A metal-free current collector integrated self-supporting electrode and a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries without metal current collectors, and specifically discloses a metal current collector-free integrated self-supporting electrode as well as a preparation method and application thereof. The electrode comprises, from top to bottom, a positive active material layer, a first conductive functional coating, a porous diaphragm substrate, a second conductive functional coating and a negative active material layer. The first and second conductive functional coatings are both composite functional coatings containing a conductive agent and a binder, and are used to replace metal current collectors to realize electronic conduction. The preparation method comprises the following steps: forming conductive functional coatings on both sides of the porous diaphragm substrate synchronously through a spraying process, and then coating the positive and negative active material layers respectively to form an integrated self-supporting structure. The application eliminates the use of copper foil and aluminum foil, reduces the weight and cost of the battery, solves the problem of large electronic transmission impedance of the electrode without current collectors, simplifies the preparation process and assembly process, improves the structural stability and energy density of the battery, and can be widely applied to the field of lithium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology with metal-free current collectors, and particularly relates to an integrated self-supporting electrode with metal-free current collectors, its preparation method and application. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and no memory effect, have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage. With the rapid development of related industries, the market is placing higher demands on improving the energy density and reducing the manufacturing cost of lithium-ion batteries.

[0003] Traditional lithium-ion battery electrode structures typically employ a coating process where positive and negative electrode active material slurries are coated onto the surfaces of aluminum and copper foil current collectors, respectively. After drying and rolling, the positive and negative electrode sheets are formed, which are then stacked with a separator or wound to assemble the battery cell. In this structure, the metal current collectors (aluminum and copper foils) primarily function to carry the active material and collect current. However, metal current collectors have significant drawbacks: firstly, their density is relatively high (aluminum foil 2.7 g / cm³). 3 Copper foil 8.9g / cm 3 Firstly, the cost of metal current collectors accounts for a considerable proportion of the total battery mass and has no lithium storage capacity, which limits the further improvement of battery mass energy density. Secondly, the cost of metal current collectors accounts for about 10% to 15% of the total battery material cost, becoming an important constraint on reducing battery manufacturing costs.

[0004] Furthermore, in traditional electrode structures, the active material layer and the metal current collector are physically bonded together through a binder. During long-term battery cycling, the active material undergoes volume expansion and contraction due to lithium insertion / extraction, which can easily lead to interface contact degradation and increased interface impedance, thereby affecting the battery's rate performance and cycle stability. At the battery assembly process level, the three independent structures of the positive electrode, separator, and negative electrode need to be precisely aligned, which is a complicated process and carries the risk of short circuits.

[0005] To address the aforementioned issues, researchers have attempted to develop current collector-free electrode structures. Chinese patent CN110957456A discloses a metal-free current collector composite electrode and its preparation method. This method involves first coating a polyolefin separator with a coating containing inorganic particles (such as AlPO4 and LiGe2(PO4)3) and a binder, followed by coating with positive and negative electrode active material layers. However, analysis of the technical solution reveals that the inorganic particles in the coating (AlPO4 is an electronic insulator, and LiGe2(PO4)3 is an ionic conductor but lacks electronic conductivity) themselves do not possess electronic conductivity, and no conductive components are added to the coating. When the metal current collector is removed, electrons generated by the electrode reaction must pass through this non-conductive coating to be transmitted to the external circuit, inevitably leading to a significant increase in the overall charging and discharging impedance of the battery. Therefore, while this solution achieves a current collector-free structure, its coating design fails to solve the core problem of difficult electron transport. Furthermore, this solution uses an extrusion coating method on the soft separator surface, which easily causes problems such as separator wrinkling and uneven coating, affecting production yield and consistency.

[0006] Another research direction is the development of self-supporting flexible electrodes. Chinese patent CN118919725B discloses a method for preparing a current collector-free flexible self-supporting electrode using a high free volume binder (PTMSP). This method involves mixing active material, conductive carbon, and PTMSP binder, coating the mixture onto a temporary current collector (such as aluminum foil), and then physically peeling off the self-supporting film after drying. Analysis of the preparation process reveals that this scheme introduces an additional "coating-peeling" step. The peeling process is prone to mechanical damage to the self-supporting film, and the consistency of peeling is difficult to guarantee, which is detrimental to yield control in large-scale production. More importantly, the product obtained by this scheme is only a single-polarity self-supporting film (such as a positive or negative electrode film). When assembling the battery, the positive electrode film, separator, and negative electrode film still need to be stacked independently and precisely aligned, failing to achieve integrated electrode-separator structure. Therefore, it still suffers from the inherent defects of traditional three-layer structures, such as cumbersome assembly, poor interlayer interface stability, and high risk of relative slippage.

