Reference electrode for all-solid-state battery and all-solid-state battery including reference electrode

Abstract

The application relates to a reference electrode for a full solid-state battery and a full solid-state battery comprising the reference electrode, the reference electrode comprising a reference current collector, a sealing adhesive layer, a reference active material layer and an insulating layer; the reference current collector comprises a tail part, a sealing part and an overhang part used for being arranged in an overhang space of the full solid-state battery, the overhang space being a space formed by being clamped by a positive electrode layer of the full solid-state battery and solid-state electrolyte layers located on the upper and lower sides of the positive electrode layer; the sealing adhesive layer is arranged on the sealing part; the reference active material layer and the insulating layer are arranged on the overhang part, and the reference active material layer is located between the sealing adhesive layer and the insulating layer. The application can solve the problems of poor service life, stability and yield of the reference electrode in the related art.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a reference electrode for an all-solid-state battery and an all-solid-state battery including the reference electrode. Background Technology

[0002] In recent years, with the rapid development of new energy vehicles and distributed energy storage, increasingly higher demands have been placed on the energy density and safety of lithium-ion batteries. Improving battery energy density by optimizing battery shape and reducing the proportion of inactive materials has approached the physical limits of this strategy. Further improvements in battery energy density and safety require the use of positive and negative electrode materials with higher specific capacity and novel battery structures. All-solid-state lithium batteries, combining high energy density and high safety, are considered the mainstream technology for next-generation power batteries.

[0003] Solid-state batteries can be categorized into two types based on their technology: semi-solid-state and all-solid-state. All-solid-state batteries are rechargeable batteries where the battery structure contains no electrolyte, and all materials exist in solid form. Currently, the solid electrolytes used are primarily sulfides. All-solid-state batteries exhibit excellent stability because, due to the use of solid electrolytes, electrolyte evaporation or leakage will not occur even if the casing is damaged. Furthermore, the electrolyte's good temperature and pressure tolerance allows it to operate normally in extreme external environments with high heat and high pressure.

[0004] A typical all-solid-state battery cell consists of a positive electrode, an electrolyte membrane, and a negative electrode. The electrolyte membrane isolates electrons while allowing ions to pass through. The negative electrode uses a low-potential material and serves as both the counter electrode and the reference electrode, while the positive electrode uses a high-potential material as the working electrode. This means that in a dual-electrode battery cell, only the voltage and resistance of the entire cell (comprising the positive and negative electrodes) can be measured; the electrical characteristics of individual electrodes (positive and negative) cannot be analyzed. This presents challenges for studying material properties or investigating failure behavior.

[0005] A reference electrode is an auxiliary electrode introduced into a typical two-electrode battery cell to provide information such as potential and resistance for the positive and negative electrodes. In a battery cell containing a reference electrode, the voltage, resistance, and other characteristics of the positive and negative electrodes can be measured by connecting them separately to the reference electrode. This also means that the voltage and resistance information of the entire cell can be decoupled to the voltage and resistance of individual electrodes through the reference electrode, which is very important for studying and analyzing the electrical characteristics of battery systems.

[0006] Currently, battery structures containing reference electrodes are commonly found in liquid batteries.

[0007] In solid-state batteries, the battery voltage is the voltage difference between the positive and negative electrodes. Without introducing a third electrode as a reference electrode into the battery cell, it's impossible to accurately assess the voltage and resistance changes at each electrode, leading to an inability to accurately evaluate the characteristics of the active materials or the reasons for their performance failure. However, all-solid-state batteries consist entirely of solid-solid interfaces, making the introduction of a reference electrode much more challenging than in liquid-state batteries. It's crucial to ensure the reference electrode's lifespan and stability, while also guaranteeing that it doesn't interfere with the operation of the solid-state battery itself, and simultaneously ensuring a high success rate in its fabrication. Summary of the Invention

[0008] This application provides a reference electrode for all-solid-state batteries and an all-solid-state battery containing the reference electrode, in order to solve the problems of poor reference electrode lifespan, stability, and yield in related technologies.

[0009] In a first aspect, a reference electrode for an all-solid-state battery is provided, the reference electrode comprising a reference current collector, a sealing adhesive layer, a reference active material layer, and an insulating layer;

[0010] The reference current collector includes a tail section, a sealing section, and an overhang section for arrangement in the overhang space of the all-solid-state battery, which are connected in sequence. The overhang space is a space formed by the positive electrode layer of the all-solid-state battery and the solid electrolyte layers located on the upper and lower sides of the positive electrode layer.

[0011] The sealing adhesive layer is provided on the sealing section;

[0012] The reference active material layer and the insulating layer are disposed on the overhang section, and the reference active material layer is located between the sealing adhesive layer and the insulating layer.

[0013] In some embodiments, the reference current collector is made of copper foil, steel foil, titanium foil, stainless steel, or nickel foil;

[0014] And / or, the reference current collector is used to insert the overhang segment into the overhang space with a length of 0.1mm to 3mm, a thickness of 4μm to 100μm, and a width of 10mm to 100mm.

[0015] In some embodiments, the sealing adhesive layer is made of PP plastic, PE plastic, or PI plastic;

[0016] And / or, the length of the sealing adhesive layer is 2mm to 10mm and the thickness is 1mm to 3mm.

[0017] In some embodiments, the reference active material layer is made of lithium metal or a lithium-indium alloy;

[0018] And / or, the length of the reference active material layer is 0.1 mm to 3 mm, and the thickness is 1 μm to 100 μm.

[0019] In some embodiments, the insulating layer is made of one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and PVDF-HFP, or the insulating layer is a filler layer.

[0020] And / or, the length of the insulating layer is 0.1 mm to 3 mm, and the thickness is 1 μm to 100 μm.

[0021] In a second aspect, an all-solid-state battery including a reference electrode is provided, comprising a reference electrode for an all-solid-state battery as described above, an outer packaging, and a negative electrode layer, a positive electrode layer, a solid electrolyte layer, and a filler layer located within the outer packaging;

[0022] The negative electrode layer and the positive electrode layer are stacked alternately, and a solid electrolyte layer is disposed between adjacent negative electrode layers and positive electrode layers to form an overhang space.

[0023] At least one of the overhang spaces has the reference electrode inserted through the outer packaging, and the remaining overhang spaces are provided with the filling layer.

[0024] In some embodiments, the sidewall corresponding to the long side of the outer packaging is the first sidewall, and the sidewall corresponding to the wide side is the second sidewall. The reference electrode is located on the first sidewall, or the reference electrode is located on the second sidewall, or at least one of the reference electrodes is located on the first sidewall and at least one of the reference electrodes is located on the second sidewall.

[0025] And / or, the reference electrodes are provided in multiples, with at least two of the reference electrodes located in the overhang space of the same positive electrode layer, or at least two of the reference electrodes located in the overhang space of different positive electrode layers.

