CN118510944A

CN118510944A - Composite foil and preparation method and application thereof

Info

Publication number: CN118510944A
Application number: CN202280088142.0A
Authority: CN
Inventors: 王慢慢; 葛销明; 欧阳楚英
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-08-08
Filing date: 2022-08-08
Publication date: 2024-08-16
Also published as: WO2024031243A1

Abstract

A composite foil and its preparation method and application are provided. The composite foil comprises a metal simple substance layer and metal alloy layers attached to two opposite surfaces of the metal simple substance layer; the metal alloy layer is made of Cu-X alloy, wherein X is at least one metal element with activity greater than Cu. The porous composite foil prepared by taking the composite foil as a precursor material and combining corresponding dealloying technology can solve the problem that the existing two-dimensional foil cannot cope with infinite volume expansion of a lithium metal battery, and meanwhile, the phenomenon of lithium dendrite growth of the lithium metal battery can be effectively inhibited due to the existence of a porous structure.

Description

Composite foil and preparation method and application thereof

Technical Field

The application relates to the field of battery materials, in particular to a composite foil and a preparation method and application thereof.

Background

The current collector is one of indispensable component parts in the lithium ion battery, not only can bear active substances, but also can collect and output current generated by electrode active substances, is beneficial to reducing the internal resistance of the lithium ion battery and improves the coulomb efficiency, the circulation stability and the multiplying power performance of the battery.

The current materials which can be used as the current collector of the lithium ion battery are metal conductor materials such as copper, aluminum, nickel, stainless steel and the like, and the product form is single metal foil such as copper foil, aluminum foil, nickel foil and the like or metal composite foil formed by compounding a plurality of layers of different metal foils. Because the advantages and disadvantages of different metals are different, the metal composite foil can be improved and shortened, and particularly can be compatible with electric conductivity and thermal conductivity, however, the compact surface of the metal composite foil cannot adapt to the expansion problem of the lithium ion battery in the use process, so that the service life of the battery is limited.

For this purpose, the present invention is proposed.

Disclosure of Invention

The invention mainly aims to provide a composite foil, a preparation method and application thereof, wherein the porous composite foil prepared by taking the composite foil as a precursor material and combining corresponding dealloying technology can solve the problem that the existing two-dimensional foil cannot cope with infinite volume expansion of a lithium metal battery, and meanwhile, the phenomenon of lithium dendrite growth of the lithium metal battery can be effectively inhibited due to the existence of a porous structure.

In order to achieve the above object, the present invention provides the following technical solutions.

The first aspect of the invention provides a composite foil comprising a metal simple substance layer and metal alloy layers attached to two opposite surfaces of the metal simple substance layer;

the metal alloy layer is made of Cu-X alloy, wherein X is at least one metal element with activity greater than Cu.

The composite foil can form a porous metal foil after dealloying treatment, and the porous metal foil is distributed on two surface layers only, and the center is a complete metal simple substance layer, so that the composite foil has higher strength and higher porosity, and can reserve space for expansion of a battery and inhibit growth of lithium dendrites when used as a battery current collector。

The mechanism of forming the porous structure after the composite foil is treated is as follows: x is more active than Cu and therefore is preferentially etched after dealloying, with consequent formation of pores, leaving only the Cu metal skeleton. The activity herein refers to reducibility or measured by standard hydrogen electrode potential, and generally the smaller the hydrogen standard electrode potential, the more easily it is etched away.

The material type of the metal simple substance layer in the center is considered to consider the application scene besides the strength. Taking lithium ion batteries and lithium metal batteries as examples, the problems of expansion and lithium dendrite are serious, and if the porous composite foil prepared from the composite foil is applied to the negative electrode, materials such as copper, nickel and the like are generally selected. However, the application scope of the composite foil of the present invention is not limited by the above description.

In some embodiments, the proportion of X in the Cu-X alloy is 56.3wt.% to 88.5wt.%, optionally 56.3wt.% to 77.5wt.%, more optionally 72wt.% to 77.5wt.%.

