CN113725557B - Lithium ion battery diaphragm supporting layer and lithium ion battery diaphragm - Google Patents
Lithium ion battery diaphragm supporting layer and lithium ion battery diaphragm Download PDFInfo
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- CN113725557B CN113725557B CN202111027789.6A CN202111027789A CN113725557B CN 113725557 B CN113725557 B CN 113725557B CN 202111027789 A CN202111027789 A CN 202111027789A CN 113725557 B CN113725557 B CN 113725557B
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 57
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 57
- 230000008093 supporting effect Effects 0.000 title abstract description 6
- 239000000835 fiber Substances 0.000 claims abstract description 367
- 239000004745 nonwoven fabric Substances 0.000 claims abstract description 125
- 239000011148 porous material Substances 0.000 claims abstract description 42
- 239000012784 inorganic fiber Substances 0.000 claims abstract description 25
- -1 polyethylene terephthalate Polymers 0.000 claims description 36
- 238000002844 melting Methods 0.000 claims description 25
- 230000008018 melting Effects 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 25
- 229920000098 polyolefin Polymers 0.000 claims description 10
- 239000003365 glass fiber Substances 0.000 claims description 9
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 8
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 8
- YKTSYUJCYHOUJP-UHFFFAOYSA-N [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] Chemical compound [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] YKTSYUJCYHOUJP-UHFFFAOYSA-N 0.000 claims description 7
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 6
- 229920001707 polybutylene terephthalate Polymers 0.000 claims description 6
- 239000004952 Polyamide Substances 0.000 claims description 5
- 239000004698 Polyethylene Substances 0.000 claims description 5
- 239000004743 Polypropylene Substances 0.000 claims description 5
- 229920002647 polyamide Polymers 0.000 claims description 5
- 229920000573 polyethylene Polymers 0.000 claims description 5
- 229920001155 polypropylene Polymers 0.000 claims description 5
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 5
- 239000004800 polyvinyl chloride Substances 0.000 claims description 5
- 239000002033 PVDF binder Substances 0.000 claims description 4
- 239000002131 composite material Substances 0.000 claims description 4
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 claims description 4
- 229910052839 forsterite Inorganic materials 0.000 claims description 4
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 claims description 4
- 229910052863 mullite Inorganic materials 0.000 claims description 4
- 150000004767 nitrides Chemical class 0.000 claims description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 4
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 3
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
- 239000004734 Polyphenylene sulfide Substances 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 239000004760 aramid Substances 0.000 claims description 3
- 229920006231 aramid fiber Polymers 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 239000004417 polycarbonate Substances 0.000 claims description 3
- 229920000515 polycarbonate Polymers 0.000 claims description 3
- 229920002530 polyetherether ketone Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920000069 polyphenylene sulfide Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- 239000010453 quartz Substances 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 3
- 239000011230 binding agent Substances 0.000 abstract description 3
- 229910052744 lithium Inorganic materials 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 77
- 239000011248 coating agent Substances 0.000 description 15
- 238000000576 coating method Methods 0.000 description 15
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- 230000000052 comparative effect Effects 0.000 description 5
- 239000011162 core material Substances 0.000 description 5
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- 238000010521 absorption reaction Methods 0.000 description 3
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- 239000011159 matrix material Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
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- 230000009286 beneficial effect Effects 0.000 description 2
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- 229910052582 BN Inorganic materials 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 241001391944 Commicarpus scandens Species 0.000 description 1
- 229920001634 Copolyester Polymers 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
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- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
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- 229910052804 chromium Inorganic materials 0.000 description 1
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- 229910052739 hydrogen Inorganic materials 0.000 description 1
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- 239000012779 reinforcing material Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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
-
- 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
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Composite Materials (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Cell Separators (AREA)
Abstract
The application relates to the field of lithium batteries, and relates to a lithium ion battery diaphragm supporting layer and a lithium ion battery diaphragm. The support layer comprises a non-woven fabric layer, wherein the non-woven fabric layer comprises first fibers, second fibers and third fibers; the first fibers are organic fibers, and the second fibers are inorganic fibers; the third fibers are organic binder fibers. The longitudinal tensile strength of the non-woven fabric layer is 5.6N/15 mm-65N/15 mm; the transverse tensile strength is 3.5N/15-55N/15 mm; the average pore diameter is not more than 5 μm, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 10. The addition of the inorganic fibers improves the heat resistance of the non-woven fabric layer. The diameters of the first, second and third fibers ensure that the nonwoven layer has a thinner thickness. The excellent tensile strength of the non-woven fabric layer improves the mechanical strength of the lithium ion battery diaphragm, and is hopeful to improve the use safety of the lithium ion battery.