[0007] Based on this, developing a metal-free integrated current collector electrode structure that can effectively reduce battery weight, simplify the manufacturing process, improve energy density, and has good electron transport performance and structural stability is of great practical significance for promoting the development of lithium-ion battery technology. Summary of the Invention

[0008] To address the problems of existing technologies where metal current collectors result in heavy batteries, low energy density, and high cost, and the high electron transport impedance and membrane deformation caused by non-conductive inorganic coatings in existing metal-free current collector electrodes (such as CN110957456A) due to the use of non-conductive inorganic coatings, and the complexity and poor product consistency caused by the "coating-peeling" process in CN118919725B, which is still a single-polarity self-supporting film and fails to achieve electrode-separator integration, resulting in poor interface stability and cumbersome assembly processes, this invention provides a metal-free integrated self-supporting current collector electrode, its preparation method, and its application. This invention achieves efficient replacement of metal current collectors through integrated structural design and process optimization, improving the overall electrochemical performance of the battery while reducing battery manufacturing costs.

[0009] To achieve the above objectives, the present invention adopts the following technical solution.

[0010] In a first aspect, the present invention provides a metal-free integrated self-supporting electrode for current collection, wherein the metal-free integrated self-supporting electrode for current collection comprises, from top to bottom: a positive electrode active material layer, a first conductive functional coating, a porous membrane substrate, a second conductive functional coating, and a negative electrode active material layer. Both the first conductive functional coating and the second conductive functional coating are composite functional coatings containing conductive agents and binders, used to replace metal current collectors to achieve electron conduction.

[0011] Preferably, the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene, and conductive graphite, with a particle size of 10~100nm.

[0012] In this invention, the aforementioned conductive agent is used to construct a continuous three-dimensional electron conduction network in the coating, thereby replacing the traditional metal current collector to achieve efficient electron transmission between the active material layer and the external circuit.

[0013] Preferably, the adhesive is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, lithium carboxymethyl cellulose, and sodium carboxymethyl cellulose.

[0014] In this invention, the binder is used to firmly bond the conductive agent to the porous membrane substrate, while simultaneously improving the mechanical strength of the porous membrane substrate and enhancing the structural stability of the electrode. The positive electrode active material layer and the negative electrode active material layer are respectively directly coated on the surface of the conductive functional coating on the corresponding side, forming an integrated self-supporting structure with a metal-free current collector.

[0015] Preferably, the porous membrane substrate is a polyolefin microporous membrane, a non-woven fabric membrane, or a ceramic composite membrane, with a thickness of 9~25μm, a porosity of 40%~60%, and an air permeability of 100~500s / 100mL.

[0016] Secondly, the present invention provides a method for preparing a metal-free, integrated, self-supporting current collector electrode, comprising the following steps: S1. Preparation of functional coating slurry: Disperse the conductive agent and binder in the first solvent, stir and mix evenly to obtain the functional coating slurry; S2. Forming of double-sided functional coating of diaphragm: The functional coating slurry is simultaneously coated on both sides of the porous diaphragm substrate using a spraying process. After drying, a first conductive functional coating and a second conductive functional coating are formed on the two surfaces of the porous diaphragm substrate, respectively, to obtain a double-sided coated functional diaphragm. S3. Positive electrode active material layer coating: The positive electrode active material, conductive agent and binder are dispersed in a second solvent and stirred and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of the first conductive functional coating of the functionalized membrane, and after drying, a positive electrode active material layer is formed; S4. Coating of negative electrode active material layer: Disperse the negative electrode active material, conductive agent and binder in a third solvent, stir and mix evenly to obtain a negative electrode slurry; coat the negative electrode slurry onto the surface of the second conductive functional coating of the functionalized membrane, and after drying, form a negative electrode active material layer, thus obtaining a metal-free current collector integrated self-supporting electrode.

