Functional composite current collector, preparation method thereof, and fluoride ion battery

Abstract

The present application relates to the technical field of secondary batteries, and in particular to a functional composite current collector, a preparation method thereof, and a fluoride ion battery. The functional composite current collector comprises a support layer, a conductive layer provided on at least one surface of the support layer, and a primer layer provided on the surface of the conductive layer away from the support layer; the support layer comprises a polymer base film and a toughening agent dispersed in the polymer base film; the primer layer comprises a first binder and a conductive agent dispersed in the first binder, the functional groups on the surface of the conductive agent carry a negative charge in the solution, and the functional groups comprise one or more of hydroxyl, carboxyl, halogen, and oxygen-metal bonds. The functional composite current collector provided by the present application has high structural stability and strong adhesion to the active material layer, and can significantly improve the cycle stability of the fluoride ion battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a functional composite current collector, a preparation method thereof, and a fluoride ion battery. Background Art

[0002] Fluoride ion battery is a kind of battery that uses fluoride ions (F - Fluoride-ion batteries, which shuttle charge carriers between the positive and negative electrodes, are secondary batteries that operate on a similar principle to lithium-ion batteries. Fluorine, the most electronegative element, exhibits excellent oxidation resistance, making it a suitable candidate for high-voltage cathode materials. Fluorine reserves are abundant, with high annual production, effectively controlling battery costs. Fluoride-ion batteries also exhibit excellent safety and avoid dendrite growth during charge and discharge cycles, potentially challenging lithium-ion batteries in the energy storage sector. However, conventional fluoride-ion batteries suffer from poor cycling performance, limiting their application in this field. Summary of the Invention

[0003] Based on this, it is necessary to provide a functional composite current collector and a preparation method thereof and a fluoride ion battery to solve the problem of poor cycle performance of traditional fluoride ion batteries.

[0004] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0005] In a first aspect of the present application, a functional composite current collector is provided, comprising a support layer, a conductive layer disposed on at least one surface of the support layer, and a primer layer disposed on a surface of the conductive layer away from the support layer;

[0006] The support layer includes a polymer base film and a toughening agent dispersed in the polymer base film;

[0007] The primer layer includes a first binder and a conductive agent dispersed in the first binder. The functional groups on the surface of the conductive agent carry negative charges in the solution. The functional groups include one or more of hydroxyl groups, carboxyl groups, halogen groups, and oxygen-metal bonds.

[0008] In some embodiments, the conductive agent includes one or more of carboxylated carbon nanotubes, polyhydroxy fullerenes, and MXene materials; the MXene material includes Ti3C2T x 、Ti2CT x 、Ti3CNT x 、Ta4C3T x 、V2CT x 、V3C2T x 、Mo2CT x and Mo2TiC2T xOne or more of, wherein T includes one or more of -OH, -F and -O, and x>0.

[0009] In some embodiments, the first binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, hydrogenated nitrile rubber, polyvinyl alcohol, polymethacrylic acid, polymethyl methacrylate, polyacrylic acid, sodium polyacrylate, polyacrylamide, sodium alginate, sodium carboxymethyl cellulose and carboxymethyl chitosan.

[0010] In some embodiments, the mass ratio of the first binder to the conductive agent is 1:(0.1-4).

[0011] In some embodiments, the base coating further includes a dispersant, which includes one or more of polyvinyl pyrrolidone, sodium polyacrylate, sodium lignin sulfonate, and sodium polystyrene sulfonate, and the mass ratio of the first binder to the dispersant is 1:(0.1~1).

[0012] In some embodiments, the primer layer has a thickness of 0.5 μm to 3 μm.

[0013] In some embodiments, the surface roughness of the primer layer is 100 nm to 800 nm.

[0014] In some embodiments, the peel strength of the primer layer is 14 N / 25 mm to 30 N / 25 mm.

[0015] In some embodiments, the toughening agent includes bacterial cellulose, a polydopamine layer coated on the bacterial cellulose, and an amino-modified layer grafted onto the polydopamine layer.

[0016] In some embodiments, the preparation method of the toughening agent comprises the following steps:

[0017] mixing bacterial cellulose, dopamine, and a buffer solution, and allowing the dopamine to self-polymerize to form a polydopamine layer covering the bacterial cellulose, thereby obtaining an intermediate;

[0018] The intermediate is dispersed in a mixed solution containing an aminating agent, and the aminating agent is grafted onto the polydopamine layer to form the amino-modified layer, thereby obtaining the toughening agent.

[0019] In some embodiments, the mass ratio of the bacterial cellulose, the dopamine, and the amination reagent is 1:(0.5-2):(0.5-5).

[0020] In some embodiments, the bacterial cellulose has a diameter of 10 nm to 200 nm, a length of 100 nm to 2000 nm, and an aspect ratio of 0.5 to 200.

[0021] In some embodiments, the amination agent includes one or more of ethylenediamine, histamine, polyethyleneimine, and cetyltrimethylammonium bromide.

[0022] In some embodiments, the mass ratio of the polymer base film to the toughening agent is 100:(1-10).

[0023] In some embodiments, the thickness of the support layer is 4 μm to 8 μm.

[0024] In some embodiments, the functional composite current collector further comprises a first safety coating layer, wherein the first safety coating layer is disposed between the support layer and the conductive layer;

[0025] The first safety coating comprises a second binder and a phase change material in a mass ratio of (2-5): (95-98), wherein the melting point of the phase change material is 85°C-120°C; or

[0026] The first safety coating includes a second binder and microcapsules in a mass ratio of (2~10):(90~98), the microcapsules include a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material is 1:(1.2~40), and the melting point of the phase change material is 85°C~120°C.

[0027] In a second aspect of the present application, a method for preparing the functional composite current collector as described above is provided, comprising the following steps:

[0028] Melting and blending a polymer resin and a toughening agent, and subjecting the resulting mixture to a film-forming process, wherein the polymer resin forms a polymer base film, and the toughening agent is dispersed in the polymer base film to obtain a support layer;

[0029] forming a conductive layer on at least one surface of the support layer;

[0030] A primer slurry containing a first binder and a conductive agent is applied on the conductive layer and dried to form a primer layer.

[0031] In a third aspect of the present application, a fluoride ion battery is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet and / or the negative electrode sheet comprises the functional composite current collector as described above, or comprises a functional composite current collector prepared by the preparation method of the functional composite current collector as described above.

[0032] In some embodiments, the isolation film includes a base film and a second security coating applied to at least one surface of the base film;

[0033] The second safety coating comprises a second binder and a phase change material in a mass ratio of (2-5): (95-98), wherein the melting point of the phase change material is 85°C-120°C; or

[0034] The second safety coating includes a second binder and microcapsules in a mass ratio of (2~10):(90~98), the microcapsules include a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material is 1:(1.2~40), and the melting point of the phase change material is 85℃~120℃.