[0026] In some embodiments, the outer packaging includes a heat-sealing layer, an aluminum foil layer, and a nylon layer stacked from the inside out;

[0027] And / or, the thickness of the outer packaging is 50μm to 200μm.

[0028] In some embodiments, the solid electrolyte layer is made of an oxide electrolyte or a sulfide electrolyte.

[0029] In some embodiments, the filler layer is made of oxide ceramic or solid electrolyte material;

[0030] And / or, the thickness of the filling layer is 100μm to 300μm.

[0031] In some embodiments, the oxide ceramic includes one or more of aluminum oxide (Al2O3), boehmite (AlOOH), magnesium oxide (MgO), and calcium oxide (CaO).

[0032] In some embodiments, the solid electrolyte material is an oxide electrolyte or a sulfide electrolyte.

[0033] In some embodiments, the thickness of the negative electrode layer is 5 μm to 300 μm;

[0034] The thickness of the positive electrode layer is 5μm to 300μm;

[0035] The length of the negative electrode layer is greater than the length of the positive electrode layer, and the length difference between the negative electrode layer and the positive electrode layer is 1mm to 6mm;

[0036] The width of the negative electrode layer is greater than the width of the positive electrode layer, and the width difference between the negative electrode layer and the positive electrode layer is 1mm to 6mm.

[0037] Thirdly, a method for preparing a reference electrode for an all-solid-state battery as described in any of the above-mentioned embodiments is provided, comprising:

[0038] Based on the dimensions of the overhang space, determine the dimensions of the tail, sealing section, and overhang section of the reference current collector;

[0039] A melt extruder is used to extrude the reference active material to the overhang section to form a reference active material layer. The nozzle diameter of the melt extruder is 50μm to 200μm, the nozzle temperature is 185℃ to 200℃, which is higher than the melting point of the reference active material, the oxygen content in the cavity of the melt extruder is ≤10ppm, the water vapor content is ≤5ppm, and the cavity temperature is 25℃ to 30℃.

[0040] The insulating slurry is applied to the end of the overhang section using either a slurry coating method or a micro-droplet spray molding method to form an insulating layer.

[0041] The sealing adhesive is applied to the sealing section using a hot melt coating method or a melt extrusion molding method to form a sealing adhesive layer.

[0042] The beneficial effects of the technical solution provided in this application include:

[0043] This application utilizes the overhang space created by the negative-to-positive overhang design of solid-state batteries to install a reference electrode. This design avoids inserting the reference electrode between the separator and electrodes inside the cell, thus preventing any increase in cell thickness. Since the reference electrode is located in the overhang space, it can directly contact the reference active material layer and the solid electrolyte layer, having virtually no impact on the original cell structure. Shortening the distance between the reference electrode and the negative and positive electrode layers effectively improves the accuracy of potential and resistance measurements. Furthermore, the reference electrode is inserted into the overhang space like a filler layer, simplifying installation. The design only requires a window in the outer packaging for insertion, having virtually no impact on the original battery structure. This simpler design significantly increases the success rate of reference electrode fabrication. The reference electrode is isostatically molded integrally with the cell in the overhang space, improving its structural stability and sealing, effectively enhancing its structural stability and lifespan. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic cross-sectional view of an all-solid-state battery provided in an embodiment of this application;

[0046] Figure 2 This is a side view of the reference electrode provided in an embodiment of this application;

[0047] Figure 3 This is a schematic diagram of the top of the reference electrode provided in an embodiment of this application;

[0048] Figure 4 This is a schematic diagram of the top of the reference electrode arranged on the side of an all-solid-state battery according to an embodiment of this application;

[0049] Figure 5 This is a schematic diagram of the top of the reference electrode arranged on the opposite side of the tab of the all-solid-state battery provided in an embodiment of this application;

[0050] Figure 6 This is a schematic cross-sectional view of a dual-reference electrode all-solid-state battery provided in an embodiment of this application;

[0051] Figure 7 This is a schematic cross-sectional view of a three-reference electrode all-solid-state battery provided in an embodiment of this application;

[0052] Figure 8 A schematic diagram of EIS and voltage testing of the reference electrode provided in the embodiments of this application;

[0053] Figure 9 This is the voltage curve detected using a reference electrode in Embodiment 6 of this application;

[0054] Figure 10 This refers to the use of a reference electrode to detect the negative electrode voltage curve during cycling in Embodiment 7 of this application.

[0055] Figure 11 This refers to the use of a reference electrode to detect EIS impedance data in Embodiment 8 of this application;

[0056] Figure 12 This is the EIS impedance data obtained by detecting the positive electrode relaxation for 10 hours under high voltage using a reference electrode in Example 9 of this application.

[0057] In the diagram: 10, solid electrolyte layer; 20, negative electrode layer; 21, negative electrode current collector; 30, positive electrode layer; 31, positive electrode current collector; 40, reference electrode; 41, reference current collector; 411, tail section; 412, sealing section; 413, overhang section; 42, sealing adhesive layer; 43, reference active material layer; 44, insulating layer; 50, filler layer; 60, outer packaging. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0059] See Figure 1 As shown, this application provides an all-solid-state battery including a reference electrode, which includes a reference electrode 40, an outer packaging 60, and a negative electrode layer 20, a positive electrode layer 30, a solid electrolyte layer 10, and a filling layer 50 located within the outer packaging 60.

[0060] The negative electrode layer 20 and the positive electrode layer 30 are alternately stacked, and a solid electrolyte layer 10 is disposed between adjacent negative electrode layers 20 and positive electrode layers 30 to form an overhang space. Specifically, an overhang design of negative-enclosing positive is adopted, that is, the length and width of the electrode sheet of the negative electrode layer 20 are greater than the length and width of the electrode sheet of the positive electrode layer 30, and the length and width of the solid electrolyte layer 10 are usually the same as the length and width of the negative electrode layer 20, so that the solid electrolyte layer 10 located at the end of the positive electrode layer 30 and on the upper and lower sides of the positive electrode layer 30 enclose a space, which is the overhang space.

[0061] The outer packaging 60 has a window corresponding to the overhang space. At least one of the overhang spaces has the reference electrode 40 inserted through the window of the outer packaging 60. In order to prevent the cell from short-circuiting during the pressure molding process, the remaining overhang spaces are provided with the filling layer 50.

[0062] See Figure 1 , Figure 2 and Figure 3 As shown, the reference electrode 40 includes a reference current collector 41, a sealing adhesive layer 42, a reference active material layer 43, and an insulating layer 44. The reference current collector 41 includes a tail section 411, a sealing section 412, and an overhang section 413 arranged in the overhang space, which are connected in sequence. The sealing adhesive layer 42 is disposed on the sealing section 412. The reference active material layer 43 and the insulating layer 44 are disposed on the overhang section 413, and the reference active material layer 43 is located between the sealing adhesive layer 42 and the insulating layer 44.

[0063] When the reference electrode 40 is inserted into the overhang space, the tail 411 is located outside the outer packaging 60 and is used to connect with the positive and negative electrodes to form a circuit.

