Conductive film, method for preparing conductive film and lithium ion battery

Abstract

The invention discloses a conductive film, a method for preparing the conductive film and a lithium ion battery, and relates to the technical field of conductive film preparation. The preparation method comprises the following steps: S10, after selecting a support layer, respectively coating the upper and lower surfaces of the support layer with a first metal layer; S20, composite a first film on the surface of one of the first metal layers, and composite a second film on the surface of the other first metal layer; S30, composite a third film on the surfaces of the first film and the second film using a film composite technology, and etch a plurality of penetrating circular holes on the third film and the second film; S40, coating the outer surface of the third film and the inner wall of the circular hole with a second metal layer; S50, preparing the composite film; S60, coating the third metal layer on the upper and lower surfaces of the composite film using a vacuum coating technology, and obtaining the conductive film after rolling. The invention has the beneficial effects of preventing the battery from overheating and burning, and improving the conductivity and tensile strength of the conductive film.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film manufacturing, and more specifically, to a conductive film, a method for preparing the conductive film and a lithium ion battery. Background Art

[0002] Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive and negative electrodes to work. Due to the call of the country and the reality of global climate change, lithium-ion batteries are becoming more and more popular as a clean energy.

[0003] People's current focus on lithium-ion batteries is mainly on their energy density and safety performance, which are related to the promotion and application prospects of lithium-ion batteries. In terms of safety, the main reason for the heating and even combustion and explosion of lithium-ion batteries in actual use is "thermal runaway". "Thermal runaway" is a phenomenon in which the heat inside the battery continues to increase and cannot be stopped due to some reason. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a conductive film, a method for preparing the conductive film and a lithium ion battery, which can prevent the battery from overheating and burning, and improve the conductivity and tensile strength of the conductive film.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a conductive film, the improvement of which is that the preparation method comprises the following steps:

[0006] S10, after selecting a support layer, coating the first metal layer on the upper and lower surfaces of the support layer respectively;

[0007] S20, compounding a first thin film on the surface of one of the first metal layers, and compounding a second thin film on the surface of the other first metal layer;

[0008] S30, compounding a third film on the surfaces of the first film and the second film by using a thin film compounding technology, etching a plurality of penetrating circular holes on the third film and the second film and on another third film and the first film respectively, the depth of the circular holes on the third film and the second film is equal to the sum of the thicknesses of the third film and the second film, and the depth of the circular holes on another third film and the first film is equal to the sum of the thicknesses of another third film and the first film;

[0009] S40, using vacuum coating technology to coat the second metal layer on the outer surfaces of the two third films and the inner wall of the circular hole;

[0010] S50, peeling the third film from the second film and peeling another third film from the first film, while retaining the second metal layer plated on the inner wall of the circular hole of the second film and the first film;

[0011] The circular hole is filled with a flame retardant, and a layer of modified paraffin wax is filled on the flame retardant to seal it;

[0012] Alternatively, the circular hole is filled with a flame retardant, a layer of modified paraffin is filled on the flame retardant, and the flame retardant is filled on the basis of the modified paraffin, and then the modified paraffin is used for sealing;

[0013] A composite film is obtained;

[0014] S60, using vacuum coating technology to coat the upper and lower surfaces of the composite film with a third metal layer, and rolling to obtain a conductive film;

[0015] The first metal layer and the third metal layer are 200-300 nm copper layers or aluminum layers, and the second metal layer is 20-100 nm lithium layer.

[0016] Furthermore, a first metal layer is plated on the surface of the first supporting layer using a vacuum coating device, wherein the vacuum coating device includes a magnetron sputtering device or a vacuum evaporation device.

[0017] Furthermore, a coating composite device is used to realize the composite of the first film and the second film.

[0018] Furthermore, the diameter of the circular holes is 500-600 nm.

[0019] Furthermore, after a second metal layer is plated on the outer surface of the third film and in the circular hole, an etching technique is used to remove the metal layer at the center of the circular hole, leaving a metal layer on the inner wall of the circular hole.

[0020] Furthermore, the flame retardant is trimethyl phosphate.

