Three-electrode battery, reference electrode, preparation method of reference electrode and electric device

Abstract

The invention provides a three-electrode battery, a reference electrode, a preparation method of the reference electrode and an electric device. The three-electrode battery comprises a positive pole piece, a negative pole piece, an isolating membrane and the reference electrode, the isolating membrane is arranged between the positive pole piece and the negative pole piece; the reference electrode is arranged between the negative pole piece and the isolating membrane, or the reference electrode is arranged between the positive pole piece and the isolating membrane, or the reference electrode is arranged inside the negative pole piece; the reference electrode comprises a metal matrix, a lithium metal layer and an electronic insulation ion transmission layer, the lithium metal layer coats the surface of the metal matrix, and the electronic insulation ion transmission layer coats the surface of the lithium metal layer; the electron insulation ion transport layer comprises an organic polymer matrix, and a lithium alloy and a lithium salt which are positioned in the organic polymer matrix; the lithium alloy is located on the side, close to the lithium metal layer, of the electron insulation ion transport layer. According to the three-electrode battery, the kinetic parameters of the negative pole piece can be accurately tested, and the reference electrode has a long service life.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a three-electrode battery, a reference electrode and a preparation method thereof, and an electrical device. Background Art

[0002] In recent years, as the application scope of lithium-ion batteries has become more and more extensive, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0003] During the design and development phase of lithium-ion batteries, it is necessary to rely on a reference electrode (i.e., the third electrode) to test the kinetic parameters of the negative electrode such as the lithium precipitation window in order to develop a reasonable charge and discharge strategy. However, in traditional three-electrode batteries, the insulating layer outside the reference electrode has poor ion conductivity, low strength, poor flexibility, and poor corrosion resistance; or, two layers of isolation membranes are required in the three-electrode battery, and the reference electrode is set between the two layers of isolation membranes; the above three-electrode battery will affect the accuracy of the reference electrode's kinetic parameter test of the negative electrode, and at the same time shorten the service life of the reference electrode and the three-electrode battery.

[0004] Therefore, the traditional technology still needs to be further improved. Summary of the invention

[0005] The present application is made in view of the above-mentioned problems, and one of its purposes is to provide a three-electrode battery, a reference electrode and a preparation method thereof, and an electrical device. The three-electrode battery can more accurately test the kinetic parameters of the negative electrode plate, and the reference electrode has a longer service life.

[0006] In order to achieve the above-mentioned object, the first aspect of the present application provides a three-electrode battery, including a positive electrode sheet, a negative electrode sheet, a separator and a reference electrode;

[0007] The separator is disposed between the positive electrode sheet and the negative electrode sheet; the reference electrode is disposed between the negative electrode sheet and the separator, or the reference electrode is disposed between the positive electrode sheet and the separator, or the reference electrode is disposed inside the negative electrode sheet;

[0008] The reference electrode includes a metal substrate, a lithium metal layer and an electronic insulating ion transport layer, wherein the lithium metal layer is coated on the surface of the metal substrate, and the electronic insulating ion transport layer is coated on the surface of the lithium metal layer; the electronic insulating ion transport layer includes an organic polymer substrate and a lithium alloy and a lithium salt located in the organic polymer substrate; the lithium alloy is located on a side of the electronic insulating ion transport layer close to the lithium metal layer.

[0009] A reference electrode is formed by coating a lithium metal layer on the surface of a metal substrate and coating an electronic insulating ion transport layer on the surface of the lithium metal layer. Since an electronic insulating ion transport layer is provided on the outside of the reference electrode, a short circuit between the reference electrode and the negative electrode sheet and the positive electrode sheet can be avoided. Therefore, only one isolation film can be provided between the negative electrode sheet and the positive electrode sheet, which can better maintain the original structural design of the battery, thereby improving the accuracy of parameter testing.

[0010] By using an organic polymer matrix, a lithium alloy and a lithium salt in the electronic insulating ion transport layer of the reference electrode, the lithium alloy is located on the side of the electronic insulating ion transport layer close to the lithium metal layer; the lithium alloy in the organic polymer matrix can enhance the ion conductivity of the electronic insulating ion transport layer, so that lithium ions can better pass through the electronic insulating ion transport layer, which is beneficial to improving the accuracy of the parameter test results of the reference electrode; and the lithium alloy in the organic polymer matrix can also enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer, which is beneficial to prolonging the service life of the reference electrode and the three-electrode battery. The lithium alloy is located on the side of the electronic insulating ion transport layer close to the lithium metal layer, which is beneficial to improving the electronic insulation of the outer side of the electronic insulating ion transport layer.

[0011] In any embodiment, the lithium alloy includes one or more of lithium tin alloy, lithium copper alloy and lithium zinc alloy. In this way, the ion conductivity of the electronic insulating ion transport layer can be effectively improved, and the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer can be enhanced; thereby, the accuracy of parameter test results and the service life of the reference electrode and the three-electrode battery can be improved.

[0012] In any embodiment, the organic polymer matrix includes one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, styrene-butadiene rubber and polyimide. In this way, the electronic insulating ion transport layer can have good electronic insulation and ion conductivity.

[0013] In any embodiment, the lithium salt includes one or more of lithium fluoride, lithium carbonate, lithium bromide and lithium chloride. This is beneficial to improve the electronic insulation and ion conductivity of the electronic insulating ion transport layer; and can improve the stability of the SEI film after lithium plating of the reference electrode.

[0014] In any embodiment, the lithium salt is located on a side of the electronically insulating ion transport layer close to the lithium metal layer.

[0015] In any embodiment, the thickness of the lithium metal layer is 10 nm to 50 nm.

[0016] In any embodiment, the thickness of the electronically insulating ion transport layer is 3 μm to 6 μm.

[0017] In any embodiment, the metal matrix includes one or more of copper, gold and silver.

[0018] In any embodiment, the reference electrode is disposed between the negative electrode sheet and the separator, and the reference electrode is attached to the surface of the negative electrode sheet. In this way, compared with the method of disposing the reference electrode between the positive electrode sheet and the separator, the kinetic parameters of the negative electrode sheet can be tested more accurately.

[0019] In any embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector, and the reference electrode is disposed in the negative electrode film layer. Thus, disposing the reference electrode inside the negative electrode plate is conducive to accurately testing the kinetic parameters of the negative electrode plate.

[0020] The second aspect of the present application provides a reference electrode, comprising a metal substrate, a lithium metal layer and an electronically insulating ion transport layer, wherein the lithium metal layer is coated on the surface of the metal substrate, and the electronically insulating ion transport layer is coated on the surface of the lithium metal layer; the electronically insulating ion transport layer comprises an organic polymer substrate and a lithium alloy and a lithium salt in the organic polymer substrate; the lithium alloy is located on one side of the electronically insulating ion transport layer close to the lithium metal layer. In this way, the reference electrode is conducive to improving the accuracy of the kinetic parameter test of the negative electrode plate, and has a longer service life.