Description
Technical Field
The application relates to the field of lithium batteries, in particular to a lithium ion battery diaphragm supporting layer and a lithium ion battery diaphragm.
Background
In recent years, the requirements of lithium ion battery diaphragms are rapidly increased under the drive of the explosive development of new energy automobile markets, the vigorous requirements of energy storage and 3C fields, and meanwhile, the requirements on the energy density of the lithium ion batteries are also increased. The diaphragm is used as one of four core materials (positive electrode, negative electrode, electrolyte and diaphragm) of the lithium ion battery, determines the interface structure, internal resistance and the like of the battery, and directly influences the capacity, circulation, safety performance and the like of the battery.
At present, a lithium ion battery diaphragm is mainly a polyolefin diaphragm, but in the application process, if the battery is in thermal runaway due to internal short circuit or overcharge and the like, the internal temperature of the battery is rapidly increased, the size integrity of the polyolefin diaphragm cannot be ensured at high temperature, so that positive and negative electrode materials are in large-area contact, explosion of the battery is caused, and the safety of the battery is threatened.
The non-woven fabric diaphragm has advantages in various novel diaphragm materials due to excellent heat resistance, has long been applied to the fields of nickel-cadmium batteries, nickel-hydrogen batteries, lead-acid batteries, alkaline batteries, super capacitors and the like, but is limited by practical difficulties such as technology, cost and other uncertainties, the application of the non-woven fabric diaphragm in a lithium ion battery is still very limited, the non-woven fabric is difficult to simultaneously meet the requirements of the lithium ion battery diaphragm on both aperture and thickness, and under the prior art, the non-woven fabric diaphragm cannot be directly used as the lithium ion battery diaphragm, is generally only suitable for being used as a supporting layer of the lithium ion battery diaphragm, but is difficult to fully meet the requirements of a high-speed winding process of an assembled battery due to poor tensile mechanical strength of the non-woven fabric compared with a polyolefin porous film. In order to increase the strength of the non-woven fabric and reduce the pore diameter to prevent micro-short circuit, the thickness of the non-woven fabric must be increased; however, the thickness of the non-woven fabric serving as the membrane supporting layer is larger, and the thickness of the non-woven fabric membrane is increased further after the coating layer is formed, so that larger loss is brought to the energy density of the battery, and the non-woven fabric membrane is difficult to fully meet the application requirements of the lithium ion battery membrane at present.
Disclosure of Invention
The embodiment of the application aims to provide a lithium ion battery diaphragm support layer and a lithium ion battery diaphragm.
In a first aspect, the present application provides a lithium ion battery separator support layer comprising: a non-woven fabric layer;
the non-woven fabric layer comprises first fibers, second fibers and third fibers; the first fibers are organic fibers, and the second fibers are inorganic fibers; the third fibers are organic bonding fibers;
the longitudinal tensile strength of the non-woven fabric layer is 5.6N/15 mm-65N/15 mm; the transverse tensile strength of the non-woven fabric layer is 3.5N/15 mm-55N/15 mm; the average pore diameter of the nonwoven fabric layer is not more than 5 μm, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 10.
The non-woven fabric layer combines the organic fiber and the inorganic fiber, gives consideration to the respective advantages of the organic fiber and the inorganic fiber, has complementary actions, and makes up the application defect of a single material. Meanwhile, the organic bonding fiber is compounded, so that the bonding strength between the organic fiber and the inorganic fiber is ensured. The addition of the inorganic fiber greatly improves the heat resistance of the non-woven fabric layer, and the non-woven fabric layer can obtain good heat shrinkage performance when applied to a lithium ion battery diaphragm. The diameters of the first fiber, the second fiber and the third fiber are all micron-sized, the average pore diameter of the non-woven fabric layer is not more than 5 mu m, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 10, so that the non-woven fabric layer is ensured to have a thinner thickness and excellent ion permeability. The longitudinal tensile strength of the non-woven fabric layer is 5.6N/15 mm-65N/15 mm; the transverse tensile strength is 3.5N/15-55N/15 mm, so that the mechanical strength of the lithium ion battery diaphragm can be effectively improved, and the use safety of the lithium ion battery is expected to be improved. The non-woven fabric layer can improve the mechanical strength and the heat shrinkage performance of the lithium ion battery diaphragm on the premise of ensuring the excellent permeability of the thinner ion of the lithium ion battery diaphragm, and ensure the higher battery energy density.
