High-heat-conductivity-coefficient casting polypropylene film, high-heat-conductivity-coefficient aluminum-plastic film, preparation methods of high-heat-conductivity-coefficient casting polypropylene film and high-heat-conductivity-coefficient aluminum

Abstract

The invention relates to the technical field of soft package lithium batteries, and discloses a high-heat-conductivity-coefficient casting polypropylene film, a high-heat-conductivity-coefficient aluminum-plastic film and a preparation method thereof, and a soft package battery. The casting polypropylene film sequentially comprises an attaching layer, a high-heat-conductivity-coefficient core layer and a heat sealing layer, the fitting layer and the heat sealing layer are both made of co-polypropylene, and the high-heat-conductivity-coefficient core layer is made of homo-polypropylene and / or block polypropylene. The aluminum plastic film sequentially comprises a protective layer, a binder layer, an aluminum foil layer and the casting polypropylene layer with the high heat conductivity coefficient from top to bottom. According to the aluminum plastic film, the casting polypropylene layer and the aluminum foil layer are high in peel strength, high in electrolyte corrosion resistance, excellent in shell punching performance and high in heat conductivity coefficient, heat generated in the soft package battery under high-rate circulation can be rapidly conducted to the outside of the battery, and therefore the purpose of improving the safety of the soft package battery is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft package lithium battery, and in particular to a high-thermal-conductivity cast polypropylene film, a high-thermal-conductivity aluminum-plastic film, a preparation method thereof, and a soft package battery. BACKGROUND

[0002] In recent years, clean and low-carbon is a global energy development trend. With the introduction of relevant policies in China, the new energy industry is entering a period of rapid development, and the market in the power field has higher and higher requirements for the capacity and safety of lithium batteries. Under the dual driving of the adjustment of new energy vehicle subsidy policies and the development of new battery technologies, the dominant position of square batteries in the market is facing challenges. Due to the high energy density, good safety performance, and flexible design of soft package batteries, the application of soft package batteries in the field of new energy vehicles and unmanned aerial vehicles is accelerating.

[0003] With the development of batteries towards high-rate charging and discharging, in the process of high-rate charging and discharging, the battery needs to bear a larger charging and discharging current, resulting in a sharp increase in heat generated by the internal resistance of the battery. At the same time, under high current, the embedding / extraction speed of lithium ions in the electrode material increases, resulting in significant enhancement of concentration difference polarization and electrochemical polarization, further generating additional heat. Since soft package batteries are packaged with aluminum-plastic film, and except for the aluminum foil layer in the middle, which is metal, the other layers are all high-molecular materials, which have low thermal conductivity. Therefore, compared with metal enclosures (such as cylindrical or square batteries), soft package batteries have poor thermal conductivity, and heat is easily accumulated inside, resulting in accelerated aging and failure of the internal materials of the battery. In the worst case, the soft package battery may catch fire or explode, seriously affecting the safety of the soft package battery.

[0004] Patent CN110010801A discloses a multi-phase composite CPP heat-sealing layer, which improves the thermal conductivity of the aluminum-plastic film by adding modified thermal conductive materials to the CPP heat-sealing layer. Although this method improves the thermal conductivity of the aluminum-plastic film to some extent, the modified thermal conductive filler is directly added to the CPP heat-sealing layer, and since the thermal conductive filler has a certain electrical conductivity, the soft package battery has a large edge voltage after heat-sealing, which poses a risk of electrochemical corrosion during use of the soft package battery. Therefore, it is necessary to develop a high-thermal-conductivity aluminum-plastic film that can quickly dissipate the heat accumulated inside the soft package battery to the outside of the battery, improving the safety of the soft package battery under high-rate charging and discharging, while not affecting the other performance of the battery.

[0005] Therefore, there is an urgent need for a high-thermal-conductivity cast polypropylene film and aluminum-plastic film that can efficiently conduct heat without affecting the performance of the battery. SUMMARY

[0006] The technical problems to be solved by the present application are: overcoming the deficiencies in the prior art, providing a high-thermal-conductivity cast polypropylene film, a high-thermal-conductivity aluminum-plastic film and a preparation method thereof, and a soft-pack battery. The high-thermal-conductivity cast polypropylene film and the high-thermal-conductivity aluminum-plastic film both have a high thermal conductivity, can quickly dissipate the heat accumulated in the soft-pack battery under high-rate cycling to the outside of the battery, improve the safety of the soft-pack battery under high-rate charging and discharging, and do not affect other performances of the battery.