[0021] Furthermore, the modified paraffin wax comprises 6-7 parts of paraffin wax, 0.5-1 parts of lithium chloride, 0.5-3 parts of conductive graphite and 1-3 parts of n-dodecanoic acid, and the softening point of the modified paraffin wax is 65-80°C.

[0022] The present invention also provides a conductive film, the improvement of which is that the conductive film is prepared by the above-mentioned method for preparing a conductive film, and the conductive film comprises a support layer, a first metal layer, a first film, a second film and a third metal layer;

[0023] The upper surface and the lower surface of the support layer are both plated with a first metal layer, and the first film and the second film are respectively composited on the surfaces of the two first metal layers;

[0024] The first film and the second film are provided with a plurality of penetrating circular holes, and the inner walls of the circular holes are plated with a second metal layer with a circular cross section, and the hole in the center of the second metal layer is filled with a flame retardant layer;

[0025] The outer surface of the first film and the outer surface of the second film are both plated with a third metal layer.

[0026] In the above structure, the flame retardant layer includes a flame retardant filled in the hole at the center of the second metal layer and a modified paraffin filled outside the flame retardant, and the flame retardant is trimethyl phosphate.

[0027] In the above structure, the flame retardant layer includes a first flame retardant filled inside the hole in the center of the second metal layer, a first modified paraffin filled outside the first flame retardant, a second flame retardant filled outside the first modified paraffin, and a second modified paraffin filled outside the second flame retardant, and the first flame retardant and the second flame retardant are trimethyl phosphate.

[0028] On the other hand, the present invention further provides a lithium ion battery, the improvement of which lies in that it comprises a conductive film, and the conductive film is prepared by any of the above-mentioned methods for preparing a conductive film.

[0029] The beneficial effect of the present invention is that by placing a flame retardant sealed by modified paraffin in the circular holes of the second film, when the temperature reaches the softening point of the modified paraffin, the paraffin melts from the holes and the flame retardant is released from the holes, which can prevent the battery from burning due to excessive temperature. The second metal layer is a lithium layer, and after the flame retardant is released, the energy density of the battery can also be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a schematic flow chart of a method for preparing a conductive film according to the present invention.

[0031] Figure 2 It is a schematic structural diagram of step S10 of a method for preparing a conductive film of the present invention.

[0032] Figure 3 It is a schematic structural diagram of step S20 of a method for preparing a conductive film of the present invention.

[0033] Figure 4 It is a schematic structural diagram of step S30 of a method for preparing a conductive film of the present invention.

[0034] Figure 5 It is a schematic structural diagram of step S40 of a method for preparing a conductive film of the present invention.

[0035] Figure 6It is a diagram of a first embodiment of step S50 of a method for preparing a conductive film of the present invention.

[0036] Figure 7 It is a diagram of a first embodiment of step S60 of a method for preparing a conductive film of the present invention.

[0037] Figure 8 It is a diagram of a second embodiment of step S50 of a method for preparing a conductive film of the present invention.

[0038] Fig. 9 It is a diagram of a second embodiment of step S60 of a method for preparing a conductive film of the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0040] The following will clearly and completely describe the concept, specific structure and technical effects of the present invention in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention. In addition, all the connection / connection relationships involved in the patent do not refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features in the invention can be combined interchangeably without conflicting with each other.

[0041] Example 1

[0042] Reference Figure 1 As shown, the present invention discloses a method for preparing a conductive film. In this embodiment, the preparation method includes the following steps:

[0043] S10, after selecting the support layer 20, the first metal layer 101 is plated on the upper and lower surfaces of the support layer 10, wherein the support layer 10 is a PET film, and the structure formed is as follows Figure 2 As shown;

[0044] In this embodiment, a first metal layer 101 is plated on the surface of the first support layer 10 by using a vacuum coating device, and the vacuum coating device includes a magnetron sputtering device or a vacuum evaporation device; the first metal layer 101 is a copper layer with a thickness of 200 nm;

[0045] The main function of the first metal layer 101 is to increase the conductivity and the elongation at break of the entire conductive film. In this embodiment, the vacuum coating device is a magnetron sputtering device, and the vacuum degree of the magnetron sputtering is 0.1×10-3Pa-1.0×10-3Pa. The magnetron sputtering argon gas is used as the sputtering gas with a flow rate of 50-60ml / min. Such pressure and speed can speed up the process and improve production efficiency.