[0021] The third aspect of the present application provides a method for preparing a reference electrode, comprising the following steps:

[0022] Coating an electronically insulating ion transport precursor layer on the surface of a metal substrate, wherein the electronically insulating ion transport precursor layer comprises an organic polymer substrate and a non-lithium metal halide salt in the organic polymer substrate;

[0023] The metal substrate coated with the electronic insulating ion transport precursor layer is plated with lithium so that the non-lithium metal halide salt forms a lithium alloy and a lithium salt to obtain an electronic insulating ion transport layer, and a lithium metal layer is formed between the metal substrate and the electronic insulating ion transport layer.

[0024] In this way, the surface of the metal substrate is first coated with an electronic insulating ion transport precursor layer, and then lithium is plated, so that lithium ions pass through the electronic insulating ion transport precursor layer and are deposited on the surface of the metal substrate, so that the non-lithium metal halide salt forms a lithium alloy to obtain an electronic insulating ion transport layer, and a lithium metal layer is formed inside the electronic insulating ion transport layer; through this preparation method, the electronic insulating ion transport layer can protect the lithium metal layer, isolate the lithium metal layer from contact with oxygen, moisture and other substances in the external environment, prevent the lithium metal from being oxidized or undergoing other chemical reactions, thereby improving the stability and service life of the lithium metal layer. It is also conducive to controlling the deposition of the lithium metal layer.

[0025] Since the electronic insulating ion transport precursor layer contains non-lithium metal halide salts, during lithium plating, the non-lithium metal halide salts can react with lithium ions to generate lithium alloys and lithium salts. The lithium alloy generated in the electronic insulating ion transport layer can enhance the ion conductivity of the electronic insulating ion transport layer, which is beneficial to improving the accuracy of the parameter test results of the reference electrode; and the lithium alloy in the organic polymer matrix can also enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer, which is beneficial to extending the service life of the reference electrode. The lithium salt generated in the electronic insulating ion transport layer can improve the electronic insulation and ion conductivity of the electronic insulating ion transport layer; and can improve the stability of the SEI film after lithium plating of the reference electrode; it is filled in the pore structure of the electronic insulating ion transport layer, and can also improve the flexibility and strength of the electronic insulating ion transport layer.

[0026] In any embodiment, coating the surface of the metal substrate with an electronically insulating ion transport precursor layer comprises the following steps: applying a solution containing an organic polymer and a non-lithium metal halide salt to the surface of the metal substrate, and forming the electronically insulating ion transport precursor layer on the surface of the metal substrate after curing;

[0027] Alternatively, a solution containing an organic polymer monomer and a non-lithium metal halide salt is applied to the surface of the metal substrate, and the electronic insulating ion transport precursor layer is formed on the surface of the metal substrate after reaction and curing.

[0028] In any embodiment, lithium plating of the metal substrate coated with the electronic insulating ion transport precursor layer includes the following steps: forming a three-electrode battery with a positive electrode sheet, a negative electrode sheet, an isolation membrane and a metal substrate coated with the electronic insulating ion transport precursor layer of a lithium-ion battery, wherein the isolation membrane is located between the positive electrode sheet and the negative electrode sheet, and the metal substrate is located between the negative electrode sheet and the isolation membrane; connecting the positive electrode sheet to the positive electrode of a power source and the metal substrate to the negative electrode of the power source for charging; connecting the negative electrode sheet to the positive electrode of a power source and the metal substrate to the negative electrode of the power source for charging.

[0029] Through the above method, a lithium metal layer can be deposited on both the side of the metal substrate facing the positive electrode sheet and the side facing the negative electrode sheet; and a lithium alloy can be formed in the electronic insulating ion transport layer.

[0030] In any embodiment, before the surface of the metal substrate is coated with the electron-insulating ion transport precursor layer, the step of cleaning the metal substrate to remove oil stains and an oxide layer on the surface of the metal substrate is also included.

[0031] In any embodiment, after immersing and cleaning the metal substrate and before coating the surface of the metal substrate with an electronically insulating ion transport precursor layer, the step further includes etching the surface of the metal substrate to form lithium metal deposition sites on the surface of the metal substrate.

[0032] In this way, fine lithium metal deposition sites can be formed on the surface of the metal substrate, so that the lithium metal layer can be better attached to the surface of the metal substrate, thereby improving the deposition effect of the lithium metal layer and extending the service life of the reference electrode.

[0033] The fourth aspect of the present application provides an electrical device, comprising the three-electrode battery of the first aspect of the present application.

[0034] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to better describe and illustrate the embodiments or examples provided by the present application, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes of these applications currently understood. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0036] Figure 1 An exploded view of a three-electrode battery according to one embodiment of the present application;

[0037] Figure 2 An exploded view of a three-electrode battery according to another embodiment of the present application;

[0038] Figure 3 An exploded view of a three-electrode battery according to another embodiment of the present application;

[0039] Figure 4 is an enlarged schematic diagram of a reference electrode according to one embodiment of the present application;

[0040] Figure 5 This is a test curve diagram of the in-situ three-electrode test of the three-electrode battery of Example 1 of the present application.

[0041] Description of reference numerals:

[0042] 100. Three-electrode battery; 101. Positive electrode; 102. Negative electrode; 103. Isolation membrane; 104. Reference electrode; 1041. Metal substrate; 1042. Lithium metal layer; 1043. Electronic insulation ion transport layer. DETAILED DESCRIPTION

[0043] Hereinafter, the three-electrode battery, reference electrode, preparation method thereof, and implementation mode of the electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] The "range" disclosed in the present application can be limited in the form of a lower limit and an upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The range limited in this way can be including or excluding end values, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents the abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0045] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. The "implementation methods" mentioned herein have a similar understanding.

[0048] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0049] In the present application, in the open technical features or technical solutions described by the words "contain", "include", "comprise", etc., unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2 and a3" and the feature or solution of "A not only includes a1, a2 and a3, but also includes other members". In the present application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0050] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0051] During the design and development phase of lithium-ion batteries, it is necessary to rely on reference electrodes to test the kinetic parameters such as the lithium precipitation window of the negative electrode in order to develop a reasonable charge and discharge strategy. The conventional practice is to set two layers of separators between the positive and negative electrodes, and place a reference electrode (such as copper wire) between the two layers of separators to form a three-electrode battery for testing kinetic parameters such as the lithium precipitation window of the negative electrode. This structure of a three-electrode battery requires two layers of separators, while under normal circumstances there is only one layer of separator between the positive and negative electrodes of the battery. This three-electrode battery changes the original design of the battery, resulting in the accuracy of the test being affected. In addition, the reference electrode solution is corroded by the electrolyte, resulting in a short service life of the reference electrode and the three-electrode battery.

