Polypropylene-based composite current collectors, methods of making and using the same

Abstract

The application provides a polypropylene-based composite current collector, which comprises a polypropylene layer, a modified layer and a metal layer arranged in a stack; the modified layer is formed by grafting an end-hydroxyl acrylate and a layered double metal hydroxide onto the polypropylene layer through ultraviolet light-induced polymerization. The combination of the layered double metal hydroxide and the end-hydroxyl acrylate can increase the content of hydroxyl groups on the surface of the modified layer, thereby improving the surface tension; meanwhile, the combination can also improve the surface roughness of the modified layer; the improvement of the surface tension and the roughness can jointly promote the adhesion between the modified polypropylene layer and the metal layer. Moreover, the hydroxyl groups in the layered double metal hydroxide and the hydroxyl groups in the end-hydroxyl polyacrylate molecules can form hydrogen bonds, which can enhance the interfacial compatibility between the two and reduce the surface defects of the modified layer. Therefore, the polypropylene-based composite current collector provided by the application has strong interlayer bonding force and stable structure, and the surface tension of the modified polypropylene film is stable after being placed for three months.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a polypropylene-based composite current collector and a preparation method and application thereof. BACKGROUND

[0002] The composite current collector based on the polymer polymer film has attracted extensive attention and application in the new energy industry. At present, the composite current collector mainly includes a polymer polymer film and a metal layer stacked on the polymer polymer film. Compared with the traditional current collector, the composite current collector based on the polymer polymer film has the characteristics of low cost, good safety, light weight, good internal insulation, etc. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when applied in the battery.

[0003] Among the many polymer-based composite current collectors, the most common one is the polypropylene-based composite current collector. However, due to the extremely weak polarity of polypropylene, the surface tension of the polypropylene film is low, and the surface adhesion performance is weak, so that the adhesion between the base film and the metal layer of the prepared composite current collector is weak, which finally leads to poor structural stability of the composite current collector, affecting the normal use of the composite current collector. Among the current methods for enhancing adhesion, the mechanical roller pressing method cannot guarantee the thickness control of the composite current collector; the glue bonding method has few types of available glue, and high temperature or long time standing is required to achieve the bonding effect, which is not efficient; the vacuum evaporation method has high equipment and process cost, which is not conducive to wide application. SUMMARY

[0004] In view of the above problems existing in the prior art, the purpose of the present application is to provide a polypropylene-based composite current collector and a preparation method and application thereof. The polypropylene-based composite current collector comprises a modified layer, which can keep the surface tension of the modified polypropylene layer unchanged for a long time, and the polypropylene-based composite current collector has stable structure and strong adhesion.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a polypropylene-based composite current collector, which comprises a polypropylene layer, a modified layer and a metal layer stacked.

[0007] In one of the embodiments, the polypropylene-based composite current collector has one or more of the following characteristics:

[0008] (1) The thickness of the polypropylene layer is 2-20 microns;

[0009] (2) The thickness of the modified layer is 0.02-0.12 microns;

[0010] (3) the thickness of the metal layer is 0.5 μm to 2 μm.

[0011] In one embodiment, the terminal hydroxyl acrylate includes one or more of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 1,2-dihydroxyethyl methacrylate, 2,2-dihydroxyethyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, poly(ethylene glycol) methacrylate, and derivatives thereof.

[0012] In one embodiment, the layered double hydroxide is [M 2+ 1-x M 3+ x (OH)2](A n- ) x / n ·mH2O, M 2+ is selected from any one of Ca 2+ , Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ or Zn 2+ ;

[0013] M 3+ is selected from any one of Al 3+ , Fe 3+ or Co 3+ ;

[0014] A n- is selected from any one of Cl - , Br - , NO3 - , CO3 2- , SO4 2- or SeO4 2- .

[0015] In one embodiment, the material of the metal layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0016] In one embodiment, the polypropylene-based composite current collector further includes a protective layer, which is laminated to the surface of the metal layer.

[0017] The material of the protective layer includes one or more of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, ketjen black, carbon nanometer quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0018] The thickness of the protective layer is 0.01-0.15 μm, and the thickness of the protective layer is less than or equal to one-tenth of the thickness of the metal layer.

[0019] The application also provides a preparation method of the polypropylene-based composite current collector, comprising the following steps:

[0020] A polypropylene layer is provided, the surface of the polypropylene layer is contacted with a modification liquid, a modified layer is prepared on the polypropylene layer by using a method of ultraviolet light-induced polymerization grafting, the modification liquid comprises a hydroxyl-terminated acrylate, a layered double hydroxide and a solvent, and a metal layer is prepared by depositing a metal on the surface of the modified layer.

[0021] In one embodiment, the preparation method of the polypropylene-based composite current collector comprises the following steps:

[0022] A protective layer is prepared by depositing a material of the protective layer on the surface of the metal layer.

[0023] In one embodiment, the modification liquid comprises a hydroxyl-terminated acrylate, a layered double hydroxide, a photosensitizer and a solvent.

[0024] In one embodiment, the modification liquid has one or more of the following characteristics:

[0025] (1) In the modification liquid, the mass concentration of the hydroxyl-terminated acrylate is 20%-50%;

[0026] (2) In the modification liquid, the mass concentration of the photosensitizer is 1%-5%;

[0027] (3) In the modification liquid, the mass concentration of the layered double hydroxide is 0.1%-10%.

[0028] In one embodiment, the conditions of the ultraviolet light-induced polymerization grafting comprise one or more of the following characteristics:

[0029] (1) The ultraviolet lamp selected is a medium-pressure ultraviolet lamp, and the power density of the medium-pressure ultraviolet lamp is set to 50-300 W / cm;

[0030] (2) The reaction temperature is 25-70 °C;

[0031] (3) The reaction time is 0.5-10 min.

