Functional current collector, preparation method thereof and bipolar battery

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a functional current collector, a preparation method thereof and a bipolar battery, the functional current collector comprises a negative electrode protection layer, a negative electrode conductive layer, a transition layer, a first positive electrode conductive layer, a second positive electrode conductive layer and a positive electrode protection layer which are stacked; wherein holes exist in the first positive electrode conducting layer, and the porosity is smaller than or equal to 10%. The transition layer and the second positive electrode conducting layer are arranged on the surfaces of the two sides of the first positive electrode conducting layer respectively, the pinhole defect of the first positive electrode conducting layer is repaired, the cycle performance of the battery is improved, and large-scale application and popularization are facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery manufacturing, and relates to a functional current collector, and in particular to a functional current collector, a preparation method thereof, and a battery. Background Art

[0002] With the increasing popularity of electric vehicles, the market is placing higher demands on their battery life. To address this issue, the development of high-energy-density batteries is imperative. Among the various solutions, bipolar batteries, as promising high-energy-density batteries, continue to attract widespread attention.

[0003] A bipolar battery is a battery composed of bipolar pole pieces (pole pieces made by coating positive and negative electrode materials on either side of a current collector) stacked in series. This battery relies on the series conduction of its own current collectors, eliminating the wires between the electrodes in traditional batteries, thereby reducing the battery's mass and volume and increasing its energy density. Furthermore, its series battery structure can increase the battery's output voltage and power, thereby increasing the battery's output power. It is reported that under the same size conditions, a bipolar battery can accommodate 1.4 times the number of cells as a traditional battery, and its output power is approximately 1.5 times that of a traditional battery, showing great potential.

[0004] The current collector, a key component of bipolar batteries, has a significant impact on battery performance due to its structure. Typically, the functional current collector is prepared by combining aluminum foil (13μm) with copper foil (4.5μm). However, due to pinhole defects in the aluminum and copper foils, the prepared functional current collector is prone to localized micro-short circuits during battery cycling, ultimately resulting in poor battery cycling performance.

[0005] It can be seen that how to provide a functional current collector to repair pinhole defects as much as possible and improve the cycle performance of the battery has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a functional current collector, a preparation method thereof, and a bipolar battery. By respectively arranging a transition layer and a second positive conductive layer on the two side surfaces of the first positive conductive layer, the pinhole defects of the first positive conductive layer are repaired, the cycle performance of the battery is improved, and it is conducive to large-scale promotion and application.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a functional current collector, which includes a negative electrode protection layer, a negative electrode conductive layer, a transition layer, a first positive electrode conductive layer, a second positive electrode conductive layer and a positive electrode protection layer that are stacked.

[0009] The first positive electrode conductive layer has holes, and the porosity is ≤10%.

[0010] In response to the pinhole defect problem existing in traditional functional current collectors, the present invention respectively arranges a transition layer and a second positive conductive layer on both side surfaces of the first positive conductive layer to repair the pinhole defects of the first positive conductive layer, thereby avoiding local micro-short circuits during the battery cycle, thereby improving the battery cycle performance. At the same time, the transition layer improves the adhesion between the positive and negative conductive layers, and the positive and negative protective layers play a good protective role on the conductive layers, ultimately significantly improving the overall performance of the bipolar battery.

[0011] Preferably, the density ratio of the second positive electrode conductive layer to the first positive electrode conductive layer is ≥1.

[0012] Preferably, the material of the first positive electrode conductive layer includes aluminum.

[0013] Preferably, the thickness of the first positive electrode conductive layer is 2-20 μm.

[0014] Preferably, the second positive electrode conductive layer is made of aluminum or aluminum alloy.

[0015] Preferably, the thickness of the second positive electrode conductive layer is 10-1000 nm.

[0016] Preferably, the thickness ratio of the second positive electrode conductive layer to the first positive electrode conductive layer is 1:(2-20).

[0017] Preferably, the material of the positive electrode protection layer includes at least one of aluminum oxide, graphene, carbon nano-quantum dots, carbon nanotubes, and carbon nanofibers.

[0018] Preferably, the thickness of the positive electrode protective layer is 5-100 nm, more preferably 10-80 nm.

