Composite electrode, preparation method thereof and lithium ion battery

Abstract

The invention provides a composite electrode, a preparation method thereof and a lithium ion battery. The composite electrode comprises a current collecting net and electrode plates arranged on the two sides of the current collecting net. The current collecting net is provided with penetrating meshes; the electrode plates on the two sides of the current collecting net are in contact through meshes; the electrode plate comprises an electrode active material, a conductive agent and a binder; and the binder comprises a hot-melt binder. The fluidity of the hot-melt adhesive in the hot pressing process is utilized, so that the hot-melt adhesive fills the meshes of the current collecting net and is connected with the electrode plates on the two sides of the current collecting net, bonding of all functional layers is achieved, the distribution uniformity of an electrode active material and a conductive agent in the composite electrode is improved, the composite electrode with a more stable structure is formed, and the service life of the composite electrode is prolonged. The tortuosity and the resistivity of the composite electrode are reduced, and the thermal diffusivity, the rate capability and the cycling stability of the lithium ion battery are improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and more specifically, to a composite electrode and its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are increasingly being used in electric vehicles and energy storage, becoming the two major markets for lithium-ion batteries in this new era. Currently, battery manufacturing technology focuses on innovation in new materials and processes to enhance competitiveness in these two application areas. To meet market demands for high energy density in lithium-ion batteries, cathode materials are moving towards high-nickel content, while anode materials are shifting towards pure silicon-carbon and high-silicon-oxygen doping. However, issues such as safety, stability, and lifespan in applications have become challenges for material innovation. On the other hand, to achieve both economic efficiency and fast charging, thick electrode technology using graphite anode systems, combining long lifespan and high rate performance, has become another development focus. However, achieving fast charging and long cycle life with thick electrode technology requires overcoming kinetic bottlenecks, which poses a significant technical challenge for its industrialization.

[0003] In emerging battery manufacturing technologies, dry processing, distinct from wet-process battery manufacturing, is a key area of ​​research. Dry processing uses little or no solvent, significantly reducing energy consumption and solvent usage compared to wet processes, making it highly environmentally friendly. It also saves on solvent recycling costs and the need for extensive baking tunnels, lowering investment and factory land costs. Dry electrode manufacturing technology can produce thicker electrodes with higher compaction density, thereby increasing the energy density of lithium-ion batteries. However, the dry electrode fabrication process requires the use of conductive adhesive layers to bond the dry film to the current collector. This results in higher resistivity for thicker electrode films, and the increased thickness also increases electrode tortuosity. High compaction density leads to insufficient porosity, reducing the cycle stability and rate performance of lithium-ion batteries. Furthermore, insufficient precision in the dry electrode fabrication process can cause significant variations in electrode film thickness, leading to uneven polarization within the lithium-ion battery. This results in uneven thermal diffusion within the cell, increasing safety risks. Currently, solutions to these problems are lacking.

[0004] In summary, the research and development of a composite electrode with a compact and stable structure, low electrode resistivity, high porosity, and low tortuosity, as well as its preparation method, is of great significance for improving the cycle stability and rate performance of lithium-ion batteries. Summary of the Invention

[0005] The main objective of this application is to provide a composite electrode and its preparation method, as well as a lithium-ion battery, to solve the problems of uneven polarization, high resistivity, low porosity and large tortuosity of electrodes prepared by existing dry battery preparation processes, and the resulting poor rate performance and cycle stability of lithium-ion batteries.

[0006] To achieve the above objectives, this application provides a composite electrode comprising a current collector and electrode plates disposed on both sides of the current collector; the current collector has through-holes; the electrode plates on both sides of the current collector are in contact at the holes; the electrode plates comprise an electrode active material, a conductive agent, and a binder; the binder comprises a hot-melt binder.

[0007] Furthermore, the thickness of the current collector mesh is 20–100 μm, and the mesh size is 8–120 mesh; preferably, the mesh openings are arranged in an array; more preferably, the cross-section of the mesh openings is square, rectangular, or rhomboid; preferably, the cross-sectional area of ​​a single mesh opening is 0.03–6 mm². 2 The distance between two adjacent mesh openings is 0.02 to 0.1 mm; preferably, the material of the current collector mesh is selected from one or more of the group consisting of copper-nickel alloy, copper, nickel, aluminum and steel.

[0008] Further, the cross-section of the electrode sheet is square or rectangular; preferably, the thickness of the electrode sheet is 60-1000 μm; preferably, the weight ratio of electrode active material, conductive agent and binder in the electrode sheet is (95-98):(0.4-2):(0.8-3).

[0009] Furthermore, the adhesive also includes polytetrafluoroethylene; preferably, the weight ratio of hot-melt adhesive to polytetrafluoroethylene is (30-50):(50-70).

[0010] Further, the melting temperature of the hot-melt adhesive is ≥80℃; preferably, the softening temperature of the hot-melt adhesive is lower than its melting temperature, and the absolute value of the difference between the two is ≥20℃; preferably, the melting temperature of the hot-melt adhesive is 80~180℃, and the softening temperature is 60~150℃; preferably, the hot-melt adhesive relative to Li / Li + The voltage window of the electrode pair is 0-5V; preferably, the hot-melt adhesive is selected from one or more of the group consisting of polyethylene, polyamide, polyurethane, butyl rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer, and polyethylene oxide; more preferably, the hot-melt adhesive is polyethylene, and its weight-average molecular weight is 50,000 to 300,000; or, the hot-melt adhesive is ethylene-vinyl acetate copolymer, and its weight-average molecular weight is 70,000 to 120,000; or, the hot-melt adhesive is polyamide, and its weight-average molecular weight is 6,000 to 120,000.

[0011] Furthermore, the electrode active material is a positive electrode active material or a negative electrode active material; preferably, the positive electrode active material is selected from one or more of the group consisting of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and lithium cobalt oxide; preferably, the negative electrode active material is selected from one or more of the group consisting of graphite, silicon oxide and silicon carbon.

[0012] Furthermore, the conductive agent is selected from one or more of the group consisting of conductive carbon black, carbon nanotubes, graphene, conductive carbon nanofibers, conductive graphite, and porous carbon.