[0032] The application also provides a battery comprising the polypropylene-based composite current collector according to any one of the above embodiments or prepared by the preparation method according to any one of the above embodiments.

[0033] The application also provides a power utilization device comprising the battery.

[0034] Compared with the prior art, the application has the following beneficial effects:

[0035] The application provides a polypropylene-based composite current collector, which comprises a polypropylene layer, a modified layer and a metal layer arranged in a stack; the modified layer is formed by grafting an end-hydroxyl acrylate and a layered double hydroxide onto the polypropylene layer through ultraviolet light-induced polymerization. The combination of the layered double hydroxide and the end-hydroxyl acrylate can increase the content of hydroxyl groups on the surface of the modified layer, thereby improving the surface tension; at the same time, the combination can also increase the surface roughness of the modified layer, and the improvement of the surface tension and the roughness together promotes the adhesion between the modified polypropylene layer and the metal layer. In addition, the lamellar porous structure of the layered double hydroxide provides sites for the deposition of metal atoms, which can further promote the adhesion between the polypropylene layer and the metal layer. The hydroxyl groups in the layered double hydroxide and the hydroxyl groups in the end-hydroxyl polyacrylate molecules form hydrogen bonds, which can enhance the interfacial compatibility between the two and reduce the surface defects of the modified layer. Therefore, the polypropylene-based composite current collector has strong interlayer bonding force and stable structure, and the surface tension of the modified polypropylene film is stable after being placed for three months. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a structural schematic diagram of the polypropylene-based composite current collector;

[0037] In the figure, the polypropylene layer 1, the modified layer 2, the metal layer 3 and the protective layer 4. DETAILED DESCRIPTION

[0038] The polypropylene-based composite current collector, the preparation method and the application thereof will be further described in detail below in combination with specific embodiments. The application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the application more thorough and comprehensive. Of course, they are only examples and the purpose is not to limit the application.

[0039] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum value and the maximum value of the range and every value between the minimum value and the maximum value. Further, when a range is referred to as an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges incorporated therein.

[0040] 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. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0041] The application provides a polypropylene-based composite current collector, comprising a polypropylene layer, a modified layer and a metal layer which are stacked; the modified layer is formed by grafting an end-hydroxyl acrylate and a layered double hydroxide onto the polypropylene layer through ultraviolet light-induced polymerization.

[0042] The modified layer is stacked on the surface of the polypropylene layer, which can perform surface modification treatment on the polypropylene layer; the methyl group of the polypropylene layer and the carbon-carbon double bond of the end-hydroxyl acrylate react to occur addition, so the modified layer and the polypropylene film are combined by chemical bonds, and the combination is firm. At the same time, the surface of the modified layer is rich in hydroxyl groups, which is easy to interact with the atoms of the metal layer, so as to improve the adhesion between the polypropylene-based film and the metal layer, and maintain the stability of the adhesion for a long time.

[0043] In one example, the polypropylene layer is a commercial biaxially stretched polypropylene film.

[0044] In one example, the thickness of the polypropylene layer is 2 μm to 20 μm. Specifically, the thickness of the polypropylene layer includes but is not limited to 2 μm, 3 μm, 4 μm, 5 μm, 9 μm, 10 μm, 11 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm. The selection and thickness of the polypropylene layer meet the application requirements of the composite current collector, and simplify the preparation process and reduce the cost.

[0045] In one example, the thickness of the modified layer is 0.02 μm to 0.12 μm; specifically, the thickness of the modified layer includes but is not limited to 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.10 μm, 0.11 μm or 0.12 μm; the modified layer can improve the surface structure and properties of the polypropylene film. Increasing the thickness of the modified layer under the premise of uniform modification cannot further improve the surface structure and properties, and increases the cost of raw materials, and may cause uneven modification. Therefore, the modified layer should not be too thick. If the modified layer is too thin, the modification effect is slightly weak.

[0046] In one example, the modified layer is stacked on the two surfaces of the polypropylene layer which are opposite to each other.

[0047] In one example, the thickness of the modified layer stacked on the two surfaces of the polypropylene layer which are opposite to each other is consistent.

[0048] The metal layer is laminated on the surface of the modified layer, and can play a conductive role. In one example, the thickness of the metal layer is 0.5 μm to 2 μm. Further, the thickness of the metal layer is 0.7 μm to 1.2 μm; specifically, the thickness of the metal layer includes but is not limited to 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2.0 μm.

[0049] In one example, the modified layer is laminated on two opposite surfaces of the polypropylene layer, and the surface of the modified layer on the two opposite surfaces is laminated with the metal layer.

[0050] In one example, the metal layer includes a metal thin layer and a thickened metal layer.

[0051] In one example, the thickness of the metal thin layer is 30 nm to 100 nm.

[0052] In one example, the thickness of the thickened metal layer is 400 nm to 1970 nm.

[0053] In one example, the modified layer is laminated on two opposite surfaces of the polypropylene layer, and the surface of the modified layer on the two opposite surfaces is sequentially laminated with a metal thin layer and a thickened metal layer.

[0054] In one example, the material of the metal layer on the surface of the modified layer on the two opposite surfaces is consistent.

[0055] In one example, the material of the metal thin layer on the surface of the modified layer on the two opposite surfaces is consistent.

[0056] In one example, the material of the thickened metal layer on the surface of the metal thin layer on the two opposite surfaces is consistent.

[0057] In one example, the thickness of the metal layer on the surface of the modified layer on the two opposite surfaces is consistent.

[0058] In one example, the thickness of the metal thin layer on the surface of the modified layer on the two opposite surfaces is consistent.

[0059] In one example, the thickness of the thickened metal layer on the surface of the metal thin layer on the two opposite surfaces is consistent.