Influence of the longitudinal tensile Strength and the transverse tensile Strength of the nonwoven layer on the application of the lithium-ion separator:
the non-woven fabric layer with the longitudinal tensile strength and the transverse tensile strength in the above ranges is used as a diaphragm base material, and the longitudinal and transverse strength are cooperatively matched, so that the high mechanical strength of the diaphragm is ensured. Compared with the conventional non-woven fabric, the high-strength non-woven fabric can meet higher strength requirements under the same thickness condition, lower thickness can be realized under the same strength, and the reduction of the thickness of the diaphragm means the reduction of ion transmission difficulty, thereby being beneficial to reducing the internal resistance of the battery, promoting the charge and discharge processes of the battery, improving the volume energy density of the battery and lightening the weight of the battery. On the premise of ensuring safety, the thin and high-strength diaphragm is easier to meet the requirements of the downstream lithium battery for thinness, high capacity and high energy density.
The inorganic fibers are added, so that the strength of the non-woven fabric layer is greatly improved, but the defects of poor elasticity and brittleness of the inorganic fibers are easy to cause the brittleness of the non-woven fabric layer to be increased, so that the non-woven fabric layer is easy to be broken and not easy to bend.
The high strength of the separator provides a basic guarantee for the safety of the battery, and in order to increase the energy density of the battery when the battery is assembled, the separator needs to be wound on the surface of the electrode material, simultaneously compacts each electrode, and reduces the spacing between the electrodes as much as possible. For this reason, the separator must have sufficient strength and good winding characteristics, which directly relate to the characteristics of the cell winding, such as the degree of alignment, the degree of tightness, whether the battery is deformed, and the like, and directly affect the performance of the battery.
In other embodiments of the present application, the first fiber diameter is in the range of 1 μm to 6 μm; the diameter of the second fiber is not more than 6 μm, and the diameter of the third fiber is not more than 10 μm.
In other embodiments of the present application, the nonwoven layer includes fourth fibers; the fourth fiber is an organic fiber, the diameter of the fourth fiber is smaller than the diameter of the first fiber, and the diameter of the fourth fiber is nano-scale.
In other embodiments of the present application, the diameter of the fourth fiber is greater than 100nm and less than 1 μm.
In other embodiments of the present application, the third fiber accounts for 15% -40% of the nonwoven layer, and the rest is the first fiber, the second fiber and the fourth fiber;
the second fiber accounts for less than or equal to 35 percent in the first fiber, the second fiber and the fourth fiber; the fourth fiber has a duty ratio of 0 to 25% and is not equal to 0.
In other embodiments of the present application, the melting point or softening point of the third fiber is 100 to 220 ℃; the melting point or softening point of the first fiber and the fourth fiber is higher than the melting point or softening point of the third fiber by not less than 20 ℃.
In other embodiments of the present application, the fiber lengths of the first fiber, the second fiber, the third fiber, and the fourth fiber are all in the range of 1mm to 6 mm.
In other embodiments of the present application, the nonwoven layer has a density of 0.50g/m 3 ～0.9g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the non-woven fabric layer is 5-35 mu m.
