Composite current collector, preparation method thereof and all-solid-state battery

Abstract

The embodiment of the invention provides a composite current collector, a preparation method thereof and an all-solid-state battery. The composite current collector comprises a polymer conductive layer comprising a first surface and a second surface which are oppositely arranged; a first metal layer and a first conductive ion electronic layer are sequentially arranged on the first surface in the direction away from the polymer conductive layer; a second metal layer and a second conductive ion electronic layer are sequentially arranged on the second surface along the direction far away from the polymer conductive layer; the polymer conductive layer comprises a first polymer and a first conductive agent; the first ion-conducting electronic layer and the second ion-conducting electronic layer both comprise a solid electrolyte, a second polymer and a second conductive agent. According to the composite current collector, the polymer conductive layer, the first metal layer, the second metal layer, the first conductive ion electronic layer and the second conductive ion electronic layer are arranged, so that the finally obtained composite current collector shows excellent performance in the aspects of thermal stability, safety, electron and ion transmission efficiency and corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, and more specifically, to a composite current collector, its preparation method, and an all-solid-state battery. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, wide operating temperature range, lack of memory effect, and long cycle life, have been widely used in electric vehicles, portable electronic products, rail transportation, and energy storage systems. Currently, traditional liquid lithium-ion batteries use organic liquid electrolytes, which pose safety hazards such as leakage, combustion, and explosion. Using solid-state electrolytes to replace traditional flammable organic liquid electrolytes can effectively improve the safety performance of lithium-ion batteries; therefore, the development of high-energy-density all-solid-state lithium-ion batteries has received widespread attention.

[0003] In traditional liquid lithium-ion batteries, aluminum foil is used as the positive electrode current collector, and copper foil is used as the negative electrode current collector. For all-solid-state batteries, sulfide and halide solid electrolytes readily react with trace amounts of water to generate H₂S and HCl gases, which corrode the current collector and limit their application in all-solid-state batteries. Furthermore, in all-solid-state batteries, the active material near the current collector is difficult to fully participate in electrochemical reactions due to limited ion transport within the electrode, leading to increased internal polarization and accelerated degradation of battery cycle performance. In addition, most composite current collectors studied are three-layer composite structures of "metal-polymer-metal." The polymer interlayer can melt rapidly at high temperatures, preventing thermal runaway, and its lightweight properties help improve the battery's energy density. However, the insulating properties of the polymer interlayer restrict electron conduction between the two electrodes, resulting in independent electron transport within the two electrode layers, increasing the complexity of the battery assembly process.

[0004] There is currently no good solution to the above problems. Summary of the Invention

[0005] This application provides a composite current collector, its preparation method, and an all-solid-state battery to solve the technical problems of existing all-solid-state battery current collectors, which are prone to thermal runaway, corrosion by H2S and HCl gases, and have low ion transport rates near the current collector side electrode, thus leading to poor safety and electrochemical performance of the corresponding all-solid-state batteries.

[0006] According to a first aspect of the embodiments of this application, a composite current collector is provided, comprising: a polymer conductive layer including a first surface and a second surface disposed opposite to each other; on the first surface, a first metal layer and a first ion-conducting electron layer are sequentially disposed along a direction away from the polymer conductive layer; on the second surface, a second metal layer and a second ion-conducting electron layer are sequentially disposed along a direction away from the polymer conductive layer; the polymer conductive layer includes a first polymer and a first conductive agent; both the first ion-conducting electron layer and the second ion-conducting electron layer include a solid electrolyte, a second polymer, and a second conductive agent.

[0007] Further, in the polymer conductive layer, the weight ratio of the first polymer to the first conductive agent is 1:(0.1~0.3); and / or, the first polymer is selected from one or more of polyimide, polyethylene terephthalate, polyethylene and polypropylene; and / or, the first conductive agent is selected from one or more of vapor-grown carbon fiber, conductive carbon black SuperP, carbon nanotubes, graphene and acetylene black.

[0008] Furthermore, the first metal layer and the second metal layer are each independently an aluminum layer or a copper layer, and the density of the aluminum layer and the copper layer are each independently 95%~98%.

[0009] Furthermore, in the first and second ion-conducting electron layers, the weight ratio of the solid electrolyte, the second polymer, and the second conductive agent is independently 1:(0.02~0.1):(0.45~0.60); and / or, the solid electrolyte is an oxide solid electrolyte, and the D50 of the solid electrolyte is 100nm~300nm; and / or, the second polymer is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyvinyl alcohol; and / or, the second conductive agent is selected from one or more of vapor-grown carbon fiber, conductive carbon black SuperP, carbon nanotubes, graphene, and acetylene black.

[0010] Furthermore, the total thickness of the composite current collector is 5μm~15μm; in the composite current collector, the thickness ratio of the first ion-conducting electron layer, the first metal layer, the polymer conductive layer, the second metal layer and the second ion-conducting electron layer is 1:(2~3):(3~4):(2~3):1.