[0060] In one example, the terminal hydroxyl acrylate includes one or more of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 1,2-dihydroxyethyl methacrylate, 2,2-dihydroxyethyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, poly(ethylene glycol) methacrylate, and derivatives thereof.

[0061] In one example, the layered double hydroxide (LDH) is [M 2+ 1-x M 3+ x (OH)2](A n- ) x / n ·mH2O, M 2+ is selected from any one of Ca 2+ , Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , or Zn 2+ ;

[0062] M 3+ is selected from any one of Al 3+ , Fe 3+ , or Co 3+ ;

[0063] A n- is selected from any one of Cl - , Br - , NO3 - , CO3 2- , SO4 2- , or SeO4 2- .

[0064] In one example, the layered double hydroxide can be one or more of MnAl-LDH, MgAl-LDH, CuAl-LDH, NiAl-LDH, NiFe-LDH, and NiCo-LDH.

[0065] In one example, the average flake size of the layered double hydroxide is less than or equal to 200 nm. Specifically, the average flake size of the layered double hydroxide includes, but is not limited to, 10 nm, 15 nm, 18 nm, 19 nm, 20 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 180 nm, 190 nm, or 200 nm.

[0066] The addition of the layered double hydroxide in the modification solution can further increase the content of surface hydroxyl groups in the formed modified layer, thereby increasing the surface tension. On the other hand, the addition of the layered double hydroxide can increase the surface roughness of the modified layer. The increase in the surface tension and the surface roughness together promote the adhesion between the modified polypropylene film and the metal layer. In addition, the porous structure of the layered double hydroxide provides sites for the deposition of metal atoms, which further promotes the adhesion between the polypropylene layer and the metal layer. Moreover, the hydroxyl groups in the layered double hydroxide molecules can form hydrogen bonds with the hydroxyl groups in the hydroxyl-terminated polyacrylate molecules, thereby avoiding the problem of defects in the modified layer caused by the incompatibility of the two interfaces.

[0067] In one example, the material of the metal layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0068] In one example, the material of the metal layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0069] In one example, the material of the metal layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0070] The protective layer can prevent chemical corrosion or physical damage of the metal layer. In one example, the polypropylene-based composite current collector further includes a protective layer laminated on the surface of the metal layer.

[0071] In one example, the material of the protective layer includes one or more of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, ketjen black, carbon nanometer quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0072] In one example, the protective layer has a thickness of 0.01 μm to 0.15 μm, and the thickness of the protective layer is less than or equal to one-tenth of the thickness of the metal layer. Further, the thickness of the protective layer is 0.02 μm to 0.10 μm. Specifically, the thickness of the protective layer includes, but is not limited to, 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.10 μm, 0.13 μm, 0.14 μm, or 0.15 μm.

[0073] In one example, the material of the protective layer on the surface of the metal layer on the two opposite surfaces is uniform.

[0074] In one example, the thickness of the protective layer on the surface of the metal layer on the two opposite surfaces is uniform.

[0075] The present application also provides a method for preparing a polypropylene-based composite current collector, comprising the following steps:

[0076] A polypropylene layer is provided, the surface of the polypropylene layer is contacted with a modification liquid, and a modified layer is prepared on the polypropylene layer by using a method of ultraviolet light-induced polymerization grafting; the modification liquid comprises a hydroxyl-terminated acrylate, a layered double hydroxide, and a solvent.

[0077] A metal is deposited on the surface of the modified layer to prepare a metal layer.

[0078] In one example, the method for preparing a polypropylene-based composite current collector comprises the following steps:

[0079] A material of the protective layer is deposited on the surface of the metal layer to prepare a protective layer.

[0080] In one example, the modified layer is laminated on the surface of the polypropylene layer by a deposition process. The deposition process is one or more of physical vapor deposition, electroplating, and electroless plating. The physical vapor deposition can be selected from resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation, and magnetron sputtering.

[0081] In one example, the metal layer is laminated on the surface of the modified layer by a deposition process. The deposition process is one or more of physical vapor deposition, electroplating, and electroless plating. The physical vapor deposition is one or more of resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation, and magnetron sputtering.

[0082] In one example, the metal thin layer and the thickened metal layer are laminated on the surface of the modified layer by different deposition processes.

[0083] In one of the examples, the metal thin layer is laminated on the surface of the modified layer by magnetron sputtering.

[0084] In one of the examples, the thickened metal layer is laminated on the surface of the metal thin layer by electroplating.

[0085] In one of the examples, the protective layer is laminated on the surface of the metal layer by a deposition process. The deposition process is one or more of physical vapor deposition, chemical vapor deposition, in-situ forming, and coating. The physical vapor deposition can be vacuum evaporation and magnetron sputtering; the chemical vapor deposition can be atmospheric pressure chemical vapor deposition and plasma enhanced chemical vapor deposition; the in-situ forming can be a method of forming a metal oxide passivation layer on the surface of the metal layer in-situ; the coating method can be die coating, blade coating, and extrusion coating.

[0086] In one of the examples, the modified layer needs to be cleaned and dried. The cleaning time is 1-5 minutes. Cleaning the modified layer can effectively remove unreacted terminal hydroxyl acrylate.

[0087] In one of the examples, the polypropylene-based composite current collector needs to be cleaned and dried.

[0088] In one of the examples, the modification liquid includes terminal hydroxyl acrylate, layered double hydroxide, photosensitizer, and solvent. The photosensitizer can absorb ultraviolet light to generate free radicals, which in turn induce the reaction of terminal hydroxyl acrylate.

