CN113725556A - Nonwoven fabric and battery separator - Google Patents

Nonwoven fabric and battery separator Download PDF

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Publication number
CN113725556A
CN113725556A CN202111026506.6A CN202111026506A CN113725556A CN 113725556 A CN113725556 A CN 113725556A CN 202111026506 A CN202111026506 A CN 202111026506A CN 113725556 A CN113725556 A CN 113725556A
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CN
China
Prior art keywords
fibers
nonwoven fabric
mass fraction
fiber
fibrillated
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Granted
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CN202111026506.6A
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Chinese (zh)
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CN113725556B (en
Inventor
陈莉
王艳杰
林陆菁
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Shenzhen Senior Technology Material Co Ltd
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Shenzhen Senior Technology Material Co Ltd
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Priority to CN202111026506.6A priority Critical patent/CN113725556B/en
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/425—Cellulose series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4282—Addition polymers
    • D04H1/4291—Olefin series
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4326—Condensation or reaction polymers
    • D04H1/4334—Polyamides
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4326—Condensation or reaction polymers
    • D04H1/4334—Polyamides
    • D04H1/4342—Aromatic polyamides
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • D04H1/4391—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece characterised by the shape of the fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Cell Separators (AREA)

Abstract

A non-woven fabric and a battery diaphragm belong to the technical field of non-woven fabrics. The non-woven fabric comprises at least two fiber layers, the fibers in the fiber layers comprise first fibers and second fibers, the melting point or softening point of the second fibers is smaller than that of the first fibers, the fiber layers on the surface of the non-woven fabric further comprise fibrillated fibers, and the melting point or softening point of the second fibers is smaller than that of the fibrillated fibers. The non-woven fabric has good liquid absorption rate and electrolyte holding rate.

Description

Nonwoven fabric and battery separator
Technical Field
The application relates to the technical field of non-woven fabrics, particularly, relate to a non-woven fabrics and battery diaphragm.
Background
In recent years, the demand of battery separators is rapidly increased due to the explosive development of the new energy automobile market. The non-woven fabric separator has good heat resistance temperature, so that the non-woven fabric separator has great potential in the application aspect of batteries, but the tensile mechanical strength of the non-woven fabric is generally poorer than that of the polyolefin porous membrane, and the thickness of the non-woven fabric must be increased in order to increase the strength of the non-woven fabric. Meanwhile, the non-woven fabric has a natural large aperture, the electrochemical safety is poor, if the aperture is reduced to prevent micro short circuit, the holding rate of the membrane to the electrolyte is obviously reduced, and the high-efficiency migration of ions in the non-woven fabric is difficult to maintain, so that the non-woven fabric membrane is difficult to fully meet the application requirement of the lithium ion battery membrane at present, and how to obtain the thin non-woven fabric membrane with high liquid absorption rate and high holding rate is a problem to be solved urgently by relevant researchers at present.
Disclosure of Invention
The application provides a non-woven fabrics and battery diaphragm, this non-woven fabrics have better imbibition rate and electrolyte hold rate simultaneously.
The embodiment of the application is realized as follows:
in a first aspect, embodiments of the present application provide a nonwoven fabric, the nonwoven fabric including at least two fiber layers, fibers in the fiber layers including first fibers and second fibers, and melting point or softening point of the second fibers being smaller than melting point or softening point of the first fibers;
one fiber layer on the surface of the non-woven fabric also comprises fibrillated fibers, and the melting point or softening point of the second fibers is smaller than that of the fibrillated fibers.
In a second aspect, embodiments of the present application provide a battery separator including the nonwoven fabric of the first aspect.
The non-woven fabric and the battery diaphragm of the embodiment of the application at least comprise the following beneficial effects:
in the non-woven fabrics of this application, the melting point or the softening point of second fibre is less than the melting point or the softening point of first fibre and fibrillated fiber, and when making the fibrous layer, first fibre and fibrillated fiber can the original state after second fibre melts or softens, and the second fibre can be in order to improve the intensity of whole non-woven fabrics with first fibre and fibrillated fiber closely together.
