Composite foil, battery pole piece and battery

Abstract

Provided are a composite foil, a battery pole piece and a battery, belonging to the technical field of batteries. The composite foil comprises a substrate layer and an electrically conductive layer; the electrically conductive layer is disposed on at least one side of the substrate layer; the retention rate of the electrically conductive layer on said at least one side of the composite foil is 40-99.8%. The constructed composite foil is thin and lightweight, improving the energy density of the battery; lithium dendrites grow inside a part where the electrically conductive layer is removed, which can prevent same from forming burrs that pierce the diaphragm and cause a battery to short circuit, thereby improving lithium battery safety performance; battery active materials are embedded in the part where the conductive layer is removed, which enhances the bonding force between the battery active materials and the conductive layer, prevents the active materials from separating from the conductive layer, and prolongs battery life; in addition, the attachment area between the active materials and the conductive layer is increased, and contact resistance between the two is reduced, thereby maximizing the collection and conduction of electrons generated by positive and negative active materials, and improving battery performance.

Description

Composite foil, battery pole piece and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on June 12, 2023, with application number 202310685844.3 and invention name “A composite foil, battery electrode and battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of battery technology, and specifically relates to a composite foil, a battery pole piece and a battery. Background Art

[0004] Lithium-ion batteries have been widely used in portable energy, energy storage power supplies and electric vehicles due to their advantages such as high energy density, environmental friendliness and long service life.

[0005] Currently, the safety and energy density of lithium batteries are receiving much attention. In terms of safety, the flammability of the electrolyte inside lithium batteries causes thermal runaway during use, which in turn causes electric vehicles to catch fire and spontaneously combust. In terms of energy density, including volume density and mass density, the energy density of the battery determines the endurance of electric vehicles. The battery current collector acts as a carrier for the positive and negative active materials, and is also responsible for collecting and conducting positive and negative electrons. Its function is to collect the current generated by the battery active materials to produce a larger output current. Therefore, the current collector has a significant impact on battery performance. Existing batteries generally use aluminum foil as the positive electrode current collector and copper foil as the negative electrode current collector to collect current. However, batteries using existing aluminum foil or copper foil will experience thermal runaway, leading to battery fires, posing a significant safety hazard. The battery's energy density is not high, which affects battery performance.

[0006] Therefore, using battery current collectors as a starting point to improve the energy density and safety of lithium-ion batteries is one of the current directions of technological research.

[0007] Summary of the Invention

[0008] To address the shortcomings of the existing technology, the present application provides a composite foil, a battery electrode, and a battery. By providing a conductive layer with a certain residual rate on at least one side of the substrate layer, the present application makes the constructed composite foil lighter, thereby increasing the energy density of the battery from the perspective of mass density, and also improving the safety performance of the lithium-ion battery.

[0009] This application adopts the following technical solutions to achieve the purpose of this application:

[0010] In a first aspect, the present application provides a composite foil comprising a substrate layer and a conductive layer; the conductive layer is provided on at least one side of the substrate layer; and the residual rate of the conductive layer on at least one side of the substrate layer is 40 to 99.8%.

[0011] The present application provides a conductive layer with a certain residual rate on at least one side of the substrate layer, so that the constructed composite foil is thinner and lighter, thereby improving the energy density of the battery in terms of mass density. The portion where the surface of the conductive layer is removed can form a space to accommodate the growth of metallic lithium dendrites, which allows the lithium dendrites to grow inside the space instead of growing on the surface of the conductive layer, and can prevent the lithium dendrites from growing on the surface of the conductive layer to form burrs and pierce the diaphragm, causing a short circuit in the battery, thereby improving the safety performance of the battery. In addition, the battery active material is embedded in the portion where the conductive layer is removed, which can enhance its bonding strength with the conductive layer, prevent the active material from separating from the conductive layer, and at the same time increase the contact area between the electrode active material and the conductive layer, reduce the resistance of the battery electrode, and improve the battery performance.

[0012] In the present application, the residual rate of the conductive layer on at least one side of the substrate layer is 40 to 99.8%, for example, it can be 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% or 99.8%.

[0013] In this application, a conductive layer residual rate within the range of 40% to 99.8% can achieve good technical effects. If the conductive layer residual rate is too low, too little of the conductive layer remains, increasing internal resistance and hindering the collection of current from the battery's active materials. The resulting current density is low, affecting the battery's current output power. If the conductive layer residual rate is too high, it is detrimental to the bonding of the electrode active materials with the conductive layer, and there is too little space for the growth of lithium dendrites, thereby affecting the battery's safety performance.

[0014] Optionally, the residual rate of the conductive layer is 50% to 85%, and further optionally 60% to 75%.

[0015] It should be noted that the residual rate of the conductive layer in this application is calculated as follows:

[0016] Optionally, the conductive layer includes a first conductive layer and a second conductive layer, and the first conductive layer and the second conductive layer are respectively arranged on both sides of the substrate layer.

[0017] Optionally, the residual rate of the first conductive layer is greater than the residual rate of the second conductive layer; or the residual rate of the first conductive layer is less than the residual rate of the second conductive layer; or the residual rate of the first conductive layer is equal to the residual rate of the second conductive layer.

[0018] Optionally, the total thickness of the conductive layer is 0.2-4 μm, for example, 0.2 μm, 0.4 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm.

[0019] In this application, if the total thickness of the conductive layer is too thin, on the one hand, it will cause poor conductivity of the current collector, which is not conducive to the collection and conduction of positive and negative electrode electrons, and cannot meet the requirements of fast charging of the battery; on the other hand, it will reduce the mechanical properties of the foil, resulting in easy breakage in the subsequent winding process of the battery, and easy deformation and breakage of the current collector during the battery cycle, thereby causing safety problems; if the total thickness of the conductive layer is too thick, it will increase the weight and volume of the current collector, thereby reducing the energy density of the battery.

[0020] Optionally, the conductive layer is made of metal.

[0021] Optionally, the metal includes any one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In or Zn, or an alloy of at least two of the metals.

[0022] Optionally, the conductive layer is a multilayer structure formed by stacking at least two conductive sublayers. For example, if the base material layer of the composite foil is only provided with a conductive layer on one side, the multilayer structure of the conductive layer is provided with a conductive first sublayer, a conductive second sublayer, a conductive third sublayer, and so on.