[0013] To achieve the above objectives, another aspect of this application provides a method for preparing the composite electrode provided in this application. The method includes: step S1, preparing an electrode sheet containing an electrode active material, a conductive agent, and a binder; wherein the binder includes a hot-melt binder; step S2, alternately stacking the electrode sheet and a current collector to obtain a stacked structure, wherein both sides of the stacked structure are electrode sheets; wherein the current collector has through-holes; and step S3, hot-pressing the stacked structure to obtain a composite electrode.

[0014] Further, step S1 includes: step S-A1, mixing the electrode active material, conductive agent and binder to obtain a first mixture; wherein the binder includes a hot-melt binder and polytetrafluoroethylene; step S-A2, fibrousizing the first mixture to obtain fibrous powder; step S-A3, pressing the fibrous powder to obtain an electrode sheet; preferably, the linear velocity of the fibrous treatment is 20-120 m / s, and the time is 10 s-30 min.

[0015] Furthermore, the weight ratio of electrode active material, conductive agent and binder is (95-98):(0.4-2):(0.8-3).

[0016] Furthermore, in the adhesive, the weight ratio of hot-melt adhesive to polytetrafluoroethylene is (30-50):(50-70).

[0017] Further, in step S3, the pressure applied to the laminated structure during the hot pressing process is 1 to 15 MPa; the temperature of the hot pressing process is 80 to 200°C, and the time is 20 to 300 s; preferably, the temperature of the hot pressing process is 80 to 150°C, and the time is 20 to 90 s.

[0018] Furthermore, hot pressing is performed using a flat plate hot press or a roller press; preferably, a flat plate hot press is used for hot pressing, and the pressure applied to the laminated structure is 1-15 MPa; preferably, a roller press is used for hot pressing, and the roller diameter of the pressure roller in the roller press is 400-1000 mm; the linear speed of the pressure roller is ≤80 m / min, preferably 2.5-40 m / min; the pressure applied by the pressure roller to the laminated structure is 2-15 MPa.

[0019] Another aspect of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode and / or the negative electrode is the composite electrode provided in this application.

[0020] Compared to traditional methods that involve hot-pressing two electrode sheets with a current collector pre-coated with a conductive adhesive layer to form a composite electrode, this application provides a composite electrode comprising a current collector mesh and electrode sheets disposed on both sides of the current collector mesh. Each electrode sheet comprises an electrode active material, a conductive agent, and a hot-melt adhesive. The current collector mesh has through-holes. During the hot-pressing process, the hot-melt adhesive in the electrode sheets softens and melts upon heating, becoming a fluid molten state. This molten adhesive flows along and passes through the mesh of the current collector mesh, connecting the electrode sheets on both sides. After cooling and solidification, the electrode sheets on both sides of the current collector mesh can contact each other at the mesh openings, effectively bonding the components, increasing the cohesion of the composite electrode, reducing its interfacial resistivity, and improving its electronic conductivity and ion transport performance, thereby enabling it to better utilize its electrochemical capacity. Meanwhile, the mesh on the current collector allows for the free flow of electrolyte and lithium ions inside the composite electrode, thereby effectively improving the lithium ion transport efficiency, increasing the electrolyte penetration path, and reducing the tortuosity of the composite electrode.

[0021] In summary, the composite electrode provided in this application has a stable electrode structure, low tortuosity and resistivity, and high electrolyte permeability. Its application in lithium-ion batteries can improve the cycle stability and rate performance of lithium-ion batteries. At the same time, it can also improve the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, improve the uniformity of internal polarization of lithium-ion batteries, thereby improving the thermal diffusion capability of lithium-ion batteries and improving the safety performance of lithium-ion batteries. 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 application will now be described in detail with reference to the embodiments.

[0023] As described in the background section, existing composite electrodes fabricated using dry-process battery manufacturing techniques suffer from high resistivity, low porosity, and poor cycle stability, rate performance, and safety performance of lithium-ion batteries made from them. To address these technical problems, a first aspect of this application provides a composite electrode comprising a current collector and electrode plates disposed on both sides of the current collector; the current collector has through-holes; the electrode plates on both sides of the current collector are in contact through the through-holes; the electrode plates comprise an electrode active material, a conductive agent, and a binder; the binder comprises a hot-melt binder.

[0024] Compared to traditional methods that involve hot-pressing two electrode sheets with a current collector pre-coated with a conductive adhesive layer to form a composite electrode, this application provides a composite electrode comprising a current collector mesh and electrode sheets disposed on both sides of the current collector mesh. Each electrode sheet comprises an electrode active material, a conductive agent, and a hot-melt adhesive. The current collector mesh has through-holes. During the hot-pressing process, the hot-melt adhesive in the electrode sheets softens and melts upon heating, becoming a fluid molten state. This molten adhesive flows along and passes through the mesh of the current collector mesh, connecting the electrode sheets on both sides. After cooling and solidification, the electrode sheets on both sides of the current collector mesh can contact each other at the mesh openings, effectively bonding the components, increasing the cohesion of the composite electrode, reducing its interfacial resistivity, and improving its electronic conductivity and ion transport performance, thereby enabling it to better utilize its electrochemical capacity. Meanwhile, the mesh on the current collector allows for the free flow of electrolyte and lithium ions inside the composite electrode, thereby effectively improving the lithium ion transport efficiency, increasing the electrolyte penetration path, and reducing the tortuosity of the composite electrode.

[0025] In summary, the composite electrode provided in this application has a stable electrode structure, low tortuosity and resistivity, and high electrolyte permeability. Its application in lithium-ion batteries can improve the cycle stability and rate performance of lithium-ion batteries. At the same time, it can also improve the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, improve the uniformity of internal polarization of lithium-ion batteries, thereby improving the thermal diffusion capability of lithium-ion batteries and improving the safety performance of lithium-ion batteries.