The content of X has a significant effect on porosity and strength. When the proportion of X is in the range of 56.3wt.% to 88.5wt.%, the dealloyed treatment has a higher porosity while allowing for a high strength, more optionally 56.3 to 77.5wt.%, for example 56.3wt.%, 59wt.%, 61wt.%, 64wt.%, 65wt.%, 67wt.%, 70wt.%, 72wt.%, 73wt.%, 74wt.%, 76wt.%, 77.5wt.%, etc., with 72 to 77.5at.% being more preferred.

In some embodiments, X is at least one of Mn, zn, fe, al, sn, ni, optionally at least one of Mn and Al, and more optionally Mn.

As described above, X is a sacrificial metal element, and therefore the type should be selected with preference for easily removable elements, mn, zn, fe, al, sn, ni having lower standard hydrogen electrode potentials, with Mn being preferred over Al, and Mn being more preferred, as shown in table 1 below.

TABLE 1 Standard hydrogen electrode potentials for different metals

Metal material	Price level	Standard hydrogen electrode potential, V
Cu	2+	+0.337
Mn	2+	-1.179
Zn	2+	-0.7628
Fe	3+	-0.037
Al	3+	-1.163
Sn	2+	-0.136
Ni	2+	-0.250

In addition, in practical application, the selection of X should also consider cost and other factors.

In some embodiments, the X is a metal element with a hydrogen standard electrode potential of-1.2 to-1.0V.

In some embodiments, the Cu-X alloy is a binary alloy or a ternary alloy.

The Cu-X alloy is a binary alloy or a ternary alloy, has simpler composition, can reduce the processing difficulty, can be completed in one step during dealloying treatment, and avoids the problems of complex treatment and the like caused by different properties of more alloys.

In some embodiments, the elemental metal layer is pure copper.

The collocation of copper and Cu-X alloy has remarkable advantages when applied to a lithium ion battery or a negative electrode of a lithium metal battery, and is especially applied to the lithium metal battery.

In some embodiments, the phase of the Cu-X alloy is in a state where αmn and (Cu, γmn) coexist, and the mass ratio of αmn phase in the total object phase is 0 to 85.71%, optionally 22 to 85.71%.

The manganese of the alpha Mn phase forms larger pores after corrosion, for example, 0.5-10 mu m macropores can be formed under heat treatment at 430-725 ℃; and the gamma Mn forms smaller pores after corrosion, for example, pores of 20-200 nm can be formed under heat treatment at 430-725 ℃. Macropores are beneficial for solving the problem of expansion, but if too much distribution is detrimental to strength. In combination, the αmn phase preferably has a mass ratio of 22% to 85.71% in the total phase, for example, 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 48%, 50%, 53%, 55%, 60%, 65%, 67%, 70%, 75%, 78%, 80%, 82%, 85%, or the like.

In addition, the ratio of αmn and (Cu, γmn) phases has a correlation with the heat treatment conditions of the alloy, and the ratio of both can be controlled by adjusting the heat treatment conditions.

In some embodiments, the alpha Mn has a crystal morphology of near equiaxed crystals, which form a uniform pore size distribution after etching.

In some embodiments, the thickness of the two metal alloy layers is independently 30-200 μm, and the thickness of the metal simple substance layer is optionally 4.5-12 μm.

The three layers adopt the thickness collocation, so that the strength, the conductivity and other performances can be considered.

A second aspect of the present invention provides a method of preparing a composite foil as described above, comprising:

And stacking the Cu-X alloy foil and the metal simple substance foil together according to the sequence of the Cu-X alloy foil/the metal simple substance foil/the Cu-X alloy foil, and carrying out integrated rolling.

The invention is not particularly limited in rolling, and cold rolling, hot rolling or a combination of both can be performed.

In some embodiments, the integrated rolling is followed by a split phase heat treatment: heat treatment is carried out for 10-600 min at 430-725 ℃, and optionally at 430-650 ℃.

