Three - electrode battery, reference electrode and its preparation method, and electrical device

Abstract

The present application provides a three - electrode battery, a reference electrode and its preparation method, and an electrical device. The three - electrode battery 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 matrix, a lithium metal layer, and an electron - insulating ion - transport layer. The lithium metal layer coats the surface of the metal matrix, and the electron - insulating ion - transport layer coats the surface of the lithium metal layer; the electron - insulating ion - transport layer 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 electron - insulating ion - transport layer close to the lithium metal layer. This three - electrode battery can accurately measure the kinetic parameters of the negative electrode sheet, and the reference electrode has a long service life.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, 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, with the increasingly wide application range of lithium-ion batteries, lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0003] During the design and R & D stage of lithium-ion batteries, it is necessary to rely on a reference electrode (i.e., the third electrode) to test kinetic parameters such as the lithium deposition window of the negative electrode in order to formulate a reasonable charge and discharge strategy. However, in traditional three-electrode batteries, the ion conductivity of the insulating layer outside the reference electrode is poor, the strength is low, the flexibility and corrosion resistance are poor; or, two separator films need to be provided in the three-electrode battery, and the reference electrode is arranged between the two separator films; the above three-electrode batteries will affect the accuracy of the kinetic parameter test of the reference electrode for the negative electrode sheet, and at the same time make the service life of the reference electrode and the three-electrode battery shorter.

[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 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, which can more accurately test the kinetic parameters of the negative electrode sheet, and the reference electrode has a long service life.

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

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

[0008] The reference electrode includes a metal matrix, a lithium metal layer and an electron-insulating ion transport layer, the lithium metal layer covers the surface of the metal matrix, and the electron-insulating ion transport layer covers the surface of the lithium metal layer; the electron-insulating ion transport layer 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 electron-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 electron-insulating ion-conducting layer on the surface of the lithium metal layer. Since the electron-insulating ion-conducting layer is provided outside the reference electrode, it can avoid the short-circuit situation between the reference electrode and the negative electrode plate and the positive electrode plate. Therefore, only one separator can be provided between the negative electrode plate and the positive electrode plate, which can better maintain the original structural design of the battery, thereby improving the accuracy of parameter testing.

[0010] In the electron-insulating ion-conducting layer of the reference electrode, an organic polymer matrix, a lithium alloy, and a lithium salt are used. The lithium alloy is located on the side of the electron-insulating ion-conducting layer close to the lithium metal layer. The lithium alloy in the organic polymer matrix can enhance the ion conductivity of the electron-insulating ion-conducting layer, enabling lithium ions to pass through the electron-insulating ion-conducting layer better, which is beneficial to improving the accuracy of the parameter test results of the reference electrode. Moreover, the lithium alloy in the organic polymer matrix can also enhance the flexibility, anti-electrolyte corrosion performance, and strength of the electron-insulating ion-conducting layer, which is beneficial to extending the service life of the reference electrode and the three-electrode battery. The lithium alloy is located on the side of the electron-insulating ion-conducting layer close to the lithium metal layer, which is beneficial to improving the electron insulation outside the electron-insulating ion-conducting 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 electron-insulating ion-conducting layer can be effectively improved, and the flexibility, anti-electrolyte corrosion performance, and strength of the electron-insulating ion-conducting layer can be enhanced; thus, it is beneficial to improving the accuracy of the parameter test results and the service life of the reference electrode and the three-electrode battery.

[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 electron-insulating ion-conducting layer can have good electron 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. In this way, it is beneficial to improving the electron insulation and ion conductivity of the electron-insulating ion-conducting layer; and it can improve the stability of the SEI film after the reference electrode is lithium-plated.

[0014] In any embodiment, the lithium salt is located on the side of the electron-insulating ion-conducting 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 electron-insulating ion-conducting layer is 3 μm to 6 μm.

[0017] In any embodiment, the metal matrix comprises 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 membrane, and the reference electrode is attached to the surface of the negative electrode sheet. Thus, compared with the method of disposing the reference electrode between the positive electrode sheet and the separator membrane, the kinetic parameters of the negative electrode sheet can be tested more accurately.

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

[0020] The second aspect of the present application provides a reference electrode, comprising a metal matrix, a lithium metal layer, and an electron-insulating ion-transporting layer. The lithium metal layer is coated on the surface of the metal matrix, and the electron-insulating ion-transporting layer is coated on the surface of the lithium metal layer; the electron-insulating ion-transporting layer comprises 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 electron-insulating ion-transporting layer close to the lithium metal layer. Thus, this reference electrode is beneficial to improving the accuracy of testing the kinetic parameters of the negative electrode sheet and has a long service life at the same time.

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

[0022] Coat an electron-insulating ion-transporting precursor layer on the surface of the metal matrix. The electron-insulating ion-transporting precursor layer comprises an organic polymer matrix and a non-lithium metal halide salt located in the organic polymer matrix;

[0023] Lithium plate the metal matrix coated with the electron-insulating ion-transporting precursor layer so that the non-lithium metal halide salt forms a lithium alloy and a lithium salt to obtain an electron-insulating ion-transporting layer, and a lithium metal layer is formed between the metal matrix and the electron-insulating ion-transporting layer.

