Nonwoven fabric, separator and battery

Abstract

The present invention provides a nonwoven fabric, a separator, and a battery, wherein the nonwoven fabric comprises main fibers including circular cross-section fibers and modified cross-section fibers, and the circumferential coefficient of the cross section of at least some of the modified cross-section fibers is X L and 1 <X L ≦5. The present invention can improve the strength of the nonwoven fabric while maintaining a thin thickness, thereby improving the safety, cycle life, energy density, and other performances of the battery.

Description

[Technical Field]

[0001] The present invention relates to the technical field of nonwoven materials, and specifically to nonwoven fabrics, separators and batteries. [Background technology]

[0002] Nonwoven fabrics have properties such as naturally large pore size, high porosity, and high temperature resistance, and therefore have excellent application prospects in the field of energy storage devices such as batteries, and can be formed into nonwoven fabric separators for batteries, for example. However, in related art, it is generally difficult to achieve both strength and thickness in nonwoven fabrics, and if the thickness of a nonwoven fabric is thin, its strength is low, which is detrimental to performance such as battery safety and cycle life, and if the thickness of a nonwoven fabric is increased, performance such as battery energy density is affected. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides a nonwoven fabric, a separator, and a battery, which can improve the strength of the nonwoven fabric while maintaining its thickness thin, thereby achieving performance such as battery safety, cycle life, and energy density. [Means for solving the problem]

[0004] In one aspect of the present invention, a nonwoven fabric is provided, comprising main fibers including circular cross-section fibers and modified cross-section fibers, and the perimeter coefficient of the cross section of at least some of the modified cross-section fibers is X L and 1 <X L ≦5.

[0005] In another aspect of the present invention, there is provided a separator comprising the nonwoven fabric described above.

[0006] In a further aspect of the present invention, there is provided a battery comprising a positive plate, a negative plate and the separator described above, said separator being between said positive plate and said negative plate.

[0007] In the present invention, the main fibers of the nonwoven fabric include circular cross-section fibers and irregular cross-section fibers, and the circumferential coefficient X of the cross section of at least some of the irregular cross-section fibers is L is 1 <X L By controlling the ratio of the main fibers to the total fiber length so as to satisfy the following relationship, the introduction of these specific forms of main fibers is advantageous for sufficient adhesion between the fibers in the nonwoven fabric, and it is possible to form a strong mesh structure. This significantly improves the strength of the nonwoven fabric, while at the same time keeping the thickness of the nonwoven fabric thin. Specifically, the maximum tensile strength of the nonwoven fabric in the longitudinal direction is 469 kgf / cm. 2 Above, 540kgf / cm 2 The transverse tensile strength can reach up to 300kgf / cm 2 Above, and 330kgf / cm 2 The thickness of the nonwoven fabric can be 25 μm or less, and the present invention provides a thin, high-strength nonwoven fabric that can be used as a separator in electrochemical energy storage devices such as lithium ion batteries, thereby improving the safety, cycle life, energy density, and other performance of the electrochemical energy storage devices such as lithium ion batteries. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of the cross-sectional (cross-shaped) shape of a modified cross-section fiber in one embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a schematic diagram of the cross-sectional shape (semicircular ring shape) of a modified cross-section fiber in another example of the present invention. [Figure 3] FIG. 3 is a schematic diagram of the cross-sectional shape (7 / 8 of a circle) of a modified cross-section fiber in another embodiment of the present invention (A in FIG. 3 indicates the circular angle, and B in FIG. 3 indicates the depth of the deepest part and the width of the widest part). [Figure 4] FIG. 2 is a schematic diagram of the cross-sectional shape (eight-pointed star) of a modified cross-section fiber in another embodiment of the present invention. [Figure 5] FIG. 2 is a schematic diagram of the cross-sectional shape (S-shape) of a modified cross-section fiber in another example of the present invention. [Figure 6]FIG. 2 is a schematic diagram of the cross-sectional shape (deca-pointed star) of a modified cross-section fiber in another example of the present invention. [Figure 7] FIG. 2 is a schematic diagram of the cross-sectional shape (U-shaped) of a modified cross-section fiber in another embodiment of the present invention. [Figure 8] FIG. 2 is a schematic diagram of the cross-sectional shape (twelve-pointed star) of a modified cross-section fiber in another embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram of the cross-sectional shape (hexagonal star) of a modified cross-section fiber in another embodiment of the present invention. [Figure 10] FIG. 2 is a schematic diagram of the cross-sectional shape (crescent shape) of a modified cross-section fiber in another example of the present invention. [Figure 11] FIG. 2 is a schematic diagram of the cross-sectional shape (four-pointed star) of a modified cross-section fiber in another example of the present invention. [Figure 12] FIG. 2 is a schematic diagram of the cross-sectional shape (T-shaped) of a modified cross-section fiber in another example of the present invention. [Figure 13] FIG. 2 is a schematic diagram of the cross-sectional shape (cross-shaped) of a modified cross-section fiber in another example of the present invention. [Figure 14] FIG. 2 is a schematic diagram of the cross-sectional shape (crescent shape) of a modified cross-section fiber in another example of the present invention. [Figure 15] FIG. 2 is a schematic diagram of the cross-sectional shape (W-shaped) of a modified cross-section fiber in another example of the present invention. [Figure 16] FIG. 2 is a schematic diagram of the cross-sectional shape (N-shaped) of a modified cross-section fiber in another example of the present invention. [Figure 17] FIG. 2 is a schematic diagram of the cross-sectional shape (U-shaped) of a modified cross-section fiber in another example of the present invention. [Figure 18] FIG. 2 is a schematic diagram of the cross-sectional shape (circular opening) of a modified cross-section fiber in another example of the present invention. [Figure 19] FIG. 2 is a schematic diagram of the cross-sectional shape (pentagon) of a modified cross-section fiber in another example of the present invention. [Figure 20] FIG. 2 is a schematic diagram of the cross-sectional shape (non-perfect circular ring shape) of a modified cross-section fiber in another example of the present invention. [Figure 21] 1 is a differential scanning calorimetry curve of the fiber. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to allow those skilled in the art to better understand the means of the present invention, the present invention will be described in more detail below. The specific embodiments listed below are intended to illustrate the principles and features of the present invention, and the listed examples are only used to interpret the present invention and do not limit the scope of the present invention. Any other embodiments obtained by those skilled in the art based on the examples of the present invention without any creative work shall fall within the protection scope of the present invention.

[0010] With the development of new energy vehicles, 3C and other technological fields, lithium-ion batteries are increasingly being used widely. At the same time, the performance requirements for lithium-ion batteries, such as energy density and safety, are also becoming increasingly higher. For example, the theoretical energy density of conventional power battery systems is approaching its technical limit, and it is becoming increasingly difficult to break through this limit.

[0011] Specifically, liquid batteries require a separator to separate the positive and negative electrodes and an electrolyte for ion conduction, and their safety remains an issue that urgently needs improvement. Conventional separators, such as polyolefin-based separators, in liquid batteries have poor performance in areas such as thermal stability, which poses significant obstacles to the safety of liquid batteries.