[0017] Preferably, in step S1, the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, graphene, and conductive graphite, with a particle size of 10~100nm; the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, lithium carboxymethyl cellulose, and sodium carboxymethyl cellulose; and the first solvent is N-methylpyrrolidone or deionized water.

[0018] Preferably, in step S2, the spraying pressure of the spraying process is 0.2~0.6MPa, the spraying distance is 10~30cm, and the spraying speed is 2~10m / min.

[0019] Preferably, in step S1, the mass ratio of the conductive agent to the binder is (2:8) to (8:2), and the total mass of the conductive agent and the binder accounts for 40% to 70% of the total mass of the functional coating slurry.

[0020] Preferably, in step S2, the single-sided coating thickness of the first conductive functional coating and the second conductive functional coating is independently 2~20μm.

[0021] Preferably, in step S2, the porous membrane substrate is a polyolefin microporous membrane, a non-woven fabric membrane, or a ceramic composite membrane, with a thickness of 9~25μm, a porosity of 40%~60%, and an air permeability of 100~500s / 100mL.

[0022] Preferably, in step S2, the drying temperature is 40-80°C.

[0023] Preferably, in step S3, the positive electrode active material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide, and its particle size is 0.5~50μm; in step S4, the negative electrode active material is selected from one or more of artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate, and its particle size is 2~20μm.

[0024] Preferably, in step S3, the mass ratio of the positive electrode active material, conductive agent and binder is (85~96):(2~8):(2~7), and the total mass of the positive electrode active material, conductive agent and binder accounts for 45%~80% of the total mass of the positive electrode slurry.

[0025] Preferably, in step S3, the thickness of the positive electrode active material layer is 50~200μm, and the drying temperature is 80-120℃.

[0026] Preferably, in step S4, the mass ratio of the negative electrode active material, conductive agent and binder is (80~96):(2~10):(2~10), and the total mass of the negative electrode active material, conductive agent and binder accounts for 40%~75% of the total mass of the negative electrode slurry.

[0027] Preferably, in step S4, the thickness of the negative electrode active material layer is 50~200μm, and the drying temperature is 80-120℃.

[0028] Preferably, in steps S3 and S4, the drying method is independently hot air drying, infrared drying, or vacuum drying; the second solvent and the third solvent are independently N-methylpyrrolidone or deionized water.

[0029] Thirdly, the present invention provides a lithium-ion battery comprising the metal-free current collector integrated self-supporting electrode described in the first aspect above, or the metal-free current collector integrated self-supporting electrode prepared by the preparation method described in the second aspect above.

[0030] Preferably, the lithium-ion battery is a coin cell. The metal-free current collector integrated self-supporting electrode is placed inside the positive electrode shell of the coin cell, with the negative electrode active material layer facing upwards and the positive electrode active material layer facing downwards, directly contacting the inner wall of the positive electrode shell. Electrolyte is injected into the positive electrode shell. A gasket and a spring are placed sequentially on the surface of the negative electrode active material layer, and the negative electrode shell is covered and sealed, thus obtaining a coin cell lithium-ion battery using a metal-free current collector integrated self-supporting electrode. The electrolyte is a lithium-ion battery electrolyte with ethylene carbonate / dimethyl carbonate as a mixed solvent (volume ratio 7:3) and LiPF6 as the solute, with a solute concentration of 0.8~1.2 mol / L and an electrolyte injection volume of 50~100 μL.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention directly replaces the traditional metal current collector by conductive functional coating, completely eliminating the use of copper foil and aluminum foil, which can reduce the cost of battery raw materials by 10% to 15%; at the same time, the integrated structure simplifies the battery assembly process, further reducing the manufacturing cost by 5% to 8%, and significantly improving the economic benefits of battery production.

[0032] (2) The present invention uses a non-contact spraying process to prepare a conductive functional coating on the surface of a porous diaphragm, which avoids the wrinkles and deformation problems caused by the soft texture of the diaphragm during the coating process, improves the uniformity of the coating and its adhesion to the diaphragm, and is conducive to improving the consistency of the electrodes and the product yield.

[0033] (3) The present invention loads the positive and negative active material layers onto the conductive functional coatings on both sides of the separator to form an integrated self-supporting structure. The positive and negative active material layers can directly contact the battery casing to achieve conductivity, which greatly simplifies the battery assembly process.