[0024] Thus, first, an electron-insulating ion transport precursor layer is coated on the surface of the metal substrate, and then lithium plating is carried out, enabling lithium ions to pass through the electron-insulating ion transport precursor layer and deposit on the surface of the metal substrate, so that a non-lithium metal halide salt forms a lithium alloy to obtain an electron-insulating ion transport layer, and a lithium metal layer is formed on the inner side of the electron-insulating ion transport layer; through this preparation method, the electron-insulating ion transport layer can play a role in protecting the lithium metal layer, can isolate the contact between the lithium metal layer and substances such as oxygen and moisture in the external environment, prevent the lithium metal from being oxidized or undergoing other chemical reactions, thus being beneficial to improving the stability and service life of the lithium metal layer. And it is beneficial to control the deposition of the lithium metal layer.

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

[0026] In any implementation manner, coating the electron-insulating ion transport precursor layer on the surface of the metal substrate includes 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 electron-insulating ion transport precursor layer on the surface of the metal substrate after curing;

[0027] Or, applying a solution containing an organic polymer monomer and a non-lithium metal halide salt on the surface of the metal substrate, and forming the electron-insulating ion transport precursor layer on the surface of the metal substrate after reaction and curing.

[0028] In any implementation manner, lithium plating the metal substrate coated with the electron-insulating ion transport precursor layer includes the following steps: forming a three-electrode battery with the positive electrode plate, negative electrode plate, separator and the metal substrate coated with the electron-insulating ion transport precursor layer of the lithium ion battery, where the separator is located between the positive electrode plate and the negative electrode plate, and the metal substrate is located between the negative electrode plate and the separator; connecting the positive electrode plate to the positive pole of the power supply and the metal substrate to the negative pole of the power supply for charging; connecting the negative electrode plate to the positive pole of the power supply and the metal substrate to the negative pole of the power supply for charging.

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

[0030] In any embodiment, before coating the electron-insulating ion transport precursor layer on the surface of the metal matrix, it further includes a step of cleaning the metal matrix to remove oil stains and oxide layers on the surface of the metal matrix.

[0031] In any embodiment, after soaking and cleaning the metal matrix and before coating the electron-insulating ion transport precursor layer on the surface of the metal matrix, it further includes a step of etching the surface of the metal matrix to form lithium metal deposition sites on the surface of the metal matrix.

[0032] In this way, fine lithium metal deposition sites can be formed on the surface of the metal matrix, enabling the lithium metal layer to better adhere to the surface of the metal matrix, 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, including the three-electrode battery of the first aspect of the present application.

[0034] 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 specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To better describe and illustrate the embodiments or examples provided by the present application, one or more drawings can be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed application, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

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

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

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

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

[0040] Figure 5 It is a test curve graph for in-situ three-electrode testing of the three-electrode battery of Embodiment 1 of the present application.

[0041] Explanation of reference numerals:

[0042] 100. Three-electrode battery; 101. Positive electrode sheet; 102. Negative electrode sheet; 103. Separator; 104. Reference electrode; 1041. Metal substrate; 1042. Lithium metal layer; 1043. Electron-insulating ion transport layer. Detailed implementation manners

[0043] Hereinafter, embodiments of the three-electrode battery, reference electrode and its preparation method, and electrical device of the present application are described in detail with appropriate reference to the accompanying 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 identical 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 accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0044] The "range" disclosed in the present application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include or not include the end values, and any end value can be independently included or not included, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. 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 are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, the numerical range "a~b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been fully listed herein, and "0~5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to listing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a certain parameter is 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 this application, terms such as "multiple" and "diverse", unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0046] Without specific instructions, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0047] Reference to "embodiment" in this document means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The phrase may not necessarily refer to the same embodiment at every location in the specification, nor are they independent or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to "implementation manner" mentioned in this document.

[0048] Those skilled in the art can understand that in the methods of each embodiment or implementation manner, the written order of each step does not imply a strict execution order that would impose any limitation on the implementation process. The detailed execution order of each step should be determined based on its function and possible internal logic. Without specific instructions, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0049] In this application, in an open technical feature or technical solution described using terms such as "containing", "including", "comprising", etc., unless otherwise stated, additional members outside the listed members are not excluded. It can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, A includes a1, a2, and a3. Unless otherwise stated, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution that "A is composed of a1, a2, and a3" and the feature or solution that "A not only includes a1, a2, and a3 but also includes other members". In this application, unless otherwise stated, 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 "option" mean "may or may not be", that is, any one of the two parallel options of "yes" or "no" is selected. If "optional" appears in multiple places in a technical solution, without special instructions, and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0051] During the design and R & D stage of lithium-ion batteries, it is necessary to rely on a reference electrode to test kinetic parameters such as the lithium deposition window of the negative electrode in order to formulate a reasonable charge-discharge strategy. The conventional method is to set two separator films between the positive electrode and the negative electrode, and place a reference electrode (such as a copper wire) between the two separator films to form a three-electrode battery for testing kinetic parameters such as the lithium deposition window of the negative electrode. In this three-electrode battery with such a structure, two separator films need to be set, while normally there is only one separator film 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, please refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 In one embodiment of the present application, a three-electrode battery 100 is provided. The three-electrode battery 100 includes a positive electrode tab 101, a negative electrode tab 102, a separator 103, and a reference electrode 104. Among them, the separator 103 is disposed between the positive electrode tab 101 and the negative electrode tab 102. The reference electrode 104 is disposed between the negative electrode tab 102 and the separator 103, or the reference electrode 104 is disposed between the positive electrode tab 101 and the separator 103, or the reference electrode 104 is disposed inside the negative electrode tab 102. The reference electrode 104 includes a metal matrix 1041, a lithium metal layer 1042, and an electronically insulating ion transport layer 1043. The lithium metal layer 1042 coats the surface of the metal matrix 1041, and the electronically insulating ion transport layer 1043 coats the surface of the lithium metal layer 1042. The electronically 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 electronically insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0053] The above 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 electron - insulating ion - transport layer 1043 on the surface of the lithium - metal layer 1042. Since an electron - insulating ion - transport layer 1043 is provided outside the reference electrode 104, and the electron - insulating ion - transport layer 1043 includes an organic - polymer matrix and a lithium alloy and a lithium salt located in the organic - polymer matrix, with the lithium alloy located on the side of the electron - insulating ion - transport layer 1043 close to the lithium - metal layer 1042, the electron - insulating ion - transport layer 1043 can prevent a short - circuit situation between the reference electrode 104, the negative - electrode plate 102, and the positive - electrode plate 101. Therefore, only one separator 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 plate 102 and the separator 103, or can be disposed between the positive - electrode plate 101 and the separator 103, or even can be disposed inside the negative - electrode plate 102.

