Three-electrode lithium ion battery, preparation method thereof and vehicle

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a three-electrode lithium ion battery, a preparation method thereof and a vehicle. The three-electrode lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte, a diaphragm and a reference electrode, wherein the reference electrode comprises a lithium titanate coating and a PVDF (Polyvinylidene Fluoride) coating; the diaphragm is arranged between the positive pole piece and the negative pole piece; the lithium titanate coating is arranged on the surface of any side of the diaphragm. According to the three-electrode lithium ion battery provided by the invention, the lithium titanate coating in the reference electrode has high thermal stability and long cycle life, so that on one hand, the lithium titanate coating serving as one part of the reference electrode can effectively prolong the service life of the reference electrode, and on the other hand, the problem of thermal shrinkage of the diaphragm can be effectively improved; therefore, the safety and the stability of the lithium ion battery are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a three-electrode lithium-ion battery, its preparation method, and a vehicle thereof. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density and long cycle life, and are widely used in portable electronic devices and electric vehicles. However, as the operating time increases, the performance of lithium-ion batteries gradually deteriorates, resulting in capacity decay.

[0003] On the one hand, the separators in lithium-ion batteries are usually made of polyolefins. Although they can provide sufficient mechanical strength and chemical stability at room temperature, they will exhibit significant thermal shrinkage under high temperature conditions, which can lead to short circuits between the positive and negative electrodes and even cause safety problems.

[0004] On the other hand, during battery design and research, it is necessary to independently analyze the impact of the positive and negative electrodes on battery capacity changes. Therefore, a reference electrode needs to be introduced into the full cell to measure the potential and impedance of the positive and negative electrodes relative to the reference electrode, enabling monitoring of the performance of the positive and negative electrodes during charge and discharge, and effectively distinguishing their electrochemical behaviors. However, for traditional lithium-ion three-electrode batteries, copper wire plated with lithium is typically used as the reference electrode. The lithium plating layer is very prone to failure in the electrolyte, leading to the deactivation of the reference electrode. Furthermore, using copper wire as the substrate for the reference electrode can easily result in poor sealing during cell sealing, leading to leakage risks. Moreover, placing the reference electrode inside the cell hinders lithium-ion transport between the positive and negative electrodes during charge and discharge, affecting battery performance and interfering with the electrical signal of the reference electrode, thus affecting the accuracy of test results.

[0005] Therefore, we hope to change the design approach in order to simultaneously solve the problems of high-temperature thermal shrinkage of the diaphragm and the existing reference electrode. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a three-electrode lithium-ion battery, its preparation method, and a vehicle thereof. The three-electrode lithium-ion battery provided by this invention effectively improves the thermal shrinkage problem of the separator by setting a reference electrode with high thermal stability on the separator, thereby effectively improving the safety and stability of the lithium-ion battery. At the same time, the reference electrode has an extended cycle life.

[0007] In a first aspect, the present invention provides a three-electrode lithium-ion battery, the three-electrode lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, a separator and a reference electrode, wherein the reference electrode comprises a lithium titanate coating and a PVDF coating;

[0008] The diaphragm is placed between the positive electrode and the negative electrode;

[0009] The lithium titanate coating is provided on either side of the diaphragm surface.

[0010] The three-electrode lithium-ion battery provided by this invention has a lithium titanate coating in the reference electrode that has high thermal stability and long cycle life. On the one hand, as part of the reference electrode, it can effectively improve the life of the reference electrode. On the other hand, it can effectively improve the thermal shrinkage problem of the separator, thereby effectively improving the safety and stability of the lithium-ion battery.

[0011] As a preferred embodiment of the present invention, the reference electrode further includes a reference tab, which comprises an aluminum substrate, a lithium titanate coating, and a PVDF coating, wherein the aluminum substrate is connected to the diaphragm.

[0012] The lithium titanate coating in the reference tab and the lithium titanate coating included in the reference electrode of the present invention are lithium titanate coatings obtained by an integrated coating process and have the same thickness; the PVDF coating in the reference tab and the PVDF coating included in the reference electrode are PVDF coatings obtained by an integrated coating process and have the same thickness.