[0012] Compared with liquid batteries, semi-solid batteries and solid batteries have advantages in safety, energy density, and cycle life, and have attracted widespread attention. The separator in semi-solid batteries and solid batteries can play the role of electrolyte instead of electrolyte, which places high demands on separator performance such as strength, while semi-solid batteries still require electrolyte and separator for ion conduction and insulation, respectively, which places high demands on separator performance such as strength and heat resistance.

[0013] Nonwoven fabrics have naturally large pore sizes and high porosity, making them suitable for use in the field of energy storage devices such as batteries. For example, they can be used as nonwoven fabric separators. Nonwoven fabric separators can be widely used in fields such as lead-acid batteries, alkaline batteries, nickel-metal hydride batteries, and supercapacitors. They have advantages such as high temperature resistance and high porosity, and their safety advantages over conventional polyolefin-based separators make them particularly suitable for use in large batteries. They are therefore attracting attention from the lithium battery industry as they are suitable for energy storage and power batteries that require large sizes and long cycle lives.

[0014] However, in related technologies, it is usually difficult to achieve both strength and thickness in nonwoven fabrics. Reducing the thickness of a nonwoven fabric results in a corresponding weakening of its strength, which is detrimental to performance such as battery safety and cycle life, while increasing the thickness of the nonwoven fabric affects performance such as battery energy density.

[0015] In view of this, an embodiment of the present invention provides a nonwoven fabric, comprising a main fiber including a circular cross-section fiber and a modified cross-section fiber, wherein the perimeter coefficient of the cross section 1 of at least a portion (i.e., a part or all) of the modified cross-section fiber is X L and 1 <X L ≦5.

[0016] Specifically, the nonwoven fabric may have one type of modified cross-section fiber (i.e., the cross-section 1 of these modified cross-section fibers has the same shape), or may have a plurality of different types of modified cross-section fibers (i.e., the cross-section 1 of at least some of the modified cross-section fibers has a different shape). When a plurality of different types of modified cross-section fibers are present, the perimeter coefficient X of the cross-section 1 of at least one type of modified cross-section fiber is L is 1 <X L ≦5, that is, the perimeter coefficient X of the cross section 1 of one modified cross-section fiber L is 1 <X L ≦5, and the perimeter coefficient X of the cross section 1 of at least two modified cross-section fibers L is 1 <X L ≦5 may be satisfied.

[0017] Illustratively, the perimeter coefficient of the cross section 1 of at least some of the modified cross-section fibers may be 1.5, 2, 3, 4, 5, or a range consisting of any two of them.

[0018] Specifically, the modified cross-section fiber is a non-circular cross-section fiber, that is, its cross section 1 is non-circular, and the cross section 1 is perpendicular to the axial direction of the modified cross-section fiber (generally also the length direction of the modified cross-section fiber). The perimeter coefficient X of the cross section 1 of the modified cross-section fiber L is the ratio of the perimeter C0 of the cross section 1 of the modified cross section fiber to the perimeter C1 of a circle having the same area as the cross section 1 of the modified cross section fiber (i.e., X L =C0 / C1), and can be measured according to the circumference coefficient measurement method in the People's Republic of China textile industry standard FZ / T 50002-2013 (chemical fiber irregularity degree test method).

[0019] Specifically, the cross section of a circular cross section fiber is essentially circular, and the cross section is perpendicular to the axial direction of the circular cross section fiber (which is also generally the length direction of the circular cross section fiber).

[0020] In the nonwoven fabric, the main fiber is the skeleton of the nonwoven fabric, and the circular main fiber (i.e., the circular cross section fiber) and the irregular cross section fiber (i.e., the irregular cross section fiber) are simultaneously introduced into the nonwoven fabric, and the circumferential coefficient X of the cross section 1 of the irregular main fiber is L 1 <X L By controlling the ratio of the tensile strength of the nonwoven fabric to 5, the strength of the nonwoven fabric can be significantly improved while the thickness of the nonwoven fabric can be kept thin. Specifically, the maximum tensile strength of the nonwoven fabric in the longitudinal direction is 469 kgf / cm 2 Above, 540kgf / cm 2 The transverse tensile strength can reach up to 300kgf / cm 2 Above, and 330kgf / cm 2The thickness of the nonwoven fabric can be 25 μm or less. Thus, the present invention provides a thin, high-strength nonwoven fabric that can be used as a separator and is applicable to electrochemical energy storage devices such as lithium ion batteries, and that combines the safety, cycle life, energy density, and other performances of electrochemical energy storage devices such as lithium ion batteries.

[0021] According to the research of the inventors, the circumferential coefficient X of the modified cross section fiber L If is greater than 5, the specific surface area of ​​the fiber increases, but the fiber surface will have too many microstructures such as grooves and protrusions, which conversely makes it easier for the modified cross-section fibers to become entangled with each other, and the main fibers will become entangled with each other and form clumps, making it difficult to disperse them sufficiently uniformly, which is disadvantageous for obtaining a nonwoven fabric with highly uniform performance.

[0022] Generally, nonwoven fabrics also contain viscose fiber, the main fiber of which has a higher softening point than viscose fiber. Viscose fiber is mainly used to bond components such as the main fiber in nonwoven fabrics and improve the structural strength of the nonwoven fabric.

[0023] Specifically, in the manufacturing process of nonwoven fabrics, randomly dispersed fibers (including main fibers and viscose fibers) are usually shaped by a hot rolling process. The main fibers, which serve as the backbone of the nonwoven fabric structure, do not generally melt, while the viscose fibers melt partially or completely on the surface, penetrating into the fiber surface and structures such as gaps, voids, and unevenness of the fibers. After cooling and hardening, they generate interlocking forces at the interface regions, which cause the fibers in the nonwoven fabric to adhere to each other, realizing strong bonds between the fibers and providing structural strength to the nonwoven fabric.

[0024] Generally, when the fiber length and cross-sectional area of ​​the fiber are the same, the specific surface area of ​​the modified cross-section fiber is significantly higher than that of the circular cross-section fiber. L is 1 <X LBy introducing modified cross-section fibers that satisfy a specific surface area of ​​≦5, the high specific surface area of ​​the modified cross-section fibers and the pore structure that allows capillary action to form between the fibers can be utilized to more fully and quickly infiltrate the molten viscose fibers, greatly increasing the bonding area between the fibers and significantly improving the structural strength of the nonwoven fabric.

[0025] In some embodiments, grooves 10 can be formed on the surface of the modified cross-section fibers, which further strengthens the anchoring effect of the fiber bonding. The molten viscose fibers penetrate into the fine grooves 10 on the surface of the modified cross-section fibers due to capillary attraction, and the fibers cannot move relative to each other after cooling and hardening, thereby achieving strong bonding between the fibers and further improving the structural strength of the nonwoven fabric.

[0026] Specifically, in the modified cross-section fiber, the grooves 10 extend along the axial direction of the modified cross-section fiber and can penetrate the modified cross-section fiber in the axial direction of the modified cross-section fiber, that is, the length of the grooves 10 on the modified cross-section fiber is equal to the length of the modified cross-section fiber.