[0023] For example, a first conductive layer and a second conductive layer are respectively provided on both sides of the substrate layer of the composite foil. The multilayer structure of the first conductive layer includes a conductive first sublayer, a conductive second sublayer, a conductive third sublayer, and so on; the multilayer structure of the second conductive layer includes a conductive first sublayer, a conductive second sublayer, a conductive third sublayer, and so on.

[0024] Optionally, the materials of the at least two conductive sublayers are the same or different. For example, the material of the conductive first sublayer is Cu, and the material of the conductive second sublayer is also Cu; or, the material of the conductive first sublayer is Cu, and the material of the conductive second sublayer is Fe.

[0025] Optionally, the conductive layer has a porous structure, and the porous structure includes blind holes and / or through holes.

[0026] It should be noted that the removed portion of the conductive layer forms a porous structure.

[0027] Optionally, the substrate layer has a porous structure, and the porous structure includes blind holes and / or through holes.

[0028] The present application sets a porous structure in the substrate layer in order to: 1) enhance the bonding strength between the battery active material and the foil. When the electrode active material slurry is coated on the surface of the conductive layer of the composite foil, the active material slurry diffuses into the pore structure and forms an "I"-shaped structure that is interconnected and integrated with the entire foil, so that the adhesion strength between the electrode active material and the foil surface is increased and not easy to fall off, which effectively improves the battery cycle life and extends the battery service life; 2) expand the space for the growth of lithium dendrites and changes the growth direction of lithium dendrites. Lithium dendrites grow inward along the pore wall of the conductive layer. The pore space in the substrate layer accommodates the lithium dendrites that continue to grow, preventing them from growing toward the surface of the foil to form burrs and thus puncturing the positive and negative electrode diaphragms of the battery, resulting in a short-circuit effect of the battery and causing fire and smoke; 3) the pore structure of the substrate layer can absorb or alleviate the expansion and contraction stress generated by the insertion and removal of lithium ions during the charge and discharge process of the battery, maintain the integrity of the current collector, and prevent the battery from swelling.

[0029] Optionally, in the conductive layer, the apertures of the blind holes and through holes are independently 0.01 to 1000 μm, for example, 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 500 μm or 1000 μm.

[0030] Optionally, in the substrate layer, the pore diameters of the blind holes and through holes are independently 0.01 to 1000 μm, for example, 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 500 μm or 1000 μm.

[0031] It should be noted that the pore diameter described in this application is the value obtained by measuring the maximum width of the pore.

[0032] Optionally, in the conductive layer, the diameter of the blind hole gradually decreases, or gradually increases, or remains the same along the direction from the opening position to the position away from the hole.

[0033] Optionally, in the substrate layer, the diameter of the blind hole gradually decreases, or gradually increases, or remains the same along the direction from the opening position to the position away from the opening position.

[0034] In this application, the shape of the blind hole can enhance the bonding strength between the electrode active material and the foil. When the battery active material is coated on the composite foil provided in this application, the active material diffuses into the hole. When entering the battery drying process, the dried active material is embedded in the hole. At this time, after the active material solidifies, it forms a groove-engaging structure that fits with the blind hole. In particular, the hole structure, in which the aperture gradually increases from the position close to the opening to the position far from the opening, forms two opposing raised engaging portions at the opening, which firmly clamp the solidified active material embedded in the hole and prevent the active material from separating from the foil.

[0035] Optionally, in the conductive layer, the through hole includes a first through hole and a second through hole connected to the first through hole, the aperture of the first through hole gradually decreases from the opening position along the direction close to the second through hole, and the aperture of the second through hole gradually decreases along the direction close to the first through hole.

[0036] Optionally, in the substrate layer, the through hole includes a first through hole and a second through hole connected to the first through hole, the aperture of the first through hole gradually decreases from the opening position along the direction approaching the second through hole, and the aperture of the second through hole gradually decreases along the direction approaching the first through hole.

[0037] In the present application, the aperture of the first through hole gradually decreases in the direction approaching the second through hole, and the aperture of the second through hole gradually decreases in the direction approaching the first through hole. This arrangement makes the first through hole and the second through hole both have a conical structure, with the aperture being smallest at the position where the first through hole and the second through hole are connected, and a snap-fitting protrusion is formed at the intersection of the side wall of the first through hole and the side wall of the second through hole. After the electrode active material is coated, it will diffuse into the through holes of the conductive layer and the through holes of the substrate layer in sequence. Due to the presence of the snap-fitting protrusion, after the active material solidifies, a snap-fitting groove that cooperates with the snap-fitting protrusion is formed at the position corresponding to the snap-fitting protrusion. The snap-fitting protrusion and the snap-fitting groove are used to engage with each other, thereby enhancing the bonding strength between the electrode active material and the composite foil, thereby preventing the electrode active material from separating from the composite foil.

[0038] Optionally, in the conductive layer, the average hole density of blind holes and through holes is independently 10 to 30,000 holes / cm 2 , for example, it can be 10 / cm 2 , 50 pieces / cm 2 , 100 pieces / cm 2 , 250 pieces / cm 2 , 500 pieces / cm 2 , 750 pieces / cm 2 , 1000 pieces / cm 2 , 10,000 pieces / cm 2 or 30,000 pieces / cm 2 etc., preferably 100-900 pcs / cm 2 .

[0039] Optionally, in the substrate layer, the average hole density of the blind holes and through holes is independently 10 to 30,000 holes / cm 2 , for example, it can be 10 / cm 2 , 50 pieces / cm 2 , 100 pieces / cm 2 , 250 pieces / cm 2 , 500 pieces / cm2 , 750 pieces / cm 2 , 1000 pieces / cm 2 , 10,000 pieces / cm 2 or 30,000 pieces / cm 2 etc., preferably 100-900 pcs / cm 2 .

[0040] It should be noted that, within the scope defined in the present application, the pore diameter and pore density of the porous structures of the conductive layer and the substrate layer do not affect each other.

[0041] Optionally, the thickness of the substrate layer is 1 to 13 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm or 13 μm.