[0052] Based on this, see Figure 1 , Figure 2 , Figure 3 and Figure 4 In one embodiment of the present application, a three-electrode battery 100 is provided, which includes a positive electrode sheet 101, a negative electrode sheet 102, a separator 103 and a reference electrode 104; wherein the separator 103 is disposed between the positive electrode sheet 101 and the negative electrode sheet 102; the reference electrode 104 is disposed between the negative electrode sheet 102 and the separator 103, or the reference electrode 104 is disposed between the positive electrode sheet 101 and the separator 103, or the reference electrode 104 is disposed inside the negative electrode sheet 102. The reference electrode 104 includes a metal substrate 1041, a lithium metal layer 1042 and an electronic insulating ion transport layer 1043, wherein the lithium metal layer 1042 is coated on the surface of the metal substrate 1041, and the electronic insulating ion transport layer 1043 is coated on the surface of the lithium metal layer 1042; the electronic insulating ion transport layer 1043 includes an organic polymer matrix and a lithium alloy and a lithium salt in the organic polymer matrix; the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0053] The above-mentioned three-electrode battery 100 forms a reference electrode 104 by coating a lithium metal layer 1042 on the surface of a metal substrate 1041 and coating an electronic insulating ion transport layer 1043 on the surface of the lithium metal layer 1042; since the electronic insulating ion transport layer 1043 is provided on the outside of the reference electrode 104, the electronic insulating ion transport layer 1043 includes an organic polymer matrix and a lithium alloy and a lithium salt located in the organic polymer matrix, and the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042, the electronic insulating ion transport layer 1043 can avoid a short circuit between the reference electrode 104 and the negative electrode plate 102 and the positive electrode plate 101, so only one layer of isolation film 103 can be provided between the negative electrode plate 102 and the positive electrode plate 101, which can better maintain the original structural design of the battery, thereby improving the accuracy of parameter testing. The reference electrode 104 can be disposed between the negative electrode sheet 102 and the separator 103 , between the positive electrode sheet 101 and the separator 103 , or even inside the negative electrode sheet 102 .

[0054] By including an organic polymer matrix, a lithium alloy and a lithium salt in the electronic insulating ion transport layer 1043 of the reference electrode 104, the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042; the lithium alloy in the organic polymer matrix can enhance the ion conductivity of the electronic insulating ion transport layer 1043, so that lithium ions can better pass through the electronic insulating ion transport layer 1043, which is beneficial to improving the accuracy of the parameter test results of the reference electrode 104; and the lithium alloy in the organic polymer matrix can also enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer 1043, which is beneficial to prolonging the service life of the reference electrode 104 and the three-electrode battery 100. The lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042, while there is no lithium alloy on the side of the electronic insulating ion transport layer 1043 away from the lithium metal layer 1042, which is beneficial to improving the electronic insulation of the outer side of the electronic insulating ion transport layer 1043.

[0055] It should be noted that if Figure 1 As shown, the reference electrode 104 can be disposed between the negative electrode sheet 102 and the isolation film 103; Figure 2 As shown, the reference electrode 104 can also be arranged between the positive electrode sheet 101 and the isolation film 103; Figure 3 As shown, the reference electrode 104 may also be disposed inside the negative electrode sheet 102 .

[0056] In some embodiments, the lithium alloy includes one or more of lithium tin alloy (Li-Sn), lithium copper alloy (Li-Cu) and lithium zinc alloy (Li-Zn). The use of the above lithium alloy can effectively improve the ion conductivity of the electronic insulating ion transport layer 1043, enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer 1043, thereby facilitating the improvement of the accuracy of parameter test results and the service life of the reference electrode 104 and the three-electrode battery 100.

[0057] In some embodiments, the organic polymer matrix includes one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, styrene-butadiene rubber and polyimide. Using the above polymers as the material of the organic polymer matrix can make the electronic insulating ion transport layer 1043 have good electronic insulation and ion conductivity.

[0058] Among them, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride and styrene-butadiene rubber can be coated on the surface of the metal substrate 1041 in the form of solution or emulsion, and form an organic polymer matrix after drying and curing; polyimide can be cured by monomer curing, and the metal substrate 1041 is exposed to a solution containing polyimide monomer and initiator, and then reacted and cured to form an organic polymer matrix.

[0059] In some embodiments, the mass fraction of the organic polymer matrix is ​​90% to 99% based on the total mass of the electronic insulating ion transport layer 1043 being 100%. Controlling the mass fraction of the organic polymer matrix within the above range is conducive to making the electronic insulating ion transport layer 1043 have good electronic insulation and ion conductivity. It can be understood that the mass fraction of the organic polymer matrix in the electronic insulating ion transport layer 1043 can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% and any value within the range formed by any two of the above values.

[0060] In some embodiments, the lithium salt in the electronic insulating ion transport layer 1043 includes one or more of lithium fluoride, lithium carbonate, lithium bromide and lithium chloride. By adding the above lithium salt to the electronic insulating ion transport layer 1043, it is beneficial to improve the electronic insulation and ion conductivity of the electronic insulating ion transport layer 1043; and it can improve the stability of the SEI film after the reference electrode 104 is plated with lithium; in addition, the lithium salt is an inorganic particle that can be filled in the pore structure of the electronic insulating ion transport layer 1043 to improve the flexibility and strength of the electronic insulating ion transport layer 1043.

[0061] In some embodiments, the lithium salt is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042. In some embodiments, the thickness of the lithium metal layer 1042 is 10nm~50nm; the thickness of the electronic insulating ion transport layer 1043 is 3μm~6μm; the metal matrix 1041 includes one or more of copper, gold and silver, or other metal materials with good conductivity. Further, the metal matrix 1041 can be a copper wire. The diameter of the copper wire is generally less than or equal to 0.1mm.

[0062] It can be understood that the thickness of the lithium metal layer 1042 may be 10nm, 12nm, 15nm, 18nm, 20nm, 22nm, 25nm, 28nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, 48nm, 50nm and any value within the range formed by any two of the above values; the thickness of the electronic insulating ion transport layer 1043 may be 3μm, 3.2μm, 3.5μm, 3.8μm, 4μm, 4.2μm, 4.5μm, 4.8μm, 5μm, 5.2μm, 5.5μm, 5.8μm, 6μm and any value within the range formed by any two of the above values.