[0027] In addition, the modified cross-section fiber may have one or more grooves 10, and if there are more than one grooves 10, these grooves 10 can be distributed specifically along the circumferential direction of the modified cross-section fiber.

[0028] Specifically, in the modified cross-section fiber, the number of grooves 10 may be 16 or less, that is, 1 to 16 grooves 10 can be provided in one modified cross-section fiber, and the number of grooves 10 may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16, etc., which is advantageous in further improving the structural strength of the nonwoven fabric.

[0029] Generally, there are multiple modified cross-section fibers in a nonwoven fabric, and the numbers of grooves 10 on these modified cross-section fibers may be the same or different. As described above, the nonwoven fabric may have at least one shape of modified cross-section fiber, i.e., one type of modified cross-section fiber or multiple types of modified cross-section fibers, and if multiple types of modified cross-section fibers are present, the numbers of grooves 10 on any two types of modified cross-section fibers may be the same or different.

[0030] Further research has shown that, from the viewpoint of sufficient wetting, it is preferable that the width w of the widest point of the groove 10 is 15% or more of the diameter D of the circumscribed circle 100 of the cross section 1 of the modified cross-section fiber, which is more advantageous in excluding air inside the groove 10, thereby allowing the fluid to wetting out inside the groove 10 more quickly and thoroughly.

[0031] From the viewpoint of structural strength, it is preferable that the depth h of the deepest point of the groove 10 is 75% or less of the diameter D of the circumscribed circle 100 of the cross section 1 of the modified cross section fiber; in this way, the bottom of the groove 10 is less likely to become a weak point in the structure itself, is less likely to tear under the action of related stresses, and can better maintain the original shape of the groove 10.

[0032] In some embodiments, in the modified cross-section fiber, the width w of the widest point of the groove 10 may be 15% or more of the diameter D of the circumscribed circle 100 of the cross section 1 of the modified cross-section fiber (i.e., w / D≧15%), and specifically, w / D may be 15% to 100%, for example, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or a range consisting of any two thereof, thereby further improving the structural strength of the nonwoven fabric.

[0033] In some embodiments, in the profiled cross-section fiber, the depth h of the deepest part of the groove 10 may be 75% or less of the diameter D of the circumscribed circle 100 of the cross-section 1 of the profiled cross-section fiber (i.e., h / D≤75%). Specifically, h / D can satisfy 0 < h / D≤75%. h / D can be, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or a range consisting of any two of them. In this way, the structural strength of the non-woven fabric can be further improved.

[0034] The width w of the widest part of the groove 10 refers to the distance between the two side wall surfaces of the widest part of the groove 10. That is, the width w of the widest part of the groove 10 is the maximum linear distance between the two side wall surfaces constituting the groove 10. Specifically, the groove 10 has two side wall surfaces, and the two side wall surfaces are respectively on the opposite sides of the groove 10 (that is, one side wall surface is on one side of the groove 10, and the other side wall surface is on the other side of the groove 10). The length of each of the two side wall surfaces in the length direction (axial direction) of the profiled cross-section fiber is equal to the length of the profiled cross-section fiber, and the maximum distance between the two side wall surfaces of the profiled cross-section fiber in the direction perpendicular to the length direction is the width w of the widest part of the groove 10.

[0035] For example, referring to FIGS. 1 to 19, the widest part of the groove 10 is the opening of the groove 10. At this time, specifically, the width w of the widest part of the groove 10 may refer to the linear distance between the two outermost end points of the contour lines of the cross-sections of the two side wall surfaces constituting the groove 10. That is, in the cross-section 1 of the profiled cross-section fiber (the cross-section 1 is perpendicular to the axial direction of the profiled cross-section fiber), the linear distance between the end points of the two side wall surfaces surrounding the groove 10 at the opening of the groove 10 is the width w of the widest part of the groove 10.

[0036] For example, referring to FIG. 20, the widest part of the groove is inside the groove 10. At this time, the width w of the widest part of the groove 10 is the distance between the two side wall surfaces of the groove 10 at the widest part.

[0037] Continuing to refer to Figures 1 to 20, the depth h of the deepest point of groove 10 (i.e., the maximum depth of groove 10) refers to the maximum vertical distance between the bottom of groove 10 (the bottom surface of groove 10 away from its opening) and the connecting line between the opposing end points of the opening of groove 10, and in the cross section 1 of the modified cross-section fiber (the cross section 1 is perpendicular to the axial direction of the modified cross-section fiber), the straight line between the end points of the opening of groove 10 on the two side wall surfaces surrounding groove 10 becomes the connecting line.

[0038] As can be understood, the above straight lines, connecting lines, and contour lines are intended to explain the width w of the widest point of groove 10 and the depth h of the deepest point of groove 10, and are all imaginary lines and do not have any actual structures.

[0039] Specifically, the shape of the cross section 1 of the modified cross section fiber may include, but is not limited to, a heart shape, a dumbbell shape, a crescent shape (see FIG. 10), a new moon shape (see FIG. 14), a non-perfect ring shape, a non-perfect circle shape, a multi-lobed clover shape, a polygonal shape, a letter shape, or a plum blossom shape, and may also be other regular or irregular shapes.

[0040] The central angle corresponding to the outer circular arc of a non-complete torus is smaller than the central angle corresponding to the outer circular arc of its complete concentric ring. For example, a non-complete torus may be a semi-torus (i.e., the central angle corresponding to the outer circular arc of a non-complete torus is 1 / 2 of the central angle corresponding to the outer circular arc of its complete concentric ring, as shown in Figure 2), or a two-thirds torus (i.e., the central angle corresponding to the outer circular arc of a non-complete torus is 2 / 3 of the central angle corresponding to the outer circular arc of its complete concentric ring), or a non-complete torus as shown in Figure 20.

[0041] The central angle α of a non-perfect circle (including a sector, a circular arc, and an open circle) is smaller than 360°. For example, a non-perfect circle includes a 7 / 8 circle (i.e., its central angle α is 7 / 8 of 360°, as shown in FIG. 3 (A in FIG. 3 shows the central angle, and B in FIG. 3 shows the depth h of the deepest point and the width w of the widest point)), a 3 / 4 circle (i.e., its central angle α is 3 / 4 of 360°), or a 2 / 3 circle (i.e., its central angle α is 2 / 3 of 360°), or a circle as shown in FIG. 18.

[0042] Illustratively, the multi-leaf cloverleaf includes a three-leaf cloverleaf or a four-leaf cloverleaf.

[0043] Illustratively, polygons include pentagons (as shown in FIG. 19) and may include poly-pointed stars, which include three-pointed stars, four-pointed stars (as shown in FIG. 11), five-pointed stars, six-pointed stars, eight-pointed stars (as shown in FIG. 4), decagrams (as shown in FIG. 6), twelve-pointed stars (as shown in FIG. 8), or sixteen-pointed stars (as shown in FIG. 9).