In other embodiments of the present application, the first fiber includes: at least one of polyethylene terephthalate fibers, polybutylene terephthalate fibers, polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, ES fibers, polyamide fibers, polyimide fibers, polytetrafluoroethylene fibers, polyvinyl alcohol fibers, polyvinylidene fluoride fibers, polyphenylene sulfide fibers, polyetheretherketone fibers, polyacrylonitrile fibers, polycarbonate fibers, or aramid fibers;
optionally, the second fiber comprises: aluminum silicate fiber, mullite fiber, forsterite fiber, alumina fiber, quartz fiber, zirconia fiber, and SiO 2 CaO-MgO fiber and Al 2 O 3 CaO-based fibers, al 2 O 3 -SiO 2 -ZrO 2 At least one of a series fiber, boride fiber, carbide fiber, nitride fiber, magnesium aluminum silicon ternary glass fiber, magnesium aluminum silicon series glass fiber or silicon aluminum calcium magnesium series glass fiber;
optionally, the third fiber comprises: at least one of polyethylene terephthalate undrawn fiber, polybutylene terephthalate undrawn fiber, polyolefin fiber, or sheath-core structure composite fiber.
In a second aspect, the present application provides a lithium ion battery separator, including a lithium ion battery separator support layer provided by any one of the foregoing embodiments.
Detailed Description
Hereinafter, embodiments of the present application are described in detail so that those skilled in the art to which the present application pertains can easily implement the present application. Embodiments of the present application are provided to more fully describe the present application to one of ordinary skill in the art. Therefore, the embodiments of the present application may be modified in various different forms, and the scope of the present application is not limited to the embodiments described below.
Throughout the specification of this application, when a portion is stated as "comprising" a certain structural element, unless stated otherwise, it is intended that other structural elements may also be included, rather than excluded.
Throughout the specification of this application, when a step is described as "above" or "before" another step, this includes not only the case where a step has a direct chronological relationship with another step, but also the same rights as in the case of an indirect chronological relationship where the order of two steps may be changed, such as a mixing step after each step.
The terms "about," "substantially," and the like, as used throughout the specification of this application, are used as a numerical or near-numerical meaning in the sense of mention that inherent manufacturing and material tolerances are suggested to be present, to prevent unreasonable use of the disclosure by an unscrupulous infringer of mention of an exact or absolute value in order to assist the invention. The term "(performing) … … step" or "… … step" as used throughout this application does not mean "step for … …".
The inventor found that the inorganic fiber has outstanding characteristics of high thermal stability, high mechanical strength, high temperature and pressure resistance, and good chemical stability, and the organic fiber has advantages of good flexibility and processability, but poor heat resistance and mechanical properties compared with the inorganic fiber.
Inorganic fibers are doped in an organic fiber raw material, the inorganic fibers are wrapped by the organic fibers to provide bonding strength and form an integral structure, the inorganic fibers serve as reinforcing materials to strengthen the structural strength of the non-woven fabric, after the inorganic fibers and the organic fibers are blended, the inorganic fibers are uniformly distributed in an organic fiber matrix, the modulus of the inorganic fibers is larger than that of the organic fiber matrix, and under the same strain, the bearing capacity of the inorganic fibers is larger; when the diaphragm is acted by external force, the force is transferred from the organic fiber matrix to the inorganic fiber, the force direction is changed, namely the transfer is carried out along the fiber orientation direction, and the transfer also plays a role in dispersing the force to a certain extent, so that the capability of the film material for bearing the external force is enhanced, and the mechanical property of the non-woven fabric is greatly improved in a macroscopic sense.
The embodiment of the application provides a lithium ion battery diaphragm support layer, which comprises: a non-woven fabric layer.
The nonwoven fabric layer comprises first fibers, second fibers and third fibers; the first fibers are organic fibers, and the second fibers are inorganic fibers; the third fibers are organic binder fibers.
The organic fiber and the inorganic fiber are compounded, the advantages of the organic fiber and the inorganic fiber are considered, the effects are complementary, the application defect of a single material is overcome, the high mechanical strength and high heat resistance which are not originally available for the single fiber material can be developed, and the application requirements of the lithium ion battery diaphragm on the mechanical strength and the thermal stability can be met.
In some embodiments of the present application, the first fibers have a diameter in the range of 1 μm to 6 μm. Further alternatively, the diameter of the first fiber is in the range of 1.5 μm to 5.5 μm.
Illustratively, the diameters of the first fibers may each be selected to be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or 6 μm.
Further, the diameter of the second fibers is not greater than 6 μm, further alternatively, the diameter of the second fibers is 0 to 6 μm and is not equal to 0. Illustratively, the second fiber has a diameter of 0.1 μm, 0.5 μm, 2 μm, 4 μm, or 5 μm.