[0064] The sealing adhesive layer 42 covers the surface of the sealing section 412 and is located at the window of the outer packaging 60. When the soft-pack battery is sealed, the reference current collector 41 and the cell electrode core are heat-sealed and fixed together with the soft-pack battery outer packaging 60.

[0065] The reference current collector 41 is coated with a reference active material layer 43, which is in direct contact with the solid electrolyte layer 10. The overall thickness of the reference current collector 41 and the reference active material layer 43 is comparable to the thickness of the positive electrode layer 30 after the cell is formed and compressed.

[0066] The front end of the reference current collector 41 abuts against, covers, or wraps the insulating layer 44 to achieve insulation of the positive electrode layer 30.

[0067] The reference electrode 40 in this embodiment is an electrode that does not substantially contribute to the battery capacity of the all-solid-state battery. Using the reference electrode 40 as a reference, the positive and negative electrode potentials and the EIS impedance spectrum can be measured separately. One end of the reference electrode 40 is disposed in the overhang space between the positive and negative electrode plates. The other end of the reference electrode 40 is exposed outside the battery cell.

[0068] According to the design of this application, the positive and negative electrodes can be connected to a reference electrode respectively, enabling the measurement of the resistance and voltage of the positive and negative electrodes. This design utilizes the overhang space formed by the negative-to-positive overhang design of the solid-state battery to install the reference electrode. This ensures that the reference electrode is not inserted between the separator and electrode plates inside the cell, thus avoiding any additional increase in cell thickness. Since the reference electrode is not inserted between the separator and electrode plates inside the cell but is located in the overhang space, it can directly contact the reference active material layer 43 and the solid electrolyte layer 10, having virtually no impact on the original cell structure. Shortening the distance between the reference electrode and the negative electrode layer 20 and the positive electrode layer 30 effectively improves the measurement accuracy of potential and resistance. Furthermore, the reference electrode of this application is inserted into the overhang space like the filling layer 50, simplifying installation. The design only requires a window on the outer packaging 60 for insertion, having virtually no impact on the original battery structure. This simpler structural design significantly increases the success rate of reference electrode fabrication. The reference electrode is integrally formed with the battery cell in the overhang space under isostatic pressing, which improves the structural stability and sealing of the reference electrode, and can effectively improve the structural stability and lifespan of the reference electrode.

[0069] It should be noted that the applicant also performed positive-to-negative overhang formation and used a reference electrode for testing. However, it was found that positive-to-negative overhang caused lithium plating, which seriously affected the battery performance.

[0070] The reference current collector 41 is the substrate of the reference electrode 40. The reference current collector 41 is made of various common metal foils, such as copper foil, steel foil, titanium foil, stainless steel, and nickel foil. The overhang section 413 of the reference current collector 41 is located within the overhang space. This application uses foil as the current collector for the reference electrode. Compared to using traditional copper wire as the current collector, the flat structure of the foil increases the structural stability during cell packaging. Simultaneously, the flat structure better supports the positive and negative electrodes in the overhang space, reducing electrode breakage during cell pressing and increasing the success rate of cell manufacturing.

[0071] The aforementioned solid-state battery typically uses alternating layers of negative electrode 20 and positive electrode 30 to form a square shape, such as a cube (including a cuboid or a cubic shape). Of course, it can also be designed into other shapes according to actual needs. This application uses the commonly used cube shape as an example for illustration.

[0072] See Figure 1 As shown, a coordinate system is established with the stacking direction of the negative electrode layer 20 and the positive electrode layer 30 as the z-direction (the thickness direction of the cubic solid-state battery), and one of the length and width directions of the cubic solid-state battery as the x-direction and the other as the y-direction.

[0073] Combination Figure 1 and Figure 4 In this application, a coordinate system is established with the thickness direction of the cubic solid-state battery as the z-direction, the width direction as the x-direction, and the length direction as the y-direction for illustration.

[0074] If inserted into the overhang space along the x-direction, the length of the overhang segment 413 along the x-direction is less than 0.5 times the width difference between the negative electrode layer 20 and the positive electrode layer 30 in the x-direction, to reserve space for the insulating layer 44. It should be noted that the center lines of the negative electrode layer 20 and the positive electrode layer 30 are aligned in the x-direction at this time. Generally, the center lines of the negative electrode layer 20 and the positive electrode layer 30 are aligned in the x-direction and also in the y-direction, so that the positive electrode layer 30 is located exactly at the center of the negative electrode layer 20, with overhang spaces around the edges of the positive electrode layer 30. The filling layer 50 is used for isolation and insulation. The purpose of this arrangement is to prevent short circuits between the positive electrode layer 30 and the negative electrode layer 20. However, if the short circuit problem can be solved, one edge of the positive electrode layer 30 can be aligned with one edge of the negative electrode layer 20, so that there is no need for overhang spaces around the edges of the positive electrode layer 30. For example, the edge in the x-direction can be aligned. In this case, the length of the overhang segment 413 along the x-direction is less than the width difference between the negative electrode layer 20 and the positive electrode layer 30 in the x-direction.

[0075] Consistent with the logic of inserting into the overhang space in the x direction, if inserted into the overhang space in the y direction, then the length of the overhang segment 413 in the y direction is less than 0.5 times the length difference between the negative electrode layer 20 and the positive electrode layer 30 in the y direction, so as to reserve space for the insulating layer 44. Regarding the alignment, please refer to the logic of inserting into the overhang space in the x direction, which will not be repeated here.

[0076] As an example, the reference current collector 41 is used to insert the overhang segment 413 within the overhang space for a length (in terms of...). Figure 2 , Figure 3 , Figure 4For example, the length (the dimension in the x-direction) is 0.1mm to 3mm, and the thickness (in words) is... Figure 2 , Figure 3 , Figure 4 For example, the thickness (the dimension in the z-direction) is 4μm to 100μm, and the width (in words) is... Figure 2 , Figure 3 , Figure 4 For example, the width (the dimension in the y-direction) is 10mm to 100mm.

[0077] See Figure 1 , Figure 2 and Figure 3 As shown, the sealing adhesive layer 42 covers at least a portion of the sealing section 412, ensuring a seal at least at the reference electrode and guaranteeing that the battery is well isolated from air. The main material is PP plastic, PE plastic, or PI plastic.

[0078] The sealing adhesive layer 42 has a length of 2mm to 10mm along the X direction and a thickness of 1mm to 3mm along the Z direction. It can be seen that a sealing adhesive layer 42 is provided on both the upper and lower sides of the reference current collector 41, and the thickness here is the thickness on one side.

[0079] See Figure 1 , Figure 2 and Figure 3 As shown, the reference active material layer 43 covers the overhang section 413. The reference active material layer 43 has a reference potential and needs to be in close contact with the solid electrolyte layer 10 and the reference current collector 41, without reacting with them. The positive electrode potential is the difference between the potential of the reference active material layer 43 and the potential of the positive electrode layer 30, and the negative electrode potential is the difference between the potential of the reference active material layer 43 and the potential of the negative electrode layer 20.