[0019] Preferably, the material of the transition layer includes at least one of nickel, chromium, silicon, aluminum, zinc, manganese, titanium, vanadium, niobium and tantalum.

[0020] Preferably, the thickness of the transition layer is 10-1000 nm.

[0021] Preferably, an interface layer is further provided between the transition layer and the first positive electrode conductive layer.

[0022] Preferably, the material of the interface layer includes nickel, chromium, nickel-chromium alloy or nickel-chromium-copper alloy.

[0023] Preferably, the material of the negative electrode conductive layer includes at least one of copper, nickel, titanium, carbon, gold, and silver, and more preferably at least one of copper, nickel, and carbon.

[0024] Preferably, the thickness of the negative electrode conductive layer is 500-2000 nm.

[0025] Preferably, the material of the negative electrode protective layer includes at least one of chromium, nickel-based alloy, copper-based alloy, aluminum oxide, silicon oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, copper-chromium oxide, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0026] Preferably, the thickness of the negative electrode protective layer is 5-100 nm, more preferably 10-80 nm.

[0027] In a second aspect, the present invention provides a method for preparing the functional current collector according to the first aspect, the preparation method comprising the following steps:

[0028] (1) depositing a second positive electrode conductive layer and a positive electrode protective layer on one side surface of the first positive electrode conductive layer;

[0029] (2) depositing a transition layer, a negative electrode conductive layer and a negative electrode protective layer on the other side surface of the first positive electrode conductive layer.

[0030] Among them, step (1) and step (2) are performed in no particular order.

[0031] Preferably, the deposition method of the second positive electrode conductive layer includes physical vapor deposition.

[0032] Preferably, the deposition method of the positive electrode protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating.

[0033] Preferably, the deposition method of the transition layer includes physical vapor deposition.

[0034] Preferably, the deposition method of the negative electrode conductive layer includes at least one of physical vapor deposition, electroplating, and chemical plating.

[0035] Preferably, the deposition method of the negative electrode protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating.

[0036] In a third aspect, the present invention provides a bipolar battery comprising the functional current collector as described in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In response to the pinhole defect problem existing in traditional functional current collectors, the present invention respectively arranges a transition layer and a second positive conductive layer on both side surfaces of the first positive conductive layer to repair the pinhole defects of the first positive conductive layer, thereby avoiding local micro-short circuits during the battery cycle, thereby improving the battery cycle performance. At the same time, the transition layer improves the adhesion between the positive and negative conductive layers, and the positive and negative protective layers play a good protective role on the conductive layers, ultimately significantly improving the overall performance of the bipolar battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the functional current collector structure provided by the present invention.

[0040] Among them: 1-negative electrode protection layer; 2-negative electrode conductive layer; 3-transition layer; 4-first positive electrode conductive layer; 5-second positive electrode conductive layer; 6-positive electrode protection layer. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0042] An embodiment of the present invention provides a functional current collector, which includes a stacked negative electrode protection layer, a negative electrode conductive layer, a transition layer, a first positive electrode conductive layer, a second positive electrode conductive layer and a positive electrode protection layer.

[0043] Among them, the first positive electrode conductive layer has holes and the porosity is ≤10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In the present invention, the first positive electrode conductive layer serves as a substrate for the functional current collector, and the transition layer and the second positive electrode conductive layer are respectively used to repair pinhole defects in the first positive electrode conductive layer.

[0045] In response to the pinhole defect problem existing in traditional functional current collectors, the present invention respectively arranges a transition layer and a second positive conductive layer on both side surfaces of the first positive conductive layer to repair the pinhole defects of the first positive conductive layer, thereby avoiding local micro-short circuits during the battery cycle, thereby improving the battery cycle performance. At the same time, the transition layer improves the adhesion between the positive and negative conductive layers, and the positive and negative protective layers play a good protective role on the conductive layers, ultimately significantly improving the overall performance of the bipolar battery.

[0046] In some embodiments, the density ratio of the second positive conductive layer to the first positive conductive layer is ≥1, that is, the density of the second positive conductive layer is greater than or equal to the density of the first positive conductive layer. The density ratio between the two can be 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or 3, but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable.