Further, the diameter of the third fiber is not more than 10 μm. Further alternatively, the diameter of the third fiber is 0 to 10 μm and is not equal to 0. The diameter of the third fiber is illustratively 0.2 μm, 0.4 μm, 1 μm, 7 μm or 9 μm.
If the diameters of the first fiber and the second fiber are larger than 6 μm, and the diameter of the third fiber is larger than 10 μm, the thickness of the obtained non-woven fabric layer will be too large, and for a lithium ion battery with a certain specification size, the larger the thickness of the non-woven fabric membrane means that the amount of active substances during the assembly of the battery will be reduced, and the battery capacity is reduced; meanwhile, the possibility of large holes generated by the non-woven fabric is increased due to the excessively coarse fibers, the expected pore diameter and the distribution thereof are not easy to obtain, and meanwhile, coating slurry easily permeates from the upper layer to the lower layer through the through holes, so that the possibility of defects such as pinholes and the like generated by the membrane coating layer is increased.
Further, in some embodiments of the present application, the nonwoven layer includes fourth fibers; the fourth fiber is an organic fiber, the diameter of the fourth fiber is smaller than the diameter of the first fiber, and the diameter of the fourth fiber is nano-scale.
The nanometer organic fiber has fine diameter, and when making certain amount of non-woven fabric, nanometer organic fiber is added to increase the number of fibers, promote the contact and combination between fibers and increase the cross bonding points of the fibers, so as to improve the bonding tightness of the fibers in the non-woven fabric. Meanwhile, the fine fibers are favorable for filling the pores among the fibers, or the pores among the fiber layers in the thickness direction of the non-woven fabric are properly filled, so that coarse and fine fibers and organic and inorganic fibers are mutually interwoven and laminated, a firm mixed pore structure with mutually nested macropores and pores can be formed, the pore diameter of the non-woven fabric is greatly reduced, the regulation of the pore diameter is realized, the pore structure of the non-woven fabric is finer, and the pores of the non-woven fabric are more uniform and are convenient to regulate and control.
The more fine non-woven fabrics layer of structure improves the liquid absorption rate, the liquid retention rate to electrolyte, and then the affinity of non-woven fabrics diaphragm and electrolyte is stronger, is favorable to electrolyte to form one deck stable adsorbed layer on the diaphragm surface, and then improves the interface nature of diaphragm, promotes the transmission of lithium ion in battery reaction process to promote battery performance. In addition, the high liquid absorption and high liquid retention rate can effectively prevent the phenomenon of electrolyte exhaustion caused by liquid leakage and other reasons in the use process of the non-woven fabric diaphragm, the filling time of the electrolyte is shortened in the battery assembly production process, and the manufacturing cost is reduced.
In addition, the addition of the nanoscale organic fibers increases the total specific surface area of the fibers of the non-woven fabric layer, and is beneficial to increasing the binding force between the fibers and the coating slurry and improving the retention rate of the slurry when coating is carried out on the surface of the non-woven fabric layer subsequently.
Further, in some embodiments of the present application, the diameter of the fourth fiber is greater than 100nm and less than 1 μm.
Further alternatively, the diameter of the fourth fiber is greater than 110nm and less than 0.9 μm.
Illustratively, the diameter of the fourth fiber described above is 0.15 μm, 0.20 μm, 0.30 μm, 0.40 μm, 0.50 μm, 0.60 μm, 0.70 μm, or 0.80 μm.
Further, in some embodiments of the present application, the average pore size of the nonwoven fabric layer is not greater than 5 μm.
Further alternatively, the nonwoven fabric layer has an average pore diameter of 1 μm to 5 μm; further alternatively, the nonwoven fabric layer has an average pore diameter of 1 μm to 3 μm.
The average pore diameter of the nonwoven fabric layer is exemplified by 1.2 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm.
Further, in some embodiments of the present application, the ratio of the maximum pore diameter to the average pore diameter of the nonwoven fabric layer is not less than 1 and not more than 10. Further alternatively, the ratio of the maximum pore diameter to the average pore diameter of the nonwoven fabric layer is not less than 1 and not more than 5.