[0046] S20, compounding a first film 201 on the surface of one of the first metal layers 101, and compounding a second film 202 on the surface of another first metal layer 101; in this embodiment, Figure 3 As shown, the second film 202 is compounded on the surface of the first metal layer 101 located at the top, and the first film 201 is compounded on the surface of the first metal layer 101 located at the bottom; and the first film 201 and the second film 202 are compounded by using a coating compounding device.

[0047] S30, using thin film composite technology to composite a third film 203 on the surface of the first film 201 and the second film 202, etching a plurality of penetrating circular holes 204 on the third film 203 and the second film 202, the depth of the circular holes 204 being equal to the sum of the thickness of the second film 202 and the third film 203; at the same time, etching a plurality of penetrating circular holes 204 on another third film 203 and the first film 201, the depth of the circular holes 204 being equal to the sum of the thickness of the other third film 203 and the first film 201; refer to Figure 4 , which is a schematic diagram of a structure in which a plurality of circular holes 204 are etched on the third film 203, the second film 202 and the first film 201, and the diameter of the circular hole 204 is 500 nm;

[0048] S40, using vacuum coating technology, coating the second metal layer 102 on the outer surface of the third film 203 and the inner wall of the circular hole 204; Figure 5 As shown, at this time, the inner wall of the circular hole 204 is plated with the second metal layer 102, but the second metal layer 102 does not completely seal the circular hole 204, so a plurality of blind holes are formed on the second metal layer 102;

[0049] S50, peeling the third film 203 from the second film 202, while retaining the second metal layer 102 plated on the inner wall of the circular hole 204 of the second film 202; peeling another third film 203 from the first film 201, while retaining the second metal layer plated on the inside of the circular hole 204 of the first film 201; and the second metal layer 102 is a lithium layer of 100nm;

[0050] In this embodiment, Figure 6As shown, a flame retardant 301 is filled in the blind hole, and a layer of modified paraffin 302 is filled on the flame retardant 301 for sealing; the flame retardant 301 is trimethyl phosphate; and the modified paraffin 302 comprises 6 parts of paraffin, 0.5 parts of lithium chloride, 0.5 parts of conductive graphite and 1 part of n-dodecanoic acid; generally, paraffin begins to soften at 50-60°C, and in this embodiment, the modified paraffin 302 can increase the softening point of paraffin to 65-80°C, thereby improving its temperature resistance;

[0051] S60, using vacuum coating technology, coating the third metal layer 103 on the upper and lower surfaces of the composite film, and rolling to obtain a conductive film, the structure of which is as follows: Figure 7 As shown; and, the third metal layer 103 is a 200nm copper layer.

[0052] Combination Figure 7 As shown, the present invention also provides a conductive film, including a support layer 10, a first metal layer 101, a first film 201, a second film 202 and a third metal layer 103; the support layer 10 is a PET film, the upper surface and the lower surface of the support layer 10 are plated with the first metal layer 101, the first metal layer 101 is a copper layer with a thickness of 200nm, the first film 201 and the second film 202 are respectively compounded on the surfaces of the two first metal layers 101; the first film 201 and the second film 202 are provided with a plurality of penetrating circular holes 204, and the inner wall of the circular hole 204 is plated with the second metal layer 102 with a circular cross section, and the hole in the center of the second metal layer 102 is filled with a flame retardant layer. The outer surface of the first film 201 and the outer surface of the second film 202 are plated with the third metal layer 103; in this embodiment, the first film 201 and the second film 202 are both PP, and it should be noted that the first film and the second film can be selected from any one of PP, PI, PET, and PE.

[0053] In this embodiment, combined with Figure 7 As shown, the flame retardant layer includes a flame retardant 301 located at the bottom layer and a modified paraffin 302 located above the flame retardant 301, the flame retardant 301 is trimethyl phosphate, the flame retardant 301 is filled inside the hole in the center of the second metal layer 102, and the modified paraffin 302 is filled outside the flame retardant. In addition, the third metal layer 103 is a copper layer with a thickness of 200nm, and the second metal layer 102 is a lithium layer with a thickness of 100nm.

