A three-dimensional porous material based on melt spinning process and its preparation method

Abstract

This invention discloses a three-dimensional porous material based on melt spinning. The three-dimensional porous material is a multilayer fiber network composite composed of two or more Type I layers, two or more Type II layers, or two or more Type III layers. In the Type I and Type II layers, the fiber diameter exhibits a unimodal distribution, while in the Type III layer, the fiber diameter exhibits a bimodal distribution. This invention constructs fibers with unimodal or bimodal diameter distributions within a single layer. Through the stacking and bonding techniques of similar fiber network layers, the thickness uniformity is improved. The single-layer and stacking processes can be flexibly adjusted according to the battery's requirements for the support layer, manufacturing support layers that meet different needs. Different materials can be used in different layers to meet different functional requirements. The resulting three-dimensional porous structure enables electrolyte permeation and low-resistance ion transport, and the material exhibits high stability during battery chemistry. The process is simple, flexible, and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional porous material preparation technology, specifically to a three-dimensional porous material based on melt spinning process and its preparation method. Background Technology

[0002] Currently, improvements in energy density and safety of liquid lithium-ion batteries are gradually encountering bottlenecks, and solid-state batteries are considered an important path to overcome these limitations. However, the film-forming process of solid electrolytes for solid-state batteries still faces significant obstacles: due to the strict limitation of binder usage (usually only a very small amount), it is difficult to process electrolytes, whether in powder or slurry form, into thin films with complete structures and a certain degree of self-support, resulting in generally low production efficiency and product consistency. Introducing materials with high porosity and three-dimensional porous structures as support layers is considered a key approach to solving these problems. In practical applications, such support layers must simultaneously meet the following conditions: uniform thickness (thickness deviation should generally be controlled within ±3μm, and in special scenarios, even less than ±1.5μm is required), porosity greater than 60%, average pore size greater than 2μm, and acceptable mechanical properties.

[0003] Currently reported solid electrolyte support materials and their preparation methods mainly include the following: Firstly, there is the perforation process for non-porous substrate membranes. Perforated membranes prepared using this process cannot construct a three-dimensional continuous ion transport network; instead, they significantly increase ion migration resistance. According to literature reports, after using this type of support, the ionic conductivity often drops to one-fifth to one-tenth of its original value.

[0004] Secondly, the short fiber dispersion and web-making method (see CN114759253A). This technical route consumes a large amount of water and is cumbersome: first, chemical fibers must be obtained through melt spinning and then cut into short fibers, or natural fibers must be directly pulped, and then dispersed in water to form a web. In addition, dispersing agents must be added, which poses an environmental burden.

[0005] Third, the wet phase transformation process combined with mechanical stretching. The pore size obtained by this method is usually no more than 0.2 μm, making it difficult for electrolyte powder to fill effectively and resulting in high ion transport resistance.

[0006] Fourth, electrospinning technology (see CN120461967A). The disadvantage of this method is that it requires a high proportion of organic solvents, which will cause environmental problems, and its large-scale production capacity is relatively weak. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a three-dimensional porous material based on melt spinning. Within the same layer, the fiber diameter exhibits a single-peak distribution (i.e., only one main diameter range) within the range of 0.5-5.0 μm or 5-20 μm, or a bi-peak distribution (i.e., two distinct diameter concentration areas) within the range of 1-20 μm. Multiple layers of similar fiber webs are stacked, and the material thickness fluctuation is controlled within ±3 μm through stacking and bonding, while maintaining an average pore size ≥2 μm.

[0008] To address the aforementioned technical problems, the first aspect of this invention provides a three-dimensional porous material used as a solid electrolyte film-forming support layer. Its structure is a multilayer fiber network composite, wherein the composite consists of two or more fiber layers of the same type. The type is Type I (suitable for small-particle-size and high-flow-rate electrolyte slurries), Type II (suitable for large-particle-size and low-flow-rate electrolyte slurries), or Type III (suitable for support layers with large particle size distributions and high requirements for mechanical properties, pore size, and thickness uniformity). The diameter distribution of each type of fiber layer satisfies the following conditions: The fiber diameter in the type I fiber layer has a unimodal distribution, and satisfies the following conditions: 0.5μm≤80% of the fibers have a diameter ≤5.0μm, and 1μm≤60% of the fibers have a diameter ≤3.5μm. The fiber diameter in the type II fiber layer is unimodal, and satisfies the following conditions: 5μm≤80% of the fibers have a diameter ≤20μm, and 7μm≤60% of the fibers have a diameter ≤15μm. The fiber diameter in the type III fiber layer exhibits a bimodal distribution, and satisfies the following conditions: 1μm≤80% of the fibers have a diameter ≤20μm, 1μm≤30% of the fibers have a diameter ≤3.5μm, and 4.5μm≤20% of the fibers have a diameter ≤10μm.