[0044] Exemplary letter shapes include a cross (shown in FIGS. 1 and 13), a double cross, a U-shape, a R-shape (shown in FIG. 7), a C-shape, an E-shape, an F-shape, a G-shape, an H-shape, a J-shape, a K-shape, an L-shape, an M-shape, an N-shape (shown in FIG. 16), an S-shape (shown in FIG. 5), a T-shape (shown in FIG. 12), a U-shape (shown in FIG. 17), a V-shape, a W-shape (shown in FIG. 15), an X-shape, a Y-shape, or a Z-shape.

[0045] Illustratively, the plum blossom shape includes a four-petal plum blossom shape, a five-petal plum blossom shape, or a six-petal plum blossom shape.

[0046] In some embodiments, the ratio of the mass of the modified cross-section fibers to the mass of the main fibers (the mass percentage content of the modified cross-section fibers in the main fibers) may be 5% to 60%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or a range consisting of any two thereof, which is advantageous in improving the structural strength of the nonwoven fabric.

[0047] In addition, the mass ratio of the circular cross-section fibers to the main fibers (mass percentage content of the circular cross-section fibers in the main fibers) may be 40% to 95%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or a range consisting of any two of these, which is advantageous in improving the structural strength of the nonwoven fabric.

[0048] In some embodiments, the ratio of the mass of the main fiber to the mass of the nonwoven fabric (i.e., the mass percent content of the main fiber in the nonwoven fabric) may be 60% to 85%, such as 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, or a range consisting of any two thereof, which is advantageous in improving the structural strength of the nonwoven fabric.

[0049] Fiber linear density indicates the degree of fiber thickness. All other conditions being equal, if the fibers are too thick, the nonwoven fabric will be too thick, which will be detrimental to the performance of the nonwoven fabric in battery separators and electrolyte membranes. Taking separators as an example, if the nonwoven fabric is too thick (linear density is too high), the nonwoven fabric will be too thick, resulting in increased ion transport resistance and changes in the diffusion coefficient of the separator, which will cause uneven transport of ions (lithium ions) and increase the unevenness of ion arrival at the electrode interface. The unevenness of ions entering and exiting the electrode through the separator will cause phenomena such as incomplete lithium embedding and release, and localized overcharge or overdischarge, which will affect the safety and lifespan of the battery.

[0050] Therefore, in some preferred embodiments, the linear density of the main fiber may be 0.4 dtex or less, i.e., the linear density of the circular cross-section fiber may be 0.4 dtex or less, and the linear density of the modified cross-section fiber may be 0.4 dtex or less, thereby preventing the nonwoven fabric from being too thick, making it more convenient for the application of the nonwoven fabric to battery separators and electrolyte membranes, and further improving the safety and cycle life of the battery.

[0051] Furthermore, the linear density of the main fibers (circular cross section fibers or modified cross section fibers) may be 0.05 dtex to 0.4 dtex, for example, 0.05 dtex, 0.06 dtex, 0.08 dtex, 0.1 dtex, 0.15 dtex, 0.2 dtex, 0.25 dtex, 0.3 dtex, 0.35 dtex, 0.4 dtex, or a range consisting of any two of them.

[0052] The linear densities of the circular cross-section fiber and the modified cross-section fiber may be the same or different, i.e., the linear density of the circular cross-section fiber may be greater than or less than the linear density of the modified cross-section fiber. In some preferred embodiments, the linear density of the viscose fiber is 0.8 dtex or less, which is more convenient for the application of nonwoven fabrics to battery separators and electrolyte membranes and improves battery performance such as safety and cycle life.

[0053] Furthermore, the linear density of the viscose fibers may be 0.2 dtex to 0.8 dtex, for example, 0.2 dtex, 0.3 dtex, 0.4 dtex, 0.5 dtex, 0.6 dtex, 0.7 dtex, 0.8 dtex, or a range consisting of any two of them.

[0054] The linear densities of the viscose fiber and the main fiber (circular cross section fiber or modified cross section fiber) may be the same or different, i.e., the linear density of the viscose fiber may be greater than or less than the linear density of the circular cross section fiber, and the linear density of the viscose fiber may be greater than or less than the linear density of the modified cross section fiber.

[0055] The length of the main fiber may be 1 mm to 3 mm, i.e., the length of the circular cross section fiber may be 1 mm to 3 mm, and the length of the modified cross section fiber may be 1 mm to 3 mm, which is advantageous in further improving the structural strength and other performance of the nonwoven fabric.

[0056] For example, the length of the main fibers (circular cross-section fibers and modified cross-section fibers) may be specifically 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3 mm, or a range consisting of any two thereof.

[0057] The circular cross section fibers and the modified cross section fibers may have the same length or different lengths, that is, the length of the circular cross section fibers may be greater than or less than the length of the modified cross section fibers.

[0058] The length of the viscose fibers may be 1 mm to 3 mm, for example, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3 mm, or a range consisting of any two of these.

[0059] The length of the viscose fiber and the length of the main fiber (irregular cross section fiber, circular cross section fiber) may be the same or different; that is, the length of the viscose fiber may be longer than or shorter than the length of the circular cross section fiber, and the length of the viscose fiber may be longer than or shorter than the length of the irregular cross section fiber.

[0060] The linear density of the main fiber and the linear density of the viscose fiber both refer to the average linear density, and are measured by a method commonly used in the art, such as GB / T 14335-2008 Chemical Fiber Staple Fiber Linear Density Test Method.

[0061] The length of the main fiber and the length of the viscose fiber both refer to the average length, and are measured by a method commonly used in the art, such as GB / T 14336-2008, test method for the length of chemical staple fiber.

[0062] In addition, the softening point of the main fiber is set to be higher than that of the viscose fiber so that the morphological structure of the nonwoven fabric does not change or substantially change when the main fiber melts or softens during processing when the viscose fiber melts and softens. In order to better maintain the morphological structure of the main fiber, the difference between the softening points of the main fiber and the viscose fiber is preferably 20°C or more. That is, the difference between the softening point of the circular cross section fiber and the viscose fiber may be 20°C or more, and the difference between the softening point of the modified cross section fiber and the viscose fiber may be 20°C or more.

[0063] The softening point of the circular cross section fiber and the softening point of the modified cross section fiber may be the same or different, that is, the softening point of the circular cross section fiber may be higher or lower than the softening point of the modified cross section fiber.

[0064] In some embodiments, the difference between the softening point of the main fiber (circular cross section fiber or modified cross section fiber) and the softening point of the viscose fiber is specifically 20 to 280°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 90°C, 95°C, 100°C, 110°C, 120°C, 125°C, The temperature may be 130°C, 135°C, 140°C, 145°C, 150°C, 160°C, 165°C, 170°C, 180°C, 190°C, 195°C, 200°C, 205°C, 210°C, 220°C, 230°C, 240°C, 250°C, 252°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, or a range consisting of any two thereof.

[0065] In some embodiments, the softening point of the main fiber (circular cross section fiber or modified cross section fiber) may be 240°C to 400°C, such as 240°C, 245°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, or a range consisting of any two thereof.