[0054] By including an organic - polymer matrix, a lithium alloy, and a lithium salt in the electron - insulating ion - transport layer 1043 of the reference electrode 104, with the lithium alloy located on the side of the electron - 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 electron - insulating ion - transport layer 1043, enabling lithium ions to better pass through the electron - insulating ion - transport layer 1043, which is beneficial to improving the accuracy of the parameter - testing results of the reference electrode 104. Moreover, the lithium alloy in the organic - polymer matrix can also enhance the flexibility, anti - electrolyte - corrosion performance, and strength of the electron - insulating ion - transport layer 1043, which is beneficial to extending the service life of the reference electrode 104 and the three - electrode battery 100. The lithium alloy is located on the side of the electron - insulating ion - transport layer 1043 close to the lithium - metal layer 1042, while there is no lithium alloy on the side of the electron - insulating ion - transport layer 1043 far from the lithium - metal layer 1042, which is beneficial to improving the electron insulation outside the electron - insulating ion - transport layer 1043.

[0055] It should be noted that, as Figure 1 shown, the reference electrode 104 can be disposed between the negative - electrode plate 102 and the separator 103; as Figure 2 shown, the reference electrode 104 can also be disposed between the positive - electrode plate 101 and the separator 103; as Figure 3 shown, the reference electrode 104 can also be disposed inside the negative - electrode plate 102.

[0056] In some of these embodiments, the lithium alloy includes one or more of a lithium-tin alloy (Li-Sn), a lithium-copper alloy (Li-Cu), and a lithium-zinc alloy (Li-Zn). By using the above lithium alloy, the ionic conductivity of the electron-insulating ion transport layer 1043 can be effectively improved, and the flexibility, electrolyte corrosion resistance, and strength of the electron-insulating ion transport layer 1043 can be enhanced; thus, it is beneficial to improve the accuracy of parameter test results and the service life of the reference electrode 104 and the three-electrode cell 100.

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

[0058] Among them, the polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and styrene-butadiene rubber can be coated on the surface of the metal matrix 1041 in the form of a solution or an emulsion, and an organic polymer matrix is formed after drying and curing; polyimide can be formed by monomer curing. The metal matrix 1041 is placed in a solution containing polyimide monomers and initiators, and then an organic polymer matrix is formed after reaction curing.

[0059] In some of these embodiments, based on the total mass of the electron-insulating ion transport layer 1043 being 100%, the mass fraction of the organic polymer matrix is 90% - 99%. Controlling the mass fraction of the organic polymer matrix within the above range is beneficial to make the electron-insulating ion transport layer 1043 have good electron insulation and ionic conductivity. It can be understood that the mass fraction of the organic polymer matrix in the electron-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 of these embodiments, the lithium salts in the electron-insulating ion transport layer 1043 include one or more of lithium fluoride, lithium carbonate, lithium bromide, and lithium chloride. By adding the above lithium salts to the electron-insulating ion transport layer 1043, it is beneficial to improve the electron insulation and ionic conductivity of the electron-insulating ion transport layer 1043; and it can improve the stability of the SEI film after lithium plating of the reference electrode 104; in addition, the lithium salt is an inorganic particle that can fill the pore structure of the electron-insulating ion transport layer 1043, improving the flexibility and strength of the electron-insulating ion transport layer 1043.

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

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

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

[0064] Please refer to Figure 3 , in some of these embodiments, the negative electrode plate 102 includes a negative current collector (not shown in the figure) and a negative electrode film layer disposed on the negative current collector, and the reference electrode 104 is disposed in the negative electrode film layer. In this way, disposing the reference electrode 104 inside the negative electrode plate 102 is beneficial to accurately measuring the kinetic parameters of the negative electrode plate 102.

[0065] Please refer to Figure 4 , another embodiment of the present application provides a reference electrode 104, including a metal matrix 1041, a lithium metal layer 1042, and an electron-insulating ion transport layer 1043. The lithium metal layer 1042 is coated on the surface of the metal matrix 1041, and the electron-insulating ion transport layer 1043 is coated on the surface of the lithium metal layer 1042; the electron-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 electron-insulating ion transport layer 1043 close to the lithium metal layer 1042.