[0009] The core of this invention lies in the customized design of the fiber diameter distribution pattern within each single layer constituting the multilayer fiber web composite. Specifically, each fiber layer can select one of the following two distribution patterns: Unimodal distribution pattern: The fiber diameter in this layer is concentrated in the range of 0.5μm-5μm, or concentrated in the range of 5μm-20μm; Bimodal distribution pattern: There are two diameter distribution peaks in this layer, which fall within the ranges of 1μm-3.5μm and 4.5μm-10μm, respectively.

[0010] Multiple layers of the same type of fiber (i.e., layers with the same distribution pattern and diameter distribution range) are stacked and bonded together using an adhesive process to obtain a three-dimensional porous material for supporting solid electrolyte film formation. The resulting material exhibits electrochemical inertness and low ion transport resistance: it remains chemically stable under battery operating conditions, and the three-dimensional through-hole structure provides low-impedance channels for ion migration after being filled by the electrolyte; it also possesses excellent and highly consistent mechanical properties: the product has sufficient structural strength to facilitate subsequent processing, the material thickness deviation is controlled within ±3μm, and the average pore size is not less than 2μm, enabling it to adapt to the differentiated requirements of different types of electrolyte membranes for the support layer.

[0011] Furthermore, the raw materials for the three-dimensional porous material can be selected from one or more combinations of olefin-based polymers and block copolymers, polyamide (PA), and polyester (PET), all of which exhibit good stability during electrochemical processes. Different polymer materials can be used between different layers to achieve functional design. For example, when thermal or pressure-responsive bonding is required, polymer layers with thermosensitive or pressure-sensitive bonding properties can be used. The structure of a single fiber can be a homogeneous fiber of a single component, or a composite fiber structure formed by two materials in a skin-core or parallel manner.

[0012] Furthermore, the olefin-based polymer and block copolymer are selected from one or more of polypropylene (PP), polyethylene (PE), amorphous α-olefin copolymer (APAO), ethylene-butene copolymer and ethylene-octene copolymer (POE), styrene-butadiene-styrene block copolymer (SBS), polyisobutylene (PIB), ethylene-vinyl acetate copolymer (EVA), and random polypropylene (APP).

[0013] Furthermore, the average pore size of the three-dimensional porous material is ≥2μm.

[0014] Furthermore, another aspect of the present invention provides a method for preparing the above-mentioned three-dimensional porous material. Specifically, the method involves first spraying spun fibers and laying them into a web through a melt spinning process, and then sequentially forming the three-dimensional porous material through a layering and bonding process. In this preparation method, the thickness fluctuation of the material is reduced and the thickness uniformity is improved by multi-layer layering and bonding.

[0015] Furthermore, in the melt spinning process, a metal mesh connected to a DC power supply is provided on the path between the spinneret outlet and the receiving mesh belt, and the metal mesh is 2-5 cm away from the end face of the spinneret outlet; the spun fibers ejected from the spinneret pass through the inside of the metal mesh and fall onto the receiving mesh belt.

[0016] Furthermore, the voltage value of the DC power supply is set to ≥0.5kV and ≤4kV. Within this voltage range, it does not play a role in refining. The static voltage plays a role in electrostatic repulsion and confinement of the fiber jet, reducing the degree of disorder in fiber deposition caused by airflow turbulence, thereby improving the uniformity of thickness. The thickness fluctuation can be further controlled within ±1.5μm by setting a metal mesh enclosure.

[0017] Furthermore, the bonding process can be implemented by means of residual heat bonding (direct bonding using residual heat during fiber forming and web laying), hot pressing bonding (hot pressing bonding using the hot pressing adhesion of fibers) or hot air bonding (bonding using hot air).

[0018] Furthermore, by simultaneously configuring spinnerets with a first aperture and a second aperture on the die head during the melt spinning process, and with the first aperture not equal to the second aperture, the resulting type III fiber layer exhibits a bimodal distribution.

[0019] Furthermore, the metal mesh enclosure is either in use or not in use. In the in use state, the thickness fluctuation of the obtained three-dimensional porous material does not exceed 1.5 μm; in the not-used state, the thickness fluctuation of the obtained three-dimensional porous material does not exceed 3 μm.