[0013] The reference electrode of this invention includes a reference tab, a lithium titanate coating, and a PVDF coating. An aluminum substrate is connected to a separator. The lithium titanate coating and the PVDF coating are integrally coated sequentially on either side of the aluminum substrate and the separator. A schematic diagram of the prepared separator-reference electrode structure is shown below. Figure 1 As shown, the presence of the PVDF coating avoids direct contact between the lithium titanate coating and the positive and negative electrode sheets, while simultaneously strengthening the adhesion between the lithium titanate coating and the aluminum substrate. Furthermore, the lithium titanate coating extends beyond the positive and negative electrode sheets (the lithium titanate coating within the reference tab), thus not interfering with lithium-ion transport between the positive and negative electrodes. Simultaneously, using an aluminum substrate as the reference electrode substrate and utilizing tab sealant during heat sealing effectively solves the leakage problem near the reference electrode after it is sealed to the housing.

[0014] As a preferred embodiment of the present invention, the thickness of the lithium titanate coating is 0.5-5μm, for example, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0015] The thickness of the lithium titanate coating must be within the range of this invention. If the thickness is too small, the reference electrode cannot effectively improve the high-temperature shrinkage problem of the separator. If the thickness is too large, the lithium intercalation path of the negative electrode becomes longer, the impedance increases, and lithium plating is easily generated, leading to abnormal reference electrode potential.

[0016] As a preferred embodiment of the present invention, the thickness of the PVDF coating is 0.1-3μm, such as 0.1μm, 0.5μm, 1μm, 2μm, 3μm, etc.

[0017] The thickness of the PVDF coating must be within the range of this invention. If the thickness is too small, the reference electrode cannot effectively improve the high-temperature shrinkage problem of the separator. If the thickness is too large, it will increase the internal resistance of the battery and thus affect the battery performance.

[0018] As a preferred embodiment of the present invention, the lithium titanate coating comprises 75-85 wt% lithium titanate, 8-13 wt% conductive agent, and 8-13 wt% binder. The 75-85 wt% can be 75 wt%, 78 wt%, 80 wt%, 82 wt%, 85 wt%, etc., and the 8-13 wt% can be 8 wt%, 10 wt%, 12 wt%, 13 wt%, etc.

[0019] When the composition of the lithium titanate coating is within the above range, it exhibits superior thermal stability and long cycle life, which can more effectively improve the life of the reference electrode and alleviate the thermal shrinkage problem of the separator, thereby more effectively improving the safety and stability of lithium-ion batteries.

[0020] As a preferred embodiment of the present invention, the conductive agent includes any one or more of conductive carbon black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, or graphene.

[0021] As a preferred embodiment of the present invention, the adhesive includes any one or more of PVDF, SBR, CMC, PEO, PAN, PEG, or PEGMEA.

[0022] As a preferred embodiment of the present invention, the lithium titanate coating comprises 80 wt% lithium titanate, 10 wt% conductive carbon black and 10 wt% PVDF, at which point the overall performance of the lithium titanate coating is optimal.

[0023] As a preferred embodiment of the present invention, the width of the aluminum substrate is 0.5-1cm, such as 0.5cm, 0.6cm, 0.7cm, 0.8cm, 0.9cm, 1cm, etc.

[0024] The width direction of the aluminum substrate in this invention is consistent with the width direction of the diaphragm. The reference tab includes an aluminum substrate, a lithium titanate coating, and a PVDF coating. The lithium titanate coating and the PVDF coating are completely coated on the surface of the aluminum substrate. Correspondingly, the width of the lithium titanate coating and the PVDF coating on the reference tab is 0.5-1 cm.

[0025] In a preferred embodiment of the present invention, the positive electrode plate is connected to the positive electrode tab, and the negative electrode plate is connected to the negative electrode tab.

[0026] In a second aspect, the present invention provides a method for preparing the three-electrode lithium-ion battery described in the first aspect, the method comprising:

[0027] (1) Lithium titanate slurry and PVDF slurry are sequentially coated on the diaphragm to obtain a diaphragm-reference electrode;

[0028] (2) The positive electrode, the separator-reference electrode, and the negative electrode are stacked, packaged, and filled with electrolyte to obtain the three-electrode lithium-ion battery.

