Composite current collector

Abstract

The utility model discloses a composite current collector which comprises a thin film layer and metal conducting layers arranged on the upper side and the lower side of the thin film layer, and the upper end face and the lower end face of the thin film layer are constructed to be of a step-shaped structure so as to be in direct or indirect contact with the metal conducting layers. Compared with a composite current collector of a traditional structure, the composite current collector has the advantages that when the metal conductive layer and the thin film layer are directly or indirectly combined, the contact area of the metal conductive layer and the thin film layer can be increased due to the arrangement of the stepped structure, the binding force between the metal conductive layer and the thin film layer can be enhanced, and the tensile property of the composite current collector is better; meanwhile, due to the existence of the step-shaped structure, the metal conducting layer is thicker, and the improvement of the flow conductivity of the composite current collector is facilitated.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field especially relates to a kind of composite current collector. BACKGROUND

[0002] Composite current collector has "sandwich" structure, middle layer is polymer macromolecule film layer, common material has PP (polypropylene), PET (polyethylene terephthalate) etc., two sides are metal conductive layer, such as copper metal or aluminum metal.For increasing the bonding force of metal conductive layer and film layer, prior art will be often set between film layer and metal conductive layer conductive glue or increase other substance that improves the bonding force of metal conductive layer and film layer;Doing this will improve the cost of composite current collector on the one hand, let composite current collector lose cost advantage compared with traditional current collector, limit the commercial application of composite current collector, on the other hand, the effect of improving the bonding force of metal conductive layer and film layer is also limited, instead, the weight of composite current collector is increased.

[0003] In addition, the middle film layer of current composite current collector, when tab is welded on the edge of composite current collector, due to the existence of middle film layer, when welding, middle film layer will form the mixture of metal and film melt under high temperature, greatly affect the electron of tab welding place, increase the heat generation of battery using composite current collector.

[0004] Thus prior art still needs to be improved and improved. UTILITY MODEL CONTENT

[0005] In view of the deficiencies of the prior art described above, the purpose of the utility model is to provide a kind of composite current collector, to solve at least one problem existing in the composite current collector described in the background art.

[0006] In order to achieve the above purpose, the utility model takes the following technical scheme:

[0007] A kind of composite current collector, including film layer and the metal conductive layer being set on the upper and lower sides of the film layer, the upper and lower end faces of the film layer are configured to have stepped structure, to be directly or indirectly contacted with the metal conductive layer.

[0008] The stepped structure has multiple step faces, and the step faces include a top step face, a bottom step face and multiple intermediate step faces, based on the reference surface of the film layer and along the length direction of the film layer, the two sides of the top step face are sequentially provided with the intermediate step face and the bottom step face, and the height of the top step face, the intermediate step face to the bottom step face gradually decreases.

[0009] The stepped structure is symmetrically distributed in the length direction of the film layer.

[0010] The ratio of the height of the top step surface to the height of the bottom step surface is 3:1 to 6:1 based on the reference surface.

[0011] The width of the top step surface along the length direction of the thin film layer is 10 um-1 cm.

[0012] A filling space is formed at at least one of the top step surface, the middle step surface and the bottom step surface to expose the inside of the thin film layer, and the bottom surface of the filling space is higher than the reference surface.

[0013] The cross section of the filling space taken along a plane parallel to the reference surface is circular, and the diameter of the filling space is 10 nm-100 nm.

[0014] The cross section of the filling space taken along a plane parallel to the reference surface is the same as the shape of the middle step surface.

[0015] An intermediate connecting layer is further arranged between the thin film layer and the metal conductive layer, the material of the intermediate connecting layer is one of aluminum oxide, silicon nitride, nickel alloy, copper alloy and aluminum alloy, and the top step surface is flush with the end surface of the metal conductive layer.

[0016] The height of the bottom step surface is 1 um-1.5 um, and the height of the top step surface is 3 um-6 um.