[0047] The present invention limits the density of the second positive electrode conductive layer to be greater than or equal to the density of the first positive electrode conductive layer, so that the stress distribution of the composite material is more uniform during subsequent stretching and bending processes.

[0048] In some embodiments, the material of the first positive conductive layer includes aluminum.

[0049] In the present invention, the first positive electrode conductive layer serves as a substrate of the functional current collector, provides support for the current collector, and is a part of the positive electrode conductive layer, providing conductivity for the positive electrode conductive layer.

[0050] In some embodiments, the thickness of the first positive electrode conductive layer is 2-20 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] By limiting the thickness of the first positive electrode conductive layer to a reasonable range, the present invention balances the cycling performance and energy density of the bipolar battery. When the thickness of the first positive electrode conductive layer is less than 2 μm, the metal foil becomes more difficult to prepare and its conductivity deteriorates, thereby reducing the cycling performance of the resulting bipolar battery. When the thickness of the first positive electrode conductive layer is greater than 20 μm, the excessively thick functional current collector increases its surface density, thereby reducing the energy density of the bipolar battery.

[0052] In some embodiments, the second positive conductive layer is made of aluminum or aluminum alloy.

[0053] In the present invention, the second positive electrode conductive layer is used to repair the pinhole defects of the first positive electrode conductive layer, improve the cycle performance of the bipolar battery, and provide a certain conductivity for the positive electrode conductive layer.

[0054] In some embodiments, the thickness of the second positive conductive layer is 10-1000 nm, for example, it can be 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] The present invention balances the cycling performance and energy density of the bipolar battery by limiting the thickness of the second positive conductive layer to a reasonable range. When the thickness of the second positive conductive layer is less than 10nm, the pinhole defects in the first positive conductive layer cannot be effectively repaired, thereby reducing the cycling performance of the resulting bipolar battery. When the thickness of the second positive conductive layer is greater than 1000nm, the pinhole defects in the first positive conductive layer have been fully repaired, making it impossible to further increase the repair rate. Instead, the surface density of the functional current collector is too high, thereby reducing the energy density of the bipolar battery.

[0056] In some embodiments, the thickness ratio of the second positive conductive layer to the first positive conductive layer is 1:(2-20), for example, it can be 1:2, 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18 or 1:20, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0057] In some embodiments, the material of the positive electrode protection layer includes at least one of aluminum oxide, graphene, carbon nano-quantum dots, carbon nanotubes, and carbon nanofibers.

[0058] In some embodiments, the thickness of the positive electrode protective layer is 5-100nm, for example, it can be 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, and more preferably 10-80nm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0059] In some embodiments, the material of the transition layer includes at least one of nickel, chromium, silicon, aluminum, zinc, manganese, titanium, vanadium, niobium, and tantalum.

[0060] In the present invention, the transition layer can not only repair the pinhole defects of the first positive electrode conductive layer, but also improve the bonding force between the positive electrode conductive layer and the negative electrode conductive layer.

[0061] In some embodiments, the thickness of the transition layer is 10-1000 nm, for example, it can be 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] By limiting the thickness of the transition layer to a reasonable range, the present invention balances the cycling performance and energy density of the bipolar battery. When the transition layer is less than 10 nm thick, pinhole defects in the first positive conductive layer cannot be effectively repaired, and the adhesion between the positive and negative conductive layers is insufficient, thereby reducing the cycling performance of the resulting bipolar battery. When the transition layer is thicker than 1000 nm, the pinhole defects in the first positive conductive layer are fully repaired, making it impossible to further improve the repair rate. Moreover, the adhesion between the positive and negative conductive layers is limited, resulting in an excessively high surface density of the functional current collector, thereby reducing the energy density of the bipolar battery.

[0063] In some embodiments, an interface layer is further provided between the transition layer and the first positive electrode conductive layer to enhance the repair effect of the transition layer on pinhole defects in the first positive electrode conductive layer, and to enhance the structural stability of the interface, thereby enhancing the cycle performance of the battery.

[0064] In some embodiments, the interface layer is made of nickel, chromium, nickel-chromium alloy, or nickel-chromium-copper alloy.

[0065] In some embodiments, the material of the negative electrode conductive layer includes at least one of copper, nickel, titanium, carbon, gold, and silver. Considering cost, processability, and conductivity, at least one of copper, nickel, and carbon is further preferred.