[0011] According to a second aspect of the embodiments of this application, a method for preparing the above-mentioned composite current collector is also provided, comprising: step S1, preparing a first polymer and a first conductive agent into a first slurry, coating the first slurry to obtain a first wet film, and drying the first wet film to obtain a polymer conductive layer; step S2, depositing a first metal layer and a second metal layer on a first surface and a second surface of the polymer conductive layer respectively by magnetron sputtering; step S3, preparing a solid electrolyte, a second polymer and a second conductive agent into a second slurry, coating the second slurry on the side surface of the first metal layer away from the polymer conductive layer and the side surface of the second metal layer away from the polymer conductive layer respectively, and forming a second wet film and a third wet film respectively; and drying the second wet film and the third wet film to form a first ion-conducting electron layer and a second ion-conducting electron layer respectively, thereby obtaining a composite current collector.

[0012] Further, the preparation process of the first slurry includes: mixing the first polymer and the first solvent in a first mixing process to obtain a first adhesive solution with a mass concentration of 5 wt.% to 10 wt.%; mixing the first conductive agent and the second solvent in a second mixing process to obtain a first suspension with a solid content of 25 wt.% to 30 wt.%; mixing the first adhesive solution and the first suspension in a third mixing process to obtain the first slurry; the preparation process of the second slurry includes: mixing the second polymer and the third solvent in a fourth mixing process to obtain a second adhesive solution with a mass concentration of 5 wt.% to 10 wt.%; mixing the solid electrolyte, the second conductive agent, and the fourth solvent in a fifth mixing process to obtain a second suspension with a solid content of 45 wt.% to 50 wt.%; mixing the second adhesive solution and the second suspension in a sixth mixing process to obtain the second slurry.

[0013] Furthermore, the first, third, fourth, and sixth mixtures are all carried out by stirring, with each stirring rate independently ranging from 1000 r / min to 2000 r / min and each stirring time independently ranging from 30 min to 60 min; and / or, the second and fifth mixtures are both carried out by ultrasonic dispersion, with each ultrasonic dispersion frequency independently ranging from 80 Hz to 120 Hz and each time independently ranging from 30 ± 5 min; and / or, the first, second, third, and fourth solvents are each independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and dimethyl sulfoxide; and / or, the first and second drying temperatures are each independently ranging from 60 °C to 80 °C and each drying time is independently ranging from 12 h to 24 h.

[0014] Furthermore, during magnetron sputtering, the vacuum level of the deposition chamber is 0.8 × 10⁻⁶. -4 Pa ~ 1.0 × 10 - 4Pa, argon flow rate of 40 sccm~60 sccm, operating pressure of 0.5 Pa~2 Pa, sputtering power of 70 W~200 W, sputtering time of 1 h~1.5 h, and substrate temperature of 40 °C~50 °C.

[0015] According to a third aspect of the embodiments of this application, an all-solid-state battery is also provided, which includes at least one of the above-described composite current collectors.

[0016] Compared with the prior art, this application has the following advantages:

[0017] The composite current collector provided in this application comprises a polymer conductive layer, a metal layer, and a corrosion-resistant and ion-conducting electronic layer. The metal layer is disposed on both sides of the polymer conductive layer, and the corrosion-resistant and ion-conducting electronic layer is disposed on the surface of the metal layer. The polymer conductive layer promotes rapid electron conduction between the metal layers on both sides of the polymer conductive layer, and can also rapidly melt at high temperatures, cutting off the electron transport path, thereby suppressing the risk of thermal runaway in all-solid-state batteries and further improving the safety performance of all-solid-state batteries. The corrosion-resistant and ion-conducting electronic layer has good ion and electron conduction capabilities, which can effectively improve the ion and electron conduction capabilities of the electrode near the current collector side in all-solid-state batteries, enabling the active material to fully participate in the electrochemical reaction, reducing the polarization inside the battery, and preventing the metal layer current collector from being corroded by H2S and HCl, further improving the long-cycle performance of all-solid-state batteries. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the composite current collector provided according to Embodiment 1 of this application.

[0020] The above figures include the following reference numerals:

[0021] 10. Polymer conductive layer; 21. First metal layer; 22. Second metal layer; 31. First ion-conducting electron layer; 32. Second ion-conducting electron layer. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0023] As described in the background art, existing all-solid-state battery current collectors suffer from problems such as susceptibility to thermal runaway, corrosion by H2S and HCl gases, and low ion transport rates near the current collector-side electrode, leading to poor safety and electrochemical performance of the corresponding all-solid-state batteries. To address these technical problems, according to a first aspect of this application, a composite current collector is provided, comprising: a polymer conductive layer 10, including a first surface and a second surface disposed opposite to each other; on the first surface, a first metal layer 21 and a first ion-conducting electron layer 31 are sequentially disposed along a direction away from the polymer conductive layer 10; on the second surface, a second metal layer 22 and a second ion-conducting electron layer 32 are sequentially disposed along a direction away from the polymer conductive layer 10; the polymer conductive layer 10 contains a first polymer and a first conductive agent; both the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32 contain a solid electrolyte, a second polymer, and a second conductive agent.