[0035] This application has at least the following beneficial effects:

[0036] The functional composite current collector provided by the present application includes a support layer, a conductive layer and a bottom coating layer. Among them, the bottom coating layer includes a first binder and a conductive agent. The functional groups on the surface of the conductive agent carry a negative charge in the solution environment, which can generate electrostatic repulsion on fluoride ions, prevent fluoride ions from migrating to the interface between the functional composite current collector and the active material layer, reduce the probability of the active material at the interface participating in the conversion reaction, and the probability of stress and strain generated at the interface is reduced accordingly, thereby improving the adhesion of the active material layer to the functional composite current collector, thereby improving the cycle performance of the fluoride ion battery. Compared with traditional composite current collectors, the bottom coating layer has a high surface roughness and good bonding performance, which effectively enhances the peel strength between the active material layer and the functional composite current collector, which is beneficial to prevent the active material layer from detaching or peeling off. At the same time, the support layer includes a polymer base film and a toughening agent, which can enhance the tensile strength, elongation at break and toughness of the support layer, improve the mechanical properties of the functional composite current collector, and help improve the cycle performance of the battery. Therefore, the functional composite current collector provided by the present application has high structural stability and strong adhesion to the active material layer, which can significantly improve the cycle stability of the fluoride ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0038] Figure 1 Schematic diagram of the structure of a functional composite current collector in some embodiments;

[0039] Figure 2 Schematic diagrams of the structures of functional composite current collectors in other embodiments;

[0040] Figure 3Schematic diagram of a process for preparing a functional composite current collector in some embodiments;

[0041] Figure 4 Schematic diagram of the structure of the isolation membrane in some embodiments.

[0042] Reference numerals: 11, support layer; 12, conductive layer; 13, primer layer; 14, first security coating layer; 21, base film; 22, second security coating layer. DETAILED DESCRIPTION

[0043] To facilitate understanding of the present application, the present application will be further described in detail below with reference to specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0045] In this application, the meaning of "and / or" includes any and all combinations of one or more related listed items. "One or more" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0046] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges subsumed therein.

[0047] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] In this application, “above” or “below” includes the number itself. For example, “1 below” includes 1.

[0049] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0050] In this application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23℃±2℃, 25℃±5℃ or 20℃±5℃.

[0051] The electrode sheet is a crucial component of a fluoride ion battery. It includes a current collector and an active material layer disposed on at least one surface of the current collector. Fluoride ion batteries typically use conversion-type active materials for their active material layers. For example, a metal fluoride (such as CuF2) is used as the positive electrode active material. During discharge, the fluoride ions in the metal fluoride are released and reduced to elemental metal. During charge, the metal and fluoride ions combine to regenerate the metal fluoride. Consequently, conversion-type active materials undergo changes in chemical composition and phase structure during the charge-discharge process, accompanied by significant volume changes. This can cause significant stress and strain at the interface between the active material layer and the current collector, and can even cause the active material layer to completely detach from the current collector, degrading the cyclic performance of the fluoride ion battery. Alternatively, the current collector can be made of metal foil or a composite current collector. Compared to metal foil, composite current collectors are lighter at the same thickness, resulting in a higher energy density in the resulting fluoride ion battery. However, the poor mechanical properties of composite current collectors can also affect the cyclic performance of fluoride ion batteries.

[0052] Based on this, in the first aspect of the present application, a functional composite current collector is provided to solve the problem of poor cycle performance of traditional fluoride ion batteries.

[0053] In some embodiments, as Figure 1As shown, the functional composite current collector includes a support layer 11 , a conductive layer 12 disposed on both surfaces of the support layer 11 , and a primer layer 13 disposed on a surface of the conductive layer 12 away from the support layer 11 .

[0054] The support layer 11 includes a polymer base film and a toughening agent dispersed in the polymer base film;

[0055] The primer layer 13 includes a first binder and a conductive agent dispersed in the first binder. The functional groups on the surface of the conductive agent carry negative charges in the solution. The functional groups include one or more of hydroxyl groups, carboxyl groups, halogen groups, and oxygen atoms.

[0056] The functional composite current collector provided in this application includes a support layer 11, a conductive layer 12 and a primer layer 13. Among them, the primer layer 13 includes a first binder and a conductive agent. The functional groups on the surface of the conductive agent carry a negative charge in the solution environment, which can generate electrostatic repulsion on the fluoride ions, prevent the fluoride ions from migrating to the interface between the functional composite current collector and the active material layer, reduce the probability of the active material at the interface participating in the conversion reaction and undergoing a significant volume change, and the probability of stress and strain at the interface is reduced accordingly, thereby improving the adhesion of the active material layer to the functional composite current collector, thereby improving the cycle performance of the fluoride ion battery. Compared with traditional composite current collectors, the primer layer 13 has a high surface roughness and good bonding performance, which effectively enhances the peel strength between the active material layer and the functional composite current collector, which is beneficial to prevent the active material layer from detaching or peeling off. At the same time, the support layer 11 includes a polymer base film and a toughening agent, which can enhance the tensile strength, elongation at break and toughness of the support layer 11, improve the mechanical properties of the functional composite current collector, and help improve the cycle performance of the battery. Therefore, the functional composite current collector provided by the present application has high structural stability and strong adhesion to the active material layer, which can significantly improve the cycle stability of the fluoride ion battery.

[0057] The following is some description about the support layer 11 .

[0058] In some embodiments, the material of the polymer-based film includes one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), polyvinyl chloride (PVC), polystyrene (PS), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Further, the material of the polymer-based film includes one or more of polypropylene (PP), polyimide (PI), and polyethylene terephthalate (PET).

[0059] In some embodiments, the toughening agent includes bacterial cellulose, a polydopamine layer coated on the bacterial cellulose, and an amino-modified layer grafted onto the polydopamine layer.

[0060] In some embodiments, the method for preparing the toughening agent comprises the following steps:

[0061] S110: mixing bacterial cellulose, dopamine, and a buffer solution to allow dopamine to self-polymerize to form a polydopamine layer coating the bacterial cellulose, thereby obtaining an intermediate;

[0062] S120: dispersing the intermediate in a mixed solution containing an aminating agent, so that the aminating agent is grafted onto the polydopamine layer to form an amino-modified layer, thereby obtaining a toughening agent.

[0063] In this application, the preparation mechanism of the toughening agent is as follows: Dopamine (DA) contains amino groups and catechol functional groups (also known as catechol functional groups), which can spontaneously polymerize to form polydopamine (PDA) under neutral or slightly alkaline conditions. PDA is coated on the surface of bacterial cellulose to form a polydopamine layer. PDA provides abundant functional groups and active sites, which can undergo covalent cross-linking reactions with amino groups (or imino groups) in the amination reagent through Michael addition, thereby forming an amino-modified layer. As a result, the toughening agent surface contains a large number of amino groups, which helps to strengthen its bonding with the polymer base film, thereby enhancing the toughening effect of the support layer 11.

[0064] In some embodiments, the mass ratio of bacterial cellulose, dopamine, and amination agent is 1:(1-2):(1-5). As examples, the mass ratio of bacterial cellulose to dopamine includes, but is not limited to, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2, and the mass ratio of bacterial cellulose to amination agent includes, but is not limited to, 1:1, 1:2, 1:3, 1:4, or 1:5. Furthermore, the mass ratio of bacterial cellulose, dopamine, and amination agent is 1:1:1.

[0065] In some embodiments, the bacterial cellulose has a diameter of 10 nm to 200 nm, a length of 100 nm to 2000 nm, and an aspect ratio of 0.5 to 200. As an example, the diameter of the bacterial cellulose includes but is not limited to 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, or 200 nm, the length includes but is not limited to 100 nm, 200 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm, 1800 nm, or 2000 nm, and the aspect ratio includes but is not limited to 0.5, 1, 5, 10, 20, 50, 80, 100, 120, 150, 180, or 200.