[0066] In the present invention, the negative electrode conductive layer provides good conductivity for the negative electrode side.

[0067] In some embodiments, the thickness of the negative electrode conductive layer is 500-2000 nm, for example, it can be 500 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm or 2000 nm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0068] By limiting the thickness of the negative electrode conductive layer to a reasonable range, the present invention balances the cycling performance and energy density of the bipolar battery. When the thickness of the negative electrode conductive layer is less than 500nm, the conductivity is poor, reducing the cycling performance of the bipolar battery. When the thickness of the negative electrode conductive layer is greater than 2000nm, the surface density of the functional current collector is too high, thereby reducing the energy density of the bipolar battery.

[0069] In some embodiments, the material of the negative electrode protective layer includes at least one of chromium, nickel-based alloy, copper-based alloy, aluminum oxide, silicon oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, copper-chromium oxide, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0070] In some embodiments, the thickness of the negative electrode protective layer is 5-100 nm, for example, it can be 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, and more preferably 10-80 nm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0071] An embodiment of the present invention further provides a method for preparing the functional current collector described in any of the above embodiments, the preparation method comprising the following steps:

[0072] (1) depositing a second positive electrode conductive layer and a positive electrode protective layer on one side surface of the first positive electrode conductive layer;

[0073] (2) depositing a transition layer, a negative electrode conductive layer and a negative electrode protective layer on the other side surface of the first positive electrode conductive layer.

[0074] Among them, step (1) and step (2) are performed in no particular order.

[0075] In some embodiments, the deposition method of the second positive conductive layer includes physical vapor deposition.

[0076] In some embodiments, the deposition method of the positive electrode protection layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating.

[0077] In some embodiments, the transition layer is deposited by physical vapor deposition.

[0078] In some embodiments, the deposition method of the negative electrode conductive layer includes at least one of physical vapor deposition, electroplating, and chemical plating.

[0079] In some embodiments, the deposition method of the negative electrode protection layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating.

[0080] In the present invention, the physical vapor deposition can be vacuum evaporation or magnetron sputtering, the chemical vapor deposition can be atmospheric pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, the in-situ forming can be a method of in-situ forming a metal oxide passivation layer on the surface of the metal layer, and the coating can be at least one of die coating, blade coating or extrusion coating.

[0081] An embodiment of the present invention further provides a bipolar battery, comprising the functional current collector described in any of the above embodiments.

[0082] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0083] Example 1

[0084] This embodiment provides a functional current collector, such as Figure 1 As shown, the functional current collector includes a stacked negative electrode protection layer 1, a negative electrode conductive layer 2, a transition layer 3, a first positive electrode conductive layer 4, a second positive electrode conductive layer 5 and a positive electrode protection layer 6; wherein, the first positive electrode conductive layer 4 has holes, and the porosity is tested using a fully automatic specific surface and porosity analyzer (BET), and its porosity is measured to be 8%.

[0085] Specifically, the first positive electrode conductive layer 4 is aluminum foil with a thickness of 13 μm and an average density of 2.47 g / cm³. The second positive electrode conductive layer 5 is an aluminum layer with a thickness of 10 nm and an average density of 2.70 g / cm³. The positive electrode protective layer 6 is an aluminum oxide layer with a thickness of 10 nm. The transition layer 3 is a nickel-chromium alloy layer (with a nickel-chromium mass ratio of 4:1) with a thickness of 10 nm. The negative electrode conductive layer 2 is a copper layer with a thickness of 1 μm. The negative electrode protective layer 1 is a graphite layer with a thickness of 10 nm.

[0086] In this embodiment, the average density testing method of the first positive conductive layer 4 and the second positive conductive layer 5 is: first test the material volume V1 and mass M1 of the first positive conductive layer 4, and then test the material volume V2 and mass M2 after stacking the second positive conductive layer 5. The calculation formulas for the average density ρ1 of the first positive conductive layer 4 and the average density ρ2 of the second positive conductive layer 5 are: ρ1 = M1 / V1, ρ2 = (M2-M1) / (V2-V1).