[0024] The composite current collector provided in this application includes a polymer conductive layer, two metal layers, and two ion-conducting electron layers. The metal layers are disposed on both sides of the polymer conductive layer, and the ion-conducting electron layers are disposed on the surface of the metal layers. The polymer conductive layer promotes rapid electron conduction between the metal layers on both sides of the polymer conductive layer and can rapidly melt at high temperatures, cutting off the electron transport path, thereby suppressing the risk of thermal runaway in all-solid-state batteries and further improving the safety performance of all-solid-state batteries. The two outermost ion-conducting electron layers have good ion and electron conductivity, which can effectively improve the ion and electron conductivity of the electrode near the current collector side in the all-solid-state battery, enabling the active material to fully participate in the electrochemical reaction, reducing internal polarization of the battery, and preventing the metal layer current collector from being corroded by H2S and HCl. This allows for stable collection and output of current for the all-solid-state battery, further improving the long-cycle performance of the all-solid-state battery.

[0025] In several embodiments, to maintain the integrity of the polymer matrix while maximizing the filling density of the first conductive agent, thereby further improving the distribution density of the formed conductive network and ultimately obtaining a composite current collector with better mechanical properties and conductivity, the weight ratio of the first polymer to the first conductive agent in the polymer conductive layer 10 is preferably 1:(0.1~0.3). Furthermore, the first polymer can be selected from one or more of polyimide, polyethylene terephthalate, polyethylene, and polypropylene; and / or, the first conductive agent can be selected from one or more of vapor-grown carbon fibers, conductive carbon black SuperP, carbon nanotubes, graphene, and acetylene black. Based on the above, in several preferred embodiments, the polymer conductive layer 10 is formed from polyimide and carbon nanotubes at a weight ratio of 10:(1.0~1.2); or, the polymer conductive layer 10 is formed from polyethylene and carbon nanotubes at a weight ratio of 10:(1.0~1.2). The aforementioned preferred polymer conductive layers 10 can, on the one hand, utilize conductive agents to promote electron conduction between the metal layers on both sides of the polymer, and on the other hand, utilize the high-temperature melting properties of the polymer to cut off the electron transport path, thereby improving the safety performance of solid-state batteries.

[0026] In several embodiments, the first metal layer 21 and the second metal layer 22 are preferably each independently an aluminum layer or a copper layer, and the density of the aluminum layer and the copper layer are each independently 95%~98%. Aluminum and copper have better conductivity and mechanical strength, and are low in cost, which can significantly improve the electron transport path of the composite current collector while ensuring the mechanical strength of the composite current collector. In practical applications, when the composite current collector is a positive current collector, both the first metal layer 21 and the second metal layer 22 are aluminum layers; while when the composite current collector is a negative current collector, both the first metal layer 21 and the second metal layer 22 are copper layers.

[0027] In several embodiments, to enhance the synergistic effect of the solid electrolyte, the second polymer, and the second conductive agent, the weight ratio of the solid electrolyte, the second polymer, and the second conductive agent in the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32 is preferably 1:(0.02~0.1):(0.45~0.60). At this ratio, the ion-conducting and electronic properties of the coating can be fully utilized, thereby significantly improving the overall performance of the resulting composite current collector. Furthermore, it is preferable that the solid electrolyte is an oxide solid electrolyte with a D50 of 100nm~300nm to facilitate the formation of a more continuous ion conduction path and to promote uniform dispersion with the second polymer matrix and the second conductive agent. If the solid electrolyte particle size is too small, agglomeration is likely to occur; conversely, if the particle size is too large, the slurry dispersion will be uneven and rapid sedimentation may occur.

[0028] For the second polymer, it is preferably selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyvinyl alcohol. For the second conductive agent, it is preferably selected from one or more of vapor-grown carbon fibers, conductive carbon black SuperP, carbon nanotubes, graphene, and acetylene black. In practical applications, the oxide solid electrolyte can be selected from one or more of the following types: Li 1+ x Al x Ti 2-x (PO4)3, where 0 ≤ x ≤ 0.65; Li 1+x Al x Ge 2-x (PO4)3, where 0 ≤ x ≤ 0.65; Li 3x La 2 / 3-x TiO3, where 0.05 ≤ x ≤ 0.2; Li7La3Zr2O 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 .