[0066] In some embodiments, the buffer solution comprises a Tris-HCl buffer solution, i.e., a Tris-HCl buffer solution. The pH of the Tris-HCl buffer solution is 7-9, and the concentration is 10 mM to 20 mM. Furthermore, the pH of the Tris-HCl buffer solution is 8.5, and the concentration is 10 mM.

[0067] In some embodiments, the mass fraction of the bacterial cellulose in the buffer solution is 0.1% to 1%. Furthermore, the mass fraction of the bacterial cellulose in the buffer solution is 0.5%.

[0068] In some embodiments, the mass fraction of dopamine in the buffer solution is 0.1% to 1%. Furthermore, the mass fraction of dopamine in the buffer solution is 0.5%.

[0069] In some embodiments, in step S110 , mixing bacterial cellulose, dopamine, and a buffer solution comprises the following steps: dispersing bacterial cellulose in a buffer solution, and adding dopamine under ultrasonic conditions.

[0070] In some embodiments, in step S110, dopamine is self-polymerized to form a polydopamine layer coating bacterial cellulose, comprising the following steps: continuous stirring for 12 h to 36 h at a pH of 7 to 9, a temperature of 10° C. to 40° C., and a rotation speed of 100 rpm to 1000 rpm.

[0071] In some embodiments, in step S110 , after the self-polymerization reaction, the following step is further included: removing residual dopamine and unstable polydopamine on the surface of the intermediate by water washing.

[0072] In some embodiments, the amination reagent includes one or more of ethylenediamine (EDA), histamine (1H-imidazole-4-ethylamine), polyethyleneimine (PEI), and cetyltrimethylammonium bromide (CTAB). Further, the amination reagent is polyethyleneimine (PEI).

[0073] In some embodiments, the mass fraction of the amination reagent in the mixed solution is 0.1% to 1%, including but not limited to 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 1%.

[0074] In some embodiments, grafting an amination reagent onto a polydopamine layer to form an amino-modified layer comprises the following steps: continuously stirring for 6 h to 24 h at a temperature of 40° C. to 60° C. and a rotation speed of 100 rpm to 1000 rpm.

[0075] In some embodiments, in step S120 , after the grafting reaction, the following step is further included: removing the unreacted amination reagent on the surface of the toughening agent by water washing.

[0076] In some embodiments, the mass ratio of the polymer base film to the toughening agent is 100:(1-10), including but not limited to 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, or 100:10. Furthermore, the mass ratio of the polymer base film to the toughening agent is 100:(1-4).

[0077] Therefore, adding an appropriate amount of toughening agent to the support layer 11 can fully exert its toughening effect, enabling it to buffer stress and maintain structural stability during battery preparation and operation, thereby providing a guarantee for the stable performance of the battery.

[0078] In some embodiments, the thickness of the support layer 11 is 4 μm to 8 μm, including but not limited to 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm.

[0079] The following is some description about the conductive layer 12 .

[0080] In this application, if Figure 1 As shown, the support layer 11 has two surfaces opposite to each other in its thickness direction, and the conductive layer 12 is disposed on the two opposite surfaces of the support layer 11. However, the present application is not limited thereto, and in some other embodiments, the conductive layer 12 may also be disposed on either of the two opposite surfaces of the support layer 11.

[0081] In some embodiments, the conductive layer 12 is made of one or more of stainless steel, copper (Cu), nickel (Ni), and aluminum (Al).

[0082] If the functional composite current collector is applied to the positive electrode, the conductive layer 12 may be made of aluminum (Al).

[0083] If the functional composite current collector is applied to the negative electrode, the conductive layer 12 may be made of copper (Cu), nickel (Ni) or stainless steel.

[0084] In some embodiments, the thickness of the conductive layer 12 is 0.5 μm to 4 μm, including but not limited to 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm.

[0085] The following is some description about the primer layer 13 .

[0086] In some embodiments, in the primer layer 13, the functional groups on the surface of the conductive agent carry a negative charge in the solution, and the functional groups include one or more of a hydroxyl group (-OH), a carboxyl group (-COOH), a halogen (-F, -Cl, -Br, or -I), and an oxygen-metal bond (-O).

[0087] It is understood that hydroxyl (-OH) and carboxyl (-COOH) groups can be negatively charged (-O - and -COO - Halogens (such as -F) inherently have high electronegativity, which can impart a negative charge to the surface of the conductive agent. Oxygen-metal bonds (-O, or MO bonds) are stable chemical bonds formed by oxygen atoms joining surface metal atoms through substitution or adsorption. The high electronegativity of oxygen atoms imparts a certain degree of negative charge to the surface of MXene materials, especially in solution.

[0088] In this application, the surface charge of the conductive agent can be tested using the Zeta potential test method. The test solution can be water or an organic solvent. The test sample is dispersed in deionized water at a mass fraction of 0.01% to 0.1% to form a suspension, which is then tested using a Zeta potential meter.

[0089] In some embodiments, in the primer layer 13 , the conductive agent includes one or more of carboxylated carbon nanotubes, polyhydroxyfullerenes, and MXene materials.

[0090] In this application, the surface of the carboxylated carbon nanotubes contains a large number of carboxyl groups, the surface of the polyhydroxyfullerene contains a large number of hydroxyl groups, and the surface of the MXene material contains a large number of active functional groups, such as -OH, -F, or -O. These functional groups carry a negative charge in a solution environment through deprotonation or adsorption, which can provide a strong electrostatic repulsion, preventing fluoride ions from migrating to the interface between the functional composite current collector and the active material layer, and effectively improving the adhesion between the active material layer and the functional composite current collector.

[0091] In some embodiments, the molecular formula of the MXene material is M n+1 X n T x .

[0092] Wherein, n=1, 2, 3; M represents a transition metal element, M includes one or more of Ti, Ta, Mo, V, Sr and Zr; X represents one or more of carbon and nitrogen; T represents a surface active functional group, T includes one or more of -OH, -F and -O, x represents the number of T, and x>0.

[0093] In some embodiments, the MXene material includes Ti3C2Tx 、Ti2CT x 、Ti3CNT x 、Ta4C3T x 、V2CT x 、V3C2T x 、Mo2CT x and Mo2TiC2T x One or more of .

[0094] In some embodiments, the MXene material includes one or more of a multilayer MXene material and a single layer MXene material. The thickness of the multilayer MXene material is 5 μm to 50 μm, and the thickness of the single layer MXene material is 0.5 nm to 5 nm.

[0095] In some embodiments, the preparation method of MXene material comprises the following steps: placing a MAX precursor in a solution containing hydrogen ions (H + ) and fluoride ions (F - ) in an etching solution and subjected to purification treatment to prepare MXene materials.

[0096] In some embodiments, the MAX precursor includes one or more of Ti3AlC2, Ti2AlC, Ti3AlCN, Ta4AlC3, V2AlC, V3AlC2, Mo2AlC, and Mo2TiAlC2.

[0097] In some embodiments, the etching solution contains one or more of HF, HCl, and fluoride salts, wherein the fluoride salts include one or more of lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), aluminum fluoride (AlF3), and ammonium fluoride (NH4F).

[0098] In some embodiments, the etching solution is an HF solution, and the concentration of HF is 6 mol / L to 12 mol / L, including but not limited to 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L.