[0066] By coating a lithium metal layer 1042 on the surface of a metal matrix 1041 and coating an electron-insulating ion transport layer 1043 on the surface of the lithium metal layer 1042, a reference electrode 104 is formed; an electron-insulating ion transport layer 1043 is provided outside the reference electrode 104, and the electron-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 electron-insulating ion transport layer 1043 close to the lithium metal layer 1042. The electron-insulating ion transport layer 1043 can prevent short circuits between the reference electrode 104 and the negative electrode tab 102 and the positive electrode tab 101. Therefore, only one separator 103 can be provided between the negative electrode tab 102 and the positive electrode tab 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 provided between the negative electrode tab 102 and the separator 103, or can be provided between the positive electrode tab 101 and the separator 103, or even can be provided inside the negative electrode tab 102.

[0067] By using an organic polymer matrix, a lithium alloy and a lithium salt in the electron-insulating ion transport layer 1043 of the reference electrode 104, the lithium alloy is located on the side of the electron-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 electron-insulating ion transport layer 1043, enabling lithium ions to better pass through the electron-insulating ion transport layer 1043, which is beneficial to improving the accuracy of the parameter test results of the reference electrode 104; moreover, the lithium alloy in the organic polymer matrix can also enhance the flexibility, anti-electrolyte corrosion performance and strength of the electron-insulating ion transport layer 1043, which is beneficial to extending the service life of the reference electrode 104. The lithium alloy is located on the side of the electron-insulating ion transport layer 1043 close to the lithium metal layer 1042, which is beneficial to improving the electron insulation outside the electron-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, based on the total mass of the electron-insulating ion transport layer 1043 being 100%, the mass fraction of the organic polymer matrix is 90% - 99%.

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

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

[0071] In some of these embodiments, the reference electrode 104 includes a coated section and an uncoated section. The lithium metal layer 1042 and the electronically insulating ion transport layer 1043 are disposed within the coated section, and the uncoated section is the exposed metal substrate 1041. In the three - electrode cell 100, the coated section of the reference electrode 104 is located inside the cell; while the uncoated section extends outside the cell for welding the conductive electrode tab.

[0072] Another embodiment of the present application provides a method for preparing the above - mentioned reference electrode 104. The preparation method includes the following steps: coating an electronically insulating ion transport precursor layer on the surface of the metal substrate 1041, where the electronically insulating ion transport precursor layer includes an organic polymer matrix and a non - lithium metal halide salt located in the organic polymer matrix; plating lithium on the metal substrate 1041 coated with the electronically insulating ion transport precursor layer to form a lithium alloy and a lithium salt from the non - lithium metal halide salt to obtain the electronically insulating ion transport layer 1043, and forming a lithium metal layer 1042 between the metal substrate 1041 and the electronically insulating ion transport layer 1043.

[0073] In the above - mentioned preparation method, first, an electronically insulating ion transport precursor layer is coated on the surface of the metal substrate 1041, and then lithium plating is carried out, so that lithium ions pass through the electronically insulating ion transport precursor layer and deposit on the surface of the metal substrate 1041, thereby forming a lithium metal layer 1042 on the inner side of the electronically insulating ion transport layer 1043. Through this preparation method, the electronically insulating ion transport layer 1043 can play a role in protecting the lithium metal layer 1042, can isolate the contact between the lithium metal layer 1042 and substances such as oxygen and moisture in the external environment, prevent the lithium metal from being oxidized or undergoing other chemical reactions, and thus is beneficial to improving the stability and service life of the lithium metal layer. And it is beneficial to control the deposition of the lithium metal layer 1042.

[0074] Since the electron-insulating ion transport precursor layer contains non-lithium metal halide salts, when lithium plating is carried out, the non-lithium metal halide salts can react with lithium ions to form a lithium alloy and lithium salts on the side of the electron-insulating ion transport layer 1043 close to the lithium metal layer 1042. The lithium alloy formed in the electron-insulating ion transport layer 1043 can enhance the ion conductivity of the electron-insulating ion transport layer 1043, enabling lithium ions to pass through the electron-insulating ion transport layer 1043 better, which is beneficial to improving the accuracy of the parameter test results of the reference electrode 104; moreover, the lithium alloy in the organic polymer matrix can also enhance the flexibility, anti-electrolyte corrosion performance and strength of the electron-insulating ion transport layer 1043, which is beneficial to extending the service life of the reference electrode 104. The lithium salts formed in the electron-insulating ion transport layer 1043 can improve the electron insulation and ion conductivity of the electron-insulating ion transport layer 1043; and can improve the stability of the SEI film after lithium plating of the reference electrode 104; the lithium salts are filled in the pore structure of the electron-insulating ion transport layer 1043, and can also improve the flexibility and strength of the electron-insulating ion transport layer 1043.

[0075] In some specific examples, the non-lithium metal halide salt can be a non-lithium metal fluoride salt, such as at least one of tin fluoride (SnF2), copper fluoride (CuF2), zinc fluoride (ZnF2), etc.; correspondingly, the formed 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 form a lithium-tin alloy and lithium fluoride is as follows: 3Li + + SnF2 + 3e - → Li-Sn-alloy + 2LiF. It can be understood that since the above reaction requires the participation of electrons, the reaction will occur on the inner side of the electron-insulating ion transport precursor layer, so a lithium alloy and lithium salts will be formed on the side of the electron-insulating ion transport layer 1043 close to the lithium metal layer 1042.