[0054] On the other hand, the present invention further provides a lithium ion battery, comprising a conductive film, and the conductive film is prepared by the above-mentioned conductive film preparation method.

[0055] In the above embodiment, by placing the flame retardant 301 sealed by the modified paraffin 302 in the circular hole 204 of the second film 202, when the temperature reaches the softening point of the modified paraffin 302, the paraffin melts from the hole and the flame retardant 301 is released from the hole, which can prevent the battery from burning due to excessive temperature. The second metal layer 102 is a lithium layer, which can also increase the energy density of the battery after the flame retardant 301 is released. In addition, adding the first metal layer 101 between the first film 201 and the second film 202 increases the conductivity and tensile strength of the conductive film.

[0056] Example 2

[0057] Reference Figure 1 As shown, the present invention discloses a method for preparing a conductive film. In this embodiment, the preparation method includes the following steps:

[0058] S10, after selecting the support layer 10, the first metal layer 101 is plated on the upper and lower surfaces of the support layer 10, wherein the support layer 10 is a PET film, and the structure formed is as follows Figure 2 As shown;

[0059] In this embodiment, a first metal layer 101 is plated on the surface of the first support layer 10 by using a vacuum coating device, and the vacuum coating device includes a magnetron sputtering device or a vacuum evaporation device; of course, a vacuum coating machine can also be used; the first metal layer 101 is an aluminum layer with a thickness of 300nm;

[0060] The main function of the first metal layer 101 is to increase the conductivity and the elongation at break of the entire conductive film. In this embodiment, the vacuum coating device is a magnetron sputtering device, and the vacuum degree of the magnetron sputtering is 0.1×10-3Pa-1.0×10-3Pa. The magnetron sputtering argon gas is used as the sputtering gas with a flow rate of 50-60ml / min. Such pressure and speed can speed up the process and improve production efficiency.

[0061] S20, compounding a first film 201 on the surface of one of the first metal layers 101, and compounding a second film 202 on the surface of another first metal layer 101; in this embodiment, Figure 3 As shown, the second film 202 is compounded on the surface of the first metal layer 101 located at the top, and the first film 201 is compounded on the surface of the first metal layer 101 located at the bottom; and the first film 201 and the second film 202 are compounded by using a coating compounding device.

[0062] S30, using thin film composite technology to composite a third film 203 on the surface of the first film 201 and the second film 202, etching a plurality of penetrating circular holes 204 on the third film 203 and the second film 202, the depth of the circular holes 204 being equal to the sum of the thickness of the second film 202 and the third film 203; at the same time, etching a plurality of penetrating circular holes 204 on another third film 203 and the first film 201, the depth of the circular holes 204 being equal to the sum of the thickness of the other third film 203 and the first film 201; refer to Figure 4 , which is a schematic diagram of a structure in which a plurality of circular holes 204 are etched on the third film 203, the second film 202 and the first film 201, and the diameter of the circular hole 204 is 600 nm;

[0063] S40, using vacuum coating technology, coating the second metal layer 102 on the outer surface of the third film 203 and the inner wall of the circular hole 204; Figure 5 As shown, at this time, the inner wall of the circular hole 204 is plated with the second metal layer 102, but the second metal layer 102 does not completely seal the circular hole 204, so a plurality of blind holes are formed on the second metal layer 102;

[0064] S50, peeling the third film 203 from the second film 202, while retaining the second metal layer 102 plated on the inner wall of the circular hole 204 of the second film 202; peeling another third film 203 from the first film 201, while retaining the second metal layer plated on the inside of the circular hole 204 of the first film 201; and the second metal layer 102 is a lithium layer of 100nm;

[0065] In this embodiment, Figure 8 As shown, a flame retardant 301 is filled in the blind hole, a layer of modified paraffin 302 is filled on the flame retardant 301, and the flame retardant 301 is filled on the basis of the modified paraffin 302, and then the modified paraffin 302 is used to seal; a composite film is obtained; the flame retardant 301 is trimethyl phosphate; and the modified paraffin 302 includes 7 parts of paraffin, 1 part of lithium chloride, 3 parts of conductive graphite and 3 parts of n-dodecanoic acid; in general, paraffin begins to soften at 50-60°C, and in this embodiment, the modified paraffin 302 can increase the softening point of paraffin to 65-80°C, thereby improving its temperature resistance;

[0066] S60, using vacuum coating technology, coating the third metal layer 103 on the upper and lower surfaces of the composite film, and rolling to obtain a conductive film, the structure of which is as follows: Fig. 9 As shown; and, the third metal layer 103 is a 200nm copper layer.

