Composite metal current collector and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a composite metal current collector and a preparation method and application thereof, the composite metal current collector comprises a first metal layer and a second metal layer which are laminated, and the Mohs hardness M1 of the first metal layer and the Mohs hardness M2 of the second metal layer meet the following condition: 0 < M1-M2 < = 0.5. By designing the composite metal current collector with a laminated structure and reasonably limiting the hardness relationship among different metal layers, the physical and mechanical property matching among the metal layers is realized, the alloying reaction is avoided, the cycle stability is improved, meanwhile, the volume expansion phenomenon is relieved, the energy density of the battery is improved, and large-scale popularization and application are facilitated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery manufacturing, and relates to a current collector, in particular to a composite metal current collector and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of new energy technology, the demand for high-performance batteries is showing an explosive growth trend. Among the many battery technology routes, zinc batteries and sodium batteries have outstanding advantages, such as higher energy density, environmental friendliness, and relatively abundant resources. The above advantages make zinc batteries and sodium batteries have broad application prospects in new energy vehicles, energy storage systems and many other fields.

[0003] However, in the practical application of zinc batteries and sodium batteries, the current collector as an important component of the battery becomes a key factor restricting the overall performance improvement of the battery. The existing current collector materials in the application of the two batteries all face a series of problems to be solved. Traditional current collector materials have many shortcomings when they face the working environment of zinc batteries and sodium batteries. These shortcomings seriously affect the various performance indicators of the battery and hinder the further development and large-scale application of battery technology.

[0004] Specifically, copper foil, as one of the traditional current collector materials, has obvious defects when applied in zinc batteries. When copper foil is used as a current collector, zinc is prone to irreversible alloying reaction during deposition on its surface. This reaction will directly lead to a significant reduction in the coulombic efficiency of the battery, causing serious energy loss during the charging and discharging process of the battery; at the same time, it also causes poor cycle stability and greatly shortens the service life of the battery. In addition, copper foil itself is relatively high in price, which undoubtedly increases the overall manufacturing cost of the battery. Under the background of large-scale popularization and application of batteries, the cost problem has become a huge obstacle, limiting the popularization of batteries in more fields.

[0005] Another traditional current collector material, zinc foil, also faces many challenges in application. During the charging and discharging process of the battery, zinc foil will have a relatively obvious volume expansion phenomenon, which is easy to cause the current collector to be perforated. Once the current collector is perforated, it will not only affect the normal work of the battery, but also pose a serious threat to the service life and safety of the battery. At the same time, the low depth of discharge of zinc foil is not conducive to improving the energy density of the battery, and cannot meet the growing demand for high energy density batteries.

[0006] In view of the above problems of zinc foil, the technical personnel mainly take measures such as surface treatment or building a composite structure, for example, by building a three-dimensional porous structure to increase the specific surface area of zinc foil, thereby improving its stability to a certain extent. However, these methods still have obvious limitations and cannot fundamentally solve the key problems in the application of zinc foil.

[0007] Therefore, how to provide a current collector, avoid alloying reaction, improve cycle stability, and at the same time alleviate the volume expansion phenomenon and improve the energy density of the battery, has become a problem to be solved by the person skilled in the art. SUMMARY

[0008] In view of the deficiencies in the prior art, the purpose of the present application is to provide a composite metal current collector and its preparation method and application, by designing a composite metal current collector with a laminated structure and reasonably limiting the hardness relationship between different metal layers, realizing the physical and mechanical property matching between the metal layers, avoiding alloying reaction, improving cycle stability, and at the same time alleviating the volume expansion phenomenon and improving the energy density of the battery.

[0009] To achieve the purpose of the present application, the following technical solutions are adopted:

[0010] In a first aspect, the present application provides a composite metal current collector, which comprises a first metal layer and a second metal layer arranged in a laminated manner, and the Mohs hardness M1 of the first metal layer and the Mohs hardness M2 of the second metal layer satisfy: 0

[0011] The present application realizes the physical and mechanical property matching between the metal layers by designing a composite metal current collector with a laminated structure and reasonably limiting the Mohs hardness relationship between different metal layers. On the one hand, the metal layers with similar hardness can better withstand external forces during processing and use, thereby reducing the stress concentration and damage phenomenon caused by the hardness difference and improving the mechanical stability of the current collector; on the other hand, the metal layers with similar hardness can better embed each other, thereby enhancing the bonding strength of the interface and reducing the risk of interlayer peeling. At the same time, the metal layers with similar hardness can sufficiently reduce the contact resistance at the interface, reduce the internal resistance of the battery, and significantly improve the power output of the battery.