[0063] See also Figure 1 In some embodiments, the reference electrode 104 is disposed between the negative electrode sheet 102 and the separator 103, and the reference electrode 104 is attached to the surface of the negative electrode sheet 102. In this way, compared with the method of disposing the reference electrode 104 between the positive electrode sheet 101 and the separator 103, the kinetic parameters of the negative electrode sheet 102 can be tested more accurately.

[0064] See also Figure 3 In some embodiments, the negative electrode sheet 102 includes a negative electrode current collector (not shown) and a negative electrode film layer disposed on the negative electrode current collector, and the reference electrode 104 is disposed in the negative electrode film layer. Thus, disposing the reference electrode 104 inside the negative electrode sheet 102 is conducive to accurately testing the kinetic parameters of the negative electrode sheet 102.

[0065] See also Figure 4 Another embodiment of the present application provides a reference electrode 104, including a metal substrate 1041, a lithium metal layer 1042 and an electronic insulating ion transport layer 1043, the lithium metal layer 1042 is coated on the surface of the metal substrate 1041, and the electronic insulating ion transport layer 1043 is coated on the surface of the lithium metal layer 1042; the electronic insulating ion transport layer 1043 includes an organic polymer matrix and a lithium alloy and a lithium salt located in the organic polymer matrix; the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0066] A reference electrode 104 is formed by coating a lithium metal layer 1042 on the surface of a metal substrate 1041 and coating an electronic insulating ion transport layer 1043 on the surface of the lithium metal layer 1042; an electronic insulating ion transport layer 1043 is provided on the outer side of the reference electrode 104, and the electronic insulating ion transport layer 1043 includes an organic polymer matrix and a lithium alloy and a lithium salt in the organic polymer matrix, and the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042. The electronic insulating ion transport layer 1043 can avoid a short circuit between the reference electrode 104 and the negative electrode sheet 102 and the positive electrode sheet 101, so only one layer of isolation film 103 can be provided between the negative electrode sheet 102 and the positive electrode sheet 101, which can better maintain the original structural design of the battery, thereby improving the accuracy of parameter testing. The reference electrode 104 can be disposed between the negative electrode sheet 102 and the separator 103 , between the positive electrode sheet 101 and the separator 103 , or even inside the negative electrode sheet 102 .

[0067] By using an organic polymer matrix, a lithium alloy and a lithium salt in the electronic insulating ion transport layer 1043 of the reference electrode 104, the lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042; the lithium alloy in the organic polymer matrix can enhance the ion conductivity of the electronic insulating ion transport layer 1043, so that lithium ions can better pass through the electronic insulating ion transport layer 1043, which is beneficial to improve the accuracy of the parameter test results of the reference electrode 104; and the lithium alloy in the organic polymer matrix can also enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer 1043, which is beneficial to extend the service life of the reference electrode 104. The lithium alloy is located on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042, which is beneficial to improve the electronic insulation of the outer side of the electronic insulating ion transport layer 1043.

[0068] In some embodiments, the organic polymer matrix includes one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, styrene butadiene rubber and polyimide. In some specific examples, the mass fraction of the organic polymer matrix is ​​90% to 99% based on the total mass of the electronic insulating ion transport layer 1043 as 100%.

[0069] In some embodiments, the lithium salt includes one or more of lithium fluoride, lithium carbonate, lithium bromide and lithium chloride.

[0070] In some of the embodiments, the thickness of the lithium metal layer 1042 is 10 nm to 50 nm; the thickness of the electronic insulating ion transport layer 1043 is 3 μm to 6 μm; and the metal matrix 1041 includes one or more of copper, gold and silver.

[0071] In some embodiments, the reference electrode 104 includes a coated section and an uncoated section, wherein the lithium metal layer 1042 and the electronic insulating ion transport layer 1043 are disposed in the coated section, and the uncoated section is a bare metal substrate 1041. In the three-electrode battery 100, the coated section of the reference electrode 104 is located inside the battery, while the uncoated section extends to the outside of the battery for welding the conductive electrode lug.

[0072] Another embodiment of the present application provides a method for preparing the above-mentioned reference electrode 104, which comprises the following steps: coating the surface of a metal substrate 1041 with an electronic insulating ion transport precursor layer, wherein the electronic insulating ion transport precursor layer comprises an organic polymer matrix and a non-lithium metal halide salt in the organic polymer matrix; lithium plating the metal substrate 1041 coated with the electronic insulating ion transport precursor layer so that the non-lithium metal halide salt forms a lithium alloy and a lithium salt to obtain an electronic insulating ion transport layer 1043, and forming a lithium metal layer 1042 between the metal substrate 1041 and the electronic insulating ion transport layer 1043.

[0073] The above-mentioned preparation method first coats the surface of the metal substrate 1041 with an electronic insulating ion transport precursor layer, and then performs lithium plating, so that lithium ions pass through the electronic insulating ion transport precursor layer and are deposited on the surface of the metal substrate 1041, thereby forming a lithium metal layer 1042 on the inner side of the electronic insulating ion transport layer 1043; through this preparation method, the electronic insulating ion transport layer 1043 can protect the lithium metal layer 1042, and can isolate the lithium metal layer 1042 from contact with oxygen, moisture and other substances in the external environment, and prevent the lithium metal from being oxidized or undergoing other chemical reactions, thereby helping to improve the stability and service life of the lithium metal layer. It is also helpful to control the deposition of the lithium metal layer 1042.

[0074] Since the electronic insulating ion transport precursor layer contains non-lithium metal halide salts, during lithium plating, the non-lithium metal halide salts can react with lithium ions to generate lithium alloys and lithium salts on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042. The lithium alloy generated in the electronic insulating ion transport layer 1043 can enhance the ion conductivity of the electronic insulating ion transport layer 1043, so that lithium ions can better pass through the electronic insulating ion transport layer 1043, which is beneficial to improving the accuracy of the parameter test results of the reference electrode 104; and the lithium alloy in the organic polymer matrix can also enhance the flexibility, electrolyte corrosion resistance and strength of the electronic insulating ion transport layer 1043, which is beneficial to prolonging the service life of the reference electrode 104. The lithium salt generated in the electronic insulating ion transport layer 1043 can improve the electronic insulation and ion conductivity of the electronic insulating ion transport layer 1043; and can improve the stability of the SEI film after lithium plating of the reference electrode 104; the lithium salt is filled in the pore structure of the electronic insulating ion transport layer 1043, and can also improve the flexibility and strength of the electronic insulating ion transport layer 1043.