The split-phase heat treatment at a temperature of 430-725 ℃ can form a specific phase in which the αmn and (Cu, γmn) phases coexist, which is advantageous in controlling pore size distribution and porosity after corrosion, and the temperature can be a relatively severe constant temperature or a constant temperature allowing fluctuation in a small range (e.g., ±2℃, ±3℃, ±5℃, etc.). Among them, the treatment at a temperature of 430 to 650℃is preferable, for example, the average temperature is kept at 430℃、440℃、450℃、460℃、470℃、480℃、490℃、500℃、510℃、520℃、530℃、540℃、550℃、560℃、570℃、580℃、590℃、600℃、610℃、620℃、630℃、640℃、650℃ or the like.

A third aspect of the invention provides the use of a composite foil as described above in a current collector of a battery. The application refers to that the composite foil is used as a precursor of a current collector, X is required to be removed by dealloying treatment and corrosion, a porous current collector material is formed, and then a negative electrode active material is coated on the surface of the porous current collector material.

In some embodiments, the method of dealloying is: the more reactive X element or components are selectively removed by chemical or electrochemical means by utilizing the difference in chemical activity between the Cu and X elements in the alloy.

By the method, after the relatively active X element (also called base component) is removed, the residual Cu (also called noble component) spontaneously forms the three-dimensional bicontinuous porous metal through atomic diffusion, aggregation and other modes.

In conclusion, compared with the prior art, the invention achieves the following technical effects:

The porous metal current collector can be formed by simply processing the composite foil, and has higher porosity, tensile strength and good toughness;

The phase-splitting heat treatment can be used to make the alloy have specific phase composition, so as to improve the pore size distribution after dealloying treatment.

The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present application more readily apparent.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the accompanying drawings. In the drawings:

FIG. 1. Metallographic pictures of as-cast alloy of example 2;

FIG. 2 is a metallographic photograph of the wrought alloy of example 2;

FIG. 3 is a cross-sectional scan of a composite foil of example 2;

FIG. 4. Example 2 is a metal foam scan of precursor preparation;

FIG. 5 XRD pattern of example 2 without split phase heat treatment;

FIG. 6 XRD pattern after phase separation heat treatment of example 2;

FIG. 7. Example 2 is an XRD pattern of a metal foam current collector prepared from a precursor;

fig. 8 is a schematic view of a secondary battery according to an embodiment of the present application;

Fig. 9 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 5;

fig. 10 is a schematic view of a battery module according to an embodiment of the present application;

FIG. 11 is a schematic view of a battery pack according to an embodiment of the present application;

fig. 12 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 8;

Fig. 13 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 top cap assembly.

Detailed Description

Embodiments of the technical scheme of the present application will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present application, and thus are merely examples, and are not intended to limit the scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.

In the description of embodiments of the present application, the technical terms "first," "second," and the like are used merely to distinguish between different objects and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, a particular order or a primary or secondary relationship. In the description of the embodiments of the present application, the meaning of "plurality" is two or more unless explicitly defined otherwise.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

In the description of the embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

In the description of the embodiments of the present application, the term "plurality" means two or more (including two), and similarly, "plural sets" means two or more (including two), and "plural sheets" means two or more (including two).

In the description of the embodiments of the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured" and the like should be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; or may be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the embodiments of the present application will be understood by those of ordinary skill in the art according to specific circumstances.

As described in the summary of the invention, the composite foil provided by the invention has a sandwich-like structure, and comprises a metal simple substance layer and metal alloy layers on two sides. The metal simple substance layer is used as a strength supporting layer; the metal alloy layer is used for forming a porous structure and has a specific chemical composition, namely Cu-X alloy, wherein X is at least one metal element with activity larger than Cu. The three layers can be prepared into corresponding foil materials in advance, laminated and rolled together, and then subjected to optional split-phase heat treatment to obtain the composite foil material. The main purpose of the heat treatment is to form a multiphase structure where αmn and (Cu, γmn) coexist.

Although the invention is not limited to the application of the composite foil, experiments have found that the above composite foil has significant advantages when used as a precursor of a current collector of a negative electrode of a lithium metal battery, and for this reason, only the application of the composite foil in the negative electrode current collector is listed below.

The secondary battery, the battery module, the battery pack, and the electric device to which the composite foil is applied are described below with appropriate reference to the drawings.