[0020] The beneficial effects of this invention are: The three-dimensional porous support material obtained by this invention has the following advantages: 1) It is easy to fill the electrolyte and achieve ion transport resistance: Its internal three-dimensional through-hole structure can enable the electrolyte to be filled and provide a low-resistance channel for ion transport; 2) It has high electrochemical stability: The polymer raw materials used in the three-dimensional porous material of this invention (the same or different materials can be selected in different layers as needed, such as olefins, polyamides, polyesters, etc.) exhibit good stability in the battery electrochemical environment and are not prone to side reactions; 3) It has strong functional designability: Different materials can be used in different layers of the three-dimensional porous material of this invention. For example, by introducing polymers with pressure-sensitive or heat-sensitive bonding properties into different layers, the material itself can have specific bonding functions to meet the interface requirements of different battery systems for the support layer; The preparation method of the present invention can effectively improve the thickness uniformity of the final product by designing fibers with single-peak or double-peak diameter distribution in a single fiber layer and implementing multi-layer stacking and bonding of similar fiber webs. At the same time, the single-layer parameters, stacking structure and bonding process can be freely adjusted according to the specific requirements of the battery for the support layer. The process is flexible and controllable and suitable for mass production. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the melt spinning process in Embodiment 5 of the present invention; The labels in the diagram are as follows: 1. Spinning box, 2. Metal mesh enclosure, 3. DC power supply, 4. Spinning fiber, 5. Receiving mesh belt.

[0023] Figure 2 This is a SEM image of the three-dimensional porous material of Embodiment 1 of the present invention.

[0024] Figure 3 This is a fiber diameter distribution diagram of Embodiment 1 of the present invention.

[0025] Figure 4 This is a fiber diameter distribution diagram of Embodiment 9 of the present invention.

[0026] Figure 5 This is a fiber diameter distribution diagram of Embodiment 11 of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In this invention, unless otherwise stated, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are merely for the convenience of describing the invention and 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, and therefore should not be construed as limiting the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" 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 communication of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0029] The test methods used in the following examples and comparative examples are as follows: 1. Fiber diameter: Tested according to standard GB / T20332-2006 "Textiles - Test Method for Fiber Diameter - Projection Microscopy Method", with a count of no less than 200 fibers.

[0030] 2. Porosity: Tested according to the mass density method (Method A) in standard GB / T42697-2023 "Test Method for Porosity of Nonwoven Fabrics". The formula for calculating porosity is: P=(1-ρ0 / ρ)×100%, where: P is porosity (%), ρ0 is the apparent density of the nonwoven fabric (g / cm³). 3 ρ is the true density of the fiber material (g / cm³). 3 ).

[0031] 3. Tensile strength: Tested according to standard ISO9073-3, wherein the specimen width is 50 mm, the gauge length is 100 mm, and the tensile speed is 100 mm / min.

[0032] Example 1: Three-dimensional porous material composed of type I fiber layers Raw materials and process: Polypropylene (PP) is selected as the fiber-forming raw material. The spinneret diameter of the die head equipped with the melt spinning equipment is 0.28mm. The spinning process conditions are as follows: the box temperature is set to 250℃, the hot air temperature is 250℃, the hot air fan frequency is 1000Hz, and the cold air fan frequency is 900Hz. The spun fiber 4 is laid on the receiving mesh belt 5 to form a single layer of fiber with a basis weight of 4g / m². Two rolls of this fiber layer are stacked and fed into a hot roll mill for bonding. The roll pressure is 2.5MPa and the roll surface temperature is 120℃.

[0033] Finished Product Performance: The resulting product is a double-layer fiber web composite with an average thickness of 30.56 μm and a thickness fluctuation range of ±2.86 μm. The diameter distribution of the single-layer fibers meets the following requirements: over 80% of the fiber diameter falls within the range of 0.5–5.0 μm, exhibiting a unimodal distribution characteristic; among them, fibers with a diameter between 1 and 3.5 μm account for over 60% (see details for specific distribution). Figure 3 The material has a porosity of 71.54% and an average pore size of 3.16 μm (microstructure can be found in...). Figure 2 The tensile strength reaches 11.50 N / 5 cm.

[0034] Example 2: Three-dimensional porous material composed of type I fiber layers Same as Example 1, except that: the single-layer mesh weight is changed to 2.67 g / m²; and the number of rolls is changed to 3 (i.e., a three-layer structure). The finished product has an average thickness of 30.82 μm and a thickness fluctuation of ±2.65 μm; a porosity of 71.78%, an average pore size of 3.55 μm, and a tensile strength of 11.95 N / 5 cm.