[0029] In the preparation method provided by the present invention, a lithium titanate coating and a PVDF coating are sequentially coated on the separator. On the one hand, this effectively improves the thermal shrinkage problem of the separator, and on the other hand, it avoids direct contact between the lithium titanate coating and the positive and negative electrode sheets. Moreover, the preparation method is simple and suitable for mass production.

[0030] As a preferred technical solution of the present invention, step (1) is as follows: connecting the diaphragm to the aluminum substrate, simultaneously coating the diaphragm and the aluminum substrate with lithium titanate slurry to obtain a lithium titanate coating, and coating the lithium titanate coating with PVDF slurry to obtain a diaphragm-reference electrode.

[0031] In the preparation method provided by this invention, a separator is connected to an aluminum substrate, and then lithium titanate slurry is simultaneously and integrally coated on both the separator and the aluminum substrate, thereby forming a lithium titanate coating on both the separator and the aluminum substrate. Then, PVDF slurry is uniformly coated onto the lithium titanate coating to form a PVDF adhesive layer. This avoids direct contact between the reference electrode and the positive and negative electrode plates, while simultaneously strengthening the adhesion between the lithium titanate coating and the aluminum substrate. The reference electrode in the separator-reference electrode prepared by this invention can be located close to either the positive or negative electrode plate.

[0032] As a preferred embodiment of the present invention, the thickness of the lithium titanate coating is 0.5-5μm, for example, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0033] As a preferred embodiment of the present invention, the thickness of the PVDF coating is 0.1-3μm, such as 0.1μm, 0.5μm, 1μm, 2μm, 3μm, etc.

[0034] As a preferred embodiment of the present invention, the PVDF slurry is coated by hot-press coating, preferably by hot-press roller coating.

[0035] As a preferred embodiment of the present invention, the hot pressing temperature of the hot pressing coating is 70-120℃, such as 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, etc.

[0036] As a preferred embodiment of the present invention, the hot pressing pressure of the hot pressing coating is 0.5-3MPa, for example 0.5MPa, 1MPa, 2MPa, 3MPa, etc.

[0037] As a preferred embodiment of the present invention, the hot pressing time for hot pressing coating is 5-50s, such as 5s, 10s, 20s, 30s, 40s, 50s, etc.

[0038] As a preferred technical solution of the present invention, before stacking the positive electrode, the diaphragm-reference electrode and the negative electrode in step (2), the positive electrode needs to be connected to the positive electrode tab and the negative electrode needs to be connected to the negative electrode tab, that is, the positive electrode is welded to one end of the positive electrode tab and the negative electrode is welded to one end of the negative electrode tab.

[0039] This invention stacks and assembles a positive electrode, a separator-reference electrode, and a negative electrode, and encapsulates them using an aluminum-plastic film. One end of the positive electrode tab, negative electrode tab, and reference electrode tab (aluminum substrate) is connected to the positive electrode, negative electrode, and separator, respectively. The other end of the positive electrode tab, negative electrode tab, and reference electrode tab is led out of the aluminum-plastic film, and an electrolyte is filled into the aluminum-plastic film to obtain the three-electrode lithium-ion battery.

[0040] As a preferred embodiment of the present invention, the reference tab is sealed on the aluminum-plastic film by tab adhesive.

[0041] This invention utilizes tab sealant during the heat sealing process, effectively solving the leakage problem near the reference electrode after the reference electrode is sealed to the housing.

[0042] As a preferred embodiment of the present invention, the positive electrode tab is sealed on the aluminum-plastic film by tab adhesive.

[0043] As a preferred embodiment of the present invention, the negative electrode tab is sealed on the aluminum-plastic film by tab adhesive.