[0089] In one of the examples, the mass concentration of the terminal hydroxyl acrylate in the modification liquid is 20-50%. Specifically, the concentration of the terminal hydroxyl acrylate includes but is not limited to 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 30wt%, 35wt%, 39wt%, 40wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, or 50wt%. The concentration affects the reaction speed. Too low concentration results in slightly poor reaction effect, and too high concentration results in too intense reaction, leading to slightly poor uniformity of the modified layer.

[0090] In one of the examples, the mass concentration of the layered double hydroxide in the modification liquid is 0.1-10%. Specifically, the concentration of the layered double hydroxide includes but is not limited to 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%. The concentration affects the surface properties and structure of the formed modified layer. Too low concentration results in less obvious changes in the surface properties and structure of the formed modified layer, and too high concentration results in defects on the surface of the formed modified layer.

[0091] In one example, the mass concentration of the photosensitizer in the modification liquid is 1% to 5%. Specifically, the concentration of the benzophenone photosensitizer includes, but is not limited to, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 2.0 wt%, 3 wt%, 4 wt%, 4.5 wt%, 4.6 wt%, 4.7 wt%, 4.8 wt%, 4.9 wt%, or 5.0 wt%. The concentration of the photosensitizer also affects the reaction speed. If the concentration is too low, the reaction effect is slightly poor. If the concentration is too high, the reaction is too violent, resulting in slightly poor uniformity of the modified layer.

[0092] In one example, the photosensitizer is a benzophenone photosensitizer.

[0093] In one example, the benzophenone photosensitizer includes one or more of benzophenone, 2,4-dihydroxybenzophenone, Michler's ketone, and derivatives thereof.

[0094] In one example, in the ultraviolet light-induced graft polymerization modification, the selected ultraviolet lamp is a medium-pressure ultraviolet lamp, and the power density of the medium-pressure ultraviolet lamp is set to 50 W / cm to 300 W / cm. Specifically, the power density of the medium-pressure ultraviolet lamp includes, but is not limited to, 50 W / cm, 51 W / cm, 52 W / cm, 53 W / cm, 54 W / cm, 55 W / cm, 59 W / cm, 60 W / cm, 70 W / cm, 80 W / cm, 90 W / cm, 100 W / cm, 150 W / cm, 200 W / cm, 250 W / cm, 260 W / cm, 270 W / cm, 280 W / cm, 290 W / cm, 298 W / cm, 299 W / cm, or 300 W / cm. If the power density of the medium-pressure ultraviolet lamp is too low, the reaction efficiency will be reduced, resulting in slightly poor modification effect. If the power density is too high, the reaction is too fast, which can result in slightly poor reaction uniformity.

[0095] In one example, in the ultraviolet light-induced graft polymerization modification, the reaction temperature is 25°C to 70°C. Specifically, the reaction temperature includes, but is not limited to, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 40°C, 50°C, 60°C, 65°C, 66°C, 67°C, 68°C, 69°C, or 70°C. If the reaction temperature is too low, the reaction effect is slightly poor. If the reaction temperature is too high, the reaction speed is too fast, which can result in slightly poor reaction uniformity. Specifically, the modification liquid is heated to the reaction temperature, and then the polypropylene layer is soaked in the modification liquid to react.

[0096] In one of the examples, the reaction time in the ultraviolet light-induced graft polymerization modification is 0.5 min to 10 min. Specifically, the reaction time includes but is not limited to 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min, 1.0 min, 2.0 min, 3.0 min, 4.0 min, 5.0 min, 6.0 min, 7.0 min, 8.0 min, 9.0 min, 9.5 min, 9.6 min, 9.7 min, 9.8 min, 9.9 min or 10 min. The radiation time is low, and the reaction effect is slightly poor; the radiation time is too long, and the modified layer is too thick, resulting in slightly poor surface uniformity.

[0097] In one of the examples, the ultraviolet light-induced graft polymerization modification uses a medium-pressure ultraviolet lamp.

[0098] In one of the examples, the medium-pressure ultraviolet lamp can provide a wide-band linear spectrum in the ultraviolet and visible spectral range, i.e. in the range of 200 nm to 600 nm.

[0099] In one of the examples, the ultraviolet light-induced graft polymerization modification needs to be carried out in a protective atmosphere. The selection of the protective atmosphere can protect the activity of the free radicals generated in the reaction process.

[0100] In one of the examples, the protective atmosphere is nitrogen.

[0101] The application also provides a battery comprising the polypropylene-based composite current collector according to any one of the examples.

[0102] The application also provides an electrical device comprising the battery according to the examples.

[0103] The following are specific examples. Unless otherwise specified, the raw materials used in the examples are commercially available.

[0104] (1) Preparation of the modification solution

[0105] 2 kg of 2-hydroxyethyl methacrylate, 0.01 kg of MnAl-LDH (average particle size of 30 nm, self-synthesized, structural formula of [Mn 2+ 0.7 Al 3+ 0.3 (OH)2](NO3 - ) 0.3· 3H2O), 0.1 kg benzophenone, 7.89 kg pure water were mixed. The above reaction raw materials were mixed on a magnetic stirrer, the stirring speed was 600 rpm, the stirring time was 30 min, and a modified solution of 20 wt% 2-hydroxyethyl methacrylate, 0.1 wt% MnAl-LDH, 1 wt% benzophenone was prepared.

[0106] (2) Preparation of the modified layer

[0107] The modified solution was poured into the water tank of the film modification device, and the solution was heated to 25°C, then a commercial 4.5 μm biaxially stretched polypropylene film was placed in the modified solution, nitrogen was introduced into the device, after the modification device was filled with nitrogen, the power density of the medium pressure ultraviolet lamp was set to 50 W / cm, and the ultraviolet lamp irradiated the film surface, the irradiation time was 0.5 min. After irradiation, it was put into a pure water cleaning tank and cleaned in the pure water cleaning tank for 2.0 min, and finally into an oven at 70°C for drying, forming a modified layer on the two opposite surfaces of the polypropylene film to obtain a modified polypropylene layer.

