Sensor for in-situ detection of amount of free electrolyte in lithium battery and lithium battery

Abstract

The utility model relates to a sensor for detecting the amount of free electrolyte in a lithium battery in situ and the lithium battery. The sensor comprises an insulating shell, a conductive polymer electrode and two wires, the conductive polymer electrode is disposed on the insulating housing. One ends of the two wires are embedded in the insulating shell in a sealed mode and are electrically connected with different positions of the conductive polymer electrode respectively, and the other ends of the two wires are located outside the insulating shell. When the sensor provided by the utility model is used for detecting the amount of free electrolyte in the lithium battery in situ, the sensor is firstly implanted into the lithium battery, electrochemical balance can be established between the conductive polymer electrode and the electrolyte, and the charge distribution and the electrode potential on the surface of the conductive polymer electrode can be changed due to different concentrations of lithium salts; the change curve of the current of the conductive polymer electrode along with the potential is recorded in real time through the electrochemical workstation, and the loss condition of the solvent in the electrolyte is indirectly judged through the potential of the conductive polymer electrode and the change of the response current intensity.

Description

TECHNICAL FIELD

[0001] The utility model relates to lithium battery technical field especially relates to a sensor for in situ detection lithium battery internal free electrolyte amount and lithium battery. BACKGROUND

[0002] As the core energy component of modern electronic devices and electric vehicles, the performance and safety of lithium batteries directly affect the reliability and efficiency of the entire vehicle system. As a key component of lithium batteries, the state of electrolyte has a decisive influence on the working performance of lithium batteries. Leakage, excess or uneven distribution of electrolyte not only reduces the energy output efficiency of the battery, but also may cause the battery to overheat, even burn and explode, causing serious safety accidents.

[0003] Traditional electrolyte monitoring methods mostly rely on external detection equipment of the battery, such as X-ray, ultrasonic detection or chemical analysis, etc. Although these methods can evaluate the health status of the battery to a certain extent, they have certain limitations: 1. unable to monitor in real time: most traditional methods need to be carried out in a specific detection environment, and cannot realize real-time monitoring during the use of the battery; 2. high invasiveness: some detection methods may damage the structure of the battery, affecting the normal service life of the battery; 3. cost and efficiency problems: advanced detection equipment is usually expensive, and the detection process is complex and inefficient. UTILITY MODEL CONTENT

[0004] Therefore, the utility model provides a sensor for in situ detection of the amount of free electrolyte in a lithium battery, which can monitor the amount of free electrolyte and the distribution of electrolyte in the lithium battery in situ and in real time.

[0005] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0006] The utility model provides a sensor for in situ detection of the amount of free electrolyte in a lithium battery, which comprises:

[0007] An insulating shell;

[0008] A conductive polymer electrode arranged on the insulating shell; and

[0009] Two wires, one end of each of the two wires is sealed and embedded in the insulating shell and is electrically connected to different positions of the conductive polymer electrode, and the other end of each of the two wires is located outside the insulating shell.

[0010] As a further improvement of the above-mentioned scheme of the utility model, the insulating shell is of a flat structure.

[0011] As a further improvement of the above-mentioned scheme of the utility model, the conductive polymer electrode is provided with a plurality of, a plurality of windows are set up on the insulating shell and penetrate through two sides, a plurality of conductive polymer electrodes are respectively arranged at a plurality of windows, and a plurality of conductive polymer electrodes are all electrically connected with one end of two wires.

[0012] As a further improvement of the above-mentioned scheme of the utility model, the insulating shell is a polymer film made of one material or composite of multiple materials selected from polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), polystyrene (PS), polycarbonate (PC) and polymethyl methacrylate (PMMA).

[0013] As a further improvement of the above-mentioned scheme of the utility model, the conductive polymer electrode is made of one material or composite of multiple materials selected from polyaniline, derivative of polyaniline, polypyrrole, derivative of polypyrrole, polythiophene, derivative of polythiophene, poly-p-phenylene vinylene and derivative of poly-p-phenylene vinylene.

[0014] As a further improvement of the above-mentioned scheme of the utility model, the wire is gold wire, silver wire, copper wire or carbon wire.

[0015] The utility model also provides a lithium battery which comprises the sensor for in-situ detection of the amount of free electrolyte in the lithium battery.

[0016] As a further improvement of the above-mentioned scheme of the utility model, the lithium battery further comprises a shell and a cell pole group and electrolyte arranged in the shell, the sensor is arranged on the outer surface or inside of the cell pole group, and the wire of the sensor is arranged to extend out of the shell away from one end of the conductive polymer electrode.

