Positive electrode current collector, preparation method thereof and battery comprising positive electrode current collector

Abstract

The invention discloses a positive current collector, a preparation method thereof and a battery comprising the positive current collector. The preparation method of the positive current collector comprises the following steps: preparing a continuous thin film from a high polymer material; carrying out surface pretreatment on the continuous film; carrying out chemical plating on the pretreated film to form a metal conductive layer; carrying out electrochemical deposition on the film subjected to chemical plating to form a metal layer; and depositing the metal layer on the thin film subjected to electrochemical deposition of the metal layer by a PVD (Physical Vapor Deposition) process to obtain the positive electrode current collector. The preparation method of the lithium battery positive electrode current collector provided by the invention is simple to operate and high in yield, can reduce the risk of thermal damage of a PVD (Physical Vapor Deposition) process to a high polymer material, and can also improve the activity and roughness of the surface of a base material, so that the adhesive force of a metal layer is improved. The anode current collector prepared according to the preparation method has the advantages of strong coating binding force, lower thickness, lower density and strong conductivity.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a positive electrode current collector, its preparation method, and a battery containing the same. Background Technology

[0002] With technological advancements and the ever-growing demand for clean energy, lithium batteries, as an important energy storage device, have been widely used in various fields such as electric vehicles and portable electronic devices. Improving battery performance depends not only on innovation in active materials but also increasingly on the optimized design of components such as current collectors.

[0003] Both lithium-ion and lithium-metal batteries typically use lithium-containing transition metal oxides as the positive electrode material. The positive electrode is formed by coating the active material onto a current collector. Generally, aluminum foil is commonly used as the current collector for lithium battery positive electrodes, partly because aluminum has a higher potential (typically 3-5V vs. Li). + Under lithium oxide (Li₂O₃) at the same potential, aluminum can form a dense alumina passivation layer, preventing further corrosion. Copper, on the other hand, is easily oxidized at the same potential, leading to current collector failure. Furthermore, because aluminum's density is only one-third that of copper, it can reduce battery weight and increase energy density. In addition, although aluminum's conductivity is not as good as copper's, it is sufficient for current collector requirements, and aluminum's flexibility and ductility facilitate electrode processing. Finally, aluminum does not undergo alloying reactions with commonly used positive electrode active materials (such as lithium cobalt oxide and ternary materials), while copper may form alloys with lithium (such as Li-Cu), leading to structural damage.

[0004] Traditional positive electrode current collectors generally use a single layer of aluminum foil. However, single-layer aluminum foil has certain limitations in terms of safety, weight, and manufacturing process.

[0005] Compared to traditional single-layer aluminum foil, composite current collectors have become an important direction for the development of lithium battery current collectors due to their advantages in many aspects, such as high safety (e.g., preventing puncture of the separator and short circuit; reducing thermal runaway), long life, high energy density, and low cost.

[0006] Composite current collectors typically exhibit a "sandwich" structure consisting of a "metal conductive layer - polymer layer - metal conductive layer". In this case, the composite aluminum foil uses polymer insulating materials such as PET, PP, and PI as the intermediate support layer, with metallic aluminum deposited on both its top and bottom surfaces to form an "aluminum - polymer support layer - aluminum" sandwich structure.

[0007] However, the preparation of composite current collectors still faces certain challenges. As organic materials, polymer films have weak surface adhesion to metals, making direct metal deposition on their surfaces difficult.

[0008] Currently, composite aluminum foils on the market are mostly prepared by physical lamination process, such as using ingot hot rolling method or double-roller casting method to combine metal aluminum foil with polymer support film through hot pressing or gluing.

[0009] Although such process is mature, it has certain limitations. Specifically, the preparation process of traditional composite aluminum foil is relatively complex, involving multiple rolling and heat treatment processes, which requires high process precision. Secondly, the thickness of aluminum foil is limited by the rolling limit, and the aluminum foil prepared by traditional process is mostly 10-16 μm thick, with mainstream products around 12 μm, which is difficult to further reduce to below 10 μm. In addition, the density of aluminum foil itself is relatively large, even at a relatively thin specification, which still has a great impact on the overall quality and cost of the battery, thereby limiting the further improvement of energy density.

[0010] In addition, the thinning of the current collector has become a significant trend in the development of lithium batteries. As a non-active component, the current collector does not directly participate in the electrochemical reaction, so under the premise of ensuring its sufficient mechanical strength, electrical conductivity and safety performance, reducing its thickness as much as possible has the following advantages: 1) The current collector itself does not store energy, and thinning its thickness can release more space for filling positive active material, thereby improving the effective energy storage ratio per unit volume or weight and improving the energy density of the battery. 2) The current collector material is mainly metal such as aluminum and copper, which accounts for a large proportion of the cost of battery raw materials. By thinning the current collector, metal consumption can be significantly reduced, thereby reducing the overall manufacturing cost, especially for large-scale production needs. 3) Thin current collectors help reduce the weight of the entire electrode or even the entire battery, which has important value for applications such as electric vehicles, drones, and wearable devices that are extremely sensitive to weight.

