optical fibers are implanted in the porous lattice structure. The porous lattice structure adopts a porous structure, and photosensitive resin is processed using a light-curing technique, which can achieve high porosity, high mechanical strength, and precise dimensional processing, enabling the measurement device to be immersed in the electrolyte, enabling the optical fibers to decouple the mechanical action and temperature influence, and not affecting the normal operation of the lithium battery at the same time.

[0013] Furthermore, multiple Bragg gratings (FBGs) are etched in the optical fibers. Thus, the temperature information at different positions can be measured using multiple gratings. Through the spectral demodulator, the decoupled signal is transmitted to the computer, and the wavelength of the light and the temperature information at different positions can be directly read in specific software, and the temperature at different positions and the data of the temperature change over time are recorded and saved.

[0014] Furthermore, the pore diameter in the porous lattice structure is slightly larger than the diameter of the optical fiber. The porous lattice structure has electrical conductivity insulation and mechanical strength, which can ensure that the battery does not have an internal short circuit during operation. At the same time, the pore diameter in the porous structure is slightly larger than the diameter of the optical fiber, ensuring that the optical fiber is not affected by the battery stacking stress while ensuring a lightweight design. The pores in the porous structure form countless microchannels, which can ensure the normal transmission of the electrolyte.

[0015] Furthermore, the material of the porous lattice structure includes nylon, high-temperature resistant resin, or ceramic.

[0016] A manufacturing process for the optical fiber distributed lithium battery as described above, which process includes the following steps:

[0017] Obtain the positive and negative electrode plates, as well as the porous lattice structure, insert the optical fiber into the porous lattice structure to form an internal measurement mechanism;

[0018] Insert the internal measurement mechanism between the positive and negative electrode plates, and stack the positive and negative electrode plates to form an electrode core;

[0019] Weld the positive electrode tab (aluminum tab) and the negative electrode tab (nickel tab) to the positive and negative electrodes of the electrode core respectively, then place the electrode core into an aluminum-plastic film casing, and use a heat sealer to seal the tab side and the area below the tab of the electrode core, leaving an open side in a state of being connected to the outside; wherein, both ends of the optical fiber are connected to external devices after being heat-sealed by the aluminum-plastic film; to ensure the battery's sealing performance, the length of the lead wire at the aluminum-plastic film sealing position is not less than 6 millimeters;

[0020] Dry the battery, and after cooling, inject an electrolyte matching the capacity of the electrode core into the soft-pack battery packaging bag under a negative pressure environment;

[0021] Perform vacuum pumping and primary sealing to obtain an optical fiber distributed lithium battery; then subject the battery to formation and grading, and then perform secondary vacuum pumping and sealing to complete all the manufacturing processes of the optical fiber distributed lithium battery.

[0022] Furthermore, the manufacturing method of the porous lattice structure is: import the data of the three-dimensional model into a micro-scale 3D printer, and use surface projection micro-stereolithography technology to etch and solidify the three-dimensional model layer by layer to complete the precision manufacturing of the porous lattice structure.

[0023] Furthermore, the lithium battery is a stacked soft-pack battery or a wound soft-pack battery.

[0024] Furthermore, the lithium battery is a stacked soft-pack battery, and the number of negative electrode plates is one more layer than the number of positive electrode plates. The preparation steps of the electrode core are: stack the positive electrode plate, the separator, and the negative electrode plate in sequence; insert the internal measurement mechanism between the positive electrode plate and the negative electrode plate, and ensure that the porous structure is aligned with the electrode plate and has an appropriate edge distance from the electrode plate; stack the positive and negative electrode plates in a concentric and diagonal alignment manner with the center, and stack the separator in a Z shape to obtain the electrode core body of the stacked soft-pack battery.

[0025] Furthermore, the lithium battery is a wound soft-pack battery, and the porous lattice structure is placed in the middle of the winding core during manufacturing.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention first proposes a design scheme and a measuring device for the internal structure of a lithium battery based on fiber optic distributed measurement. The device implants a porous structure formed by additive manufacturing with an inserted optical fiber into the positive and negative electrode plates of a soft-pack battery. Through multiple gratings in the optical fiber, signals can be transmitted to the outside of the battery in real time through the optical fiber, thereby obtaining the temperature distribution information inside the battery;