[0007] The technical solution adopted by the present application to solve its technical problems is:

[0008] A high-thermal-conductivity cast polypropylene film sequentially comprises a bonding layer, a high-thermal-conductivity core layer and a heat-sealing layer from top to bottom.

[0009] The materials of the bonding layer and the heat-sealing layer are both copolymerized polypropylene, and the material of the high-thermal-conductivity core layer is homopolymerized polypropylene and / or block polypropylene.

[0010] The high-thermal-conductivity core layer material further comprises a high-thermal-conductivity filler, and the components of the high-thermal-conductivity core layer are: 5-40wt% of the filler, and the balance of homopolymerized polypropylene and / or block polypropylene.

[0011] When the mass percentage of the high-thermal-conductivity filler is <5%, the thermal conductivity of the aluminum-plastic film of the high-thermal-conductivity cast polypropylene cannot be obviously improved, and the heat accumulated in the soft-pack battery cannot be quickly dissipated to the outside of the battery. When the mass percentage of the high-thermal-conductivity filler is >40%, although the thermal conductivity of the aluminum-plastic film is obviously improved, the toughness of the core layer of the cast polypropylene is affected due to the increase of the mass ratio of the high-thermal-conductivity filler, the CPP surface of the aluminum-plastic film is prone to appear whitening after being punched, and the long-term reliability of the aluminum-plastic film is reduced.

[0012] The melt index of the high-thermal-conductivity cast polypropylene film at 230℃ and under a load of 2.16kg is 1-50g / 10min, and is preferably 2-20g / 10min.

[0013] Further, the thickness ratio of the bonding layer, the high-thermal-conductivity core layer and the heat-sealing layer is 1:(1-5):1. If the proportion of the high-thermal-conductivity core layer is too small, the thermal conductivity of the aluminum-plastic film cannot be obviously improved, but if the proportion of the high-thermal-conductivity core layer is too large, the proportions of the bonding layer and the heat-sealing layer will be small, the probability of the contact between the high-thermal-conductivity filler in the core layer and the aluminum layer will be large after heat sealing, the edge voltage of the soft-pack battery will be large, and there is a risk of electrochemical corrosion in long-term use.

[0014] Further, the materials of the bonding layer and the heat-sealing layer are both binary copolymerized polypropylene and / or ternary copolymerized polypropylene.

[0015] Further, the high thermal conductivity filler is at least one of aluminum powder, copper powder, metal oxide, glass fiber, graphene and boron nitride.

[0016] Further, the high thermal conductivity filler is surface modified by a surface modifier.

[0017] The surface modifier is at least one of isocyanate, silane coupling agent, polyvinylpyrrolidone, sodium dodecyl benzene sulfonate, sodium lignosulfonate, polyvinyl alcohol, polyethylene oxide, polyacrylic acid, polymethacrylic acid and polyacrylamide.

[0018] Further, the high thermal conductivity filler has a particle size of 200 nm or less. The smaller the particle size of the high thermal conductivity filler, the easier it is to uniformly disperse in the adhesive layer, and the uniformly dispersed high thermal conductivity filler will not affect the appearance of the aluminum-plastic film due to agglomeration in the cast polypropylene, and will not easily affect the mechanical properties of the cast polypropylene layer.

[0019] An aluminum-plastic film with high thermal conductivity, sequentially comprising a protective layer, an adhesive layer, an aluminum foil layer and a high thermal conductivity cast polypropylene layer from top to bottom, wherein the high thermal conductivity cast polypropylene layer uses the high thermal conductivity cast polypropylene film described above; the adhesive layer is arranged in connection with the aluminum foil layer.

[0020] The thickness of the protective layer is 2-40 um, the thickness of the adhesive layer is 1-10 um, the thickness of the aluminum foil layer is 20-100 um, and the thickness of the high thermal conductivity cast polypropylene layer is 20-100 um.

[0021] When the thickness of the protective layer is <2 um, the protective layer cannot provide sufficient protection for the aluminum layer, and is easily broken during the shell punching process. When the thickness of the protective layer is >40 um, the protective layer is a high molecular material, and has a low thermal conductivity, so the thermal conductivity of the aluminum-plastic film is also reduced.