[0011] To achieve the preparation of ultra-thin composite current collectors, existing technologies mostly use physical vapor deposition (PVD) methods such as vacuum evaporation to directly deposit a metal aluminum layer on the surface of a polymer film, so that the metal aluminum layer eventually reaches the required thickness and uniformity to meet the technical requirements of lithium battery current collectors in terms of electrical conductivity, mechanical properties, and chemical stability.

[0012] However, directly PVD plating aluminum on the surface of a polymer substrate has certain limitations. High-energy particle bombardment and local thermal effects often occur during the PVD process, which can cause thermal damage to the polymer material, resulting in warping, shrinkage, or even local thermal decomposition of the substrate, affecting its mechanical properties and dimensional stability. In addition, the interfacial bonding force between the polymer material and the metal aluminum is weak, and even if a dense film layer is prepared by PVD, there may be problems such as insufficient adhesion, peeling or cracking during subsequent processing, thereby affecting the reliability and service life of the product.

[0013] Therefore, on the basis of the prior art, further optimization is still needed to meet the development of light and thin current collectors. SUMMARY

[0014] The present application is directed to the deficiencies of the prior art, in order to solve at least one problem in the prior art, the present application provides a preparation method of positive electrode current collector, which takes high molecular material as base material, combines continuous chemical plating, electroplating and PVD process to prepare positive electrode current collector. The preparation method is simple in operation, high in yield, strong in plating layer adhesion and high in production efficiency; while reducing the weight of current collector and improving the energy density of battery, it reduces the shedding loss of positive active material and guarantees the cycle life of battery.

[0015] In the first aspect, the present application provides a preparation method of positive electrode current collector, which comprises the following steps:

[0016] The high molecular material is made into a continuous film;

[0017] The continuous film is subjected to surface pretreatment;

[0018] The pretreated film is subjected to chemical plating to form a metal conductive layer;

[0019] The film subjected to chemical plating is subjected to electrochemical deposition of metal layer;

[0020] The film subjected to electrochemical deposition of metal layer is subjected to PVD process to deposit metal layer to obtain positive electrode current collector.

[0021] In the present application, the film is made of two or more components, at least one of which can be etched.

[0022] Further, the etched film component content is less than 30wt%. Preferably, the etched film component content is less than 25wt%, less than 20wt%, less than 15wt%, less than 10% or less than 5wt%; more preferably, the content is 5-30wt%.

[0023] Etching treatment can make the surface of the base material rough, form a micro concave-convex structure, and significantly improve the adhesion between the base material and the metal layer.

[0024] In some embodiments, too high etched film component content can cause perforation problem in the roughening process, and too low etched film component content can cause reduced adhesion between the film and the metal. Perforation problem in the roughening process mainly affects the strength of the composite current collector and the flatness of the surface of the composite current collector, leading to perforation and other adverse phenomena of the composite current collector, affecting the yield of the composite current collector.

[0025] The polymer material used for preparing the continuous film includes, but is not limited to, polypropylene (PP), polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), polyphenylene sulfide (PPS), polysulfone (PPSU), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene copolymer resin (ETFE), polychlorotrifluoroethylene (PCTFE), polylactic acid (PLA), polycaprolactone (PCL), polystyrene (PS), polymethyl methacrylate (PMMA), acrylonitrile (A)-butadiene (B)-styrene (S) terpolymer (ABS), thermoplastic elastomer (TPU, TPE, TPEE, etc.), polyolefin elastomer (POE), maleic anhydride grafted polymer, and two or more of their derivatives, crosslinked products and copolymers.

[0026] Preferably, the polymer material used for preparing the continuous film is selected from at least one of PP, PI, PET and PPS.

[0027] PP, PI and PET have a lower density and a higher flexibility, so that the aluminum metal layer can generate a buckling under stress, and the buckling is sufficient to release the stress and reduce the shedding of the positive active material, thereby ensuring the cycle life of the lithium battery.

[0028] The method for preparing the film from the polymer material includes blending and processing the etchable component with the target polymer material, which can be achieved by using a banbury mixer, a single screw, a double screw or a multi-screw blending method, or a polymer kettle melting blending method. Preferably, the blending and processing method is polymer kettle melting.

[0029] The process conditions such as the melting temperature, stirring speed, blending and stirring time of the polymer material can be selected according to the type of the polymer material actually used.

[0030] By selecting a suitable blending and processing method and raw material ratio, the etchable component is uniformly dispersed in the main polymer, which is beneficial to the subsequent etching to form uniform pits. However, the present application is not limited to the case where the etchable component is uniformly distributed, and other suitable dispersion conditions, such as island structure, interpenetrating network, etc., are also within the scope of the present application.