[0075] In some specific examples, the non-lithium metal halide salt may be a non-lithium metal fluoride salt, such as tin fluoride (SnF 2 ), copper fluoride (CuF 2 )、ZnF 2 ) etc.; accordingly, the generated lithium alloy is at least one of lithium-tin alloy (Li-Sn), lithium-copper alloy (Li-Cu) or lithium-zinc alloy (Li-Zn). Optionally, the non-lithium metal fluoride salt is tin fluoride. Taking tin fluoride as an example, the chemical equation for the reaction of lithium ions with tin fluoride to generate lithium-tin alloy and lithium fluoride is as follows: 3Li + +SnF 2 +3e - →Li-Sn-alloy+2LiF. It is understandable that since the above reaction requires the participation of electrons, the reaction will occur on the inner side of the electronic insulating ion transport precursor layer, so lithium alloy and lithium salt will be formed on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0076] In some of the embodiments, coating the surface of the metal substrate 1041 with an electronic insulating ion transport precursor layer includes the following steps: applying a solution containing an organic polymer and a non-lithium metal halide salt to the surface of the metal substrate 1041, and forming an electronic insulating ion transport precursor layer on the surface of the metal substrate 1041 after curing; or, applying a solution containing an organic polymer monomer and a non-lithium metal halide salt to the surface of the metal substrate 1041, and forming an electronic insulating ion transport precursor layer on the surface of the metal substrate 1041 after reaction and curing.

[0077] Among them, when the organic polymer matrix is ​​polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride or styrene-butadiene rubber, these polymers and non-lithium metal halide salts can be dissolved in a solvent to form a solution or emulsion, and then dried and solidified to form an electronic insulating ion transport precursor layer. When the organic polymer matrix is ​​polyimide, the polyimide monomer, cross-linking agent and non-lithium metal halide salt can be dissolved in a solvent, and then reacted and solidified to form an electronic insulating ion transport precursor layer on the surface of the metal matrix 1041.

[0078] Taking polyvinylidene fluoride-hexafluoropropylene copolymer as an organic polymer matrix material as an example, polar solvents such as N,N-dimethylformamide can be used as solvents, and the mass concentration of polyvinylidene fluoride-hexafluoropropylene copolymer is 2%~10%, and a 5% solution can be selected. Ultrasonic vibration is performed for more than 5 minutes to fully dissolve the polymer to form a solution. The mass concentration of the metal halide salt in the solution can be about 0.5%, and stirring is performed for more than 2 hours to fully disperse the non-lithium metal halide salt.

[0079] In some of the embodiments, a glass or steel plate mold can be used during curing, and a semi-cylindrical groove with a diameter of about 0.2mm~0.5mm (the diameter of the metal substrate 1041 is generally less than or equal to 0.1mm) is reserved on the surface of the mold. The metal substrate 1041 is placed in the groove, and the configured solution is injected. It is immediately placed in a vacuum drying oven, evacuated at 50℃~120℃, and heated for 2h~6h to dry.

[0080] In some of the embodiments, lithium plating of the metal substrate 1041 coated with the electronic insulating ion transport precursor layer includes the following steps: the positive electrode plate, the negative electrode plate, the isolation membrane and the metal substrate 1041 coated with the electronic insulating ion transport precursor layer of the lithium ion battery are combined into a three-electrode battery 100, wherein the isolation membrane is located between the positive electrode plate and the negative electrode plate, and the metal substrate 1041 is located between the negative electrode plate and the isolation membrane; the positive electrode plate is connected to the positive electrode of the power supply, and the metal substrate 1041 is connected to the negative electrode of the power supply for charging; the negative electrode plate is connected to the positive electrode of the power supply, and the metal substrate 1041 is connected to the negative electrode of the power supply for charging.

[0081] Through the above method, a lithium metal layer 1042 can be deposited on both the side of the metal substrate 1041 facing the positive electrode plate and the side facing the negative electrode plate; and a lithium alloy and a lithium salt can be formed on the side of the electronic insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0082] In some specific examples, the positive electrode plate is connected to the positive electrode of the power supply, the metal substrate 1041 is connected to the negative electrode of the power supply, and 50 μAh of electricity is charged at a constant current of 10μA~50μA; then the negative electrode plate is connected to the positive electrode of the power supply, the metal substrate 1041 is connected to the negative electrode of the power supply, and 50 μAh of electricity is charged at a constant current of 10μA~50μA.

[0083] In some of the embodiments, before the surface of the metal substrate 1041 is coated with the electron-insulating ion transport precursor layer, the step of cleaning the metal substrate 1041 to remove oil stains and an oxide layer on the surface of the metal substrate 1041 is also included.

[0084] Specifically, the metal substrate 1041 can be soaked in anhydrous ethanol for more than 5 minutes, and then a dilute acid solution (dilute hydrochloric acid or dilute sulfuric acid) with a concentration less than or equal to 0.05 mol / L is prepared, and the metal substrate 1041 is soaked in the dilute acid for 5 minutes to 10 minutes, and then washed with anhydrous ethanol and pure water in turn; thereby removing the oil stains and oxide layer on the surface of the metal substrate 1041.

[0085] In some of the embodiments, after the metal substrate 1041 is soaked and cleaned, and before the surface of the metal substrate 1041 is coated with the electronic insulating ion transport precursor layer, the surface of the metal substrate 1041 is further etched to form lithium metal deposition sites on the surface of the metal substrate 1041. In this way, fine lithium metal deposition sites can be formed on the surface of the metal substrate 1041, and the lithium metal layer 1042 can be deposited in the lithium metal deposition sites, so that the lithium metal layer 1042 can be more firmly attached to the surface of the metal substrate 1041, thereby improving the deposition effect of the lithium metal layer 1042 and extending the service life of the reference electrode 104.

[0086] In some specific examples, the surface of the metal substrate 1041 is etched by the following method: first, a dopamine hydrochloride solution is prepared: a dopamine (PDA) solution is prepared with purified water at a concentration of 1.5 mg / mL to 2.5 mg / mL, and a Tris-HCl buffer is used to adjust the pH of the PDA solution to between 8.5 and 9.0; the metal substrate 1041 is placed in the dopamine hydrochloride solution and soaked for 3 hours to 12 hours, thereby forming a lithium metal deposition site on the surface of the metal substrate 1041. The etching time should not be too short or too long; if the time is too short, the etching effect will be poor, affecting the deposition effect of the lithium metal layer 1042; if the time is too long, the etching will be more serious, affecting the toughness and strength of the metal substrate 1041.

[0087] Another embodiment of the present application provides an electrical device, including the three-electrode battery 100 described above in the present application.

[0088] The three-electrode battery and the electrical device of the present application are described below with appropriate reference to the drawings.

[0089] In one embodiment of the present application, a three-electrode battery is provided.