[0017] Compared with the prior art, the composite current collector provided by the utility model comprises a thin film layer and metal conductive layers arranged on the upper and lower sides of the thin film layer, and the upper and lower end surfaces of the thin film layer are constructed into a stepped structure to be in direct or indirect contact with the metal conductive layers. Compared with the composite current collector with the traditional structure, when the metal conductive layers are directly or indirectly combined with the thin film layer, the stepped structure increases the contact area of the two, is beneficial to enhancing the bonding force between the metal conductive layers and the thin film layer, makes the tensile property of the composite current collector better, and simultaneously, due to the existence of the stepped structure, the metal conductive layers are thicker, which is beneficial to improving the current conducting capacity of the composite current collector. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structure diagram of the thin film layer with the stepped structure in the composite current collector provided by the utility model is shown.

[0019] Figure 2 The structure diagram of the composite current collector of the first embodiment provided by the utility model is shown.

[0020] Figure 3 The structure diagram of the composite current collector of the second embodiment provided by the utility model is shown.

[0021] Figure 4 The structure diagram of the composite current collector of the third embodiment of the utility model.

[0022] Figure 5 The structure diagram of the composite current collector of the fourth embodiment of the utility model.

[0023] Figure 6 The structure diagram of the composite current collector of the third embodiment of the utility model.

[0024] Figure 7 The structure diagram of the composite current collector of the third embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and effect of the utility model more clear and definite, the utility model is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the utility model and should not be used to limit the utility model.

[0026] It should be noted that when a component is referred to as "mounted on", "fixed on" or "provided on" another component, it can be directly on another component or there can be a middle component. When a component is referred to as "connected to" another component, it can be directly connected to another component or there can be a middle component.

[0027] It should also be noted that the left, right, up, down and other orientation terms in the utility model examples are only relative concepts or are referenced to the normal use state of the product, and should not be considered as limiting.

[0028] The composite current collector has a "sandwich" structure, the middle layer is a polymer macromolecular film layer, and common materials include PP (polypropylene), PET (polyethylene terephthalate) and the like, and the two sides are metal conductive layers, such as copper metal or aluminum metal. In order to increase the bonding force of the metal conductive layer and the film layer, the prior art often provides conductive glue between the film layer and the metal conductive layer or increases other substances to improve the bonding force of the metal conductive layer and the film layer; this does not only increase the cost of the composite current collector, which makes the composite current collector lose the cost advantage compared with the traditional current collector, limits the commercial application of the composite current collector, but also has limited effect on improving the bonding force of the metal conductive layer and the film layer, and instead increases the weight of the composite current collector.

[0029] In addition, the current intermediate film layer of the composite current collector, when the tab is welded on the edge of the composite current collector, due to the existence of the intermediate film layer, the intermediate film layer will form a mixture of metal and film melt at high temperature during welding, which greatly affects the electron of the tab welding place, increases the heat generation of the battery using the composite current collector.

[0030] The utility model provides a kind of composite current collector, please refer to Figures 1-7 , including film layer 1 and the metal conductive layer 2 being set to the upper and lower sides of film layer 1, the upper and lower two end surfaces of film layer 1 are configured to have stepped structure, to be directly or indirectly contacted with the metal conductive layer 2.The composite current collector of the present application compared with the composite current collector of traditional structure, when the metal conductive layer 2 is directly or indirectly combined with film layer 1, the stepped structure is arranged to increase the contact area of both, it is advantageous to enhance the bonding force between the metal conductive layer 2 and film layer 1, so that the tensile property of composite current collector is better;At the same time, due to the existence of stepped structure, the metal conductive layer 2 is thicker, which is advantageous to improve the current-carrying capacity of composite current collector.