[0029] In several more preferred embodiments, the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32 are each independently composed of Li 1+x Al x Ge 2-x (PO4)3, conductive carbon black SuperP and polyvinylidene fluoride are formed in a weight ratio of 10:(4~6):1, where x is 0.3~0.6; or, the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32 are each independently formed from Li 1+ x Al x Ti 2-x (PO4)3, acetylene black and polytetrafluoroethylene are formed in a weight ratio of 10:(4~6):1, where x is 0.25~0.5.

[0030] In several embodiments, the total thickness of the composite current collector is preferably 5 μm to 15 μm to better balance mechanical strength, electrochemical performance, and overall battery energy density. Furthermore, the thickness ratio of the first ion-conducting electron layer 31, the first metal layer 21, the polymer conductive layer 10, the second metal layer 22, and the second ion-conducting electron layer 32 in the composite current collector is preferably 1:(2~3):(3~4):(2~3):1, which further optimizes the overall performance of the composite current collector and further improves the long-cycle performance of the all-solid-state battery. In this preferred thickness configuration, the polymer conductive layer 10 serves as an intermediate layer, promoting rapid electron conduction between the metal layers on both sides of the polymer conductive layer. Simultaneously, it can rapidly melt at high temperatures, cutting off the electron transport pathway and thus suppressing the risk of thermal runaway in the all-solid-state battery, further improving its safety performance. The outer ion-conducting electron layer, which directly contacts the active material, possesses excellent ion and electron conduction capabilities. This effectively improves the ion and electron conduction capabilities of the electrode near the current collector in the all-solid-state battery, enabling the active material to fully participate in the electrochemical reaction, reducing internal polarization, and preventing corrosion of the metal current collector by H2S and HCl. It can stably collect and output current for the all-solid-state battery, ultimately improving the cycle stability of the all-solid-state battery.

[0031] Specifically, in order to optimize the electrochemical performance and safety of the resulting composite current collector to a greater extent while maintaining a thinner and lighter profile, preferably: the thickness of the polymer conductive layer 10 is 2μm to 4μm; and / or, the thicknesses of the first metal layer 21 and the second metal layer 22 are each independently 2μm to 3μm; and / or, the thicknesses of the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32 are each independently 1μm to 2μm.

[0032] The embodiments of this application also provide a method for preparing the above-mentioned composite current collector, including: step S1, preparing a first polymer and a first conductive agent into a first slurry, coating the first slurry to obtain a first wet film, and drying the first wet film to obtain a polymer conductive layer 10; step S2, depositing a first metal layer 21 and a second metal layer 22 on the first and second surfaces of the polymer conductive layer 10 respectively by magnetron sputtering; step S3, preparing a second slurry by preparing a solid electrolyte, a second polymer, and a second conductive agent, coating the second slurry on the side of the first metal layer 21 away from the polymer conductive layer 10 and the side of the second metal layer 22 away from the polymer conductive layer 10 respectively, and forming a second wet film and a third wet film respectively; the second wet film and the third wet film are dried in a second process to form a first ion-conducting electron layer 31 and a second ion-conducting electron layer 32 respectively, thereby obtaining a composite current collector.

[0033] Regarding the aforementioned composite current collector, this application provides a corresponding preparation method. By preparing a first polymer and a first conductive agent into a first slurry, and then forming a polymer conductive layer 10 through coating and drying steps, the uniform dispersion of the first conductive agent in the polymer matrix can be ensured, increasing the electron transport path. Simultaneously, the first polymer can rapidly melt at high temperatures, cutting off the electron transport channel, which can suppress the risk of thermal runaway in all-solid-state batteries and further improve the safety performance of all-solid-state batteries. Depositing the metal layer using magnetron sputtering allows for precise control of the metal layer thickness while ensuring uniform coverage of metal particles in the polymer conductive layer 10, significantly improving the electron transport path of the composite current collector while maintaining its mechanical strength. Finally, a second slurry is prepared by mixing a solid electrolyte, a second polymer, and a second conductive agent, and then uniformly coated onto the surface of the metal layer to form an ion-conducting electron layer. This step ensures that the outermost layer of the composite current collector possesses both good ion and electron conductivity, and protects the metal layer from corrosion by H2S and HCl gases.

[0034] To ensure more thorough mixing of the components in the first and second slurries, resulting in a more uniform slurry and a more uniform coating with fewer defects during subsequent coating processes, thereby significantly improving the overall performance of the composite current collector, the following preferred method is used: the preparation process of the first slurry includes: first mixing of a first polymer and a first solvent to obtain a first adhesive solution with a mass concentration of 5 wt.% to 10 wt.%; second mixing of a first conductive agent and a second solvent to obtain a first suspension with a solid content of 25 wt.% to 30 wt.%; and third mixing of the first adhesive solution and the first suspension to obtain the first slurry. The preparation process of the second slurry includes: fourth mixing of a second polymer and a third solvent to obtain a second adhesive solution with a mass concentration of 5 wt.% to 10 wt.%; fifth mixing of a solid electrolyte, a second conductive agent, and a fourth solvent to obtain a second suspension with a solid content of 45 wt.% to 50 wt.%; and sixth mixing of the second adhesive solution and the second suspension to obtain the second slurry.