[0017] As a further improvement of the above-mentioned scheme of the utility model, the sensor is arranged on the outer surface of the cell pole group, and the cell pole group is wrapped with an insulating film to fix the sensor.

[0018] As a further improvement of the above-mentioned scheme of the utility model, the sensor is arranged inside the cell pole group and between the positive plate and the diaphragm of the cell pole group, and the sensor is wrapped with the diaphragm.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] The sensor is used for in-situ detection of the amount of free electrolyte in a lithium battery, the sensor is implanted into the lithium battery first, during use of the lithium battery, electrochemical equilibrium is established between the conductive polymer electrode and the electrolyte, different lithium salt concentrations change the charge distribution and electrode potential on the surface of the conductive polymer electrode, the lead wire of the sensor is connected with an electrochemical workstation, the change curve of the current of the conductive polymer electrode with the potential is recorded in real time by the electrochemical workstation, the loss of the solvent in the electrolyte is indirectly judged by the potential of the conductive polymer electrode and the intensity of the response current, and thus the amount of free electrolyte in the lithium battery is obtained.

[0021] The sensor can in-situ and real-time monitor the amount and distribution state of the free electrolyte in the lithium battery, and the use safety and management efficiency of the battery can be greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structure schematic view of a sensor for in-situ detection of the amount of free electrolyte in a lithium battery is provided for the embodiment of the utility model;

[0023] Figure 2 A structure schematic view of a lithium battery is provided for the embodiment of the utility model.

[0024] Reference signs: 1, sensor; 11, insulating shell; 12, conductive polymer electrode; 13, lead wire; 2, shell; 3, cell pole group. DETAILED DESCRIPTION

[0025] In order to facilitate understanding of the utility model, the utility model will be more comprehensively described in combination with specific embodiments. However, the utility model can be realized in many different forms, and is not limited to the embodiments described in the present text. On the contrary, the purpose of providing these embodiments is to make the disclosure of the utility model more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the utility model belongs. The terms used in the specification of the utility model herein are only for the purpose of describing specific embodiments and are not intended to limit the utility model.

[0027] REFERENCE Figure 1 The embodiment provides a sensor for in-situ detection of the amount of free electrolyte in a lithium battery, which comprises an insulating shell 11, a plurality of conductive polymer electrodes 12 and two lead wires 13.

[0028] In the embodiment, the insulating shell 11 is composed of a polymer film with high electrochemical stability, and the polymer film can be one or more of polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and polymethyl methacrylate (PMMA). In the embodiment, the material of the polymer film is high-temperature-resistant PET. The insulating shell is provided with a plurality of windows penetrating through both sides thereof.

[0029] A conductive polymer electrode 12 is arranged at each window position of the insulating shell 11, so that the electrolyte can infiltrate the conductive polymer electrode 12. The material of the conductive polymer electrode 12 can be one or more of polyaniline, a derivative of polyaniline, polypyrrole, a derivative of polypyrrole, polythiophene, a derivative of polythiophene, poly-p-phenylene vinylene, and a derivative of poly-p-phenylene vinylene. In the embodiment, the material of the conductive polymer electrode 12 is polypyrrole.

[0030] One end of each of the two wires 13 is sealed and embedded in the insulating shell 11 and electrically connected to both ends of the plurality of conductive polymer electrodes 12, and the two wires 13 are not in contact with each other. The other end of each of the two wires 13 is located outside the insulating shell 11. The material of the wire 13 can be one of gold, silver, copper, and carbon material, which is made by printing or extrusion molding.

[0031] In the manufacturing of the sensor for in-situ detection of the amount of free electrolyte in a lithium battery in the embodiment, (1) the polymer film is first cut into a predetermined shape (such as a circle, an ellipse, etc.) and provided with windows, and the size of each window is 5 mm ± 0.4 mm * 2.5 mm ± 0.2 mm, and the position of the window corresponds to the position of the conductive polymer electrode 12; (2) then the conductive polymer electrode 12 is attached to the window, and the area of the conductive polymer electrode 12 is slightly larger than the window, which is 6 mm ± 0.5 mm * 3 mm ± 0.3 mm, the insulating layer on one end of the two wires 13 is peeled off, and the one end of the two wires 13 is fixed together with the plurality of conductive polymer electrodes 12 by conductive silver glue, and the two wires 13 are prevented from contacting each other; (3) another piece of polymer film is cut into a corresponding shape and covered on the polymer film containing the conductive polymer electrode 12 and the wire 13, and the two polymer films are combined together by heat sealing to realize the sealed insulation of the two wires 13, thereby forming a sealed flat sensor. The insulating layer on the outer surface of the part of the two wires 13 located outside the polymer film is retained.