[0031] Further, the stepped structure has a plurality of step surfaces, the step surfaces include a top step surface 31, a bottom step surface 32 and a plurality of intermediate step surfaces 33, based on a reference surface 10 of the film layer 1 and along a length direction of the film layer 1, both sides of the top step surface 31 are sequentially provided with the intermediate step surfaces 33 and the bottom step surface 32, the height of the top step surface 31, the intermediate step surfaces 33 to the bottom step surface 32 gradually decreases.In the present application, due to the lower height of the two bottom step surfaces 32, the metal conductive layer 2 corresponding to the position of the bottom step surface 32 is thicker after the film layer 1 is combined with the metal layer, which can reduce the internal resistance during tab welding.In the embodiment of the present application, the number of step surfaces is 6-11, that is, the number of top step surfaces 31 is 1, the number of bottom step surfaces 32 is 2 and is located at the outermost side of the step surface respectively, and the rest is intermediate step surface 33, preferably, the number of intermediate step surfaces 33 on both sides of the top step surface 31 is the same, at this time, the tensile strength of the composite current collector is better.It should be noted that the reference surface 10 in the present application is virtual, which is convenient for subsequent definition of the height of the step surface;The structure diagram of the film layer 1 in the present application Figure 1 and the structure diagram of the composite current collector in the present application Figures 2-7 are both up-down symmetrical, Figure 1 The structure diagram of the film layer 1 in the present application Figures 3-7 and the structure diagram of the composite current collector in the present application are both left-right symmetrical, therefore. Part of the corresponding position in the drawing is omitted. Figures 1-7The structure of the structure diagram shown is formed along the length direction and the height direction of the thin film layer 1, wherein the horizontal direction is the length direction of the thin film layer 1, and the vertical direction is the height direction of the thin film layer 1. Figure 1 The middle top step surface 31 is located at the middle position of the thin film layer 1, and the bottom step surface 32 is located at both sides of the thin film layer 1, and the plurality of middle step surfaces 33 are arranged between the top step surface 31 and the bottom step surface 32 along the arrangement direction of the top step surface 31 to the bottom step surface 32.

[0032] In this application, the top step surface 31, the bottom step surface 32 and the plurality of middle step surfaces 33 are arranged along the horizontal direction, the top step surface 31 and the adjacent middle step surface 33, the two adjacent middle step surfaces 33 and the middle step surface 33 and the bottom step surface 32 are provided with a step height surface 35 in the thickness direction of the thin film layer 1 to connect the two adjacent step surfaces, and the step height surface 35 in the embodiment is parallel to the thickness direction of the thin film layer 1, that is, the arrangement direction of the step height surface 35 is perpendicular to the length direction of the thin film layer 1. Further, in order to avoid the stress concentration of the right angle step formed by the step height surface 35 and the step surface, the step height surface 35 can be arranged obliquely, and the inclination angle of the step height surface 35 and the reference surface 10 is 30°-60°, so as to disperse the stress and improve the bending fatigue life; in addition, the obliquely arranged step height surface 35 can better adapt to the processing technology, for example, a small angle is used for high precision laser etching, and a large angle is used for low precision chemical etching.

[0033] In this application, the projection height of the step height surface 35 between the two adjacent step surfaces in the three of the top step surface 31, the bottom step surface 32 and the plurality of middle step surfaces 33 in the height direction of the thin film layer 1 is the same or different, which can be set according to the difference of the thermal expansion coefficient of the metal conductive layer 2 and the thin film layer 1 in the projection height of the step height surface 35 in the height direction of the thin film layer 1, so as to reduce the shear stress under temperature cycle; the top step surface 31 occupies 10%-35% in the length direction of the thin film layer 1, and the width of the top step surface 31 can be beneficial to improve the overall tensile strength. Of course, alternatively, the step height surface 35 can also be transitioned by a smooth arc or an arc chamfer is arranged at the connection between the step surface and the step height surface 35, which is easier to realize in the preparation process and can reduce stress concentration; further, the roughness Ra of the top step surface 31, the middle step surface 33, the bottom step surface 32 and the step height surface 35 is limited to 0.01um-0.2um, so as to ensure the good contact of the metal conductive layer 2 and the thin film layer 1. As shown in Figure 6 The step height surface 35 between the adjacent step surfaces adopts an arc.