[0026] In a preferred embodiment, the thickness of the current collector mesh is 20–100 μm, and the mesh size is 8–120 mesh. The thickness and mesh size of the current collector mesh include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving the electronic conductivity and ion transport performance of the composite electrode, enhancing the structural stability of the composite electrode, and also for improving the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, thereby improving the uniformity of internal polarization of the lithium-ion battery. This, in turn, is beneficial for improving the thermal diffusion capability, rate performance, and cycle performance of the lithium-ion battery. Specifically, the thickness of the current collector mesh can be 20 μm, 40 μm, 50 μm, 70 μm, 80 μm, 90 μm, or 100 μm; the mesh size of the current collector mesh can be 8 mesh, 15 mesh, 20 mesh, 40 mesh, 50 mesh, 65 mesh, 80 mesh, 90 mesh, 110 mesh, 110 mesh, or 120 mesh.

[0027] In a preferred embodiment, the mesh is arranged in an array. Compared to other methods (such as random arrangement), the array arrangement allows the hot-melt binder to flow and pass through the mesh uniformly, and to be more evenly distributed on the surface of adjacent electrode sheets. This improves the uniformity of the pore structure distribution of the composite electrode, allowing the electrolyte to penetrate more evenly during the charging and discharging process of the lithium-ion battery. Consequently, it improves the cycle stability and rate performance of the lithium-ion battery. Furthermore, it improves the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, enhances the uniformity of internal polarization of the lithium-ion battery, thereby improving the thermal diffusion capability of the lithium-ion battery and ultimately enhancing its safety performance.

[0028] In order to facilitate the flow of molten hot-melt adhesive along and through the mesh of the manifold, in a preferred embodiment, the cross-section of the mesh is square, rectangular or rhomboid.

[0029] In a preferred embodiment, the cross-sectional area of ​​a single mesh opening is 0.03–6 mm². 2 The distance between two adjacent mesh openings (i.e., the diameter of the metal wires constituting the current collector) is 0.02–0.1 mm. The cross-sectional area of ​​a single mesh opening and the distance between two adjacent mesh openings include, but are not limited to, the above range. Limiting them to the above range facilitates the flow of molten hot-melt binder along and through the mesh openings of the current collector, which is beneficial for improving the electrolyte permeability, enhancing the permeability of the composite electrode, reducing the tortuosity and resistivity of the composite electrode, thereby improving the cycle stability and rate performance of the lithium-ion battery. At the same time, it is also beneficial for improving the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, improving the uniformity of internal polarization of the lithium-ion battery, thereby improving the thermal diffusion capability of the lithium-ion battery.

[0030] To facilitate the flow and passage of the molten hot-melt binder along the mesh of the current collector, thereby further improving the electrolyte permeability, reducing the tortuosity and resistivity of the composite electrode, and enhancing the uniformity of internal polarization in the lithium-ion battery, thus further improving the cycle stability, rate performance, and safety performance of the lithium-ion battery, preferably, the cross-section of the mesh is square with a side length of 0.2–5 mm, for example, a square with a cross-section of 0.5 mm × 0.5 mm; or, the cross-section of the mesh is rectangular with a length and width of 0.2–5 mm, for example, a rectangle with a cross-section of 0.2 mm × 0.5 mm, 0.5 mm × 1 mm, 1 mm × 2 mm, 2 mm × 3 mm, or 3 mm × 5 mm; or, the cross-section of the mesh is rhomboid with a side length of 0.2–5 mm, for example, a rhomboid with a cross-section of 0.5 mm × 1 mm or 1 mm × 2 mm.

[0031] In a preferred embodiment, the current collector is made of one or more materials, including but not limited to copper-nickel alloys, copper, nickel, aluminum, and steel. Compared to other materials, current collectors made of the above materials are beneficial for improving the stability of the composite electrode, enhancing its ion transport capacity and conductivity, and thus improving the cycle stability and rate performance of the lithium-ion battery.

[0032] To improve the consistency and structural stability of the fabricated composite electrode, in a preferred embodiment, the cross-section of the electrode sheet is square or rectangular.

[0033] In a preferred embodiment, the thickness of the electrode sheet is 60–1000 μm. The thickness of the electrode sheet includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the structural stability of the composite electrode, enhancing its electronic conductivity and ion transport performance, and simultaneously increasing the energy density of the resulting lithium-ion battery.

[0034] In a preferred embodiment, the weight ratio of electrode active material, conductive agent, and binder in the electrode sheet is (95-98):(0.4-2):(0.8-3). The weight ratio of electrode active material, conductive agent, and binder includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the ion transport capacity and conductivity of the composite electrode, thereby improving the cycle stability and rate performance of the resulting lithium-ion battery.

[0035] Polytetrafluoroethylene (PTFE) possesses fibrous properties; under certain shear strength or temperature, its original crystalline structure undergoes a phase transformation, converting primary particles into fibrous filaments and improving the film-forming properties of the fibrous powder, thus facilitating compression molding to obtain electrode sheets. To further enhance the bonding strength between the electrode active material and the conductive agent, construct a more continuous conductive network, and further improve the structural stability of the composite electrode, in a preferred embodiment, the binder also includes PTFE.

[0036] To further enhance the interaction between the hot-melt adhesive and polytetrafluoroethylene (PTFE), enable PTFE to better utilize its fibrous properties, further improve the bonding strength between the electrode active material and the conductive agent, construct a more continuous conductive network, and further improve the structural stability of the composite electrode, preferably, the weight ratio of the hot-melt adhesive to PTFE is (30-50):(50-70).

[0037] In a preferred embodiment, the melting temperature of the hot-melt binder is ≥80°C. The melting temperature of the hot-melt binder includes, but is not limited to, the above range. Limiting it to the above range helps to suppress the melting of the hot-melt binder during the preparation of the electrode sheet, and helps it to play a melting and bonding role during hot pressing, resulting in a more stable composite electrode.

[0038] In order to further suppress the melting of the hot-melt adhesive during the preparation of the electrode sheet and promote its melting and bonding function during hot pressing, preferably, the softening temperature of the hot-melt adhesive is lower than its melting temperature, and the absolute value of the difference between the two is ≥20℃.

