A preparation method of a potential sensor and a potential sensor

Abstract

An embodiment of the present invention provides a method for preparing a potential sensor and a potential sensor. The method comprises: uniformly dispersing an active material and a conductive carbon material in a preparation solvent according to a preset ratio; then removing the preparation solvent to allow the conductive carbon material to self-assemble into a conductive film, with the active material uniformly embedded in the inner structure of the conductive film, to obtain a reference electrode material; and cutting the reference electrode material and connecting the cut reference electrode material to a conductive tab to obtain a potential sensor. The potential sensor utilizes the conductive carbon material to self-assemble into a conductive film, and uniformly embeds the active material within the conductive film, thereby reducing side reactions between the active material and the electrolyte and preventing the active material from falling off. The sensor has a long service life and can achieve long-term monitoring and testing of the battery's negative electrode potential. Furthermore, the sensor eliminates the need for a separate substrate material and adhesive, reducing the impact on the battery itself.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a preparation method of a potential sensor and the potential sensor. Background Art

[0002] With the continuous development of electric vehicles, the safety of lithium-ion batteries, the primary power source for electric vehicles, is attracting increasing attention. Lithium-ion batteries are "rocking-chair batteries" based on the principle of intercalation and deintercalation reactions. During charging, the current ejects lithium ions from the cathode's intercalation structure. These lithium ions "swim" through the electrolyte between the positive and negative electrodes into the negative electrode's intercalation structure. During discharge, the lithium ions "swim" back from the negative electrode's intercalation structure through the electrolyte. Lithium maintains a stable ionic form throughout the intercalation and deintercalation cycle, oscillating between the intercalation structures at the battery's poles or between them. However, under high-rate or low-temperature conditions, lithium intercalation is hindered, and lithium is easily deposited on the negative electrode surface, forming lithium dendrites. On the one hand, lithium deposition reduces the amount of active lithium, causing rapid capacity degradation and shortening the battery life. On the other hand, lithium dendrites can accelerate the aging and rupture of the separator, leading to a short circuit between the positive and negative electrodes. They are also prone to side reactions with electrolytes and other factors, accelerating thermal runaway and posing a significant safety hazard.

[0003] Therefore, in order to avoid the safety hazards caused by lithium plating at the negative electrode, it is necessary to monitor the negative electrode potential in real time during the battery charging and discharging process to keep the negative electrode potential above the lithium plating potential. However, current battery tests can often only obtain the voltage difference between the positive and negative electrodes, and cannot accurately obtain the single electrode potential of the battery's negative electrode in real time to monitor changes in the battery's internal state. Summary of the Invention

[0004] This specification provides a method for preparing a potential sensor and a potential sensor, to overcome at least one technical problem existing in the prior art.

[0005] In a first aspect, according to an embodiment of this specification, a method for preparing a potentiometric sensor is provided, the method comprising:

[0006] The active material and the conductive carbon material are uniformly dispersed in a preparation solvent according to a preset ratio, and then the preparation solvent is removed to allow the conductive carbon material to self-assemble into a conductive film, and the active material is uniformly embedded in the inner layer structure of the conductive film to obtain a reference electrode material;

[0007] The reference electrode material is cut, and the cut reference electrode material is connected to a conductive electrode lug to obtain a potential sensor.

[0008] Optionally, the method further includes:

[0009] The thickness of the reference electrode material can be regulated by controlling the addition amount of the conductive carbon material.

[0010] Optionally, the conductive electrode tab is a metal tab, and one end of the conductive electrode tab is connected to one end of the cut reference electrode material through a conductive gel.

[0011] Optionally, the step of uniformly dispersing the active material and the conductive carbon material in a preparation solvent in a preset ratio, and then removing the preparation solvent to allow the conductive carbon material to self-assemble into a conductive film, wherein the active material is uniformly embedded in the inner layer structure of the conductive film, specifically includes:

[0012] adding the active material and the conductive carbon material into the preparation solvent according to the preset ratio, and then using a uniform dispersion method to uniformly disperse the active material and the conductive carbon material in the preparation solvent;

[0013] The solvent removal method is adopted to remove the preparation solvent after the active material and the conductive carbon material are uniformly dispersed, so as to obtain the conductive film embedded with the uniformly distributed active material.

[0014] Further optionally, the uniform dispersion method is one or more of an ultrasonic dispersion method, a cell crusher dispersion method, or a dispersant-added stirring dispersion method.

[0015] Further optionally, the solvent removal method is one or more of a vacuum filtration method, a drying method, and an air-drying method.

[0016] Optionally, the active material is one or more of titanium dioxide, lithium titanate, and lithium iron phosphate.