[0108] (3) Preparation of the copper thin layer

[0109] The modified polypropylene layer prepared in (2) was placed in the cabin of the magnetron sputtering, copper metal was used as the target material, and argon was used as the gas source. A single-sided copper thin layer with a thickness of 90 nm was plated on the surface of the modified polypropylene layer prepared in (2) by magnetron sputtering in the magnetron sputtering cabin, forming a copper thin layer on the two opposite surfaces of the modified layer, and preparing a copper thin layer intermediate product.

[0110] (4) Preparation of thickened metal layer and protective layer

[0111] Then, the copper thin layer intermediate product prepared in the above step was used as the substrate for electroplating, which was divided into the following three processes: ① Electroplating: the electroplating solution was 150 g / L copper sulfate, 120 g / L sulfuric acid, 60 mg / L chloride ion, and 9 mL / L LD-5120M, the electroplating solution temperature was 25°C, the average cathode current density was 2 A / dm 2 A thickened metal layer was formed on the two opposite surfaces of the copper thin layer, the single-sided thickened metal layer had a thickness of 910 nm, and a final metal layer was obtained. ② Passivation: after electroplating, the plated film was cleaned in a water tank, then a surface protective layer was prepared by passivation in a passivation tank, the passivation temperature was 25°C, the passivation solution was 5 g / L potassium dichromate aqueous solution, and finally the film was cleaned again in a water tank. A protective layer was formed on the two opposite surfaces of the metal layer. ③ Drying: the cleaned film was dried in an oven at a temperature of 70°C, and a protective layer with a single-sided plated layer thickness of 50 nm was finally obtained, and a polypropylene-based composite current collector was prepared.

[0112] Example 2

[0113] The same as Example 1, the main difference is that the 2-hydroxyethyl methacrylate in the modifying solution is 35 wt%.

[0114] Example 3

[0115] The same as Example 1, the main difference is that the 2-hydroxyethyl methacrylate in the modifying solution is 50 wt%.

[0116] Example 4

[0117] The same as Example 2, the main difference is that the benzophenone in the modifying solution is 3 wt%.

[0118] Example 5

[0119] The same as Example 2, the main difference is that the benzophenone in the modifying solution is 5 wt%.

[0120] Example 6

[0121] The same as Example 4, the main difference is that the power density of the medium pressure ultraviolet lamp is 200 W / cm.

[0122] Example 7

[0123] The same as Example 4, the main difference is that the power density of the medium pressure ultraviolet lamp is 300 W / cm.

[0124] Example 8

[0125] The same as Example 6, the main difference is that in the preparation of the modified layer in step (2), the solution is heated to 50°C.

[0126] Example 9

[0127] The same as Example 6, the main difference is that in the preparation of the modified layer in step (2), the solution is heated to 70°C.

[0128] Example 10

[0129] The same as Example 8, the main difference is that the ultraviolet lamp irradiates the film surface for 5 min.

[0130] Example 11

[0131] The same as Example 8, the main difference is that the ultraviolet lamp irradiates the film surface for 10 min.

[0132] Example 12

[0133] The same as Example 10, the main difference is that the 2-hydroxyethyl methacrylate in the modifying solution is replaced by hydroxypropyl methacrylate.

[0134] Example 13

[0135] The same as Example 10, the main difference is that 2-hydroxyethyl methacrylate is replaced by 2,2-dihydroxyethyl methacrylate in the modifying solution.

[0136] Example 14

[0137] The same as Example 10, the main difference is that benzophenone is replaced by 2,4-dihydroxybenzophenone in the modifying solution.

[0138] Example 15

[0139] The same as Example 1, the main difference is that 2-hydroxyethyl methacrylate in the modifying solution is 19 wt%.

[0140] Example 16

[0141] The same as Example 1, the main difference is that 2-hydroxyethyl methacrylate in the modifying solution is 51 wt%.

[0142] Example 17

[0143] The same as Example 2, the main difference is that benzophenone in the modifying solution is 0.9 wt%.

[0144] Example 18

[0145] The same as Example 2, the main difference is that benzophenone in the modifying solution is 5.1 wt%.

[0146] Example 19

[0147] The same as Example 4, the main difference is that the power density of the medium pressure UV lamp is 49 W / cm.

[0148] Example 20

[0149] The same as Example 4, the main difference is that the power density of the medium pressure UV lamp is 301 W / cm.

[0150] Example 21

[0151] The same as Example 6, the main difference is that in the preparation of the modified layer of step (2), the solution is heated to 24°C.

[0152] Example 22

[0153] The same as Example 6, the main difference is that in the preparation of the modified layer of step (2), the solution is heated to 71°C.

[0154] Example 23

[0155] The same as example 8, the main difference is that the film surface is irradiated by ultraviolet lamp for 0.4 min.

[0156] Example 24

[0157] The same as example 8, the main difference is that the film surface is irradiated by ultraviolet lamp for 11 min.

[0158] Example 25

[0159] The same as example 1, the main difference is that the concentration of MnAl-LDH in the modification solution is 1 wt%.

[0160] Example 26

[0161] The same as example 1, the main difference is that the concentration of MnAl-LDH in the modification solution is 5 wt%.

[0162] Example 27

[0163] The same as example 1, the main difference is that the concentration of MnAl-LDH in the modification solution is 10 wt%.

[0164] Example 28

[0165] The same as example 1, the main difference is that the MnAl-LDH in the modification solution is replaced by MgAl-LDH (the structural formula is [Mg 2+ 0.6 Al 3+ 0.4 (OH)2](SO4 2- ) 0.2 ·5H2O).