[0039] In order to further suppress the melting of the hot-melt binder during the preparation of the electrode sheet and to further promote its melting and bonding function during subsequent hot pressing, preferably, the melting temperature of the hot-melt binder is 80-180°C and the softening temperature is 60-150°C.

[0040] The voltage window of a hot-melt adhesive refers to the voltage window of the hot-melt adhesive relative to lithium metal (Li / Li). + The voltage range at which it can exist stably under the electrochemical potential of ) . In a preferred embodiment, the hot-melt binder relative to Li / Li + The voltage window of the electrode pair is 0–5V. The voltage window of the hot-melt binder includes, but is not limited to, the above range. Limiting it to the above range helps to suppress the structural damage of the hot-melt binder during the charging and discharging process of lithium-ion batteries, improves the structural stability of the composite electrode, and thus helps to improve the safety of lithium-ion batteries.

[0041] In a preferred embodiment, the hot-melt binder includes, but is not limited to, one or more of the following groups: polyethylene, polyamide, polyurethane, butyl rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer, and polyethylene oxide. Compared to other types, the aforementioned hot-melt binders have excellent adhesion properties, which helps to improve the bond strength between the electrode active material and the conductive agent, thereby improving the cohesion of the composite electrode and obtaining a more stable composite electrode. This, in turn, helps to improve the cycle stability and rate performance of the lithium-ion battery. Furthermore, it helps to improve the uniformity of the distribution of the electrode active material and the conductive agent in the composite electrode, and improves the uniformity of the internal polarization of the lithium-ion battery, thereby improving the thermal diffusion capability of the lithium-ion battery and ultimately enhancing its safety performance.

[0042] To further improve the bonding strength between the electrode active material and the conductive agent, further enhance the cohesion of the composite electrode, and obtain a more structurally stable composite electrode, thereby further improving the cycle stability and rate performance of the lithium-ion battery, and simultaneously further improving the uniformity of the distribution of the electrode active material and the conductive agent in the composite electrode, improving the uniformity of internal polarization of the lithium-ion battery, and thus further improving the thermal diffusion capability of the lithium-ion battery, preferably, the hot-melt binder is polyethylene with a weight-average molecular weight of 50,000 to 300,000; or, the hot-melt binder is ethylene-vinyl acetate copolymer with a weight-average molecular weight of 70,000 to 120,000; or, the hot-melt binder is polyamide with a weight-average molecular weight of 6,000 to 120,000.

[0043] The electrode active material in this application can be any type of positive or negative electrode active material commonly used in the art. In a preferred embodiment, the electrode active material is either a positive or negative electrode active material.

[0044] In order to improve the ion transport capacity and conductivity of the composite electrode, and further improve the energy density, cycle stability and rate performance of lithium-ion batteries, preferably, the positive electrode active material includes, but is not limited to, one or more of the group consisting of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and lithium cobalt oxide; the negative electrode active material includes, but is not limited to, one or more of the group consisting of graphite, silicon oxide and silicon carbon.

[0045] The conductive agent used in this application can be any type commonly used in the art. In a preferred embodiment, the conductive agent includes, but is not limited to, one or more of the group consisting of conductive carbon black, carbon nanotubes, graphene, conductive carbon nanofibers, conductive graphite, and porous carbon. Compared to other types, using the above-mentioned conductive agents is beneficial for improving the conductivity of the composite electrode, improving ion transport capability, and reducing the resistance of the composite electrode, thereby improving the cycle stability and rate performance of the lithium-ion battery.

[0046] The second aspect of this application also provides a method for preparing the composite electrode provided in this application. The method for preparing the composite electrode includes: step S1, preparing an electrode sheet containing an electrode active material, a conductive agent, and a binder; wherein the binder includes a hot-melt binder; step S2, alternately stacking the electrode sheet and a current collector to obtain a stacked structure, wherein both sides of the stacked structure are electrode sheets; wherein the current collector has through-holes; step S3, hot-pressing the stacked structure to obtain the composite electrode.

[0047] Compared to traditional methods that combine two dry-prepared electrode sheets with a current collector pre-coated with a conductive adhesive layer via hot pressing, the composite electrode preparation method provided in this application can produce an electrode sheet containing an electrode active material, a conductive agent, and a hot-melt binder through step S1. The introduction of the hot-melt binder facilitates its melting and bonding during the subsequent hot pressing process. In step S2, by alternately stacking the electrode sheets with a current collector having the specific structure described above, a laminated structure with the specific structure can be obtained, thereby facilitating the bonding of the current collector and its adjacent electrode sheets during the subsequent hot pressing process. In step S3, during the hot-pressing process of the laminated structure, the hot-melt binder in the electrode sheet softens and melts under heat, becoming a fluid molten state. On the one hand, it can play a bonding role, bonding the electrode active material and conductive agent inside the electrode sheet, improving the bonding force between the components, thereby improving the cohesion of the composite electrode and maximizing its electrochemical capacity. On the other hand, by utilizing the fluidity of the molten hot-melt binder during the hot-pressing process, the molten hot-melt binder in the area of ​​the electrode sheet near the current collector can fill the mesh of the current collector and connect the electrode sheets on both sides of the current collector, thereby achieving the bonding of each functional layer in the laminated structure, forming a structurally stable composite electrode. At the same time, it can significantly reduce the overall thickness of the composite electrode while maintaining the same electrode active material areal density.

[0048] In summary, the composite electrode preparation method provided in this application can improve the porosity of the composite electrode, reduce its resistivity, increase the electrolyte permeability to the composite electrode, and enhance its permeability characteristics, thereby improving the cycle stability and rate performance of the lithium-ion battery. Furthermore, it can improve the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, enhance the uniformity of internal polarization of the lithium-ion battery, thereby improving the thermal diffusion capability of the lithium-ion battery and ultimately improving its safety performance.