In one embodiment of the present application, a secondary battery is provided.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

[ Positive electrode sheet ]

The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material of the first aspect of the application.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, 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 a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (e.g., liCoO ₂), lithium nickel oxide (e.g., liNiO ₂), lithium manganese oxide (e.g., liMnO ₂、LiMn ₂O ₄), lithium nickel cobalt oxide, Lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3Co _1/3Mn _1/3O ₂ (which may also be abbreviated as NCM 333), liNi _0.5Co _0.2Mn _0.3O ₂ (which may also be abbreviated as NCM 523), lini0.5co0.25mn0.25o2 (which may also be abbreviated as NCM 211), liNi _0.6Co _0.2Mn _0.2O ₂ (which may also be abbreviated as NCM 622), At least one of LiNi _0.8Co _0.1Mn _0.1O ₂ (which may also be abbreviated as NCM 811), lithium nickel cobalt aluminum oxide (such as LiNi _0.85Co _0.15Al _0.05O ₂), modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO ₄ (which may also be referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄), a composite of lithium manganese phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, 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; and (3) coating the positive electrode slurry on a current collector formed by dealloying treatment of the composite foil, and drying, cold pressing and the like to obtain the positive electrode plate.

[ Negative electrode sheet ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector may have two surfaces opposite in its own thickness direction, and the anode film layer may be provided on either or both of the two surfaces opposite to the anode current collector. The current collector and the negative electrode film layer may be made of the materials listed below.

In some embodiments, the negative electrode current collector may be a porous current collector obtained after dealloying, that is, the composite foil provided by the invention is used as a precursor, and dealloying treatment is performed to directly serve as a negative electrode plate. Wherein, the dealloying treatment can be: by utilizing the chemical activity difference between different elements in the alloy, one or more components (sometimes called base components) which are relatively active are selectively removed through a chemical or electrochemical method, and the rest components (also called noble components) spontaneously form the three-dimensional bicontinuous porous metal through the modes of atomic diffusion, aggregation and the like.

In some embodiments, the chemical method may be: preparing a sufficient amount of hydrochloric acid aqueous solution with the concentration of 2mol/L, placing the composite foil in a glass beaker, placing the composite foil in hydrochloric acid for free chemical corrosion, and removing alloying when no obvious bubbles appear on the surface layer of the composite foil when the temperature of the corrosive solution is 35 ℃.

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from 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).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ Electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

[ Isolation Membrane ]

In some embodiments, a separator is further included in the secondary battery. The application is not particularly limited in the kind of the separator, and any known porous separator having good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 8 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 9, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 10 is a battery module 4 as an example. Referring to fig. 10, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 11 and 12 are battery packs 1 as an example. Referring to fig. 11 and 12, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 13 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1:

1) Preparing copper blocks with the purity of more than 99.9% and manganese blocks with the purity of more than 99%, smelting the copper blocks into Cu _43.7Mn _56.3 alloy ingots by a vacuum induction smelting furnace, and preparing a copper foil for later use;

2) Mechanically polishing the Cu _43.7Mn _56.3 alloy ingot obtained in the first step to remove surface oxide skin, forging, wherein the forging pressure is 20t, performing stress relief annealing after each forging, wherein the annealing temperature is 750 ℃, and then performing water cooling. The annealing time is 60min;

3) Carrying out heat treatment on the forged alloy, wherein the heat treatment temperature is 750 ℃, the time is 60 minutes, and then carrying out preliminary hot rolling;

4) Stacking the alloy foil after hot rolling and the red copper foil together according to a stacking mode of the alloy foil (namely a first layer)/the red copper foil (namely a second layer)/the alloy foil (namely a third layer), and then carrying out integrated rolling;

5) Thinning and rolling the integrated rolled foil, wherein the total thickness of a rolled sample is 408 mu m, the thicknesses of the first layer and the third layer are 200 mu m, and the thickness of the second layer is 8 mu m;

6) And carrying out split-phase heat treatment on the sample, wherein the heat treatment temperature is 650 ℃, and the heat treatment time is 360 minutes, so as to obtain a final product.