Illustratively, the ratio of the maximum pore size to the average pore size of the nonwoven layer described above is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
Under the condition of the same thickness, the larger the aperture of the diaphragm is, the smaller the resistance to lithium ion migration is, but the mechanical property and the electronic insulation property of the diaphragm are reduced, and the diaphragm is easy to puncture to cause micro short circuit of the battery; too small a pore diameter increases internal resistance, resulting in low ion transport efficiency. The micropores are unevenly distributed, so that local current is easy to form when the battery works, the battery performance is influenced, and even safety problems are caused. The average pore diameter of the non-woven fabric layer is not more than 5 mu m, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 10, so that the separator has a rich porous structure. The porous structure is a guarantee of uniform current density, and it is vital to ensure uniform and abundant pore structure in the preparation process of the diaphragm, so that the electrode performance attenuation caused by current asymmetry in high-power discharge is avoided, the internal short circuit or micro short circuit is avoided, the liquid absorption rate and the liquid retention rate are better, the efficient and rapid transfer of ions is ensured, and the circulation of the battery core is facilitated.
When the average pore diameter of the nonwoven fabric layer is more than 5 μm and the maximum pore diameter/average pore diameter ratio is more than 10, the coating paste easily permeates from the coating surface to the back surface, through holes are formed in the coating layer, and finally the coating paste adheres to the surface of the guide roller, causing foreign matter contamination.
Further, in some embodiments of the present application, the first fiber includes: at least one of polyethylene terephthalate fibers, polybutylene terephthalate fibers, polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, ES fibers, polyamide fibers, polyimide fibers, polytetrafluoroethylene fibers, polyvinyl alcohol fibers, polyvinylidene fluoride fibers, polyphenylene sulfide fibers, polyetheretherketone fibers, polyacrylonitrile fibers, polycarbonate fibers, or aramid fibers.
In other alternative embodiments of the present application, the first fiber may be selected from polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, and polyolefin fibers other than ES fibers.
Further, the polyamide fiber may be PA66 fiber.
Further, in some embodiments of the present application, the material of the fourth fiber may be selected from various materials selected from the first fiber. It should be noted that, in a specific embodiment, the first fiber and the fourth fiber may be identical or different.
Illustratively, when the first fibers and the fourth fibers are the same material, the first fibers may be selected from polyethylene terephthalate fibers, and likewise, the fourth fibers may be selected from polyethylene terephthalate fibers, where the two differ only in fiber diameter, and the first fibers are micron-sized fibers; the fourth fiber is a nanoscale fiber; for example, the first fibers have a diameter of 1.3 μm; the diameter of the fourth fiber was 0.3. Mu.m.
Illustratively, when the materials of the first and fourth fibers are not the same, the first fiber may be selected from ES fibers; the fourth fiber is polyamide fiber; at this time, the materials are different, and the fiber diameters are also different. For example, the diameter of the first fiber is 2.3 μm; the diameter of the fourth fiber was 0.4. Mu.m.
Further, in some embodiments of the present application, the second fiber includes: aluminum silicate fiber, mullite fiber, forsterite fiber, alumina fiber, quartz fiber, zirconia fiber, and SiO 2 CaO-MgO fiber and Al 2 O 3 CaO-based fibers, al 2 O 3 -SiO 2 -ZrO 2 At least one of a series fiber, boride fiber, carbide fiber, nitride fiber, magnesium aluminum silicon ternary glass fiber, magnesium aluminum silicon series glass fiber or silicon aluminum calcium magnesium series glass fiber.
Further alternatively, the aluminum silicate fibers described above may be selected from chromium-containing, zirconium-containing, or boron-containing aluminum silicate fibers.
In other alternative embodiments of the present application, the aluminum silicate fibers described above may also be selected from other aluminum silicate fibers common in the art.
In other alternative embodiments of the present application, the second fibers may be selected from mullite fibers and ceramic fibers other than forsterite fibers.
Further alternatively, the nitride fiber is selected from a silicon nitride fiber or a boron nitride fiber.
Further, in some embodiments of the present application, the third fiber includes: at least one of polyethylene terephthalate undrawn fiber, polybutylene terephthalate undrawn fiber, polyolefin fiber, or sheath-core structure composite fiber.
Further alternatively, the polyolefin fiber is selected from polyethylene, polypropylene, polyvinyl chloride, and other polyolefin fibers.