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

[0077] Among them, when the organic polymer matrix is polyvinylidene fluoride - hexafluoropropylene copolymer, polyvinylidene fluoride or styrene - butadiene rubber, a solution or emulsion can be formed by dissolving these polymers and non - lithium metal halide salts in a solvent, and an electron - insulating ion - transport precursor layer can be formed after drying and curing. When the organic polymer matrix is polyimide, a polyimide monomer, a cross - linker and a non - lithium metal halide salt can be dissolved in a solvent, and an electron - insulating ion - transport precursor layer can be formed on the surface of the metal matrix 1041 after reaction and curing.

[0078] Taking polyvinylidene fluoride - hexafluoropropylene copolymer as an example of the organic polymer matrix material, a polar solvent such as N,N - dimethylformamide can be used as the solvent. A solution with a mass concentration of polyvinylidene fluoride - hexafluoropropylene copolymer of 2% - 10%, preferably 5%, can be prepared, and ultrasonic vibration can be carried out for more than 5 min 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 can be carried out for more than 2 h to fully disperse the non - lithium metal halide salt.

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

[0080] In some embodiments, the lithium plating of the metal matrix 1041 coated with the electron - insulating ion - transport precursor layer includes the following steps: The positive electrode plate, negative electrode plate, separator and the metal matrix 1041 coated with the electron - insulating ion - transport precursor layer of a lithium - ion battery form a three - electrode battery 100, where the separator is located between the positive electrode plate and the negative electrode plate, and the metal matrix 1041 is located between the negative electrode plate and the separator; the positive electrode plate is connected to the positive pole of the power supply, the metal matrix 1041 is connected to the negative pole of the power supply, and charging is carried out; the negative electrode plate is connected to the positive pole of the power supply, and the metal matrix 1041 is connected to the negative pole of the power supply, and charging is carried out.

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

[0082] In some specific examples, after connecting the positive electrode plate to the positive pole of the power supply and the metal matrix 1041 to the negative pole of the power supply, a constant current charge of 50 μAh is carried out at a constant current of 10 μA to 50 μA; then, the negative electrode plate is connected to the positive pole of the power supply and the metal matrix 1041 is connected to the negative pole of the power supply, and a constant current charge of 50 μAh is carried out at a constant current of 10 μA to 50 μA.

[0083] In some of these embodiments, before coating the surface of the metal matrix 1041 with an electron-insulating ion transport precursor layer, it further includes a step of cleaning the metal matrix 1041 to remove oil stains and oxide layers on the surface of the metal matrix 1041.

[0084] Specifically, the metal matrix 1041 can be soaked in absolute 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 matrix 1041 is soaked in the dilute acid for 5 minutes to 10 minutes, and then sequentially cleaned with absolute ethanol and pure water; thereby removing oil stains and oxide layers on the surface of the metal matrix 1041.

[0085] In some of these embodiments, after soaking and cleaning the metal matrix 1041 and before coating the surface of the metal matrix 1041 with an electron-insulating ion transport precursor layer, it further includes a step of etching the surface of the metal matrix 1041 to form lithium metal deposition sites on the surface of the metal matrix 1041. In this way, fine lithium metal deposition sites can be formed on the surface of the metal matrix 1041, and the lithium metal layer 1042 can be deposited within the lithium metal deposition sites, enabling the lithium metal layer 1042 to adhere more firmly to the surface of the metal matrix 1041, 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 matrix 1041 is etched by the following method: First, prepare a hydrochloric acid dopamine solution: Prepare a dopamine (PDA) solution with pure water at a concentration of 1.5 mg / mL to 2.5 mg / mL, and adjust the pH of the PDA solution to between 8.5 and 9.0 using a Tris-HCl buffer; place the metal matrix 1041 in the hydrochloric acid dopamine solution and soak it for 3 hours to 12 hours, thereby forming lithium metal deposition sites on the surface of the metal matrix 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 severe, affecting the toughness and strength of the metal matrix 1041.

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

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

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

[0090] Generally, a three-electrode battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, a separator, and a reference electrode. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly serving to prevent short circuit between the positive and negative electrodes, and at the same time 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 provided 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 own thickness direction, and the positive electrode active material layer is provided on either 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, as the metal foil, aluminum foil can be used. 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 can 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, etc. 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), and polyethylene (PE).

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

[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 conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the 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 the 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 manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), etc.; non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.1 Al 0.05 O2.

[0097] Understandably, during the charge and discharge process of the battery, the insertion and extraction of lithium (Li) and its consumption will occur, and the content of Li in the positive electrode sheet varies when the battery is discharged to different states. In the enumeration of the positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode material is applied to the positive electrode sheet in the battery system, after charge and discharge cycles, the content of Li in the positive electrode material contained in the sheet usually changes. Among them, the content of Li can be measured by molar content, but is not limited thereto. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0098] In the enumeration of the positive electrode materials in this application, the content of oxygen (O) is only the 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 show fluctuations. Among them, the content of O can be measured by molar content, but is not limited thereto.

[0099] In some embodiments, the positive electrode active material layer may further 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 fluorinated 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 optionally 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 by the following method: dispersing the components for preparing the positive electrode sheet described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on both surfaces of the positive electrode current collector, and forming the positive electrode sheet 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 provided on at least one surface of the negative electrode current collector, and 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 either or both of the two opposite surfaces of the negative electrode current collector.

[0104] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Among them, in the negative electrode current collector, non-limiting examples of the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate can 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 can be a negative electrode active material for a battery well-known in the art.

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

[0107] In some embodiments, the negative electrode active material layer may optionally further include a binder. The binder can 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 optionally further include a conductive agent. The conductive agent can 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 optionally further include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[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 surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current 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 calculated by dry weight (deducting the solvent) can be 75g / m 2 ~220g / m 2 . The tap density of the negative electrode sheet can be 1.0g / cm 3 ~1.8g / cm 3 .