[0034] (4) The conductive functional coating in this invention has multiple functions: on the one hand, the conductive agent in the coating constructs a continuous three-dimensional electron conduction network, providing an efficient electron transport path for the electrochemical reaction of the electrode, and solving the core problem of large electron transport impedance after removing the metal current collector; on the other hand, the binder in the coating firmly bonds the conductive agent to the porous membrane substrate through the spraying process, which enhances the mechanical strength of the membrane and avoids the relative slippage and interface separation problem between the membrane and the electrode in the traditional structure, effectively improving the safety and structural stability of the battery.

[0035] (5) Compared with the prior art CN110957456A, which uses non-conductive inorganic coatings (AlPO4, LiGe2(PO4)3) resulting in high electron transport impedance, this invention uses a composite functional coating containing conductive agents to construct an efficient electron conduction network, ensuring rate performance without current collector structure. Compared with the prior art CN118919725B, which uses a "coating-peeling" process resulting in complex process, poor product consistency, and still requires independent assembly of the three-layer structure of positive electrode film, separator, and negative electrode film, this invention uses a spraying process to directly form conductive coating and active material layer on both sides of the separator simultaneously, realizing a true "integrated self-supporting" structure, simplifying the process and improving structural stability. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a metal-free, integrated, self-supporting current collector electrode according to the present invention; Figure 2 This is a graph showing the first charge and discharge process of the battery obtained in Example 1 of the present invention. Figure 3 This is a graph showing the first charge and discharge process of the battery obtained in Comparative Example 1 of the present invention. Figure 4 This is a graph showing the first charge and discharge process of the battery obtained in Comparative Example 3 of this invention.

[0037] Explanation of reference numerals in the attached figures: 1. Positive electrode active material layer; 2. First conductive functional coating; 3. Porous membrane substrate; 4. Second conductive functional coating; 5. Negative electrode active material layer. Detailed Implementation

[0038] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to specific embodiments. Obviously, the described embodiments are only a portion, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] To address the problems of existing technologies where metal current collectors result in heavy batteries, low energy density, and high cost, and the high electron transport impedance and membrane deformation caused by non-conductive inorganic coatings in existing metal-free current collector electrodes (such as CN110957456A) due to the use of non-conductive inorganic coatings, and the complexity and poor product consistency caused by the "coating-peeling" process in CN118919725B, which is still a single-polarity self-supporting film and fails to achieve electrode-separator integration, resulting in poor interface stability and cumbersome assembly processes, this invention provides a metal-free integrated self-supporting current collector electrode, its preparation method, and its application. This invention achieves efficient replacement of metal current collectors through integrated structural design and process optimization, improving the overall electrochemical performance of the battery while reducing battery manufacturing costs.

[0043] The following examples and comparative models further illustrate this point.

[0044] Example 1 This embodiment provides a metal-free, integrated, self-supporting current collector electrode, such as... Figure 1 As shown, its structure, from top to bottom, consists of a positive electrode active material layer 1, a first conductive functional coating 2, a porous membrane substrate 3, a second conductive functional coating 4, and a negative electrode active material layer 5.

[0045] This embodiment also provides a method for fabricating the above-mentioned metal-free current collector integrated self-supporting electrode, including the following steps: (1) Preparation of functional coating slurry: Conductive carbon black (particle size 50nm) and carbon nanotubes (diameter 10~20nm, length 5~15μm) are mixed at a mass ratio of 5:5 to obtain a conductive agent mixture. The conductive agent mixture is then mixed with polyvinylidene fluoride at a mass ratio of 5:5 and added to N-methylpyrrolidone so that the total mass of the conductive agent and binder accounts for 48.5% of the total mass of the slurry. The mixture is stirred evenly in a vacuum mixer to obtain a functional coating slurry with a solid content of 48.5%.

[0046] (2) Preparation of functionalized diaphragm: A polyethylene microporous membrane with a thickness of 20 μm, a porosity of 45%, and an air permeability of 200 s / 100 mL was selected as the porous diaphragm substrate; the functional coating slurry prepared in step (1) was simultaneously coated on both sides of the diaphragm using a spraying process. The spraying process parameters were: spraying pressure 0.4 MPa, spraying distance 20 cm, and spraying speed 5 m / min; after coating, the membrane was vacuum dried at 80 °C for 60 min to form a first conductive functional coating and a second conductive functional coating with a thickness of 8 μm on the two surfaces of the diaphragm, respectively, to obtain a double-sided coated functionalized diaphragm.