[0042] Optionally, the material of the substrate layer is selected from any one or a combination of at least two of the following materials: phenolic resins, alkyd resins, amino resins, polyester resins, polyurethane resins, acrylic resins, vinyl resins, fluororesins, cyanate esters, polystyrenes, vinyl acetates, polyamides (PA), rubbers, urethanes, melamines, BT resins, ABF resins, polypropylene (PP), polyphenylene sulfides (PPS), polyethylene terephthalate (PET) or polyimides (PI).

[0043] In this application, BT resin is a thermosetting resin formed by adding bismaleimide and triazine as the main resin components, and epoxy resin, polyphenylene ether resin or allyl compound as a modifying component; ABF resin, also known as "Ajinomoto stacking film", is a film made of synthetic resin materials with excellent insulation properties; PP refers to polypropylene; PPS refers to polyphenylene sulfide; PET refers to polyester copolymer; PI refers to polyimide.

[0044] Optionally, the composite foil further includes a transition layer, and the transition layer is located between the conductive layer and the substrate layer.

[0045] Optionally, the material of the transition layer is metal, and the metal includes any one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In or Zn, or an alloy of at least two metals.

[0046] Optionally, the thickness of the transition layer is 0.001-10 μm, for example, 0.001 μm, 0.01 μm, 0.1 μm, 1 μm, 3 μm, 5 μm, 7 μm or 10 μm.

[0047] The present application does not limit the method for forming the transition layer. For example, it can be formed by a vacuum sputtering process.

[0048] Optionally, the composite foil further includes an adjustment layer, and the adjustment layer is located between the conductive layer and the substrate layer.

[0049] Optionally, the thickness of the adjustment layer is 0.05-10 μm, for example, 0.05 μm, 0.1 μm, 1 μm, 3 μm, 5 μm, 7 μm or 10 μm.

[0050] Optionally, the composite foil further includes a transition layer and an adjustment layer, wherein the transition layer and the adjustment layer are located between the conductive layer and the substrate layer, the transition layer is located on a side close to the conductive layer, and the adjustment layer is located on a side close to the substrate layer.

[0051] The purpose of providing the transition layer and the adjustment layer in the present application is to improve the peeling strength between the conductive layer and the substrate layer, and to prevent the two from separating during actual application.

[0052] The present application does not limit the method for forming the adjustment layer. For example, it can be formed by a coating process.

[0053] Optionally, the number of the adjustment layer is at least one.

[0054] Optionally, the regulating layer is selected from any one or a combination of at least two of the following materials: resin, filler particles, treating agent, coupling agent or active agent.

[0055] When the adjustment layer described herein has a multi-layer structure of at least two layers, the material of each adjustment layer can be any one or a combination of at least two of the above materials, without limitation. For example, when the adjustment layer has a three-layer structure, the material of the first adjustment layer is resin, the material of the second adjustment layer is a mixture of resin and filler particles, and the material of the third adjustment layer is a mixture of a coupling agent and a treating agent.

[0056] Optionally, the resin includes any one or a combination of at least two of acrylamide resin, thermoplastic polyimide resins, modified epoxy resins, modified acrylic resins, modified polyurethane resins, modified phenolic resins, water-soluble phenolic resins or amino resins.

[0057] Optionally, the filler particles include at least one of conductor particles, semiconductor particles, insulator particles and coated composite particles.

[0058] Optionally, the filler particles further include large particles formed by agglomeration of small particles.

[0059] It should be noted that the coated composite particles refer to insulator particles coated with a conductor, or another type of insulator particles coated with an insulator.

[0060] In practical applications, the filler particles can be diamond powder, titanium dioxide, silicon powder, silicide powder, silicon dioxide powder, aluminide powder, graphene powder, iron powder, nickel powder, copper powder, nickel-plated diamond powder or metal-plated inorganic powder.

[0061] Optionally, the treating agent includes any one of acrylamide, acrylate, polyether or polyethylene oxide-propylene oxide, or a combination of at least two thereof.

[0062] Optionally, the coupling agent includes any one of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a bimetallic coupling agent, a lignin coupling agent or a tin coupling agent, or a combination of at least two thereof.

[0063] Optionally, the active agent comprises a surfactant.

[0064] In a second aspect, the present application provides a battery pole piece, which includes the composite foil material as described in the first aspect.

[0065] In a third aspect, the present application provides a battery, comprising the battery electrode as described in the second aspect.

[0066] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the numerical ranges not listed. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0067] Compared with the prior art, this application has the following beneficial effects:

[0068] (1) By providing a conductive layer with a residual rate of 40 to 99.8% on at least one side of the substrate layer, the present application removes part of the conductive layer, making the composite foil thinner and lighter than traditional current collectors. When the composite foil is made into battery pole pieces through a winding process, the resulting battery pole pieces are smaller in size and lighter in weight, providing more space for battery active materials, thereby improving the energy density of the battery.

[0069] (2) The composite foil provided in the present application changes the growth direction of lithium dendrites, causing lithium dendrites to grow inside the area where the conductive layer is removed, thereby delaying the growth of lithium dendrites on the surface of the conductive layer, thereby piercing the diaphragm and causing the battery to short-circuit, thereby improving the safety performance of the battery.

[0070] (3) The battery active material coated on the surface of the composite foil provided in the present application is embedded in the portion where the conductive layer is removed, thereby enhancing the bonding strength between the battery active material and the conductive layer, preventing the active material from separating from the conductive layer, and extending the battery life.

[0071] (4) The composite foil provided in this application increases the attachment area between the active material and the conductive layer, reduces the contact resistance between the two, maximizes the collection and conduction of electrons generated by the positive and negative active materials, outputs a larger current, and improves battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG1 is a schematic structural diagram of the composite foil provided in Example 6 of the present application.

[0073] FIG2 is a schematic diagram of the structure of the composite foil provided in Example 8 of the present application.

[0074] FIG3 is a schematic structural diagram of the composite foil provided in Example 9 of the present application.

[0075] FIG4 is a schematic diagram of the structure of the composite foil provided in Example 10 of the present application.

[0076] FIG5 is a schematic structural diagram of the composite foil provided in Example 11 of the present application.

[0077] FIG6 is a schematic structural diagram of the composite foil provided in Example 12 of the present application.