[0035] Example 3: Three-dimensional porous material composed of type I fiber layers Same as Example 1, except that: the single-layer mesh weight is changed to 2g / m²; the number of rolls is changed to 4 (four-layer structure). The finished product has an average thickness of 32.95 μm, with a thickness fluctuation of ±2.15 μm; a porosity of 73.60%, an average pore size of 3.36 μm, and a tensile strength of 12.15 N / 5 cm.

[0036] Example 4: Three-dimensional porous material composed of type I fiber layers Same as Example 1, except that: the single-layer mesh weight is changed to 1.6 g / m²; the number of rolls is changed to 5 (five-layer structure). The finished product has an average thickness of 31.35 μm, with a thickness fluctuation of ±2.07 μm; a porosity of 72.26%, an average pore size of 3.28 μm, and a tensile strength of 12.94 N / 5 cm.

[0037] Summary: As can be seen from Examples 1-4, the thickness fluctuation range can be reduced through lamination and bonding processes.

[0038] Example 5: Three-dimensional porous material composed of type I fiber layers Similar to Example 1, except that: a metal mesh 2 with a height of 4cm and a width of 3cm is added below the spinning box 1 at a distance of 3cm from the outlet end face of the spinneret hole, and connected to a DC power supply 3 with a voltage of 2kV; The finished product has an average thickness of 32.06 μm, with a thickness fluctuation of ±1.36 μm; a porosity of 72.87%, an average pore size of 3.09 μm, and a tensile strength of 11.08 N / 5 cm.

[0039] Example 6: Three-dimensional porous material composed of type I fiber layers Same as Example 5, except that the voltage of the metal mesh enclosure 2 is changed to 0.5kV; The finished product has an average thickness of 31.52 μm, with a thickness fluctuation of ±1.47 μm; a porosity of 72.87%, an average pore size of 3.43 μm, and a tensile strength of 12.06 N / 5 cm.

[0040] Example 7: Three-dimensional porous material composed of type I fiber layers Same as Example 5, except that: the voltage of the metal mesh enclosure 2 is changed to 4kV; the single layer mesh weight is 2g / m², and 4 layers are stacked (same as the mesh weight and number of layers in Example 3). The finished product has an average thickness of 29.18 μm, with a thickness fluctuation of ±1.33 μm; a porosity of 70.19%, an average pore size of 3.43 μm, and a tensile strength of 10.09 N / 5 cm.

[0041] Summary: Compared with Examples 1 and 3, Examples 5-7 show that adding an electric current treatment to the metal mesh can further reduce thickness fluctuations, especially in Example 7 where the fluctuation is less than ±1.5μm.

[0042] Example 8: Three-dimensional porous material composed of type II fiber layers Polypropylene (PP) was selected as the fiber-forming raw material. A melt spinning device with a spinning aperture of 0.35 mm was used. The chamber temperature and hot air temperature were both set at 250℃, with a hot air fan frequency of 1000Hz and a cold air fan frequency of 900Hz. The weight of the spun fiber in a single layer was 4 g / m². Two rolls of the 4 g / m² fiber were stacked together and passed through a heated roller mill at a pressure of 2.5 MPa and a temperature of 120℃. The finished material (two layers) had an average thickness of 31.56 μm, with a thickness fluctuation range of ±2.83 μm. Within each single layer, >80% of the fiber diameter was distributed between 5-20 μm, exhibiting a single-peak distribution; >60% of the fiber diameter was distributed between 7-15 μm. The porosity was 72.44%, the average pore size was 9.06 μm, and the tensile strength was 5.31 N / 5 cm.

[0043] Example 9: Three-dimensional porous material composed of type II fiber layers Same as Example 8, except that the single-layer mesh weight is changed to 2g / m², and 4 layers are stacked (the same number of layers as in Example 3). The finished product has an average thickness of 30.86 μm, with a thickness fluctuation of ±2.83 μm; a porosity of 72.44%, an average pore size of 8.99 μm, and a tensile strength of 6.02 N / 5 cm; fiber diameter distribution is shown in [reference needed]. Figure 4 .

[0044] Example 10: Three-dimensional porous material composed of type II fiber layers Same as in Example 8, but with the addition of a metal mesh enclosure 2 and power supply (same as in Example 5, voltage 2kV), single layer mesh weight 4g / m² stacked 2 layers; The finished product has an average thickness of 30.22 μm, with a thickness fluctuation of ±1.43 μm; a porosity of 71.22%, an average pore size of 9.25 μm, and a tensile strength of 5.85 N / 5 cm.

[0045] Summary: Comparing Examples 8 and 9 with Examples 1 and 3, and comparing Example 10 with Example 5, it can be seen that increasing the spinneret diameter can increase the average orifice diameter, which is suitable for large particle size or low flowability electrolyte slurries.