[0031] Further, the composite material obtained after blending and processing is formed into a sheet material through melting, screw extrusion, casting and sheet casting processes; and then the obtained sheet material is formed into a composite film through a two-way stretching process.

[0032] The continuous film made of the polymer material has a thickness of 1-15 μm. Preferably, the thickness of the film is 2-14 μm, 2-13 μm, 2-12 μm, 2-11 μm, 2-10 μm, 2-9 μm, 2-8 μm, 2-7 μm, 2-6 μm or 2-5 μm; more preferably, the thickness of the film is 2-4 μm.

[0033] Compared with the traditional current collector, the thinner polymer-based film can significantly reduce the overall thickness and weight of the current collector, thereby reducing the volume of the battery or improving the energy density of the battery under the same mass of the battery.

[0034] Since these polymer materials and the film prepared therefrom are organic, the bonding force with metals is very weak, and the surface cannot be directly electroplated with a metal layer. In the prior art, a PVD process is usually used to first deposit a conductive metal layer on the surface of the polymer, and then chemical plating and electroplating are performed; or through a one-step method, a metal is directly deposited to the desired thickness by using a PVD process.

[0035] However, the PVD process needs to vaporize the metal at high temperature, which causes damage to the polymer material during production, and the PVD process has low efficiency, cannot be continuously produced for a long time, and also causes internal stress of the polymer.

[0036] Therefore, the present application selects to perform surface pretreatment on the polymer film, the pretreatment is performed at room temperature, the etching liquid in a solution state is used to etch the surface of the polymer, so that the surface of the polymer presents micro-pits, and then metal atoms are deposited in the micro-pits by chemical plating, thereby avoiding damage to the polymer material caused by high temperature.

[0037] The pretreatment includes roughening, sensitization, activation, chemical nickel plating and the like. The roughening refers to treating the substrate with a strong acid (such as chromic acid, sulfuric acid), a strong base, a strong oxidizing agent and the like, so that the surface of the substrate is in a micro-rough state, the contact surface of the plating layer and the substrate is increased, a large number of hydrophilic groups are formed on the surface of the substrate, and the substrate is changed from a hydrophobic body to a hydrophilic body. The surface of the substrate after roughening is negatively charged, and Sn 2+ , Ag + and the like are easily adsorbed, so that the sensitization, activation and chemical plating can be smoothly performed.

[0038] Optionally, before the surface pretreatment is performed on the continuous film, steps of oil removal, cleaning, drying and the like are further included. The oil removal can be performed by using a solution of alkali, acid, organic solvent and the like. The oil removal mode includes immersion brushing, ultrasonic cleaning or spraying, and the oil removal can also be heated.

[0039] The surface pretreatment performed on the continuous film according to the present application is etching treatment, wherein the etching treatment can be chemical etching by using an acid, an alkali or a reactive gas, or can be etching by using a plasma.

[0040] Further, the surface pretreatment of the continuous film is to immerse the film in etching solution to form micro-pits on the surface of the film.

[0041] The etching solution includes acid (chromic acid, hydrochloric acid, sulfuric acid or nitric acid, etc.), alkali (sodium hydroxide or potassium hydroxide, etc.), salt solution (potassium permanganate, etc.), organic solvent (trichloromethane, tetrachloromethane, dichloromethane, trichloroethane, acetone, etc.) and the like.

[0042] In the present application, the etching solution is not limited to one etching solution component, and the etching solution can also be a mixed solution containing two or more components, such as a mixed acid of chromic acid and hydrochloric acid, etc.

[0043] In the present application, when the etching solution is acid or alkali, on the one hand, the etching solution utilizes the destructive effect of acid or alkali on the polymer chain to partially etch the etchable component, and on the other hand, the etching solution utilizes the oxidation effect of acid or alkali to generate hydrophilic polar groups on the surface of the polymer, thereby enhancing the adhesion with the plating layer. When an organic solvent is used as the etching solution, the etching solution utilizes the similar-soluble principle to dissolve the etchable component in the solution, thereby leaving micro-pits on the surface of the film.

[0044] Further, the etching treatment forms micro-pits with a diameter of less than 0.5 μm on the surface of the film; preferably, the diameter of the micro-pits is less than 0.4 μm; more preferably, the diameter of the micro-pits is less than 0.3 μm.

[0045] In the present application, the diameter of the micro-pits is related to the residence time of the film in the etching solution and the concentration of the etching solution. The present application preferably uses the above-mentioned diameter of the micro-pits, and the diameter in the above range is beneficial to the deposition of metal atoms on the surface and inside of the micro-pits, thereby enhancing the adhesion of the metal film, but the present application is not limited to the above-mentioned diameter range.