[0078] FIG7 is a schematic diagram of the structure of the composite foil provided in Example 14 of the present application.

[0079] Among them, 1 is substrate layer; 2 is conductive layer; 21 is first conductive layer; 22 is second conductive layer; 3 is transition layer; 4 is adjustment layer; 41 is first adjustment layer; 42 is second adjustment layer; 5 is blind hole; 6 is through hole; 61 is first through hole; 62 is second through hole. DETAILED DESCRIPTION

[0080] The technical solution of the present application is further described below through specific embodiments. Those skilled in the art should understand that the embodiments are merely helpful for understanding the present application and should not be considered as specific limitations of the present application. The embodiments of the present application use an etching process to treat the conductive layer, and the desired conductive layer residual rate is obtained by adjusting the etching solution treatment time. It should also be noted that the etching process is one of the methods cited in the present application.

[0081] The present application provides a specific embodiment, which provides a composite foil, comprising a substrate layer and a conductive layer; the conductive layer is provided on one side of the substrate layer; and the residual rate of the conductive layer on one side of the composite foil is 40 to 99.8%.

[0082] The conductive layer in the composite foil provided in this embodiment has a thickness of 0.2 to 4 μm and is made of metal.

[0083] The thickness of the base material layer in the composite foil provided in this embodiment is 1 to 13 μm, and the material is polyethylene terephthalate (PET).

[0084] The composite foil material of the present application is prepared by the following method:

[0085] S1: Using evaporation copper plating process to form a conductive layer on one side of PET;

[0086] S2: using an etching process to remove part of the conductive layer, so that the residual rate is 40 to 99.8%;

[0087] Etching solution: 1 mol / L HCl, 0.8 mol / L malonic acid, 0.2 mol / L NH4Cl, 0.5 mol / L FeCl3, 1 mol / L HgCl2;

[0088] The specific steps of the etching process include: spraying the foil (size 30 cm×30 cm) with etching liquid at a liquid temperature of 35° C.

[0089] Example 1

[0090] This embodiment provides a composite foil, which includes a substrate layer 1 and a conductive layer 2;

[0091] The conductive layer 2 is provided on one side of the substrate layer 1;

[0092] The residual rate of the conductive layer 2 is 99.8%;

[0093] The conductive layer 2 has a porous structure, and the porous structure includes blind holes 5 and through holes 6;

[0094] The blind holes and through holes of the conductive layer 2 have a pore size of 0.01 μm and an average pore density of 10 holes / cm 2 ;

[0095] The thickness of the conductive layer 2 is 4 μm and the material is Cu;

[0096] The thickness of the base material layer 1 is 1 μm, and the material is ABF resin.

[0097] The composite foil provided in this embodiment is prepared by the following method:

[0098] (1) forming a conductive layer 2 on one side of the substrate layer 1 by using an evaporation copper plating process;

[0099] (2) etching away a portion of the conductive layer 2 by an etching process, so that the residual rate is 99.8%;

[0100] The etching solution in the etching process includes: 1 mol / L HCl, 0.8 mol / L malonic acid, 0.2 mol / L NH4Cl, 0.5 mol / L FeCl3, and 1 mol / L HgCl2;

[0101] The specific steps of the etching process include: spraying the foil material (size 30 cm×30 cm) with the conductive layer 2 with etching liquid at 35° C.

[0102] Example 2

[0103] The difference between this embodiment and embodiment 1 is that:

[0104] The residual rate of the conductive layer 2 is 75%;

[0105] The diameter of the through holes and blind holes in the conductive layer 2 is 500 μm, and the average hole density is 15,000 / cm 2 ;

[0106] The base material is polyimide (PI).

[0107] The rest of the preparation methods and parameters remained the same as in Example 1.

[0108] Example 3

[0109] The difference between this embodiment and embodiment 1 is that:

[0110] The residual rate of the conductive layer 2 is 40%;

[0111] The diameter of the through holes and blind holes in the conductive layer 2 is 1000 μm, and the average hole density is 30,000 / cm 2 ;

[0112] The base material is polypropylene (PP).

[0113] The rest of the preparation methods and parameters remained the same as in Example 1.

[0114] The battery mass energy density and the peeling force between the active material and the foil of Examples 1-3 were measured. The results are shown in Table 1.

[0115] Table 1

[0116] The data from Examples 1-3 show that Example 1 has the highest conductive layer residue rate of 99.8%, resulting in the highest battery energy density, but the lowest peeling force between the active material and the foil. Example 3 has a residue rate of 40%, resulting in the lowest battery energy density, but the highest peeling force between the active material and the foil. Compared to Examples 1 and 3, Example 2 has a more moderate battery energy density and peeling force between the active material and the foil. Therefore, Example 2 was selected as the basis for further research.

[0117] Example 4

[0118] The difference between this embodiment and embodiment 2 is that:

[0119] The thickness of the conductive layer 2 is 2 μm;

[0120] The material of the base material layer 1 is polyethylene terephthalate (PET).

[0121] The rest of the preparation methods and parameters remained the same as in Example 2.

[0122] Example 5

[0123] The difference between this embodiment and embodiment 2 is that:

[0124] The thickness of the conductive layer 2 is 0.2 μm;

[0125] The material of the substrate layer 1 is polyamide (PA).

[0126] The rest of the preparation methods and parameters remained the same as in Example 2.

[0127] The mass energy density of the batteries of Examples 2, 4, and 5 was measured, and the test results are shown in Table 2.

[0128] Table 2

[0129] Examples 2, 4 and 5 compare the effect of the thickness of the conductive layer on the battery energy density. As can be seen from the above table, under the same residual rate conditions, the thickness of the conductive layer has a greater effect on the battery energy density.

[0130] When the thickness of the conductive layer is 0.2 μm (Example 5), the battery mass energy density is 152 wh / kg. This is because the conductive layer is relatively thin, which is not conducive to the collection and conduction of positive and negative electrode electrons and cannot meet the requirements of fast charging of the battery. At the same time, it will also reduce the mechanical properties of the foil, resulting in easy breakage in the subsequent winding process of the battery. During the battery cycle, the current collector is prone to deformation and breakage, which leads to safety problems.