[0044] This invention does not impose any special limitation on the length of the tab adhesive, as long as it can seal the tab on the aluminum-plastic film. Preferably, the length of the tab adhesive is 0.5-1cm, such as 0.5cm, 0.6cm, 0.8cm, 1cm, etc. This invention uses tab adhesive to seal the tabs. Preferably, the length of the tab sealed inside the battery is 1-2cm, such as 1cm, 1.2cm, 1.4cm, 1.6cm, 1.8cm, 2cm, etc.; preferably, the length of the tab exposed outside the battery is 1-2cm, such as 1cm, 1.2cm, 1.4cm, 1.6cm, 1.8cm, 2cm, etc. The tabs mentioned here include positive tabs, negative tabs, and reference tabs.

[0045] Thirdly, the present invention provides a vehicle comprising the three-electrode lithium-ion battery described in the first aspect or the three-electrode lithium-ion battery prepared by the preparation method described in the second aspect.

[0046] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art:

[0047] The three-electrode lithium-ion battery provided by this invention has a lithium titanate coating in the reference electrode that has high thermal stability and long cycle life. On the one hand, as part of the reference electrode, it can effectively improve the life of the reference electrode. On the other hand, it can effectively improve the thermal shrinkage problem of the separator, thereby effectively improving the safety and stability of the lithium-ion battery. Attached Figure Description

[0048] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the diaphragm-reference electrode prepared in Example 1 of the present invention;

[0051] Among them, 41-separator, 42-lithium titanate coating, 43-PVDF coating, 44-aluminum substrate.

[0052] Figure 2 This is a schematic diagram of the structure of the lithium-ion battery prepared in Example 1 of the present invention;

[0053] Among them, 20-positive electrode sheet, 21-positive electrode tab, 30-negative electrode sheet, 31-negative electrode tab, 40-diaphragm-reference electrode, and 50-aluminum-plastic film. Detailed Implementation

[0054] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0055] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of the invention.

[0056] Example 1

[0057] This embodiment provides a three-electrode lithium-ion battery and its preparation method, the preparation method including the following steps:

[0058] (1) A PE separator and an aluminum substrate (1 cm wide) are connected. A lithium titanate slurry is simultaneously coated onto both the separator and the aluminum substrate. The lithium titanate slurry consists of 80 wt% lithium titanate, 10 wt% conductive carbon black, and 10 wt% PVDF, thus forming a lithium titanate coating with a thickness of 1.5 μm on both the separator and the aluminum substrate. Then, a PVDF slurry is uniformly coated onto the lithium titanate coating using a hot-press roller coating process to form a PVDF coating with a thickness of 2 μm, resulting in a separator-reference electrode (e.g., ...). Figure 1 As shown in the figure, the hot pressing temperature is 100℃, the hot pressing pressure is 1.5MPa, and the hot pressing time is 30s;

[0059] (2) Place the above-mentioned separator-reference electrode between the positive and negative electrode plates, weld the positive electrode plate to one end of the positive electrode tab, and weld the negative electrode plate to one end of the negative electrode tab. Lead out the other ends of the positive electrode tab, negative electrode tab, and reference electrode tab through the aluminum-plastic film; encapsulate the battery cell in the aluminum-plastic film, and fill the aluminum-plastic film with electrolyte (1mol / L LiPF6, EC:PC:DMC=1:1:1), and seal the tabs on the aluminum-plastic film with tab adhesive. The length of the tab adhesive is 0.8cm, the length of the tab sealed inside the battery is 1.5cm, and the length of the tab exposed outside the battery is 1.5cm, thus obtaining the three-electrode lithium-ion battery (e.g., Figure 2 (As shown).

[0060] Example 2

[0061] This embodiment provides a three-electrode lithium-ion battery and its preparation method, the preparation method including the following steps:

[0062] (1) A PE diaphragm and an aluminum substrate (width 0.5 cm) are connected. A lithium titanate slurry is simultaneously coated on the diaphragm and the aluminum substrate. The lithium titanate slurry consists of 85 wt% lithium titanate, 8 wt% carbon nanotubes and 7 wt% PAN, thus forming a lithium titanate coating with a thickness of 5 μm on the diaphragm and the aluminum substrate. Then, a PVDF slurry is uniformly coated on the lithium titanate coating by a hot-pressing roller coating process to form a PVDF coating with a thickness of 3 μm, thus obtaining a diaphragm-reference electrode. The hot-pressing temperature is 120℃, the hot-pressing pressure is 0.5 MPa and the hot-pressing time is 50 s.