[0035] In the actual preparation process, the first, third, fourth, and sixth mixing processes are preferably carried out by stirring, with each stirring rate independently ranging from 1000 r / min to 2000 r / min and each stirring time independently ranging from 30 min to 60 min; and / or, the second and fifth mixing processes are carried out by ultrasonic dispersion, with each ultrasonic dispersion frequency independently ranging from 80 Hz to 120 Hz and each time independently ranging from 30 ± 5 min. The stirring under the above-mentioned specific conditions can promote the mixing of the components through mechanical force, while ultrasonic dispersion can utilize the cavitation effect of ultrasound to break the binding forces between particles, making them more uniformly dispersed in the solvent. Preferably, both are used in combination in the preparation method provided in this application, which can promote a more uniform distribution of the components in the slurry and reduce the formation of agglomerates.

[0036] Furthermore, the first solvent, second solvent, third solvent, and fourth solvent may each be independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and dimethyl sulfoxide. Based on the above solvents, it is correspondingly preferred that the temperature of the first drying and the second drying are each independently 60°C to 80°C, and the time is each independently 12h to 24h.

[0037] Furthermore, to optimize the uniformity and integrity of the resulting metal layer, the vacuum level of the deposition chamber is preferably 0.8 × 10⁻⁶ during the magnetron sputtering process. -4 Pa ~ 1.0 × 10 -4 Pa, argon flow rate of 40 sccm~60 sccm, operating pressure of 0.5 Pa~2 Pa, sputtering power of 70 W~200 W, sputtering time of 1 h~1.5 h, and substrate temperature of 40 °C~50 °C.

[0038] Embodiments of this application also provide an all-solid-state battery, which includes at least one of the aforementioned composite current collectors. Because the composite current collector provided in this application is designed with high-temperature melting, efficient electron and ion transport, and corrosion resistance in mind, its design incorporates a polymer conductive layer, a metal layer, and an ion-conducting electron layer. The polymer conductive layer promotes rapid electron conduction between the metal layers on both sides of the polymer conductive layer, and can rapidly melt at high temperatures, cutting off the electron transport path, thereby suppressing the risk of thermal runaway in the all-solid-state battery and further improving its safety performance. The corrosion-resistant ion-conducting electron layer has excellent ion and electron conduction capabilities, effectively improving the ion and electron conduction capabilities of the electrode near the current collector side in the all-solid-state battery, enabling the active material to fully participate in the electrochemical reaction, reducing internal polarization of the battery, and preventing the metal current collector from being corroded by H2S and HCl, further improving the long-cycle performance of the all-solid-state battery.

[0039] In several preferred embodiments, the all-solid-state battery includes two composite current collectors, one of which serves as the positive electrode current collector and the other as the negative electrode current collector. That is, this preferred embodiment uses two composite current collectors, one as the positive electrode current collector and the other as the negative electrode current collector, which can simultaneously improve the cycle stability and safety performance of the all-solid-state battery.

[0040] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0041] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0043] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0044] Example 1

[0045] A structural schematic diagram is shown below. Figure 1 Preparation method of positive electrode composite current collector:

[0046] (1-1) Weigh 10g of polyimide (PI) as the first polymer and mix it with N,N-dimethylformamide (DMF) solvent. Stir at high speed at room temperature for 30 minutes at a stirring rate of 1200r / min to prepare a clear and transparent PI polymer solution with a mass concentration of 8wt.%.

[0047] (1-2) Weigh 1g of the first conductive agent carbon nanotubes (CNTs) and disperse them in DMF solvent. Perform ultrasonic dispersion at 100Hz for 30min to form a uniform suspension with a solid content of 28wt.%. Mix it with the first polymer solution obtained above and stir at high speed at room temperature for 30min at a stirring rate of 1200r / min to obtain PI-CNTs conductive slurry, i.e., the first slurry.

[0048] (1-3) The first slurry is coated on the substrate and dried under vacuum at 80°C for 24 hours. After the film is removed, a polymer conductive layer 10 is obtained with a thickness of 2 μm, wherein the weight ratio of the first polymer to the first conductive agent is 1:0.1.

[0049] (2) Al metal elements were deposited on both sides of the polymer conductive layer 10 by magnetron sputtering to obtain a first metal layer 21 with a thickness of 2 μm and a second metal layer 22 with a thickness of 2 μm, both with a density of 98%. During the coating process, the vacuum degree of the deposition chamber was adjusted to 1.0 × 10⁻⁶. -4 The sputtering pressure was below Pa, with an argon gas flow rate of 60 sccm, the operating pressure controlled at 0.5 Pa, the sputtering power at 150 W, the sputtering time at 1 h, and the substrate temperature at 40 °C.