[0066] Specifically, the softening point of the viscose fiber may be equal to or greater than 120° C. In some embodiments, the softening point of the viscose fiber may be between 120° C. and 230° C., such as 120° C., 125° C., 130° C., 135° C., 140° C., 145° C., 150° C., 155° C., 160° C., 165° C., 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., 205° C., 210° C., 215° C., 220° C., 225° C., 230° C., or a range consisting of any two of these.

[0067] Specifically, the softening points of the main fiber and the viscose fiber can be measured using a differential scanning calorimeter (DSC). Specifically, the differential scanning calorimeter (DSC) measures the differential scanning calorimeter curve of the fiber using a programmed temperature rise method, and the starting temperature T at which the melting endothermic peak in the obtained curve begins to deviate from the baseline is determined. iindicates the softening point of the fiber (shown in Figure 21). For specific measurement methods, please refer to GBT 19466.3-2004 (Plastic Differential Scanning Calorimetry (DSC) Part 3: Determination of Melting and Crystallization Temperatures and Enthalpies).

[0068] In some embodiments, the viscose fibers may include one or more of unstretched polyester fibers, polyvinylidene fluoride fibers (PVDF), polyamide fibers, polyolefin fibers, copolyester fibers, and copolyamide fibers.

[0069] Optionally, the unstretched polyester fibers may comprise at least one of unstretched polyethylene terephthalate (PET) fibers or unstretched polybutylene terephthalate fibers.

[0070] Optionally, the polyolefin fibers may include one or more of polyethylene (PE) fibers, polypropylene (PP) fibers, polyvinyl chloride fibers, polystyrene fibers, polyethylene / polypropylene sheath-core fibers, polyethylene / polyethylene terephthalate sheath-core fibers, and polyethylene / polybutylene terephthalate sheath-core fibers.

[0071] Specifically, the adhesive fiber may be a bicomponent fiber made of two kinds of fiber materials, such as polyethylene and polypropylene, or polyethylene and polyethylene terephthalate, or polyethylene and polybutylene terephthalate. The bicomponent fiber may have structures such as side-by-side fibers, sheath-core fibers, multi-core composite fibers, and islands-in-the-sea composite fibers. Bicomponent fibers with corresponding structures can be manufactured according to conventional processes in the art.

[0072] Sheath-core fibers have a sheath-core structure, i.e., in the two types of fiber materials that form the bicomponent sheath-core fiber, one fiber material forms the core layer and the other fiber material forms the skin layer that is present on the surface of the core layer, and the skin layer is specifically wrapped around the core layer, thereby forming a sheath-core structure.

[0073] For example, the viscose fiber may include a PE / PP bicomponent fiber, which may specifically be a PE / PP bicomponent sheath-core fiber (i.e., the above-mentioned polyethylene / polypropylene sheath-core fiber), and the PE / PP bicomponent sheath-core fiber includes a core layer and a skin layer located on the surface of the core layer, and the skin layer may specifically be wrapped around the periphery of the core layer, with the core layer including PE and the skin layer including PP.

[0074] Optionally, the copolyester fibers may include at least one of copolyethylene terephthalate fibers (CoPET) or copolybutylene terephthalate fibers (CoPBT).

[0075] Alternatively, the copolyamide fiber may be formed by copolymerizing at least two types of polyamide monomers, and the at least two types of polyamides may include, for example, at least one or more of polyamide 6 (PA6), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 66 (PA66), polyamide 69 (PA69), polyamide 610 (PA610), polyamide 612 (PA612), and polyamide 1010 (PA1010). In other words, the copolyamide fiber may be a copolymer of at least two monomers of these polyamides.

[0076] Specifically, the copolyamide fiber may include at least one of a bipolymer, a terpolymer, or a tetrapolymer.

[0077] In some embodiments, the copolyamide fiber is PA6 / 6 (a polyamide 6 / 6 copolymer obtained by copolymerizing polyamide 6 monomers of different molecular weights or degrees of polymerization), PA6 / 66 (a polyamide 6 / 66 copolymer obtained by copolymerizing polyamide 6 monomers and PA66 monomers), PA6 / 66 / 12 (a polyamide 6 / 66 / 12 terpolymer obtained by copolymerizing polyamide 6 monomers, polyamide 66 monomers, and polyamide 12 monomers), PA6 / 66 / 69 (poly Polyamide 6 / 66 / 69 terpolymer obtained by copolymerizing amide 6 monomers, polyamide 66 monomers, and polyamide 69 monomers), PA6 / 66 / 610 (polyamide 6 / 66 / 610 terpolymer obtained by copolymerizing polyamide 6 monomers, polyamide 66 monomers, and polyamide 610 monomers), PA6 / 66 / 612 (polyamide 6 / 66 / 612 terpolymer obtained by copolymerizing polyamide 6 monomers, polyamide 66 monomers, and polyamide 612 monomers), PA 6 / 66 / 1010 (terpolymer polyamide 6 / 66 / 1010 obtained by copolymerizing polyamide 6 monomers, polyamide 66 monomers, and polyamide 1010 monomers), PA6 / 612 / 12 (terpolymer polyamide 6 / 612 / 12 obtained by copolymerizing polyamide 6 monomers, polyamide 612 monomers, and polyamide 12 monomers), PA6 / 610 / 12 (terpolymer polyamide 6 copolymerized by copolymerizing polyamide 6 monomers, polyamide 610 monomers, and polyamide 12 monomers) The polyamide may contain one or more of: PA6 / 610 / 12), PA6 / 66 / 69 / 12 (a tetrapolymer polyamide 6 / 66 / 69 / 12 obtained by copolymerizing a polyamide 6 monomer, a polyamide 66 monomer, a polyamide 69 monomer, and a polyamide 12 monomer); and PA6 / 66 / 11 / 12 (a tetrapolymer polyamide 6 / 66 / 11 / 12 obtained by copolymerizing a polyamide 6 monomer, a polyamide 66 monomer, a polyamide 11 monomer, and a polyamide 12 monomer).

[0078] In some embodiments, the main fiber (i.e., the circular cross-section fiber and the modified cross-section fiber) may comprise one or more of polyester fiber, polyolefin fiber, polyamide fiber, polyimide fiber (PI), polytetrafluoroethylene fiber (PTFE), polyphenylene sulfide fiber (PPS), polyether ether ketone fiber, polyacrylonitrile fiber (PAN), polycarbonate fiber, and aramid fiber; the polyester fiber may comprise one or more of polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate, and polyisophthalate resin; the polyolefin fiber may comprise one or more of polyethylene, polypropylene (PP), polyvinyl chloride, and polystyrene; and the polyamide fiber may comprise PA66.

[0079] Here, the material of the circular cross section fiber may be the same as or different from the material of the modified cross section fiber.

[0080] The thickness of the nonwoven fabric may be 25 μm or less, thereby maintaining a thin thickness while maintaining strong structural strength. In some embodiments, the thickness of the nonwoven fabric may be specifically 5 μm to 25 μm, for example, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, or a range consisting of any two thereof. This is advantageous for application to battery separators or electrolyte membranes, and also improves battery performance such as energy density and safety.