[0063] (2) Place the above-mentioned separator-reference electrode between the positive and negative electrode plates, weld the positive electrode plate to one end of the positive electrode tab, weld the negative electrode plate to one end of the negative electrode tab, and lead out the other ends of the positive electrode tab, negative electrode tab and reference electrode tab through the aluminum-plastic film; encapsulate the cell in the aluminum-plastic film, and fill the aluminum-plastic film with electrolyte (1mol / L LiPF6, EC:PC:DMC=1:1:1), and seal the tabs on the aluminum-plastic film with tab adhesive. The length of the tab adhesive is 0.5cm, the length of the tab sealed inside the battery is 1cm, and the length of the tab exposed outside the battery is 2cm, thus obtaining the three-electrode lithium-ion battery.

[0064] Example 3

[0065] This embodiment provides a three-electrode lithium-ion battery and its preparation method, the preparation method including the following steps:

[0066] (1) A PE diaphragm and an aluminum substrate (width 0.8 cm) are connected. A lithium titanate slurry is simultaneously coated on the diaphragm and the aluminum substrate. The lithium titanate slurry consists of 75 wt% lithium titanate, 12 wt% conductive graphite and 13 wt% SBR+CMC (SBR:CMC = 1:1), thus forming a lithium titanate coating with a thickness of 0.5 μm on both the diaphragm and the aluminum substrate. Then, a PVDF slurry is uniformly coated on the lithium titanate coating by a hot-pressing roller coating process to form a PVDF coating with a thickness of 0.1 μm, thus obtaining a diaphragm-reference electrode. The hot-pressing temperature is 70 °C, the hot-pressing pressure is 3 MPa, and the hot-pressing time is 5 s.

[0067] (2) Place the above-mentioned separator-reference electrode between the positive and negative electrode plates, weld the positive electrode plate to one end of the positive electrode tab, weld the negative electrode plate to one end of the negative electrode tab, and lead out the other end of the positive electrode tab, negative electrode tab and reference electrode tab through the aluminum-plastic film; encapsulate the cell in the aluminum-plastic film, and fill the aluminum-plastic film with electrolyte (1mol / L LiPF6, EC:PC:DMC=1:1:1), and seal the tabs on the aluminum-plastic film with tab adhesive. The length of the tab adhesive is 1cm, the length of the tab sealed inside the battery is 2cm, and the length of the tab exposed outside the battery is 1cm, thus obtaining the three-electrode lithium-ion battery.

[0068] Example 4

[0069] This embodiment provides a three-electrode lithium-ion battery and its preparation method.

[0070] The preparation method is the same as in the example, except that the thickness of the lithium titanate coating in this example is 0.5 μm.

[0071] Example 5

[0072] This embodiment provides a three-electrode lithium-ion battery and its preparation method.

[0073] The preparation method is the same as in the example, except that the thickness of the lithium titanate coating in this example is 5 μm.

[0074] Example 6

[0075] This embodiment provides a three-electrode lithium-ion battery and its preparation method.

[0076] The preparation method is the same as in the example, except that the PVDF coating thickness is 1 μm in this example.

[0077] Comparative Example 1

[0078] This comparative example provides a three-electrode lithium-ion battery and its preparation method.

[0079] The preparation method is the same as in Example 1. The difference is that in this comparative example, copper wire plated with lithium is used as the reference electrode. The reference electrode is placed between the positive and negative electrodes, and a PE separator is used to separate the positive electrode from the reference electrode and the negative electrode from the reference electrode.

[0080] Performance testing

[0081] 1. Heat shrinkage experiments were conducted on the diaphragms prepared in the examples and comparative examples.

[0082] The test conditions for baking shrinkage rate are as follows: cut the diaphragm-reference electrode or diaphragm into a square with a side length of 50 mm, bake it in an oven for 1 hour and then let it cool naturally. After cooling to room temperature, use CCD to measure the diaphragm size and calculate the thermal shrinkage rate of the diaphragm.