[0111] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0112] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0113] In some embodiments, the electrolyte salt of the lithium-ion three-electrode battery can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0114] In some embodiments, the solvent may include one or more of vinyl fluorocarbonate (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 also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, etc.

[0116] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of vinyl fluorocarbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl vinyl carbonate (TFPC), etc.

[0117] In some embodiments, a separator is further included in the three-electrode battery. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0118] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator 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 can be made into an electrode assembly by a winding process or a stacking process.

[0120] In some embodiments, the three-electrode battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0121] In some embodiments, the outer packaging of the three - electrode battery can 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 can also be a soft package, such as a pouch - type soft package. The material of the soft package can be plastic. Further, non - limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

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

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

[0124] In some embodiments, the outer packaging can include a housing and a cover plate. Among them, the housing can include a bottom plate and side plates connected to the bottom plate. The bottom plate and the side plates enclose to form a receiving cavity. The housing has an opening communicating with the receiving cavity, and the cover plate can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly by a winding process or a stacking process. The electrode assembly is encapsulated in the receiving cavity. The electrolyte infiltrates the electrode assembly. The number of electrode assemblies included 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, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

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

[0127] Optionally, the battery module can further include a housing having a receiving space, and multiple battery cells are received in the receiving space.

[0128] In some embodiments, the above - mentioned battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0129] A 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. 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 by the present application. The three-electrode battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device 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, satellites, energy storage systems, etc., but is not limited thereto.

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

[0132] The following are some embodiments.

[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 embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0134] For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial procurement.

[0135] Embodiment 1:

[0136] (1) Copper wire decontamination

[0137] A copper wire with a diameter of 0.1 mm is used as the metal substrate. The copper wire is soaked in absolute ethanol for 5 min, and then soaked in 0.05 mol / L dilute hydrochloric acid for 8 min; then it is washed successively with absolute ethanol and water.

[0138] (2) Copper wire pretreatment

[0139] Prepare an aqueous dopamine (PDA) solution with a concentration of 2 mg / mL, and adjust the pH of the PDA solution to 9.0 using Tris-HCl buffer to obtain a dopamine hydrochloride solution; place the cleaned copper wire in the dopamine hydrochloride solution and soak it for 6 h to etch the copper wire.

[0140] (3)Insulating coating of copper wire

[0141] Dissolve polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tin fluoride (SnF2) in the solvent N,N-dimethylformamide, and ultrasonically oscillate for 5 min to fully dissolve them, and prepare a polymer solution with a mass concentration of PVDF-HFP of 5% and a mass concentration of SnF2 of 0.5%.

[0142] Use a glass mold to coat the copper wire with the polymer. A semi-cylindrical groove is reserved on the surface of the glass mold. Place one end of the copper wire into the groove, and the other end extends out of the groove. Inject the prepared polymer solution, and immediately place it in a vacuum drying oven. Vacuum dry at 100 °C for 6 h, so as to form a coating layer containing PVDF-HFP and SnF2 on the surface of a partial area of the copper wire, and the other part is the bare copper wire.

[0143] (4)Assembly of three-electrode battery and lithium plating

[0144] Stack the positive electrode sheet, separator, copper wire with PVDF-HFP and SnF2 coating layer, and negative electrode sheet in sequence, so that the separator is between the positive electrode sheet and the negative electrode sheet to play a role in isolation. The copper wire is between the separator and the negative electrode sheet, and the part with the coating layer is attached to the surface of the negative electrode sheet. After stacking, a bare battery core is obtained; place the bare battery core in an outer packaging shell, inject electrolyte after drying, and vacuum package.

[0145] Connect the ear of the positive electrode sheet to the positive electrode of the power supply, and the exposed part of the copper wire to the negative electrode of the power supply. Charge with a constant current of 30 μA for a charge of 50 μAh, so as to deposit lithium on the layer of the copper wire facing the positive electrode sheet. Lithium ions pass through the PVDF-HFP coating layer and deposit on the surface of the copper wire, forming a lithium metal layer between the copper wire and the PVDF-HFP coating layer; moreover, lithium ions react with SnF2 in the PVDF-HFP coating layer to generate lithium tin alloy (Li-Sn) and lithium fluoride (LiF) on the side of the coating layer close to the lithium metal layer.

[0146] Connect the tab of the negative electrode plate to the positive electrode of the power supply, and connect the exposed part of the copper wire to the negative electrode of the power supply. Charge with a constant current of 30 μA for a charge of 50 μAh, so as to deposit lithium on the layer of the copper wire facing the negative electrode plate. Lithium ions pass through the PVDF-HFP coating layer and deposit on the surface of the copper wire, forming a lithium metal layer between the copper wire and the PVDF-HFP coating layer; moreover, lithium ions react with SnF2 in the PVDF-HFP coating layer to generate lithium tin alloy and lithium fluoride on the side of the coating layer close to the lithium metal layer; thus, lithium metal layers are deposited on both the front and back sides of the copper wire.