[0022] When the thickness of the adhesive layer is <1 um, the peel strength of the protective layer and the aluminum foil layer is reduced, causing the protective layer and the aluminum foil layer to easily separate, reducing the long-term reliability of the aluminum-plastic film. When the thickness of the adhesive layer is >10 um, the adhesive is also a high molecular material, and has a low thermal conductivity, so the thermal conductivity of the aluminum-plastic film is also reduced.

[0023] Since the aluminum foil is a metal, it has excellent thermal conductivity, so the thicker the aluminum foil, the more obvious the effect on the thermal conductivity of the aluminum-plastic film. However, when the thickness of the aluminum foil is >100 um, the strength becomes large and becomes an aluminum plate, which no longer has the processing performance of an aluminum foil. When the thickness of the aluminum foil is <20 um, the strength of the aluminum foil is too small, resulting in poor overall mechanical properties of the aluminum-plastic film, and the aluminum-plastic film is easily broken during the shell punching process.

[0024] When the thickness of the high-thermal-conductivity cast polypropylene layer is > 100 um, the thermal conductivity of the aluminum-plastic film is reduced due to the low thermal conductivity of the heat-sealing layer which is a polymer material. When the thickness of the high-thermal-conductivity cast polypropylene layer is < 20 um, the soft-pack battery heat-sealing strength is reduced due to the thin heat-sealing layer, and there is a risk of false sealing and liquid leakage.

[0025] Further, the protective layer material is at least one of nylon 6, nylon 66, aromatic nylon, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polypropylene terephthalate, and polyimide.

[0026] A preparation method of the high-thermal-conductivity aluminum-plastic film is provided, which specifically comprises the following steps:

[0027] Step S1: uniformly coating an adhesive layer on the outer surface of the aluminum foil layer by means of gravure coating;

[0028] Step S2: laminating the protective layer on the adhesive layer, and completing the lamination of the protective layer and the aluminum foil layer by means of a compound roller;

[0029] Step S3: extruding the high-thermal-conductivity cast polypropylene layer from a three-layer co-extrusion die by means of the lamination layer, the high-thermal-conductivity core layer, and the heat-sealing layer, and uniformly laminating the high-thermal-conductivity cast polypropylene layer on the inner surface of the aluminum foil layer to obtain the finished high-thermal-conductivity aluminum-plastic film.

[0030] A soft-pack battery comprises the high-thermal-conductivity aluminum-plastic film.

[0031] The soft-pack battery can be a lithium ion battery, such as a lithium ion secondary battery. The battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.

[0032] The electrolyte comprises a lithium salt and an organic solvent; the lithium salt can be LiFSI, LiPF6, LiTFSI, LiODFB, LiBF4, LiClO4, etc.; the organic solvent can be ethylene glycol dimethyl ether DME, DOL, tetrahydrofuran THF, 3,3,3-trifluoropropyl methyl dimethoxy silicon FMS, and fluoroethylene carbonate FEC, etc., and the concentration thereof can be selected as needed.

[0033] The separator can be made of conventional materials in the art, including but not limited to at least one of polyethylene, polypropylene, glass fiber, and non-woven fabric. The separator can be a single-layer film or a multi-layer composite film.

[0034] The negative electrode sheet can be made of conventional materials in the art. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer on one side or both sides of the negative electrode current collector, and the negative electrode active material layer can comprise a negative electrode active material, a conductive agent, and a binder.

[0035] The mass percentage of each component in the negative active material layer is: 80wt%-99.8wt% of the negative active material, 0.1wt%-10wt% of the conductive agent, and 0.1wt%-10wt% of the binder.

[0036] The negative active material includes a carbon-based negative material and / or a silicon-based negative material. The carbon-based negative material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon. The silicon-based negative material is selected from at least one of nano-silicon, a silicon alloy, a silicon-oxygen negative material (SiOx, 0

[0037] The conductive agent is selected from at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber. The binder is selected from at least one of carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride (PVDF), and polyethylene oxide.

