Composite foil, pole piece and battery

Abstract

The utility model provides a composite foil, a pole piece and a battery, and relates to the technical field of batteries. The composite foil comprises a supporting layer, a first metal layer and a second metal layer. The support layer has a membrane region and a non-membrane region. The first metal layers are arranged on the two sides of the film area in the thickness direction. The second metal layers are arranged on the two sides of the non-film area in the thickness direction. An average thickness of the second metal layer is greater than a thickness of the first metal layer. The pole piece provided by the utility model adopts the composite foil; the battery provided by the utility model adopts the pole piece. According to the composite foil, the pole piece and the battery provided by the utility model, the technical problem that high-rate charging and discharging are difficult to adapt due to poor overcurrent capability in the prior art can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a composite foil material, a pole piece and a battery. Background Art

[0002] New energy lithium-ion batteries are mainly composed of four main materials: positive electrode materials, negative electrode materials, electrolytes and diaphragms, as well as auxiliary materials such as copper foil, aluminum foil, conductive agents, binders, and structural parts. The current collector (copper / aluminum foil) is the electronic conductor between the positive and negative electrodes and the external circuit. Its function is to collect and output the current generated by the positive and negative active materials or input the electrode current to the active materials.

[0003] Usually, lithium-ion batteries use aluminum foil with a high oxidation potential for the positive electrode, and copper foil that is not easy to form an alloy with lithium for the negative electrode. Currently, with the development of foil technology, composite copper foil has received a lot of attention. Compared with pure copper / aluminum foil, composite copper foil can reduce the cost of foil and the weight of the battery, and improve the energy density of the power battery. In particular, the special structure of the composite can effectively control the puncture problem (for example, the current composite copper foil is a sandwich structure, the middle layer is PET film or PP film, and the upper and lower surfaces are copper layers with a thickness of about 1 micron), alleviate the battery explosion and fire caused by internal lithium dendrites or external punctures, etc., "only smoke but no fire", and greatly improve the safety performance of the battery.

[0004] However, since the thickness of the metal layer of the composite foil is relatively small, usually around 1um, its current carrying capacity is limited. Resistance R = (conductivity σ*transmission distance b) / cross-sectional area A. According to the calculation principle, the thickness of the single-layer tab metal coating D*tab width y is the cross-sectional area A. When the tab width y is fixed, the smaller the D value, the smaller A will be, so R will increase, resulting in limited current carrying capacity. Although usually at low rates, the difference in charge and discharge performance between traditional foil and composite foil is not obvious. However, at high rate charge and discharge, the electrochemical performance of batteries using thin-coated composite foil will decline. Utility Model Content

[0005] The technical problem solved by the utility model is how to improve the technical problem that the existing technology has poor current capacity and is difficult to adapt to high rate charging and discharging.

[0006] The embodiments of the present invention can be implemented as follows:

[0007] The embodiment of the utility model provides a composite foil material, comprising:

[0008] A support layer having a connected membrane area and a non-membrane area;

[0009] A first metal layer is disposed on both sides of the film region in a thickness direction;

[0010] A second metal layer is disposed on both sides of the non-film region in a thickness direction;

[0011] Wherein, the average thickness of the second metal layer is greater than the thickness of the first metal layer.

[0012] Optionally, a ratio of a maximum thickness of the second metal layer to a maximum thickness of the first metal layer is greater than 1 and less than or equal to 2.

[0013] Optionally, the first metal layer is a copper plating layer, and the thickness of the first metal layer ranges from 0.5 μm to 2.5 μm;

[0014] Alternatively, the first metal layer is an aluminum plating layer, and the thickness of the first metal layer ranges from 3 μm to 4 μm.

[0015] Optionally, the thickness of the second metal layer gradually decreases from a side close to the first metal layer to a side far away from the first metal layer.

[0016] Optionally, the side surface away from the non-film area is in a concave arc shape, or the side surface of the second metal layer away from the non-film area is in an inclined plane.

[0017] Optionally, the thickness of the second metal layer is equal everywhere.

[0018] Optionally, the thickness of the non-membrane region is smaller than the thickness of the membrane region.