[0028] (2) In the present invention, the design of the porous structure and the implantation of the optical fiber do not affect the infiltration of the electrolyte inside the battery and the lithium ion transmission. At the same time, the insertion of the porous structure does not affect the active materials on the electrode plate, and the overall thickness is similar to that of a single electrode plate, so as to ensure the measurement accuracy without affecting the performance and energy density of the battery;

[0029] (3) In the present invention, both the optical fiber and the porous structure have insulation and corrosion resistance. When implanted into the battery, they can ensure the working stability without causing a short circuit inside the battery. At the same time, the gratings etched at multiple places in the optical fiber can measure the temperatures at multiple points inside the battery with a single optical fiber, thus efficiently realizing distributed measurement. By measuring the temperature inside the battery in real time, the internal state of the battery can be effectively monitored, and the thermal runaway caused by high-rate charge and discharge, high and low temperature environments, aging, and extreme conditions of the lithium battery can be quickly monitored and managed;

[0030] (4) In the present invention, the optical fiber and the porous structure are fabricated by additive manufacturing, so the manufacturing accuracy can be guaranteed and there is potential for large-scale production. When winding / stacking the battery electrode plates, the porous structure can be implanted through simple positioning, and there is no additional device requirement for the existing battery production line. Therefore, it is very suitable for industrial production. By implanting a porous structure containing an optical fiber inside the battery, the decoupling analysis of temperature and stress on the optical fiber signal can be realized, greatly simplifying the signal analysis process and enhancing the accuracy of battery management;

[0031] (5) In the present invention, for a battery pack composed of multiple batteries, a single optical fiber can be used to connect multiple batteries in series to simultaneously monitor the temperature signals of multiple single batteries inside the battery pack, which will improve the monitoring and management of the battery management system for the temperature inconsistency and single cell anomalies of the single batteries inside the battery module. Description of the Drawings

[0032] Figure 1 is the external view of the fiber optic distributed lithium battery in the present invention;

[0033] Figure 2 is the schematic internal structure diagram of the fiber optic distributed lithium battery in the present invention;

[0034] Figure 3 is the schematic assembly diagram of the optical fiber and the porous lattice structure in the present invention;

[0035] Figure 4 This is a partially enlarged schematic diagram of the assembly gap between the optical fiber and the porous lattice structure in the present invention. Specific Embodiments

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art can understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection required by the present invention is defined by the scope defined in the claims.

[0037] A method for designing the internal structure of a lithium battery based on distributed optical fiber measurement, in which the internal porous structure is fabricated by additive manufacturing, includes the following steps:

[0038] (1) Design the capacity of the soft-pack battery to determine the number of positive and negative electrode plates and the specific number of layers inserted into the porous structure. By measuring the diameter of the optical fiber and the size of the electrode plates of the soft-pack battery, determine the diameter of the rods of the porous structure, the pore size, and the three-dimensional size of the outer shape.

[0039] (2) Cut the rolled electrode plates by a die cutter to obtain positive and negative electrode plates of fixed size. Among them, when using a laminated soft-pack battery, the number of negative electrode plates is one more layer than the number of positive electrode plates.

[0040] (3) Design a porous lattice structure by three-dimensional design software, where the pore size of this structure needs to be larger than the diameter of the optical fiber, and the rod diameter is related to the stacking pressure and assembly pressure of the soft-pack battery. By importing the data of the three-dimensional model into a micro-scale 3D printer, use the surface projection micro-stereolithography technology to layer-etch and solidify the three-dimensional model to complete the precision manufacturing of the porous lattice structure. The manufacturing raw materials of this porous structure can be selected from materials such as nylon, high-temperature resistant resin, and ceramics.

[0041] (4) Stack the positive electrode plate, separator, and negative electrode plate in the specified order, insert a porous lattice structure containing an optical fiber between the positive and negative electrode plates in the specified order, and ensure that the porous structure is aligned with the electrode plates and has an appropriate distance from the edges of the electrode plates to obtain the main body of the battery cell.

[0042] (5) Bind the battery cell with a special tape, and weld the aluminum electrode tab and nickel electrode tab to the positive and negative electrodes of the battery cell.

[0043] (6) Stamp the aluminum-plastic film with an aluminum-plastic film forming machine to obtain an aluminum-plastic film shell that matches the set battery capacity. Place the battery cell into the aluminum-plastic film shell, and use a heat sealer to seal one side and the tab side of the battery cell and the aluminum-plastic film, leaving an open side in communication with the outside. Among them, both ends of the optical fiber are connected to external devices after being heat-sealed through the aluminum-plastic film. To ensure the battery's sealing performance, the length of the optical fiber at the aluminum-plastic film sealing position is not less than 6 millimeters.