[0080] The reference active material layer 43 can have a thickness along the z-direction of, for example, 1 μm to 100 μm. The specific thickness matches the thickness of the positive electrode layer and the reference current collector 41. For example, the thickness of the reference active material layer 43 along the z-direction = (thickness of the positive electrode layer along the z-direction - thickness of the reference current collector 41 along the z-direction) / 2. The reference active material layer 43 can have a length along the x-direction of, for example, 0.1 mm to 3 mm. The specific dimensions match the length of the insulating layer and the dimensions of the overhang space. For example, the length of the reference active material layer 43 along the x-direction = overhang space length - length of the insulating layer 44 along the x-direction. Furthermore, a gap can exist between the insulating layer 44 and the reference active material layer 43. The reference active material layer 43 contains active materials, primarily including metallic lithium and lithium-indium alloys.

[0081] See Figure 1 , Figure 2 and Figure 3 As shown, the insulating layer 44 covers the overhang section 413 to prevent short circuits between the reference current collector 41 and the positive electrode layer 30. The insulating layer can have a thickness of, for example, 1 μm to 100 μm along the z-direction, specifically matched to the thickness of the positive electrode layer and the reference current collector; for example, the thickness of the insulating layer along the z-direction = (the thickness of the positive electrode layer along the z-direction - the thickness of the reference current collector 41 along the z-direction) / 2. The insulating layer 44 can be formed by dip coating, and its thickness also takes into account ease of fabrication. The insulating layer 44 can have a length of, for example, 0.1 mm to 3 mm along the x-direction, specifically matched to the dimensions of the reference active material layer 43 and the overhang space; for example, the length of the insulating layer along the x-direction = the length of the overhang space - the length of the reference active material layer 43 along the x-direction. The insulating layer 44 can be made substantially of an insulating material, for example, one or more combinations of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and PVDF-HFP.

[0082] In addition, the insulating layer can also be a filler layer 50 to isolate the reference electrode from the positive electrode layer 30. That is, the filler layer 50 is smaller in the x-direction than the filler layer 50 at other locations, so that the reference current collector 41 can abut against the filler layer 50, thereby preventing a short circuit between the reference current collector 41 and the positive electrode layer 30.

[0083] As mentioned above, there is usually an overhang space around the edges of the positive electrode layer 30. The sidewall corresponding to the long side of the outer packaging 60 is defined as the first sidewall, and the sidewall corresponding to the wide side is defined as the second sidewall. In this application, the arrangement position of the reference electrode 40 can be flexibly set.

[0084] For example, as an example, the reference electrode 40 may be located on the first sidewall, see [reference]. Figure 4 As shown, the reference electrode 40 is inserted into the overhang space along the x-direction.

[0085] For example, as an example, the reference electrode 40 may be located on the second sidewall, see [reference]. Figure 5 As shown, the reference electrode 40 is inserted into the overhang space along the y-direction.

[0086] For example, as an example, at least one of the reference electrodes 40 is located on the first sidewall and at least one of the reference electrodes 40 is located on the second sidewall, in which case one of the reference electrodes 40 is inserted into the overhang space along the x-direction and the other reference electrode 40 is inserted into the overhang space along the y-direction.

[0087] Furthermore, in this application, the number of reference electrodes 40 can be set according to actual needs.

[0088] For example, as an example, multiple reference electrodes 40 are provided, with at least two reference electrodes 40 located in the overhang space of the same positive electrode layer 30, see [link to relevant documentation]. Figure 6 As shown, the two reference electrodes 40 are inserted along the x-direction into the overhang space of the same positive electrode layer 30. In fact, the two reference electrodes 40 can also be inserted along the y-direction into the overhang space of the same positive electrode layer 30, or one of the two reference electrodes 40 can be inserted along the x-direction and the other along the y-direction into the overhang space of the same positive electrode layer 30.

[0089] For example, as an example, at least two of the reference electrodes 40 are located in the overhang space of different positive electrode layers 30, such as Figure 7 As shown, there are three reference electrodes 40, all of which are located in the overhang space of different positive electrode layers 30.

[0090] A single all-solid-state battery may contain only one reference electrode 40 or multiple reference electrodes 40. Multiple reference electrodes 40 may use different active materials as references. For example, lithium metal may be used as the reference active material layer 43 of one reference electrode 40, and lithium-indium alloy may be used as the reference active material layer 43 of another reference electrode 40.

[0091] The battery's outer packaging 60 uses an aluminum-plastic film outer packaging for soft-pack batteries. Its structure includes a heat-sealing layer, an aluminum foil layer, and a nylon layer stacked from the inside out.

[0092] The nylon layer can be made of polyamide-based nylon, and a PET layer can be added to enhance its mechanical properties; the aluminum foil layer uses an oxide film to prevent moisture penetration; the heat-sealing layer is generally made of cast polypropylene (CPP) or modified polypropylene (MPP), and its function is to seal the battery cell and prevent electrolyte leakage from corroding the aluminum foil. The thickness of the aluminum-plastic film in the z-direction is generally 50μm to 200μm.

[0093] The solid electrolyte layer 10 is primarily made of a solid electrolyte material. The solid electrolyte layer 10 may also contain, for example, a binder. There are no particular limitations on the solid electrolyte material. For example, the solid electrolyte material can be in a glassy state or a crystalline state. The solid electrolyte material can be an oxide electrolyte or a sulfide electrolyte. The oxide solid electrolyte is selected from Li. 1+x1 Al x1 Ti 2-x1 (PO4)3 (LATP electrolyte), Li 7-x2 La3Zr 2-x2 Ta x2 O 12(LLZTO electrolyte) or Li 3x3 La 2 / 3-x3 TiO3 (LLTO electrolyte), in which... x The value of 1 ranges from 0.3 to 0.5. x2 The value ranges from 0.2 to 1. x3 The value ranges from 0 to 0.16; the sulfide solid electrolyte is selected from Li 10 GeP2S 12 Li3PS4, Li7P3S 11 Or Li6PS5Cl. In subsequent embodiments, the solid electrolyte will be referred to simply as SE. There are no particular limitations on the binder contained in the solid electrolyte layer 10. The binder may be one or a combination of polyisobutylene (PIB), styrene-butadiene-styrene block copolymer (SEBS), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and tetrafluoroethylene (PTFE).