The fibrillated fiber contains numerous fibrils and microfibrils with small diameters, the fibrillated fiber can be mutually staggered with the first fiber and the second fiber in the papermaking forming process to form a tight fiber network, the establishment of a rich and uniform pore structure is facilitated, the strength of a fiber layer is improved, the porosity and pore distribution of the fiber layer are controlled, the effective specific surface area of the fiber layer can be remarkably increased, the fiber layer and electrolyte can have good wettability, fine and rich pores formed by the fibrillated fiber have strong capillary force, and the strong liquid absorption capacity and liquid retention capacity of the non-woven fabric to the electrolyte are ensured. In addition, the cellulose fibrillated fiber has abundant hydroxyl structures, and is favorable for further improving the electrolyte absorption rate and holding rate of the non-woven fabric.
The effect of the fibrillated fiber on the peeling strength of the coating is mainly shown in the mechanical combination of the coating sizing agent and the surface of the non-woven fabric base material, the fibrillated fiber with abundant microfiber structure can effectively increase the surface roughness and the specific surface area of the non-woven fabric, increase the specific surface area, increase the van der Waals attraction of the coating sizing agent molecules and the base material surface groups, and improve the coating adhesive force; the three-dimensional texture formed on the rough surface provides more anchoring points for the coating, so that the mechanical engagement between the coating slurry and the base material is firmer, the adhesion of the coating is enhanced, and the conditions of falling and peeling are not easy to occur.
Detailed Description
The embodiments of the present application will now be described in detail with reference to the examples, wherein all of the features disclosed in this specification, or all of the steps of any method or process so disclosed, may be combined in any combination, except for the mutually exclusive features and/or steps.
The following will specifically describe the nonwoven fabric and the battery separator according to the embodiment of the present application:
in a first aspect, embodiments of the present application provide a nonwoven fabric, the nonwoven fabric including at least two fiber layers, fibers in the fiber layers including first fibers and second fibers, and a melting point or a softening point of the second fibers being smaller than a melting point or a softening point of the first fibers.
One fiber layer on the surface of the non-woven fabric also comprises fibrillated fibers, and the melting point or softening point of the second fibers is smaller than that of the fibrillated fibers.
That is, the melting point of the fibrillated fibers and the first fibers may be higher than the melting point of the second fibers, the melting point of the fibrillated fibers and the first fibers may be higher than the softening point of the second fibers, the softening point of the fibrillated fibers and the first fibers may be higher than the melting point of the second fibers, or the softening point of the fibrillated fibers and the first fibers may be higher than the softening point of the second fibers.
In the non-woven fabrics of this application embodiment, the melting point or the softening point of second fibre is less than the melting point or the softening point of first fibre and fibrillated fiber, and first fibre and fibrillated fiber can the original state after second fibre melts or softens, and the second fibre can be closely combined first fibre and fibrillated fiber together in order to improve the intensity of whole non-woven fabrics.
The fibrillation of the fiber means a process in which, when wet friction occurs in the fiber in a wet state, the fiber is peeled off along the fiber main body to form fibrils having a smaller diameter and further to form finer microfibrils. The fibrillated fiber contains numerous fibrils and microfibrils with small diameters, so that the fibrillated fiber can be mutually staggered with the first fiber and the second fiber in the papermaking forming process to form a tighter fiber network, the establishment of a rich and uniform pore structure is facilitated, the strength of a fiber layer is improved, the porosity and pore distribution of the fiber layer are controlled, the effective specific surface area of the fiber layer can be remarkably increased by the fibrillated fiber, the fiber layer and electrolyte can have good wettability, fine and rich pores formed by the fibrillated fiber have strong capillary force, and the strong liquid absorption capacity and liquid retention capacity of the non-woven fabric to the electrolyte are ensured.