[0099] In some embodiments, the etching solution is a mixed solution containing HCl and a fluoride salt, wherein the molar ratio of HCl to the fluoride salt is 1:(0.1-0.5), including but not limited to 1:0.1, 1:0.2, 1:0.3, 1:0.4, or 1:0.5. The fluoride salt can be one or more of LiF, NaF, and KF.

[0100] In some embodiments, the volume mass ratio of the etching solution to the MAX precursor is 10 mL / g to 20 mL / g, including but not limited to 10 mL / g, 12 mL / g, 14 mL / g, 16 mL / g, 18 mL / g or 20 mL / g.

[0101] In some embodiments, the etching reaction includes the following steps: etching at 20° C. to 50° C. for 12 hours to 48 hours. As an example, the etching reaction temperature can be 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or 50° C., and the etching reaction time can be 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, or 48 hours.

[0102] In some embodiments, the purification treatment includes the following steps: repeatedly centrifuging and washing the reaction liquid after the etching reaction with HCl solution and deionized water until the pH value of the upper liquid after centrifugation is ≥6 to obtain a washed product; dispersing the washed product in deionized water and ultrasonicating it under an inert gas atmosphere to obtain a dispersion; and then high-speed centrifuging and freeze-drying the dispersion to obtain a MXene material.

[0103] In some embodiments, the first binder includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), polymethyl methacrylate (PMMA), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), and carboxymethyl chitosan (CMCS).

[0104] If the functional composite current collector is applied to the positive electrode sheet, the first binder can be selected from 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), sodium carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCS), and can further be selected from SBR and CMC.

[0105] If the functional composite current collector is applied to the negative electrode sheet, the first binder can be selected from one or more of polyvinylidene fluoride (PVDF), sodium alginate (SA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), hydrogenated nitrile rubber (HNBR), polytetrafluoroethylene (PTFE) and polyacrylic acid (PAA), and PVDF can be further selected.

[0106] In some embodiments, the mass ratio of the first binder to the conductive agent is 1:(0.1-4), including but not limited to 1:0.1, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0107] In some embodiments, the primer layer 13 further includes a dispersant, which includes one or more of polyvinyl pyrrolidone (PVP), sodium polyacrylate (PAAS), sodium lignin sulfonate, and sodium polystyrene sulfonate (PSS). Furthermore, the dispersant is polyvinyl pyrrolidone (PVP).

[0108] In some embodiments, the mass ratio of the first binder to the dispersant is 1:(0.1-1), including but not limited to 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0109] In some embodiments, the thickness of the primer layer 13 is 0.5 μm to 3 μm, including but not limited to 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0110] In some embodiments, the surface roughness of the primer layer 13 is 100 nm to 800 nm, including but not limited to 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, or 800 nm;

[0111] In some embodiments, the peel strength of the primer layer 13 is 14N / 25mm~30N / 25mm, including but not limited to 14N / 25mm, 16N / 25mm, 18N / 25mm, 20N / 25mm, 22N / 25mm, 24N / 25mm, 26N / 25mm, 28N / 25mm or 30N / 25mm.

[0112] In some embodiments, as Figure 2 As shown, the functional composite current collector further includes a first safety coating 14, which is disposed between the support layer 11 and the conductive layer 12. The first safety coating 14 includes a second binder and a phase change material in a mass ratio of (2-5):(95-98), and the melting point of the phase change material is 85°C to 120°C. As examples, the mass ratio of the second binder to the phase change material includes, but is not limited to, 2:98, 3:97, 4:96, or 5:95, and the melting point of the phase change material includes, but is not limited to, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C.

[0113] As a result, when the battery's internal temperature rises abnormally to the melting point of the phase-change material, the phase-change material absorbs the heat and melts, causing the conductive layer 12 on the surface of the first safety coating 14 to fall off, thereby suppressing abnormal circuit currents and improving battery safety. Furthermore, under normal operating conditions, the first safety coating 14 can also improve the mechanical properties of the functional composite current collector.

[0114] In some embodiments, the second binder includes one or more of polyimide (PI), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), polymethyl methacrylate (PMMA), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), sodium carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCS), and may further be PVDF or PI.

[0115] In some embodiments, the phase change material includes one or more of paraffin wax, chlorinated paraffin wax, pearlescent wax, and stearic acid. The paraffin wax may include high-melting-point paraffins such as paraffin No. 90 (melting point range 85°C-90°C), paraffin No. 95 (melting point range 90°C-95°C), and paraffin No. 105 (melting point range 100°C-105°C). The chlorinated paraffin may include chlorinated paraffin-70 (melting point range 95°C-120°C). Pearlescent wax is a high-melting-point wax commonly used in the manufacture of pearlescent pigments and coatings, exhibiting excellent stability and pearlescent effects. A pearlescent wax with a melting point of 88°C-93°C may be used.

[0116] In other embodiments, the first safety coating 14 may further include a second binder and microcapsules in a mass ratio of (2-10):(90-98), the microcapsules including a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material being 1:(1.2-40), and the melting point of the phase change material being 85°C-120°C. For example, the mass ratio of the second binder to the microcapsules is 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, or 10:90, and the mass ratio of the flame retardant to the phase change material includes, but is not limited to, 1:1.2, 1:2, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, or 1:40.

[0117] Therefore, the introduction of flame retardants helps improve the battery's flame retardancy, inhibiting exothermic chain reactions and further enhancing battery safety. Furthermore, the phase change material coating the flame retardant prevents loss of the flame retardant under normal operating conditions, ensuring its stable flame retardant effect under abnormal operating conditions.

[0118] In some embodiments, the flame retardant includes one or more of 3-thiopheneboronic acid, pentafluoroethoxycyclotriphosphazene, hexaphenoxycyclotriphosphazene, hexachlorotriphosphazene, Li[P(DPC)3], and poly(ethyl phosphate-ethylene glycol) co-oligomer.

[0119] In some embodiments, in the microcapsules, the particle size of the flame retardant is 40 nm to 400 nm, including but not limited to 40 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0120] In some embodiments, in the microcapsule, the thickness of the phase change material is 400 nm to 1000 nm, including but not limited to 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm.

[0121] In some embodiments, the first security coating 14 has a thickness of 0.5µm to 1.5µm, including but not limited to 0.5µm, 0.6µm, 0.7µm, 0.8µm, 0.9µm, 1µm, 1.1µm, 1.2µm, 1.3µm, 1.4µm or 1.5µm.

[0122] In a second aspect of the present application, a method for preparing a functional composite current collector is provided, which is used to prepare the above-mentioned functional composite current collector.

[0123] In some embodiments, as Figure 3 As shown, the preparation method of the functional composite current collector includes the following steps:

[0124] S210: melt-blending the polymer resin and the toughening agent, and performing a film-forming treatment on the resulting mixture, wherein the polymer resin forms a polymer base film, and the toughening agent is dispersed in the polymer base film to obtain a support layer;

[0125] S220: forming a conductive layer on at least one surface of the supporting layer;

[0126] S230: coating a primer slurry containing a first binder and a conductive agent on the conductive layer, and drying the slurry to obtain a primer layer.

[0127] The following is a detailed description of the preparation method of the functional composite current collector in a step-by-step manner.

[0128] S210: melt-blending the polymer resin and the toughening agent, and performing a film-forming treatment on the obtained mixture, wherein the polymer resin forms a polymer base film, and the toughening agent is dispersed in the polymer base film to obtain a support layer.

[0129] In some embodiments, the temperature of melt blending is 170°C to 450°C, including but not limited to 170°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C or 450°C.