[0019] Optionally, the width of the first metal layer ranges from 50 mm to 250 mm, and the ratio of the width of the first metal layer to the width of the second metal layer ranges from 2.5 to 50.

[0020] A pole piece comprises the above-mentioned composite foil material.

[0021] A battery comprises the above-mentioned pole piece.

[0022] The composite foil, pole piece and battery provided by the utility model have the following beneficial effects compared with the prior art:

[0023] In the composite foil, the film area in the support layer is used to form the main part of the pole piece, and the non-membrane area near the edge area is used to form the pole ear in the pole piece. Among them, since the thickness of the second metal layer on the non-membrane area is greater than the thickness of the first metal layer, the cross-sectional area through which the electron flow passes can be increased, the internal resistance of the foil and the temperature rise of the battery can be reduced, thereby reducing the ohmic impedance of the battery and the polarization of the battery, which is conducive to rapid charging and discharging of the battery, and can be suitable for high-rate charging and discharging. Based on this, the composite foil provided by the utility model and the pole piece and battery using the composite foil can improve the technical problem in the prior art that the poor current capacity makes it difficult to adapt to high-rate charging and discharging. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the utility model and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a schematic structural diagram of a composite foil provided in the first embodiment of the present application;

[0026] Figure 2 This is a schematic structural diagram of another composite foil material provided in the first embodiment of the present application;

[0027] Figure 3 This is a schematic cross-sectional structure diagram of a composite foil material provided in the first embodiment of the present application;

[0028] Figure 4 This is a schematic cross-sectional structure diagram of another composite foil material provided in the first embodiment of the present application;

[0029] Figure 5 This is a schematic cross-sectional structure diagram of another composite foil material provided in the first embodiment of the present application;

[0030] Figure 6 This is a schematic cross-sectional structure diagram of another composite foil material provided in the first embodiment of the present application.

[0031] Icon: 10-composite foil; 100-support layer; 110-membrane area; 111-first metal layer; 120-non-membrane area; 121-second metal layer; 200-active coating. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0035] In the description of the present utility model, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the utility model product is usually placed when used. It is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present utility model.

[0036] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0037] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0038] First embodiment

[0039] See also Figure 1 This embodiment provides a composite foil 10, which is used to make a pole piece, and the composite foil 10 can improve the technical problem in the prior art that the poor current capacity makes it difficult to adapt to high-rate charge and discharge.

[0040] In this embodiment, the composite foil 10 includes a support layer 100, a first metal layer 111 and a second metal layer 121. The support layer 100 has a film region 110 and a non-film region 120, such as Figure 1 and Figure 2 The support layer 100 can be regarded as a base film, which can be made of PET film or PP film. It is worth noting that Figure 1 The composite foil 10 shown in Figure 2 The difference between the composite foil 10 shown in FIG. 1 and FIG. 2 is that the structure of the non-film area 120 is different. After the composite foil 10 is made into a pole piece, the film area 110 forms the main part of the pole piece, and the non-film area 120 forms the pole ear part. Figure 3 The first metal layer 111 is disposed on both sides of the film region 110 in the thickness direction. The second metal layer 121 is disposed on both sides of the non-film region 120 in the thickness direction. The average thickness of the second metal layer 121 is greater than the thickness of the first metal layer 111.

[0041] As described above, in the composite foil 10, since the thickness of the second metal layer 121 on the non-film region 120 is greater than the thickness of the first metal layer 111, the cross-sectional area through which the electron flow passes can be increased, the internal resistance of the foil and the temperature rise of the battery can be reduced, thereby reducing the battery ohmic impedance and battery polarization, which is conducive to rapid battery charging and discharging, and can be suitable for high-rate charging and discharging. Based on this, the composite foil 10 provided in this embodiment can improve the technical problem of poor current capacity in the prior art that makes it difficult to adapt to high-rate charging and discharging.

[0042] exist Figure 3 In , a represents the thickness of the active coating 200, b represents the thickness of the first metal layer 111, and c represents the thickness of the support layer 100. When the thicknesses of the membrane region 110 and the non-membrane region 120 are the same, c can also represent the thickness of the membrane region 110 and the thickness of the non-membrane region 120 at the same time; d represents the thickness of the second metal layer 121. Figure 1 In FIG. 1 , e represents the width of the film area 110 , f represents the width of the non-film area 120 , and g represents the plating length of the non-film area 120 .