The effect of the fibrillated fiber on the peeling strength of the coating is mainly shown in the mechanical combination of the coating sizing agent and the surface of the non-woven fabric base material, the fibrillated fiber with abundant microfiber structure can effectively increase the surface roughness and the specific surface area of the non-woven fabric, increase the specific surface area, increase the van der Waals attraction of the coating sizing agent molecules and the base material surface groups, and improve the coating adhesive force; the three-dimensional texture formed on the rough surface provides more anchoring points for the coating, so that the mechanical engagement between the coating slurry and the base material is firmer, the adhesion of the coating is enhanced, and the conditions of falling and peeling are not easy to occur.
Optionally, the fibrillated fibers have a diameter of less than 1.0 μm, such as 0.1 μm, 0.2 μm, 0.5 μm, 0.7 μm, or 0.9 μm.
Illustratively, the fibrillated fibers include at least one of cellulosic fibers, bacterial cellulose, aramid fibers, polyolefin fibers, and poly-paraphenylene terephthalamide.
The cellulose fibrillated fiber has abundant hydroxyl structures, and is favorable for further improving the liquid absorption rate and the holding rate of the electrolyte of the non-woven fabric.
Optionally, the cellulosic fibers comprise at least one of viscose, modal and lyocell fibers.
Optionally, the polyolefin fibers comprise at least one of polyethylene fibers and polypropylene fibers.
In some possible embodiments, the mass percent of the second fibers in each fiber layer is 20 to 40 wt%, and the mass percent of the fibrillated fibers in the fiber layer containing fibrillated fibers is no greater than 20 wt%.
The content of the first fibers can be ensured by arranging the fibers according to the proportion range, so that the non-woven fabric can have higher strength. Optionally, the mass percent of the second fibers in each fibrous layer is 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%. Optionally, the mass percent of fibrillated fibers is 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, or 18 wt%.
Optionally, the first fibers comprise at least one of unstretched polyethylene terephthalate fibers, polyvinyl alcohol fibers, unstretched polybutylene terephthalate fibers, polyvinylidene fluoride (PVDF) fibers, polyvinyl chloride (PVC) fibers, Polyethylene (PE) fibers, polypropylene (PP) fibers, Polyamide (PA) fibers, Polyetheretherketone (PEEK) fibers, Polytetrafluoroethylene (PTFE) fibers, polycarbonate fibers, Polyphenylene Sulfide (PPs) fibers, ES fibers, aramid fibers, Polyacrylonitrile (PAN) fibers, boride fibers, acrylonitrile fibers, glass fibers, ceramic fibers, Polyimide (PI) fibers, oxide fibers, and nitride fibers.
Optionally, the bonding fibers comprise at least one of polyethylene terephthalate fibers (PET), alkali soluble polyester (COPET), copolyamides, polyolefin fibers, polybutylene terephthalate (PBT) fibers, and copolyester fibers. Optionally, the polyamide fiber comprises PA 66.
The first fibers of each fiber layer may be fibers of the same material, or fibers of different materials. The second fibers of each fiber layer may be the same material or different materials, so long as the melting point or softening point of the second fibers is lower than the melting point or softening point of the first fibers and the fibrillated fibers.
Further, the inventor of the present application found in research that the stretch-resistant mechanical strength of the nonwoven fabric is generally poor, and it is difficult to sufficiently meet the requirements of the high-speed winding process of the assembled battery, and in order to increase the strength of the nonwoven fabric, the thickness of the nonwoven fabric is generally increased in the conventional method, but this method results in a thicker nonwoven fabric serving as a support layer of the separator, and the thickness of the coated battery separator is further increased, and the battery separator with a large thickness correspondingly causes a large loss to the energy density of the battery. And the aperture of the existing non-woven fabric is generally larger, which is beneficial to obtaining high ion migration rate, but the risk of generating pore defects on a coating layer of the battery diaphragm is increased.