[0166] Example 29

[0167] The same as example 1, the main difference is that the concentration of MnAl-LDH in the modification solution is 0.09 wt%.

[0168] Example 30

[0169] The same as example 1, the main difference is that the concentration of MnAl-LDH in the modification solution is 10.1 wt%.

[0170] Comparative example 1

[0171] The same as example 1, the main difference is that the polypropylene is not modified, i.e. the polypropylene-based composite current collector prepared in comparative example 1 does not include a modified layer.

[0172] (1) Preparation of metal layer

[0173] The polypropylene layer is placed in a magnetron sputtering chamber, copper metal is used as the target material, and argon gas is used as the gas source. A 90 nm thick copper thin layer is plated on the surface of the polypropylene layer in the magnetron sputtering chamber by magnetron sputtering. Copper thin layers are formed on the two opposite surfaces of the polypropylene layer to prepare a copper thin layer intermediate product.

[0174] (2) Preparation of thickened metal layer and protective layer

[0175] Then, the copper thin layer intermediate product prepared in the above step is used as the base material for electroplating. The electroplating process is divided into the following three steps: ① Electroplating: the electroplating solution is 150 g / L copper sulfate, 120 g / L sulfuric acid, 60 mg / L chloride ion, and 9 mL / L LD-5120M. The temperature of the electroplating solution is 25°C, and the average cathode current density is 2 A / dm 2 . A thickened metal layer is formed on the two opposite surfaces of the copper thin layer, with a single-sided thickened metal layer thickness of 910 nm, to obtain the final metal layer. ② Passivation: after electroplating, the plated film is cleaned in a water tank, then passivated in a passivation tank to prepare a surface protective layer. The passivation temperature is 25°C, and the passivation solution is a 5 g / L potassium dichromate aqueous solution. Finally, the film is cleaned again in a water tank to form a protective layer on the two opposite surfaces of the metal layer. ③ Drying: the cleaned film is dried in an oven at a temperature of 70°C to obtain a protective layer with a single-sided plating layer thickness of 50 nm, and a polypropylene-based composite current collector is prepared.

[0176] Comparative Example 2

[0177] The process is basically the same as in Example 1, with the main difference being that the conventional treatment method, i.e., corona treatment, is used instead of the ultraviolet light-induced modification treatment.

[0178] (1) Preparation of modified layer

[0179] First, the polypropylene layer is placed in a roll-to-roll corona treatment device. The corona power is selected to be 10 kW, the current is selected to be 6 A, and the line speed is selected to be 100 m / min. The two opposite surfaces of the polypropylene layer are modified to obtain a modified polypropylene layer.

[0180] (2) Preparation of copper thin layer

[0181] The modified polypropylene layer prepared in (1) is placed in a magnetron sputtering chamber. Copper metal is used as the target material, and argon gas is used as the gas source. A 90 nm thick copper thin layer is plated on the surface of the modified polypropylene layer in the magnetron sputtering chamber by magnetron sputtering. Copper thin layers are formed on the two opposite surfaces of the modified layer to prepare a copper thin layer intermediate product.

[0182] (3) Preparation of thickened metal layer and protective layer

[0183] Then, the copper thin layer intermediate product prepared in the above step is used as a substrate for electroplating, which is divided into the following three processes: ① Electroplating: the electroplating solution is 150 g / L copper sulfate, 120 g / L sulfuric acid, 60 mg / L chloride ion, and 9 mL / L LD-5120M, the temperature of the electroplating solution is 25°C, the average cathode current density is 2 A / dm 2 A thickened metal layer is formed on the two opposite surfaces of the copper thin layer, the thickness of the single-side thickened metal layer is 910 nm, and a final metal layer is obtained. ② Passivation: after electroplating, the plated thin film is cleaned in a water tank, and then a surface protection layer is prepared by passivation in a passivation tank, the passivation temperature is 25°C, the passivation solution is a 5 g / L potassium dichromate aqueous solution, and finally the thin film is cleaned again through a water tank, forming a protection layer on the two opposite surfaces of the metal layer. ③ Drying: the cleaned thin film is dried at an oven temperature of 70°C, and a protection layer with a single-side plated layer thickness of 50 nm is finally obtained, thereby preparing a polypropylene-based composite current collector.

[0184] Comparative Example 3

[0185] The main difference between Example 1 and Comparative Example 3 is that MnAl-LDH is not added to the modification solution.

[0186] Test Evaluation:

[0187] The adhesion between the base film and the metal layer of the composite current collector is a key indicator of the stability of the structure of the composite current collector. Here, the adhesion between the base film and the metal layer is tested. Secondly, the improvement of adhesion depends on the surface tension of the modified layer on the surface of the base film. Here, the surface tension of the modified polypropylene layer is evaluated, and the storage stability of the modified polypropylene layer is verified, i.e., the change in surface tension after storage for 3 months. In addition, in order to verify the formation and effect of the modified layer, the thickness of the modified layer is first characterized by field emission scanning electron microscopy, and then the O / C ratio of the O and C contents in the surface of the modified polypropylene layer is characterized by X-ray photoelectron spectroscopy (XPS). The specific evaluation methods are as follows:

[0188] ① Surface tension: the initial surface tension of the modified polypropylene layer and the surface tension after being placed for three months are tested according to GB / T 14216-2008.

[0189] ② Adhesion: a layer of Permacel P-94 double-sided tape is adhered to a 1 mm thick aluminum foil, a polypropylene-based composite current collector sample is adhered on top of the double-sided tape, and a layer of ethylene acrylic acid copolymer film (Dupont Nurcel0903, thickness of 50 μm) is covered on top of the sample, then the sample is placed in a 1.3×10 5 N / m 2The sample was cut into a small strip of 150 mm x 15 mm. The ethylene acrylic acid copolymer film of the sample strip was fixed to the upper clamp of the tensile testing machine, and the rest was fixed to the lower clamp. After fixing, the two were peeled at an angle of 180° and a speed of 100 mm / min to test the peeling force, i.e., the adhesion between the modified layer and the metal layer in the polypropylene-based composite current collector.