[0049] In a preferred embodiment, step S1 includes: step S-A1, mixing the electrode active material, conductive agent, and binder to obtain a first mixture; wherein the binder includes a hot-melt binder and polytetrafluoroethylene (PTFE); step S-A2, subjecting the first mixture to a fibrous treatment to obtain a fibrous powder; and step S-A3, pressing the fibrous powder to obtain an electrode sheet. In step S-A2, the fibrous treatment of the first mixture containing the electrode active material, conductive agent, hot-melt binder, and PTFE obtained in step S-A1 yields a fibrous powder. The PTFE introduced into the first mixture has fibrous properties; under certain shear strength or temperature, it can undergo a phase transformation of its original crystal structure, changing it from primary particles to fibrous filaments. This improves the degree of fibrous formation of the fibrous powder, thereby enhancing its film-forming properties and facilitating subsequent pressing to obtain the electrode sheet.

[0050] In a preferred embodiment, in step S-A3, the fibrous powder is pressed and molded using the dry electrode film preparation equipment disclosed in Chinese patent application CN202410058114.5 to obtain an electrode sheet. In the dry electrode film preparation equipment, the first roller has a diameter of 10–30 cm, a pressure of 8 kN–80 kN, a rotation speed ≤1800 rpm, and a temperature of 50–200°C; the second roller has a diameter of 5–20 cm, a pressure of 5 kN–70 kN, a rotation speed ≤500–2000 rpm, and a temperature of 50–200°C; and the third roller has a diameter of 15–60 cm, a pressure of 10 kN–100 kN, a rotation speed ≤500–2000 rpm, and a temperature of 0–150°C.

[0051] In a preferred embodiment, step S-A1 includes: mixing the electrode active material with a conductive agent to obtain a second mixture; mixing the second mixture with a binder to obtain a third mixture; and step S-A2 includes: subjecting the third mixture to a fibrous treatment to obtain a fibrous powder. First, the electrode active material and the conductive agent are mixed in a second mixture, and then the second mixture is mixed with the binder in a third mixture. This improves the dispersibility of the conductive agent and the binder, and enhances the degree of fibrous formation in the subsequently obtained fibrous powder and the conductivity of the electrode sheet.

[0052] In a preferred embodiment, step S-A1 further includes: mixing the second mixture with a hot-melt binder in a fourth mixing to obtain a fourth mixture; mixing the fourth mixture with polytetrafluoroethylene (PTFE) in a fifth mixing to obtain a fifth mixture; and step S-A2 includes: subjecting the fourth mixture to a fibrous treatment to obtain a fibrous powder. Compared to mixing the binder containing the hot-melt binder and PTFE with the second mixture in a single third mixing, adding the hot-melt binder and PTFE in two separate mixing steps improves the dispersibility of the binder components. Furthermore, the subsequent addition of PTFE in the fifth mixing allows PTFE to better utilize its fibrous properties, thereby increasing the degree of fibrous formation in the fibrous powder and facilitating subsequent pressing and molding to obtain electrode sheets.

[0053] To improve the efficiency of the fiberization process, further enhance the degree of fiberization of the fiberized powder, and further improve the film-forming properties of the fiberized powder, preferably, the linear velocity of the fiberization process is 20-120 m / s, and the time is 10-1800 s.

[0054] In a preferred embodiment, the weight ratio of the electrode active material, conductive agent, and binder is (95-98):(0.4-2):(0.8-3). This weight ratio includes, but is not limited to, the range described above. Limiting it to this range facilitates the melting and bonding of the binder during subsequent hot-pressing, improves the ion transport capacity and conductivity of the composite electrode, thereby enhancing the cycle stability and rate performance of the lithium-ion battery. It also improves the utilization rate of each raw material and reduces costs.

[0055] In a preferred embodiment, the weight ratio of the hot-melt adhesive to polytetrafluoroethylene (PTFE) in the binder is (30-50):(50-70). This weight ratio includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the interaction between the hot-melt adhesive and PTFE, for allowing PTFE to exhibit its fibrous properties, and for the hot-melt adhesive to play a melting and bonding role in subsequent hot-pressing processes. This results in a more stable composite electrode structure and also improves the utilization rate of the adhesive, reducing costs.

[0056] In a preferred embodiment, in step S3, the pressure applied to the laminated structure during the hot pressing process is 1–15 MPa; the hot pressing temperature is 80–200°C; and the time is 20–300 s. The pressure applied to the laminated structure during the hot pressing process, as well as the temperature and time, are not limited to the above ranges. Limiting them to these ranges helps improve the efficiency of the hot pressing process, promotes the melting and activation of the hot-melt binder, thereby resulting in a more stable composite electrode and improving production efficiency.

[0057] To further improve the efficiency of hot pressing, further promote the melting of the hot-melt binder and enable it to play its role, thereby further improving the structural stability of the prepared composite electrode, preferably, the hot pressing temperature is 80-150℃ and the time is 20-90s.

[0058] To further improve the efficiency of hot pressing, further promote the melting and function of the hot-melt binder, and further improve the structural stability of the resulting composite electrode, it is preferable to use a flat plate hot pressing device or a roller pressing device for hot pressing.

[0059] To further improve the efficiency of hot pressing, further promote the melting and function of the hot-melt binder, and further improve the structural stability of the resulting composite electrode, more preferably, a flat plate hot pressing device is used for hot pressing, and the pressure applied to the laminated structure is 1-15 MPa; or, a roller pressing device is used for hot pressing, and the roller diameter of the roller in the roller pressing device is 400-1000 mm; the linear speed of the roller is ≤80 m / min, and the preferred linear speed of the roller is 2.5-40 m / min; the pressure applied by the roller to the laminated structure is 2-15 MPa.

[0060] A third aspect of this application also provides a lithium-ion battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes, wherein the positive and / or negative electrodes are the composite electrodes provided in this application.

[0061] The composite electrode provided in this application has a stable electrode structure, low tortuosity and resistivity, and high electrolyte permeability. When used as a positive electrode and / or negative electrode in lithium-ion batteries, it can improve the cycle stability and rate performance of lithium-ion batteries. At the same time, it can also improve the uniformity of the distribution of electrode active materials and conductive agents in the composite electrode, improve the uniformity of internal polarization of lithium-ion batteries, thereby improving the thermal diffusion capability of lithium-ion batteries and improving the safety performance of lithium-ion batteries.