[0081] The surface density of the nonwoven fabric is 4 g / m 2 ~20g / m 2 , e.g., 4 g / m 2 , 7g / m 2 , 10g / m 2 , 13g / m 2 , 15g / m 2 , 18g / m 2 , 20g / m 2 Or it may be a range consisting of any two of them.

[0082] The density of the nonwoven fabric is 0.5 g / cm3 ~0.9g / cm 3 , e.g., 0.5 g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 Or it may be a range consisting of any two of them.

[0083] The nonwoven fabric can be produced by a conventional method in this field, and this method is not particularly limited. For example, raw materials for forming the nonwoven fabric (such as the main fiber or viscose fiber) are used to make nonwoven fabric base paper using conventional equipment in this field, such as a diagonal paper machine, and then the fiber base paper formed by a hot rolling mill is hot-rolled, for example, using a combination of a steel roller / soft roller or a steel roller / steel roller, and the hot-rolling temperature is, for example, 100°C to 300°C, and the nonwoven fabric is produced through the hot-rolling process.

[0084] The separator according to the embodiment of the present invention includes the nonwoven fabric, i.e., the separator is a nonwoven fabric separator. As described above, the nonwoven fabric can be used as a separator because it has both a thin thickness and high structural strength, and it can reduce the thickness of the separator while improving its performance such as strength, thereby improving the performance such as safety, cycle life, and energy density of electrochemical energy storage devices such as lithium ion batteries that use the separator.

[0085] Specifically, electrochemical devices such as lithium-ion batteries include a positive electrode plate and a negative electrode plate, and the separator is located between the positive electrode plate and the negative electrode plate to separate them. The separator can be used in liquid batteries, semi-solid batteries, or solid batteries. When used in semi-solid or solid batteries, the separator also serves as an electrolyte, i.e., functions as an electrolyte membrane instead of an electrolyte solution. Of course, semi-solid batteries generally require the injection of an electrolyte solution.

[0086] Generally, the separator may further include a component compounded with the nonwoven fabric, and the nonwoven fabric serves as the framework of the separator to support the component. The component may be specifically filled into the interior of the nonwoven fabric, for example, by penetrating into the fiber surfaces, gaps, pores, or uneven structures within the nonwoven fabric, and the component may also form a coating on the surface of the nonwoven fabric.

[0087] Fibers are the skeleton of nonwoven fabrics, and the morphology, arrangement, and other characteristics of the fibers in nonwoven fabrics determine the internal pore structure of the nonwoven fabric. The cross-sectional shape of modified cross-section fibers is irregular. By introducing modified cross-section fibers into nonwoven fabrics, the number, size, and other characteristics of the internal capillary pores of the nonwoven fabric can be adjusted. At the same time, the specific surface area and capillary phenomenon of the fibers and fiber network in the nonwoven fabric are significantly increased, which strengthens the absorption, transmission, and retention of components compounded with the nonwoven fabric and contributes to optimizing the performance of nonwoven fabric separators.

[0088] Specifically, when the separator is applied to a liquid battery, the component to be combined with the nonwoven fabric in the separator may include inorganic particles, polymers, or a combination thereof.

[0089] Specifically, when the separator is applied to a semi-solid battery or a solid battery, the component combined with the nonwoven fabric in the separator (electrolyte membrane) may be a solid electrolyte, which may specifically include one or more of a polymer electrolyte, an oxide electrolyte, a sulfide electrolyte, etc., but is not limited thereto.

[0090] Specifically, in practice, the components to be combined with the nonwoven fabric may be prepared into a slurry, which may then be applied to the nonwoven fabric and dried to form a coating.

[0091] When the separator is an electrolyte membrane (for example, an electrolyte membrane applied to a solid-state battery or a semi-solid-state battery), the perimeter coefficient X of the cross section is L is 1 <X LThe use of a nonwoven fabric containing modified cross-section fibers satisfying a ratio of ≦5 significantly increases the contact area between the nonwoven fabric and the solid electrolyte, enhancing the nonwoven fabric's ability to adsorb and coat the solid electrolyte, which is beneficial for the solid electrolyte to be more fully and efficiently packed into the nonwoven fabric, improving the packing density and loading of the solid electrolyte in the nonwoven fabric and alleviating interfacial contact issues with the solid electrolyte. At the same time, the anchoring effect provides a strong bond between the solid electrolyte and the nonwoven fabric, which is beneficial for reducing the solid / solid interfacial impedance between the solid electrolyte and the nonwoven fabric fibers. Therefore, the use of the electrolyte membrane of the present invention can improve the safety, cycle life, energy density, rate performance, and other performance of electrochemical energy storage devices such as lithium-ion batteries.

[0092] Specifically, when the above nonwoven fabric is used in the process of manufacturing the electrolyte membrane, the solid electrolyte slurry enters the internal pores of the nonwoven fabric through capillary action. If the irregular cross-section fibers in the nonwoven fabric have grooves 10, the solid electrolyte slurry also enters the fine grooves 10 on the surface of the irregular cross-section fibers. The strong wicking action and capillary action contribute to the solid electrolyte slurry spontaneously wetting and coagulating on the fiber surface and / or moving into the internal pores of the nonwoven fabric, thereby greatly increasing the contact area between the nonwoven fabric and the solid electrolyte, strengthening the nonwoven fabric's ability to adsorb and cover the solid electrolyte, and promoting the filling and densification of the solid electrolyte in the nonwoven fabric. This improves the density and loading, favoring more sufficient and efficient filling, and improves the interfacial contact problem of the solid electrolyte. At the same time, a strong bond between the solid electrolyte and the nonwoven fabric can be achieved through the anchoring effect. The solid electrolyte slurry penetrates into the internal structures of the nonwoven fabric, such as the fiber surface, gaps, pores, and unevenness, and generates an interlocking force at the contact surface after drying and curing, thereby achieving a high bonding strength between the solid electrolyte and the nonwoven fabric and favoring a reduction in the solid / solid interfacial impedance between the solid electrolyte and the nonwoven fabric fibers, thereby effectively improving the rate performance and other performances of the battery.

[0093] In addition, in the embodiment of the present invention, when the separator is applied to a liquid battery (where ions (such as lithium ions) are conducted by an electrolyte) or a semi-solid battery injected with an electrolyte, the high specific surface area of ​​the internal fibers of the nonwoven fabric can further improve the electrolyte absorption rate of the nonwoven fabric separator. In particular, when the irregular cross-section fibers have grooves 10 on the surface, the capillary force generated by the fine grooves 10 on the fiber surface allows the electrolyte to quickly infiltrate the surface and interior of the nonwoven fabric through wicking action, thereby improving the electrolyte absorption rate of the nonwoven fabric separator. This significantly improves the electrolyte retention rate and capacity, forms a stable electrolyte adsorption layer on the surface of the nonwoven fabric, reduces the resistance of the electrolyte to penetrate into the battery, and improves the interfacial properties of the separator. At the same time, by utilizing the properties of the pores due to the high specific surface area of ​​the nonwoven fabric and the capillary force of the fine grooves 10 in the fibers, the nonwoven fabric separator's ability to retain the electrolyte that enters the nonwoven fabric is improved, which is advantageous for realizing rapid transfer of ions (such as lithium ions). This effectively prevents phenomena such as leakage during use of the separator and the resulting problems of electrolyte depletion.