In some embodiments of the present application, the first fibers and the second fibers each have coarse fibers and fine fibers, wherein the fine fibers in the first fibers have a diameter <3 μm and the coarse fibers in the first fibers have a diameter of 3 to 13 μm; the diameter of the fine fibers in the second fibers is less than 4 micrometers, and the diameter of the coarse fibers in the second fibers is 4-15 micrometers; along the thickness direction of the fiber layers, the ratio gradient of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is increased, the surface of the fiber layer with the minimum ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is a coating surface, and the surface of the fiber layer with the maximum ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is a non-coating surface.
The mass fraction of the coarse fiber is equal to the mass of the coarse fiber/(mass of the coarse fiber + mass of the fine fiber), and the mass fraction of the fine fiber is equal to the mass of the fine fiber/(mass of the coarse fiber + mass of the fine fiber).
Illustratively, the diameter of the fine fibers in the first fibers is 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 2.9 μm.
Illustratively, the diameter of the coarse fibers in the first fibers is 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or 13 μm.
Illustratively, the fine fibers in the second fibers have a diameter of 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or 3.9 μm.
Illustratively, the diameter of the coarse fibers in the second fibers is 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.
In the embodiment of the application, along the thickness direction of fibrous layer, the fibrous layer that the mass fraction of thick fibre and the mass fraction of thin fibre's ratio is less can cover and fill the pore part that the fibrous layer that the mass fraction of thick fibre and the mass fraction of thick thin fibre's ratio is great formed, the pore diameter that forms along the thickness direction pore of fibrous layer is gradient change's structure, and each fibrous layer can form more smooth transition, increase along with the ratio gradient of the mass fraction of thick fibre and the mass fraction of thin fibre, the pore diameter gradient of fibrous layer increases, intensity progressively increases in proper order. The pore diameter of the pores changes in a gradient manner, so that the permeation resistance of the electrolyte is reduced, the transmission rate of lithium ions in the non-woven fabric is improved, the concentration polarization phenomenon of the lithium ions on the surface of the electrode is greatly reduced, the capacity attenuation caused by untimely lithium ion insertion-extraction in the circulation process of the battery can be effectively reduced, and the capacity of the battery is maintained particularly under the condition of high-rate charge and discharge.
When the surface of the fiber layer with the minimum ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is used for coating a coating, the pore diameter formed by the fiber layer is small, the specific surface of pores is large, the contact area of the coating liquid and the fiber layer can be increased when the coating liquid is coated, a continuous coating can be formed by coating a small amount, the coating liquid is not easy to permeate to the other side of the non-woven fabric from the layer, and the probability of pore defects caused by liquid leakage of the coating layer can be reduced. Meanwhile, the pore diameter of the fiber layer is small, so that the growth of lithium dendrites and the self-discharge phenomenon of the battery can be effectively inhibited, and the safety performance of the battery is improved. In addition, the small-aperture pore capillary effect ensures the liquid absorption rate and the liquid retention capacity of the diaphragm on the electrolyte, is favorable for the electrolyte to form a stable adsorption layer on the surface of the coating, and is favorable for the rapid transmission of lithium ions. The non-coating side has larger pore volume, so that the diaphragm fixes a large amount of electrolyte, and the high electrolyte holding rate promotes the high-efficiency transmission of lithium ions in the pore channel. The battery diaphragm is high in liquid absorption rate and liquid holding rate of electrolyte, the cycle performance of the battery is improved, and the phenomenon that the electrolyte is exhausted due to reasons such as leakage and the like in the use process of the battery diaphragm can be effectively prevented.
Wherein, increase along with the ratio gradient of the mass fraction of thick fibre and the mass fraction of thin fibre, intensity increases gradually in proper order, and the one deck fibrous layer that the mass fraction of thick fibre and the mass fraction of thin fibre are the biggest is mainly used as the support, and the intensity of this layer fibrous layer is great, then need not also can guarantee the intensity of non-woven fabrics through the thickness that increases the non-woven fabrics to can be used for the battery diaphragm to play the supporting role. In addition, the pore diameter of the layer of fiber layer with the largest ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is larger, so that air entrained between the coating layer and the non-woven fabric can be enabled to rapidly escape through large pores of the layer of fiber layer, air residues are prevented from entering the coating layer to form bubbles, and the generation of pore defects can be reduced.