[0034] In the first embodiment of the application, please refer to Figure 1 and 2, the top step surface 31 is not in the middle position in the length direction of the film layer 1, that is, in this embodiment, the number of the middle step surfaces 33 between the top step surface 31 and the bottom step surfaces 32 on both sides is different, and the number of the middle step surfaces 33 on one side is more, and the number of the middle step surfaces 33 on the other side is less. In the second embodiment of the present application, please refer to Figure 1 and Figure 3 , the stepped structure is symmetrically distributed up and down and left and right in the length direction of the film layer 1, that is, in this embodiment, the number of the middle step surfaces 33 between the top step surface 31 and the bottom step surfaces 32 on both sides is the same. Compared with the second embodiment, the first embodiment has the disadvantage that when the film layer 1 is stretched along the length direction, the inconsistent number of the middle step surfaces 33 on both sides of the top step surface 31 will affect the tensile strength of the film layer 1, and then affect the tensile strength of the composite current collector; the structure of the second embodiment of the present application is beneficial to balance the electrical properties of the current collector on both sides.

[0035] Further, based on the reference surface 10, the ratio of the height of the top step surface 31 to the height of the bottom step surface 32 is 3:1 to 6:1. Specifically, the height of the bottom step surface 32 is 1um-1.5um, and the height of the top step surface 31 is 3um-6um. By limiting the height of the stepped structure by the above numerical values, it is ensured that the film layer 1 has sufficient mechanical support to resist deformation under external force during charging and discharging, while avoiding the thickness of the film layer 1 being too large to cause the weight of the composite current collector to rise, and reducing the effective space occupied in the battery.

[0036] Further, along the length direction of the film layer 1, the width of the top step surface 31 is 10um-1cm, which balances the electrical and mechanical properties of the current collector, adjusts the flexibility and rigidity of the current collector, ensures that the composite current collector is not easily damaged during battery assembly and use, and improves the overall reliability of the battery.

[0037] Further, a filling space 34 is formed at at least one of the top step surface 31, the middle step surface 33 and the bottom step surface 32 to expose the inside of the thin film layer 1, and the bottom surface of the filling space 34 is higher than the reference surface 10. In the embodiment of the present application, the filling space 34 is formed on at least one of the top step surface 31, the middle step surface 33 and the bottom step surface 32 by etching, laser processing or other methods, and the metal conductive layer 2 is deposited into the filling space 34 by vacuum evaporation, magnetron sputtering or other deposition methods to enhance the bonding force between the thin film layer 1 and the metal conductive layer 2. The filling space 34 provides a new way for optimizing the performance of the composite current collector, and the filling space 34 exposes the inside of the thin film layer 1, fills the metal conductive material, increases the ion transmission channel, and improves the charging and discharging speed and the rate performance of the battery. Meanwhile, the filling space 34 changes the local structure of the current collector, which helps to disperse stress and improve the mechanical properties and stability of the current collector. Of course, alternatively, micro convexes can be arranged on the top step surface 31, the bottom step surface 32 and the middle step surfaces 33 to enhance the bonding force between the thin film layer 1 and the metal conductive layer 2. Specifically, the cross section of the filling space 34 taken along a plane parallel to the reference surface 10 can be circular, polygonal or grid-shaped, etc.

[0038] In the third embodiment of the present application, referring to Figure 1 and Figure 4 , the cross section of the filling space 34 taken along a plane parallel to the reference surface 10 is circular, and the diameter of the filling space 34 is 10 nm-100 nm. In this embodiment, the cylindrical filling space 34 is formed on the stepped structure by removing part of the material on at least one of the top step surface 31, the middle step surface 33 and the bottom step surface 32 by etching, laser processing or other methods, so that the metal conductive layer 2 is deposited and combined with the thin film layer 1. The filling space 34 with the aforementioned diameter can reduce the interface resistance between the filling material and the stepped structure, and improve the ion transmission efficiency.