[0038] The present application has the following advantages: the design is reasonable, the preparation method is simple, and the present application has the following advantages:

[0039] (1) The high-thermal-conductivity filler is added to the high-thermal-conductivity core layer, and then the high-thermal-conductivity core layer and the heat-sealing layer are extruded through a three-layer co-extrusion die to obtain a high-thermal-conductivity cast polypropylene layer, and then the aluminum-plastic film is prepared. By adding the high-thermal-conductivity filler, the thermal conductivity of the aluminum-plastic film is improved, the heat accumulated inside the soft package battery under high-rate cycling can be quickly dissipated to the outside of the battery, and the safety of the soft package battery under high-rate charging and discharging is improved. By controlling the adding mode of the high-thermal-conductivity filler, the peeling force of the aluminum foil layer and the high-thermal-conductivity cast polypropylene layer is not affected, the electrolyte corrosion resistance is strong, the edge voltage of the soft package battery after heat sealing is not affected, and the long-term storage reliability of the soft package battery is improved.

[0040] (2) The high-thermal-conductivity filler is at least one of metal powder, metal oxide, glass fiber, graphene, and boron nitride, and the barrier property is better than that of high-molecular material, so that the barrier property of the aluminum-plastic film is improved. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0042] Figure 1 is a schematic diagram of the high thermal conductivity aluminum plastic film in the present application;

[0043] Figure 2 is a cross-sectional view of the high thermal conductivity core layer without adding high thermal conductivity fillers;

[0044] Figure 3 is a cross-sectional view of the high thermal conductivity core layer with adding high thermal conductivity fillers;

[0045] Figure 4 is an SEM diagram of the high thermal conductivity filler in the present application.

[0046] In the figure: 1. protective layer, 2. adhesive layer, 3. aluminum foil layer, 4. high thermal conductivity cast polypropylene film layer, 4-1. bonding layer, 4-2. high thermal conductivity core layer, 4-3. heat sealing layer. DETAILED DESCRIPTION

[0047] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0048] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form also includes the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the present description, they indicate the presence of a feature, step, operation, device, component and / or combination thereof.

[0049] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0050] A high thermal conductivity cast polypropylene film, from top to bottom, includes a bonding layer 4-1, a high thermal conductivity core layer 4-2 and a heat sealing layer 4-3; the materials of the bonding layer 4-1 and the heat sealing layer 4-3 are both copolymerized polypropylene, and the material of the high thermal conductivity core layer 4-2 is homopolymerized polypropylene and / or block polypropylene.

[0051] The thickness ratio of the bonding layer 4-1, the high thermal conductivity core layer 4-2 and the heat sealing layer 4-3 is 1:1 to 5:1.

[0052] The materials of the bonding layer 4-1 and the heat sealing layer 4-3 are both binary copolymerized polypropylene and / or ternary copolymerized polypropylene.

[0053] The high-thermal-conductivity core layer 4-2 material further comprises a high-thermal-conductivity filler, and the high-thermal-conductivity core layer 4-2 component is: 5-40 wt% of the filler, and the balance being homopolymer polypropylene and / or block polypropylene. The homopolymer polypropylene and / or block polypropylene is mixed with the filler to obtain the high-thermal-conductivity core layer 4-2 by co-extrusion. Preferably, the mass percentage of the filler is 15-25 wt%.

[0054] The high-thermal-conductivity filler is at least one of aluminum powder, copper powder, metal oxide, glass fiber, graphene, and boron nitride.

[0055] The high-thermal-conductivity filler is surface-modified by a surface modifier; the surface modifier is at least one of isocyanate, silane coupling agent, polyvinylpyrrolidone, sodium dodecyl benzene sulfonate, sodium lignosulfonate, polyvinyl alcohol, polyethylene oxide, polyacrylic acid, polymethacrylic acid, and polyacrylamide. The surface modifier is preferably a silane coupling agent.

[0056] Taking graphene modified by the silane coupling agent KH-560 as an example, the molecular structure of KH-560 is CH2CHCH2O(CH2)2Si(OCH3)3, which is represented by A-SiX3, wherein A is CH2CHCH2O(CH2)2, and X is OCH3; the reaction mechanism of the graphene modified by the silane coupling agent is as follows:

[0057] The first step is hydrolysis of the silane coupling agent:

[0058]

[0059] The second step is modification of the graphene by the silane coupling agent:

[0060]

[0061] The particle size of the high-thermal-conductivity filler is 200 nm or less, and is preferably 10-100 nm.