[0131] When the conductive layer thickness is 4 μm (Example 2), the battery mass energy density is 163 wh / kg, which is lower than when the conductive layer thickness is 2 μm (Example 4). This is because as the conductive layer thickness increases, the weight and volume of the battery current collector also increase, and the battery active material decreases, thereby reducing the battery energy density.

[0132] After optimization, the present application believes that the thickness of the conductive layer is 2 μm as the optimal thickness. Therefore, Example 4 is selected as the basis for further research.

[0133] Example 6

[0134] The difference between this embodiment and embodiment 4 is that:

[0135] The thickness of the base material layer 1 is 6 μm.

[0136] The rest of the preparation methods and parameters remained the same as in Example 4.

[0137] FIG1 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0138] Example 7

[0139] The difference between this embodiment and embodiment 4 is that:

[0140] The thickness of the base material layer 1 is 13 μm.

[0141] The rest of the preparation methods and parameters remained the same as in Example 4.

[0142] The mass energy density of the batteries of Examples 4, 6, and 7 was measured, and the test results are shown in Table 3.

[0143] Table 3

[0144] Examples 4, 6 and 7 compare the effect of the thickness of the substrate layer on the battery mass energy density. It can be seen from the above table that under the same conditions, the thickness of the substrate layer has a greater effect on the battery energy density. When the thickness of the substrate layer is 13 μm (Example 7), the battery pole piece prepared by the composite foil of the present application through the battery winding process is larger in volume, occupies a larger space inside the battery, and leaves less space for the battery electrolyte, so the battery energy density of Example 7 is the smallest. Although the battery mass energy density of Example 4 is the largest, due to the thin thickness of the substrate layer, it is easy to break during the battery pole piece preparation process due to insufficient supporting force. After optimization, this application considers that the thickness of the substrate layer is 6 μm as the optimal thickness. Therefore, Example 6 is selected as the basis for further research.

[0145] Example 8

[0146] The difference between this embodiment and embodiment 6 is that:

[0147] This embodiment is provided with a transition layer 3, which is located between the conductive layer 2 and the substrate layer 2;

[0148] The material of the transition layer is an alloy of Cu and Ni;

[0149] The thickness of the transition layer is 0.01 μm.

[0150] The composite foil provided in this embodiment is prepared by the following method:

[0151] (1) forming a transition layer 3 on one side of the substrate layer 1 by a vacuum sputtering process;

[0152] (2) forming a conductive layer 2 on the transition layer 3 using an electrolytic copper foil production process;

[0153] (3) etching away part of the conductive layer 2 by an etching process, so that the residual rate is 75%;

[0154] The etching process is the same as that in Example 1.

[0155] The remaining preparation methods and parameters remained the same as in Example 6.

[0156] FIG2 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0157] Example 9

[0158] The difference between this embodiment and embodiment 6 is that:

[0159] This embodiment is provided with an adjustment layer 4, which is located between the conductive layer 2 and the substrate layer 2;

[0160] The adjustment layer 4 includes a first adjustment layer 41 and a second adjustment layer 42 . The first adjustment layer 41 is arranged on a side close to the substrate layer 1 , and the second adjustment layer 42 is arranged on a side close to the conductive layer 2 .

[0161] The thickness of the first adjustment layer is 0.2 μm, and the thickness of the second adjustment layer is 0.1 μm;

[0162] The material of the first adjustment layer is modified epoxy resin, and the material of the second adjustment layer is silane coupling agent (ie, γ-(2,3-epoxypropoxy)propyltrimethoxysilane).

[0163] The composite foil provided in this embodiment is prepared by the following method:

[0164] (1) forming a first adjustment layer 41 on one side of the substrate layer 1 by a coating process;

[0165] (2) forming a second adjustment layer 42 on the first adjustment layer 41 by a coating process;

[0166] (3) forming a conductive layer 2 on the second adjustment layer 42 using an electrolytic copper foil process;

[0167] (4) etching away a portion of the conductive layer 2 by an etching process, so that the residual rate is 75%;

[0168] The etching process is the same as that in Example 1.

[0169] The remaining preparation methods and parameters remained the same as in Example 6.

[0170] FIG3 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0171] The peeling force between the conductive layer and the substrate layer of the composite foil materials of Examples 6, 8, and 9 was measured. The test results are shown in Table 4.

[0172] Table 4

[0173] It can be seen from the data of Examples 6, 8 and 9 that adding a transition layer or an adjustment layer between the conductive layer and the substrate layer of the composite foil can improve the peeling force between the conductive layer and the substrate layer. The use of the transition layer and the adjustment layer together has a synergistic effect, preventing the separation between the two during actual application.

[0174] Example 10

[0175] The difference between this embodiment and embodiment 6 is that:

[0176] The substrate layer 1 has a porous structure, which includes blind holes 5 and through holes 6. The pore diameters of the blind holes 5 and through holes 6 are both 500 μm, and the average pore density is 15,000 / cm 2 .

[0177] The composite foil provided in this embodiment is prepared by the following method:

[0178] (1) punching the substrate layer 1 with an ion beam to form a porous structure, wherein the porous structure includes blind holes 5 and through holes 6;

[0179] (2) forming a conductive layer 2 on the substrate layer 1 by using an evaporation copper plating process;

[0180] (3) etching away a portion of the conductive layer 2 so that the residual rate is 75%;

[0181] The etching process is the same as that in Example 1.

[0182] The remaining preparation methods and parameters remained the same as in Example 6.

[0183] FIG4 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0184] Example 11

[0185] The difference between this embodiment and embodiment 10 is that:

[0186] In the conductive layer 2, the aperture of a part of the blind holes 5 gradually decreases along the direction from the opening position to the direction away from the opening position, and the aperture of another part of the blind holes 5 gradually increases along the direction from the opening position to the direction away from the opening position. The through hole 6 includes a first through hole 61 and a second through hole 62 connected to the first through hole 61. The aperture of the first through hole 61 gradually decreases from the opening position along the direction close to the second through hole 62, and the aperture of the second through hole 62 gradually decreases along the direction close to the first through hole 61.