Optionally, the nonwoven fabric has a thickness of 5 to 35 μm, for example 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or 35 μm.
Optionally, the fine fibers have a length of 1 to 6mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, or 6 mm. Optionally, the coarse fibers have a length of 1 to 10mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10 mm.
In some embodiments, the mass percentage of fine fibers is greater than 50 wt% in the fiber layer having the smallest ratio of the mass fraction of coarse fibers to the mass fraction of fine fibers, and the mass percentage of coarse fibers is greater than 50 wt% in the fiber layer having the largest ratio of the mass fraction of coarse fibers to the mass fraction of fine fibers. The research of the inventor of the application finds that when the coarse fibers and the fine fibers are arranged in the mode, the probability of generating hole defects due to liquid leakage of the coating layer can be further reduced.
Illustratively, the mass percentage of the coarse fibers in the fiber layer in which the ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is largest is 52 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%.
Illustratively, the mass percentage of fine fibers in the fiber layer having the smallest ratio of the mass fraction of coarse fibers to the mass fraction of fine fibers is 52 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%.
In some embodiments, the mass percentage of coarse fibers in the first fibers of the fibrous layer is the same as the mass percentage of coarse fibers in the second fibers. In other embodiments, it is also possible that the mass percentage of coarse fibers in the first fibers of the fiber layer is different from the mass percentage of coarse fibers in the second fibers.
In some embodiments, the nonwoven fabric has an average pore size of 5 μm or less and a ratio of the maximum pore size to the average pore size of 1 to 10.
In the research of the present inventors, it was found that when the average pore diameter of the nonwoven fabric is greater than 5 μm, the coating liquid is easily permeated from one side to the other side when the nonwoven fabric is coated, and when the ratio of the maximum pore diameter to the average pore diameter of the nonwoven fabric is greater than 10, the uniformity of the cured film formation of the coating layer is affected. The average pore diameter of the non-woven fabric is less than or equal to 5 microns, the phenomenon that the coating liquid permeates to the other side to cause leakage can be avoided, and the ratio of the maximum pore diameter to the average pore diameter of the non-woven fabric is 1-10, so that the non-woven fabric has relatively uniform pore diameter distribution, and the uniformity of coating film forming is improved.
Illustratively, the mean pore size of the nonwoven fabric is 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm.
Illustratively, the ratio of the maximum pore size to the average pore size of the nonwoven fabric is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.
In some embodiments, the nonwoven fabric has an areal density of 5 to 25g/m2For example, 5g/m2、10g/m2、15g/m2、20g/m2And 25g/m2Or any range therebetween.
The inventors of the present application have found that when the areal density of the nonwoven fabric is less than 5g/m2In this case, the battery separator cannot withstand high tension, and is likely to break, and the coating liquid is likely to permeate to the other side when the nonwoven fabric is coated. If the areal density is more than 25g/m2In the case of the same density, the thickness may become thicker, which may decrease the capacity of the battery pack.
In some embodiments, the nonwoven fabric has a density of 0.50 to 0.90g/m3For example, 0.5g/m3、0.6g/m3、0.7g/m3、0.8g/m3And 0.90g/m3Or any range therebetween.
The inventors of the present application have found that when the density is less than 0.50g/m3When the coating solution is applied to the nonwoven fabric, the coating solution is easily penetrated into the other side of the nonwoven fabric, and when the density is more than 0.90g/m3In the process, the coating liquid is easy to penetrate deeply into the surface of the non-woven fabric, the formed coating has insufficient binding force to the non-woven fabric, and the transmission of lithium ions in the charging and discharging process of the battery is also hindered due to overhigh density.
In some embodiments, the nonwoven fabric has a transverse direction tensile strength >0.2kN/m and a machine direction tensile strength/transverse direction tensile strength ratio of 1.05 to 4.