[0012] Preferably, the first metal layer is used for loading positive active material.

[0013] The present application limits the Mohs hardness of the first metal layer loading positive active material to be greater than that of the second metal layer, so that the second metal layer with smaller hardness can better adapt to the expansion and contraction of the negative active material when the volume changes during the charging and discharging process of the battery, thereby improving the cycle stability and energy density of the battery.

[0014] Preferably, the thickness ratio of the first metal layer to the second metal layer is (10-70):1, and further preferably (10-35):1.

[0015] Preferably, the thickness of the first metal layer is 5-60 μm.

[0016] Preferably, the porosity k1 of the first metal layer and the porosity k2 of the second metal layer satisfy: 0.5% < k2-k1 < 1%.

[0017] Preferably, the porosity k1 of the first metal layer is < 0.5%.

[0018] Preferably, the porosity k2 of the second metal layer is < 2%.

[0019] Preferably, the material of the first metal layer and the second metal layer respectively independently comprises at least one of aluminum, aluminum alloy, zinc, silver, silver alloy, tin, tin alloy, copper, copper alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, manganese alloy or lead.

[0020] Preferably, the material of the first metal layer comprises aluminum.

[0021] Preferably, the material of the second metal layer comprises zinc, further preferably zinc and oxygen.

[0022] Preferably, the content of oxygen in the second metal layer is ≤ 2wt%, further preferably 0.5wt%-2wt%.

[0023] Preferably, the first metal layer is a single-layer structure.

[0024] Preferably, the second metal layer is a multi-layer structure, comprising at least 2 second metal sub-layers, further preferably at least 5 second metal sub-layers.

[0025] In a second aspect, the present application provides a preparation method of the composite metal current collector as described in the first aspect, the preparation method comprising: first preparing a first metal layer, and then depositing a second metal layer on one side surface of the first metal layer to obtain the composite metal current collector.

[0026] In a third aspect, the present application provides a battery comprising the composite metal current collector as described in the first aspect.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The present application realizes the matching of physical and mechanical properties between metal layers by designing a composite metal current collector with a laminated structure and reasonably limiting the Mohs hardness relationship between different metal layers. On the one hand, metal layers with similar hardness can better withstand external forces during processing and use, thereby reducing stress concentration and damage phenomena caused by hardness differences and improving the mechanical stability of the current collector. On the other hand, metal layers with similar hardness can better embed each other, thereby enhancing the bonding strength of the interface and reducing the risk of interlayer peeling. At the same time, metal layers with similar hardness can substantially reduce the contact resistance at the interface, reduce the internal resistance of the battery, and significantly improve the power output of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a schematic diagram of a composite metal current collector structure provided by the present application.

[0030] 1 - first metal layer; 2 - second metal layer. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0032] In some embodiments of the present application, a composite metal current collector is provided, which includes a first metal layer and a second metal layer arranged in a laminated manner, and the Mohs hardness M1 of the first metal layer and the Mohs hardness M2 of the second metal layer satisfy: 0 < M1-M2≤0.5, for example, M1-M2 can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0033] The present application realizes the matching of physical and mechanical properties between metal layers by designing a composite metal current collector with a laminated structure and reasonably limiting the Mohs hardness relationship between different metal layers. On the one hand, metal layers with similar hardness can better withstand external forces during processing and use, thereby reducing stress concentration and damage phenomena caused by hardness differences and improving the mechanical stability of the current collector. On the other hand, metal layers with similar hardness can better embed each other, thereby enhancing the bonding strength of the interface and reducing the risk of interlayer peeling. At the same time, metal layers with similar hardness can substantially reduce the contact resistance at the interface, reduce the internal resistance of the battery, and significantly improve the power output of the battery.