[0130] In some embodiments, the melt blending time is 0.5 h to 8 h, including but not limited to 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h.

[0131] In some embodiments, the film forming method includes one or more of compression molding, hot pressing molding, autoclave molding, and calendering molding, and hot pressing molding may be further selected.

[0132] In some embodiments, after the film forming process, the following step is further included: increasing the surface roughness of the support layer by plasma etching, thereby improving the peeling strength between the support layer and other film layers.

[0133] In some embodiments, the plasma etching process includes the following steps: evacuating to a vacuum of 5×10 -5 Pa~8×10 - 5 Pa, an inert gas is introduced at a flow rate of 10 sccm~100 sccm, and plasma etching treatment is performed under the conditions of a working pressure of 0.5 Pa~5 Pa and a working power of 20 W~80 W; wherein the inert gas includes one or more of helium, neon, argon, krypton and xenon.

[0134] S220: forming a conductive layer on at least one surface of the support layer.

[0135] In some embodiments, the conductive layer is prepared by magnetron sputtering.

[0136] In some embodiments, the method for preparing the conductive layer comprises the following steps: vacuuming to ≤5×10 -5 Pa, an inert gas is introduced at a flow rate of 50 sccm~100 sccm, and DC magnetron sputtering coating is performed under the conditions of a sputtering pressure of 0.5 Pa~5 Pa and a sputtering power of 100 W~200 W to form a conductive layer; wherein the inert gas includes one or more of helium, neon, argon, krypton and xenon.

[0137] S230: coating a primer slurry containing a first binder and a conductive agent on the conductive layer, and drying the slurry to obtain a primer layer.

[0138] In some embodiments, a method for preparing a primer layer comprises the following steps: mixing a conductive agent, a dispersant, a first binder, and a first solvent to form a primer slurry, applying the primer slurry onto the conductive layer, and vacuum drying the primer slurry at 60°C to 80°C for 48 to 72 hours. The first solvent comprises one or more of N-methylpyrrolidone (NMP) and water, and the water may be deionized water, pure water, or ultrapure water. The primer slurry has a solids content of 5% to 20%, including but not limited to 5%, 8%, 10%, 12%, 15%, 18%, or 20%. The vacuum drying temperature includes but is not limited to 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, or 80°C, and the vacuum drying time includes but is not limited to 48 hours, 50 hours, 55 hours, 60 hours, 65 hours, 70 hours, or 72 hours.

[0139] In some embodiments, after step S210, the following steps are further included: forming a first safety coating layer on at least one surface of the support layer, and sequentially forming a conductive layer and a primer layer on the first safety coating layer.

[0140] In some embodiments, a method for preparing a first safety coating comprises the following steps: mixing a phase change material, a second binder, and a second solvent to form a safety slurry, or mixing a safety capsule, a second binder, and a second solvent to form a first safety slurry; applying the first safety slurry to at least one surface of a support layer by extrusion molding, and vacuum drying at 60°C to 70°C for 12 to 24 hours to form the first safety coating. The second solvent comprises one or more of N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF); the solids content of the safety slurry is 5% to 20%, including but not limited to 5%, 8%, 10%, 12%, 15%, 18%, or 20%; the vacuum drying temperature includes but is not limited to 60°C, 62°C, 64°C, 66°C, 68°C, or 70°C, and the vacuum drying time includes but is not limited to 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0141] In some embodiments, the preparation method of the safety capsule includes the following steps: heating the phase change material to melt, impregnating the flame retardant into the molten phase change material, coating the flame retardant surface with a layer of phase change material by melt impregnation, cooling, solidifying, and crushing to obtain the safety capsule.

[0142] It is understandable that after forming the first safety coating, during the process of preparing the conductive layer by magnetron sputtering, the temperature in the reaction chamber should be controlled below the melting point of the phase change material to avoid loss of the first safety coating.

[0143] In a third aspect of the present application, a fluoride ion battery is provided. In the present application, the fluoride ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the cycle, fluoride ions (F - ) shuttles back and forth between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing fluoride ions to pass through. The electrolyte, located between the positive and negative electrodes, primarily conducts fluoride ions.

[0144] In some embodiments, the positive electrode sheet and / or the negative electrode sheet includes the functional composite current collector described above.

[0145] In some embodiments, the positive electrode sheet includes the functional composite current collector as described above and a positive electrode active layer covering at least one surface of the functional composite current collector.

[0146] In some embodiments, the positive electrode active layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder, wherein the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80-95):(2.5-10):(2.5-10), and can further be 80:10:10.

[0147] In some embodiments, the positive electrode active material includes a metal fluoride and a modified compound thereof. The metal fluoride includes one or more of CuF2, FeF3, BiF3, LaF3, MgF2, NiF2, and PbF2, and the modified compound of the metal fluoride can be one or more of mixed modification, doping modification, and surface coating modification. Furthermore, the positive electrode active material is a composite material of a metal fluoride and carbon, and the carbon can be one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers.

[0148] In some embodiments, the positive electrode binder includes one or more of polyvinylidene fluoride (PVDF), sodium alginate (SA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), hydrogenated nitrile rubber (HNBR), polytetrafluoroethylene (PTFE) and polyacrylic acid (PAA), and can further be polyvinylidene fluoride (PVDF).

[0149] In some embodiments, the positive electrode conductive agent includes one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers, and may further be conductive carbon black (Super-P, SP).

[0150] In some embodiments, the preparation method of the positive electrode sheet includes the following steps: dispersing the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in a solvent (such as NMP) to prepare a positive electrode slurry; covering the positive electrode slurry on at least one surface of the functional composite current collector, and obtaining the positive electrode sheet through drying, rolling and cutting.

[0151] In some embodiments, the negative electrode sheet includes the functional composite current collector as described above and a negative electrode active layer covering at least one surface of the functional composite current collector.

[0152] In some embodiments, the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, wherein the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (80-95):(2.5-10):(2.5-10), and can further be 80:10:10.

[0153] In some embodiments, the negative electrode active material includes a metal, a metal fluoride, a metal carbide, and modified compounds of each material. The metal includes one or more of Ca, Sn, La, Bi, Mg, Al, and Pb; the metal fluoride includes one or more of SnF2 and PbF2; and the metal carbide includes Y2C. The modified compounds of each material can be one or more of mixed modification, doping modification, and surface coating modification.

[0154] In some embodiments, the negative electrode binder includes 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), sodium carboxymethyl cellulose (CMC), and carboxymethyl chitosan (CMCS).

[0155] In some embodiments, the negative electrode conductive agent includes one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers, and may further be carbon nanofibers (CNFs).

[0156] In some embodiments, the preparation method of the negative electrode plate includes the following steps: using a dry mixing method to mix the negative electrode active material, the negative electrode conductive agent and the negative electrode binder to form a negative electrode powder; hot pressing the negative electrode powder on at least one surface of the functional composite current collector, and obtaining the negative electrode plate after drying, rolling and cutting.

[0157] It is understood that the electrolyte in the fluoride ion battery can be liquid, gel or all-solid.

[0158] In some embodiments, the electrolyte is an electrolyte solution comprising a fluoride ion salt and an organic solvent. The fluoride ion salt comprises one or more of CsF, KF, NaF, and KSnF3; and the organic solvent comprises one or more of benzyl alcohol (BA), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and ethylene glycol (EG).