[0062] 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.

[0063] Example 1

[0064] A method for preparing a composite negative electrode includes the following steps:

[0065] (1) Graphite anode material, conductive carbon black (SP), ethylene-vinyl acetate copolymer (weight-average molecular weight of 70,000, melting temperature of 85°C), and polytetrafluoroethylene (weight-average molecular weight of 10 million) are mixed in a weight ratio of 97:1:1:1 to obtain a mixture; the mixture is sheared and fiberized at a linear velocity of 30 m / s for 10 min to obtain a fiberized powder; the fiberized powder is placed in a dry electrode film preparation device (the device disclosed in Chinese patent application CN202410058114.5) for pressing and molding to obtain an electrode sheet; step (1) is repeated to obtain several electrode sheets; wherein the areal density of the electrode sheet is 320 g / m 2 ;

[0066] (2) A copper current collector with a size of 70mm×100mm×30μm is placed between two electrode plates prepared in step (1) to obtain a stacked structure, wherein the cross-section of the copper current collector is a rhombus of 0.5mm×1mm and the distance between two adjacent meshes is 0.025mm.

[0067] (3) The laminated structure obtained in step (2) was hot-pressed at 150°C for 30s using a flat plate hot press (Dongguan Kerui Instrument Technology Co., Ltd., REE601413-10) to obtain a composite negative electrode. The pressure per unit area applied to the laminated structure by the flat plate hot press was 3MPa.

[0068] Example 2

[0069] The difference from Example 1 is that in step (1), the weight ratio of graphite anode material, SP, ethylene-vinyl acetate copolymer and polytetrafluoroethylene is 98:1:0.4:0.6; the remaining steps are the same as in Example 1.

[0070] Example 3

[0071] The difference from Example 1 is that in step (1), the weight ratio of graphite anode material, SP, ethylene-vinyl acetate copolymer and polytetrafluoroethylene is 95:2:1:2; the remaining steps are the same as in Example 1.

[0072] Example 4

[0073] The difference from Example 1 is that in step (1), the weight ratio of ethylene-vinyl acetate copolymer to polytetrafluoroethylene is 3:7; the remaining steps are the same as in Example 1.

[0074] Example 5

[0075] The difference from Example 1 is that in step (1), the weight ratio of ethylene-vinyl acetate copolymer and polytetrafluoroethylene is 1:1; the remaining steps are the same as in Example 1.

[0076] Example 6

[0077] The difference from Example 1 is that in step (1), the weight ratio of ethylene-vinyl acetate copolymer to polytetrafluoroethylene is 3:2; the remaining steps are the same as in Example 1.

[0078] Example 7

[0079] The difference from Example 1 is that in step (1), the linear velocity of the shearing fiberization process is 120 m / s and the time is 10 s; the remaining steps are the same as in Example 1.

[0080] Example 8

[0081] The difference from Example 1 is that in step (1), the linear velocity of the shearing fiberization process is 10 m / s and the time is 10 min; the remaining steps are the same as in Example 1.

[0082] Example 9

[0083] The difference from Example 1 is that in step (3), the temperature of hot pressing is 80°C and the time is 300s. The pressure per unit area applied by the flat plate hot press to the laminated structure obtained in step (2) is 15MPa. The remaining steps are the same as in Example 1.

[0084] Example 10

[0085] The difference from Example 1 is that in step (3), the temperature of hot pressing is 200°C and the time is 20s. The pressure per unit area applied by the flat plate hot press to the laminated structure obtained in step (2) is 1MPa. The remaining steps are the same as in Example 1.

[0086] Example 11

[0087] The difference from Example 1 is that in step (3), the temperature of the hot pressing treatment is 60°C and the time is 15s; the remaining steps are the same as in Example 1.

[0088] Example 12

[0089] The difference from Example 1 is that in step (3), the flat plate hot press applies a unit area pressure of 0.5 MPa to the laminated structure obtained in step (2); the remaining steps are the same as in Example 1.

[0090] Example 13

[0091] The difference from Example 1 is that in step (1), polyethylene (weight average molecular weight of 50,000 and melting temperature of 100°C) of equal weight is used instead of the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0092] Example 14

[0093] The difference from Example 1 is that in step (1), polyethylene (weight average molecular weight of 300,000 and melting temperature of 120°C) of equal weight is used instead of the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0094] Example 15

[0095] The difference from Example 1 is that in step (1), an equal weight of polyamide (weight-average molecular weight of 0.6 million and melting temperature of 100°C) is used to replace the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0096] Example 16

[0097] The difference from Example 1 is that in step (1), an equal weight of polyamide (weight-average molecular weight of 120,000 and melting temperature of 110°C) is used to replace the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0098] Example 17

[0099] The difference from Example 1 is that in step (1), an equal weight of styrene-butadiene-styrene block copolymer (weight-average molecular weight of 100,000 and melting temperature of 140°C) is used to replace the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0100] Example 18

[0101] The difference from Example 1 is that in step (1), an equal weight of polyurethane (weight-average molecular weight of 200,000 and melting temperature of 140°C) is used to replace the ethylene-vinyl acetate copolymer in Example 1; the remaining steps are the same as in Example 1.

[0102] Example 19

[0103] A method for preparing a composite positive electrode includes the following steps:

[0104] (1) The positive electrode active material NCM811, conductive carbon black (SP), ethylene-vinyl acetate copolymer (weight average molecular weight of 70,000, melting temperature of 85°C) and polytetrafluoroethylene (weight average molecular weight of 10 million) are mixed in a weight ratio of 96:1:1:2 to obtain a mixture; the mixture is sheared and fiberized at a linear velocity of 40 m / s for 15 min to obtain a fiberized powder; the fiberized powder is placed in a dry electrode film preparation equipment (the equipment disclosed in Chinese patent application CN202410058114.5) for pressing and molding to obtain an electrode sheet; step (1) is repeated to obtain several electrode sheets;

[0105] (2) Place an aluminum current collector with a size of 200mm×1000mm×35μm between two electrode plates prepared in step (1) to obtain a stacked structure, wherein the cross-section of the aluminum current collector is a rhombus of 1mm×1mm and the distance between two adjacent meshes is 0.03mm.