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

[0148] Perform in-situ three-electrode testing on the three-electrode battery prepared in Example 1. During the test, connect the positive tab of the battery to the positive electrode of the charge-discharge device, the negative tab to the negative electrode of the charge-discharge device, and the reference electrode tab to the reference channel of the charge-discharge device, and monitor the voltage changes of each electrode in real time during charge and discharge. The test results are as Figure 5 shown. Figure 5 In the figure, curve ① represents the change of the value of the positive electrode potential minus the reference electrode potential (positive electrode VS reference electrode) with the charging time; curve ② represents 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 represents the change of the value of the negative electrode potential minus the reference electrode potential (negative electrode VS reference electrode) with the charging time. Through the above in-situ three-electrode testing, observe the change trends of the three curves, and observe the charging time when curve ③ approaches 0 voltage, then the lithium deposition situation of the negative electrode plate can be judged, and further provide a basis for formulating the charge-discharge strategy of the battery.

[0149] Example 2:

[0150] This example is basically the same as Example 1, except that the copper wire pretreatment step in step (2) is not carried out.

[0151] Example 3:

[0152] (1) Copper wire decontamination

[0153] Use a copper wire with a diameter of 0.1 mm as the metal substrate, soak the copper wire in absolute ethanol for 5 min, and then soak it in 0.05 mol / L dilute hydrochloric acid for 8 min; then wash it with absolute ethanol and water in turn.

[0154] (2) Copper wire pretreatment

[0155] Prepare an aqueous dopamine (PDA) solution with a concentration of 2 mg / mL, and adjust the pH of the PDA solution to 9.0 using Tris-HCl buffer to obtain a dopamine hydrochloride solution; place the cleaned copper wire in the dopamine hydrochloride solution and soak it for 6 h to etch the copper wire.

[0156] (3)Insulating coating of copper wire

[0157] Dissolve styrene-butadiene rubber and zinc fluoride (ZnF2) in the solvent N,N-dimethylformamide, and ultrasonically oscillate for 5 min to fully dissolve and disperse them to prepare a polymer solution with a mass concentration of 5% for styrene-butadiene rubber and 0.5% for ZnF2.

[0158] Use a glass mold to coat the copper wire with the polymer. A semi-cylindrical groove is reserved on the surface of the glass mold. Place one end of the copper wire into the groove, and the other end extends out of the groove. Inject the prepared polymer solution, and immediately place it in a vacuum drying oven. Vacuum dry it at 100 °C for 6 h to form a coating layer containing styrene-butadiene rubber and ZnF2 on the surface of a partial area of the copper wire, and the other part is the bare copper wire.

[0159] (4)Preparation of negative electrode sheet

[0160] Mix graphite, conductive agent Super P, thickening agent sodium carboxymethyl cellulose, and binder styrene-butadiene rubber in a mass ratio of 96:1:1.2:1.8, then add the solvent deionized water and stir evenly to obtain the negative electrode slurry; evenly coat the negative electrode slurry on both sides of the negative electrode current collector copper foil, and embed the above copper wire with a styrene-butadiene rubber coating layer in the negative electrode slurry on one side, dry and cold press to obtain the negative electrode sheet.

[0161] (5)Assembly of three-electrode battery and lithium plating

[0162] Stack the positive electrode sheet of the lithium-ion battery, the separator, and the above negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play a role in isolation, and make the side of the negative electrode sheet with the embedded copper wire face the separator. After stacking, obtain a bare battery cell; place the bare battery cell in the outer packaging shell, dry it and then inject the electrolyte, and vacuum package it.

[0163] Connect the ear of the positive electrode sheet to the positive pole of the power supply, and the exposed part of the copper wire to the negative pole of the power supply. Charge with a constant current of 30 μA for a charge of 50 μAh, so that lithium plating is carried out on the layer of the copper wire facing the positive electrode sheet. Lithium ions pass through the styrene-butadiene rubber coating layer and deposit on the surface of the copper wire, forming a lithium metal layer between the copper wire and the styrene-butadiene rubber coating layer; moreover, lithium ions react with ZnF2 in the styrene-butadiene rubber coating layer to generate lithium zinc alloy (Li-Zn) and lithium fluoride (LiF) on the side of the coating layer close to the lithium metal layer.

[0164] Connect the tab of the negative electrode plate to the positive electrode of the power supply, and connect the exposed part of the copper wire to the negative electrode of the power supply. Charge at a constant current of 30 μA for a charge of 50 μAh, so as to deposit lithium on the layer of the copper wire facing the negative electrode plate. Lithium ions pass through the styrene-butadiene rubber coating layer and deposit on the surface of the copper wire, forming a lithium metal layer between the copper wire and the styrene-butadiene rubber coating layer; moreover, the lithium ions react with ZnF₂ in the styrene-butadiene rubber coating layer to generate lithium-zinc alloy and lithium fluoride on the side of the coating layer close to the lithium metal layer; thus, lithium metal layers are formed on both the front and back sides of the copper wire.

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

[0166] Example 4:

[0167] This example is basically the same as Example 1, except that in step (3), copper fluoride (CuF₂) is used instead of tin fluoride (SnF₂); correspondingly, the lithium alloy in the electron-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 in the polymer solution of step (3), SnF₂ is not added; correspondingly, the electron-insulating ion transport layer does not contain a lithium alloy; at the same time, 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 in the polymer solution of step (3), SnF₂ is not added; correspondingly, the electron-insulating ion transport layer does not contain a lithium alloy.