[0094] See Figure 1 As shown, the negative electrode layer 20 is in contact with the solid electrolyte layer 10. The negative electrode layer 20 includes a negative electrode current collector 21 and a negative electrode active material layer located on the surface of the negative electrode current collector 21. The negative electrode current collector can be made of copper foil, steel foil, titanium foil, stainless steel, nickel foil, etc., with copper foil being preferred. The negative electrode layer 20 can have a thickness along the z-direction of, for example, 5 μm to 300 μm. The negative electrode active material layer is mainly made of negative electrode active material, and the proportion of negative electrode active material can be 50% to 100%. In addition to the negative electrode active material, the negative electrode active material layer can also contain, for example, conductive materials, solid electrolyte materials, binders, etc. The negative electrode active material is one or more of graphite, silicon oxide, silicon, silicon-based alloys, lithium metal, lithium-magnesium alloys, lithium-tin alloys, lithium-zinc alloys, and lithium-indium alloys. The conductive material can be one or more of Super-P, acetylene black, vapor-grown carbon fiber (VGCF), and carbon nanotubes (CNTs). The binder can be one or a combination of PIB, SEBS, PAA, SBR, PVDF, PVDF-HFP, and PTFE. The solid electrolyte material used in the negative electrode active material layer can be an oxide electrolyte or a sulfide electrolyte. The oxide solid electrolyte is selected from Li. 1+x1 Al x1 Ti 2-x1 (PO4)3 (LATP electrolyte), Li 7-x2 La3Zr 2-x2 Ta x2 O 12 (LLZTO electrolyte) or Li 3x3 La 2 / 3-x3 TiO3 (LLTO electrolyte), in which...x The value of 1 ranges from 0.3 to 0.5. x2 The value ranges from 0.2 to 1. x3 The value ranges from 0 to 0.16; the sulfide solid electrolyte is selected from Li 10 GeP2S 12 Li3PS4, Li7P3S 11 Or Li6PS5Cl.

[0095] The length of the negative electrode layer 20 is greater than the length of the positive electrode layer 30, and the length difference between the negative electrode layer 20 and the positive electrode layer 30 is 1mm to 6mm.

[0096] The width of the negative electrode layer 20 is greater than the width of the positive electrode layer 30, and the width difference between the negative electrode layer 20 and the positive electrode layer 30 is 1mm to 6mm.

[0097] The positive electrode layer 30 is in contact with the solid electrolyte layer 10. The positive electrode layer 30 includes a positive electrode current collector 31 and a positive electrode active material layer located on the surface of the positive electrode current collector 31. The positive electrode current collector can be copper foil, steel foil, titanium foil, stainless steel, nickel foil, etc., preferably aluminum foil. The positive electrode layer 30 can have a thickness along the z-direction of, for example, 5 μm to 300 μm. The positive electrode active material layer is mainly made of positive electrode active material, and the proportion of positive electrode active material can be 50% to 100%. In addition to the positive electrode active material, the positive electrode active material layer may also include, for example, conductive materials, solid electrolyte materials, binders, etc. The positive electrode active material is an NCM series positive electrode active material, which can be selected from LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.2 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2 may be used. The conductive material may be one or more of Super-P, acetylene black, vapor-grown carbon fiber (VGCF), and carbon nanotubes (CNTs). The binder may be one or more of PIB, SEBS, PAA, SBR, PVDF, PVDF-HFP, and PTFE. The solid electrolyte material used in the positive electrode active material layer may be an oxide electrolyte or a sulfide electrolyte. The oxide solid electrolyte is selected from Li. 1+x1 Alx1 Ti 2-x1 (PO4)3 (LATP electrolyte), Li 7-x2 La3Zr 2-x2 Ta x2 O 12 (LLZTO electrolyte) or Li 3x3 La 2 / 3-x3 TiO3 (LLTO electrolyte), in which... x The value of 1 ranges from 0.3 to 0.5. x2 The value ranges from 0.2 to 1. x3 The value ranges from 0 to 0.16; the sulfide solid electrolyte is selected from Li 10 GeP2S 12 Li3PS4, Li7P3S 11 Or Li6PS5Cl.

[0098] See Figure 1 As shown, the function of the filler layer 50 is to prevent the Overhang space from collapsing after isostatic pressing, which would cause the positive electrode layer and the negative electrode layer to come into contact, leading to a short circuit in the battery. The filler layer 50 can be made primarily of oxide ceramics or solid electrolyte materials, and may also contain, for example, binders. Oxide ceramics include alumina (Al2O3), boehmite (AlOOH), magnesium oxide (MgO), calcium oxide (CaO), etc. The electrolyte may contain materials exemplified, such as the solid electrolyte material in the solid electrolyte layer 10. The thickness of the filler layer 50 along the z-direction is 100 μm to 300 μm, specifically the same as the thickness of the pressed positive electrode layer. The length of the filler layer 50 along the x-direction = (width of the negative electrode layer 20 in the x-direction - width of the positive electrode layer 30 in the x-direction) / 2.

[0099] The present application will be described in detail below through some embodiments and comparative examples.

[0100] A coordinate system is established with the thickness direction of the cubic solid-state battery as the z-direction, the width direction as the x-direction, and the length direction as the y-direction for explanation.

[0101] Example 1:

[0102] ① Reference electrode fabrication

[0103] 1. Reference current collector pretreatment

[0104] Copper foil was selected as the reference current collector for the reference electrode, and the copper foil thickness was 50 μm.

[0105] The design incorporates an integrated structure of "tail + sealing section + overhang section" cut from copper foil according to the overhang space dimensions, so that the length in the x direction is 30mm and the length in the y direction is 20mm. The overhang section is 2.5mm long (to accommodate the size difference between the positive and negative electrode layers), the sealing section is 7.5mm long, the tail is 20mm long and 20mm wide.

[0106] Surface cleaning: To ensure full contact between the active material and the current collector of the reference electrode, first use 1000-grit sandpaper to remove the oxide layer on the surface of the current collector, then use 7000-grit sandpaper to polish until the surface roughness Ra≤0.1μm, and finally wipe with anhydrous ethanol 3 times to ensure that there is no oil or oxide impurities. Polishing and cleaning can avoid surface unevenness and foreign matter, which can affect the bonding between the lithium metal layer and the current collector.

[0107] 2. Step-by-step molding process for preparing each functional layer

[0108] The reference active material layer, insulating layer, and sealing adhesive layer of the reference electrode are preferably formed by low-temperature melt molding or 3D printing, which can be precisely adapted to micro-scale manufacturing.

[0109] (1) Forming of the reference active material layer:

[0110] Selection of active material: In this embodiment, 99.99% high-purity lithium metal is selected and low-temperature melt extrusion molding or micro-droplet jet molding is adopted.

[0111] Molding equipment: Low-temperature melt extruder, nozzle diameter 50μm~200μm, suitable for layer thickness 1μm~100μm, the cavity is filled with 99.999% argon gas, oxygen content ≤10ppm, water vapor content ≤5ppm, to prevent lithium oxidation.