[0106] (3) The laminated structure obtained in step (2) is hot-pressed at 100°C using a roller press to obtain a composite positive electrode. The roller diameter of the roller in the roller press is 800 mm, the linear speed of the roller is 5 m / min, and the pressure applied by the roller to the laminated structure is 12 MPa.

[0107] Comparative Example 1

[0108] The difference from Example 1 is that an equal weight of sodium carboxymethyl cellulose adhesive (weight average molecular weight of 160) is used to replace the hot-melt adhesive ethylene-vinyl acetate copolymer in Example 1, while the remaining steps are the same as in Example 1.

[0109] Comparative Example 1 could not obtain a stable negative electrode structure, and the electrode plates on both sides of the copper current collector were prone to detachment, making performance testing impossible.

[0110] Comparative Example 2

[0111] The difference from Example 1 is that a 10μm copper foil without holes and with conductive adhesive layers on both sides is used instead of the copper current collector in Example 1, wherein the thickness of the conductive adhesive layer is 1μm; the remaining steps are the same as in Example 1.

[0112] Comparative Example 3

[0113] A method for preparing a negative electrode includes the following steps:

[0114] Graphite anode material, SP, styrene-butadiene rubber binder, and carboxymethyl cellulose were mixed in a weight ratio of 96.5:1:1.5:1 to obtain an anode slurry. The anode slurry was coated onto a 10 μm thick copper foil and dried at 80°C to obtain an anode sheet. Subsequently, it was rolled to obtain a compaction density of 1.6 g / cm³. 3 The negative electrode sheet; wherein, the areal density of the negative electrode active material layer is 320 g / m². 2 .

[0115] The porosity, resistivity, liquid phase ion impedance, and tortuosity of the composite negative electrode prepared in Examples 1 to 18, the composite positive electrode prepared in Example 19, and the negative electrode sheets prepared in Comparative Examples 1 to 3 of this application were tested.

[0116] The above test methods are as follows: the effective porosity of the composite electrode is characterized by the electrolyte absorption rate; the resistivity of the composite electrode is measured using a membrane resistance meter (Hangzhou Chuanyuan Technology Co., Ltd., TT-ACCF-GI); the liquid phase ionic impedance and tortuosity are tested using an electrode tortuosity meter (Yuaneng Technology (Xiamen) Co., Ltd., EIC2400M), with an EIS test frequency of 100kHz~1Hz, and the tortuosity of the electrode is calculated according to the formula shown in equation (I). , (I), where, R ion Let A be the liquid-phase ion impedance and A be the area of ​​the composite electrode. The electrolyte conductivity is 8.7 MS / cm. d represents the porosity of the composite electrode, and d represents the thickness of the composite electrode.

[0117] The test results are shown in Table 1.

[0118] Table 1

[0119]

[0120] The composite negative electrode prepared in Examples 1 to 18 and the negative electrode prepared in Comparative Examples 1 to 3 were used as negative electrodes, respectively; lithium iron phosphate positive electrode was used as positive electrode, 1 mol / L lithium hexafluorophosphate (solvent is ethylene carbonate and methyl ethyl carbonate, with a volume ratio of 3:7) was used as electrolyte, and commercial boehmite-coated polypropylene / polyethylene composite membrane was used as membrane to assemble a 2Ah soft-pack lithium-ion battery.

[0121] Using the composite positive electrode prepared in Example 19 as the positive electrode, the graphite negative electrode as the negative electrode, 1 mol / L lithium hexafluorophosphate (the solvents are ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7) as the electrolyte, and a commercial boehmite-coated polypropylene / polyethylene composite membrane as the separator, a 2Ah soft-pack lithium-ion battery was assembled.

[0122] The following performance tests were performed on the lithium-ion batteries assembled from all the embodiments and comparative examples described above:

[0123] (1) The test conditions for the first charge specific capacity and the first coulombic efficiency (first efficiency) are as follows: constant current and constant voltage charging at a rate of 0.2C, cutoff rate of 0.05C, and voltage range of 0 to 3.65V;

[0124] (2) The impedance test conditions are as follows: discharge to 50% SOC, that is, discharge the lithium-ion battery from the fully charged state (100% SOC) to the level where its remaining capacity is 50%; SOC represents the ratio of the remaining capacity of the lithium-ion battery to its capacity when fully charged;

[0125] (3) The test conditions for the discharge capacity retention rate at different rates are as follows: at 25℃ and a voltage range of 2.5~3.65V, constant current discharge is performed at rates of 0.2C, 0.5C, 1C, 2C and 3C respectively, and the discharge capacity is recorded. The ratio of the discharge capacity at different rates to the discharge capacity at 0.2C is calculated, which is the discharge capacity retention rate at different rates.

[0126] (4) The test conditions for capacity retention are as follows: 25℃, 1C rate, voltage range 2.5~3.65V, 0.05C cutoff, 500 cycles.

[0127] The test results are shown in Table 2.

[0128] Table 2

[0129]

[0130] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0131] Comparing Example 1 and Comparative Examples 1 and 2, and referring to the data in Table 2, it can be seen that using the current collector mesh provided in this application to replace the traditional current collector (such as copper foil), and in conjunction with the molten binder provided in this application, can effectively bond the components in the composite electrode, improve the cohesion of the composite electrode, reduce its interfacial resistivity, and improve the electronic conductivity and ion transport performance of the composite electrode, thereby enabling it to better exert its electrochemical capacity. Furthermore, compared to copper foil, the mesh openings on the current collector mesh can also allow the electrolyte and lithium ions to flow freely inside the composite electrode, thereby effectively improving the lithium ion transport efficiency, increasing the electrolyte penetration path, reducing the tortuosity of the composite electrode, and thus effectively improving the cycle stability and rate performance of the lithium-ion battery.

[0132] Comparing Example 1 and Comparative Example 3, and referring to the data in Table 2, it can be seen that, compared with the traditional wet coating preparation process, the preparation method of the composite electrode provided in this application can effectively improve the cohesion, electronic conductivity and lithium-ion transport performance of the composite electrode, while reducing the tortuosity of the composite electrode, thereby effectively improving the cycle stability and rate performance of the lithium-ion battery.