[0087] This embodiment also provides a method for preparing the functional current collector, which specifically includes the following steps:

[0088] (1) An aluminum foil with a porosity of 8% is selected as a substrate and placed in a vacuum evaporation chamber. A high-purity aluminum wire (purity ≥ 99.99 wt%) is melted and evaporated at a high temperature of 1200°C in the metal evaporation chamber. The evaporated aluminum atoms pass through a cooling system in the vacuum coating chamber and are deposited on one side of the aluminum foil, forming an aluminum layer with a thickness of 10 nm, i.e., a second positive electrode conductive layer 5 is prepared on the surface of the first positive electrode conductive layer 4;

[0089] (2) placing the composite aluminum foil obtained in step (1) in a vacuum evaporation chamber, melting and evaporating high-purity aluminum wire (purity ≥99.99 wt%) in the metal evaporation chamber at a high temperature of 1200° C., and introducing oxygen into the evaporation system at a flow rate of 50 mL / min. The evaporated metal aluminum atoms pass through the cooling system in the vacuum coating chamber and react with the oxygen to be deposited on one side surface of the second positive electrode conductive layer 5, forming an aluminum oxide layer with a thickness of 10 nm as the positive electrode protective layer 6;

[0090] (3) The composite metal layer obtained in step (2) is placed in a magnetron sputtering machine, using a nickel-chromium target (purity of 99.99 wt%) as the target material, controlling the target power to 5.0 kW, the argon flow rate to 50 mL / min, the coating vacuum to 0.08 Pa, the coating time to 1 s, and the temperature of the main roller during the coating process to 0° C., and depositing a nickel-chromium alloy layer with a thickness of 10 nm as the transition layer 3 on the other side of the first positive electrode conductive layer 4;

[0091] (4) The composite metal layer obtained in step (3) is placed in a magnetron sputtering machine, with a copper target (purity of 99.99 wt%) as the target material, the target power is controlled to be 10 kW, argon is used as the gas source, the gas flow rate is 80 mL / min, the air pressure in the chamber is 0.08 Pa during operation, the main roller cooling temperature is -10°C, and a copper layer with a thickness of 1 μm is deposited on the surface of the transition layer 3 as the negative electrode conductive layer 2;

[0092] (5) The composite metal layer obtained in step (4) is placed in a magnetron sputtering machine, and a graphite target (purity of 99.99wt%) is used as the target material. The target power is controlled to 5kW, argon is used as the gas source, the gas flow rate is 80mL / min, the air pressure in the cabin is 0.08Pa during operation, the main roller cooling temperature is -5°C, and a graphite layer with a thickness of 10nm is deposited on the surface of the negative electrode conductive layer 2 as the negative electrode protective layer 1, and finally a functional current collector with a total thickness of 14.04μm is obtained.

[0093] Example 2

[0094] This embodiment provides a functional current collector. Except for selecting aluminum foil with a porosity of 10% as the substrate and the average density of the first positive electrode conductive layer 4 being 2.42 g / cm3, the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0095] Example 3

[0096] This embodiment provides a functional current collector. Except that the thickness of the first positive electrode conductive layer 4 is changed to 2 μm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0097] Example 4

[0098] This embodiment provides a functional current collector. Except that the thickness of the first positive electrode conductive layer 4 is changed to 20 μm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0099] Example 5

[0100] This embodiment provides a functional current collector. Except that the thickness of the first positive electrode conductive layer 4 is changed to 1 μm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0101] Example 6

[0102] This embodiment provides a functional current collector. Except that the thickness of the first positive electrode conductive layer 4 is changed to 22 μm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0103] Example 7

[0104] This embodiment provides a functional current collector. Except that the thickness of the second positive electrode conductive layer 5 is changed to 100 nm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0105] Example 8

[0106] This embodiment provides a functional current collector. Except that the thickness of the second positive electrode conductive layer 5 is changed to 1000 nm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0107] Example 9

[0108] This embodiment provides a functional current collector. Except that the thickness of the second positive electrode conductive layer 5 is changed to 5 nm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0109] Example 10

[0110] This embodiment provides a functional current collector. Except that the thickness of the second positive electrode conductive layer 5 is changed to 1010 nm, the rest of the structure and conditions are the same as those of the embodiment 1, and therefore will not be described in detail here.