[0046] The present application blends and processes the etchable component and the target polymer material to form a film, removes the etchable component in the continuous film by etching, and retains the target polymer, thereby forming pits on the surface of the polymer film, increasing the specific surface area, and depositing metal atoms in the pits in the subsequent electroless plating process, thereby effectively enhancing the adhesion of the film and the plated metal. Since the etchable component is uniformly distributed in the film, the etchable component is distributed on both sides of the film. In the surface pretreatment process, since the entire film is immersed in the solution, all the surfaces of the film form micro-pits, so all the surfaces of the film can simultaneously deposit metal atoms in the subsequent electroless plating and electroplating.

[0047] Further, the film after the surface pretreatment further includes the conventional steps of reduction, activation, debonding and the like in the prior art before electroless plating.

[0048] Further, the film after the surface pretreatment is subjected to electroless plating to form a metal conductive layer.

[0049] The electroless plating refers to the reduction of metal ions to atoms and then deposition on the surface of the film by adding catalysts into the electroless plating solution in the electroless plating stage. In this way, the metal atoms are combined with the film with enhanced binding force, and the polymer film is not damaged.

[0050] Preferably, the catalysts include at least one of colloidal palladium (Pd-Sn colloidal), ionic palladium (acidic palladium salt), nickel / cobalt-based catalysts (such as Ni-B nanoparticles), Ag + colloid (AgNO3reducing agent), Cu 2+ complex, etc.

[0051] Further, when the catalyst is colloidal palladium, the concentration of the colloidal palladium is preferably 10-50 ppm, the concentration of Sn 2+ is preferably 1-3 g / L, and the concentration of ionic palladium (Pd 2 +) is preferably 50-80 ppm.

[0052] Preferably, the material of the metal conductive layer is selected from one or more of copper, gold, silver, aluminum, nickel, titanium, aluminum, chromium, zinc, cadmium, lead, platinum, iron, cobalt, manganese, antimony, bismuth, gallium, indium, thallium, palladium, rhenium, rhodium, osmium, iridium, niobium, tungsten; more preferably, one or more of nickel, copper, gold, silver, aluminum.

[0053] Further, the thickness of the metal conductive layer formed by electroless plating is 10-500 nm. Preferably, the thickness of the metal conductive layer formed by electroless plating is 20-100 nm.

[0054] Further, the film after the electroless plating treatment is subjected to electrochemical deposition of a metal layer.

[0055] The electrochemical deposition of the metal layer refers to the deposition of a dense metal layer on the surface of the film by using electrochemical action with the film as the cathode and the electrolytic metal foil or metal plate as the anode.

[0056] Preferably, the material of the metal layer is selected from one or more of copper, gold, silver, aluminum, nickel, titanium, aluminum, chromium, zinc, cadmium, lead, platinum, iron, cobalt, manganese, antimony, bismuth, gallium, indium, thallium, palladium, rhenium, rhodium, osmium, iridium, niobium, tungsten; more preferably, one or more of nickel, copper, gold, silver, aluminum.

[0057] In the electrochemical deposition process, the electroplating is continued until the thickness of the metal layer is greater than 0.5 μm.

[0058] In the present application, the electrochemical layered metal layer can be plated with one or more than one metal to form one or more than one metal layer according to actual needs. Therefore, according to the required plated metal and the number of metal layers, the electrochemical deposition process can continue to be plated until the metal layer reaches the required thickness. Therefore, the present application is not limited to the above-mentioned metal layer thickness range.

[0059] Preferably, the plating process uses a conductive thin film as the cathode, uses a metal (titanium, gold, silver, copper, etc.) as the anode, and is carried out in an electrolyte. More preferably, the plating process uses a thin film as the cathode, uses a solid copper plate as the anode, and is carried out in a copper sulfate electrolyte.

[0060] The metal layer is thickened to a specified thickness by controlling the metal ion concentration in the electrolyte, the current density, and the additive concentration.

[0061] In some specific embodiments, a water plating (chemical plating + electrochemical deposition) process is used to plate copper on the surface of the thin film.

[0062] The water plating process has the advantages of simple operation and low cost, and can uniformly deposit a copper layer on the surface of the thin film. The copper layer has good electrical conductivity and can effectively collect and conduct the electrons generated by the positive electrode material, ensuring the charge and discharge performance of the battery.

[0063] Further, the thin film after electrochemical deposition of the metal layer is subjected to a PVD process to deposit a metal layer, thereby obtaining a positive electrode current collector.

[0064] The PVD process is selected from at least one of an evaporation method and a sputtering method. Preferably, the evaporation method is selected from at least one of vacuum evaporation, thermal evaporation, and electron beam evaporation; and preferably, the sputtering method is a magnetron sputtering method.

[0065] Further, the metal layer deposited by the PVD process is an aluminum layer.

[0066] The specific PVD technology can be selected comprehensively according to the specific material combination system (such as PET / copper, PP / aluminum) and performance requirements (such as electrical conductivity).