[0133] Comparing Examples 1, 4 to 6, and in conjunction with the data in Tables 1 and 2, it can be seen that, compared to other ranges, limiting the weight ratio of the hot-melt binder to polytetrafluoroethylene (PTFE) within the preferred range described above in this application is beneficial to improving the interaction between the hot-melt binder and PTFE, enabling PTFE to better exert its fibrous properties, while also improving the bonding strength between the electrode active material and the conductive agent, constructing a more continuous conductive network, improving the structural stability of the composite electrode, and reducing its tortuosity, thereby improving the cycle stability and rate performance of the lithium-ion battery.

[0134] 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 terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0135] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite electrode, characterized in that, The composite electrode includes a current collector and electrode plates disposed on both sides of the current collector; the current collector has through-holes; the electrode plates on both sides of the current collector are in contact at the holes; the electrode plates include an electrode active material, a conductive agent, and a binder; the binder includes a hot-melt binder.

2. The composite electrode according to claim 1, characterized in that, The thickness of the current collection mesh is 20–100 μm, and the mesh size is 8–120 mesh. Preferably, the mesh openings are arranged in an array; more preferably, the cross-section of the mesh openings is square, rectangular, or rhomboid. Preferably, the cross-sectional area of ​​a single mesh opening is 0.03–6 mm². 2 The distance between two adjacent mesh openings is 0.02–0.1 mm; Preferably, the material of the current collection network is selected from one or more of the group consisting of copper-nickel alloy, copper, nickel, aluminum and steel.

3. The composite electrode according to claim 1 or 2, characterized in that, The cross-section of the electrode sheet is square or rectangular; Preferably, the thickness of the electrode sheet is 60–1000 μm; Preferably, in the electrode sheet, the weight ratio of the electrode active material, the conductive agent, and the binder is (95-98):(0.4-2):(0.8-3). Preferably, the adhesive further includes polytetrafluoroethylene; more preferably, the weight ratio of the hot-melt adhesive to the polytetrafluoroethylene is (30-50):(50-70).

4. The composite electrode according to any one of claims 1 to 3, characterized in that, The melting temperature of the hot-melt adhesive is ≥80℃; Preferably, the softening temperature of the hot-melt adhesive is lower than its melting temperature, and the absolute value of the difference between the two is ≥20℃; Preferably, the hot-melt adhesive has a melting temperature of 80–180°C and a softening temperature of 60–150°C. Preferably, the hot-melt adhesive is relative to Li / Li + The voltage window of the electrical pair is 0–5V; Preferably, the hot-melt adhesive is selected from one or more of the group consisting of polyethylene, polyamide, polyurethane, butyl rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer, and polyethylene oxide; More preferably, the hot-melt adhesive is polyethylene with a weight-average molecular weight of 50,000 to 300,000; or, the hot-melt adhesive is ethylene-vinyl acetate copolymer with a weight-average molecular weight of 70,000 to 120,000; or, the hot-melt adhesive is polyamide with a weight-average molecular weight of 6,000 to 120,000.

5. The composite electrode according to claim 4, characterized in that, The electrode active material is a positive electrode active material or a negative electrode active material; Preferably, the positive electrode active material is selected from one or more of the group consisting of lithium iron phosphate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium cobalt oxide; Preferably, the negative electrode active material is selected from one or more of the group consisting of graphite, silicon oxide, and silicon carbon; Preferably, the conductive agent is selected from one or more of the group consisting of conductive carbon black, carbon nanotubes, graphene, conductive carbon nanofibers, conductive graphite, and porous carbon.

6. A method for preparing a composite electrode according to any one of claims 1 to 5, characterized in that, The method for preparing the composite electrode includes: Step S1: Prepare an electrode sheet containing an electrode active material, a conductive agent, and a binder; wherein the binder includes a hot-melt binder; Step S2: The electrode plates and the current collector are alternately stacked to obtain a stacked structure, and the electrode plates are on both sides of the stacked structure; wherein the current collector has through-holes. Step S3: Perform hot pressing on the stacked structure to obtain the composite electrode.

7. The method for preparing the composite electrode according to claim 6, characterized in that, Step S1 includes: Step S-A1: The electrode active material, the conductive agent, and the binder are mixed for the first time to obtain a first mixture; wherein the binder includes the hot-melt binder and polytetrafluoroethylene; Step S-A2: The first mixture is subjected to fibrous treatment to obtain fibrous powder; Step S-A3: The fibrous powder is pressed and molded to obtain the electrode sheet; Preferably, the linear velocity of the fiberization treatment is 20-120 m / s, and the time is 10 s-30 min.

8. The method for preparing the composite electrode according to claim 7, characterized in that, The weight ratio of the electrode active material, the conductive agent, and the binder is (95-98):(0.4-2):(0.8-3). Preferably, in the adhesive, the weight ratio of the hot-melt adhesive to the polytetrafluoroethylene is (30-50):(50-70).

9. The method for preparing the composite electrode according to any one of claims 6 to 8, characterized in that, In step S3, the pressure applied to the laminated structure during the hot pressing process is 1-15 MPa; the temperature of the hot pressing process is 80-200°C, and the time is 20-300 s; preferably, the temperature of the hot pressing process is 80-150°C, and the time is 20-90 s. Preferably, the hot pressing process is performed using a flatbed hot press or a roller press. More preferably, the hot pressing process is performed using the flat plate hot pressing equipment, and the pressure applied to the laminated structure is 1 to 15 MPa; More preferably, the hot pressing treatment is performed using the roller pressing equipment, and the roller diameter of the roller in the roller pressing equipment is 400-1000 mm; the linear speed of the roller is ≤80 m / min, preferably 2.5-40 m / min; and the pressure applied by the roller to the laminated structure is 2-15 MPa.

10. A lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, characterized in that, The positive electrode and / or the negative electrode are the composite electrode according to any one of claims 1 to 5.

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