Further alternatively, the sheath-core structural composite fiber described above selects polyolefin, copolyester, copolyamide, or the like as the sheath material.
Further, in some embodiments of the present application, the nonwoven fabric layer has a third fiber content of 15% to 40% by mass, and the balance of the first fiber, the second fiber, and the fourth fiber; the second fiber accounts for less than or equal to 35 percent in the first fiber, the second fiber and the fourth fiber; the fourth fiber has a duty ratio of 0 to 25% and is not equal to 0.
Further alternatively, the non-woven fabric layer comprises 15-39% of third fibers and the balance of first fibers, second fibers and fourth fibers in percentage by mass; the first fiber, the second fiber and the fourth fiber have the second fiber accounting for 0-34 percent and are not equal to 0; the fourth fiber has a duty ratio of 0 to 24% and is not equal to 0.
Illustratively, the nonwoven fabric layer has a third fiber content of 35% by mass, and the balance of first, second, and fourth fibers; the second fiber accounts for 33% of the first fiber, the second fiber and the fourth fiber; the fourth fiber had a duty cycle of 23% and the remainder were the first fibers.
If the mass fraction of the inorganic fibers is more than 35wt%, the brittleness of the nonwoven fabric increases, the strength thereof decreases, and the nonwoven fabric is easily broken or broken during the winding process. The bonding force between the fibers is ensured by the bonding fibers, if the content of the bonding fibers is too low, and the content of the organic fibers is too high, the fibers in the non-woven fabric cannot be fully adhered and bonded, the reticular structure is loose and difficult to be fixed and shaped, and the mechanical strength of the non-woven fabric is difficult to be ensured. If the content of the bonding fiber is too high, but the content of the organic fiber is low, the excessive bonding fiber is melted on the surface of the non-woven fabric, so that the blocking of holes is serious, and the expected pore structure is difficult to obtain.
Further, the melting point or softening point of the third fiber is 100-220 ℃; the melting point or softening point of the first fiber and the fourth fiber is higher than the melting point or softening point of the third fiber by not less than 20 ℃.
The third fiber is organic bonding fiber, the melting point or softening point is relatively low, the bonding fiber is partially or completely melted when the hot rolling treatment is carried out, the fibers in the non-woven fabric are adhered to each other, and a three-dimensional net structure of the firm non-woven fabric is formed after cooling and solidifying. However, if the melting point or softening point of the bonding fiber is too low, the bonding fiber is easy to excessively melt in the hot pressing treatment process, and the bonding roller is serious; if the melting point or softening point of the binder fiber is too high, it cannot be melted in time at the time of hot pressing, thereby making it difficult to obtain sufficient adhesive strength of the nonwoven fabric.
Further alternatively, the third fiber has a melting point or softening point of 110 to 210 ℃; the melting point or softening point of the first fiber and the fourth fiber is higher than the melting point or softening point of the third fiber by not less than 20 ℃.
The melting point or softening point of the first fiber and the fourth fiber may be the same or different.
Illustratively, the third fiber has a melting point or softening point of 200 ℃; the melting point or softening point of the first fiber is the same as the melting point or softening point of the fourth fiber. For example: the first fiber has a melting point or softening point of 230 ℃; the fourth fiber has a melting point or softening point of 230 ℃. Or the melting point or softening point of the first fiber is different from the melting point or softening point of the fourth fiber. For example: the first fiber has a melting point or softening point of 240 ℃; the fourth fiber has a melting point or softening point of 235 ℃.
Further, the fiber lengths of the first fiber, the second fiber, the third fiber and the fourth fiber are all in the range of 1 mm-6 mm. Further alternatively, the first, second, third, and fourth fibers each have a fiber length in the range of 1.1mm to 5.9 mm. Further alternatively, the first, second, third, and fourth fibers each have a fiber length in the range of 2.5mm to 5.5 mm.
If the fiber length is less than 1mm, the problem that the strength of the non-woven fabric is too low may exist, and even the fiber cannot be formed into paper; if the fiber length is more than 6mm, the overlong fibers are easy to agglomerate and tangle, so that serious appearance performance defects of the non-woven fabric are caused.