[0043] Generally, in this embodiment, the first metal layer 111 is disposed on both sides of the film region 110 in the thickness direction by plating, and the second metal layer 121 is disposed on both sides of the non-film region 120 by plating.

[0044] It is worth noting that in this embodiment, the thickness of the second metal layer 121 may be uneven, that is, the second metal layer 121 may be thicker in some areas and relatively thinner in some areas, such as Figure 4 Based on this, in some cases, the thickness of a portion of the second metal layer 121 is less than or equal to the thickness of the first metal layer 111. In addition, in this embodiment, the first metal layer 111 is plated on both sides of the film region 110 in a uniform thickness direction.

[0045] In addition, in this embodiment, the first metal layer 111 and the second metal layer 121 are made of copper, aluminum, gold or silver, etc., and the resistivity is less than 6*10 -8 Ω*m metal material.

[0046] Optionally, in this embodiment, the ratio of the maximum thickness of the second metal layer 121 to the maximum thickness of the first metal layer 111 is greater than 1 and less than or equal to 2. On the one hand, the thickness of the second metal layer 121 is greater than the thickness of the first metal layer 111; on the other hand, the problem of the second metal layer 121 being too thick and affecting the overall quality of the pole piece, resulting in a reduction in energy density, can also be avoided.

[0047] In some implementations of this embodiment, when the composite foil 10 is used to make a pole piece for a negative electrode, the first metal layer 111 is a copper plating layer, and the thickness of the first metal layer 111 ranges from 0.5 μm to 2.5 μm. For example, the thickness of the first metal layer 111 can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm or 2.5 μm, etc.

[0048] In other implementations of this embodiment, when the composite foil 10 is used to make a pole piece for a positive electrode, the first metal layer 111 is an aluminum plating layer, and the thickness of the first metal layer 111 ranges from 3 μm to 4 μm. For example, the thickness of the first metal layer 111 can be 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm or 4 μm, etc.

[0049] Compared with the foil in the prior art, the composite foil 10 provided in this embodiment can be regarded as thickening the thickness of the second metal layer 121, so that the average thickness of the second metal layer 121 is greater than the thickness of the first metal layer 111; however, in this embodiment, the method of thickening the thickness of the second metal layer 121 can be presented in different ways according to actual needs. For example, in some embodiments, the thickness of the second metal layer 121 gradually decreases from the side close to the first metal layer 111 to the side away from the first metal layer 111. In this case, the side of the second metal layer 121 away from the non-film area 120 can be an inclined plane, such as Figure 4 The side of the second metal layer 121 away from the non-film area 120 may also be an arc-shaped surface, such as Figure 5 For example, in some other embodiments, the thickness of the second metal layer 121 can be set to be uniform, that is, the thickness of the second metal layer 121 is equal everywhere. In this case, the side of the second metal layer 121 away from the non-film area 120 is parallel to the plane of the non-film area 120, such as Figure 3 .

[0050] It is worth noting that when the thickness of the second metal layer 121 gradually decreases from the side close to the first metal layer 111 to the side far from the first metal layer 111, the average thickness of the second metal layer 121 is greater than the thickness of the first metal layer 111. Based on this, the thickness of the second metal layer 121 can be substantially thickened relative to the prior art, effectively increasing the overall thickness of the second metal layer 121, achieving an increase in the cross-sectional area through which electrons flow, reducing the internal resistance of the foil and the temperature rise of the battery, thereby reducing the ohmic impedance of the battery and the polarization of the battery, which is conducive to rapid charging and discharging of the battery, and can be applied to high-rate charging and discharging.

[0051] Optionally, in this embodiment, the width of the first metal layer 111 ranges from 50 mm to 250 mm. At the same time, the ratio of the width of the first metal layer 111 to the width of the second metal layer 121 ranges from 2.5 to 50. This allows different coating areas to be clearly distinguished. Generally, the width of the film area 110 is much larger than the width of the non-film area 120.