[0067] Combination Fig. 9As shown, the present invention also provides a conductive film, including a support layer 10, a first metal layer 101, a first film 201, a second film 202 and a third metal layer 103; the support layer 10 is a PET film, the upper surface and the lower surface of the support layer 10 are plated with the first metal layer 101, the first metal layer 101 is a copper layer with a thickness of 300nm, the first film 201 and the second film 202 are respectively compounded on the surfaces of the two first metal layers 101; the first film 201 and the second film 202 are provided with a plurality of penetrating circular holes 204, and the inner wall of the circular hole 204 is plated with the second metal layer 102 with a circular cross section, and the hole in the center of the second metal layer 102 is filled with a flame retardant layer. The outer surface of the first film 201 and the outer surface of the second film 202 are both plated with the third metal layer 103; in this embodiment, the first film 201 and the second film 202 are both PI, and it should be noted that the first film 201 and the second film 202 can be selected from any one of PP, PI, PET, and PE.

[0068] In this embodiment, combined with Fig. 9 As shown, the flame retardant layer includes a first flame retardant 303 located at the bottom layer, a first modified paraffin 304 located above the first flame retardant 303, a second flame retardant 305 located above the first modified paraffin 304, and a second modified paraffin 306 located above the second flame retardant 305. It can be understood that the first flame retardant 303 is filled inside the hole in the center of the second metal layer, the first modified paraffin 304 is filled outside the first flame retardant 303, the second flame retardant 305 is filled outside the first modified paraffin 304, and the second modified paraffin 306 is filled outside the second flame retardant 305; it can prevent lithium-ion batteries from burning multiple times, further improving the safety performance of the battery; the flame retardant 301 is trimethyl phosphate. In addition, the third metal layer 103 is a copper layer with a thickness of 300nm, and the second metal layer 102 is a lithium layer with a thickness of 100nm.

[0069] On the other hand, the present invention further provides a lithium ion battery, comprising a conductive film, and the conductive film is prepared by the above-mentioned conductive film preparation method.

[0070] In the above embodiment, by placing a flame retardant sealed by modified paraffin in the circular hole 204 of the second film 202, when the temperature reaches the softening point of the modified paraffin, the paraffin melts from the hole and the flame retardant is released from the hole, which can prevent the battery from burning due to excessive temperature. The second metal layer 102 is a lithium layer, which can also increase the energy density of the battery after the flame retardant is released. In addition, adding the first metal layer 101 between the first film 201 and the second film 202 increases the conductivity and tensile strength of the conductive film.

[0071] Example 3

[0072] Reference Figure 1 As shown, the present invention discloses a method for preparing a conductive film. In this embodiment, the preparation method includes the following steps:

[0073] S10, after selecting the support layer 10, the first metal layer 101 is plated on the upper and lower surfaces of the support layer 10, wherein the support layer 10 is a PET film, and the structure formed is as follows Figure 2 As shown;

[0074] In this embodiment, a first metal layer 101 is plated on the surface of the first support layer 10 by a vacuum coating device, and the vacuum coating device includes a magnetron sputtering device or a vacuum evaporation device; of course, a vacuum coating machine can also be used; the first metal layer 101 is a copper layer with a thickness of 250nm;

[0075] The main function of the first metal layer 101 is to increase the conductivity and the elongation at break of the entire conductive film. In this embodiment, the vacuum coating device is a magnetron sputtering device, and the vacuum degree of the magnetron sputtering is 0.1×10-3Pa-1.0×10-3Pa. The magnetron sputtering argon gas is used as the sputtering gas with a flow rate of 50-60ml / min. Such pressure and speed can speed up the process and improve production efficiency.