[0172] Reference electrode life evaluation method:

[0173] 1) Perform a cyclic test on the three-electrode battery, and use 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] ① Stand still for 10 minutes;

[0176] ② Charge at a constant current of 1C to the maximum voltage, and stop charging at a constant voltage until the current is lower than 0.05C;

[0177] ③ Stand still for 10 minutes;

[0178] ④ Discharge at a constant current of 1C to the lower voltage limit;

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

[0180] 3) Negative electrode potential monitoring

[0181] In step 2), monitor the negative electrode potential in real time during the test, and calculate the lowest negative electrode potential during the constant voltage charging process in step ②, denoted as V n , where n is the number of cycles.

[0182] 4) Test life evaluation

[0183] When the absolute value of V n - V n-1 is greater than 0.1 V, it is regarded as an abnormal test once. When there are more than five accumulative abnormal tests or more than three consecutive abnormal tests, the life of the reference electrode is regarded as abnormal. 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 batteries in each example and comparative example are shown in Table 1. The reference electrode life in Table 1 is the data rounded to the nearest ten.

[0185] Table 1

[0186]

[0187] As can be seen from Table 1, the reference electrodes in the three - electrode batteries of each example of the present application have a long service life. In Comparative Example 1 and Comparative Example 2, SnF2 is not added to the polymer solution; correspondingly, the lithium alloy is not contained in the electron - insulating ion - transport layer, and the life of the reference electrode therein decreases significantly.

[0188] The above descriptions of the respective embodiments tend to emphasize the differences between the respective embodiments. Their similarities or similarities can be referred to each other. For the sake of brevity, they will not be elaborated 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 embodiments having the same composition and the same function and effect as the technical idea within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of 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 plate, a negative electrode plate, a separator, and a reference electrode; The separator is disposed between the positive electrode plate and the negative electrode plate; the reference electrode is disposed between the negative electrode plate and the separator, or the reference electrode is disposed between the positive electrode plate and the separator, or the reference electrode is disposed inside the negative electrode plate; The reference electrode includes a metal matrix, a lithium metal layer, and an electron-insulating ion-transporting layer. The lithium metal layer coats the surface of the metal matrix, and the electron-insulating ion-transporting layer coats the surface of the lithium metal layer; the electron-insulating ion-transporting layer 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 electron-insulating ion-transporting layer close to the lithium metal layer; The lithium salt is located on the side of the electron-insulating ion-transporting layer close to the lithium metal layer.

2. The three-electrode battery according to claim 1, wherein, The lithium alloy includes one or more of lithium-tin alloy, lithium-copper alloy, and 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 poly(vinylidene 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 thickness of the lithium metal layer is 10 nm to 50 nm.

6. The three-electrode battery according to any one of claims 1 to 2, characterized in that The thickness of the electron-insulating ion-transporting layer is 3 μm to 6 μm.

7. The three-electrode battery according to any one of claims 1 to 2, characterized in that, The metal matrix includes one or more of copper, gold, and silver.

8. The three-electrode battery according to any one of claims 1 to 2, characterized in that, The reference electrode is disposed between the negative electrode plate and the separator, and the reference electrode is attached to the surface of the negative electrode plate.

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

10. A reference electrode, characterized in that, It includes a metal matrix, a lithium metal layer, and an electron-insulating ion-transporting layer. The lithium metal layer coats the surface of the metal matrix, and the electron-insulating ion-transporting layer coats the surface of the lithium metal layer; the electron-insulating ion-transporting layer 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 electron-insulating ion-transporting layer close to the lithium metal layer; the lithium salt is located on the side of the electron-insulating ion-transporting layer close to the lithium metal layer.

11. A method for preparing a reference electrode, characterized in that, It includes the following steps: Coat an electron-insulating ion-transporting precursor layer on the surface of the metal matrix. The electron-insulating ion-transporting precursor layer includes an organic polymer matrix and a non-lithium metal halide salt located in the organic polymer matrix; Lithium plate the metal matrix coated with the electron-insulating ion-transporting precursor layer so that the non-lithium metal halide salt forms a lithium alloy and a lithium salt to obtain an electron-insulating ion-transporting layer, and a lithium metal layer is formed between the metal matrix and the electron-insulating ion-transporting layer; the lithium alloy and the lithium salt are located on the side of the electron-insulating ion-transporting layer close to the lithium metal layer.

12. The preparation method of the reference electrode according to claim 11, characterized in that, Coating an electron-insulating ion-transporting precursor layer on the surface of the metal matrix includes the following steps: A solution containing an organic polymer and a non-lithium metal halide salt is applied to the surface of the metal matrix, and after curing, the electron-insulating ion-transport precursor layer is formed on the surface of the metal matrix; Alternatively, a solution containing an organic polymer monomer and a non-lithium metal halide salt is applied to the surface of the metal matrix, and after reaction and curing, the electron-insulating ion-transport precursor layer is formed on the surface of the metal matrix.

13. The preparation method of the reference electrode according to any one of claims 11 to 12, characterized in that, Lithium plating of the metal matrix coated with the electron-insulating ion-transport precursor layer includes the following steps: A three-electrode battery is composed of a positive electrode plate, a negative electrode plate, a separator, and a metal matrix coated with the electron-insulating ion-transport precursor layer of a lithium-ion battery, wherein the separator is located between the positive electrode plate and the negative electrode plate, and the metal matrix is located between the negative electrode plate and the separator; Connect the positive electrode plate to the positive electrode of the power supply and the metal matrix to the negative electrode of the power supply, and charge; Connect the negative electrode plate to the positive electrode of the power supply and the metal matrix to the negative electrode of the power supply, and charge.

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

15. An electrical device, characterized in that, A three-electrode battery according to any one of claims 1 to 9 is included.

Images