[0034] In some embodiments, the first metal layer is used to load a positive active material.

[0035] The present application limits the Mohs hardness of the first metal layer loaded with positive electrode active material to be greater than the second metal layer, so that the second metal layer with smaller hardness can better adapt to the expansion and shrinkage of the negative electrode active material when the volume changes during the charging and discharging process of the battery, thereby improving the cycle stability and energy density of the battery.

[0036] In some embodiments, the thickness ratio of the first metal layer and the second metal layer is (10-70):1, for example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1 or 70:1, preferably (10-35):1, but not limited to the listed values, other values not listed in this range are also applicable.

[0037] The present application reasonably limits the thickness relationship between the first metal layer and the second metal layer, fully guarantees the mechanical properties of the current collector and the mechanical stability during the cycle process, and alleviates the deformation phenomenon of the current collector caused by the expansion and shrinkage of the active material.

[0038] In some embodiments, the thickness of the first metal layer is 5-60μm, for example, it can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm or 60μm, but not limited to the listed values, other values not listed in this range are also applicable.

[0039] In some embodiments, the porosity k1 of the first metal layer and the porosity k2 of the second metal layer satisfy: 0.5% < k2-k1 < 1%, for example, it can be k2-k1 = 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9% or 0.95%, but not limited to the listed values, other values not listed in this range are also applicable.

[0040] In some embodiments, the porosity k1 of the first metal layer is <0.5%, for example, it can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.45%, but not limited to the listed values, other values not listed in this range are also applicable.

[0041] In some embodiments, the porosity k2 of the second metal layer is <2%, for example, it can be 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6% or 1.8%, but not limited to the listed values, other values not listed in this range are also applicable.

[0042] The application effectively solves the stress concentration phenomenon caused by the difference in porosity of the metal layer, reduces the appearance problem of the second metal layer caused by the release of residual stress during the preparation process, and significantly improves the mechanical properties of the current collector.

[0043] In some embodiments, the material of the first metal layer and the second metal layer respectively independently comprises at least one of aluminum, aluminum alloy, zinc, silver, silver alloy, tin, tin alloy, copper, copper alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, manganese alloy or lead.

[0044] In some embodiments, the material of the first metal layer comprises aluminum.

[0045] In some embodiments, the material of the second metal layer comprises zinc.

[0046] In some embodiments, the material of the second metal layer comprises zinc and oxygen.

[0047] In some embodiments, the content of oxygen in the second metal layer is ≤2wt%, for example, it can be 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt% or 2wt%, preferably 0.5wt%-2wt%, but not limited to the listed values, other values not listed in the range are also applicable.

[0048] By incorporating a certain amount of oxygen in the second metal layer, the application can significantly increase the transmission and deposition of zinc ions regulated by the surface polarity, and make them uniformly distributed on the surface of the zinc negative electrode, thereby inhibiting the formation of dendrites. This is because the presence of oxygen can provide uniform nucleation sites for zinc ions, reduce the nucleation overpotential of zinc ions, enhance the chemical adsorption capacity of zinc ions on the electrode surface, thereby improving the overall electrochemical performance of the battery, and ultimately improving the cycle life and coulombic efficiency of the battery. At the same time, the incorporation of oxygen can further improve the bonding force between the first metal layer and the second metal layer, reducing the risk of interlayer peeling.

[0049] In the application, the content of oxygen in the second metal layer can be specifically adjusted by the flow rate of oxygen.

[0050] In some embodiments, the first metal layer is a single-layer structure.

[0051] In some embodiments, the second metal layer is a multi-layer structure, comprising at least 2 layers of second metal sublayers, for example, it can be 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers or 8 layers, preferably at least 5 layers of second metal sublayers, but not limited to the listed values, other values not listed in the range are also applicable.

[0052] An embodiment of the present invention also provides a method for preparing the composite metal current collector described in any of the above embodiments, the preparation method comprising: first preparing a first metal layer, and then depositing a second metal layer on one side surface of the first metal layer to obtain the composite metal current collector.

[0053] In the present invention, the preparation of the first metal layer may include smelting, casting and cold rolling in sequence, and the deposition of the second metal layer may include vacuum evaporation. As long as the corresponding metal layer can be successfully prepared, the specific preparation process and conditions are not specifically limited here.