[0090] Typically, a three-electrode battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, a separator, and a reference electrode. During the battery charge and discharge process, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0091] The reference electrode adopts the reference electrode in the above embodiment of the present application.

[0092] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0093] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0094] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0095] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0096] As a non-limiting example, the positive electrode active material of the lithium-ion three-electrode battery may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO 2 Non-limiting examples of lithium nickel oxides may include LiNiO 2 Non-limiting examples of lithium manganese oxides may include LiMnO 2 、LiMn 2 O 4 etc.; Non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ) etc.; Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.1 Al 0.05 O 2 .

[0097] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that the new material obtained by appropriate modification on the basis of the listed positive electrode materials is also within the scope of the positive electrode material. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode material, and non-limiting examples include coating modification.

[0098] In the list of positive electrode materials in this application, the content of oxygen (O) is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be measured by molar content, but is not limited to this.

[0099] In some embodiments, the positive electrode active material layer may also optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode active material layer is 0 wt % to 20 wt %, based on the total weight of the positive electrode active material layer.

[0100] In some embodiments, the positive electrode active material layer may further include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode active material layer is 0 wt % to 20 wt %, based on the total weight of the positive electrode active material layer.

[0101] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, the positive electrode slurry is coated on both sides of the positive electrode collector, and the positive electrode sheet is formed after drying and cold pressing by a cold rolling mill.

[0102] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0103] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0104] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. Among them, in the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0105] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery known in the art.

[0106] As a non-limiting example, the negative electrode active material of the lithium-ion three-electrode battery may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0107] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0108] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0110] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the surface of the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode collector coated with the negative electrode slurry can be a single surface of the negative electrode collector or on both surfaces of the negative electrode collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s~10000mPa·s. When coating the negative electrode slurry, the double-sided coating unit surface density based on dry weight (excluding solvent) can be 75g / m 2 ~220g / m 2 The compaction density of the negative electrode sheet can be 1.0g / cm 3 ~1.8g / cm 3 .

[0111] The electrolyte has the function of conducting ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0112] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0113] In some embodiments, the electrolyte salt of the lithium-ion three-electrode battery may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) and lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0114] In some embodiments, the solvent may include one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0115] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0116] In some embodiments, the additive in the electrolyte may include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0117] In some embodiments, the three-electrode battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0118] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0119] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0120] In some embodiments, the three-electrode battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0121] In some embodiments, the outer packaging of the three-electrode battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the three-electrode battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0122] The three-electrode battery includes at least one battery cell. The three-electrode battery may include one or more battery cells.

[0123] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0124] In some embodiments, the outer package may include a shell and a cover plate. The shell may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly through a winding process or a lamination process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly. The number of electrode assemblies contained in the battery cell can be one or more, and those skilled in the art can select according to specific actual needs.

[0125] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0126] In the battery module, the plurality of battery cells may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells may be fixed by fasteners.

[0127] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0128] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0129] The battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0130] In addition, the present application also provides an electrical device, which includes at least one of the three-electrode battery, battery module, or battery pack provided in the present application. The three-electrode battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0131] As an electrical device, a three-electrode battery, a battery module or a battery pack can be selected according to its usage requirements.

[0132] The following are some examples.

[0133] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0134] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0135] Embodiment 1:

[0136] (1) Copper wire decontamination

[0137] A copper wire with a diameter of 0.1 mm was used as a metal substrate. The copper wire was immersed in anhydrous ethanol for 5 minutes, and then immersed in 0.05 mol / L dilute hydrochloric acid for 8 minutes; thereafter, it was washed with anhydrous ethanol and water in turn.

[0138] (2) Copper wire pretreatment

[0139] A dopamine (PDA) aqueous solution with a concentration of 2 mg / mL was prepared, and the pH of the PDA solution was adjusted to 9.0 using a Tris-HCl buffer to obtain a dopamine hydrochloride solution; the cleaned copper wire was placed in the dopamine hydrochloride solution and immersed for 6 hours to etch the copper wire.

[0140] (3) Copper wire insulation coating

[0141] Polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tin fluoride (SnF 2 ) was dissolved in N,N-dimethylformamide, and ultrasonically vibrated for 5 min to fully dissolve it, and the PVDF-HFP mass concentration was 5%, SnF 2 The polymer solution has a mass concentration of 0.5%.

[0142] The copper wire was coated with polymer using a glass mold. A semi-cylindrical groove was reserved on the surface of the glass mold. One end of the copper wire was placed in the groove, and the other end was extended from the groove. The prepared polymer solution was injected and immediately placed in a vacuum drying oven. The vacuum was dried at 100°C for 6 hours, thereby forming a film containing PVDF-HFP and SnF on the surface of some areas of the copper wire. 2 The coating is made of copper wire, and the other part is bare copper wire.

[0143] (4) Assembling three-electrode batteries and lithium plating

[0144] Lithium-ion battery positive electrode sheet, separator, PVDF-HFP and SnF 2 The copper wire of the coating layer and the negative electrode sheet are stacked in order, so that the isolation film is between the positive electrode sheet and the negative electrode sheet to play an isolating role, the copper wire is located between the isolation film and the negative electrode sheet and the part with the coating layer is attached to the surface of the negative electrode sheet, and a bare battery cell is obtained after stacking; the bare battery cell is placed in an outer packaging shell, and after drying, the electrolyte is injected and vacuum packaged.

[0145] The positive pole piece is connected to the positive pole of the power supply with the ear, and the exposed part of the copper wire is connected to the negative pole of the power supply. The copper wire is charged with a constant current of 30μA for 50μAh, thereby lithium plating on the layer of the copper wire facing the positive pole piece. The lithium ions pass through the PVDF-HFP coating layer and are deposited on the surface of the copper wire, forming a lithium metal layer between the copper wire and the PVDF-HFP coating layer. In addition, the lithium ions react with the SnF in the PVDF-HFP coating layer. 2 The reaction generates lithium-tin alloy (Li-Sn) and lithium fluoride (LiF) on the side of the coating layer close to the lithium metal layer.

[0146] The ear of the negative electrode is connected to the positive electrode of the power supply, and the exposed part of the copper wire is connected to the negative electrode of the power supply. The copper wire is charged with a constant current of 30μA for 50μAh, so that lithium is plated on the layer of the copper wire facing the negative electrode. The lithium ions pass through the PVDF-HFP coating layer and are deposited on the surface of the copper wire, forming a lithium metal layer between the copper wire and the PVDF-HFP coating layer. In addition, the lithium ions react with the SnF in the PVDF-HFP coating layer. 2 The reaction generates lithium-tin alloy and lithium fluoride on the side of the coating layer close to the lithium metal layer; thus, lithium is plated on both the front and back sides of the copper wire to form a lithium metal layer.