[0032] The sensor for in-situ detection of the amount of free electrolyte in a lithium battery in the embodiment can be implanted in a lithium battery to facilitate in-situ detection of the amount of free electrolyte in the lithium battery. The implantable lithium battery can be compatible with common aluminum shell lithium batteries and soft package lithium batteries, and the lamination mode of the lithium battery can be Z-lamination, thermal compounding, and winding, such asFigure 2 As shown, the implantation position of the sensor 1 in the lithium battery can be the outer surface of the lithium battery cell pole group 3, or the inside of the cell pole group 3.

[0033] If the sensor 1 is located on the outer surface of the cell pole group 3, a diaphragm can be wrapped around the sensor 1 first (to avoid damage to the pole piece by the sensor 1, causing local lithium precipitation or black spots), the sensor 1 is placed on the surface of the cell pole group 3 at the corresponding position, then the sensor 1 and the cell pole group 3 are covered together with an insulating film (preferably mylar film), fixed with adhesive tape into the battery shell 2, a hole is opened on the shell 2 to lead out the lead wire of the sensor 1, and sealing glue is used to seal the opening; the subsequent manufacturing process is consistent with the conventional battery production process.

[0034] If the sensor 1 is located inside the cell pole group 3, a diaphragm is first wrapped around the sensor (to avoid damage to the pole piece by the sensor 1, causing local lithium precipitation or black spots), the sensor 1 is implanted between the positive pole piece and the diaphragm, and the lead wire 13 of the sensor 1 also needs to be wrapped with a diaphragm for insulation between the positive pole piece and the diaphragm; the assembled cell pole group 3 and diaphragm need to be fixed with a hot press, the hot pressing temperature is 50-100 degrees Celsius, and the hot pressing pressure is 3-10 tons; after hot pressing, the sensor 1 and the cell pole group 3 form a whole; then use an insulating film (preferably mylar film) to cover the pole group, open a hole in the shell 2 to lead out the lead wire 13 of the sensor 1, and seal the opening with sealing glue; the subsequent manufacturing process is consistent with the conventional battery production process.

[0035] During the use of the lithium battery, the battery shell 2 is filled with electrolyte, which will soak the cell pole group 3 and the conductive polymer electrode 12, connecting the lead wire 13 of each sensor 1 to the electrochemical workstation, and recording the peak voltage position and current response change of the sensor 1 through the electrochemical workstation during the charging and discharging process of the battery, so as to judge the residual amount of electrolyte at the position of the sensor 1, because:

[0036] The electrochemical equilibrium between the conductive polymer electrode 12 and the electrolyte is established, and the concentration of lithium salt changes the charge distribution and electrode potential on the surface of the conductive polymer electrode 12. The concentration of lithium ions in the electrolyte is the key factor affecting the potential of the conductive polymer electrode 12. The loss of the electrolyte in the lithium battery during the cycle mainly manifests the decomposition of the main solvents such as EC (ethylene carbonate), EMC (methyl ethyl carbonate) and DEC (diethyl carbonate). When the solvent content changes, the concentration of lithium ions also changes. For example, if the solvent decreases, the concentration of lithium ions increases. According to the Nernst equation, the redox potential is related to the ion activity (approximately the ion concentration). When the ion concentration increases, the redox potential also changes, so the loss of the solvent in the electrolyte can be indirectly determined by the potential change and the response current intensity of the conductive polymer electrode 12. In this embodiment, the conductive polymer electrode is prepared by using polypyrrole active material as an example. The electrochemical workstation is cyclically scanned at a constant rate, and the current change curve of the polypyrrole active material with the potential is recorded. In this process, the polypyrrole electrode undergoes redox reaction, and lithium ions in the electrolyte participate in the reaction. When the concentration of lithium salt is different, the current peak value, peak potential and other parameters of the reaction are different. By analyzing these characteristic parameters of the cyclic voltammetry curve and comparing with the calibration data of different lithium salt concentrations, the concentration of lithium salt can be determined, and the loss of the solvent can be inferred. In this test process, the concentration of lithium ions affects the conversion between the oxidized state (PPy+) and the reduced state (PPy) of polypyrrole, and the potential expression can be approximately expressed as E=E 0 +RT / nF*Ln[PPy+] / [PPy] (wherein E is the electrode potential, E 0 is the standard electrode potential, R is the gas constant, T is the temperature, n is the number of transferred electrons, and F is the Faraday constant); when the solvent decreases to cause the change of the ion concentration, the ratio of [PPy+] / [PPy] changes, so that the potential of the conductive polymer electrode 12 changes.