[0047] (3) Preparation and coating of positive electrode slurry: Lithium cobalt oxide (specific capacity 145mAh / g, particle size 12μm), conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 95:2.5:2.5 and added to N-methylpyrrolidone. The solid content is controlled to be 70%. The positive electrode slurry is prepared by stirring and mixing evenly. The positive electrode slurry is coated on the surface of the first conductive functional coating of the functionalized membrane obtained in step (2). The coating thickness is 120μm. The membrane is dried by hot air at 100℃ for 30min to form a positive electrode active material layer.

[0048] (4) Preparation and coating of negative electrode slurry: Artificial graphite (specific capacity 350mAh / g, particle size 15μm), conductive carbon black, styrene-butadiene rubber (SBR) / carboxymethyl cellulose (CMC) composite binder (SBR:CMC mass ratio 1:1) are mixed at a mass ratio of 85:7.5:7.5, added to deionized water, and the solid content is controlled at 50%. The negative electrode slurry is prepared by stirring and mixing evenly. The negative electrode slurry is coated on the surface of the second conductive functional coating of the functionalized membrane obtained in step (2) with a coating thickness of 180μm. After vacuum drying at 80℃ for 60min, a negative electrode active material layer is formed, thus obtaining a metal-free current collector integrated self-supporting electrode.

[0049] This embodiment also provides a coin cell lithium-ion battery comprising the aforementioned metal-free integrated self-supporting electrode with a current collector. The battery consists of the metal-free integrated self-supporting electrode with a current collector, a gasket, a spring, a battery casing, and an electrolyte. Its preparation method is as follows: the metal-free integrated self-supporting electrode with a current collector is cut into circular electrode sheets of a predetermined diameter of 12 mm, and placed inside the positive electrode casing of the coin cell, with the negative electrode active material layer facing upwards and the positive electrode active material layer facing downwards, directly contacting the inner wall of the positive electrode casing; an electrolyte (a lithium-ion battery electrolyte with ethylene carbonate / dimethyl carbonate as a mixed solvent, a volume ratio of 7:3, and a LiPF6 concentration of 1.0 mol / L, injected in an amount of 80 μL) is injected into the positive electrode casing; a gasket and a spring are sequentially placed on the surface of the negative electrode active material layer, the negative electrode casing is closed, and the battery is encapsulated to obtain the coin cell lithium-ion battery. The remaining processes are consistent with the conventional coin cell lithium-ion battery preparation process.

[0050] Example 2 The only difference between this embodiment and Example 1 is that in step (3), the positive electrode active material lithium cobalt oxide is replaced with lithium manganese iron phosphate (specific capacity 140mAh / g, particle size 3μm). Other parameters and preparation process are the same as in Example 1.

[0051] Example 3 The only difference between this embodiment and Example 1 is that in step (3), the positive electrode active material lithium cobalt oxide is replaced with nickel-cobalt-manganese ternary material NCM811 (specific capacity 160mAh / g, particle size 8μm). Other parameters and preparation process are the same as in Example 1.

[0052] Example 4 The only difference between this embodiment and Embodiment 1 is that in step (4), the negative electrode active material, artificial graphite, is replaced with silicon-carbon material (silicon content 5%, specific capacity 500mAh / g, particle size 5μm). Other parameters and preparation processes are the same as in Embodiment 1.

[0053] Example 5 The only difference between this embodiment and Example 1 is that in step (1), the mass ratio of the conductive agent mixture to polyvinylidene fluoride is adjusted to 3:7. Other parameters and preparation processes are the same as in Example 1.

[0054] Comparative Example 1 This comparative example provides a metal-free current collector electrode and its method for preparing a coin-type lithium-ion battery. The only difference from Example 1 is that a conductive functional coating is prepared only on the side of the porous membrane substrate near the positive electrode active material layer, and no conductive functional coating is prepared on the side near the negative electrode active material layer. Other parameters and preparation processes are the same as in Example 1.