[0017] Optionally, the conductive carbon material is one or more of graphene, carbon nanotubes, and carbon fibers.

[0018] Optionally, the preparation solvent is one or more of anhydrous ethanol, deionized water, and N-methylpyrrolidone.

[0019] In a second aspect, according to an embodiment of this specification, a potential sensor is provided, comprising: a reference electrode and a conductive electrode lug connected to the reference electrode, wherein the reference electrode comprises a conductive film self-assembled from a conductive carbon material and an active material uniformly embedded in the conductive film.

[0020] The beneficial effects of the embodiments of this specification are as follows:

[0021] Conductive carbon materials are self-assembled into a conductive film, and the active material is uniformly embedded in the inner layer structure of the conductive film, forming an integrated potential sensor without a substrate or binder. The potential sensor does not require adhesives or substrate materials during the preparation process, making the preparation process simple. The thickness of the sensor can be controlled by adjusting the amount of conductive carbon material added. After implantation into the battery, the impact on the battery itself is minimal. In addition, because the active material of the potential sensor is embedded in the conductive film and evenly dispersed within the conductive film, while ensuring good conductivity, the active material is not easily detached, and the side reaction between the active material and the electrolyte can be reduced, thereby giving the potential sensor a long service life and enabling long-term static and dynamic monitoring and testing of the negative electrode potential of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic flow chart of a method for preparing a potentiometric sensor according to an embodiment of this specification;

[0024] Figure 2 A schematic diagram of the structure of a potential sensor provided in an embodiment of this specification;

[0025] Figure 3 This is a comparison chart of the negative electrode potential of a battery during cycling monitored by the embodiment of this specification and the prior art. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] It should be noted that the terms "including" and "having" and any variations thereof in the embodiments of this specification and the accompanying drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to the process, method, product, or apparatus.

[0028] In the prior art, the method of implanting a reference electrode in a battery can be used to monitor the potential of a single electrode of a battery. Among them, the copper wire lithium-plated electrode is currently a more commonly used reference electrode, but due to the small diameter of the copper wire, the amount of lithium plating is limited, and because the lithium plating layer is only loaded on the surface of the copper wire substrate, it is easy to fall off from the copper wire, resulting in a very short service life of the copper wire lithium-plated electrode, and it is impossible to perform long-term static and dynamic monitoring tests on the negative electrode potential of the battery; aluminum foil coated lithium titanate is another more commonly used reference electrode. In this type of reference electrode, the aluminum foil substrate will hinder the transmission of lithium ions during the battery cycle, affecting the electrochemical performance of the battery itself, and the active material (i.e., lithium titanate) in this type of reference electrode is also loaded on the substrate surface, which is easy to react with the electrolyte, resulting in the active material easily falling off during use, and also unable to perform long-term static and dynamic monitoring tests on the negative electrode potential of the battery. It should be noted that the battery described in this specification is a lithium-ion battery.

[0029] In order to solve the above problems, the present invention discloses a potential sensor. Figure 2 As shown, the potential sensor includes: a reference electrode 1 and a conductive tab 2 connected to the reference electrode 1. The reference electrode 1 is the sensitive material of the potential sensor. When static and dynamic monitoring tests are performed on the negative electrode potential of the battery, the electrical signal is directly obtained and transmitted through the conductive tab 2.

[0030] The reference electrode 1 includes a conductive film formed by self-assembly of a conductive carbon material and an active material uniformly embedded in the conductive film. The conductive carbon material is self-assembled into the conductive film, and the active material is uniformly embedded in the inner layer structure of the conductive film, forming an integrated potential sensor without a substrate and a binder. Since the potential sensor does not require a substrate and a binder, it has little impact on the battery itself after being implanted in the battery. In addition, since the active material is embedded in the conductive film, the active material is integrated with the conductive film and uniformly dispersed in the conductive film, thereby ensuring good conductivity while making the active material not easy to fall off, thereby greatly reducing the side reaction between the active material and the electrolyte, thereby making the potential sensor have a long service life and capable of performing long-term static and dynamic monitoring tests on the negative electrode potential of the battery.

[0031] The potential sensor and its preparation method are described in detail below.

[0032] like Figure 1 As shown, the preparation method of the potential sensor includes the following steps:

[0033] Step 100: The active material and the conductive carbon material are uniformly dispersed in a preparation solvent in a preset ratio, and then the preparation solvent is removed to allow the conductive carbon material to self-assemble into a conductive film, and the active material is uniformly embedded in the inner layer structure of the conductive film to obtain a reference electrode material.