[0111] Example 11

[0112] This embodiment provides a functional current collector. Except that the material of the transition layer 3 is changed to silicon-aluminum alloy (silicon-aluminum mass ratio is 9:1), the rest of the structure and conditions are the same as those in Example 1, so they are not described here.

[0113] In this embodiment, the preparation process of the transition layer 3 is changed to: using a silicon aluminum target (purity of 99.99wt%) as the target material, controlling the target power to 8.0kW, the argon flow rate to 70mL / min, the coating vacuum to 0.08Pa, the coating time to 4s, and the temperature of the main roller during the coating process to -15°C.

[0114] Example 12

[0115] This embodiment provides a functional current collector. Except that the thickness of the transition layer 3 is changed to 100 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0116] Example 13

[0117] This embodiment provides a functional current collector. Except that the thickness of the transition layer 3 is changed to 1000 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0118] Example 14

[0119] This embodiment provides a functional current collector. Except that the thickness of the transition layer 3 is changed to 5 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0120] Example 15

[0121] This embodiment provides a functional current collector. Except that the thickness of the transition layer 3 is changed to 1010 nm, the rest of the structure and conditions are the same as those of the embodiment 1, so they are not described here in detail.

[0122] Example 16

[0123] This embodiment provides a functional current collector. Except for adding a nickel-chromium-copper alloy layer with a thickness of 10 nm (nickel-chromium-copper mass ratio of 4:1:1) as an interface layer (not shown in the figure) between the transition layer 3 and the first positive conductive layer 4, the remaining structures and conditions are the same as those in Example 1, so they are not repeated here.

[0124] Example 17

[0125] This embodiment provides a functional current collector. Except that the material of the negative electrode conductive layer 2 is changed to nickel, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0126] Example 18

[0127] This embodiment provides a functional current collector. Except that the material of the negative electrode conductive layer 2 is changed to carbon, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0128] Example 19

[0129] This embodiment provides a functional current collector. Except that the thickness of the negative electrode conductive layer 2 is changed to 500 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0130] Example 20

[0131] This embodiment provides a functional current collector. Except that the thickness of the negative electrode conductive layer 2 is changed to 2000 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0132] Example 21

[0133] This embodiment provides a functional current collector. Except that the thickness of the negative electrode conductive layer 2 is changed to 450 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0134] Example 22

[0135] This embodiment provides a functional current collector. Except that the thickness of the negative electrode conductive layer 2 is changed to 2050 nm, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0136] Example 23

[0137] This embodiment provides a functional current collector. Except that the material of the transition layer 3 is changed to aluminum-nickel-chromium alloy (the mass ratio of aluminum-nickel-chromium is 1:4:1), the rest of the structure and conditions are the same as those of Example 1, so they are not described here.

[0138] In this embodiment, the preparation process of the transition layer 3 is changed to: using an aluminum-nickel-chromium target (purity of 99.99wt%) as the target material, controlling the target power to 4.0kW, the argon flow rate to 70mL / min, the coating vacuum to 0.08Pa, the coating time to 1s, and the temperature of the main roller during the coating process to -15°C.

[0139] Example 24

[0140] This embodiment provides a functional current collector. Except that the material of the transition layer 3 is changed to aluminum-tantalum alloy (the mass ratio of aluminum to tantalum is 2:1), the rest of the structure and conditions are the same as those in Example 1, so they are not described here.

[0141] In this embodiment, the preparation process of the transition layer 3 is changed to: using an aluminum tantalum target (purity of 99.99wt%) as the target material, controlling the target power to 6.0kW, the argon flow rate to 70mL / min, the coating vacuum to 0.08Pa, the coating time to 1s, and the temperature of the main roller during the coating process to -15°C.

[0142] Example 25

[0143] This embodiment provides a functional current collector. Except that the material of the transition layer 3 is changed to aluminum-titanium-tantalum alloy (the mass ratio of aluminum-titanium-tantalum is 2:1:1), the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0144] In this embodiment, the preparation process of the transition layer 3 is changed to: using an aluminum titanium tantalum target (purity of 99.99wt%) as the target material, controlling the target power to 5.5kW, the argon flow rate to 70mL / min, the coating vacuum to 0.08Pa, the coating time to 1s, and the temperature of the main roller during the coating process to -15°C.