[0067] In some embodiments, aluminum is deposited on the surface of the copper layer by PVD.

[0068] The aluminum layer is deposited on the surface of the plated metal layer by the PVD process, which avoids damage to the polymer when the PVD process is directly deposited on the surface of the polymer. In addition, the aluminum layer can protect the copper layer and prevent oxidation, while further improving the electrical conductivity and corrosion resistance of the current collector.

[0069] The thickness of the aluminum layer is 0.2-10 μm. Preferably, the thickness of the aluminum layer is 0.2-9 μm, 0.2-8 μm, 0.2-7 μm, 0.2-6 μm, 0.2-5 μm, 0.2-4 μm, 0.2-3 μm, 0.2-2 μm, 0.2-1 μm, 0.2-0.9 μm, 0.2-0.8 μm, 0.2-0.7 μm, 0.2-0.6 μm, 0.2-0.5 μm, or 0.2-0.4 μm; more preferably, the thickness of the aluminum layer is 0.2 μm.

[0070] Preferably, the thickness deviation of the aluminum layer at different positions is controlled within the range of 0.05-0.08 μm, ensuring the uniformity and stability of the aluminum layer.

[0071] Further, the thin film after PVD treatment is subjected to passivation and drying treatment, so that the final product has excellent anti-oxidation performance. The passivation treatment can form a dense and uniform protective layer on the surface of the metal layer (e.g., the aluminum layer), effectively isolating air and moisture, preventing the metal layer (e.g., the aluminum layer) from being oxidized or corroded, thereby enhancing the long-term stability and electrochemical performance of the current collector.

[0072] Preferably, the passivation treatment can be achieved by coating one or more layers of inorganic or organic protective coating. For example, nano-aluminum oxide (Al2O3), silicon oxide (SiO2), or fluorinated polymer, etc. can be used as coating materials.

[0073] In the present application, by combining water electroplating with PVD process, not only the problems of thermal damage to the polymer thin film and poor adhesion between the polymer thin film and the plated metal layer caused by direct PVD aluminum plating are solved, but also the process flow is further optimized, which is helpful to realize the preparation of high-performance ultra-thin composite current collector and meet the requirements of lithium batteries for high energy density, light weight and reliability.

[0074] In addition, although from the electrical principle, the reduction of the thickness of the current collector will reduce its cross-sectional area, thereby increasing the resistance, in actual application, the influence can be compensated by optimizing the structure and material combination of the current collector. For example, in some specific embodiments of the present application, a composite structure of aluminum-copper-polymer-copper-aluminum is used, which introduces a copper layer while keeping the overall thickness low, thereby improving the overall conductivity and effectively suppressing the problem of resistance increase caused by the thinning of the current collector. Therefore, through the optimized design of materials and processes, the present application realizes the effective balance between "thinner, lighter" and "high conductivity".

[0075] In a second aspect, the present application provides a positive electrode current collector prepared by the preparation method of the first aspect.

[0076] In a third aspect, the present application further provides a battery comprising the positive electrode current collector according to the second aspect.

[0077] Further, the battery is a lithium ion battery.

[0078] Advantages of the present application:

[0079] 1. By adopting the fine control water electroplating (chemical plating + electrochemical deposition) process and PVD process, the overall thickness of the prepared positive electrode current collector is significantly lower than that of the traditional current collector. The lower thickness of the current collector helps to reduce the electrode tab spacing of the battery containing the current collector, thereby improving the energy density of the battery and enabling the battery to store more electrical energy under the same volume or weight.

[0080] 2. The density of the high polymer material such as PP, PI, PET, etc. is relatively small, and the reasonable structure and plating layer design make the density of the current collector of the present application smaller. This not only reduces the overall weight of the battery, but also helps to improve the endurance and portability of the battery, especially suitable for the fields of electric vehicles and portable electronic devices with high weight requirements.

[0081] 3. The price of the high polymer material is relatively low, and the cost of the water electroplating process and the PVD process is also controllable, so that the positive electrode current collector of the lithium battery of the present application has a significant advantage in cost.

[0082] 4. The electrical conductivity of copper (58 MS / m) is significantly higher than that of aluminum (37 MS / m), so the addition of a copper layer in the middle can reduce the resistance of the current collector and improve the charge and discharge efficiency of the battery. The composite current collector prepared according to the method provided by the present application combines the lightweight of aluminum and the high electrical conductivity of copper, and is therefore particularly suitable for high energy density batteries (such as electric vehicle batteries).