[0034] In one embodiment, the active material and the conductive carbon material are added to a preparation solvent in a preset ratio, and then a uniform dispersion method is used to uniformly disperse the active material and the conductive carbon material in the preparation solvent; thereafter, a solvent removal method is used to remove the preparation solvent after the active material and the conductive carbon material are uniformly dispersed, thereby obtaining a conductive film embedded with a uniformly distributed active material.

[0035] The preset ratio mentioned above refers to the mass ratio between the active material and the conductive carbon material. According to the preset mass ratio, a certain amount of active material and conductive carbon material are added to the preparation solvent together, and the active material and conductive carbon material are uniformly dispersed in the preparation solvent using a uniform dispersion method, so that after the reference electrode material is prepared, the active material can be uniformly embedded in the conductive carbon material. Afterwards, the preparation solvent is removed by a solvent removal method, so that the conductive carbon material self-assembles into a conductive film, and the active material is uniformly embedded in the film structure. Optionally, the conductive film self-assembled by the conductive carbon material has a thickness of 5μm-500μm and a porosity of 20%-80%, thereby completing the preparation of a conductive film embedded with active material, that is, obtaining the reference electrode material required for preparing the potential sensor.

[0036] In an optional embodiment, the uniform dispersion method is one or more of an ultrasonic dispersion method, a cell crusher dispersion method, or a dispersant-added stirring dispersion method.

[0037] In an optional embodiment, the solvent removal method is one or more of a vacuum filtration method, a drying method, and an air-drying method.

[0038] In addition, in an optional embodiment, the active material is one or more of titanium dioxide, lithium titanate, and lithium iron phosphate. Of course, other active materials can also be selected and are not limited here.

[0039] In an optional embodiment, the conductive carbon material is one or more of graphene, carbon nanotubes, and carbon fibers. Of course, other carbon materials with good conductivity may also be used.

[0040] In an optional embodiment, the preparation solvent is one or more of anhydrous ethanol, deionized water, and N-methylpyrrolidone. Other preparation solvents that do not react with the active material and the conductive carbon material may also be used.

[0041] In the embodiments of this specification, the thickness of the reference electrode material can also be controlled by controlling the amount of conductive carbon material added, that is, by controlling the mass value of the conductive carbon material used, the thickness of the potential sensor finally obtained can be controlled, so that the thickness of the prepared potential sensor can be controlled, thereby preparing a potential sensor of appropriate thickness according to specific needs, with stronger adaptability and less impact on the battery itself when implanted in a battery.

[0042] Step 200: cutting the reference electrode material, and connecting the cut reference electrode material to the conductive electrode lug to obtain a potential sensor.

[0043] In one embodiment, the conductive film embedded with active materials obtained in step 100 is first dried to facilitate subsequent cutting. For example, the conductive film embedded with active materials is placed in an oven for drying. Optionally, the drying temperature is 40° C. to 80° C., and the drying time is 3 hours to 48 hours.

[0044] Afterwards, the dried reference electrode material is cut into strips, optionally with a length of 0.1 cm–10 cm and a width of 0.5 mm–10 mm, and one end of the strip is connected to a conductive electrode ear, thereby preparing a substrate-free and binder-free integrated potential sensor.

[0045] In a specific embodiment, the conductive electrode tab is a metal tab, and one end of the conductive electrode tab is connected to one end of the cut reference electrode material through a conductive gel.

[0046] The potential sensor adopts a baseless and binderless integrated structural design. The active material with a known stable potential is uniformly embedded in a conductive film self-assembled from a conductive carbon material. The film is then cut into long strips and one end is connected to a conductive electrode ear to prepare an integrated potential sensor with no base and no binder embedded in the active material. In the preparation process of the potential sensor, no binder and base material are required. The preparation process is simple, and the thickness of the prepared potential sensor is controllable. After being implanted in the battery, the impact on the battery itself is small. In addition, since the active material of the potential sensor is embedded in the conductive film with controllable thickness and is uniformly dispersed, it not only ensures good conductivity, but also makes the active material not easy to fall off. At the same time, it can reduce side reactions with the electrolyte, so that the prepared potential sensor has a long service life and can monitor and test the negative electrode potential of the battery for a long time.

[0047] In order to further understand the present invention, the preparation method of the potential sensor provided in this specification is described in detail below with reference to a specific embodiment. It should be noted that the scope of protection of the present invention is not limited by the following embodiment.