[0112] Process parameters: Nozzle temperature 185℃~200℃, slightly higher than the lithium melting point of 180.5℃, to ensure fluidity; cavity temperature 25℃~30℃; layer thickness 5μm~10μm / layer, stacked to an uncompressed thickness of 250μm~260μm (lithium metal has good plastic deformation properties, compressed to 230μm after isostatic pressing, matching the thickness of the positive electrode layer); the forming area is precisely positioned in the overhang section, with a length of 0.1mm~3mm (1mm in this embodiment, reserving space for the insulating layer);

[0113] Post-processing: After molding, cool to room temperature in an inert atmosphere, and gently press the surface of the lithium metal layer with a PTFE soft scraper to ensure a seamless fit with the current collector.

[0114] (2) Insulation layer forming:

[0115] PTFE, PVDF, or PVDF-HFP (PVDF is selected in this embodiment) are used, and slurry coating or micro-droplet spray molding is employed:

[0116] Slurry preparation: Dissolve PVDF in NMP or acetone solvent to prepare an insulating slurry with a solid content of 20% to 30%.

[0117] Molding parameters: injection nozzle diameter 50μm, molding area covers the end of the lithium metal layer away from the sealing section, insulation layer covers the reference current collector with a length of 0.1mm to 3mm (1.5mm in this embodiment) and a thickness of 1μm to 100μm (15μm on one side in this embodiment, and a total thickness of 30μm on both sides, which is adapted to the total thickness of the current collector + insulation layer and the thickness of the positive electrode).

[0118] Curing: For UV-curable PVDF slurry, irradiate with a 365nm UV lamp for 30-60 seconds. After curing, the insulation resistance should be ≥10 Ω. 10 Ω (avoid short circuit with the positive electrode layer).

[0119] (3) Sealing adhesive layer forming:

[0120] PP, PE, or PI (PP is selected in this example) are used, and hot melt lamination or melt extrusion molding is employed:

[0121] Molding parameters: PP wire melt index (190℃ / 2.16kg) 5g / 10min~10g / 10min, nozzle temperature 180℃~220℃, molding area covers the sealing section, thickness 1mm~3mm (1mm on one side in this embodiment), length 2mm~10mm (5mm in this embodiment); apply micro pressure of 0.1MPa~0.2MPa during molding to ensure tight bonding with the current collector (for subsequent heat sealing).

[0122] 3. Pre-assembly and dimensional verification

[0123] The formed "current collector-lithium metal layer-insulating layer-sealing adhesive layer" assembly is pre-assembled in an inert atmosphere. The dimensions of each layer are checked with a laser thickness gauge (error ≤ ±5%), and the overhang length (0.1mm~3mm) is checked with a vernier caliper to ensure the overhang space of the battery is suitable.

[0124] ② Solid-state battery manufacturing

[0125] 1. Preparation of solid electrolyte layer

[0126] Solvent (dodecane), binder (PIB), and SE material were placed in a homogenizing tank at a mass ratio of SE:binder = 98:2. After adding the materials, a mixing (5 min) and homogenization (120 min) were performed to prepare a solid electrolyte slurry. The solid content of the solid electrolyte slurry was controlled to be approximately 54%, and the solid electrolyte slurry was coated onto the surface of aluminum foil. After coating, the solid electrolyte slurry was dried at 80°C for 15 to 30 minutes. After drying, the solid electrolyte layer was dried in a vacuum oven at 120°C for 60 minutes to remove residual solvent, thus preparing a solid electrolyte layer with a thickness of 65 μm before isostatic pressing.

[0127] 2. Fabrication of the negative electrode layer

[0128] Solvent NMP and binder PVDF were placed in a stainless steel homogenizing tank and homogenized for 30 minutes to prepare the adhesive solution. The mass ratio of solvent to binder was 98:2. Silicon anode material, SE, and conductive material were then added, followed by mixing (5 minutes) and homogenization (120 minutes) to prepare the anode slurry. The designed anode active material: SE: conductive material: binder = 70:26:2:2 (mass ratio). The solid content of the anode slurry was controlled to be approximately 43%. The anode slurry was coated on both sides of the copper foil surface. After coating, the anode slurry was dried at 80°C for 15 to 30 minutes. After drying, the anode was further dried in a vacuum oven at 120°C for 60 minutes to remove residual solvent, thus preparing the anode layer. The thickness of the anode layer before isostatic pressing was 35 μm.

[0129] 3. Fabrication of the positive electrode layer

[0130] Solvent (dodecane) and binder (SEBS) were placed in a stainless steel homogenizing tank and homogenized for 30 minutes to prepare the adhesive solution. The mass ratio of solvent to binder was 98:2. LiNi was then added. 0.9 Co 0.05 Mn 0.05 O2 positive electrode material, SE, and conductive material were mixed and stirred once (5 min) and then homogenized (120 min) to prepare the positive electrode slurry. The designed positive electrode active material: SE: conductive material: binder = 70:26:2:2 (mass ratio). The solid content of the negative electrode slurry was controlled to be approximately 58%, and the positive electrode slurry was coated on both sides of the aluminum foil surface. After coating, the positive electrode slurry was dried at 80℃ for 15 to 30 minutes. After drying, the positive electrode sheet was dried in a vacuum oven at 120℃ for 60 minutes to remove residual solvent, thus preparing the positive electrode layer. The thickness of the positive electrode layer before isostatic pressing was 140 μm.

[0131] 4. Overhang Filling Layer Creation

[0132] Solvent (NMP), binder (PVDF), and filler material Al2O3 were placed in a homogenizing tank. The mass ratio of filler material to binder was 98:2. After adding the materials, the mixture was stirred once (5 min) and then homogenized (120 min) to prepare a filler material slurry with a solid content of approximately 54%. The solid electrolyte layer prepared in step 1 and the negative electrode layer prepared in step 2 were subjected to double-sided roll transfer to prepare a negative electrode composite sheet with a two-sided composite electrolyte. Using 3D printing technology, a 2.5 mm filler coating was printed around the negative electrode composite sheet, with a reserved space for the reference electrode. The inner diameter of the filler coating was consistent with the size of the positive electrode layer.

[0133] 5. Cell assembly

[0134] according to Figure 1 and Figure 4 As shown, the pre-assembled reference electrode is inserted into the reserved position in the Overhang space (matching the size of the 3D printed filler layer). The negative electrode composite sheet, positive electrode layer, and reference electrode are then pressed together using an isostatic pressing device at a pressure of 300 MPa for 5 minutes. This ensures that the reference electrode and the cell are integrally formed, and that the lithium metal layer and the solid electrolyte layer are in close contact. This achieves structural compatibility and performance stability between the reference electrode and the cell, avoiding dimensional deviations and interlayer gaps caused by traditional manual bonding. Thus, an all-solid-state battery with a reference electrode has been fabricated.

[0135] Example 2:

[0136] like Figure 5 As shown, the position of the reference electrode is adjusted to the opposite side of the tab, and the fabrication of the rest of the reference electrode and the battery cell remains the same as in Example 1.

[0137] Example 3:

[0138] like Figure 6 As shown, in this embodiment, two reference electrodes are introduced in the same layer, and the fabrication of the remaining reference electrodes and the cell are consistent with those in Embodiment 1.