[0083] The preparation method of the positive electrode current collector provided by the present application is simple to operate, has a high yield, has strong plating layer adhesion, and has high production efficiency; can significantly improve the heat resistance of the surface of the high polymer material, reduce the risk of thermal damage in the subsequent PVD process, and also improve the activity and roughness of the surface of the substrate, thereby improving the adhesion of the metal layer. While reducing the weight of the current collector and improving the energy density of the battery, the shedding loss of the positive active material is reduced, and the cycle life of the battery is guaranteed. The positive electrode current collector prepared according to the preparation method of the positive electrode current collector provided by the present application has strong plating layer adhesion, lower thickness, smaller density, and strong electrical conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0084] The present application will be further described below in conjunction with the drawings and examples, in which:

[0085] Figure 1 FIG. 1 is a structural schematic diagram of the positive electrode current collector prepared by the method described in Example 1;

[0086] Figure 2The preparation process flow chart of the positive electrode current collector of the present application. DETAILED DESCRIPTION

[0087] The embodiments of the present application are described in detail below, the embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0088] Wherein, the materials can be obtained in commercial way if no special instructions, and the methods are conventional methods if no special instructions.

[0089] Example 1

[0090] The high polymer material 1 is PP M09, and the manufacturer is Maoming Branch of China Petroleum Chemical Corporation.

[0091] Example 2

[0092] The high polymer material 2: 75wt% PP M09 is blended and modified with 25wt% TPU material to prepare the high polymer material 2. The blending and modification can be realized by using mixing mill, single screw, double screw or multi-screw blending mode, or can be realized by using polymerization kettle melting blending mode, preferably the polymerization kettle melting blending mode is used to realize uniform dispersion, the blending temperature is not more than 280℃, the blending time is not more than 24h, and the stirring speed is not less than 100r / min.

[0093] Example 3

[0094] The high polymer material 3: 95wt% PET is blended and modified with 5wt% TPE material to prepare the high polymer material 3. The blending and modification can be realized by using mixing mill, single screw, double screw or multi-screw blending mode, or can be realized by using polymerization kettle melting blending mode, preferably the polymerization kettle melting blending mode is used to realize uniform dispersion, the blending temperature is not more than 300℃, the blending time is not more than 24h, and the stirring speed is not less than 100r / min.

[0095] Example 4

[0096] The high polymer material 4: 75wt% PET, 5wt% TPU and 20wt% TPE material are blended and modified to prepare the high polymer material 4. The blending and modification can be realized by using mixing mill, single screw, double screw or multi-screw blending mode, or can be realized by using polymerization kettle melting blending mode, preferably the polymerization kettle melting blending mode is used to realize uniform dispersion, the blending temperature is not more than 300℃, the blending time is not more than 24h, and the stirring speed is not less than 100r / min.

[0097] Example 5

[0098] Polymer material 5: 65% PET is blended with 35% TPE material to prepare polymer material 5. The blending modification can be achieved by using a banbury mixer, single screw, double screw or multi-screw blending method, or by using a polymer kettle melting blending method. The preferred method is the polymer kettle melting blending method to achieve uniform dispersion. The blending temperature is not more than 300°C, the blending time is not more than 24h, and the stirring speed is not less than 100r / min.

[0099] Example 6

[0100] The polymer material 2 is made into a continuous film with a thickness of 4μm. The specific operation is as follows: the uniformly mixed polymer material 2 is formed into a sheet with a certain thickness and width by melting, screw extrusion, casting and sheeting process. The sheet is finally formed into a composite continuous film by a two-way stretching process.

[0101] The above film is continuously electroplated using a continuous electroplating device.

[0102] First, the polymer film is hung so that it can be connected to the power supply to form a closed loop to allow the electroplating to proceed smoothly.

[0103] Then the film is sent to the roughening tank and continuously immersed in the etching solution to form micro-pits on the surface of the film with an average micro-pit diameter of 0.12μm. The roughening solution in the roughening tank is a high-chromium acid type roughening solution containing 400g / L chromic anhydride and 400g / L sulfuric acid, which is treated at 70°C for 12min.

[0104] The roughened film is sent to the reduction tank for reduction treatment, and then washed with clean water in the cleaning tank. The reduction solution is 1g / L sodium borohydride aqueous solution, which is treated at room temperature for 10min. After reduction treatment, the film is washed with clean water in the cleaning tank.

[0105] After reduction treatment, the film is sent to the activation tank for activation treatment, and then washed with clean water in the cleaning tank. The activation solution in the activation tank is a Pd-Sn activation solution containing hydrochloric acid 250mL / L, stannous chloride 2-8g / L and palladium 15ppm, with a temperature of 35°C and an activation time of 4min.

[0106] After activation treatment, the film is sent to the debonding tank for debonding treatment, and then washed with clean water in the cleaning tank. The debonding solution in the debonding tank is 80g / L hydrochloric acid with a temperature of 35°C and a time of 8min.

[0107] Then, the treated film is subjected to electroless copper plating to form a metal copper layer with a thickness of 0.06 μm. The electroless copper plating solution comprises copper sulfate 16 g / L, potassium sodium tartrate 14 g / L, sodium hydroxide 14.5 g / L, formaldehyde 15 mL / L, 2,2'-dipyridyl 2 mg / L, EDTA 19.5 g / L, potassium ferrocyanide 2 mg / L, methanol 2 mg / L, pH 12.5, temperature 35 °C, and time 7 min.