[0062] The particle preparation method of the high-thermal-conductivity core layer 4-2 is as follows: the homopolymer polypropylene or block polypropylene and the modified high-thermal-conductivity filler are blended, and then extruded by a single-screw extruder / double-screw extruder, granulated, and molded to obtain the high-thermal-conductivity polypropylene core layer raw material particles.

[0063] A high-thermal-conductivity aluminum-plastic film sequentially comprises a protective layer 1, an adhesive layer 2, an aluminum foil layer 3, and a high-thermal-conductivity cast polypropylene layer 4 from top to bottom, wherein the high-thermal-conductivity cast polypropylene layer 4 is made of the high-thermal-conductivity cast polypropylene film; a bonding layer 4-1 is arranged in connection with the aluminum foil layer 3; the thickness of the protective layer 1 is 2-40 um, the thickness of the adhesive layer 2 is 1-10 um, the thickness of the aluminum foil layer 3 is 20-100 um, and the thickness of the high-thermal-conductivity cast polypropylene layer 4 is 20-100 um. Preferably, the thickness of the protective layer 1 is 5-15 um, the thickness of the adhesive layer 2 is 2-5 um, the thickness of the aluminum foil layer 3 is 50-100 um, and the thickness of the high-thermal-conductivity cast polypropylene layer 4 is 20-40 um.

[0064] The material of the protective layer 1 is at least one of nylon 6, nylon 66, aromatic nylon, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyimide.

[0065] A preparation method of the high-thermal-conductivity aluminum-plastic film, specifically comprising the following steps:

[0066] In step S1, the adhesive layer 2 is uniformly coated on the outer surface of the aluminum foil layer 3 by gravure coating.

[0067] In step S2, the protective layer 1 is bonded to the adhesive layer 2, and the bonding of the protective layer 1 and the aluminum foil layer 3 is completed by extrusion through a compound roller.

[0068] In step S2, the bonding layer 4-1, the high-thermal-conductivity core layer 4-2, and the heat-sealing layer 4-3 are extruded through a three-layer co-extrusion die to obtain the high-thermal-conductivity cast polypropylene layer 4, which is uniformly bonded to the inner surface of the aluminum foil layer 3, thereby obtaining the finished high-thermal-conductivity aluminum-plastic film.

[0069] A soft package battery comprising the high-thermal-conductivity aluminum-plastic film.

[0070] Example 1

[0071] Step (1), preparation of the high-thermal-conductivity core layer 4-2

[0072] The homopolymer polypropylene or block polypropylene and the modified high-thermal-conductivity filler with a particle size of 150 nm are blended, wherein the mass ratio of the high-thermal-conductivity filler is 5%, and the high-thermal-conductivity polypropylene core layer raw material particles are obtained by single-screw extruder / double-screw extruder extrusion, granulation, and molding.

[0073] Step (2), preparation of the high-thermal-conductivity aluminum-plastic film

[0074] The adhesive layer 2 with a thickness of 6 um is uniformly coated on the outer surface of the aluminum foil layer 3 with a thickness of 30 um by means of gravure coating, the protective layer 1 (PA6) with a thickness of 25 um is attached on the adhesive layer 2, and the protective layer 1 and the aluminum foil layer 3 are attached by extrusion through a compound roller, and the semi-finished product after the attachment of the protective layer 1 and the aluminum foil layer 3 is aged at 80 DEG C for 4D; then the polypropylene layer with high thermal conductivity is extruded into a film with a thickness of 65 um according to the thickness ratio of the attachment layer 4-1, the core layer 4-2 with high thermal conductivity and the heat-sealing layer 4-3 of 1:3:1, and is uniformly attached on the inner surface of the aluminum foil layer 3 to obtain the aluminum-plastic film with high thermal conductivity. The aluminum-plastic film with high thermal conductivity is wound into a large mother roll after being detected for defects by an online CCD, and is used for the preparation of soft-pack lithium batteries after being slitted; the structure of the aluminum-plastic film with high thermal conductivity is as shown in Figure 1

[0075] Step (3), preparation of soft-pack batteries

[0076] The positive electrode sheet, the negative electrode sheet and the separator are assembled into an electric core, and the electrolyte is injected, and the soft-pack lithium ion battery is prepared through the processes of aluminum-plastic film shell punching, packaging, baking, aging, formation, sorting and the like.