[0052] In this embodiment, the first metal layer 111 includes a first conductive thin layer and a first water electroplating layer; the first conductive thin layer is plated on the film area 110, and the first water electroplating layer is plated on the first conductive thin layer; the thickness of the first conductive thin layer ranges from 2nm to 75nm. The first conductive thin layer is provided on the base film by magnetron sputtering, and the thickness is 2nm to 75nm; on this basis, the thickness of the first metal layer 111 is thickened to a specified thickness by water electroplating on the first conductive thin layer.

[0053] In addition, in this embodiment, the second metal layer 121 includes a second conductive thin layer, a second water-plated layer and a vapor-deposited layer; the second conductive thin layer is plated on the non-membrane area 120, the second water-plated layer is plated on the second conductive thin layer, and the vapor-deposited layer is plated on the second water-plated layer; the thickness of the second conductive thin layer ranges from 2nm to 75nm. The second conductive thin layer is provided on the base film by magnetron sputtering, and the thickness is 2nm to 75nm; on this basis, the thickness of the second metal layer 121 is thickened to the same thickness as the first metal layer 111 by water-plating on the second conductive thin layer; finally, the vapor-deposited layer is provided on the second water-plated layer by vacuum evaporation to thicken the second metal layer 121 to a specified thickness.

[0054] It is worth noting that in order to reduce the difficulty of the process, the first conductive thin layer and the second conductive thin layer are integrally formed; the first water-plated layer and the second water-plated layer are integrally formed. That is to say, in the process of making the composite foil 10, the first conductive thin layer and the second conductive thin layer can be plated on the support layer 100 by magnetron sputtering, and the thickness of the first conductive thin layer and the second conductive thin layer is 2nm-75nm; then the first water-plated layer and the second water-plated layer are plated on the first conductive thin layer and the second conductive thin layer by water plating, and the thickness of the first metal layer 111 reaches the specified thickness; finally, the evaporated layer is plated on the non-membrane area 120 by vacuum evaporation, so that the thickness of the second metal layer 121 reaches the specified thickness, and the manufacturing and forming of the composite foil 10 can be completed.

[0055] In this embodiment, the thickness of the membrane region 110 and the thickness of the non-membrane region 120 in the support layer 100 can be adjusted appropriately. For example, in some embodiments, the thickness of the non-membrane region 120 is less than the thickness of the membrane region 110, such as Figure 6 , space can be saved for increasing the thickness of the second metal layer 121 to meet different requirements. Of course, in other embodiments, such as Figure 3 , the thickness of the membrane area 110 may also be set to be equal to the thickness of the non-membrane area 120 to reduce the difficulty of the manufacturing process.

[0056] Furthermore, in this embodiment, the surface of the first metal layer 111 away from the support layer 100 is also coated with an active coating 200, and the width of the active coating 200 is less than or equal to the width of the first metal layer 111, thereby ensuring that the coating area is located on the first metal layer 111, and preferably, the width of the active coating 200 is equal to the width of the first metal layer 111. Generally, when the composite foil 10 is applied to the positive electrode sheet, the coated active coating 200 can be a nickel-cobalt-manganese ternary system, a lithium iron phosphate system, a layered oxide system or a polyanion system, etc.; in addition, when the composite foil 10 is applied to the negative electrode sheet, the active coating 200 in the figure can be a graphite system, a hard carbon system or a silicon-carbon system, etc.

[0057] Based on the composite foil 10 provided above, when the composite foil 10 is used in the pole piece to make a battery cell, the weld width is p1*f, and the weld wire length is p2*g, wherein p1 and p2 represent the proportion coefficients of the length and width of the pole ear corresponding to the weld width and the weld wire length, respectively; in addition, the number of layers of the composite foil 10 is w layers, and the number of battery cells is n, then the calculation formula for the actual minimum controlled flow area is as follows:

[0058] S = (p1*f+p2*g)*2*d*2*w*n;

[0059] Wherein, S represents the flow area, f represents the width of the non-film area 120 , g represents the plating length of the non-film area 120 , and d represents the thickness of the second metal layer 121 .

[0060] It can be seen that d is positively correlated with S. The larger d is, the larger S is. The larger S is, the stronger the current carrying capacity is. Based on this, in this embodiment, the method of thickening the second metal layer 121 can achieve the purpose of improving the current carrying capacity.