[0139] Example 4:

[0140] like Figure 7 As shown, in this embodiment, three reference electrodes are introduced in a heterogeneous layer. The fabrication of the remaining reference electrodes and the cell fabrication are consistent with those in Embodiment 1.

[0141] Example 5:

[0142] The active material of the reference electrode was replaced with a lithium-indium alloy, while the rest of the reference electrode fabrication and cell fabrication remained the same as in Example 1.

[0143] Example 6:

[0144] like Figure 8 As shown, using the reference electrode and all-solid-state battery design of Example 1, a voltmeter (V) and an ammeter (A) were connected to the evaluation battery to obtain a three-electrode battery consisting of a negative electrode layer 20, a reference electrode 40, and a positive electrode layer 30. In the three-electrode battery, constant current charge / discharge cycles were performed at a current rate of 0.1C. Here, C is the unit of the current charging rate. At a current rate of 1C, the designed capacity of the battery was discharged within 1 hour. During the charge / discharge cycles, the positive and negative electrode potentials were measured respectively, using the reference electrode 40 as a reference. Figure 9 This graph shows the results of the first test of the positive and negative electrodes at 0.1C charge and discharge potential in this embodiment. From the voltage fitting (positive reference - negative reference) and the measured voltage data of the positive and negative electrodes, it can be seen that the voltage accuracy error is ≤1mV, proving that the reference electrode provided in this application has very high accuracy.

[0145] Among them, positive reference refers to the actual measurement of the 0.1C charge / discharge potential between the positive electrode layer and the reference electrode.

[0146] Negative reference indicates that the actual charge / discharge potential at 0.1C was measured between the negative electrode layer and the reference electrode.

[0147] Positive and negative measurements indicate the actual measurement of the 0.1C charge / discharge potential between the positive and negative electrode layers.

[0148] Positive and negative fitting means fitting the charge and discharge potential at 0.1C between the positive and negative electrode layers.

[0149] Example 7:

[0150] In all-solid-state batteries, there are fewer side reactions and a longer reference electrode lifetime. Using the same reference electrode and voltage testing scheme as in Example 6, the negative electrode voltage variation during cycling was monitored. The results are as follows... Figure 10 As shown, the changes in the positive and negative electrode potentials during the cycle can be observed, and it can be observed when lithium plating occurs. The service life can reach hundreds of hours. It can be found that lithium plating begins to occur in the battery after 21 cycles.

[0151] Example 8:

[0152] like Figure 8As shown, the reference electrode and all-solid-state battery design of Example 1 were used. An electrochemical workstation was connected to the positive and negative electrodes and the reference electrode, respectively. The resistance characteristics of the positive and negative electrodes were studied using electrochemical impedance spectroscopy (EIS). The principle of EIS is to measure the corresponding current or voltage information by providing an AC sinusoidal voltage or current excitation, and then analyze the electrode kinetics through equivalent circuit fitting. Here, a 10mV sinusoidal voltage was used as the excitation, and the test frequency range was 0.01-1MHz. For the first charge cycle of the battery, full-cell and positive and negative half-cell measurements were performed every 10% SOC. The test results are shown below. Figure 11 As shown in the figure, the reference electrode provided in this application can achieve decoupling of the full cell impedance. The accuracy of the fitted resistance (positive reference + negative reference) is ≤1mΩ compared with the measured resistance data of the positive and negative electrodes, proving that the reference electrode provided in this application has very high accuracy.

[0153] Example 9:

[0154] The electrochemical window of the electrolyte cannot perfectly match the operating voltages of the positive and negative electrodes, leading to decomposition side reactions at both electrodes. These decomposition reactions alter the interfacial properties between the active material and the electrolyte, causing changes in impedance. Using the same reference electrode and all-solid-state battery design as in Example 1, and the same EIS testing method as in Example 8, Figure 12 The study demonstrates the change in positive electrode impedance after the full cell was left to rest at 100% SOC for 10 hours. After 10 hours of relaxation at a high voltage (4.30 V), the interfacial impedance, representing side reactions, increased by 36 Ω (60%). This indicates that the high-precision reference electrode provided in this application can be used to study the interfacial characteristics of all-solid-state batteries, meeting various practical applications.

[0155] Example 10:

[0156] Using the reference electrode fabrication process described in Example 1, three sets of reference electrodes were prepared, and their accuracy, potential stability, and other indicators were tested. Dimensional accuracy: lithium metal layer thickness 230±5μm, insulating layer thickness 30±1μm, and overhang length 2.5±0.1mm, all meeting the requirements.

[0157] Potential stability: Using the reference electrode as a reference, the potential difference between the positive electrode and the reference electrode and between the negative electrode and the reference electrode was tested, and the error was ≤1mV (consistent with the accuracy of Example 6).

[0158] Structural stability: After being subjected to 300MPa isostatic pressing, there was no peeling between the layers, and the insulation resistance remained at 1×10⁻⁶. 11 Ω or above;

[0159] Lifespan: After 200 cycles, the reference electrode can still output a stable potential without oxidation failure (superior to the 50-cycle lifespan of traditional manual bonding process).

[0160] Therefore, the reference electrode fabrication process of this application can stably prepare reference electrodes that meet the requirements, thereby improving dimensional accuracy and service life.

[0161] As can be seen from Examples 1-5, the reference electrode scheme proposed in this application has high flexibility, and its arrangement can be flexibly adjusted. Multiple reference electrode designs can also be introduced according to actual needs. As can be seen from Examples 6, 8, and 10, the average voltage fitting error of the reference electrode is ≤1mV, and the impedance fitting error is ≤1mΩ; this indicates that the reference electrode can serve as a quantitative analysis tool for decoupling the voltage and resistance of a full cell. The reason why the reference electrode used in this application has very high accuracy in decoupling the voltage and impedance of a full cell is that the reference electrode only exists as a "voltmeter." The current passing through it during impedance testing at the electrochemical workstation is ≤10PA, and the current passing through it during voltage testing at the test cabinet is ≤2.5uA. Therefore, using the reference electrode to decouple and measure voltage and resistance has a greater accuracy advantage than using a half-cell. Examples 7 and 9 demonstrate the use of the reference electrode for lithium plating monitoring and side reaction impedance characterization, showing the significant role of the reference electrode as a failure analysis tool.

[0162] Comparative Example 1

[0163] Comparative Example 1 employs a scheme in which the reference electrode is directly embedded in the solid electrolyte layer. Specifically, the all-solid-state battery includes a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a reference electrode. The solid electrolyte layer is located between the positive and negative electrode layers. The reference electrode includes a metal wire, an insulating layer, and an active material layer. The metal wire includes a first end, a second end, and a middle portion. Along the length of the metal wire, the first end and the second end are located at both ends of the metal wire, and the middle portion is located between the first end and the second end. The first end is disposed in the solid electrolyte layer, and the insulating layer covers at least a portion of the middle portion. The active material layer covers the first end, and the active material layer contains olivine-type lithium iron phosphate.