[0046] Example 11: Three-dimensional porous material composed of type III fiber layers Polypropylene (PP) was selected as the fiber-forming raw material. The melt spinning equipment had two types of spinning holes, 0.28mm and 0.35mm, arranged alternately in the die head. The spinning box temperature was set to 250℃, the hot air temperature was 250℃, the hot air fan frequency was 1000Hz, and the cold air fan frequency was 900Hz. The single-layer web weight of the spun fiber 4 was 4g / m². Two rolls of the above 4g / m² fiber layers were stacked together and passed through a heated rolling mill with a rolling pressure of 2.5MPa and a temperature of 120℃. The finished material layer (double-layer, bimodal distribution) had an average thickness of 30.27μm, with a thickness fluctuation range of ±2.53μm. >80% of the fibers had a diameter distribution of 1-20μm and exhibited a bimodal distribution; ≥30% of the fibers had a diameter distribution of 1.5-3.5μm; and ≥20% of the fibers had a diameter distribution of 4.5-10µm. The fiber diameter distribution is as follows: Figure 5 As shown, the porosity is 71.27%, the average pore size is 6.31 μm, and the tensile strength is 9.13 N / 5 cm.

[0047] Example 12: Three-dimensional porous material composed of type III fiber layers Same as Example 11, except that the single-layer mesh weight is changed to 2g / m², and 4 layers are stacked (the same number of layers as in Example 3). The finished product has an average thickness of 29.58 μm, with a thickness fluctuation of ±2.12 μm; a porosity of 70.59%, an average pore size of 5.86 μm, and a tensile strength of 9.75 N / 5 cm.

[0048] Summary: Comparing Examples 11 and 12 with Examples 1, 3, 8, and 9, it can be seen that after being laminated, the bimodal fiber web has a smaller thickness fluctuation, higher strength than the single-peak coarse fiber web (Type II), and a larger pore size than the single-peak fine fiber web (Type I), making it suitable for scenarios that balance larger pore size and higher strength.

[0049] Example 13 Three-dimensional porous material composed of type III fiber layers Same as in Example 11, but with the addition of a metal mesh enclosure 2 and power supply (voltage 2kV, the metal mesh enclosure 2 is located 5cm below the spinneret outlet end face of the box, with dimensions of 5cm high and 4cm wide), single layer mesh weight 4g / m² stacked 2 layers; The finished product has an average thickness of 30.69 μm, with a thickness fluctuation of ±1.27 μm; a porosity of 70.01%, an average pore size of 5.37 μm, and a tensile strength of 9.33 N / 5 cm.

[0050] Example 14: Three-dimensional porous materials composed of type I fiber layers (different raw materials) PP was used as the raw material, and a single-die melt spinning equipment with a spinning hole of 0.28mm was used. The spinning box temperature was set to 250℃, the hot air temperature was 250℃, the hot air fan frequency was 1000Hz, the cold air fan frequency was 900Hz, and the fiber single-layer web weight was 4g / m². This layer was self-adhesive through residual heat. The fiber diameter distribution was 0.5-5.0μm, and more than 60% of the fibers had a diameter distribution of 1-3μm.

[0051] Using POE as raw material, a melt spinning device with a spinning die head of 0.28mm was used. The spinning box temperature was set to 200℃, the hot air temperature was 200℃, the hot air fan frequency was 900Hz, the cold air fan frequency was 800Hz, and the fiber single-layer web weight was 4g / m². This layer was self-adhesive through residual heat. The fiber diameter distribution was 0.5-5.0μm, and more than 60% of the fibers had a diameter distribution of 1-3μm.

[0052] Two rolls of the aforementioned 4 g / m² fiber layer were stacked together and passed through a heated rolling mill at a pressure of 2.5 MPa and a temperature of 120°C. The finished material layer (double-layered, with a metal mesh enclosure 2 and energized at 2 kV, dual-material) had an average thickness of 29.17 μm, a thickness fluctuation range of ±2.45 μm, a porosity of 70.18%, an average pore size of 3.98 μm, and a tensile strength of 10.3 N / 5 cm. Due to the presence of the POE layer, this type of material layer has the function of self-pressurization or hot pressing to bond with other materials.

[0053] Example 15: Three-dimensional porous material composed of type III fiber layers Same as Example 11 (bimodal distribution), but hot air bonding is used instead of hot rolling: the mesh is laid (single layer 4g / m², stacked 2 layers) under the condition of energizing the metal mesh (2kV), and then bonded with hot air at 125°C; The finished product has an average thickness of 34.26 μm, with a thickness fluctuation of ±2.32 μm; a porosity of 74.16%, an average pore size of 6.29 μm, and a tensile strength of 8.85 N / 5 cm.