[0076] S20, compounding a first film 201 on the surface of one of the first metal layers 101, and compounding a second film 202 on the surface of another first metal layer 101; in this embodiment, Figure 3 As shown, the second film 202 is compounded on the surface of the first metal layer 101 located at the top, and the first film 201 is compounded on the surface of the first metal layer 101 located at the bottom; and the first film 201 and the second film 202 are compounded by using a coating compounding device.

[0077] S30, using thin film composite technology to composite a third film 203 on the surface of the first film 201 and the second film 202, etching a plurality of penetrating circular holes 204 on the third film 203 and the second film 202, the depth of the circular holes 204 being equal to the sum of the thickness of the second film 202 and the third film 203; at the same time, etching a plurality of penetrating circular holes 204 on another third film 203 and the first film 201, the depth of the circular holes 204 being equal to the sum of the thickness of the other third film 203 and the first film 201; refer to Figure 4 , which is a schematic diagram of a structure in which a plurality of circular holes 204 are etched on the third film 203, the second film 202 and the first film 201, and the diameter of the circular hole 204 is 600 nm;

[0078] S40, using vacuum coating technology, coating the second metal layer 102 on the outer surface of the third film 203 and the inner wall of the circular hole 204; Figure 5 As shown, at this time, the inner wall of the circular hole 204 is plated with the second metal layer 102, but the second metal layer 102 does not completely seal the circular hole 204, so a plurality of blind holes are formed on the second metal layer 102;

[0079] S50, peeling the third film 203 from the second film 202, while retaining the second metal layer 102 plated on the inner wall of the circular hole 204 of the second film 202; peeling another third film 203 from the first film 201, while retaining the second metal layer plated on the inside of the circular hole 204 of the first film 201; and the second metal layer 102 is a 20nm lithium layer;

[0080] In this embodiment, Figure 6 As shown, a flame retardant 301 is filled in the blind hole, and a layer of modified paraffin 302 is filled on the flame retardant 301 for sealing; the flame retardant 301 is trimethyl phosphate; and the modified paraffin 302 comprises 6 parts of paraffin, 0.5 parts of lithium chloride, 0.5 parts of conductive graphite and 1 part of n-dodecanoic acid; generally, paraffin begins to soften at 50-60°C, and in this embodiment, the modified paraffin 302 can increase the softening point of paraffin to 65-80°C, thereby improving its temperature resistance;

[0081] S60, using vacuum coating technology, coating the third metal layer 103 on the upper and lower surfaces of the composite film, and rolling to obtain a conductive film, the structure of which is as follows: Figure 7 As shown; and, the third metal layer 103 is a 200nm copper layer.

[0082] Combination Figure 7 As shown, the present invention also provides a conductive film, including a support layer 10, a first metal layer 101, a first film 201, a second film 202 and a third metal layer 103; the support layer 10 is a PET film, the upper and lower surfaces of the support layer 10 are plated with the first metal layer 101, the first metal layer 101 is a copper layer with a thickness of 250nm, the first film 201 and the second film 202 are respectively compounded on the surfaces of the two first metal layers 101; the first film 201 and the second film 202 are provided with a plurality of penetrating circular holes 204, and the inner wall of the circular hole 204 is plated with the second metal layer 102 with a circular cross section, and the hole in the center of the second metal layer 102 is filled with a flame retardant layer. The outer surface of the first film 201 and the outer surface of the second film 202 are both plated with the third metal layer 103; in this embodiment, the first film 201 and the second film 202 are both PET, and it should be noted that the first film 201 and the second film 202 can be selected from any one of PP, PI, PET, and PE.

[0083] In this embodiment, combined with Figure 7 As shown, the flame retardant layer includes a flame retardant 301 located at the bottom layer and a modified paraffin 302 located above the flame retardant 301, the flame retardant 301 is trimethyl phosphate, the flame retardant 301 is filled inside the hole in the center of the second metal layer 102, and the modified paraffin 302 is filled outside the flame retardant. In addition, the third metal layer 103 is a copper layer with a thickness of 250nm, and the second metal layer 102 is a lithium layer with a thickness of 20nm.

[0084] On the other hand, the present invention further provides a lithium ion battery, comprising a conductive film, and the conductive film is prepared by the above-mentioned conductive film preparation method.