The transverse tensile strength of the non-woven fabric is enough, the non-woven fabric is not easy to break or tear when being coated, and the longitudinal tensile strength/transverse tensile strength ratio of the non-woven fabric can reduce the probability of longitudinal wrinkles generated by the non-woven fabric.
In a second aspect, embodiments of the present application provide a battery separator including the nonwoven fabric of the first aspect.
The battery diaphragm of this application embodiment includes above-mentioned non-woven fabrics, and this non-woven fabrics has higher intensity, and it has higher electrolyte retention rate, is favorable to improving the electrical property of electric core.
The nonwoven fabric and the battery separator of the present application will be described in further detail with reference to examples.
Example 1
This embodiment provides a non-woven fabrics, this non-woven fabrics includes two-layer fibrous layer, specifically sets up as follows:
Figure BDA0003243715370000101
the preparation method of the non-woven fabric comprises the following steps: and (3) making a fiber layer by using an inclined wire paper machine, and performing hot rolling treatment on the multiple fiber layers to obtain the non-woven fabric. Wherein, the hot press of the hot pressing treatment adopts a combination of a steel roller and a soft roller. Wherein, the first fiber adopts unstretched PET, and the bonding fiber adopts conventional PET.
Example 2
The embodiment provides a non-woven fabric, the preparation method of which is the same as that of embodiment 1, the non-woven fabric comprises three fiber layers, and the specific settings are as follows:
Figure BDA0003243715370000102
Figure BDA0003243715370000111
example 3
The embodiment provides a non-woven fabric, the preparation method of which is the same as that of embodiment 1, the non-woven fabric comprises three fiber layers, and the specific settings are as follows:
Figure BDA0003243715370000112
example 4
The embodiment provides a non-woven fabric, the preparation method of which is the same as that of embodiment 1, the non-woven fabric comprises three fiber layers, and the specific settings are as follows:
Figure BDA0003243715370000113
Figure BDA0003243715370000121
example 5
The embodiment provides a non-woven fabric, the preparation method of which is the same as that of embodiment 1, the non-woven fabric comprises two fiber layers, and the specific settings are as follows:
Figure BDA0003243715370000122
example 6
This embodiment provides a non-woven fabrics, this non-woven fabrics includes two-layer fibrous layer, and two-layer fibrous layer sets up the same, specifically sets up as follows:
Figure BDA0003243715370000123
Figure BDA0003243715370000131
example 7
The embodiment provides a non-woven fabric, which includes two fiber layers, and the preparation method is the same as that of embodiment 1, and specifically includes the following steps:
Figure BDA0003243715370000132
example 8
The embodiment provides a non-woven fabric, the preparation method of which is the same as that of embodiment 1, the non-woven fabric comprises four fiber layers, and the specific settings are as follows:
Figure BDA0003243715370000133
Figure BDA0003243715370000141
wherein, the first fiber adopts unstretched PET, and the bonding fiber adopts conventional PET.
Comparative example 1
This comparative example provides a non-woven fabric, it includes two-layer fibrous layer, specifically sets up as follows:
Figure BDA0003243715370000142
wherein, the first fiber adopts unstretched PET, and the bonding fiber adopts conventional PET.
Comparative example 2
This comparative example provides a nonwoven fabric, the preparation method of which is the same as in example 1, the nonwoven fabric comprising two fibrous layers, specifically arranged as follows:
Figure BDA0003243715370000151
comparative example 3
This comparative example provides a nonwoven fabric, the preparation method of which is the same as in example 1, the nonwoven fabric comprising two fibrous layers, specifically arranged as follows:
Figure BDA0003243715370000152
comparative example 4
This comparative example provides a nonwoven fabric, the preparation method of which is the same as in example 1, the nonwoven fabric comprising two fibrous layers, specifically arranged as follows:
Figure BDA0003243715370000153
Figure BDA0003243715370000161
test example 1
The nonwoven fabrics of examples 1 to 8 and comparative examples 1 to 8 were cut into samples of the same size, and then the surface density, thickness, pore size and strength of the sample nonwoven fabrics were measured, wherein the density is the surface density/thickness, and the results of the measurement are reported in table 1.