[0054] Example 16: Three-dimensional porous material composed of type III fiber layers

[0055] Same as Example 11 (bimodal distribution, energized and voltage is 2kV), but the raw material is changed to polyamide (PA): spinning box temperature 280℃, hot air 280℃, hot air fan 1000Hz, cold air 900Hz; single layer web weight 4g / m², stacked 2 layers, hot rolling (2.5MPa, 120℃). The finished product has an average thickness of 30.67 μm, with a thickness fluctuation of ±2.28 μm; a porosity of 71.64%, an average pore size of 6.21 μm, and a tensile strength of 14.72 N / 5 cm.

[0056] Example 17 Three-dimensional porous material composed of type III fiber layers Same as Example 11 (bimodal distribution, energized and voltage is 2kV), but the raw material is changed to polyester (PET): spinning box temperature 290℃, hot air 290℃, hot air fan 800Hz, cold air 700Hz; single layer web weight 3g / m², stacked 2 layers, hot rolling (2.0MPa, 120℃). The finished product has an average thickness of 24.53 μm, with a thickness fluctuation of ±2.45 μm; a porosity of 66.97%, an average pore size of 6.76 μm, and a tensile strength of 13.86 N / 5 cm.

[0057] Example 18 Three-dimensional porous material composed of type III fiber layers (double layer, electrically conductive with a voltage of 2kV, bimodal distribution, dual material) Two different raw materials were used to form webs, both with a bimodal distribution (same as the die head in Example 11 and energized at 2kV), and then laminated: First layer: PP, process parameters are the same as in Example 11 (box temperature 250℃, hot air temperature 250℃, hot air fan frequency 1000Hz, cold air fan frequency 900Hz), single layer mesh weight 4g / m², self-adhesive with residual heat; Second layer: APAO, chamber temperature 170℃, cold air pressure 0.8MPa, single layer mesh weight 4g / m², also powered on with voltage 2kV; after stacking two layers, hot rolling (roller pressure 3MPa, 120℃). The finished product has an average thickness of 30.37 μm, with a thickness fluctuation of ±2.67 μm; a porosity of 70.18%, an average pore size of 7.03 μm, and a tensile strength of 8.06 N / 5 cm.

[0058] Example 19 Three-dimensional porous material composed of type III fiber layers (double layer, bimodal distribution, energized at 2kV, three materials) A bimodal distribution (same as the die head in Example 11 and energized at 2kV) was used with two raw materials: First layer: PP, chamber temperature 250℃, hot air temperature 250℃, fan 900 / 800Hz, web thickness 3g / m²; Second layer: PIB / SBS (mass ratio 1:5), chamber temperature 160℃, web thickness 4g / m²; After stacking the two layers, hot rolling was performed (2MPa, 115℃). The finished product has an average thickness of 26.25 μm, with a thickness fluctuation of ±2.36 μm; a porosity of 71.01%, an average pore size of 6.18 μm, and a tensile strength of 8.32 N / 5 cm.

[0059] Example 20: Three-dimensional porous material composed of type III fiber layers The system employs a series dual-die head design (i.e., the fibers from the first die head travel a certain distance on the mesh belt before being received from the second die head, equivalent to in-situ lamination): the raw materials are all PE / APP / EVA (mass ratio of 8:1:2), and the two dies have the same parameters: a bimodal distribution die head (0.28mm and 0.35mm spinning holes are arranged alternately), the chamber is 250℃, the hot air is 250℃, the fan is 1000 / 900Hz, both are powered on and the voltage is 2kV, and the web weight of each die head is 3g / m²; the two layers rely on residual heat to self-bond, without additional rolling; The finished product has an average thickness of 23.21 μm, with a thickness fluctuation of ±2.75 μm; a porosity of 71.90%, an average pore size of 5.98 μm, and a tensile strength of 7.93 N / 5 cm.

[0060] Example 21: Three-dimensional porous material composed of type III fiber layers Same as Example 11 (double-peak distribution, energized and with a voltage of 2kV), but with adjusted process parameters: the mesh surround position is 5cm below the spinneret outlet end face (5cm high, 4cm wide); the spinning box temperature is 230℃, the hot air temperature is 220℃, and the fan speed is 800 / 700Hz; the web weight is 3.5g / m², stacked in 2 layers, and hot rolled (2MPa, 110℃). The finished product has an average thickness of 26.27 μm, with a thickness fluctuation of ±1.82 μm; a porosity of 71.27%, an average pore size of 6.86 μm, and a tensile strength of 9.7 N / 5 cm.