[0164] Using the method of Comparative Example 1, the reference electrode was directly embedded in the solid electrolyte layer for reference electrode performance evaluation: the voltage accuracy error was ≥5 mV when compared with the voltage data of the positive and negative electrodes (positive reference - negative reference). However, during the cyclic voltage test, it was found that a short circuit occurred after one cycle, i.e., 20 hours later. In addition, the resistance coupling accuracy was evaluated, and the resistance accuracy error of the "positive reference + negative reference" resistance was ≥100 mΩ compared with the resistance data of the positive and negative electrodes.

[0165] In summary, considering voltage and resistance accuracy and lifespan, the method of directly implanting a reference electrode into the solid electrolyte layer is inferior to the method provided in this application in terms of performance and stability. This is because introducing a reference electrode into the electrolyte layer is akin to introducing a large "foreign defect," which hinders normal ion transport in the electrolyte layer, leading to increased voltage and resistance errors and accelerating short-circuit failure of the solid-state battery.

[0166] As can be seen, this application proposes to implant reference electrodes in the overhang region of the positive and negative electrodes. Compared with Comparative Example 1 and other existing solutions, this shortens the distance between the reference electrode and the negative electrode layer 20 and the positive electrode layer 30, which can effectively improve the measurement accuracy of potential and resistance. The simpler structural design can greatly increase the success rate of reference electrode fabrication.

[0167] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a reference electrode in an all-solid-state battery, characterized in that: The all-solid-state battery is a pouch battery. The all-solid-state battery includes a reference electrode (40) for use in the all-solid-state battery, an outer packaging (60), and a negative electrode layer (20), a positive electrode layer (30), a solid electrolyte layer (10), and a filler layer (50) located in the outer packaging (60). The reference electrode (40) includes a reference current collector (41), a sealing adhesive layer (42), a reference active material layer (43), and an insulating layer (44). The reference current collector (41) includes a tail section (411), a sealing section (412), and an overhang section (413) arranged in the overhang space of the all-solid-state battery, which are connected in sequence. The overhang space is a space formed by the positive electrode layer (30) of the all-solid-state battery and the solid electrolyte layer (10) located on the upper and lower sides of the positive electrode layer (30). The sealing adhesive layer (42) is provided on the sealing section (412) and located at the window of the outer packaging (60). When the soft pack battery is sealed, the reference current collector (41) and the cell electrode core are heat-sealed together with the soft pack battery outer packaging (41). The reference active material layer (43) and the insulating layer (44) are disposed on the overhang section (413), and the reference active material layer (43) is located between the sealing adhesive layer (42) and the insulating layer (44); The negative electrode layer (20) and the positive electrode layer (30) are stacked alternately, and a solid electrolyte layer (10) is provided between adjacent negative electrode layers (20) and positive electrode layers (30) to form an overhang space; At least one of the overhang spaces is fitted with the reference electrode (40) through the outer packaging (60), and the remaining overhang spaces are provided with the filling layer (50). Preparation methods include: Based on the dimensions of the overhang space, determine the dimensions of the tail (411), sealing section (412), and overhang section (413) of the reference current collector (41); A melt extruder is used to extrude the reference active material to the overhang section (413) to form a reference active material layer (43). The nozzle diameter of the melt extruder is 50μm to 200μm, the nozzle temperature is 185℃ to 200℃ and is higher than the melting point of the reference active material. The oxygen content in the cavity of the melt extruder is ≤10ppm, the water vapor content is ≤5ppm, and the cavity temperature is 25℃ to 30℃. An insulating slurry is applied to the end of the overhang section (413) using a slurry coating method to form an insulating layer (44). A hot melt coating method is used to apply sealing adhesive to the sealing section (412) to form a sealing adhesive layer (42).

2. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The reference current collector (41) is made of copper foil, steel foil, titanium foil, stainless steel or nickel foil; And / or, the reference current collector (41) is used to insert the overhang segment (413) in the overhang space with a length of 0.1 mm to 3 mm, a thickness of 4 μm to 100 μm, and a width of 10 mm to 100 mm.

3. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The sealing adhesive layer (42) is made of PP plastic, PE plastic or PI plastic; And / or, the length of the sealing adhesive layer (42) is 2mm to 10mm and the thickness is 1mm to 3mm.

4. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The reference active material layer (43) is made of lithium metal or a lithium-indium alloy; And / or, the length of the reference active material layer (43) is 0.1 mm to 3 mm and the thickness is 1 μm to 100 μm.

5. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The insulating layer (44) is made of one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), or the insulating layer (44) is made of a filler layer (50). And / or, the length of the insulating layer (44) is 0.1 mm to 3 mm and the thickness is 1 μm to 100 μm.

6. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The sidewall corresponding to the long side of the outer packaging (60) is the first sidewall, and the sidewall corresponding to the wide side is the second sidewall. The reference electrode (40) is located on the first sidewall, or the reference electrode (40) is located on the second sidewall, or at least one of the reference electrodes (40) is located on the first sidewall and at least one of the reference electrodes (40) is located on the second sidewall. And / or, the reference electrode (40) is provided in multiple ways, with at least two of the reference electrodes (40) located in the overhang space of the same positive electrode layer (30), or at least two of the reference electrodes (40) located in the overhang space of different positive electrode layers (30).

7. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The outer packaging (60) includes a heat-sealing layer, an aluminum foil layer, and a nylon layer stacked from the inside out; And / or, the thickness of the outer packaging (60) is 50 μm to 200 μm.

8. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The solid electrolyte layer (10) is made of an oxide electrolyte or a sulfide electrolyte.

9. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The filling layer (50) is made of oxide ceramic or solid electrolyte material; And / or, the thickness of the filling layer (50) is 100μm to 300μm.

10. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 9, characterized in that: The oxide ceramics include one or more of aluminum oxide (Al2O3), boehmite (AlOOH), magnesium oxide (MgO), and calcium oxide (CaO).

11. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 9, characterized in that: The solid electrolyte material is an oxide electrolyte or a sulfide electrolyte.

12. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The thickness of the negative electrode layer (20) is 5 μm to 300 μm; The thickness of the positive electrode layer (30) is 5 μm to 300 μm; The length of the negative electrode layer (20) is greater than the length of the positive electrode layer (30), and the length difference between the negative electrode layer (20) and the positive electrode layer (30) is 1 mm to 6 mm. The width of the negative electrode layer (20) is greater than the width of the positive electrode layer (30), and the width difference between the negative electrode layer (20) and the positive electrode layer (30) is 1 mm to 6 mm.

13. The method for preparing the reference electrode of the all-solid-state battery including the reference electrode as described in claim 1, characterized in that: The insulating slurry was applied to the end of the overhang section (413) using a micro-droplet spray molding method to form an insulating layer (44). The sealing adhesive is applied to the sealing section (412) by melt extrusion molding to form a sealing adhesive layer (42).

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