[0054] A certain embodiment of the present invention further provides a battery, comprising the composite metal current collector as described in any of the above embodiments.

[0055] 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.

[0056] Example 1

[0057] This embodiment provides a composite metal current collector, such as Figure 1 As shown, the composite metal current collector includes a first metal layer 1 and a second metal layer 2 stacked together, wherein the first metal layer 1 is used to load the positive electrode active material, and the material of the first metal layer 1 is aluminum, with a Mohs hardness of M1 = 2.75, and the material of the second metal layer 2 is zinc, with a Mohs hardness of M2 = 2.5, that is, the Mohs hardness difference between the two is M1-M2 = 0.25.

[0058] Specifically, the first metal layer 1 is a single-layer structure with a thickness of 35 μm, a porosity of 0.3%, and a grain size D50 of 5 μm; the second metal layer 2 is divided into 6 layers (not shown in the figure), with a total thickness of 2 μm, a porosity of 1.2%, a grain size D50 of 200 μm, and an oxygen content of 1.5 wt%.

[0059] In this embodiment, the preparation method of the composite metal current collector includes: using aluminum foil as the first metal layer 1 and placing it in a magnetron sputtering device, the oxygen content of the zinc target used is 0.8%, the magnetron sputtering process parameters are pure argon, and the magnetron sputtering pressure is 2.4×10 -3 mbar, the porosity of the zinc layer is 1.2%; 6 layers of metal zinc are plated on the surface of the aluminum foil as the second metal layer 2, thereby obtaining the composite metal current collector.

[0060] Example 2

[0061] The embodiment provides a composite metal current collector, wherein the total thickness of the second metal layer 2 is changed to 1 μm by regulating the time of magnetron sputtering, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0062] Embodiment 3

[0063] The embodiment provides a composite metal current collector, wherein the thickness of the first metal layer 1 is changed to 30 μm, the total thickness of the second metal layer 2 is changed to 3 μm by regulating the time of magnetron sputtering, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0064] Embodiment 4

[0065] The embodiment provides a composite metal current collector, wherein the thickness of the first metal layer 1 is changed to 8 μm, the total thickness of the second metal layer 2 is changed to 1 μm by regulating the time of magnetron sputtering, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0066] Embodiment 5

[0067] The embodiment provides a composite metal current collector, wherein the porosity of the second metal layer 2 is changed to 0.8% by regulating the air pressure (2.0*10 - 3 mbar) of magnetron sputtering, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0068] Embodiment 6

[0069] The embodiment provides a composite metal current collector, wherein the porosity of the second metal layer 2 is changed to 1.3% by regulating the air pressure (2.5*10 - 3 mbar) of magnetron sputtering, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0070] Embodiment 7

[0071] The embodiment provides a composite metal current collector, wherein the oxygen content in the zinc target is changed to 0.5% to plate the second metal layer 2 with the oxygen content of 0.5%, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0072] Embodiment 8

[0073] The embodiment provides a composite metal current collector, wherein the oxygen content in the zinc target is changed to 0.3% to plate the second metal layer 2 with the oxygen content of 0.3%, and the rest of the structure and conditions are the same as those in the embodiment 1, so the rest of the structure and conditions are not described here.

[0074] Embodiment 9

[0075] This example provides a composite metal current collector, except that the oxygen content in the zinc target is changed to 2% to plate a second metal layer 2 with an oxygen content of 2%, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0076] Example 10

[0077] This example provides a composite metal current collector, except that the oxygen content in the zinc target is changed to 2.5% to plate a second metal layer 2 with an oxygen content of 2.5%, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0078] Example 11

[0079] This example provides a composite metal current collector, except that only one layer of zinc metal with a thickness of 2 μm is plated on the surface of the aluminum foil as the second metal layer 2, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0080] Example 12

[0081] This example provides a composite metal current collector, except that the porosity of the second metal layer 2 is changed to 1.8% by adjusting the gas pressure (3.0 x 10 - 3 mbar) of the magnetron sputtering, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0082] Example 13

[0083] This example provides a composite metal current collector, except that an aluminum foil with a porosity of 0.2% is selected as the first metal layer 1, and the porosity of the second metal layer 2 is changed to 0.6% by adjusting the gas pressure (1.8 x 10 -3 mbar) of the magnetron sputtering, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0084] Comparative Example 1

[0085] This comparative example provides a composite metal current collector, except that the material of the second metal layer 2 is changed to copper, and the oxygen content in the copper target is 0.8%, and the rest of the structure and conditions are the same as in Example 1, so here is not described.