[0159] In some embodiments, as Figure 4 As shown, the isolation film includes a base film 21 and a second safety coating 22 applied to at least one surface of the base film 21. The base film 21 can be a porous film with good chemical and mechanical stability. Furthermore, the base film 21 can be a single-layer film or a multi-layer composite film. When the base film 21 is a multi-layer composite film, the materials of the layers can be the same or different, without particular limitation.

[0160] In some embodiments, the material of the base film 21 includes one or more of glass fiber (GF), non-woven fabric, polyethylene (PE), polypropylene (PP) and polyimide (PI).

[0161] In some embodiments, the second safety coating 22 in the isolation film includes a second binder and a phase change material in a mass ratio of (2-5): (95-98), and the melting point of the phase change material is 85°C-120°C.

[0162] In some other embodiments, the second safety coating 22 includes a second binder and microcapsules in a mass ratio of (2~10):(90~98), the microcapsules include a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material is 1:(1.2~40), and the melting point of the phase change material is 85℃~120℃.

[0163] It can be understood that the types of the second binder, phase change material and flame retardant in the second safety coating 22 and their related parameters are substantially the same as those of the first safety coating 14 and are not described in detail here.

[0164] Adding flame retardants to the electrolyte can improve battery safety, but it can also alter the electrolyte's viscosity, degrading its ionic conductivity. Some flame retardants also have poor compatibility with electrode active materials, affecting the battery's electrochemical performance. Encapsulating the flame retardant within a phase-change material and forming the resulting microcapsules into a second safety coating 22 is then applied to the surface of the base film 21. This not only improves the mechanical properties of the separator and ensures the stability of the battery's electrochemical performance, but also releases the flame retardant from the microcapsules when the battery's internal temperature rises abnormally, improving battery safety and avoiding the adverse effects of adding the flame retardant directly to the electrolyte.

[0165] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a lamination process, and then injected with an electrolyte to form a battery.

[0166] In some embodiments, the fluoride ion battery may include an outer packaging for encapsulating the electrode assembly and electrolyte. The outer packaging of the fluoride ion battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery may also be a soft shell, such as a pouch-type soft shell, and the soft shell may be made of aluminum-plastic film.

[0167] It can be understood that the present application has no particular limitation on the shape of the fluoride ion battery, which can be cylindrical, square or any other shape.

[0168] In a fourth aspect, the present application provides an electrical device comprising the above-mentioned fluoride ion battery.

[0169] It is understood that fluoride ion batteries can serve as power sources or energy storage units for electrical devices. These devices may include, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, and energy storage systems. Examples of mobile devices include, but are not limited to, mobile phones and laptops; and examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0170] The following is further described in conjunction with specific examples and comparative examples. Unless otherwise specified, the raw materials involved in the following specific examples and comparative examples can be sourced from commercial sources. The instruments used can be sourced from commercial sources unless otherwise specified. The processes involved can be selected conventionally by those skilled in the art unless otherwise specified.

[0171] Example 1

[0172] The preparation method of the fluoride ion battery provided in this embodiment is as follows:

[0173] (1) Preparation of toughening agent:

[0174] 0.5% mass fraction of bacterial cellulose (diameter 100 nm, length 500 nm, aspect ratio 5) was dispersed in Tris-HCl buffer solution (pH = 8.5, 10 mM), and 0.5% mass fraction of dopamine was added under ultrasonic conditions. The mixture was stirred continuously for 24 hours at pH = 8.5, temperature 26°C, and rotation speed 800 rpm, and washed with deionized water multiple times to remove unreacted dopamine and unstable polydopamine on the surface to obtain an intermediate.

[0175] The intermediate was dispersed in 200 mL of a polyethyleneimine aqueous solution (mass fraction 0.5%, mass ratio of bacterial cellulose to polyethyleneimine 1:1), stirred continuously for 12 h at a temperature of 50°C and a rotation speed of 800 rpm, and washed multiple times with deionized water to remove unreacted polyethyleneimine to obtain a toughening agent.

[0176] (2) Preparation of positive electrode sheet:

[0177] Polyethylene terephthalate (PET) and toughening agent were mixed in a mass ratio of 100:2, melt blended at 300°C for 4 hours, and then hot-calendered after being evenly mixed. The polymer resin formed a polymer base film, and the toughening agent was dispersed in the polymer base film to form a 6μm thick support layer.

[0178] The support layer was transferred to the magnetron sputtering reaction chamber and vacuumed to 6×10 -5 Pa, argon gas is introduced at a flow rate of 40 sccm, and plasma etching treatment is performed under the conditions of a working gas pressure of 0.2 Pa and a working power of 40 W to improve the surface roughness of the supporting layer; then argon gas is introduced at a flow rate of 80 sccm, and DC magnetron sputtering coating is performed under the conditions of a sputtering gas pressure of 2 Pa and a sputtering power of 150 W to form a 1 μm thick Al layer as a conductive layer.

[0179] The MAX precursor Ti3AlC2 was etched using an etching solution containing LiF and HCl to produce the MXene material Ti3C2T x ; The conductive agent (Ti3C2T x ), a dispersant (PVP), a first binder (CMC and SBR in a mass ratio of 1:1) and deionized water in a mass ratio of 18:2:8:72 to prepare a primer slurry, which was then applied to the surface of the conductive layer and vacuum dried at 60°C for 72h to form a 1µm thick primer layer, thereby obtaining a functional composite current collector A.

[0180] CuF2 and Ketjen black were mixed in a mass ratio of 8:2, and high-energy ball milling was performed at 600 rpm for 5 hours to obtain the positive electrode active material; the positive electrode active material, conductive agent SP, and binder PVDF were dispersed in the solvent NMP in a mass ratio of 80:10:10, and the positive electrode slurry was obtained after homogenization; the positive electrode slurry was coated on the bottom coating of the functional composite current collector A, and after drying, rolling and cutting, the positive electrode sheet was obtained.

[0181] (3) Preparation of negative electrode sheet:

[0182] Polypropylene (PP) and toughening agent were mixed in a mass ratio of 100:2, melt blended at 180°C for 4 hours, and then hot-calendered after being evenly mixed. The polymer resin formed a polymer base film, and the toughening agent was dispersed in the polymer base film to form a 6μm thick support layer.

[0183] The support layer was transferred to the magnetron sputtering reaction chamber and vacuumed to 6×10 -5 Pa, argon gas is introduced at a flow rate of 40 sccm, and plasma etching treatment is performed under the conditions of a working gas pressure of 0.2 Pa and a working power of 40 W to improve the surface roughness of the support layer; then argon gas is introduced at a flow rate of 60 sccm, and DC magnetron sputtering coating is performed under the conditions of a sputtering gas pressure of 1.5 Pa and a sputtering power of 180 W to form a 1 μm thick Cu layer as a conductive layer.

[0184] The MAX precursor Ti3AlC2 was etched using an etching solution containing LiF and HCl to produce the MXene material Ti3C2T x ; The conductive agent (Ti3C2T x ), dispersant (PVP), first binder (PVDF) and NMP in a mass ratio of 18:2:10:70 to prepare a primer slurry, which was then coated on the surface of the conductive layer and vacuum dried at 60°C for 72h to form a 1µm thick primer layer, thereby obtaining a functional composite current collector B.