[0077] Examples 2 to 5

[0078] The difference from Example 1 is that in step (2), the thickness ratio of the attachment layer 4-1, the core layer 4-2 with high thermal conductivity and the heat-sealing layer 4-3 is 1:1:1 (Example 2), 1:2:1 (Example 3), 1:4:1 (Example 4) and 1:5:1 (Example 5) respectively.

[0079] Examples 6 to 7

[0080] The difference from Example 3 is that the material of the protective layer 1 is different, and specifically:

[0081] Example 6: PET (polyethylene terephthalate);

[0082] Example 7: PI (polyimide).

[0083] Comparative Examples 1 and 2

[0084] The difference from Example 1 is that in step (2), the thickness ratio of the attachment layer 4-1, the core layer 4-2 with high thermal conductivity and the heat-sealing layer 4-3 is 1:6:1 (Comparative Example 1) and 1:0.5:1 (Comparative Example 2) respectively.

[0085] The specific parameters of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 1.

[0086] Table 1 Specific parameters of Examples 1 to 7 and Comparative Examples 1 and 2 ​

[0087]

[0088]

[0089] The high-thermal-conductivity aluminum-plastic film and the soft package battery prepared from Example 1 to Example 7 and Comparative Example 1 to Comparative Example 2 were evaluated by the following specific method.

[0090] The thermal conductivity of the high-thermal-conductivity aluminum-plastic film was determined according to the method of ASTM D5740-17.

[0091] The heat sealing strength of the high-thermal-conductivity aluminum-plastic film was determined according to the method of GB / T 2358-1998.

[0092] The edge voltage of the soft package battery was determined according to the method of GB / T 18278-2013.

[0093] Different rate cycle determination method: under the condition of 25±2℃, 1C, 2C, 3C, 5C, 7C, 10C current constant discharge to discharge cut-off voltage, stand by 0.5h, 1C, 2C, 3C, 5C, 7C, 10C current constant charge to charge limit voltage, stand by 0.5h, 1C, 2C, 3C, 5C, 7C, 10C current constant discharge to discharge cut-off voltage, recorded as 1 standard charge-discharge cycle. In turn, repeat 10 times of charge-discharge cycle, connect temperature data line on the surface of soft package battery, real-time collect the surface temperature of soft package battery. The results are shown in Table 2.

[0094] Table 2 evaluation results of Example 1 to Example 7 and Comparative Example 1 to Comparative Example 2

[0095]

[0096] From Table 2, the higher the thermal conductivity of the aluminum-plastic film, the higher the temperature of the battery surface after the cycle charge-discharge under different rates, which indicates that the heat generated inside the battery is conducted to the surface, which can better bring out the heat inside the battery.

[0097] Figure 2 is the cross-sectional view of the high-thermal-conductivity core layer without adding high-thermal-conductivity filler; Figure 3 is the cross-sectional view of the high-thermal-conductivity core layer adding high-thermal-conductivity filler. By comparison, Figure 3 The polypropylene core layer adds high-thermal-conductivity filler, which improves the thermal conductivity of polypropylene, thereby improving the thermal conductivity of the aluminum-plastic film. Finally, the heat accumulated inside the soft package battery under high rate cycle can be quickly dissipated to the outside of the battery, reducing the temperature inside the battery and improving the safety of the soft package battery under high rate charge-discharge, while not affecting other performance of the battery.

[0098] Figure 4It is the SEM diagram of the high thermal conductivity filler in the application. Figure 4 It can be known that the high thermal conductivity filler modified by the silane coupling agent in the application has the advantages of good monodispersity and good sphericity, is well dispersed in polypropylene and is not prone to agglomeration.

[0099] In summary, the application has the following advantages of reasonable design and simple preparation method:

[0100] (1) The high thermal conductivity filler is added to the high thermal conductivity core layer, and then the high thermal conductivity core layer and the heat-sealing layer are extruded through a three-layer co-extrusion die to obtain a high thermal conductivity cast polypropylene layer, and then an aluminum-plastic film is prepared, the thermal conductivity of the aluminum-plastic film is improved by adding the high thermal conductivity filler, the heat accumulated in the soft package battery under high rate cycling can be quickly dissipated to the outside of the battery, and the safety of the soft package battery under high rate charging and discharging is improved; and by controlling the adding mode of the high thermal conductivity filler, the peeling force of the aluminum foil layer and the high thermal conductivity cast polypropylene layer is not affected, the electrolyte corrosion resistance is strong, the edge voltage of the soft package battery after heat sealing is not affected, and the long-term storage reliability of the soft package battery is improved.