[0187] In the substrate layer 1, the apertures of some blind holes 5 gradually decrease in the direction from the opening position to the direction away from the opening position, and the apertures of another part of the blind holes 5 gradually increase in the direction from the opening position to the direction away from the opening position. The through hole 6 includes a first through hole 61 and a second through hole 62 connected to the first through hole 61. The aperture of the first through hole 61 gradually decreases from the opening position in the direction close to the second through hole 62, and the aperture of the second through hole 62 gradually decreases in the direction close to the first through hole 61.

[0188] The rest of the preparation methods and parameters remained the same as in Example 10.

[0189] FIG5 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0190] The peeling force between the battery active material and the composite foil of Examples 6, 10, and 11 was measured. The results are shown in Table 5.

[0191] Table 5

[0192] From the data of Examples 6, 10 and 11, it can be seen that the conductive layer and the substrate layer are both provided with a porous structure, which can improve the bonding strength between the battery active material and the foil. By improving the shapes of the blind holes and through holes, the bonding strength between the battery active material and the foil can be further improved.

[0193] The peeling force of Example 10 is greater than that of Example 6. This is because Example 10 is based on Example 6 and a porous structure (including blind holes and through holes) is set on the substrate layer. When the electrode active slurry is coated on the surface of the conductive layer of the composite foil, the active material slurry diffuses into the blind holes and through holes of the substrate layer through the through-hole structure of the conductive layer, especially through the through-holes of the substrate layer, so that it forms an "I"-shaped structure with the entire foil that is interconnected and integrated, thereby increasing the adhesion strength between the electrode active material and the foil and making it less likely to fall off. At the same time, the porous structure of the substrate layer also expands the space for the growth of metallic lithium dendrites and changes the growth direction of lithium dendrites. Lithium dendrites grow inward along the pores of the conductive layer. The space inside the pores of the substrate layer accommodates the lithium dendrites that continue to grow, preventing them from growing toward the surface of the foil to form burrs, thereby puncturing the positive and negative electrode diaphragms of the battery, causing the battery to short-circuit and cause fire and smoke. The pore structure of the substrate layer can absorb or alleviate the expansion and contraction stresses generated by the insertion and removal of lithium ions during the charging and discharging process of the battery, maintain the integrity of the current collector, and prevent the battery from swelling.

[0194] The peeling force of Example 11 is greater than that of Example 10. This is because the dried active material is embedded in the blind holes of the conductive layer with the groove-engaging structure, and is embedded in the blind holes of the substrate layer through the first and second through holes in the conductive layer, both of which have a tapered structure. When the battery active material diffuses into the blind holes of the conductive layer and the substrate layer, it solidifies and forms a matching groove-engaging structure with the blind holes of the conductive layer and the substrate layer (as shown in Figure 5). In particular, the hole structure gradually increases in diameter from the position close to the hole opening to the position away from the hole opening, forming two raised engaging portions at the hole opening, which firmly clamp the solidified active material embedded in the hole.

[0195] When the battery active material diffuses into the through holes of the conductive layer containing the first through hole and the second through hole and the through holes of the substrate layer respectively, a snap-fitting protrusion is formed at the intersection of the side wall of the first through hole and the side wall of the second through hole (as shown in FIG5 ). After the active material solidifies, a snap-fitting groove that cooperates with the snap-fitting protrusion is formed at the position corresponding to the snap-fitting protrusion. The snap-fitting protrusion and the snap-fitting groove are snapped together to enhance the bonding strength between the electrode active material and the composite foil, thereby preventing the electrode active material from separating from the composite foil.

[0196] Example 12

[0197] The difference between this embodiment and embodiment 6 is that:

[0198] Conductive layers 2 are provided on both sides of the substrate layer 1, which are denoted as a first conductive layer 21 and a second conductive layer 22;

[0199] The residual rates of the first conductive layer 21 and the second conductive layer 22 are both 75%;

[0200] The thickness of the first conductive layer 21 and the second conductive layer 22 are both 2 μm.

[0201] The composite foil provided in this embodiment is prepared by the following method:

[0202] (1) forming a first conductive layer 21 and a second conductive layer 22 on both sides of the substrate layer 1 by using an evaporation copper plating process;

[0203] (2) etching away a portion of the conductive layer 2 by an etching process, so that the residual rates of the first conductive layer 21 and the second conductive layer 22 are both 75%;

[0204] The etching process is the same as that in Example 1.

[0205] The remaining preparation methods and parameters remained the same as in Example 6.

[0206] FIG6 shows a schematic structural diagram of the composite foil prepared in this embodiment.

[0207] Example 13

[0208] The difference between this embodiment and embodiment 6 is that:

[0209] Conductive layers 2 are provided on both sides of the substrate layer 1, which are denoted as a first conductive layer 21 and a second conductive layer 22;

[0210] The residual rate of the first conductive layer 21 is 50%, the pore size is 950 μm, and the average pore density is 25,000 pores / cm 2 ;

[0211] The residual rate of the second conductive layer 22 is 60%, the pore size is 800 μm, and the average pore density is 20,000 / cm 2 ;

[0212] The thickness of the first conductive layer 21 and the second conductive layer 22 are both 2 μm.

[0213] The composite foil provided in this embodiment is prepared by the following method:

[0214] (1) forming a first conductive layer 21 and a second conductive layer 22 on both sides of the substrate layer 1 by using an evaporation copper plating process;

[0215] (2) A portion of the conductive layer 2 is removed by etching, so that the residual rate of the first conductive layer 21 is 50% and the residual rate of the second conductive layer 22 is 60%.

[0216] The remaining preparation methods and parameters remained the same as in Example 6.

[0217] The etching process is the same as that in Example 1.

[0218] The mass energy density of the composite foil batteries of Examples 6, 12, and 13 was measured. The results are shown in Table 6.

[0219] Table 6

[0220] The data from Examples 6, 12, and 13 demonstrate that the dual conductive layer increases the collection and conduction of electrons from the current collector and the electrode active material, enhancing current output and thus increasing the battery's energy density. The residual conductive layer in Example 13 was lower than that in Example 12, resulting in a slight decrease in battery energy density. This indicates that the optimal residual conductive layer rate for the composite foil material of this application is 75%.