[0055] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in step (1) when preparing the functional coating slurry, conductive carbon black and carbon nanotubes are not added; instead, polyvinylidene fluoride is dispersed in N-methylpyrrolidone to prepare a pure binder coating. Other parameters and preparation processes are the same as in Example 1.

[0056] Comparative Example 3 This comparative example provides a conventional coin cell and its fabrication method. The specific fabrication steps are as follows: (1) Preparation of positive electrode sheet: Lithium cobalt oxide, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 95:2.5:2.5 and added to N-methylpyrrolidone. The solid content is controlled at 70%. The mixture is stirred and mixed evenly to obtain positive electrode slurry. The positive electrode slurry is coated on the surface of a 15μm thick aluminum foil current collector with a coating thickness of 120μm. It is dried by hot air at 100℃ for 30min to form a positive electrode active material layer. After rolling, it is cut into a circular positive electrode sheet with a diameter of 12mm.

[0057] (2) Preparation of negative electrode sheet: Artificial graphite, conductive carbon black, and styrene-butadiene rubber / sodium carboxymethyl cellulose composite binder (SBR:CMC mass ratio 1:1) are mixed at a mass ratio of 85:7.5:7.5, added to deionized water, and the solid content is controlled at 50%. The mixture is stirred and mixed evenly to obtain a negative electrode slurry. The negative electrode slurry is coated on the surface of a 10μm thick copper foil current collector with a coating thickness of 180μm. After vacuum drying at 80℃ for 60min, a negative electrode active material layer is formed. After rolling, it is cut into a circular negative electrode sheet with a diameter of 12mm.

[0058] (3) Preparation of diaphragm: Select a polyethylene microporous membrane with a thickness of 20μm, porosity of 45% and air permeability of 200s / 100mL as the diaphragm, and cut it into a circular diaphragm sheet with a diameter of 12mm.

[0059] (4) Assembly of button cell: Place the negative electrode sheet cut in step (2) on the inner wall of the negative electrode shell, stack the separator in step (3) and the positive electrode sheet in step (1) in sequence, inject electrolyte (same as in Example 1), encapsulate with CR2025 button cell module, and after standing at room temperature for 12 hours, a button cell lithium-ion battery with conventional structure is obtained.

[0060] It should be noted that in this comparative example, the positive electrode, negative electrode, and separator all use the same diameter (12mm). Although conventional processes typically use a design where the negative electrode is slightly larger than the positive electrode and the separator is slightly larger than the electrode to prevent short circuits, this comparative example standardizes the dimensions of each component to achieve a single-variable comparison with Example 1. During assembly, precise positioning ensures alignment of the positive and negative electrodes, preventing short circuits due to identical dimensions.

[0061] Performance testing and results analysis: Electrochemical performance tests were conducted on the coin-type lithium-ion batteries prepared in Examples 1-5 and Comparative Examples 1-3. The test conditions were: room temperature (25±2℃), charge / discharge voltage range of 3.0V~4.5V (for Comparative Example 3 with lithium cobalt oxide as the positive electrode), and charge / discharge rate of 0.2C (1C = 145mAh / g, calculated based on the mass of the positive electrode active material). The test results are as follows. Figure 2-4 As shown in Table 1.

[0062] Figure 2 This is a typical charge-discharge process curve of the battery obtained in Example 1 of the present invention. Figure 2 It can be seen that the battery in Example 1 has a stable voltage platform and a discharge capacity of about 200mAh, showing good electrochemical performance.

[0063] Figure 3 This is a typical charge-discharge process curve of the battery obtained in Comparative Example 1. Combined with... Figure 2 and Figure 3It can be seen that the discharge capacity of the battery in Comparative Example 1 (with conductive functional coating prepared only on one side of the separator) is significantly reduced (approximately 185mAh), indicating that the double-sided conductive coating is a necessary condition for the stable operation of the integrated electrode, ensuring that both the positive and negative electrodes have efficient electron transport channels.

[0064] Figure 4 This is a typical charge-discharge process curve of the battery obtained in Comparative Example 3. Combined with... Figure 2 and Figure 4 It can be seen that the discharge capacity of Example 1 and Comparative Example 3 (traditional structure with current collector) is close (approximately 200mAh and 205mAh respectively). However, since Example 1 does not use copper foil or aluminum foil current collectors, the overall weight of the battery is significantly reduced and the energy density is improved.