[0061] The following are comparative implementation cases: Comparative Example 1 Same as Example 1, but without lamination: single-layer web weight 8g / m², only one layer, directly hot rolled (same pressure and temperature). The finished product has an average thickness of 31.56 μm, with a thickness fluctuation of ±4.86 μm; a porosity of 71.54%, an average pore size of 3.27 μm, and a tensile strength of 11.31 N / 5 cm.

[0062] Comparative Example 2 Same as Comparative Example 1, but with the addition of metal mesh 2 and energization (2kV): Single layer 8g / m², single layer rolled after energization; The finished product has an average thickness of 30.93 μm and a thickness fluctuation of ±4.17 μm; a porosity of 71.88%, an average pore size of 3.06 μm, and a tensile strength of 10.93 N / 5 cm.

[0063] Summary: Compared with Examples 1 and 5, Comparative Examples 1 and 2 showed that even with the addition of a metal mesh, the thickness fluctuation was greater than ±4μm when no layers were stacked.

[0064] Comparative Example 3 Same as Example 6 (energized at 0.5kV, two layers stacked, single layer mesh weight 4g / m²), but the voltage is reduced to 0.4kV: The finished product has an average thickness of 32.86 μm, with a thickness fluctuation of ±2.42 μm (not reduced to below ±1.5 μm, but still less than ±3 μm); a porosity of 73.53%, an average pore size of 4.53 μm, and a tensile strength of 9.72 N / 5 cm.

[0065] Comparative Example 4 Same as Example 6, but the voltage is increased to 6kV: The finished product has an average thickness of 29.17 μm and a thickness fluctuation of ±1.36 μm (small fluctuation); however, the fiber diameter range becomes 0.3-4.0 μm (unimodal distribution, >60% in 0.8-2.5 μm), and the average pore size is only 1.71 μm; the porosity is 70.18%, and the tensile strength is 11.12 N / 5 cm.

[0066] Summary: Comparative Examples 3 and 4 show that there is an upper limit to the voltage. Exceeding the reasonable range (>4kV) will damage the pore size characteristics of the material and should be controlled within 0.5 to 4kV.

[0067] Comparative Example 5 Same as Example 8 (spinning hole diameter is 0.35mm, single-peak coarse fiber), but without lamination: single-layer web weight is 8g / m², single-layer pressing; The finished product has an average thickness of 31.28 μm, with a thickness fluctuation of ±5.65 μm; a porosity of 72.19%, an average pore size of 9.73 μm, and a tensile strength of 5.16 N / 5 cm.

[0068] Comparative Example 6 Instead of using a single-layer bimodal distribution, two single layers (type A and type B) with different diameter distributions are directly stacked: First layer: same as in Example 1 (fine fiber, spinning hole diameter of 0.28 mm, web weight of 4 g / m²); Second layer: same as in Example 8 (coarse fiber, spinning hole diameter of 0.35 mm, web weight of 4 g / m²). Hot rolling (2.5MPa, 120℃) after stacking two layers; The finished product has an average thickness of 33.15 μm, with a thickness fluctuation of ±4.61 μm; a porosity of 73.76%, an average pore size of 6.81 μm, and a tensile strength of 7.92 N / 5 cm.

[0069] Summary: Comparative Examples 5 and 6 show that even bimodal distributions of single-layered structures with different diameters cannot effectively reduce thickness fluctuations, and the thickness fluctuations are still relatively large.

[0070] Comparative Example 7 Similar to Comparative Example 6, but with a web weight of 2g / m² per layer, four layers (two of each): two fine fiber layers (spinning hole diameter of 0.28mm, single-layer web weight of 2g / m²), and two coarse fiber layers (spinning hole diameter of 0.35mm, single-layer web weight of 2g / m²), alternatingly stacked and then rolled. The finished product has an average thickness of 32.61 μm, with a thickness fluctuation of ±4.37 μm; a porosity of 73.33%, an average pore size of 8.15 μm, and a tensile strength of 7.61 N / 5 cm.

[0071] Comparative Example 8 Similar to Comparative Example 6, but with a different number of layers: three fine fiber layers (spinning hole diameter of 0.28 mm, single-layer web weight of 1.6 g / m²) and two coarse fiber layers (spinning hole diameter of 0.35 mm, single-layer web weight of 1.6 g / m²) were used, for a total of five layers laminated and rolled. The finished product has an average thickness of 31.85 μm and a thickness fluctuation of ±4.37 μm; a porosity of 92.69%, an average pore size of 8.93 μm, and a tensile strength of 7.26 N / 5 cm.