[0085] In the above embodiment, by placing the flame retardant 301 sealed by the modified paraffin 302 in the circular hole 204 of the second film 202, when the temperature reaches the softening point of the modified paraffin 302, the paraffin melts from the hole and the flame retardant 301 is released from the hole, which can prevent the battery from burning due to excessive temperature. The second metal layer 102 is a lithium layer, which can also increase the energy density of the battery after the flame retardant 301 is released. In addition, adding the first metal layer 101 between the first film 201 and the second film 202 increases the conductivity and tensile strength of the conductive film.

[0086] In addition, the present invention also provides the following two comparative examples:

[0087] 1. Preparation of comparative example:

[0088] 1. The preparation method of comparative example 1 is the method in the prior art, in which a layer of metal is plated on the upper and lower surfaces of the film, and copper is plated in this embodiment.

[0089] 2. The preparation method of comparative example 2 is consistent with the method provided by the present invention, except that the middle support layer 10 is not plated with metal.

[0090] 3. The examples are samples obtained by the method provided by the present invention.

[0091] The above samples were cut into 20CM long and 2CM wide samples for testing. The tensile machine was the intelligent electronic tensile testing machine of Zhongnuo Instruments; the softening point test was carried out using an asphalt softening point tester.

[0092] A. Tensile strength test

[0093]

[0094] After comparison, it is found that the conductive film prepared by the method provided by the present invention has significantly improved tensile strength.

[0095] B. Test of electrical conductivity

[0096] Method: Directly connect the positive and negative poles of the multimeter to the two ends of the non-metallic material, turn the switch to the ohm position, and the measured data will be its resistance. The higher the resistance, the worse the conductivity.

[0097]

[0098] By comparison, the conductive film prepared by the method provided by the present invention has a relatively small resistance value, and its conductive performance is significantly improved.

[0099] C. Modified paraffin 302 softening point test data:

[0100]

[0101] 2. Preparation of Comparative Example Lithium Ion Battery:

[0102] Two groups of comparative examples were used for comparison: The assembly of the lithium-ion battery of comparative example 1: including the preparation of the positive electrode sheet: a metal aluminum layer with a thickness of 1 μm was plated on both sides of a PET with a thickness of 2 μm, and then a layer of active material layer was coated on the metal aluminum layer, the composition of the active material including: active material lithium iron phosphate, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder. The ratio of active material to conductive agent and binder is 7:1:2. The negative electrode sheet uses PET as a substrate, and then a layer of metal copper is plated on PET. The thickness of the PET is 2 μm, and the thickness of the copper metal layer is 1 μm. The negative electrode active material is lithium titanate, the binder is polyvinylidene fluoride, and the conductive agent is graphite, wherein the ratio of negative electrode active material: binder: conductive agent is 8:1:1. The electrolyte is a 1M LiPF6 solution as the electrolyte. Then the above is assembled into a button battery.

[0103] Preparation of lithium-ion battery in Example 1: The lithium-ion battery in Example 1 is different from the lithium-ion battery obtained in Comparative Example 1 in that the substrate of the negative electrode sheet adopts the conductive film provided by the present invention, and the other parts are exactly the same.

[0104] The preparation of Comparative Example 2 is different from that of the embodiment in that the Comparative Example 2 does not have holes and a flame retardant layer in the holes as in the embodiment, and the rest is exactly the same.

[0105] Preparation of Example 2: The lithium ion battery of Example 2 is completely the same as the battery of Example 1, with the only difference being that the conductive film used as the base of its negative electrode sheet contains a second flame retardant and a second modified paraffin wax.

[0106] The above-obtained batteries were placed in an oven, heated to 100 degrees at a rate of 5 degrees per minute, and then kept at a constant temperature for 30 minutes. The best result was that there was no fire or smoke. The following results were obtained:

[0107]

[0108] Examples 1-1 and 1-2 subjected to the above experiment were taken out, cooled, and then compared with Example 2. Similarly, Examples 1 and 2 were heated to 110° at a rate of 5°C per minute and then maintained for 30 minutes.