[0190] ③The modified polypropylene layer sample prepared above was placed in an argon ion polisher (Fischione 1061) to cut the sample using an argon ion beam (~1 mm). After cutting, the sample was gold sprayed to prepare a cross-section sample. The prepared cross-section sample was then placed in a field emission scanning electron microscope (Zeiss Gemini Sigma 300VP SEM) and magnified 50,000 times. After adjusting the clarity, the cross-sectional morphology of the sample was observed and the photo was output. Finally, the thickness of the modified layer in the cross-sectional morphology photo was marked using the measurement software of the electron microscope, thereby obtaining the thickness data of the modified layer.

[0191] ④Surface O / C ratio characterization: The modified polypropylene layer prepared above was processed according to the sample preparation standard of X-ray photoelectron spectroscopy (XPS), and then placed in an XPS device (model: PHI5000 Versaprobe III). The Al Kα monochromatic X-ray source was used to scan in the range of 0-1000 eV with a scanning resolution of 20 eV. The scanning results were analyzed by the built-in data processing software of the instrument, thereby characterizing the surface O / C ratio (O / C) of the film.

[0192] ⑤Surface defect rate: The modified polypropylene film was placed in a surface quality detection system (micro-visual charge-coupled device CCD) to scan the surface. Then the optical signal was converted into an electrical signal and transmitted to the computer, and the length of the film with surface defects was counted. The proportion of this length in the total length was the surface defect rate.

[0193] The test results of each example and comparative example are shown below:

[0194]

[0195] Comparative Example 1 and Examples 1-30 can be compared, it can be seen that: in Comparative Example 1, the O / C value of the surface of the unmodified polypropylene film is 0, and the O / C value of the surface of the modified polypropylene layer in Examples 1-30 is not 0, and the thickness of the modified layer is measured by the cross-sectional morphology of the sample, which proves the existence of the modified layer in Examples 1-30, and the addition of the modified layer obviously changes the surface properties. Compared with unmodified polypropylene, the modified polypropylene layer can significantly improve the surface tension of the film, thereby improving the adhesion between the prepared modified layer and the metal layer. Comparative Example 2 and Examples 1-30 can be compared, it can be seen that: compared with the traditional corona modification treatment, the surface tension of the modified polypropylene layer of the present application is stable, that is, the modified polypropylene layer can be placed for a period of time before the preparation of the polypropylene-based composite current collector, which is not possessed by the traditional corona method; in addition, the adhesion between the modified layer and the metal layer in the prepared polypropylene-based composite current collector is stronger, that is, the structure of the polypropylene-based composite current collector is more stable.

[0196] Examples 1-3 and Examples 15-16 can be compared, it can be seen that: when the concentration of 2-hydroxyethyl methacrylate is within 20-50wt%, increasing the concentration of 2-hydroxyethyl methacrylate, the surface tension of the modified polypropylene layer first increases and then decreases, and the adhesion between the prepared modified layer and the metal layer presents a consistent trend. When the concentration of monomer 2-hydroxyethyl methacrylate is more than 50wt% or less than 20wt%, the surface tension of the modified polypropylene layer is slightly poor, and the adhesion between the corresponding modified layer and the metal layer is also slightly poor.

[0197] Examples 2, 4, 5, Examples 17-18 can be compared, it can be seen that: when the concentration of benzophenone is within 1-5wt%, increasing the concentration of benzophenone, the surface tension of the modified polypropylene layer first increases and then decreases, and the adhesion between the prepared modified layer and the metal layer presents a consistent trend. When the concentration of benzophenone is less than 1wt% or more than 5wt%, the surface tension of the modified polypropylene layer is slightly poor, and the adhesion between the corresponding modified layer and the metal layer is also slightly poor.

[0198] Examples 4, 6, 7, and Examples 19-20 can be compared, it can be seen that: when the power density of the medium-pressure ultraviolet lamp is within 50-300W / cm, increasing the power density of the medium-pressure ultraviolet lamp, the surface tension of the modified polypropylene layer first increases and then decreases, and the adhesion between the prepared modified layer and the metal layer presents a consistent trend. When the power density of the medium-pressure ultraviolet lamp is less than 50W / cm or more than 300W / cm, the surface tension of the modified polypropylene layer is slightly poor, and the adhesion between the corresponding modified layer and the metal layer is also slightly poor.

[0199] From Examples 6, 8, 9 and Examples 21-22, it can be seen that when the solution temperature is within 25-70℃, the surface tension of the modified polypropylene layer first increases and then decreases with the increase of the solution temperature, and the adhesion between the modified layer and the metal layer shows a consistent trend. When the solution temperature is lower than 25℃ or higher than 70℃, the surface tension of the modified polypropylene layer is slightly poor, and the adhesion between the modified layer and the metal layer is also slightly poor.

[0200] From Examples 8, 10, 11 and Examples 23-24, it can be seen that when the ultraviolet irradiation time is within 0.5-10min, the surface tension of the modified polypropylene layer first increases and then decreases with the increase of the ultraviolet irradiation time, and the adhesion between the base film of the polypropylene-based composite current collector and the metal layer shows a consistent trend. When the ultraviolet irradiation time is lower than 0.5min or higher than 10min, the surface tension of the modified polypropylene layer is slightly poor, and the adhesion between the modified layer and the metal layer is also slightly poor.