[0039] In the fourth embodiment of the present application, referring to Figure 1 and Figure 5 , the cross section of the filling space 34 taken along a plane parallel to the reference surface 10 is the same as the shape of the middle step surface 33. In this embodiment, the filling space 34 is formed at the corresponding position of at least one middle step surface 33 between the top step surface 31 and the bottom step surface 32 on both sides, and the depth of the filling space 34 is less than the height difference between the middle step surface 33 and the reference surface 10. The corresponding positions of two adjacent middle step surfaces 33 cannot form spaces at the same time to avoid affecting the flexibility of the composite current collector. The filling space 34 can be filled with the extension of the metal conductive layer 2 or other materials to enhance the bonding force between the metal conductive layer 2 and the thin film layer 1. It should be noted that,Figure 4 and Figure 5 The extension of the metal conductive layer 2 filled in the filling space 34 of the composite current collector can also be filled with other materials that can help to improve the bonding force between the film layer 1 and the metal conductive layer 2 or improve the current conducting capacity according to actual needs.

[0040] Further, referring to Figure 1 and Figure 7 The intermediate connecting layer 4 is arranged between the film layer 1 and the metal conductive layer 2, and the material of the intermediate connecting layer 4 is one of aluminum oxide, silicon nitride, nickel alloy, copper alloy and aluminum alloy. The intermediate connecting layer 4 connects the film layer 1 and the metal conductive layer 2, which is beneficial to improve the bonding force between the metal conductive layer 2 and the stepped structure. The top step surface is flush with the end surface of the metal conductive layer 2, that is, the metal conductive layer 2 is not deposited on the top step surface. Therefore, when the composite current collector is cut, the cutter can cut the stepped structure of the film layer 1 along the top step surface. The advantage is that the metal conductive layer 2 is not damaged when the film layer 1 is cut, so that the edge of the cut composite current collector is not curled, and the flatness of the composite current collector is ensured. It should be noted that the upper and lower end surfaces of the film layer 1 in the composite current collector are both configured as a stepped structure, that is, the composite current collector has an upper-lower symmetrical structure along the reference surface 10, so that the metal conductive layer 2 is not affected when the composite current collector is cut. Of course, the intermediate connecting layer 4 arranged between the film layer 1 and the metal conductive layer 2 is also a foreseeable modification based on the first embodiment, the second embodiment, the third embodiment and the fourth embodiment, which will not be described herein. The adaptive combination based on the structure in the present application also belongs to the protection scope of the present application.

[0041] The present application also provides a preparation method of the composite current collector, which comprises the following steps:

[0042] The end surface of the film layer 1 is configured as a stepped structure by etching;

[0043] The metal conductive layer 2 is plated on the stepped structure of the film layer 1.

[0044] The preparation method of the composite current collector comprises the following steps:

[0045] Step 1, cleaning the surface of the film layer 1 to remove impurities on the surface of the film layer 1;

[0046] Step 2, immersing the film layer 1 to be etched in a chemical solution, or applying a chemical reagent on the film layer 1 by spraying or brushing;

[0047] Step 3, the end surface of the thin film layer 1 is configured to have a stepped structure by etching, and the etching time and temperature are controlled;

[0048] Step 4, the thin film layer 1 is cleaned by deionized water to remove residual chemical impurities;

[0049] Step 5, the thin film layer 1 is dried at 60-100 DEG C;

[0050] Step 6, a metal conductive layer 2 is plated on the stepped structure of the thin film layer 1;

[0051] Step 7, a metal copper layer is plated on the outer side of the metal conductive layer 2; the stepped structure can be constructed on the thin film layer 1 by the above method, and the metal conductive layer 2 and the metal copper layer can be plated on the stepped structure of the thin film layer 1.