[0145] Example 26

[0146] This embodiment provides a functional current collector. Except for adding a nickel-chromium-copper alloy layer with a thickness of 10 nm (nickel-chromium-copper mass ratio of 4:1:1) as an interface layer (not shown in the figure) between the transition layer 3 and the first positive conductive layer 4, the rest of the structure and conditions are the same as those in Example 23, so they are not repeated here.

[0147] Example 27

[0148] This embodiment provides a functional current collector. Except for adding a nickel-chromium-copper alloy layer with a thickness of 10 nm (nickel-chromium-copper mass ratio of 4:1:1) as an interface layer (not shown in the figure) between the transition layer 3 and the first positive conductive layer 4, the rest of the structure and conditions are the same as those in Example 24, so they are not repeated here.

[0149] Example 28

[0150] This embodiment provides a functional current collector. Except for adding a nickel-chromium-copper alloy layer with a thickness of 10 nm (nickel-chromium-copper mass ratio of 4:1:1) as an interface layer between the transition layer 3 and the first positive conductive layer 4 (not shown in the figure), the rest of the structure and conditions are the same as those in Example 25, so they are not repeated here.

[0151] Example 29

[0152] This embodiment provides a functional current collector. Except that the average density of the second positive electrode conductive layer 5 is changed to 2.39 g / cm 3 , the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0153] In this embodiment, the preparation conditions of the second positive electrode conductive layer 5 are substantially the same as those in embodiment 1, with the only difference being that argon gas is introduced during the preparation process, and the flow rate of the argon gas is 50 mL / min.

[0154] Example 30

[0155] This embodiment provides a functional current collector. Except for selecting aluminum foil with a porosity of 3% as the substrate and the average density of the first positive electrode conductive layer 4 being 2.61 g / cm3, the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0156] Comparative Example 1

[0157] This comparative example provides a functional current collector. Except that the second positive electrode conductive layer 5 is not provided, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0158] Comparative Example 2

[0159] This comparative example provides a functional current collector. Except that the transition layer 3 is not provided, the rest of the structure and conditions are the same as those of Example 1, so they are not described here in detail.

[0160] Comparative Example 3

[0161] This comparative example provides a functional current collector. Except for selecting aluminum foil with a porosity of 15% as the substrate and the average density of the first positive electrode conductive layer 4 being 2.29 g / cm3, the rest of the structure and conditions are the same as those in Example 1, so they are not repeated here.

[0162] Comparative Example 4

[0163] This comparative example provides a functional current collector, the preparation method of which is as follows: an aluminum foil (1060 alloy) with a thickness of 13 μm is selected as the substrate, a layer of conductive glue (Benno 3318UF) with a thickness of 0.1 μm is coated on its surface, and then it is laminated with an electrolytic copper foil with a thickness of 4.5 μm, and then placed in a 150°C oven and baked for 10 minutes to obtain a functional current collector with a thickness of 17.5 μm.

[0164] Performance Testing

[0165] (1) Pinhole defect test: The functional current collector is placed in a pinhole defect detection system (micro-visual charge coupled device CCD), scanned, and then the optical signal is converted into an electrical signal and transmitted to the computer to count the number of pinhole defects in the sample.

[0166] (2) Battery assembly:

[0167] (a) Coating the positive electrode active material on one side of the positive electrode conductive layer, including LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black Super P, PVDF 5130, carbon nanotubes CNT, and the mass ratio of the above four materials is 96:1.8:1.7:0.5;

[0168] (b) coating one side of the negative electrode conductive layer with a negative electrode active material, including graphite, conductive carbon black Super P, carbon nanotubes, and CMC, with the mass ratio of the above four materials being 96:3:0.6:0.4;

[0169] (c) Using Li6PS5Cl as the solid electrolyte, a soft-pack battery with a capacity of 3Ah was assembled according to the assembly process of bipolar solid-state batteries.

[0170] (3) The soft-pack battery assembled above was subjected to a cycle performance test under the following test conditions: charging with a constant current constant voltage (CCCV) method at a rate of 1C and discharging with a constant current (CC) method at a rate of 1C for 2000 cycles. The battery capacity retention rate after 2000 cycles of charge and discharge was recorded, i.e., the battery capacity after 2000 cycles of charge and discharge / the initial capacity of the battery × 100%.