The nonwoven fabrics of examples 1 to 8 and comparative examples 1 to 4 were cut into samples having the same size, the coating liquid was applied to the first layer surface of the sample, the sample was dried after the application, the coating layer was formed on the first layer surface of the nonwoven fabric, the number of pin holes of the coating layer, the penetration of the coating liquid, and the thickness of the coating layer were measured, and the results are shown in table 2.
Wherein the surface density is determined by the method of GB/T451.2-2002; the thickness is measured according to the method GB/T451.3-2002; the pore diameter is determined by referring to the method GB/T32361-2015; the intensity is determined by reference to the GB/T12914-2008 method.
The "peel strength" of the coating layer was measured according to GB/T2792-2014, and the results are shown in Table 2. The term "fiber entanglement" refers to the fact that undispersed fiber bundles or dispersed fibers are re-entangled and agglomerated together and reinforced, and is different from the superposition phenomenon of other parts, and when the measurement is performed, the superposition condition is observed through human eyes, and the number of the superposed parts of the fibers in each square meter of the non-woven fabric is used as the detection result of the fiber entanglement.
Electrolyte in diaphragm sampleClimbing height test on article: cutting a sample to be tested into a rectangular sample strip of 20cm multiplied by 1cm, fixing one end of the sample strip to be tested on a clamp vertical to a test bed, and vertically immersing the sample into electrolyte solution (1M LiPF) in a culture dish6EC: DEC ═ 1:1v/v), the climbing height of the electrolyte on the separator bar was measured after 1h of standing. A higher height indicates a faster absorption rate of the electrolyte by the sample. Wherein the results are reported in Table 2
Electrolyte ratio measurement: weighing the mass W of the sample to be measured without soaking in electrolyte1Soaking the sample in electrolyte for 1h, wiping off the redundant electrolyte on the surface of the film, weighing and recording as W2And calculating the electrolyte ratio by the formula (1):
electrolyte ratio (W)2-W1)/W1X 100% (1). The results are reported in table 2.
TABLE 1 test results of nonwoven fabric samples
Figure BDA0003243715370000171
TABLE 2 test results of coating layer and composite nonwoven fabric
Figure BDA0003243715370000172
Figure BDA0003243715370000181
Comparing example 1 and comparative example 1, it is found that example 1 adds fibrillated fibers in the first layer compared to comparative example 1, and in combination with the experimental results, it can be found that both the electrolyte retention rate and the electrolyte climbing height of example 1 are greater than those of comparative example 1.
Comparing example 5 with comparative example 2, it is found that example 5 adds fibrillated fibers in the first layer compared to comparative example 2, and in combination with the experimental results, it can be found that both the electrolyte retention rate and the electrolyte climbing height of example 5 are greater than those of comparative example 2.
Comparing example 6 with comparative example 3, it was found that example 6 adds fibrillated fibers in the first layer compared to comparative example 3, and in combination with the experimental results, it can be found that both electrolyte retention and electrolyte climbing height of example 6 are greater than that of comparative example 3.
Comparing example 7 with comparative example 4, it is found that example 7 adds fibrillated fibers in the first layer compared to comparative example 4, and in combination with the experimental results, it can be found that both the electrolyte retention rate and the electrolyte climbing height of example 7 are greater than those of comparative example 4.
The combination of the above results shows that the addition of the fibrillated fibers to the fiber layer can provide a composite nonwoven fabric having both good liquid absorption rate and electrolyte holding rate.
Comparing the nonwoven fabrics of the embodiment 2 and the embodiment 4, the first layer of the nonwoven fabric of the embodiment 2 contains 20 wt% of the fibrillated fiber, and the first layer of the nonwoven fabric of the embodiment 4 contains 30 wt% of the fibrillated fiber, and the experimental result shows that the electrolyte retention rate and the electrolyte climbing height of the nonwoven fabric of the embodiment 2 are both larger than those of the embodiment 4, which shows that the mass percentage of the fibrillated fiber in the fiber layer containing the fibrillated fiber is not more than 20 wt%, which is more beneficial to simultaneously improving the liquid absorption rate and the electrolyte holding rate of the composite nonwoven fabric.