[0101] (2) Since the high thermal conductivity filler is at least one of metal powder, metal oxide, glass fiber, graphene and boron nitride, the barrier property is better than that of high molecular material, and the barrier property of the aluminum-plastic film can be improved.

[0102] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A high thermal conductivity cast polypropylene film characterized by: The laminated layer (4-1), the high-thermal-conductivity core layer (4-2) and the heat-sealing layer (4-3) are sequentially arranged from top to bottom. The laminated layer (4-1) and the heat-sealing layer (4-3) are both made of copolymerized polypropylene, and the high-thermal-conductivity core layer (4-2) is made of homopolymerized polypropylene and / or block polypropylene. The high-thermal-conductivity core layer (4-2) further comprises a high-thermal-conductivity filler, and the components of the high-thermal-conductivity core layer (4-2) are as follows: 5-40wt% of the filler, and the balance of homopolymerized polypropylene and / or block polypropylene.

2. The high thermal conductivity cast polypropylene film according to claim 1, characterized in that: The thickness ratio of the laminated layer (4-1), the high-thermal-conductivity core layer (4-2) and the heat-sealing layer (4-3) is 1:(1-5):

1.

3. The high thermal conductivity cast polypropylene film according to claim 1, characterized in that: The laminated layer (4-1) and the heat-sealing layer (4-3) are both made of binary copolymerized polypropylene and / or ternary copolymerized polypropylene.

4. The high thermal conductivity cast polypropylene film according to claim 1, characterized in that: The high-thermal-conductivity filler is selected from at least one of aluminum powder, copper powder, metal oxide, glass fiber, graphene and boron nitride.

5. The high thermal conductivity cast polypropylene film according to claim 1, wherein: The particle size of the high-thermal-conductivity filler is 10-200nm.

6. The high thermal conductivity cast polypropylene film according to claim 1, wherein: The high-thermal-conductivity filler is surface-modified by a surface modifier. The surface modifier is at least one of isocyanate, silane coupling agent, polyvinylpyrrolidone, sodium dodecyl benzene sulfonate, sodium lignosulfonate, polyvinyl alcohol, polyethylene oxide, polyacrylic acid, polymethacrylic acid and polyacrylamide.

7. A high thermal conductivity lidding film, characterized by: The high-thermal-conductivity cast polypropylene layer (4) is made of the high-thermal-conductivity cast polypropylene film according to any one of claims 1-6. The thickness of the protective layer (1) is 2-40um, the thickness of the adhesive layer (2) is 1-10um, the thickness of the aluminum foil layer (3) is 20-100um, and the thickness of the high-thermal-conductivity cast polypropylene layer (4) is 20-100um.

8. The high thermal conductivity LAM according to claim 7, characterized in that: The material of the protective layer (1) is at least one of nylon 6, nylon 66, aromatic nylon, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polypropylene terephthalate and polyimide.

9. A method of producing the high thermal conductivity LAM as claimed in any one of claims 7 to 8, characterized by: The method comprises the following steps: In step S1, the adhesive layer (2) is uniformly coated on the outer surface of the aluminum foil layer (3) by gravure coating. In step S2, the protective layer (1) is laminated on the adhesive layer (2), and the lamination of the protective layer (1) and the aluminum foil layer (3) is completed by extrusion of a compound roller. In step S3, the laminated layer (4-1), the high-thermal-conductivity core layer (4-2) and the heat-sealing layer (4-3) are extruded by a three-layer co-extrusion die to obtain the high-thermal-conductivity cast polypropylene layer (4), which is uniformly laminated on the inner surface of the aluminum foil layer (3) to obtain the finished high-thermal-conductivity aluminum-plastic film.

10. A pouch battery, characterized by: The soft package battery comprises the high-thermal-conductivity aluminum-plastic film according to any one of claims 7-8.

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