[0072] Summary: Comparative examples 7 and 8 show that even with multiple layers, as long as it is not a single-layer bimodal distribution (but rather belongs to two different types of single-peak layers), the thickness fluctuation is still relatively large.

[0073] Comparative Example 9 Same as Example 11 (bimodal distribution die), but without lamination: single-layer web weight 8g / m², single-layer rolling; The finished product has an average thickness of 32.51 μm, with a thickness fluctuation of ±4.93 μm; a porosity of 73.25%, an average pore size of 6.95 μm, and a tensile strength of 7.95 N / 5 cm.

[0074] Comparative Example 10 Same as Comparative Example 9, but with the addition of a metal mesh enclosure 2 energized (voltage is 2kV): single layer mesh weight is 8g / m², and single layer is rolled after energization; The finished product has an average thickness of 31.55 μm, with a thickness fluctuation of ±4.02 μm; a porosity of 72.43%, an average pore size of 6.28 μm, and a tensile strength of 8.25 N / 5 cm.

[0075] Summary: Comparative Examples 9 and 10 show that even if the fiber diameter has a bimodal distribution, the thickness fluctuation of a single-layer web (without lamination) is still relatively large.

[0076] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A three-dimensional porous material, characterized in that, Used as a support layer for solid electrolyte film formation, its structure is a multilayer fiber network composite, wherein the composite consists of two or more fiber layers of the same type, namely type I, type II or type III, and the diameter distribution of each type of fiber layer satisfies the following conditions: The fiber diameter in the type I fiber layer has a unimodal distribution, and satisfies the following conditions: 0.5μm≤80% of the fibers have a diameter ≤5.0μm, and 1μm≤60% of the fibers have a diameter ≤3.5μm. The fiber diameter in the type II fiber layer is unimodal, and satisfies the following conditions: 5μm≤80% of the fibers have a diameter ≤20μm, and 7μm≤60% of the fibers have a diameter ≤15μm. The fiber diameter in the type III fiber layer exhibits a bimodal distribution, and satisfies the following conditions: 1μm≤80% of the fibers have a diameter ≤20μm, 1μm≤30% of the fibers have a diameter ≤3.5μm, and 4.5μm≤20% of the fibers have a diameter ≤10μm.

2. The three-dimensional porous material as described in claim 1, characterized in that, The raw materials for the three-dimensional porous material are selected from one or more of olefin-based polymers and block copolymers, polyamides, and polyesters.

3. The three-dimensional porous material as described in claim 2, characterized in that, The olefin-based polymers and block copolymers are selected from one or more of polypropylene, polyethylene, amorphous α-olefin copolymers, ethylene-butene copolymers and ethylene-octene copolymers, styrene-butadiene-styrene block copolymers, polyisobutylene, ethylene-vinyl acetate copolymers, and atactic polypropylene.

4. The three-dimensional porous material as described in claim 1, characterized in that, The average pore size of the three-dimensional porous material is ≥2μm.

5. The method for preparing a three-dimensional porous material as described in claim 1, characterized in that, First, spun fibers are sprayed out and laid into a web using a melt spinning process, and then the three-dimensional porous material is formed through a series of layering and bonding processes.

6. The method for preparing a three-dimensional porous material as described in claim 5, characterized in that, In the melt spinning process, a metal mesh enclosure connected to a DC power supply is provided on the path between the spinneret outlet and the receiving mesh belt, with the metal mesh enclosure 2-5 cm away from the end face of the spinneret outlet; the spun fibers ejected from the spinneret pass through the inside of the metal mesh enclosure and fall onto the receiving mesh belt.

7. The method for preparing a three-dimensional porous material as described in claim 6, characterized in that, The voltage value of the DC power supply is set to ≥0.5kV and ≤4kV.

8. The method for preparing a three-dimensional porous material as described in claim 5, characterized in that, The bonding process can be achieved by any one of the following methods: residual heat bonding, hot-press bonding, or hot-air bonding.

9. The method for preparing a three-dimensional porous material as described in claim 5, characterized in that, By simultaneously configuring spinnerets with a first aperture and a second aperture on the die head during the melt spinning process, and with the first aperture not equal to the second aperture, the resulting Type III fiber layer exhibits a bimodal distribution.

10. The method for preparing a three-dimensional porous material as described in claim 6, characterized in that, The metal mesh enclosure is either in use or not in use. In the in use state, the thickness fluctuation of the obtained three-dimensional porous material does not exceed 1.5 μm. When not in use, the thickness fluctuation of the obtained three-dimensional porous material does not exceed 3μm.

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