[0108] The treated film is subjected to electrochemical deposition of metal copper until the thickness reaches 1.2 μm. The electroplating is performed with the conductive film as cathode and copper foil as anode, the electroplating solution comprises copper sulfate 200 g / L, sulfuric acid 35 g / L and hydrochloric acid 100 mL / L, time 45 min, and temperature 25 °C.

[0109] The film is subjected to water electroplating to form a composite metal foil with a certain thickness of metal layer, and the obtained electroplated copper layer is dense, smooth and flat.

[0110] After the above steps are completed, the film is hung down.

[0111] Further, an aluminum layer is deposited on the surface of the electroplated copper layer by magnetron sputtering to obtain an aluminum-plated current collector. The polymer film with the electroplated copper layer is put into a PVD furnace, the pressure in the furnace is reduced to 0.1-0.3 Pa, argon gas is introduced and subjected to bias plasma glow treatment. The glow gas is argon, time 30 min, power 500 W, and glow time 2 min. The bias voltage is set to 60 V, the duty cycle is 50%, the aluminum target sputtering current is 50 A, and the sputtering time is 4 min.

[0112] By the above process, an aluminum layer with a thickness of about 1.0 μm is uniformly deposited on all surfaces of the polymer film to form a dense and well-adhered aluminum-plated layer.

[0113] Example 7

[0114] The method for preparing the lithium battery positive electrode current collector is the same as that in Example 6, except that:

[0115] The treated film is subjected to electroless plating to form a metal silver layer with a thickness of 0.06 μm.

[0116] The solution composition and process conditions for electroless silver plating are as follows: silver nitrate 5 g / L, EDTA 5 g / L, ethanol 50 mL / L, OP-102 mL / L, formaldehyde 5 mL / L, at room temperature, and time 30 min.

[0117] Example 8

[0118] The method for preparing the lithium battery positive electrode current collector is the same as that in Example 6, except that:

[0119] The polymer material 3 was made into a continuous film with a thickness of 4 μm;

[0120] Example 9

[0121] The method for preparing the lithium battery positive electrode current collector was the same as that of Example 6, except that:

[0122] The polymer material 4 was made into a continuous film with a thickness of 4 μm;

[0123] Example 10

[0124] The method for preparing the lithium battery positive electrode current collector was the same as that of Example 6, except that:

[0125] The polymer material 4 was made into a continuous film with a thickness of 6 μm;

[0126] The polymer film was continuously immersed in the etching solution, so as to form micro-pits on the surface of the polymer base film, with an average micro-pit diameter of 0.19 μm;

[0127] The above treated film was subjected to chemical plating to form a metal copper layer with a thickness of 0.10 μm;

[0128] The above treated film was subjected to electrochemical deposition of metal copper until the thickness reached 1.5 μm.

[0129] Example 11

[0130] The method for preparing the lithium battery positive electrode current collector was the same as that of Example 6, except that:

[0131] The etching solution used in the roughening stage was acetone.

[0132] Comparative Example 1

[0133] The method for preparing the lithium battery positive electrode current collector was the same as that of Example 6, except that:

[0134] The polymer material 1 was made into a continuous film with a thickness of 4 μm;

[0135] Comparative Example 2

[0136] A commercially available PVD aluminum-plated (one-step method) positive electrode current collector was used, with a PET thickness of 6 μm and an aluminum layer thickness of 1 μm.

[0137] Comparative Example 3

[0138] The method for preparing the lithium battery positive electrode current collector was the same as that of Example 6, except that:

[0139] The polymer material 5 was made into a continuous film with a thickness of 4 μm.

[0140] Test Example 1

[0141] Positive electrode current collector peeling force test method:

[0142] (1) Cut the positive electrode current collector into 100 mm x 50 mm; (2) Lay the positive electrode current collector sample on a stainless steel substrate and gently compact it using a skin hammer to ensure that the sample is in close contact with the stainless steel substrate; (3) Place it in a peeling force tester and set the test speed to 2 mm / min to perform the peeling force test. The peeling force tester will automatically record the maximum peeling force N between the sample and the metal substrate. Repeat the test 5 times and take the average value; (4) Calculate the adhesion: According to the recorded maximum peeling force and the sample size, calculate the adhesion of the sample according to the following formula.

[0143] Adhesion (N / cm) = Maximum peeling force (N) / Sample contact area (cm)

[0144] Test Example 2

[0145] Tensile strength and elongation at break of positive electrode current collector: The roughened film was measured according to the method for measuring tensile strength and elongation at break in 7.1 of GB / T 29847—2013 "Test methods for copper foil for printed boards".