[0050] (3-1) Weigh 1g of polyvinylidene fluoride (PVDF) as the second polymer and mix it with DMF solvent. Stir at high speed at room temperature for 30 minutes at a stirring rate of 1200r / min to prepare a clear and transparent PVDF polymer solution with a mass concentration of 8wt.%.

[0051] (3-2) Weigh 10g of LAGP oxide solid electrolyte (Li) with a particle size D50 = 100nm. 1.5 Al 0.5 Ge 1.5 (PO4)3) 5g of conductive carbon black SuperP was dispersed in DMF solvent as a second conductive agent and ultrasonically dispersed at 100Hz for 30min to form a uniform suspension with a solid content of 48wt.%. It was then mixed with the above PVDF polymer solution and stirred at high speed at room temperature at a stirring rate of 1200r / min for 30min to obtain the anti-corrosion and ion-conducting electronic layer slurry, i.e., the second slurry.

[0052] (3-3) The obtained second slurry is coated on the surfaces of the two metal layers prepared in step (2) that are not in contact with the polymer conductive layer 10. After vacuum drying at 80°C for 24 hours, a first ion-conducting electron layer 31 with a thickness of 1 μm and a second ion-conducting electron layer 32 with a thickness of 1 μm are formed (the weight ratio of the solid electrolyte, the second polymer and the second conductive agent in both is 1:0.1:0.5), thereby obtaining a composite current collector.

[0053] The total thickness of the resulting composite current collector is 9 μm, wherein the thickness ratio of the first ion-conducting electron layer 31, the first metal layer 21, the polymer conductive layer 10, the second metal layer 22, and the second ion-conducting electron layer 32 is 1:2:3:2:1.

[0054] The component content and solvents used in each of the above layers are shown in Table 1, and the thickness characteristics of each layer are shown in Table 2.

[0055] A structural schematic diagram is shown below. Figure 1 Preparation method of negative electrode composite current collector: Change Al in step (2) to Cu and repeat the above steps to prepare negative electrode composite current collector.

[0056] Examples 2 to 10

[0057] The only difference between Examples 2 to 10 and Example 1 is that the component content, solvent used, or thickness of each layer are different, as detailed in Tables 1 and 2.

[0058] Comparative Example 1

[0059] A 9μm thick aluminum foil was directly used as the positive electrode current collector sample.

[0060] A copper foil with a thickness of 9 μm was directly used as the negative electrode current collector sample.

[0061] Comparative Example 2

[0062] A method for preparing a positive electrode composite current collector: The only difference between this comparative example and Example 1 is that steps (3-1) to (3-3) are not performed, but the product obtained in step (2) is used directly as the obtained positive electrode current collector sample;

[0063] A method for preparing a negative electrode composite current collector: The only difference between this comparative example and Example 1 is that steps (3-1) to (3-3) were not performed, but the product obtained in step (2) was directly used as the negative electrode current collector sample.

[0064] Comparative Example 3

[0065] A method for preparing a positive electrode composite current collector: The only difference between this comparative example and Example 1 is that the first conductive agent was not used in steps (1-1) to (1-3).

[0066] A method for preparing a negative electrode composite current collector: The only difference between this comparative example and Example 1 is that the first conductive agent was not used in steps (1-1) to (1-3).

[0067] Comparative Example 4

[0068] A method for preparing a positive electrode composite current collector: The only difference between this comparative example and Example 1 is that a solid electrolyte is not used in steps (3-1) to (3-3).

[0069] A method for preparing a negative electrode composite current collector: The only difference between this comparative example and Example 1 is that a solid electrolyte is not used in steps (3-1) to (3-3).

[0070] Table 1

[0071]

[0072] In the table above, LLTO is equivalent to Li 0.33 La 0.557 TiO3,LLZO is Li7La3Zr2O 12 LATP is Li 1.3 Al 0.3 Ti 1.7 (PO4)3. Examples with the same component content as in Example 1 are not shown in Table 1 above.

[0073] Table 2

[0074]

[0075] Examples and comparative examples with the same layer thickness characteristics as in Example 1 are not shown in Table 2 above.

[0076] Test methods

[0077] Tensile strength of current collector samples: The composite current collector was cut into 150mm×10mm samples with a gauge length of 50mm. The gauge length of the sample was placed in the middle of the fixture, ensuring that the sample axis was consistent with the tensile direction. The sample was stretched at a constant speed of 200mm / min until the sample broke.

[0078] Battery sample preparation:

[0079] 1. Positive Electrode Preparation: NCM811 positive electrode material, Li6PS5Cl sulfide solid electrolyte, VGCF conductive agent, and SEBS binder were added to an organic solvent at a mass ratio of 80:20:2:2 and thoroughly mixed to prepare a positive electrode slurry with a solid content controlled at 70%. The positive electrode slurry was uniformly coated onto each positive electrode composite current collector, and then subjected to baking, rolling, slitting, and die-cutting processes to obtain individual positive electrode samples.