[0185] Pb and β-PbF2 were mixed evenly in a mass ratio of 65:15 to obtain a negative electrode active material; the negative electrode active material and the conductive agent CNF were mixed in a mass ratio of 80:10:10 until the color was uniform, and then the binder PTFE was added, and the mixture was dry-mixed at 80°C for 2h to obtain a negative electrode powder; the negative electrode powder was hot-pressed onto the bottom coating of the functional composite current collector B, and after drying, rolling and cutting, a negative electrode sheet was obtained.

[0186] (4) Preparation of isolation film:

[0187] Phase change material No. 95 paraffin was heated to melt at 100°C in a mass ratio of 2.2:1, and then the flame retardant 3-thiopheneboric acid (TB) with a particle size of 200nm was impregnated into the molten phase change material, so that the phase change material was coated on the surface of the flame retardant. The phase change material was cooled, solidified, and crushed to obtain microcapsules; the microcapsules and the second binder PVDF were added to DMF in a mass ratio of 95:5 to obtain a second safety slurry; the second safety slurry was coated on both surfaces of a 12µm thick PI base film by extrusion coating, and dried in a vacuum oven at 60°C for 24 hours to form a 1µm thick second safety coating, thereby obtaining a 14µm thick isolation film.

[0188] (5) Assembling fluoride ion batteries:

[0189] In a glove box (Ar atmosphere, water and O2 content <0.1ppm), the positive electrode, separator, and negative electrode were encapsulated with aluminum-plastic film and then injected with an electrolyte to produce a fluoride ion battery. The electrolyte consisted of 0.5 mol / L CsF and an organic solvent (BA and DMAc in a 1:1 volume ratio).

[0190] Examples 2 to 10

[0191] Please refer to Table 1. Examples 2 to 10 are basically the same as Example 1, with the following differences:

[0192] Example 2: The mass ratio of the polymer base film to the toughening agent is 100:5.

[0193] Example 3: The mass ratio of the polymer base film to the toughening agent is 100:10.

[0194] Example 4: The conductive agent of the base coating layer is carboxylated carbon nanotubes, and the carboxyl content is 6.52%.

[0195] Example 5: The conductive agent of the base coating is polyhydroxyfullerene, and the hydroxyl content is 39.1%;

[0196] Example 6: In the primer slurry, the mass fraction of the conductive agent is 12%;

[0197] Example 7: In the primer slurry, the mass fraction of the conductive agent is 6%;

[0198] Example 8: A first safety coating is also provided between the supporting layer and the conductive layer. The preparation method of the first safety coating is as follows: the phase change material chlorinated paraffin and the second binder PVDF are evenly mixed in a mass ratio of 95:5 and added to DMF to obtain a first safety slurry; the first safety slurry is coated on the surface of the supporting layer by extrusion coating, and dried in a vacuum oven at 60°C for 24 hours to form a first safety coating with a thickness of 1µm, and then a conductive layer and a primer are formed on the surface of the first safety coating in sequence according to Example 1.

[0199] Example 9: In the second safety coating layer of the isolation film, the flame retardant is pentafluoroethoxycyclotriphosphazene (FPN).

[0200] Example 10: The isolation film is not provided with a second safety coating.

[0201] Comparative Examples 1-4

[0202] Please refer to Table 1. Comparative Examples 1 to 4 are basically the same as Example 1, except that the differences are as follows:

[0203] Comparative Example 1: No toughening agent was added to the support layer; and no primer layer was provided on the surface of the conductive layer.

[0204] Comparative Example 2: No toughening agent was added to the support layer.

[0205] Comparative Example 3: No primer layer is provided on the surface of the conductive layer.

[0206] Comparative Example 4: The conductive agent of the undercoat layer is conductive carbon black SP.

[0207] The differences between Examples 2 to 8 and Comparative Examples 1 to 4 are shown in Table 1 below:

[0208] Table 1. Related parameters of functional composite current collector and separator

[0209]

[0210] Test Case

[0211] The following tests were carried out on each embodiment and each comparative example:

[0212] (1) Surface roughness of the base coating: The base coating was scanned using the non-contact mode of an atomic force microscope (AFM) to test the surface roughness.

[0213] (2) Tensile strength of functional composite current collector: Cut three sample strips with a length and width of 150 mm × 15 mm, ensure that the samples are placed vertically on the test clamp of the tensile testing machine, set the test parameters and start the test, and record the tensile strength.

[0214] (3) Peel strength of the positive electrode: Attach the tape flatly to the steel plate, fix the sample on the tape, attach the auxiliary tape to the surface of the sample, fix the steel plate and the auxiliary tape on the constant speed tensile machine to start the test, and record the peel strength of each sample.

[0215] (4) Lithium-to-Drag Ratio of the Battery: After the battery is fully charged, its internal resistance values ​​R1 and R2 at 25°C and 120°C are tested respectively, and the Lithium-to-Drag Ratio of the battery is calculated based on R2 / R1.

[0216] (5) Room temperature cycle test: The battery was subjected to a room temperature cycle test at 0.1C / 0.1C, and the first discharge specific capacity of the battery at 0.1C and the number of cycles at which the capacity decayed to 80% were recorded.

[0217] The above test results are shown in Table 2.

[0218] Table 2. Test results of functional composite current collector and fluoride ion battery

[0219]

[0220] As shown in Table 2, in Examples 1-10, the surface roughness of the primer layer ranged from 0.3 μm to 0.7 μm. This high surface roughness enhances the adhesion between the functional composite current collector and the active layer, thereby improving the peel strength of the electrode. For the positive electrode, the tensile strength of functional composite current collector A reached 183 MPa to 194 MPa, and the peel strength reached 3.8 N / 25 mm to 4.4 N / 25 mm. For the negative electrode, the tensile strength of functional composite current collector B reached 207 MPa to 215 MPa, and the peel strength reached 4.8 N / 25 mm to 5.6 N / 25 mm, showing the advantages of high tensile strength and high peel strength.

[0221] After being assembled into batteries, the number of cycles for the batteries of Examples 1 to 10 to reach 80% capacity decay at 0.1C ranged from 35 to 59, significantly higher than the number of cycles for the batteries of Comparative Examples 1 to 4. This indicates that the batteries of Examples 1 to 10 have the advantage of good cycling performance after adopting the functional composite current collector provided by this application. At the same time, the separators of Examples 1 to 9 are provided with a second safety coating. The resulting batteries have a lift-to-drag ratio of 9.8 to 286.9 when heated from 25°C to 120°C, demonstrating that the internal resistance of the battery cells at high temperatures (above the phase transition temperature) is significantly increased, which can suppress abnormal loop currents and effectively reduce the probability of thermal runaway of the battery at high temperatures. Furthermore, in the battery of Example 8, not only is the separator provided with a second safety coating, but the functional composite current collector is also provided with a first safety coating. This significantly improves the lift-to-drag ratio, resulting in particularly significant safety performance.

[0222] Compared to Example 1, Examples 2 and 3 increased the amount of toughening agent in the support layer, but the toughening effect did not improve. This may be because the increased amount of toughening agent worsens its dispersion and the nanofibers tend to agglomerate, resulting in a weakened toughening effect. This reduces the tensile strength of the functional composite current collector and the peel strength of the electrode, thereby reducing the battery's cycling performance.