[0094] In the related art, a large amount of slurry is usually required to form a continuous coating layer, which results in defects such as an excessively thick nonwoven fabric separator. L is 1 <X L By using a nonwoven fabric containing modified cross-section fibers that satisfy a ratio of ≦5, the specific surface area of ​​the nonwoven fabric surface is significantly increased, strengthening its ability to adsorb and coat the slurry, allowing a continuous coating layer to be formed with a small amount of coating on the outer surface of the nonwoven fabric. Compared to conventional nonwoven fabric separators, in the embodiments of the present invention, the slurry is less likely to penetrate excessively into the nonwoven fabric, and the coating slurry is less likely to penetrate from one side (front) of the nonwoven fabric to the other side (back) of the nonwoven fabric. This significantly reduces the amount of slurry used and the thickness of the coating layer formed, thereby reducing the thickness of the separator. At the same time, the irregular cross-sections of the modified cross-section fibers in the nonwoven fabric strengthen the anchoring effect of the bond between the nonwoven fabric and the coating layer, achieving a strong bond between the coating layer and the nonwoven fabric, resulting in a nonwoven fabric separator with excellent performance.

[0095] In addition, the separator according to the embodiment of the present invention can also be applied to a solid-state battery manufactured using the technology roadmap of in-situ polymerization of polymer electrolyte. In the manufacturing process of the battery, an in-situ polymerization reaction (monomers for polymerizing a gel polymer electrolyte to form a gel polymer electrolyte are contained in the electrolyte solution) is carried out by using an injection process. In the embodiment of the present invention, the nonwoven fabric has a perimeter coefficient X L is 1 <X L By introducing modified cross-section fibers satisfying a ratio of ≦5, especially when the modified cross-section fibers have grooves 10 on their surfaces, the nonwoven fabric can absorb the electrolyte quickly and have a good flow-guiding effect, thereby promoting the uniform and rapid transmission and diffusion of the electrolyte in the battery system and the uniform dispersion of the electrolyte, and improving the efficiency of the in-situ polymerization reaction.

[0096] A battery according to an embodiment of the present invention comprises a positive plate, a negative plate and the separator described above, with the separator located between the positive plate and the negative plate.

[0097] As described above, the battery of the present invention may be a liquid battery, a semi-solid battery, or a solid battery, and these batteries may have a structure conventional in the art, but are not limited thereto. By employing the separator, performance such as safety, cycle life, and energy density of the battery can be improved.

[0098] The present invention will be further described below with specific examples. In the following examples, the shape of the cross section 1 of the modified cross-section fiber of Example 1 is shown in Figure 1, the shape of the cross section 1 of the modified cross-section fiber of Example 2 is shown in Figure 9, the shape of the cross section 1 of the modified cross-section fiber of Example 3 is shown in Figure 3, the shape of the cross section 1 of the modified cross-section fiber of Example 4 is shown in Figure 4, the shape of the cross section 1 of the modified cross-section fiber of Example 5 is shown in Figure 5, the shape of the cross section 1 of the modified cross-section fiber of Example 6 is shown in Figure 6, the shape of the cross section 1 of the modified cross-section fiber of Example 7 is shown in Figure 7, the shape of the cross section 1 of the modified cross-section fiber of Example 8 is shown in Figure 8, the shape of the cross section 1 of the modified cross-section fiber of Example 9 is shown in Figure 9, and the shape of the cross section 1 of the modified cross-section fiber of Example 10 is shown in Figure 1. The shape of the cross section 1 of the modified cross-section fiber of Example 11 is shown in Figure 11, the shape of the cross section 1 of the modified cross-section fiber of Example 12 is shown in Figure 12, the shape of the cross section 1 of the modified cross-section fiber of Example 13 is shown in Figure 13, the shape of the cross section 1 of the modified cross-section fiber of Example 14 is shown in Figure 14, the shape of the cross section 1 of the modified cross-section fiber of Example 15 is shown in Figure 15, the shape of the cross section 1 of the modified cross-section fiber of Example 16 is shown in Figure 16, the shape of the cross section 1 of the modified cross-section fiber of Example 17 is shown in Figure 17, the shape of the cross section 1 of the modified cross-section fiber of Example 18 is shown in Figure 18, and the shape of the cross section 1 of the modified cross-section fiber of Example 19 is shown in Figure 19.

[0099] In the following Examples and Comparative Examples, main fibers and viscose fibers were used, and nonwoven fabric base paper was made using a diagonal paper machine. The obtained base paper was then hot-pressed to compound the fibers, thereby producing a nonwoven fabric.

[0100] Tables 1 and 2 show the materials, softening points, linear densities, lengths, contents, and shapes of the cross sections 1 of the irregular cross-section fibers and the viscose fibers used in Examples 1 to 19 and Comparative Example 1, the circumferential coefficients of the cross sections 1 of the irregular cross-section fibers, the number of grooves 10 of the irregular cross-section fibers, the ratio of the width w of the widest point of the grooves 10 to the diameter D of the circumscribed circle 100 of the cross section 1 of the irregular cross-section fibers (w / D in Tables 1 and 2), the ratio of the depth h of the deepest point of the grooves 10 to the diameter D of the circumscribed circle 100 of the cross section 1 of the irregular cross-section fibers (h / D in Tables 1 and 2), the thickness of the nonwoven fabric, the areal density of the nonwoven fabric, the density of the nonwoven fabric, and the measured longitudinal tensile strength and transverse tensile strength of the nonwoven fabric.

[0101] The areal density of the nonwoven fabric was measured according to GB / T 451.2-2002, the thickness of the nonwoven fabric was measured according to GB / T 451.3-2002, the density of the nonwoven fabric was the ratio of the areal density of the nonwoven fabric to the thickness of the nonwoven fabric, the tensile strength (transverse tensile strength and longitudinal tensile strength) of the nonwoven fabric was measured according to GB / T 12914-2008, and the perimeter modulus of the cross section of the modified cross-section fiber was measured according to GB / T 50002-2013.

[0102] [Table 1-1] [Table 1-2]

[0103] The nonwoven fabrics of Examples 7 to 18 were produced by referring to the manufacturing process of the nonwoven fabric of Example 1. Examples 7 to 18 are distinguished from Example 1 by the different shapes of the modified cross-section fibers used, as specifically shown in Table 2. Other than the distinctions shown in Table 2, the other conditions were the same.

[0104] [Table 2]

[0105] Compared with Comparative Example 1 (which used two types of circular cross-section fibers but did not use modified cross-section fibers), Examples 1 to 19 had a circumferential coefficient X L is 1 <X L It can be seen that by introducing modified cross-section fibers that satisfy the condition of ≦5, the strength of the nonwoven fabric can be significantly improved, and at the same time, the thickness of the nonwoven fabric can be kept thin.

[0106] Compared to Example 19 (where the surface of the modified cross-section fiber has no grooves), the modified cross-section fiber in Example 6 has grooves, which can further improve the strength of the nonwoven fabric.