[0080] 2. Preparation of solid electrolyte membrane: Li6PS5Cl sulfide solid electrolyte and PTFE binder are mixed at a mass ratio of 98:2, dispersed evenly by high-speed shearing, and then subjected to hot rolling four times at a rolling temperature of 80℃ to obtain sulfide solid electrolyte.

[0081] 3. Negative Electrode Preparation: Third-generation silicon-carbon negative electrode material, Li6PS5Cl sulfide solid electrolyte, VGCF conductive agent, and NBR binder were added to an organic solvent at a mass ratio of 60:40:2:2 and thoroughly mixed to prepare a negative electrode slurry. The solid content was controlled at 45%. The negative electrode slurry was uniformly coated onto each negative electrode composite current collector sample, and then subjected to baking, rolling, slitting, and die-cutting processes to obtain individual negative electrode sheet samples.

[0082] 4. Solid-state battery assembly: Each positive electrode, each solid electrolyte membrane, and each negative electrode are sequentially stacked, hot-pressed, packaged, and isostatically pressed to assemble each solid-state battery sample.

[0083] Initial coulombic efficiency test of battery samples: At room temperature, each of the obtained all-solid-state batteries was charged and discharged at a rate of 0.1C. Initial coulombic efficiency = initial discharge capacity / initial charge capacity × 100%.

[0084] Cyclic performance test: At room temperature, each of the obtained all-solid-state batteries was cycled at a rate of 0.5C for 500 cycles to test the capacity retention of each all-solid-state battery sample.

[0085] The results of the above tests are shown in Table 3.

[0086] Table 3

[0087]

[0088] As can be seen from the above description, compared with the comparative examples, the embodiments of the present invention, by setting the polymer conductive layer 10, the first metal layer 21, the second metal layer 22, the first ion-conducting electron layer 31, and the second ion-conducting electron layer 32, enable the final composite current collector to exhibit excellent performance in terms of thermal stability, safety, electron and ion transport efficiency, and corrosion resistance. When the obtained composite current collector is used as the positive electrode current collector and the negative electrode current collector, respectively, and assembled into an all-solid-state battery, the corresponding battery exhibits excellent charge-discharge performance and long-cycle stability.

[0089] More specifically, in the various embodiments:

[0090] Comparing Examples 3 and 4 with Example 1, it can be seen that in the polymer conductive layer 10, by optimizing the weight ratio of the first polymer to the first conductive agent, the filling density of the first conductive agent can be maximized while maintaining the integrity of the polymer matrix, thereby further improving the distribution density of the formed conductive network, and finally obtaining a composite current collector with better mechanical properties and conductivity.

[0091] Comparing Examples 5 and 6 with Example 1, it can be seen that by optimizing the weight ratio of the solid electrolyte, the second polymer, and the second conductive agent in the first ion-conducting electronic layer 31 and the second ion-conducting electronic layer 32, the ion-conducting and electronic properties of the coating can be fully utilized, thereby significantly improving the overall performance of the resulting composite current collector.

[0092] Comparing Examples 7 and 8 with Example 1, it can be seen that by optimizing the D50 particle size of the solid electrolyte in the first ion-conducting electron layer 31 and the second ion-conducting electron layer 32, a more continuous ion conduction path can be formed. At the same time, it is also beneficial to the uniform dispersion between the solid electrolyte and the second polymer matrix and the second conductive agent. If the particle size of the solid electrolyte is too small, it is easy to cause agglomeration. Conversely, if the particle size is too large, the slurry will be unevenly dispersed and will easily cause rapid sedimentation.

[0093] Comparing Examples 9 and 10 with Example 1, it can be seen that by optimizing the thickness relationship of the polymer conductive layer 10, the first metal layer 21, the second metal layer 22, the first ion-conducting electron layer 31, and the second ion-conducting electron layer 32 in the final composite current collector, the overall performance of the composite current collector can be further optimized, and the long-cycle performance of the all-solid-state battery can be further improved.

[0094] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0095] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A composite current collector, characterized in that, The composite current collector includes: A polymer conductive layer (10) includes a first surface and a second surface disposed opposite to each other; On the first surface, a first metal layer (21) and a first ion-conducting electron layer (31) are sequentially disposed along a direction away from the polymer conductive layer (10). On the second surface, a second metal layer (22) and a second ion-conducting electron layer (32) are sequentially disposed along a direction away from the polymer conductive layer (10). The polymer conductive layer (10) contains a first polymer and a first conductive agent; both the first ion-conducting electron layer (31) and the second ion-conducting electron layer (32) contain a solid electrolyte, a second polymer and a second conductive agent.