Examples 2 to 6:

The difference from example 1 is only that the alloy ingot in step 1) is chemically different, copper and manganese blocks are selected to be smelted to obtain Cu ₂₈Mn ₇₂、Cu _22.5Mn _77.5、Cu _11.5Mn _88.5、Cu ₄₅Mn ₅₅、Cu _9.3Mn _90.7 alloy ingots, and other raw materials and operation conditions are the same as in example 1.

The metallographic phase of the cast alloy obtained in the step 1) of the example 2 is shown in fig. 1, and the metallographic phase of the wrought alloy obtained in the step 2) is shown in fig. 2.

The scanned foam metal graph obtained by corroding the alloy foil obtained in the step 3) is shown in figure 4, and the corrosion method is free chemical corrosion: preparing a sufficient amount of hydrochloric acid aqueous solution with the concentration of 2mol/L, placing the composite foil in a glass beaker, placing the composite foil in hydrochloric acid for free chemical corrosion, and removing alloying when no obvious bubbles appear on the surface layer of the composite foil when the temperature of the corrosive solution is 35 ℃.

The XRD pattern obtained in step 5) without phase separation heat treatment is shown in figure 5.

The XRD pattern of the phase-separated heat-treated product obtained in the step 6) is shown in figure 6.

The cross-sectional scan pattern of the final product is shown in figure 3.

The XRD pattern of the foam metal current collector obtained by etching the final product is shown in figure 7, and the etching method is free chemical etching: preparing a sufficient amount of hydrochloric acid aqueous solution with the concentration of 2mol/L, placing the composite foil in a glass beaker, placing the composite foil in hydrochloric acid for free chemical corrosion, and removing alloying when no obvious bubbles appear on the surface layer of the composite foil when the temperature of the corrosive solution is 35 ℃.

Examples 7 to 9:

The difference from example 2 is only that the phase separation heat treatment temperature in step 6) is different, copper blocks and manganese blocks are selected to be smelted to obtain Cu ₂₈Mn ₇₂ alloy ingots, and other raw materials and operation conditions are the same as in example 2.

Examples 10 to 11:

The difference from example 2 is that the thickness of the first layer and the third layer were each 30 μm in example 10, 115 μm in example 11, and other materials and operation conditions were the same as in example 2.

Examples 12 to 13:

The difference from example 2 is that the thickness of the second layer is 4.5 μm, 12 μm, respectively, and other materials and operation conditions are the same as in example 2.

Example 14

Except that the red copper foil in step 4) was replaced with nickel foil, and other materials and conditions were the same as those in example 2.

Example 15

The difference from example 2 is that the phase separation heat treatment of step 6) was removed, and other raw materials and conditions were the same as those of example 2.

Example 16:

1) Preparing copper blocks with the purity of more than 99.9 percent and zinc blocks with the purity of more than 99.9 percent, and smelting the copper blocks into Cu ₂₅Zn ₇₅ alloy ingots for later use by adopting a vacuum induction smelting furnace;

2) Mechanically polishing the Cu ₂₅Zn ₇₅ alloy ingot obtained in the first step to remove surface oxide skin, forging, wherein the forging pressure is 20t, and stress relief annealing is required after each forging, and the annealing temperature is 350 ℃. The annealing time is 75min;

3) Carrying out heat treatment on the forged alloy, wherein the heat treatment temperature is 350 ℃ and the time is 75min, and then carrying out preliminary hot rolling;

6) And carrying out split-phase heat treatment on the sample, wherein the heat treatment temperature is 500 ℃, and the heat treatment time is 400min, so as to obtain a final product.

Examples 17 to 18:

The difference from example 7 is that the phase separation heat treatment time of example 17 was 10min and the phase separation heat treatment time of example 18 was 600min. The other conditions were the same as in example 7.