[0107] Compared to Example 18 (w / D<15%, h / D>75%), the modified cross-section fibers in Examples 1 and 7 to 17 satisfy w / D≧15% and h / D≦75%, further improving the strength of the nonwoven fabric.

[0108] Finally, it should be noted that the above embodiments are merely for illustrating the technical means of the present invention, and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art may still modify the technical means described in the above embodiments or substitute some or all of the technical features therein with equivalents, and these modifications or substitutions will not cause the essence of the corresponding technical means to depart from the scope of the technical means of the embodiments of the present invention. [Explanation of symbols]

[0109] 1: Cross section of irregular cross-section fiber 10: Groove 100: Circumscribed circle w: width of the widest part of the groove h: Depth of the deepest part of the groove

Claims

1. A nonwoven fabric comprising main fibers including circular cross-section fibers and modified cross-section fibers, wherein the circumferential coefficient of the cross section of at least some of the modified cross-section fibers is X Ｌ and 1<X Ｌ ≦5.

2. The nonwoven fabric according to claim 1 , wherein grooves are provided on the surface of the modified cross-section fibers.

3. The nonwoven fabric according to claim 2 , wherein the grooves extend along the axial direction of the modified cross-section fibers and penetrate the modified cross-section fibers in the axial direction of the modified cross-section fibers.

4. The nonwoven fabric according to claim 2 , wherein the number of the grooves is one or more, and when there are more than one, the grooves are distributed along the circumferential direction of the modified cross-section fiber.

5. 3. The nonwoven fabric according to claim 2, wherein the number of grooves is 16 or less.

6. a) the width of the widest point of the groove is 15% or more of the diameter of the circumscribed circle of the cross section of the modified cross section fiber; 3. The nonwoven fabric according to claim 2, wherein the nonwoven fabric satisfies at least one of the following conditions: a) the depth of the deepest point of the groove is 75% or less of the diameter of the circumscribed circle of the cross section of the modified cross section fiber; b) the depth of the deepest point of the groove is 75% or less of the diameter of the circumscribed circle of the cross section of the modified cross section fiber.

7. The cross-sectional shape of the modified cross-section fiber includes a heart shape, a dumbbell shape, a crescent shape, a new moon shape, a non-perfect ring shape, a non-perfect circle shape, a multi-lobed clover shape, a polygonal shape, a letter shape, or a plum blossom shape; Optionally, the non-perfect circular shape comprises a semi-circular or two-thirds circular shape; Optionally, the non-perfect circular shape comprises a seven-eighths circle, a three-quarters circle, or a two-thirds circle; Optionally, the multi-leaf cloverleaf comprises a three-leaf cloverleaf or a four-leaf cloverleaf; Optionally, the polygon comprises a poly-pointed star, the poly-pointed star comprising a three-pointed star, a four-pointed star, a five-pointed star, a six-pointed star, an eight-pointed star, a twelve-pointed star or a sixteen-pointed star; Optionally, the letter shape comprises a cross, a double cross, a U, a R, a C, an E, an F, a G, an H, a J, a K, an L, an M, an N, an S, a T, a U, a V, a W, an X, a Y, or a Z; 7. The nonwoven fabric according to claim 2, wherein the plum blossom shape optionally includes a four-petal plum blossom shape, a five-petal plum blossom shape, or a six-petal plum blossom shape.

8. a) the ratio of the mass of the modified cross-section fiber to the mass of the main fiber is 5% to 60%; The nonwoven fabric according to any one of claims 1 to 6, characterized in that it satisfies at least one of the following conditions: a) the ratio of the mass of the main fibers to the mass of the nonwoven fabric is 60% to 85%; b) the ratio of the mass of the main fibers to the mass of the nonwoven fabric is 60% to 85%.

9. a) the linear density of the main fiber is 0.4 dtex or less; 7. The nonwoven fabric according to claim 1, wherein the length of the main fibers is 1 mm to 3 mm.

10. The nonwoven fabric according to any one of claims 1 to 6, further comprising viscose fibers, wherein the softening point of the main fibers is higher than the softening point of the viscose fibers.

11. a. The difference between the softening point of the main fiber and the softening point of the viscose fiber is 20°C or more; 11. The nonwoven fabric according to claim 10, wherein at least one of the following conditions is satisfied: a) the viscose fibers have a softening point of 120°C or higher; and b) the viscose fibers have a softening point of 120°C or higher.

12. a) the linear density of the viscose fiber is 0.8 dtex or less; 11. The nonwoven fabric according to claim 10, wherein the nonwoven fabric satisfies at least one of the following conditions: a) the length of the viscose fibers is between 1 mm and 3 mm;

13. The viscose fiber includes one or more of unstretched polyester fiber, polyvinylidene fluoride fiber, polyamide fiber, copolyamide fiber, polyolefin fiber, copolyester fiber, and copolyamide fiber; Optionally, the unstretched polyester fibers comprise at least one of polyethylene terephthalate fibers or polybutylene terephthalate fibers; Optionally, the polyolefin fibers include one or more of polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, polystyrene fibers, polyethylene / polypropylene sheath-core fibers, polyethylene / polyethylene terephthalate sheath-core fibers, and polyethylene / polybutylene terephthalate sheath-core fibers; Optionally, the copolyester fiber comprises at least one of CoPET or CoPBT; Optionally, the copolyamide fibers comprise one or more of PA6 / 6, PA6 / 66, PA6 / 66 / 12, PA6 / 66 / 69, PA6 / 66 / 610, PA6 / 66 / 612, PA6 / 66 / 1010, PA6 / 612 / 12, PA6 / 610 / 12, PA6 / 66 / 69 / 12, and PA6 / 66 / 11 / 12.

14. At least one of the circular cross-section fiber and the modified cross-section fiber comprises one or more of polyester fiber, polyolefin fiber, polyamide fiber, polyimide fiber, polytetrafluoroethylene fiber, polyphenylene sulfide fiber, polyether ether ketone fiber, polyacrylonitrile fiber, polycarbonate fiber, and aramid fiber; Optionally, the polyester fiber comprises one or more of polyethylene terephthalate fiber, polybutylene terephthalate fiber, polytrimethylene terephthalate fiber, and polyisophthalate resin fiber; Optionally, the polyolefin fibers include one or more of polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, and polystyrene fibers; Optionally, the nonwoven fabric according to any one of claims 1 to 6, characterized in that the polyamide fibers comprise PA66.

15. a) the thickness of the nonwoven fabric is 5 μm to 25 μm; b. The surface density of the nonwoven fabric is 4 g / m ２ ~20g / m ２ the condition that c, the density of the nonwoven fabric is 0.5 g / cm ３ ~0.9 g / cm ３ The nonwoven fabric according to any one of claims 1 to 6, characterized in that it satisfies at least one of the following conditions:

16. A separator comprising the nonwoven fabric according to any one of claims 1 to 15.

17. 17. A battery comprising a positive plate, a negative plate, and the separator of claim 16, said separator being located between said positive plate and said negative plate.

18. 18. The battery of claim 17, wherein the battery is a liquid battery, a semi-solid battery, or a solid battery.

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