[0171] The test results of the functional current collectors and corresponding soft-pack batteries obtained in Examples 1-30 and Comparative Examples 1-4 are shown in Table 1 below.

[0172] Table 1

[0173]

[0174]

[0175] It can be seen that in order to solve the pinhole defect problem existing in the traditional functional current collector, the present invention repairs the pinhole defects of the first positive conductive layer by respectively arranging a transition layer and a second positive conductive layer on the two side surfaces of the first positive conductive layer, thereby avoiding local micro-short circuits in the battery during the cycle, thereby improving the cycle performance of the battery. At the same time, the transition layer improves the adhesion between the positive and negative conductive layers, and the positive and negative protective layers play a good protective role on the conductive layers, ultimately significantly improving the overall performance of the bipolar battery.

[0176] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A functional current collector, characterized in that: The functional current collector comprises a negative electrode protection layer, a negative electrode conductive layer, a transition layer, a first positive electrode conductive layer, a second positive electrode conductive layer and a positive electrode protection layer which are stacked; The first positive electrode conductive layer has holes, and the porosity is ≤10%.

2. The functional current collector according to claim 1, characterized in that: The density ratio of the second positive electrode conductive layer to the first positive electrode conductive layer is ≥1.

3. The functional current collector according to claim 1 or 2, characterized in that: The material of the first positive electrode conductive layer includes aluminum; And / or, the thickness of the first positive electrode conductive layer is 2-20 μm; And / or, the material of the second positive electrode conductive layer includes aluminum or aluminum alloy; And / or, the thickness of the second positive electrode conductive layer is 10-1000 nm; And / or, the thickness ratio of the second positive electrode conductive layer to the first positive electrode conductive layer is 1:(2-20).

4. The functional current collector according to claim 1 or 2, characterized in that: The material of the positive electrode protective layer includes at least one of aluminum oxide, graphene, carbon nano-quantum dots, carbon nanotubes, and carbon nanofibers; And / or, the thickness of the positive electrode protective layer is 5-100 nm, more preferably 10-80 nm.

5. The functional current collector according to claim 1 or 2, characterized in that: The material of the transition layer includes at least one of nickel, chromium, silicon, aluminum, zinc, manganese, titanium, vanadium, niobium, and tantalum; And / or, the thickness of the transition layer is 10-1000 nm; And / or, an interface layer is further provided between the transition layer and the first positive electrode conductive layer; The material of the interface layer includes nickel, chromium, nickel-chromium alloy or nickel-chromium-copper alloy.

6. The functional current collector according to claim 1 or 2, characterized in that: The material of the negative electrode conductive layer includes at least one of copper, nickel, titanium, carbon, gold, and silver, and is more preferably at least one of copper, nickel, and carbon; And / or, the thickness of the negative electrode conductive layer is 500-2000 nm.

7. The functional current collector according to claim 1 or 2, characterized in that: The material of the negative electrode protective layer includes at least one of chromium, nickel-based alloy, copper-based alloy, aluminum oxide, silicon oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, copper-chromium oxide, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers, and graphene; And / or, the thickness of the negative electrode protective layer is 5-100 nm, more preferably 10-80 nm.

8. A method for preparing the functional current collector according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) depositing a second positive electrode conductive layer and a positive electrode protective layer on one side surface of the first positive electrode conductive layer; (2) depositing a transition layer, a negative electrode conductive layer, and a negative electrode protective layer on the other side surface of the first positive electrode conductive layer; Among them, step (1) and step (2) are performed in no particular order.

9. The method for preparing the functional current collector according to claim 8, wherein: The deposition method of the second positive electrode conductive layer includes physical vapor deposition; And / or, the deposition method of the positive electrode protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating; and / or, the deposition method of the transition layer comprises physical vapor deposition; And / or, the deposition method of the negative electrode conductive layer includes at least one of physical vapor deposition, electroplating, and chemical plating; And / or, the deposition method of the negative electrode protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating.

10. A battery, characterized in that: The bipolar battery comprises the functional current collector according to any one of claims 1 to 7.

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