[0048] In this embodiment, lithium titanate (LTO) is used as the active material, graphene is used as the conductive carbon material, anhydrous ethanol is used as the preparation solvent, ultrasonic dispersion and cell crusher dispersion are used as the uniform dispersion method, and vacuum filtration is used as the solvent removal method. The specific steps of the potentiometric sensor preparation method include the following steps:

[0049] S10: adding graphene and LTO nanopowders into anhydrous ethanol at a preset mass ratio of 2:1, and then performing ultrasonic dispersion using a cell crusher to uniformly disperse the graphene and LTO in the anhydrous ethanol.

[0050] S20: Pour 10 mL of the anhydrous ethanol dispersion of graphene and LTO into a vacuum filtration bottle for filtration. After filtration, a graphene film uniformly embedded with LTO particles is obtained. The graphene film obtained at this time is supported on the filter paper.

[0051] S30: placing the filter paper loaded with the graphene film in an oven at 80° C. for drying, and the drying time is set to 24 h.

[0052] S40: peeling off the graphene film from the filter paper after drying in the above step S30, cutting it into 2mm×50mm strips, and then connecting one end of the strips to the metal tab through the conductive gel to obtain an integrated potential sensor, such as Figure 2 shown.

[0053] The following uses a 250mAh NCM811-graphite system battery as an example to specifically illustrate the working principle of using the above-mentioned integrated potential sensor for the negative electrode potential monitoring test of the battery.

[0054] The end of the potential sensor not connected to the metal tab is wrapped with a diaphragm, and then implanted between the positive and negative electrodes of a 250mAh NCM811-graphite system finished soft-pack battery cell, with the metal tab exposed outside the cell. The battery is then filled with liquid and sealed. After that, it is left to stand for 24 hours, and the current and voltage positive and negative poles of the charge and discharge instrument are connected to the positive and negative electrodes of the battery, respectively. The voltage positive and negative poles of the auxiliary channel are connected to the negative electrode of the battery and the metal tab of the potential sensor, respectively. The battery is then subjected to a charge and discharge cycle test at a charge and discharge rate of 0.3C, and the potential difference between the potential sensor and the negative electrode of the battery is collected. The test results are as follows: Figure 3 As shown in the Anode vs. Re (Example) curve.

[0055] To verify that the potential sensor has a longer service life than the existing technology and can perform long-term static and dynamic monitoring tests on the negative electrode potential of the battery, the substrate-free potential sensor in the above specific embodiment is replaced with a potential sensor with an aluminum foil substrate. LTO active material is coated on the surface of the aluminum foil substrate, and the substrate is placed in a battery for comparative battery negative electrode potential monitoring testing, which specifically includes the following steps:

[0056] D10: Add LTO nanopowder, graphene, and polyvinylidene fluoride (PVDF) to the preparation solvent of N-methylpyrrolidone in a ratio of 6:3:1, and then stir evenly in a homogenizer.

[0057] D20: The uniform slurry prepared in the above step D10 is coated on an aluminum foil substrate, and then placed in an 80° C. oven for drying. The drying time is set to 24 hours.

[0058] D30: The aluminum foil loaded with active material obtained after drying is cut into 2mm×50mm strips, and then the end not coated with active material is connected to the metal tab to obtain a potential sensor with LTO active material loaded on the surface of the aluminum foil substrate.

[0059] D40: Wrap the end of the potential sensor obtained in the above step D30 that is not connected to the metal tab with a diaphragm and implant it between the positive and negative electrodes of a 250mAh NCM811-graphite system finished soft-pack battery cell, with the metal tab exposed outside the battery cell. Then, fill the battery with liquid and seal it.

[0060] D50: After standing for 24 hours, connect the current and voltage positive and negative wires of the charge and discharge instrument to the positive and negative electrodes of the above battery respectively, connect the voltage positive and negative wires of the auxiliary channel to the negative electrode of the battery and the metal tabs of the potential sensor respectively, and then perform a charge and discharge cycle test on the battery at a charge and discharge rate of 0.3C. At the same time, collect the potential difference between the potential sensor and the negative electrode of the battery. The test results are as follows: Figure 3 As shown in the Anode vs. Re (comparative ratio) curve.

[0061] in, Figure 3 The Ca vs. An curve in the figure represents the full battery cycle voltage change curve, which is used to reflect the battery cycle status and detect whether there is any abnormality. Figure 3 The Ca vs. An curves shown indicate that there is no abnormality in the cycles of the batteries in the above specific embodiments and comparative examples.