[0083] 2. The reference electrode of the three-electrode lithium-ion battery prepared in the examples and comparative examples was activated by charging at 20 μA for 5 h, using 1C / 1C cycling, and the lifetime of the reference electrode was monitored.

[0084] The results of the heat shrinkage experiment and the lifetime of the reference electrode are shown in Table 1 below:

[0085] Table 1

[0086] project Shrinkage rate / % Reference electrode operating time / h Example 1 1.6 2515 Example 2 1.7 2550 Example 3 1.4 1500 Example 4 2.9 1470 Example 5 2 2300 Example 6 3.7 790 Comparative Example 1 5.5 150

[0087] As can be seen from the embodiments in Table 1, the thermal shrinkage rate of the separator provided by the present invention can be as low as 1.4% when baked at 130°C, and the actual working time of the reference electrode can be as long as 2500 hours or more. This indicates that the three-electrode lithium-ion battery prepared by the present invention can effectively improve the thermal shrinkage problem of the separator and enhance the safety and stability of the lithium-ion battery, and can also effectively improve the lifespan of the reference electrode.

[0088] The comparison between the examples and comparative examples further demonstrates that the three-electrode lithium-ion battery prepared by the present invention can effectively improve the thermal shrinkage problem of the separator, enhance the safety and stability of lithium-ion batteries, and effectively improve the lifespan of the reference electrode.

[0089] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0090] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-electrode lithium-ion battery, characterized in that, The three-electrode lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, a separator, and a reference electrode. The reference electrode includes a lithium titanate coating and a PVDF coating. The diaphragm is placed between the positive electrode and the negative electrode; The lithium titanate coating is provided on either side of the diaphragm surface.

2. The three-electrode lithium-ion battery according to claim 1, characterized in that, The reference electrode further includes a reference tab, which comprises an aluminum substrate, a lithium titanate coating, and a PVDF coating, wherein the aluminum substrate is connected to the diaphragm.

3. The three-electrode lithium-ion battery according to claim 1 or 2, characterized in that, The thickness of the lithium titanate coating is 0.5-5 μm; And / or, the thickness of the PVDF coating is 0.1-3 μm.

4. The three-electrode lithium-ion battery according to claim 1 or 2, characterized in that, The lithium titanate coating comprises 75-85 wt% lithium titanate, 8-13 wt% conductive agent, and 8-13 wt% binder.

5. The three-electrode lithium-ion battery according to claim 2, characterized in that, The width of the aluminum substrate is 0.5-1cm.

6. The method for preparing a three-electrode lithium-ion battery according to any one of claims 1-5, characterized in that, The preparation method includes: (1) Lithium titanate slurry and PVDF slurry are sequentially coated on the diaphragm to obtain a diaphragm-reference electrode; (2) The positive electrode, the separator-reference electrode, and the negative electrode are stacked, packaged, and filled with electrolyte to obtain the three-electrode lithium-ion battery.

7. The preparation method according to claim 6, characterized in that, Step (1) is as follows: connecting the diaphragm to the aluminum substrate, simultaneously coating the diaphragm and the aluminum substrate with lithium titanate slurry to obtain a lithium titanate coating, and coating the lithium titanate coating with PVDF slurry to obtain a diaphragm-reference electrode.

8. The preparation method according to claim 7, characterized in that, The thickness of the lithium titanate coating is 0.5-5 μm; And / or, the thickness of the PVDF coating is 0.1-3 μm; And / or, the PVDF slurry is coated by hot-press coating.

9. The preparation method according to claim 8, characterized in that, The hot-pressing temperature for the hot-press coating is 70-120℃; And / or, the hot-pressing pressure of the hot-press coating is 0.5-3 MPa; And / or, the hot pressing time for the hot pressing coating is 5-50s.

10. A vehicle, characterized in that, The vehicle includes a three-electrode lithium-ion battery as described in any one of claims 1-5 or a three-electrode lithium-ion battery prepared by the preparation method described in any one of claims 6-9.

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