[0044] (7) Dry the battery cell in a high-temperature oven. Inject electrolyte that matches the battery cell capacity into the soft-pack battery packaging bag under a negative pressure environment.

[0045] (8) Perform vacuum pumping and primary sealing to obtain a lithium battery based on fiber optic distributed measurement. Subject the battery to formation and grading, and then perform secondary vacuum pumping and sealing to complete the production.

[0046] As Figure 1 shown, this embodiment provides an aluminum-plastic film packaged soft-pack battery for measuring the internal temperature of a battery based on fiber optic distribution. The porous structure and part of the optical fiber are encapsulated inside the battery and are only connected to the outside through the optical fiber. One end of the optical fiber is connected to a special end cap, and the other end is connected to equipment such as a spectral analyzer. The optical fiber and the battery are sealed on both sides by heat-sealing with an aluminum-plastic film.

[0047] The connection and assembly method of the porous structure, the electrode plate, and the optical fiber of the soft-pack battery are as Figure 2 shown. The optical fiber is inserted through the porous structure in a serpentine manner, and both ends of the optical fiber are distributed on the upper and lower sides of the battery. The porous structure is located between the positive / negative electrode plates and the separator. The design of the porous structure provides numerous flow channels for the electrolyte. The design of the regular hexahedron prism lattice structure ensures the mechanical strength and flatness of the structure to ensure the flatness and good alignment between the positive and negative electrode plates. As Figure 3 and 4 shown, the pore size of the porous structure is slightly larger than the diameter of the optical fiber, which can ensure that the optical fiber has a certain displacement space inside the porous structure, avoid signal interference of the optical fiber caused by pressure, and achieve decoupling of the signal for measuring the temperature of the optical fiber and the signal affected by pressure. From Figure 4It can be seen that the thickness of the porous structure is close to that of the electrode sheet, which ensures that the energy density of the battery after implanting the porous structure will not change significantly. Furthermore, since the porous structure adopts the light-curing additive manufacturing technology, it can be designed into other free-form surfaces to adapt to future shaped batteries and flexible batteries. When the battery is working, the internal temperature of the battery will change. By injecting an optical signal with a specific wavelength into the optical fiber through a light source, under the influence of temperature, the grating pitch changes, resulting in a change in the wavelength of the reflected light in the optical fiber. The optical signal is demodulated by a spectral analyzer, and the relevant data is transmitted to the host computer, thereby obtaining the information on the change in the internal temperature of the battery. By connecting the optical fibers in series inside different batteries, the internal temperature monitoring of multiple battery cells can be realized, and the estimation and performance management of other related characteristics (such as state of charge, state of health, etc.) can be achieved. Therefore, this design scheme can be easily migrated to the internal temperature monitoring of multiple battery cells in a battery pack / module and the estimation and performance management of other related characteristics (such as state of charge, state of health, etc.).

[0048] Example 1

[0049] This example is a laminated battery. The process of preparing the battery cell is as follows: stack the positive electrode sheet, separator, and negative electrode sheet in sequence; insert the internal measurement mechanism between the positive electrode sheet and the negative electrode sheet, and ensure that the porous structure is aligned with the electrode sheet and the distance from the edge of the electrode sheet is appropriate; stack the positive and negative electrode sheets in a way that the centers are coaxial and the diagonals are aligned, and the separator is stacked in a Z shape to obtain the main body of the laminated soft-pack battery cell.

[0050] Example 2

[0051] This example is a wound battery. During the process of preparing the battery cell, it is necessary to pay attention to the appropriate distance between the upper and lower edges of the electrode sheet and the separator. When manufacturing, place the porous lattice structure in the middle of the bobbin. After all the battery cells are prepared, it should be ensured that the separator winds around the outside of the battery again for one week to completely wrap the battery cell.