[0147] After the above lithium plating step, a lithium metal layer is formed between the copper wire and the PVDF-HFP coating layer, and the PVDF-HFP coating layer containing lithium tin alloy and lithium fluoride serves as an electronic insulating ion transport layer to obtain a reference electrode. The thickness of the lithium metal layer in the reference electrode is 50nm; the thickness of the electronic insulating ion transport layer is 6μm.

[0148] The three-electrode battery prepared in Example 1 was subjected to an in-situ three-electrode test. During the test, the positive electrode tab of the battery was connected to the positive electrode of the charging and discharging device, the negative electrode tab was connected to the negative electrode of the charging and discharging device, and the reference electrode tab was connected to the reference channel of the charging and discharging device. The voltage changes of each were monitored in real time during charging and discharging. The test results are shown in Figure 1. Figure 5 shown. Figure 5 The middle curve ① shows the change of the value of the positive electrode potential minus the reference electrode potential (positive electrode VS reference) with the charging time; curve ② shows the change of the value of the positive electrode potential minus the negative electrode potential (positive electrode VS negative electrode) with the charging time; curve ③ shows the change of the value of the negative electrode potential minus the reference electrode potential (negative electrode VS reference) with the charging time. Through the above-mentioned in-situ three-electrode test, the change trend of three curves is observed, and the charging time when curve ③ approaches 0 voltage is observed, the lithium plating of the negative electrode sheet can be judged, and then a basis for the formulation of battery charging and discharging strategies can be provided.

[0149] Embodiment 2:

[0150] This embodiment is basically the same as Embodiment 1, except that step (2) copper wire pretreatment step is not performed.

[0151] Embodiment 3:

[0152] (1) Copper wire decontamination

[0153] A copper wire with a diameter of 0.1 mm was used as a metal substrate. The copper wire was immersed in anhydrous ethanol for 5 minutes, and then immersed in 0.05 mol / L dilute hydrochloric acid for 8 minutes; thereafter, it was washed with anhydrous ethanol and water in turn.

[0154] (2) Copper wire pretreatment

[0155] A dopamine (PDA) aqueous solution with a concentration of 2 mg / mL was prepared, and the pH of the PDA solution was adjusted to 9.0 using a Tris-HCl buffer to obtain a dopamine hydrochloride solution; the cleaned copper wire was placed in the dopamine hydrochloride solution and immersed for 6 hours to etch the copper wire.

[0156] (3) Copper wire insulation coating

[0157] Styrene butadiene rubber and zinc fluoride (ZnF 2 ) was dissolved in N,N-dimethylformamide, and ultrasonically vibrated for 5 minutes to fully dissolve and disperse it, and the mass concentration of styrene-butadiene rubber was 5%, and ZnF 2 The polymer solution has a mass concentration of 0.5%.

[0158] The copper wire was coated with polymer using a glass mold. A semi-cylindrical groove was reserved on the surface of the glass mold. One section of the copper wire was placed in the groove, and the other section was extended from the groove. The prepared polymer solution was injected and immediately placed in a vacuum drying oven. The vacuum was dried at 100°C for 6 hours, thereby forming a film containing styrene-butadiene rubber and ZnF on the surface of some areas of the copper wire. 2 The coating is made of copper wire, and the other part is bare copper wire.

[0159] (4) Preparation of negative electrode

[0160] Graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose, and binder styrene butadiene rubber are mixed in a mass ratio of 96:1:1.2:1.8, and deionized water as a solvent is added, and the mixture is stirred evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on both sides of the negative electrode current collector copper foil, and the copper wire with the styrene butadiene rubber coating layer is buried in the negative electrode slurry on one side, and the negative electrode sheet is obtained by drying and cold pressing.

[0161] (5) Assembling three-electrode batteries and lithium plating

[0162] The positive electrode sheet, the separator and the negative electrode sheet of the lithium-ion battery are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the side of the negative electrode sheet with the copper wire buried faces the separator, and a bare battery cell is obtained after stacking; the bare battery cell is placed in an outer packaging shell, and after drying, the electrolyte is injected and vacuum packaged.

[0163] The positive pole piece is connected to the positive pole of the power source with the ear, and the exposed part of the copper wire is connected to the negative pole of the power source. The copper wire is charged with a constant current of 30μA for 50μAh, thereby lithium plating is performed on a layer of the copper wire facing the positive pole piece. The lithium ions pass through the styrene-butadiene rubber coating layer and are deposited on the surface of the copper wire, forming a lithium metal layer between the copper wire and the styrene-butadiene rubber coating layer. In addition, the lithium ions react with the ZnF in the styrene-butadiene rubber coating layer. 2The reaction generates lithium zinc alloy (Li-Zn) and lithium fluoride (LiF) on the side of the coating layer close to the lithium metal layer.

[0164] The ear of the negative electrode is connected to the positive electrode of the power supply, and the exposed part of the copper wire is connected to the negative electrode of the power supply. The copper wire is charged with a constant current of 30μA for 50μAh, so that lithium is plated on the layer of the copper wire facing the negative electrode. The lithium ions pass through the styrene-butadiene rubber coating layer and are deposited on the surface of the copper wire, forming a lithium metal layer between the copper wire and the styrene-butadiene rubber coating layer. In addition, the lithium ions react with the ZnF in the styrene-butadiene rubber coating layer. 2 The reaction generates lithium-zinc alloy and lithium fluoride on the side of the coating layer close to the lithium metal layer; thus, lithium is plated on both the front and back sides of the copper wire to form a lithium metal layer.

[0165] After the above lithium plating step, a lithium metal layer is formed between the copper wire and the styrene-butadiene rubber coating layer, and the styrene-butadiene rubber coating layer containing lithium-zinc alloy and lithium fluoride serves as an electronic insulating ion transport layer to obtain a reference electrode.

[0166] Embodiment 4:

[0167] This embodiment is basically the same as embodiment 1, except that copper fluoride (CuF 2 ) instead of tin fluoride (SnF 2 ); Accordingly, the lithium alloy in the electronic insulating ion transport layer is a lithium copper alloy.

[0168] Comparative Example 1:

[0169] This comparative example is basically the same as Example 1, except that SnF is not added to the polymer solution in step (3). 2 ; Accordingly, the electronic insulating ion transport layer does not contain lithium alloy; and polyvinylidene fluoride is used instead of polyvinylidene fluoride-hexafluoropropylene copolymer as the organic polymer matrix.