[0221] Example 14

[0222] This embodiment is the best embodiment of the present application. The structural diagram of the composite foil prepared in this embodiment is shown in FIG7 . Its specific structure and parameters are as follows:

[0223] The composite foil comprises a substrate layer 1 and a conductive layer 2;

[0224] The conductive layer 2 includes a first conductive layer 21 and a second conductive layer 22. The first conductive layer 21 and the second conductive layer 22 are respectively provided on both sides of the substrate layer 1;

[0225] The thickness of the first conductive layer 21 and the second conductive layer 22 are both 2 μm, and the material is Cu;

[0226] The residual rates of the first conductive layer 21 and the second conductive layer 22 are both 75%;

[0227] The conductive layer 2 and the substrate layer 1 both have a porous structure, and the porous structure includes blind holes 5 and through holes 6;

[0228] The diameter of the blind holes 5 of the conductive layer 2 and the substrate layer 1 is 500 μm, the diameter of the through holes 6 is 500 μm, and the average hole density of the conductive layer 2 and the substrate layer 1 is 15,000 / cm 2 ;

[0229] In the conductive layer 2, the aperture of the blind hole 5 gradually increases from the opening position to the opening position. The through hole 6 includes a first through hole 61 and a second through hole 62 connected to the first through hole 61. The aperture of the first through hole 61 gradually decreases from the opening position to the direction close to the second through hole 62. The aperture of the second through hole 62 gradually decreases from the opening position to the direction close to the first through hole 61.

[0230] In the substrate layer 1, the aperture of the blind hole 5 gradually increases from the opening position to the opening position. The through hole 6 includes a first through hole 61 and a second through hole 62 connected to the first through hole 61. The aperture of the first through hole 61 gradually decreases from the opening position to the direction close to the second through hole 62. The aperture of the second through hole 62 gradually decreases from the opening position to the direction close to the first through hole 61.

[0231] The thickness of the substrate layer 1 is 6 μm and the material is polyethylene terephthalate (PET);

[0232] The composite foil provided in this embodiment further includes a transition layer 3 and an adjustment layer 4 (including a first adjustment layer 41 and a second adjustment layer). The transition layer 3 and the adjustment layer 4 are disposed simultaneously between the first conductive layer 21 and the substrate layer 1, and between the second conductive layer 22 and the substrate layer 1. The first adjustment layer 41 is disposed on the side closest to the substrate layer 1, and the second adjustment layer 42 is disposed on the side closest to the first conductive layer 21 or the side closest to the second conductive layer 22. The transition layer 3 is disposed between the second adjustment layer 42 and the first conductive layer 21 or between the second adjustment layer 42 and the second conductive layer 22.

[0233] The thickness of the transition layer 3 is 0.01 μm and the material is an alloy of Cu and Ni;

[0234] The thickness of the first adjustment layer 41 is 0.2 μm, and the thickness of the second adjustment layer 42 is 0.1 μm. The material of the first adjustment layer 41 is modified epoxy resin, and the material of the second adjustment layer 42 is silane coupling agent (i.e., γ-(2,3-epoxypropoxy)propyltrimethoxysilane).

[0235] The composite foil provided in this embodiment is prepared by the following method:

[0236] (1) forming a first adjustment layer 41 on both sides of the substrate layer 1 by a coating process;

[0237] (2) forming the second adjustment layer 42 on the first adjustment layer 41 on both sides of the substrate layer 1 by a coating process;

[0238] (3) forming transition layers 3 on the second adjustment layer 42 on both sides of the substrate layer 1 by a vacuum sputtering process;

[0239] (4) using an ion beam punching method to punch holes in the substrate layer 1, the first adjustment layer 41, the second adjustment layer 42, and the transition layer 3 to form a porous structure, wherein the porous structure includes blind holes 5 and through holes 6;

[0240] (5) forming a first conductive layer 21 and a second conductive layer 22 on the transition layer 3 on both sides of the substrate layer 1 by an electrolytic copper plating process;

[0241] (6) etching away a portion of the first conductive layer 21 and the second conductive layer 22 by an etching process, so that the residual rate is 75%;

[0242] The etching process is the same as that in Example 1.

[0243] The battery mass energy density of the active material of the composite foil battery of Example 14, the peeling force between the conductive layer and the substrate layer, and the peeling force between the active material and the foil were measured. The results are shown in Table 7.

[0244] Table 7

[0245] Example 15

[0246] The only difference between Example 15 and Example 6 is that the thickness of the conductive layer 2 is 7 μm.

[0247] The remaining preparation methods and parameters remained the same as in Example 6.

[0248] Example 16

[0249] The only difference between Example 16 and Example 6 is that the thickness of the conductive layer 2 is 0.01 μm.

[0250] The remaining preparation methods and parameters remained the same as in Example 6.

[0251] Comparative Example 1

[0252] The difference between Comparative Example 1 and Example 6 is that conventional electrolytic copper foil with a thickness of 2 μm is used as the battery current collector.

[0253] Comparative Example 2

[0254] The difference between Comparative Example 2 and Example 6 is that the conductive layer 2 is not etched and the original surface is retained.

[0255] The remaining preparation methods and parameters remained the same as in Example 6.

[0256] The battery mass energy density, the peeling force between the conductive layer and the substrate layer, and the peeling force between the active material and the foil of the foil battery active materials of Example 6, Examples 15-16, and Comparative Examples 1 and 2 were measured. The results are shown in Table 8.

[0257] Table 8

[0258] Comparing the data results of Examples 15 and 16 with those of Example 6, it can be seen that if the thickness of the conductive layer is too thin, on the one hand, the conductivity of the current collector will be poor, which is not conducive to the collection and conduction of positive and negative electrode electrons and cannot meet the requirements of fast charging of the battery; on the other hand, it will reduce the mechanical properties of the foil, resulting in easy breakage in the subsequent winding process of the battery. During the battery cycle, the current collector is prone to deformation and breakage, which leads to safety problems; if the thickness of the conductive layer is too thick, the weight and volume of the current collector will increase, thereby reducing the energy density of the battery.

[0259] From the comparison of the data results of Comparative Example 1 and Example 6, it can be seen that although the thickness of the current collector is the same, the composite foil provided by the present application can improve the battery energy density due to its reduced mass.