[0223] The primer layer of Example 4 uses carboxylated carbon nanotubes (carboxyl content of 6.52%) as a conductive agent, and the primer layer of Example 5 uses polyhydroxyfullerene (hydroxyl content of 39.1%) as a conductive agent. The roughness of the primer layer, the tensile strength of the functional composite current collector, and the peel strength of the electrode do not change significantly, the lift-to-drag ratio of the battery is slightly reduced, and the cycle performance is significantly improved; Examples 6-7 reduce the amount of MXene material in the primer layer, so that the surface roughness of the primer layer and the peel strength of the electrode are reduced, but the safety performance of the battery is increased and the cycle performance is reduced.

[0224] In Example 8, a first safety coating is set between the support layer and the conductive layer, which significantly enhances the safety performance of the battery and improves the cycle performance; in the second safety coating of the isolation membrane of Example 9, the flame retardant in the microcapsules is different from that in Example 1, and the safety performance and cycle performance of the battery are slightly reduced; the isolation membrane of Example 10 is not provided with a second safety coating, the safety performance of the battery is poor, and the cycle performance is slightly reduced.

[0225] In comparative example 1, no toughening agent is added to the support layer, and no primer is set on the surface of the conductive layer. The tensile strength of the functional composite current collector and the peel strength of the pole piece are significantly deteriorated, and the cycle performance of the battery is greatly reduced. In comparative example 2, no toughening agent is added to the support layer, the tensile strength of the functional composite current collector is significantly deteriorated, and the cycle performance of the battery is reduced. In comparative example 3, no primer is set on the surface of the conductive layer, and the peel strength of the pole piece is significantly deteriorated, and the cycle performance of the battery is greatly reduced. The conductive agent of the primer in comparative example 4 is conductive carbon black SP, the surface roughness of the primer and the peel strength of the pole piece are reduced, and the cycle performance of the battery is also greatly reduced.

[0226] In summary, the functional composite current collector provided by the present application adds a conductive agent with a negative charge on the surface to the bottom coating, and has high surface roughness and good bonding properties. It can reduce the probability of fluoride ions migrating to the interface of the functional composite current collector and the active material layer and reacting by electrostatic repulsion, thereby improving the adhesion between the active material layer and the functional composite current collector and improving the cycle performance of the fluoride ion battery. At the same time, adding a toughening agent to the supporting layer of the functional composite current collector can enhance the mechanical strength of the functional composite current collector, thereby improving the cycle performance of the battery. In addition, providing a first safety coating in the functional composite current collector, and / or providing a second safety coating in the isolation membrane can increase the resistance of the battery at high temperatures, reduce the probability of thermal runaway of the battery, and thus greatly improve the safety performance of the battery.

[0227] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0228] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A functional composite current collector, characterized in that: The invention comprises a support layer, a conductive layer provided on at least one surface of the support layer, and a primer layer provided on a surface of the conductive layer away from the support layer; The support layer includes a polymer base film and a toughening agent dispersed in the polymer base film, wherein the toughening agent includes bacterial cellulose, a polydopamine layer coated on the bacterial cellulose, and an amino-modified layer grafted on the polydopamine layer; The primer layer includes a first binder and a conductive agent dispersed in the first binder. The functional groups on the surface of the conductive agent carry negative charges in the solution. The functional groups include one or more of hydroxyl groups, carboxyl groups, halogen groups, and oxygen-metal bonds.

2. The functional composite current collector according to claim 1, wherein The conductive agent includes one or more of carboxylated carbon nanotubes, polyhydroxy fullerenes and MXene materials; the MXene material includes Ti3C2T x 、Ti2CT x 、Ti3CNT x 、Ta4C3T x 、V2CT x 、V3C2T x 、Mo2CT x and Mo2TiC2T x One or more of, wherein T includes one or more of -OH, -F and -O, and x>0.

3. The functional composite current collector according to claim 2, wherein The primer layer satisfies at least one of the following conditions: (1) The first binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, hydrogenated nitrile rubber, polyvinyl alcohol, polymethacrylic acid, polymethyl methacrylate, polyacrylic acid, sodium polyacrylate, polyacrylamide, sodium alginate, sodium carboxymethyl cellulose and carboxymethyl chitosan; (2) The mass ratio of the first binder to the conductive agent is 1:(0.1-4); (3) The base coating further includes a dispersant, wherein the dispersant includes one or more of polyvinyl pyrrolidone, sodium polyacrylate, sodium lignin sulfonate, and sodium polystyrene sulfonate, and the mass ratio of the first binder to the dispersant is 1:(0.1-1); (4) The thickness of the primer layer is 0.5 μm to 3 μm; (5) The surface roughness of the primer layer is 100 nm to 800 nm; (6) The peel strength of the primer layer is 14N / 25mm~30N / 25mm.

4. The functional composite current collector according to claim 1, wherein The preparation method of the toughening agent comprises the following steps: mixing bacterial cellulose, dopamine, and a buffer solution, and allowing the dopamine to self-polymerize to form a polydopamine layer covering the bacterial cellulose, thereby obtaining an intermediate; The intermediate is dispersed in a mixed solution containing an aminating agent, and the aminating agent is grafted onto the polydopamine layer to form the amino-modified layer, thereby obtaining the toughening agent.

5. The functional composite current collector according to claim 4, wherein At least one of the following conditions is met: (1) The mass ratio of the bacterial cellulose, the dopamine and the amination reagent is 1: (0.5-2): (0.5-5); (2) The bacterial cellulose has a diameter of 10 nm to 200 nm, a length of 100 nm to 2000 nm, and an aspect ratio of 0.5 to 200; (3) The amination reagent includes one or more of ethylenediamine, histamine, polyethyleneimine and hexadecyltrimethylammonium bromide; (4) The mass ratio of the polymer base film to the toughening agent is 100:(1-10); (5) The thickness of the support layer is 4 μm to 8 μm.

6. The functional composite current collector according to any one of claims 1 to 3, wherein: The functional composite current collector further includes a first safety coating layer, which is disposed between the support layer and the conductive layer; The first safety coating comprises a second binder and a phase change material in a mass ratio of (2-5): (95-98), wherein the melting point of the phase change material is 85°C-120°C; or The first safety coating includes a second binder and microcapsules in a mass ratio of (2~10):(90~98), the microcapsules include a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material is 1:(1.2~40), and the melting point of the phase change material is 85°C~120°C.

7. A method for preparing a functional composite current collector according to any one of claims 1 to 6, characterized in that: The following steps are involved: Melting and blending a polymer resin and a toughening agent, and subjecting the resulting mixture to a film-forming process, wherein the polymer resin forms a polymer base film, and the toughening agent is dispersed in the polymer base film to obtain a support layer; forming a conductive layer on at least one surface of the support layer; A primer slurry containing a first binder and a conductive agent is applied on the conductive layer and dried to form a primer layer.

8. A fluoride ion battery, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet and / or the negative electrode sheet comprises the functional composite current collector according to any one of claims 1 to 6, or comprises a functional composite current collector prepared by the preparation method of the functional composite current collector according to claim 7.

9. The fluoride ion battery according to claim 8, wherein The isolation film includes a base film and a second safety coating layer coated on at least one surface of the base film; The second safety coating comprises a second binder and a phase change material in a mass ratio of (2-5): (95-98), wherein the melting point of the phase change material is 85°C-120°C; or The second safety coating includes a second binder and microcapsules in a mass ratio of (2~10):(90~98), the microcapsules include a flame retardant and a phase change material coated on the flame retardant, the mass ratio of the flame retardant to the phase change material is 1:(1.2~40), and the melting point of the phase change material is 85℃~120℃.

Images