[0052] In summary, the present invention is based on the structural design for non-destructively measuring the internal temperature of lithium batteries using distributed optical fibers. This structural design is mainly based on photocuring additive manufacturing technology and the technologies for assembling, injecting electrolyte, forming, and subsequent signal decoupling analysis of soft-pack lithium-ion batteries. The positive and negative electrodes of the present invention both adopt traditional manufacturing methods, that is, active materials are double-sided coated on a metal current collector, and a three-dimensional porous lattice structure prepared by photocuring technology is implanted inside the battery, and optical fibers are implanted in the porous lattice structure. By inserting the three-dimensional porous lattice structure with implanted optical fibers between the positive and negative electrodes inside the battery, the problems of pole piece bulge and stress concentration caused by traditional thin-film thermocouples and direct optical fiber implantation can be effectively solved, and the porous structure can ensure the full infiltration of the electrolyte and the transmission of lithium ions between the positive and negative electrodes; at the same time, with photocuring technology, its micron-level printing accuracy can effectively reduce the rod diameter of the porous structure, the overall thickness of the porous structure is close to that of a single battery pole piece, and its internal structure and the channels for placing optical fibers can be flexibly customized. Therefore, the implantation of this structure has a very weak impact on the energy density of the battery; finally, implanting the optical fibers inside the porous structure can effectively achieve signal decoupling, thereby distributedly measuring the internal temperature distribution of the battery and enabling the battery to operate without damage. Compared with the prior art, the present invention has the advantages of high reliability, strong accuracy, distributed measurement, compact structure, and low cost, and is of great significance for battery management based on the internal temperature distribution information of the battery.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other form. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A fiber optic distributed lithium battery, characterized in that, the lithium battery includes an internal measurement mechanism, battery cells, tabs and an aluminum-plastic film; the internal measurement mechanism is located inside the battery cells, the tabs include a positive tab and a negative tab, which are respectively welded to the positive and negative electrodes of the battery cells, and the aluminum-plastic film is wrapped outside the lithium battery; the internal measurement mechanism includes a porous lattice structure and optical fibers interspersed in the porous lattice structure; the porous lattice structure is a regular hexahedron prism lattice structure; the pore diameter in the porous lattice structure is larger than the diameter of the optical fiber.

2. A fiber optic distributed lithium battery according to claim 1, characterized in that, multiple Bragg gratings are etched in the optical fiber.

3. A fiber optic distributed lithium battery according to claim 1, characterized in that, the material of the porous lattice structure includes nylon, high-temperature resistant resin or ceramic.

4. A manufacturing process of a fiber optic distributed lithium battery as described in any one of claims 1-3, characterized in that, the process includes the following steps: Obtain positive and negative electrode plates, and a porous lattice structure, insert the optical fiber into the porous lattice structure to form an internal measurement mechanism; Insert the internal measurement mechanism between the positive and negative electrode plates, and stack the positive and negative electrode plates to form battery cells; Weld the positive tab and the negative tab to the positive and negative electrodes of the battery cells respectively, then place the battery cells into an aluminum-plastic film shell, and seal the tab side and below the tab of the battery cells with a heat sealer; wherein, both ends of the optical fiber are connected to external devices after being heat-sealed through the aluminum-plastic film; Dry the battery, and inject electrolyte matching the capacity of the battery cells into the soft-pack battery packaging bag under a negative pressure environment after cooling; Perform vacuum pumping and primary sealing to obtain a fiber optic distributed lithium battery; then subject the battery to formation and grading, and then perform secondary vacuum pumping and sealing to complete the entire manufacturing process of the fiber optic distributed lithium battery.

5. A manufacturing process of a fiber optic distributed lithium battery according to claim 4, characterized in that, the manufacturing method of the porous lattice structure is: import the data of the three-dimensional model into a micro-scale 3D printer, and use the surface projection micro-stereolithography technology to layer-etch and solidify the three-dimensional model to complete the precision manufacturing of the porous lattice structure.

6. A manufacturing process of a fiber optic distributed lithium battery according to claim 4, characterized in that, the lithium battery is a stacked soft-pack battery or a wound soft-pack battery.

7. A manufacturing process of a fiber optic distributed lithium battery according to claim 6, characterized in that, the lithium battery is a stacked soft-pack battery, the number of negative electrode plates is one layer more than the number of positive electrode plates, and the preparation steps of the battery cells are: stack the positive electrode plates, separators and negative electrode plates in sequence; insert the internal measurement mechanism between the positive and negative electrode plates; stack the positive and negative electrode plates in a concentric and diagonal alignment manner at the center, and stack the separators in a Z-shape to obtain the main body of the battery cells of the stacked soft-pack battery.

8. A manufacturing process of a fiber optic distributed lithium battery according to claim 6, characterized in that, the lithium battery is a wound soft-pack battery, and the porous lattice structure is placed in the middle of the winding core during manufacturing.

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