[0146] Test Example 3

[0147] Resistance: The prepared positive electrode current collector was measured according to the method for measuring mass resistivity in GB / T 2036.

[0148] The test results are shown in Table 1:

[0149] Table 1: Test results of examples and comparative examples

[0150]

[0151]

[0152] As can be seen from Table 1, the peeling force of the inventive examples 6-10 is between 3.6-4.0 N / m, the comparative example 1 uses pure PP as the polymer substrate, which makes it difficult to form micro-pits on the surface of the PP film in the roughening stage, and it is difficult to deposit a uniform and complete metal layer subsequently, resulting in a weak binding force between the metal layer and the thin film layer, the comparative example 2 directly deposits an aluminum layer on the polymer layer by PVD process, and the binding force between the aluminum layer and the polymer layer is not strong, in addition, due to the high temperature in the PVD deposition process, the polymer base film may be damaged, resulting in internal stress in the polymer base film, and thus the deposited aluminum layer cannot be completely attached to the polymer base film. The comparative example 3 has a large proportion of etchable components in the polymer material, which causes serious etching of the polymer base film in the roughening stage, and even perforation occurs, and under the same electrochemical deposition process, it is difficult to obtain a complete and uniform metal layer, therefore, the binding force between the metal layer and the thin film layer is also low. This shows that by using etching treatment and optimized water electroplating (chemical plating + electrochemical deposition) process and PVD process, the binding force between the metal layer and the polymer thin film is significantly enhanced. The improvement of this technical effect helps the current collector to obtain higher mechanical stability, which can better withstand the subsequent electrode preparation and winding process, and is not prone to metal layer falling off. This performance is particularly crucial for ensuring the reliability of the battery during long-term cycling.

[0153] From the mechanical test results, it can also be seen that by controlling the content of the etchable component, the continuity of the base film is ensured, and good mechanical strength is shown. This shows that only the surface treatment film ensures the continuity of the base, which is beneficial to enhance the mechanical properties of the lithium battery positive electrode current collector. This also means that the prepared positive electrode current collector is less prone to breakage or damage during battery assembly and cycling, thereby improving the service life and safety of the battery.

[0154] The resistance test results show that the positive electrode current collector prepared according to the preparation method provided by the present application has similar conductivity to the positive electrode current collector prepared by the traditional PVD process, which shows that the lithium battery positive electrode current collector of the present application can be used as the positive electrode current collector of the lithium battery. It should be noted that the present application can maintain similar or even lower resistance under the condition of thinner thickness and smaller density, mainly due to the introduction of the copper layer and the deposition of the uniform and dense aluminum layer. This further shows that the present application improves the conductivity by the copper layer, and at the same time, the aluminum layer makes the current collector realize thinning and weight reduction under the premise of ensuring the conductivity, which is beneficial to improve the charge and discharge efficiency of the lithium battery, and is especially suitable for high rate and large current charge and discharge requirements.

[0155] Comprehensive peeling force, tensile strength, elongation and resistance and other indicators, it can be seen that the performance of the positive electrode current collector prepared by the preparation method provided by the application is particularly improved, and the defects such as insufficient adhesion of the metal layer, easy cracking and low mechanical properties in the traditional process are significantly improved. At the same time, due to the introduction of the copper layer and the uniform and dense aluminum layer deposition, the thinning and weight reduction are realized without losing the conductivity.

[0156] The above has made a detailed description of the embodiments of the application, the application is not limited to the above embodiments, within the knowledge range of ordinary skill in the art, various changes can be made without departing from the purpose of the application. In addition, the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for producing a positive electrode current collector, characterized by, The method comprises the following steps: forming a continuous film from a polymer material; surface pre-treating the continuous film; forming a metal conductive layer on the pre-treated film by electroless plating; forming a metal layer on the film by electrochemical deposition; forming a metal layer on the film by PVD after the electrochemical deposition of the metal layer, to obtain a positive current collector.

2. The method of claim 1, wherein, The film is made of two or more components, at least one of which can be etched.

3. The method of claim 2, wherein, The etched component of the film is less than 30wt%.

4. The method of claim 1, wherein, The surface pre-treatment refers to immersing the film in a solution, and using the etching component in the solution to etch at least one component of the film to form micro-pits on the film.

5. The method of claim 4, wherein, The diameter of the micro-pits is less than 0.5μm.

6. The method of claim 1, wherein, The thickness of the film is 1-15μm.

7. The method of claim 1, wherein, The PVD process includes at least one of magnetron sputtering, vacuum evaporation, thermal evaporation and electron beam evaporation.

8. The method of claim 1, wherein, The thickness of the metal layer deposited by the PVD process is 0.2-10μm.

9. A positive electrode current collector, characterized by, The method is prepared according to any one of claims 1-8.

10. A battery, characterized by The battery comprises the positive current collector according to claim 9.

Images