Comparative example 1:

1) Preparing copper blocks with the purity of more than 99.9% and manganese blocks with the purity of more than 99%, and smelting the copper blocks and the manganese blocks into Cu ₂₈Mn ₇₂ alloy ingots for later use by adopting a vacuum induction smelting furnace;

2) Mechanically polishing the Cu ₂₈Mn ₇₂ alloy ingot obtained in the first step to remove surface oxide skin, forging, wherein the forging pressure is 20t, and stress relief annealing is required after each forging, and the annealing temperature is 750 ℃. The annealing time is 60min;

4) Thinning and rolling the alloy foil, wherein the final thickness of a rolled sample is 200 mu m;

5) And carrying out split-phase heat treatment on the sample, wherein the heat treatment temperature is 650 ℃, and the heat treatment time is 360 minutes, so as to obtain a final product.

The main differences between the above examples and comparative examples are shown in table 2 below.

Table 2 differences between the examples

The mass fraction of αmn and (Cu, γmn), αmn phase grain size, tensile strength, and resistivity in the foils of all the above examples and comparative examples were examined, and the results are shown in tables 3 to 5, respectively.

Wherein, the mass fraction calculation of the alpha Mn and the (Cu, gamma Mn) utilizes the lever principle of a binary phase diagram:

1. The alloy has the composition of x, the compositions of two phases are x ₁ and x ₂ respectively, and x ₁<x<x ₂

2. Then

Grain size and morphology test method:

The sample is polished in advance, then the alloy surface layer is corroded by 4% nitric acid for about 10s, and then the crystal grain morphology and the measurement size are observed under a metallographic microscope (model VK-9710 laser confocal microscope).

Resistivity testing method: and firstly, testing by using a Fulu gram universal meter to obtain a material resistance value, and then obtaining the resistivity by using a resistivity calculation formula rho=R. The parameters in the above formula are defined as follows:

ρ: resistivity, unit Ω

R: resistance value, unit Ω

S: cross-sectional area, unit m ²

L: sample length, unit m

TABLE 3 mass fractions of αMn and (Cu, γMn) for the examples

	αMn/％	(Cu,γMn)/％	γ/％	ε/％
Example 1	22％	78％	0	0
Example 2	51％	49％	0	0
Example 3	58％	42％	0	0
Example 4	80％	20％	0	0
Example 5	14％	86％	0	0
Example 6	84％	16％	0	0
Example 7	61％	36％	0	0
Example 8	60％	64％	0	0
Example 9	0％	100％	0	0
Example 10	51％	49％	0	0
Example 11	51％	49％	0	0
Example 12	51％	49％	0	0
Example 13	51％	49％	0	0
Example 14	51％	49％	0	0

Example 15	0％	100％	0	0
Example 16	0	0	50％	50％
Example 17	1％	99％	0	0
Example 18	100％	0％	0	0
Comparative example 1	51％	49％	0	0

TABLE 4 grain size of the αMn phase of each example

Table 5 tensile strength and resistivity for various examples

The above results show that: the composite foil obtained by the invention has higher tensile strength, and the conditions of the phase separation heat treatment are closely related to the proportion between the alpha Mn/(Cu, gamma Mn) two phases, for example, if the treatment time is too short, mn is not precipitated from gamma Mn to form alpha Mn, so that the specific phase of the alloy can be controlled by controlling the heat treatment conditions. In addition, although the strength of the foils with different manganese contents is not greatly different, the porosity is significantly different, and the manganese content is positively correlated with the porosity, so that foils with high manganese content are generally used.

In addition, the performance of the porous material obtained by alloying the composite foil is tested, and compared with the prior product, and the result is shown in Table 6.

Wherein, the preparation of the composite foil of the invention: the preparation method of the precursor foil is the same as that of the embodiment 1, and the difference is that the alloy components and the thicknesses are different, the precursor alloy components in the composite foil are Mn _77.5Cu _22.5, the thickness is 57 mu m Mn _77.5Cu _22.5+6μm Cu+57μm Mn _77.5Cu _22.5, the porous foil is obtained by a free chemical corrosion method, the corrosion liquid is 2mol/l hydrochloric acid, and the corrosion temperature is room temperature.