2. The composite current collector according to claim 1, characterized in that, In the polymer conductive layer (10), The weight ratio of the first polymer to the first conductive agent is 1:(0.1~0.3); and / or, The first polymer is selected from one or more of polyimide, polyethylene terephthalate, polyethylene, and polypropylene; and / or, The first conductive agent is selected from one or more of vapor-grown carbon fibers, conductive carbon black SuperP, carbon nanotubes, graphene, and acetylene black.

3. The composite current collector according to claim 1 or 2, characterized in that, The first metal layer (21) and the second metal layer (22) are each independently an aluminum layer or a copper layer, and the density of the aluminum layer and the copper layer are each independently 95%~98%.

4. The composite current collector according to any one of claims 1 to 3, characterized in that, In the first ion-conducting electron layer (31) and the second ion-conducting electron layer (32), The weight ratio of the solid electrolyte, the second polymer, and the second conductive agent is independently 1:(0.02~0.1):(0.45~0.60); and / or, The solid electrolyte is an oxide solid electrolyte, and the D50 of the solid electrolyte is 100nm~300nm; and / or, The second polymer is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polymethyl methacrylate, polyethylene oxide, polyacrylonitrile, and polyvinyl alcohol; and / or, The second conductive agent is selected from one or more of the following: vapor-grown carbon fiber, conductive carbon black SuperP, carbon nanotubes, graphene, and acetylene black.

5. The composite current collector according to any one of claims 1 to 4, characterized in that, The total thickness of the composite current collector is 5μm~15μm; In the composite current collector, the thickness ratio of the first ion-conducting electron layer (31), the first metal layer (21), the polymer conductive layer (10), the second metal layer (22), and the second ion-conducting electron layer (32) is 1:(2~3):(3~4):(2~3):

1.

6. A method for preparing a composite current collector according to any one of claims 1 to 5, characterized in that, include: Step S1: The first polymer and the first conductive agent are prepared into a first slurry, the first slurry is coated to obtain a first wet film, and the first wet film is dried to obtain the polymer conductive layer (10). Step S2: Using magnetron sputtering, the first metal layer (21) and the second metal layer (22) are deposited on the first and second surfaces of the polymer conductive layer (10), respectively. Step S3: The solid electrolyte, the second polymer, and the second conductive agent are formulated into a second slurry. The second slurry is coated on the surface of the first metal layer (21) away from the polymer conductive layer (10) and the surface of the second metal layer (22) away from the polymer conductive layer (10), respectively, to form a second wet film and a third wet film. The second wet film and the third wet film are dried in a second process to form the first ion-conducting electron layer (31) and the second ion-conducting electron layer (32), respectively, thereby obtaining the composite current collector.

7. The method for preparing the composite current collector according to claim 6, characterized in that, The preparation process of the first slurry includes: the first polymer and the first solvent are first mixed to obtain a first adhesive solution with a mass concentration of 5 wt.% to 10 wt.%; the first conductive agent and the second solvent are second mixed to obtain a first suspension with a solid content of 25 wt.% to 30 wt.%; the first adhesive solution and the first suspension are third mixed to obtain the first slurry. The preparation process of the second slurry includes: the second polymer and the third solvent are mixed in a fourth process to obtain a second colloid with a mass concentration of 5 wt.% to 10 wt.%; the solid electrolyte, the second conductive agent and the fourth solvent are mixed in a fifth process to obtain a second suspension with a solid content of 45 wt.% to 50 wt.%; the second colloid and the second suspension are mixed in a sixth process to obtain the second slurry.

8. The method for preparing the composite current collector according to claim 7, characterized in that, The first mixture, the third mixture, the fourth mixture, and the sixth mixture are all carried out by stirring, and the stirring rate of each mixture is independently 1000 r / min to 2000 r / min, and the stirring time of each mixture is independently 30 min to 60 min; and / or, Both the second and fifth mixing processes are performed by ultrasonic dispersion, with each ultrasonic dispersion occurring independently at frequencies ranging from 80 Hz to 120 Hz and for durations of 30 ± 5 min; and / or, The first solvent, the second solvent, the third solvent, and the fourth solvent are each independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, and dimethyl sulfoxide; and / or, The temperature of the first drying and the second drying are each independently 60℃~80℃, and the time is each independently 12h~24h.

9. The method for preparing the composite current collector according to any one of claims 6 to 8, characterized in that, During the magnetron sputtering process, the vacuum level of the deposition chamber is 0.8 × 10⁻⁶. -4 Pa ~ 1.0 × 10 -4 Pa, argon flow rate of 40 sccm~60 sccm, operating pressure of 0.5 Pa~2 Pa, sputtering power of 70 W~200 W, sputtering time of 1 h~1.5 h, and substrate temperature of 40 °C~50 °C.

10. An all-solid-state battery, characterized in that, The all-solid-state battery includes at least one composite current collector as described in any one of claims 1 to 5.

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