The mass fractions of the fine fibers in the first fiber layer and the second fiber layer of the nonwoven fabric of example 7 are less than 50 wt%, and the results of the experiments show that the average pore diameter of the nonwoven fabric of example 7 is large, pinholes are generated in the coating, and the coating liquid penetrates into the back surface of the nonwoven fabric to form a thick coating. It is demonstrated that even if the ratio gradient of the mass fraction of the coarse fibers to the mass fraction of the fine fibers increases in the thickness direction of the fiber layers, if the mass fraction of the fine fibers is less than 50 wt% in one of the fiber layers in which the ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is the smallest, the coating layer is liable to cause a pore defect.
The present application is not limited to the foregoing embodiments. The application extends to any novel feature or any novel combination of features disclosed in this specification and to any novel method or process steps or any novel combination of features disclosed.

Claims (10)

1. A nonwoven fabric comprising at least two fibrous layers, the fibers in the fibrous layers comprising first fibers and second fibers, the second fibers having a melting or softening point less than the melting or softening point of the first fibers;
the non-woven fabric further comprises fibrillated fibers in one fiber layer on the surface of the non-woven fabric, and the melting point or softening point of the second fibers is smaller than that of the fibrillated fibers.
2. The nonwoven fabric according to claim 1, wherein the mass percentage of the second fibers in each of the fiber layers is 20 to 40 wt%, and the mass percentage of the fibrillated fibers in the fiber layer containing the fibrillated fibers is not more than 20 wt%.
3. The nonwoven fabric of claim 1 wherein the fibrillated fibers have a diameter of less than 1.0 μm.
4. The nonwoven fabric of claim 1, wherein the fibrillated fibers include at least one of cellulosic fibers, bacterial cellulose, aramid fibers, polyolefin fibers, and poly-paraphenylene terephthalamide.
5. The nonwoven fabric according to any one of claims 1 to 4, wherein the first fibers and the second fibers each have coarse fibers and fine fibers, and a ratio of a mass fraction of the coarse fibers to a mass fraction of the fine fibers increases in a gradient in a thickness direction of the fiber layer; the surface of the fiber layer with the smallest ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is a coating surface, and the surface of the fiber layer with the largest ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is a non-coating surface;
wherein the diameter of the fine fibers in the first fibers is less than 3 μm, and the diameter of the coarse fibers in the first fibers is 3-13 μm; the diameter of the fine fibers in the second fibers is less than 4 micrometers, and the diameter of the coarse fibers in the second fibers is 4-15 micrometers;
the fibrillated fibers are contained in the fiber layer in which the ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is smallest.
6. The nonwoven fabric according to claim 5, wherein in the fiber layer in which the ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers is smallest, the mass percentage of the fine fibers is more than 50 wt%; and in the fiber layer with the largest ratio of the mass fraction of the coarse fibers to the mass fraction of the fine fibers, the mass percentage of the coarse fibers is more than 50 wt%.
7. The nonwoven fabric according to any of claims 1 to 4, wherein the nonwoven fabric has an average pore size of 5 μm or less, and the ratio of the maximum pore size to the average pore size of the nonwoven fabric is 1 to 10.
8. The nonwoven fabric of any of claims 1 to 4, wherein the nonwoven fabric has an areal density of 5 to 25g/m2；
Optionally, the density of the non-woven fabric is 0.50-0.90 g/m3。
9. The nonwoven fabric of any of claims 1 to 4, wherein the nonwoven fabric has a transverse tensile strength >0.2kN/m and a machine direction tensile strength/transverse direction tensile strength ratio of 1.05 to 4.
10. A battery separator comprising the nonwoven fabric according to any one of claims 1 to 9.
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