[0061] In addition, this embodiment also provides a performance comparison table of a battery using existing foil materials and a battery using the composite foil material 10 in this embodiment, as follows:

[0062]

[0063]

[0064] It can be seen from the above table that within the 1C-5C rate, compared with the battery using the existing foil material, the battery using the composite foil material 10 in this embodiment has a lower improvement effect, but does have a higher charging ratio; however, at a higher rate, it can be seen that the charging ratio of the battery using the composite foil material 10 in this embodiment has a greater improvement. At the same time, the temperature rise of the battery using the composite foil material 10 in this embodiment is lower.

[0065] In addition, when the battery is subjected to discharge tests at different temperatures, although the capacity retention is not much different in a high temperature environment due to more active electron movement; however, in a low temperature environment, the capacity of Examples 1-3 is better maintained.

[0066] In summary, in the composite foil 10 provided in this embodiment, since the thickness of the second metal layer 121 on the non-film area 120 is greater than the thickness of the first metal layer 111, the cross-sectional area through which the electron flow passes can be increased, the internal resistance of the foil and the temperature rise of the battery can be reduced, thereby reducing the ohmic impedance of the battery and the polarization of the battery, which is conducive to rapid charging and discharging of the battery, and can be suitable for high-rate charging and discharging. Based on this, the composite foil 10 provided in this embodiment can improve the technical problem of poor current capacity in the prior art that makes it difficult to adapt to high-rate charging and discharging.

[0067] Second embodiment

[0068] The present embodiment provides a pole piece (not shown), and the pole piece in the present embodiment adopts the composite foil 10 in the first embodiment to improve the technical problem in the prior art that the poor current capacity makes it difficult to adapt to high-rate charge and discharge.

[0069] Third embodiment

[0070] In this embodiment, a battery (not shown) is provided, which adopts the electrode in the second embodiment. Therefore, it can be regarded as that the battery in this embodiment adopts the composite foil 10 in the first embodiment, thereby enabling the battery to improve the technical problem in the prior art that the poor current capacity makes it difficult to adapt to high-rate charge and discharge.

[0071] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the utility model should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A composite foil, characterized in that: include: A support layer (100) having a membrane region (110) and a non-membrane region (120) connected to each other; A first metal layer (111) is disposed on both sides of the film region (110) in a thickness direction; A second metal layer (121) is disposed on both sides of the non-film region (120) in a thickness direction; Wherein, the average thickness of the second metal layer (121) is greater than the thickness of the first metal layer (111).

2. The composite foil according to claim 1, characterized in that: The ratio of the maximum thickness of the second metal layer (121) to the maximum thickness of the first metal layer (111) is greater than 1 and less than or equal to 2.

3. The composite foil according to claim 1, characterized in that: The first metal layer (111) is a copper plating layer, and the thickness of the first metal layer (111) ranges from 0.5 μm to 2.5 μm; Alternatively, the first metal layer (111) is an aluminum coating, and the thickness of the first metal layer (111) is in the range of 3 μm to 4 μm.

4. The composite foil according to claim 1, characterized in that: The thickness of the second metal layer (121) gradually decreases from a side close to the first metal layer (111) to a side far from the first metal layer (111).

5. The composite foil according to claim 4, characterized in that: The side surface of the second metal layer (121) away from the non-membrane area (120) is in a concave arc shape, or the side surface of the second metal layer (121) away from the non-membrane area (120) is in an inclined plane.

6. The composite foil according to claim 1, characterized in that: The thickness of the second metal layer (121) is uniform everywhere.

7. The composite foil according to claim 1, characterized in that: The thickness of the non-membrane region (120) is smaller than the thickness of the membrane region (110).

8. The composite foil according to claim 1, characterized in that: The width of the first metal layer (111) is in the range of 50 mm to 250 mm, and the ratio of the width of the first metal layer (111) to the width of the second metal layer (121) is in the range of 2.5 to 50.

9. A pole piece, characterized in that: The composite foil (10) comprises the composite foil (10) as claimed in any one of claims 1 to 8.

10. A battery, characterized in that: Comprising the pole piece as claimed in claim 9.

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