[0065] Table 1:

[0066] In summary, this invention forms an integrated, self-supporting electrode without a metal current collector by simultaneously forming a conductive functional coating containing a conductive agent on both sides of a porous membrane using a spray coating process, and then coating the surface with positive and negative electrode active material layers respectively. This structure not only solves the problem of difficult electron transport after removing the metal current collector, but also achieves integrated electrode-membrane design, simplifying the fabrication process and battery assembly steps, while improving the structural stability and energy density of the battery.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal-free, integrated, self-supporting current collector electrode, characterized in that, The metal-free current collector integrated self-supporting electrode comprises, from top to bottom: a positive electrode active material layer, a first conductive functional coating, a porous membrane substrate, a second conductive functional coating, and a negative electrode active material layer. Both the first conductive functional coating and the second conductive functional coating are composite functional coatings containing conductive agents and binders, used to replace metal current collectors to achieve electron conduction.

2. The metal-free current collector integrated self-supporting electrode according to claim 1, characterized in that, The conductive agent in the first conductive functional coating / the second conductive functional coating is selected from one or more of conductive carbon black, carbon nanotubes, graphene, and conductive graphite, with a particle size of 10~100nm; the binder in the first conductive functional coating / the second conductive functional coating is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, lithium carboxymethyl cellulose, and sodium carboxymethyl cellulose.

3. The metal-free current collector integrated self-supporting electrode according to claim 1, characterized in that, The porous membrane substrate is a polyolefin microporous membrane, a non-woven fabric membrane, or a ceramic composite membrane, with a thickness of 9~25μm and a porosity of 40%~60%.

4. A method for preparing a metal-free current collector integrated self-supporting electrode as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of functional coating slurry: Disperse the conductive agent and binder in the first solvent, stir and mix evenly to obtain the functional coating slurry; S2. Forming of double-sided functional coating of diaphragm: The functional coating slurry is simultaneously coated on both sides of the porous diaphragm substrate using a spraying process. After drying, a first conductive functional coating and a second conductive functional coating are formed on the two surfaces of the porous diaphragm substrate, respectively, to obtain a double-sided coated functional diaphragm. S3. Positive electrode active material layer coating: The positive electrode active material, conductive agent and binder are dispersed in a second solvent and stirred and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is coated on the surface of the first conductive functional coating of the functionalized membrane, and after drying, a positive electrode active material layer is formed; S4. Coating of negative electrode active material layer: Disperse the negative electrode active material, conductive agent and binder in a third solvent, stir and mix evenly to obtain a negative electrode slurry; coat the negative electrode slurry onto the surface of the second conductive functional coating of the functionalized membrane, and after drying, form a negative electrode active material layer, thus obtaining a metal-free current collector integrated self-supporting electrode.

5. The preparation method according to claim 4, characterized in that, In step S2, the spraying pressure of the spraying process is 0.2~0.6MPa, the spraying distance is 10~30cm, and the spraying speed is 2~10m / min.

6. The preparation method according to claim 4, characterized in that, In step S1, the mass ratio of the conductive agent to the binder is (2:8) to (8:2), and the total mass of the conductive agent and the binder accounts for 40% to 70% of the total mass of the functional coating slurry.

7. The preparation method according to claim 4, characterized in that, In step S2, the thickness of the first conductive functional coating and the second conductive functional coating on one side is independently 2~20μm.

8. The preparation method according to claim 4, characterized in that, In step S3, the positive electrode active material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide, with a particle size of 0.5~50μm; in step S4, the negative electrode active material is selected from one or more of artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate, with a particle size of 2~20μm.

9. A lithium-ion battery, characterized in that, Includes the metal-free integrated self-supporting electrode with current collector as described in any one of claims 1-3, or the metal-free integrated self-supporting electrode with current collector prepared by the preparation method described in any one of claims 4-8.

10. The lithium-ion battery according to claim 9, characterized in that, The lithium-ion battery is a coin cell battery. The metal-free current collector integrated self-supporting electrode is placed inside the positive electrode shell of the coin cell battery. The negative electrode active material layer of the electrode faces upward and the positive electrode active material layer faces downward, and is in direct contact with the inner wall of the positive electrode shell.

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