[0109] The following data is obtained:

[0110]

[0111] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for preparing a conductive film, characterized in that: The preparation method comprises the following steps: S10, after selecting a support layer, coating the first metal layer on the upper and lower surfaces of the support layer respectively; S20, compounding a first thin film on the surface of one of the first metal layers, and compounding a second thin film on the surface of the other first metal layer; S30, compounding a third film on the surfaces of the first film and the second film by using a thin film compounding technology, etching a plurality of penetrating circular holes on the third film and the second film and on another third film and the first film respectively, the depth of the circular holes on the third film and the second film is equal to the sum of the thicknesses of the third film and the second film, and the depth of the circular holes on another third film and the first film is equal to the sum of the thicknesses of another third film and the first film; S40, using vacuum coating technology to coat the second metal layer on the outer surfaces of the two third films and the inner wall of the circular hole; S50, peeling the third film from the second film and peeling another third film from the first film, while retaining the second metal layer plated on the inner wall of the circular hole of the second film and the first film; The circular hole is filled with a flame retardant, and a layer of modified paraffin wax is filled on the flame retardant to seal it; Alternatively, the circular hole is filled with a flame retardant, a layer of modified paraffin is filled on the flame retardant, and the flame retardant is filled on the basis of the modified paraffin, and then the modified paraffin is used for sealing; A composite film is obtained; S60, using vacuum coating technology to coat the upper and lower surfaces of the composite film with a third metal layer, and rolling to obtain a conductive film; The first metal layer and the third metal layer are 200-300 nm copper layers or aluminum layers, and the second metal layer is 20-100 nm lithium layer.

2. The method for preparing a conductive film according to claim 1, characterized in that: In step S10, a first metal layer is deposited on the surface of the first supporting layer by using a vacuum coating device, wherein the vacuum coating device includes a magnetron sputtering device or a vacuum evaporation device.

3. The method for preparing a conductive film according to claim 1, characterized in that: In step S20, a coating and laminating device is used to achieve lamination of the first film and the second film.

4. The method for preparing a conductive film according to claim 1, characterized in that: In step S30 , the diameter of the circular hole is 500-600 nm.

5. The method for preparing a conductive film according to claim 1, characterized in that: In step S40, after the second metal layer is plated on the outer surface of the third film and in the circular hole, an etching technique is used to remove the metal layer at the center of the circular hole, and a metal layer is retained on the inner wall of the circular hole.

6. The method for preparing a conductive film according to claim 1, characterized in that: In step S50, the flame retardant is trimethyl phosphate.

7. The method for preparing a conductive film according to claim 1, characterized in that: In step S50, the modified paraffin wax comprises 6-7 parts of paraffin wax, 0.5-1 parts of lithium chloride, 0.5-3 parts of conductive graphite and 1-3 parts of n-dodecanoic acid, and the softening point of the modified paraffin wax is 65-80°C.

8. A conductive film, characterized in that: The conductive film is prepared by the method for preparing a conductive film according to any one of claims 1 to 7, and the conductive film comprises a support layer, a first metal layer, a first film, a second film and a third metal layer; The upper surface and the lower surface of the support layer are both plated with a first metal layer, and the first film and the second film are respectively composited on the surfaces of the two first metal layers; The first film and the second film are provided with a plurality of penetrating circular holes, and the inner walls of the circular holes are plated with a second metal layer with a circular cross section, and the hole in the center of the second metal layer is filled with a flame retardant layer; The outer surface of the first film and the outer surface of the second film are both plated with a third metal layer.

9. A conductive film according to claim 8, characterized in that: The flame retardant layer comprises a flame retardant filled in the hole at the center of the second metal layer and modified paraffin filled outside the flame retardant, and the flame retardant is trimethyl phosphate.

10. The conductive film according to claim 8, characterized in that: The flame retardant layer includes a first flame retardant filled in a hole at the center of the second metal layer, a first modified paraffin filled outside the first flame retardant, a second flame retardant filled outside the first modified paraffin, and a second modified paraffin filled outside the second flame retardant, wherein the first flame retardant and the second flame retardant are trimethyl phosphate.

11. A lithium ion battery, characterized in that: The invention comprises a conductive film, and the conductive film is prepared by any conductive film preparation method according to claim 1-7.

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