[0086] Performance Test

[0087] (1) Adhesion test: cut the current collector sample into a test sample with a width of 24 mm and a length of 300 mm, fold the one end of the test sample with the adhesive surface facing each other to form a folded layer about 12 mm long; paste the other end of the test sample to one end of the steel plate, and roll it twice with an adhesive tape pressure roller at a speed of 600 mm / min; place it in an electronic peeling tester, set the test speed to 300 mm / min, and the sample width to 24 mm; the equipment automatically records the force value during peeling, and this is taken as the adhesion between the first metal layer and the second metal layer; then repeat the above test after the sample is left for 3 months, and calculate the adhesion change value.

[0088] (2) Bending test: refer to GB / T 238 "Metal material wire repeated bending test method" to repeat the bending of the current collector, and record the bending number when the cracks appear on the surface of the current collector;

[0089] The test results of the current collectors obtained in the above examples and comparative examples are shown in Table 1 below.

[0090] Table 1

[0091]

[0092]

[0093] It can be seen that by designing the composite metal current collector with a laminated structure and reasonably limiting the Mohs hardness relationship between different metal layers, the physical and mechanical properties of the metal layers are matched. On the one hand, the metal layers with similar hardness can better withstand external forces during processing and use, thereby reducing stress concentration and damage caused by hardness differences and improving the mechanical stability of the current collector; on the other hand, the metal layers with similar hardness can better embed each other, thereby enhancing the bonding strength of the interface and reducing the risk of interlayer peeling.

[0094] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A composite metal current collector, characterized in that: The composite metal current collector includes a first metal layer and a second metal layer stacked together, and the Mohs hardness M1 of the first metal layer and the Mohs hardness M2 of the second metal layer satisfy: 0<M1-M2≤0.

5.

2. The composite metal current collector according to claim 1, characterized in that The first metal layer is used to support positive electrode active materials.

3. The composite metal current collector according to claim 1 or 2, characterized in that: The thickness ratio of the first metal layer to the second metal layer is (10-70):1, preferably (10-35):1; And / or, the thickness of the first metal layer is 5-60 μm.

4. The composite metal current collector according to claim 1 or 2, characterized in that: The porosity k1 of the first metal layer and the porosity k2 of the second metal layer satisfy: 0.5%<k2-k1<1%; and / or, the porosity k1 of the first metal layer is less than 0.5%; And / or, the porosity k2 of the second metal layer is less than 2%.

5. The composite metal current collector according to claim 1 or 2, characterized in that: The materials of the first metal layer and the second metal layer independently include at least one of aluminum, aluminum alloy, zinc, silver, silver alloy, tin, tin alloy, copper, copper alloy, gold, gold alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, manganese, manganese alloy or lead.

6. The composite metal current collector according to claim 5, characterized in that: The material of the first metal layer includes aluminum; And / or, the material of the second metal layer includes zinc.

7. The composite metal current collector according to claim 6, characterized in that: The material of the second metal layer includes zinc and oxygen; And / or, the oxygen content in the second metal layer is ≤2 wt%, preferably 0.5 wt%-2 wt%.

8. The composite metal current collector according to claim 1 or 2, characterized in that: The first metal layer is a single-layer structure; And / or, the second metal layer is a multi-layer structure, including at least 2 second metal sub-layers, preferably at least 5 second metal sub-layers.

9. A method for preparing the composite metal current collector according to any one of claims 1 to 8, characterized in that: The preparation method comprises: first preparing a first metal layer, and then depositing a second metal layer on one side surface of the first metal layer to obtain the composite metal current collector.

10. A battery, characterized in that: The battery comprises the composite metal current collector according to any one of claims 1 to 8.

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