[0170] Comparative Example 2:

[0171] This comparative example is basically the same as Example 1, except that SnF is not added to the polymer solution in step (3). 2 ; Accordingly, the electronically insulating ion transport layer does not contain lithium alloy.

[0172] Reference electrode life evaluation method:

[0173] 1) Perform a cycle test on the three-electrode battery, using the positive electrode, negative electrode and reference channels to monitor the positive electrode tab, negative electrode tab and three-electrode tab of the three electrodes respectively.

[0174] 2) The test process is as follows:

[0175] ①Let it stand for 10 minutes;

[0176] ②1C rate constant current charging to the maximum voltage, constant voltage charging at the maximum voltage until the current is lower than 0.05C rate and then cut off;

[0177] ③Let stand for 10 minutes;

[0178] ④1C rate constant current discharge to the lower voltage limit;

[0179] ⑤ Cycle steps ① to ④ until the battery capacity decays to 80% of the initial capacity.

[0180] 3) Negative electrode potential monitoring

[0181] Step 2) During the test, the negative electrode potential is monitored in real time, and the lowest negative electrode potential during the constant voltage charging process in step ② is calculated, which is recorded as V n , n is the number of cycles.

[0182] 4) Test life evaluation

[0183] When V n -V n-1 When the absolute value of is greater than 0.1V, it is considered as a test abnormality. When the test abnormality occurs more than five times cumulatively or more than three times in a row, it is considered as the reference electrode life abnormality. The number of test cycles at this time is the life of the reference electrode.

[0184] The reference electrode life data of the three-electrode battery of each embodiment and comparative example are shown in Table 1. The reference electrode life in Table 1 is the data after rounding to the nearest ten.

[0185] Table 1

[0186]

[0187] As can be seen from Table 1, the reference electrode in the three-electrode battery of each embodiment of the present application has a longer service life. In Comparative Examples 1 and 2, SnF is not added to the polymer solution. 2 ; Correspondingly, the electronic insulating ion transport layer does not contain lithium alloy, and the life of its reference electrode is significantly reduced.

[0188] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0189] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A three-electrode battery, characterized in that: It includes a positive electrode sheet, a negative electrode sheet, a separator and a reference electrode; The separator is disposed between the positive electrode sheet and the negative electrode sheet; the reference electrode is disposed between the negative electrode sheet and the separator, or the reference electrode is disposed between the positive electrode sheet and the separator, or the reference electrode is disposed inside the negative electrode sheet; The reference electrode includes a metal substrate, a lithium metal layer and an electronic insulating ion transport layer, wherein the lithium metal layer is coated on the surface of the metal substrate, and the electronic insulating ion transport layer is coated on the surface of the lithium metal layer; the electronic insulating ion transport layer includes an organic polymer substrate and a lithium alloy and a lithium salt located in the organic polymer substrate; the lithium alloy is located on a side of the electronic insulating ion transport layer close to the lithium metal layer.

2. The three-electrode battery according to claim 1, characterized in that: The lithium alloy includes one or more of a lithium-tin alloy, a lithium-copper alloy and a lithium-zinc alloy.

3. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The organic polymer matrix includes one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, styrene-butadiene rubber and polyimide.

4. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The lithium salt includes one or more of lithium fluoride, lithium carbonate, lithium bromide and lithium chloride.

5. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The lithium salt is located on a side of the electronic insulating ion transport layer close to the lithium metal layer.

6. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The reference electrode satisfies at least one of the following: (1) The thickness of the lithium metal layer is 10 nm to 50 nm; (2) The thickness of the electronic insulating ion transport layer is 3 μm to 6 μm; (3) The metal matrix includes one or more of copper, gold and silver.

7. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The reference electrode is arranged between the negative electrode sheet and the isolation film, and the reference electrode is attached to the surface of the negative electrode sheet.

8. The three-electrode battery according to any one of claims 1 to 2, characterized in that: The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector, and the reference electrode is arranged in the negative electrode film layer.

9. A reference electrode, characterized in that It includes a metal substrate, a lithium metal layer and an electronic insulating ion transport layer, wherein the lithium metal layer is coated on the surface of the metal substrate, and the electronic insulating ion transport layer is coated on the surface of the lithium metal layer; the electronic insulating ion transport layer includes an organic polymer substrate and a lithium alloy and a lithium salt located in the organic polymer substrate; the lithium alloy is located on a side of the electronic insulating ion transport layer close to the lithium metal layer.

10. The reference electrode according to claim 9, characterized in that The reference electrode is the reference electrode used in the three-electrode battery according to any one of claims 2 to 8.

11. A method for preparing a reference electrode, characterized in that: The following steps are involved: Coating an electronically insulating ion transport precursor layer on the surface of a metal substrate, wherein the electronically insulating ion transport precursor layer comprises an organic polymer substrate and a non-lithium metal halide salt in the organic polymer substrate; The metal substrate coated with the electronic insulating ion transport precursor layer is plated with lithium so that the non-lithium metal halide salt forms a lithium alloy and a lithium salt to obtain an electronic insulating ion transport layer, and a lithium metal layer is formed between the metal substrate and the electronic insulating ion transport layer.

12. The method for preparing a reference electrode according to claim 11, characterized in that: Coating the surface of the metal substrate with an electronically insulating ion transport precursor layer comprises the following steps: Applying a solution containing an organic polymer and a non-lithium metal halide salt on the surface of the metal substrate, and forming the electronic insulating ion transport precursor layer on the surface of the metal substrate after curing; Alternatively, a solution containing an organic polymer monomer and a non-lithium metal halide salt is applied to the surface of the metal substrate, and the electronic insulating ion transport precursor layer is formed on the surface of the metal substrate after reaction and curing.

13. The method for preparing a reference electrode according to any one of claims 11 to 12, characterized in that: Plating lithium on the metal substrate coated with the electronic insulating ion transport precursor layer comprises the following steps: A three-electrode battery is formed by combining a positive electrode sheet, a negative electrode sheet, a separator and a metal substrate covering the electronic insulating ion transport precursor layer of a lithium-ion battery, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, and the metal substrate is located between the negative electrode sheet and the separator; Connect the positive electrode sheet to the positive electrode of a power source, and connect the metal substrate to the negative electrode of the power source for charging; The negative electrode plate is connected to the positive electrode of the power source, and the metal substrate is connected to the negative electrode of the power source for charging.

14. The method for preparing a reference electrode according to any one of claims 11 to 12, characterized in that: Before coating the surface of the metal substrate with the electron-insulating ion transport precursor layer, the method further includes etching the surface of the metal substrate to form lithium metal deposition sites on the surface of the metal substrate.

15. An electrical device, characterized in that: A three-electrode battery comprising the three-electrode battery according to any one of claims 1 to 8.

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