[0052] In the preparation method of the composite current collector, the material of the thin film layer 1 can be PP film or PET film, the PP film is made of polypropylene, and the PET film is made of polyethylene terephthalate; the metal conductive layer 2 can be selected from aluminum oxide or a material similar to aluminum oxide; the metal conductive layer 2 can be plated on the stepped structure of the thin film layer 1 by vacuum evaporation or magnetron sputtering, and the metal copper layer can also be plated on the metal conductive layer 2 by vacuum evaporation or magnetron sputtering; preferably, the metal conductive layer 2 is plated on the stepped structure of the thin film layer 1 by vacuum evaporation, and the metal copper layer is deposited on the metal conductive layer 2 by magnetron sputtering, which has the advantage that the energy of magnetron sputtering is high, and the aluminum oxide layer can be firmly fixed on the thin film layer 1, thereby improving the bonding force between the two.

[0053] In summary, the composite current collector provided by the present application comprises a thin film layer and a metal conductive layer arranged on the upper and lower sides of the thin film layer, and the upper and lower end surfaces of the thin film layer are configured to have a stepped structure to directly or indirectly contact the metal conductive layer. Compared with the traditional structure of the composite current collector, when the metal conductive layer is directly or indirectly combined with the thin film layer, the stepped structure increases the contact area between the two, which is beneficial to enhancing the bonding force between the metal conductive layer and the thin film layer, so that the tensile property of the composite current collector is better; at the same time, due to the existence of the stepped structure, the metal conductive layer is thicker, which is beneficial to improving the current conducting capacity of the composite current collector

[0054] It can be understood that, for those skilled in the art, equivalent replacement or change can be made according to the technical scheme and the utility model concept of the present application, and all these changes or replacements shall belong to the protection scope of the claims attached to the present application.

Claims

1. A composite current collector, characterized by, The thin film layer and the metal conductive layer are in direct or indirect contact.

2. The composite current collector of claim 1, wherein The stepped structure has a plurality of step surfaces, including a top step surface, a bottom step surface, and a plurality of intermediate step surfaces, both sides of the top step surface are sequentially provided with the intermediate step surfaces and the bottom step surface along the length direction of the thin film layer based on the reference surface of the thin film layer, and the height of the top step surface, the intermediate step surfaces, and the bottom step surface gradually decreases.

3. The composite current collector of claim 2, wherein, The stepped structure is symmetrically distributed along the length direction of the thin film layer.

4. The composite current collector of claim 3, wherein, The ratio of the height of the top step surface to the height of the bottom step surface is 3:1 to 6:1 based on the reference surface.

5. The composite current collector of claim 4, wherein, The width of the top step surface is 10 um to 1 cm along the length direction of the thin film layer.

6. The composite current collector of any one of claims 2-5, wherein, A filling space is formed at at least one of the top step surface, the intermediate step surface, and the bottom step surface to expose the inside of the thin film layer, and the bottom surface of the filling space is higher than the reference surface.

7. The composite current collector of claim 6, wherein, The cross section of the filling space taken along a plane parallel to the reference surface is circular, and the diameter of the filling space is 10 nm to 100 nm.

8. The composite current collector of claim 6, wherein, The cross section of the filling space taken along a plane parallel to the reference surface is the same as the shape of the intermediate step surface.

9. The composite current collector of claim 2, wherein, An intermediate connecting layer is further arranged between the thin film layer and the metal conductive layer, the material of the intermediate connecting layer is one of aluminum oxide, silicon nitride, nickel alloy, copper alloy, and aluminum alloy, and the top step surface is flush with the end surface of the metal conductive layer.

10. The composite current collector of claim 4, wherein The height of the bottom step surface is 1 um to 1.5 um, and the height of the top step surface is 3 um to 6 um.

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