[0201] From Examples 1, Examples 25-27, and Examples 29-30, it can be seen that when the concentration of MnAl-LDH in the modification solution is within 0.1-10wt%, the surface tension of the modified polypropylene layer first increases and then remains unchanged with the increase of the concentration of MnAl-LDH, and the adhesion between the base film of the polypropylene-based composite current collector and the metal layer shows a consistent trend. When the concentration of MnAl-LDH in the modification solution is lower than 0.1wt%, the surface tension of the modified polypropylene layer is slightly low, and the adhesion between the base film of the polypropylene-based composite current collector and the metal layer is slightly low. When the concentration of MnAl-LDH in the modification solution is higher than 10wt%, the surface tension of the modified polypropylene layer changes little, and since the concentration of MnAl-LDH increases, agglomeration is more likely to occur, and the surface of the modified layer has smaller defects.

[0202] From Examples 1, Examples 25-27, Examples 29-30 and Comparative Example 3, it can be seen that when the modification solution does not contain MnAl-LDH, the surface tension of the modified polypropylene layer is low, and the adhesion between the base film of the polypropylene-based composite current collector and the metal layer is low.

[0203] The technical features of the above-described examples can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described examples are described, and it should be understood that any combination of the technical features is within the scope of the present disclosure as long as the combination does not result in a contradiction.

[0204] The above-mentioned embodiments only express several implementation manners of the present application, facilitate concrete and detailed understanding of the technical solutions of the present application, but cannot be understood as a limitation on the patent protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments of the skilled person in the art all belong to the protection scope of the appended claims of the present application. Therefore, the protection scope of the present application patent should be subject to the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A polypropylene-based composite current collector, characterized by, The polypropylene-based composite current collector comprises a polypropylene layer, a modified layer and a metal layer which are stacked in sequence; the modified layer is formed by grafting an end-hydroxyl acrylate and a layered double hydroxide onto the polypropylene layer through ultraviolet light-induced polymerization; said layered double hydroxide is one or more of [Mn 2+ 0.7 Al 3+ 0.3 (OH)2](NO3 - ) 0.3 ·3H2O and [Mg 2+ 0.6 Al 3+ 0.4 (OH)2](SO4 2- ) 0.2 ·5H2O.

2. The polypropylene-based composite current collector of claim 1, wherein, The polypropylene-based composite current collector has one or more of the following characteristics: (1) the thickness of the polypropylene layer is 2 μm to 20 μm; (2) the thickness of the modified layer is 0.02 μm to 0.12 μm; (3) the thickness of the metal layer is 0.5 μm to 2 μm.

3. The polypropylene-based composite current collector of claim 1, wherein, The end-hydroxyl acrylate comprises one or more of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 1,2-dihydroxyethyl methacrylate, 2,2-dihydroxyethyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, poly(ethylene glycol) methacrylate and derivatives thereof.

4. The polypropylene-based composite current collector of claim 1, wherein, The material of the metal layer comprises one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium and silver.

5. The polypropylene-based composite current collector of any one of claims 1-4, wherein, The polypropylene-based composite current collector further comprises a protective layer which is stacked on the surface of the metal layer; The material of the protective layer comprises one or more of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, ketjen black, carbon nanometer quantum dots, carbon nanometer tubes, carbon nanometer fibers and graphene; The thickness of the protective layer is 0.01 μm to 0.15 μm, and the thickness of the protective layer is less than or equal to one-tenth of the thickness of the metal layer.

6. A method of making a polypropylene-based composite current collector, characterized by, The method comprises the following steps: A polypropylene layer is provided, a surface of the polypropylene layer is contacted with a modifying liquid, and a modified layer is prepared on the polypropylene layer by a method of ultraviolet light-induced polymerization grafting; the modifying liquid comprises a terminal hydroxyl acrylate, a layered double metal hydroxide, and a solvent; the layered double metal hydroxide is one or more of [Mn 2+ 0.7 Al 3+ 0.3 (OH)2](NO3 - ) 0.3 ·3H2O and [Mg 2+ 0.6 Al 3+ 0.4 (OH)2](SO4 2- ) 0.2 ·5H2O. depositing a metal on the surface of the modified layer to prepare a metal layer.

7. The method of making a polypropylene-based composite current collector of claim 6, wherein, The method comprises the following steps: depositing a material of the protective layer on the surface of the metal layer to prepare a protective layer.

8. The method of making a polypropylene-based composite current collector of claim 6, wherein, The modification liquid comprises an end-hydroxyl acrylate, a layered double hydroxide, a photosensitizer and a solvent.

9. The method of making a polypropylene-based composite current collector of claim 8, wherein, The photosensitizer is a benzophenone photosensitizer; The benzophenone photosensitizer comprises one or more of benzophenone, 2,4-dihydroxybenzophenone, Michler's ketone and derivatives thereof.

10. The method of making a polypropylene-based composite current collector of claim 8, wherein, The modification liquid has one or more of the following characteristics: (1) the mass concentration of the end-hydroxyl acrylate in the modification liquid is 20% to 50%; (2) the mass concentration of the photosensitizer in the modification liquid is 1% to 5%; (3) the mass concentration of the layered double hydroxide in the modification liquid is 0.1% to 10%.

11. The method of making a polypropylene-based composite current collector of claim 6, wherein, The conditions of the ultraviolet light-induced polymerization grafting comprise one or more of the following characteristics: (1) the selected ultraviolet lamp is a medium-pressure ultraviolet lamp, and the power density of the medium-pressure ultraviolet lamp is set to 50 W / cm to 300 W / cm; (2) the reaction temperature is 25°C to 70°C; (3) the reaction time is 0.5 min to 10 min.

12. A battery, characterized by The polypropylene-based composite current collector comprises the polypropylene-based composite current collector according to any one of claims 1 to 5.

13. An electrical device, characterized by The battery comprises the battery according to claim 12.

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