[0260] From the comparison of the data results of Comparative Example 2 and Example 6, it can be seen that although the mass of the current collector is reduced and the energy density is improved compared with Comparative Example 1, the peeling force between the electrode active material and the foil is low, and delamination is easily produced, which greatly reduces the battery performance.

[0261] In summary, the composite foil of the present application reduces the weight of the battery current collector and can significantly increase the battery energy density, which can reach up to 185Wh / kg, an increase of 7% to 24% compared with traditional iron-lithium batteries.

[0262] Performance testing method:

[0263] Test 1: Peel force test:

[0264] Peel test: Peel strength is measured according to the 180° peel force test standard. The sample size is 5mm×20cm. The conductive layer of the foil is peeled off from the base layer, or the active material of the battery electrode prepared above is peeled off from the foil by 5cm using tweezers. The sample is then fixed at both ends of the peel force tester clamp. The tensile tester is used to perform the peel test at a speed of 10mm / min to obtain the average peel strength.

[0265] Test 2: Battery energy density test:

[0266] Battery preparation steps: homogenizing the positive and negative electrode slurries - coating - rolling - slitting - baking - winding - casing - spot welding - baking - liquid injection - cap welding. (Positive electrode: conventional carbon-coated lithium iron ore, conductive agent Carbon ECP, binder PVDF, solvent NMP, aluminum foil; negative electrode: graphite, conductive agent, thickener CMC, binder SBR, composite foil provided by this application).

[0267] Test method: Batteries are tested for performance in accordance with GB / T 31484-2015 and GB / T 31486-2015 standards. The battery energy density is calculated as follows: Energy density = discharge capacity × platform voltage / battery weight; the platform voltage is based on the 1C discharge platform.

[0268] It should also be noted that the conductive layer listed in the embodiments of the present application is Cu. However, other types of metals, such as any one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In or Zn, or an alloy of at least two of the metals, also have the same technical effects and are not listed here one by one.

[0269] The substrate layer listed in the embodiments of the present application includes any one of phenolic resins, alkyd resins, amino resins, polyester resins, polyurethane resins, acrylic resins, vinyl resins, fluororesins, cyanate esters, polystyrenes, vinyl acetates, polyamides, rubbers, urethanes, melamines, BT resins, ABF resins, polypropylenes, polyphenylene sulfides, polyethylene terephthalates or polyimides, or a combination of at least two of them, and also has the same technical effect, which will not be repeated here.

[0270] In the step of forming the conductive layer in the composite foil preparation method, the vacuum sputtering or electrolytic copper foil process is used in the embodiments of this application. In the art, the conductive layer and the base material layer can also be composited by hot pressing. Various preparation methods will not be detailed here.

[0271] The applicant declares that while the above-mentioned embodiments are used to illustrate the process of the present application, the present application is not limited to the above-mentioned process steps, which does not mean that the present application must rely on the above-mentioned process steps in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials used in the present application, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A composite foil, characterized in that: The composite foil material comprises a substrate layer and a conductive layer; the conductive layer is arranged on at least one side of the substrate layer; and the residual rate of the conductive layer on at least one side of the substrate layer is 40-99.8%.

2. The composite foil according to claim 1, characterized in that: The conductive layer includes a first conductive layer and a second conductive layer, and the first conductive layer and the second conductive layer are respectively arranged on both sides of the substrate layer.

3. According to the composite foil material of claim 2, the residual rate of the first conductive layer is greater than the residual rate of the second conductive layer; or the residual rate of the first conductive layer is less than the residual rate of the second conductive layer; or the residual rate of the first conductive layer is equal to the residual rate of the second conductive layer.

4. The composite foil according to claim 1, characterized in that: The conductive layer has a thickness of 0.2-4 μm.

5. The composite foil according to claim 1, characterized in that: The conductive layer is a multi-layer structure formed by stacking at least two conductive sub-layers, and the materials of the at least two conductive sub-layers are the same or different.

6. The composite foil according to claim 5, characterized in that: The conductive layer has a porous structure, and the porous structure includes blind holes and / or through holes.

7. The composite foil according to claim 6, characterized in that: The substrate layer has a porous structure, and the porous structure includes blind holes and / or through holes.

8. The composite foil according to claim 6 or 7, characterized in that: In the conductive layer, the diameters of the blind holes and the through holes are independently 0.01 to 1000 μm; in the substrate layer, the diameters of the blind holes and the through holes are independently 0.01 to 1000 μm.

9. The composite foil according to claim 6 or 7, characterized in that: In the conductive layer, the average hole density of blind holes and through holes is independently 10 to 30,000 per cm 2 In the substrate layer, the average hole density of blind holes and through holes is independently 10 to 30,000 / cm 2 .

10. The composite foil according to any one of claims 1, 2, 3, 6 or 7, characterized in that: The substrate layer is selected from any one or a combination of at least two of the following materials: Phenolic resins, alkyd resins, amino resins, polyester resins, polyurethane resins, acrylic resins, vinyl resins, fluororesins, cyanate esters, polystyrenes, vinyl acetates, polyamides, rubbers, urethanes, melamines, BT resins, ABF resins, polypropylenes, polyphenylene sulfides, polyethylene terephthalates or polyimides.

11. The composite foil according to claim 1, characterized in that: The composite foil further includes a transition layer, and the transition layer is located between the conductive layer and the substrate layer.

12. The composite foil according to claim 1, characterized in that: The composite foil further includes an adjustment layer, and the adjustment layer is located between the conductive layer and the substrate layer.

13. The composite foil according to claim 1, characterized in that: The composite foil further includes a transition layer and an adjustment layer, wherein the transition layer and the adjustment layer are located between the conductive layer and the substrate layer, the transition layer is located on a side close to the conductive layer, and the adjustment layer is located on a side close to the substrate layer.

14. The composite foil according to claim 12 or 13, characterized in that: The number of the adjustment layer is at least one.

15. The composite foil according to claim 12 or 13, characterized in that: The regulating layer is selected from any one or a combination of at least two of the following materials: resin, filler particles, treating agent, coupling agent or activating agent.

16. A battery pole piece, characterized in that: The battery pole piece comprises the composite foil material as described in any one of claims 1-15.

17. A battery, characterized in that: The battery comprises the battery pole piece as claimed in claim 16.

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