Preparation of a single layer alloy foil:

1) Preparing copper blocks with the purity of more than 99.9% and manganese blocks with the purity of more than 99%, and smelting the copper blocks and the manganese blocks into Mn _77.5Cu _22.5 alloy ingots by a vacuum induction smelting furnace;

2) Mechanically polishing the Mn _77.5Cu _22.5 alloy ingot obtained in the first step to remove surface oxide skin, forging, wherein the forging pressure is 20t, and after each forging, stress relief annealing is required, the annealing temperature is 750 ℃, and then water cooling is performed. The annealing time is 60min;

3) Carrying out heat treatment on the forged alloy for 60min at 750 ℃, and then rolling to obtain a single-layer alloy foil with the thickness of 120 mu m, wherein the dealloying method is consistent with that of the composite foil;

PU sponge: and (5) purchasing.

Metal foil for pore formation (i.e., metal powder+pore former group in table 6): and purchasing, namely preparing a blank from urea and copper powder, and then removing the urea through post-treatment to obtain the porous copper.

Tensile strength test method: the equipment is an electronic universal tester, model CZ-8010, and the testing method comprises the following steps: the sample is cut into the size of 18mm and 100mm for standby, two ends of the sample are respectively clamped on two chucks of a universal testing machine during testing, the speed is set to be 5mm/min, and a tensile test is carried out.

The bending resistance test method comprises the following steps: test pieces harass and disturb were wound on a 6mm core, and the breakage of the test material was observed.

The test method for the through hole is as follows: and a scanning electron microscope is adopted to obtain the section of the sample, and eyes observe whether the holes are mutually communicated.

TABLE 6 Properties of porous materials

The results show that: the porous material treated by the composite foil has higher porosity, can have high tensile strength, and can be bent without powder falling, so that the porous material can be used for a current collector to remarkably improve the expansion of a battery and the problem of lithium dendrite.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application, and are intended to be included within the scope of the appended claims and description. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims

A composite foil comprising a metal element layer, and metal alloy layers on two opposite surfaces of the metal element layer;

the metal alloy layer is made of Cu-X alloy, wherein X is at least one metal element with activity greater than Cu.
The composite foil according to claim 1, wherein the proportion of X in the Cu-X alloy is 56.3wt.% to 88.5wt.%, optionally 56.3wt.% to 77.5wt.%.
The composite foil according to claim 1 or 2, wherein X is at least one of Mn, zn, fe, al, sn, ni, optionally at least one of Mn and Al.
A composite foil according to any one of claims 1 to 3, wherein X is a metal element having a hydrogen standard electrode potential of-1.2 to-1.0V.
The composite foil according to any one of claims 1 to 4, wherein the Cu-X alloy is a binary alloy or a ternary alloy.
The composite foil according to any one of claims 1 to 5, wherein the elemental metal layer is pure copper.
The composite foil according to any one of claims 1 to 6, wherein the phases of the Cu-X alloy are co-existing of αmn and (Cu, γmn), the mass ratio of αmn phase in the total mass phase being 0-85.71%, optionally 22-85.71%.
The composite foil according to any one of claims 1 to 7, wherein the crystalline morphology of αmn is near equiaxed.
The composite foil according to any one of claims 1 to 8, wherein the thickness of both metal alloy layers is independently 30-200 μm, and the thickness of the elemental metal layer is optionally 4.5-12 μm.
The preparation method of the composite foil is characterized by comprising the following steps:

And stacking the Cu-X alloy foil and the metal simple substance foil together according to the sequence of the Cu-X alloy foil/the metal simple substance foil/the Cu-X alloy foil, and carrying out integrated rolling.
The method of manufacturing a composite foil according to claim 10, wherein the integrated rolling is followed by a split-phase heat treatment, wherein the heat treatment temperature is 430-725 ℃, optionally 430-650 ℃; the heat treatment time is 10-600 min.
A current collector, characterized in that it is prepared from a composite foil according to any one of claims 1 to 9.
The current collector of claim 12, comprising: the current collector is prepared by dealloying the composite foil.
A secondary battery comprising the current collector according to claim 12 or 13.
A battery module comprising the secondary battery according to claim 14.
A battery pack comprising the secondary battery according to claim 14 or the battery module according to claim 15.
An electric device comprising at least one of the secondary battery according to claim 14, the battery module according to claim 15, or the battery pack according to claim 16.