[0037] Taking a lithium ion battery with a capacity of 100 Ah as an example, three sensors of the embodiment are respectively buried in the top, middle and bottom regions of the electrode group of the battery. During the charging and discharging process of the battery, the current response changes of the three regions are recorded in real time by the electrochemical workstation. The results show that the loss of the residual electrolyte in the middle region of the electrode is the largest, and the loss of the residual electrolyte in the top and bottom regions is smaller. This result is consistent with the law of electrochemical reaction and structural change in the battery, and verifies the effectiveness of the sensor of the application.

[0038] Take a lithium ion battery module (6 100 Ah battery cells in series) as an example, evenly distribute multiple sensors of the embodiment in each battery cell in the module. Through long-term charge and discharge cycle test, monitor the change trend of residual electrolyte in the battery cell. The test results show that the residual electrolyte of the battery cell is obviously reduced during high-rate charge and discharge, which indicates that these battery cells may have potential safety hazards. According to this data, the design of the battery module is further optimized, and its safety performance is improved.

[0039] It should be noted that when a component is referred to as being "mounted on" another component, it can be directly on the other component or there can be a middle component. When a component is referred to as being "disposed on" another component, it can be directly disposed on the other component or there can be a middle component. When a component is referred to as being "fixed to" another component, it can be directly fixed to the other component or there can be a middle component.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but it should be considered that any combination of the technical features is within the scope of the present application, as long as the combination does not cause contradiction.

[0042] The above-described embodiments only express several embodiments of the application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the application. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are within the scope of protection of the application. Therefore, the protection scope of the application should be subject to the appended claims.

Claims

1. A sensor for in-situ detection of the amount of free electrolyte inside a lithium battery, characterized in that, It comprises: an insulating shell (11); a conductive polymer electrode (12) disposed on the insulating shell (11); and two wires (13), one end of each of the two wires (13) is sealed and embedded in the insulating shell (11) and electrically connected to the conductive polymer electrode (12) at different positions, and the other end of each of the two wires (13) is located outside the insulating shell (11).

2. The sensor for in-situ detection of amount of free electrolyte inside a lithium battery of claim 1, wherein, The insulating shell (11) is of a flat structure.

3. The sensor for in-situ detection of amount of free electrolyte inside a lithium battery of claim 2, wherein, The conductive polymer electrode (12) is provided in plurality, the insulating shell (11) is provided with a plurality of windows penetrating through both sides thereof, and the plurality of conductive polymer electrodes (12) are respectively disposed at the plurality of windows and electrically connected to one end of the two wires (13).

4. The sensor for in-situ detection of amount of free electrolyte inside a lithium battery of claim 1, wherein, The insulating shell (11) is a polymer film made of one material or a composite of multiple materials selected from polyethylene terephthalate, polyimide, polypropylene, polystyrene, polycarbonate, and polymethyl methacrylate.

5. The sensor for in-situ detection of amount of free electrolyte inside a lithium battery of claim 1, wherein, The conductive polymer electrode (12) is made of one material or a composite of multiple materials selected from polyaniline, a derivative of polyaniline, polypyrrole, a derivative of polypyrrole, polythiophene, a derivative of polythiophene, poly-p-phenylene vinylene, and a derivative of poly-p-phenylene vinylene.

6. The sensor for in-situ detection of amount of free electrolyte inside a lithium battery of claim 1, wherein, The wire (13) is a gold wire, a silver wire, a copper wire, or a carbon wire.

7. A lithium battery, characterized by It comprises the sensor (1) for in-situ detection of the amount of free electrolyte inside a lithium battery according to any one of claims 1-6.

8. The lithium battery of claim 7, wherein, The lithium battery further comprises a shell (2) and a cell pole group (3) and electrolyte disposed inside the shell (2), the sensor (1) is disposed on the outer surface or inside the cell pole group (3), and the wire (13) of the sensor (1) extends out of the shell (2) away from the conductive polymer electrode (12).

9. The lithium battery of claim 7, wherein, The sensor (1) is disposed on the outer surface of the cell pole group (3) and wrapped with a diaphragm, and the cell pole group (3) is wrapped with an insulating film to fix the sensor (1).

10. The lithium battery of claim 7, wherein, The sensor (1) is disposed inside the cell pole group (3) and located between the positive plate of the cell pole group (3) and the diaphragm, and the sensor (1) is wrapped with a diaphragm.

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