[0062] The stability of the negative electrode potential (Anode vs. Re) of the battery during the cycle measured by the potential sensor prepared in the embodiment was compared with that of the negative electrode potential (Anode vs. Re) measured by the potential sensor with active material loaded on the surface of the aluminum foil substrate in the comparative example. The results are as follows: Figure 3 As shown by Figure 3 As shown, during the test period of more than 200 hours, the negative electrode potential measured by the potential sensor in the embodiment has good consistency during the cycle process, indicating that the integrated potential sensor is relatively stable and can monitor the negative electrode potential for a long time. However, the stability of the potential sensor in the comparative example with the active material loaded on the surface of the aluminum foil substrate is poor, which may be due to the active material being exposed to the electrolyte, reacting with the electrolyte and falling off from the substrate surface, resulting in its lifespan reduction.

[0063] Therefore, it can be seen from the above that the integrated potential sensor disclosed in this specification can measure the negative electrode potential during the battery cycle for a long time. Compared with the potential sensor in the prior art with active materials loaded on the substrate surface, it is more stable and has a longer service life.

[0064] In summary, this specification discloses a method for preparing a potential sensor and a potential sensor, which uses conductive carbon materials to self-assemble into a conductive film, and at the same time, the active material is uniformly embedded in the inner layer structure of the conductive film to form an integrated potential sensor without a substrate and a binder. The potential sensor does not require adhesives and substrate materials during the preparation process, and the preparation process is simple. The thickness of the sensor can be controlled by regulating the amount of conductive carbon material added, and the impact on the battery itself after implantation in the battery is small. In addition, because the active material of the potential sensor is embedded in the conductive film and uniformly dispersed in the conductive film, while ensuring good conductivity, the active material is not easy to fall off, and the side reaction of the active material with the electrolyte can be reduced, so that the potential sensor has a long service life and can perform long-term static and dynamic monitoring tests on the negative electrode potential of the battery.

[0065] Those skilled in the art will appreciate that the accompanying drawings are merely schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0066] Those skilled in the art will appreciate that the modules in the apparatuses of the embodiments may be distributed in the apparatuses of the embodiments as described in the embodiments, or may be located in one or more apparatuses different from the embodiments with corresponding changes. The modules in the above embodiments may be combined into one module or further divided into multiple sub-modules.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a potentiometric sensor, characterized in that: The method comprises: The active material and the conductive carbon material are uniformly dispersed in a preparation solvent in a preset ratio; wherein the active material is one or more of titanium dioxide, lithium titanate, and lithium iron phosphate, and the conductive carbon material is one or more of graphene, carbon nanotubes, and carbon fibers; and the uniform dispersion method is one or more of an ultrasonic dispersion method, a cell crusher dispersion method, or a dispersant-added stirring dispersion method; Then, the preparation solvent is removed, and the conductive carbon material is self-assembled into a conductive film, and the active material is uniformly embedded in the inner layer structure of the conductive film, so as to obtain an integrated reference electrode material without a substrate and a binder; Cutting the reference electrode material, and connecting the cut reference electrode material to a conductive electrode lug to obtain a potential sensor; The conductive film has a thickness of 5 μm-500 μm and a porosity of 20%-80%.

2. The method for preparing a potential sensor according to claim 1, wherein: The method further comprises: The thickness of the reference electrode material can be regulated by controlling the addition amount of the conductive carbon material.

3. The method for preparing a potential sensor according to claim 1, wherein: The conductive electrode tab is a metal tab, and one end of the conductive electrode tab is connected to one end of the cut reference electrode material through a conductive gel.

4. The method for preparing a potential sensor according to claim 1, wherein: The process of uniformly dispersing the active material and the conductive carbon material in a preparation solvent in a preset ratio, and then removing the preparation solvent to allow the conductive carbon material to self-assemble into a conductive film, wherein the active material is uniformly embedded in the inner layer structure of the conductive film, specifically includes: adding the active material and the conductive carbon material into the preparation solvent according to the preset ratio, and then using a uniform dispersion method to uniformly disperse the active material and the conductive carbon material in the preparation solvent; The solvent removal method is adopted to remove the preparation solvent after the active material and the conductive carbon material are uniformly dispersed, so as to obtain the conductive film embedded with the uniformly distributed active material.

5. The method for preparing a potential sensor according to claim 4, wherein: The solvent removal method is one or more of a vacuum filtration method, a drying method, and an air-drying method.

6. The method for preparing a potential sensor according to any one of claims 1 to 5, characterized in that: The preparation solvent is one or more of anhydrous ethanol, deionized water, and N-methylpyrrolidone.

7. A potential sensor prepared by the method for preparing a potential sensor according to any one of claims 1 to 6, characterized in that: include: A reference electrode and a conductive electrode lug connected to the reference electrode, wherein the reference electrode comprises a conductive film formed by self-assembly of a conductive carbon material and an active material uniformly embedded in the conductive film.

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