Further, the nonwoven fabric layer has a thickness of 5 μm to 35 μm. Further alternatively, the nonwoven fabric layer has a thickness of 6 μm to 34 μm. Exemplary nonwoven layers have a thickness of 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 18 μm, 20 μm, 22 μm, 25 μm, 30 μm or 33 μm.
The thickness of the nonwoven layer directly affects the thickness of the coated separator. If the thickness of the non-woven fabric layer is larger than 35 mu m, the thickness of the separator is too large, the internal resistance of the battery is increased, the ion migration is blocked, and the battery circulation is poor. If the thickness of the non-woven fabric layer is less than 5 mu m, the thermal stability and mechanical strength of the separator are greatly reduced, the mechanical requirements of the assembly process are difficult to meet, the separator is easy to break down to cause short circuit of the battery, and the stability and safety of the separator product are challenged.
Further, the density of the nonwoven fabric layer was 0.50g/m 3 ～0.9g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the Further alternatively, the nonwoven layer has a density of 0.51g/m 3 ～0.89g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the Illustratively, the nonwoven layer has a density of 0.54g/m 3 、0.62g/m 3 、0.73g/m 3 、0.75g/m 3 、0.77g/m 3 、0.80g/m 3 、0.82g/m 3 、0.85g/m 3 。
When the density of the non-woven fabric layer is less than 0.50g/m 3 In this case, the coating paste excessively penetrates the nonwoven fabric layer to the back surface. When the density is greater than 0.9g/m 3 When the non-woven fabric layer is used, the holes may be seriously blocked, enough porosity cannot be ensured, the ion transmission efficiency in the battery reaction is affected, and finally the electrical property of the non-woven fabric diaphragm is insufficient.
Further, in some embodiments of the present application, the nonwoven fabric layer has a longitudinal tensile strength of 5.6N/15mm to 65N/15mm;
further alternatively, the nonwoven fabric layer has a longitudinal tensile strength of 7.4N/15mm to 50N/15mm.
Further alternatively, the nonwoven fabric layer has a longitudinal tensile strength of 9.3N/15mm to 46.7N/15mm.
The nonwoven layers described above have, for example, a machine direction tensile strength of 8.23N/15mm, 10.29N/15mm, 14.41N/15mm, 18.52N/15mm, 20.58N/15mm, 22.64N/15mm, 26.46N/15mm, 29.11N/15mm, 33.08N/15mm, 35.35N/15mm, 41.46N/15mm, 44.07N/15mm, 48.23N/15mm, 55.13N/15mm, 64.68N/15mm.
The transverse tensile strength of the non-woven fabric layer is 3.5N/15 mm-55N/15 mm.
Further, the transverse tensile strength of the nonwoven fabric layer is 5.4N/15mm to 45N/15mm.
Further alternatively, the nonwoven layer has a transverse tensile strength of 7.8N/15mm to 33.1N/15mm.
Exemplary, the cross-directional tensile strength of the nonwoven layer is 5.88N/15mm, 7.35N/15mm, 10.29N/15mm, 14.72N/15mm, 18.58N/15mm, 20.58N/15mm, 25.73N/15mm, 29.41N/15mm, 33.10N/15mm.
The longitudinal tensile strength of the non-woven fabric layer is 5.6N/15 mm-65N/15 mm; the transverse tensile strength is 3.5N/15-55N/15 mm, so that the mechanical strength of the lithium ion battery diaphragm can be effectively improved, and the use safety of the lithium ion battery is expected to be improved.
The nonwoven fabric layer of the present application is not particularly limited in its production method. For example, the fibrous base paper may be prepared by a nonwoven fabric preparation method known in the art, and then the formed fibrous base paper may be subjected to a thermal calendering process, optionally at a temperature ranging from 100 ℃ to 300 ℃.
Some embodiments of the present application provide a lithium ion battery separator comprising a lithium ion battery separator support layer provided in any one of the foregoing manners.
The features and capabilities of the present application are described in further detail below in connection with the examples:
example 1
The lithium ion battery diaphragm is prepared according to the following steps:
and S1, preparing a non-woven fabric layer.
According to the raw material fiber proportion in Table 1, adopting an inclined wire paper machine to manufacture fiber base paper, and then carrying out hot calendering treatment on the fiber base paper, wherein the treatment temperature is 230+/-5 ℃; the hot calender uses a steel roll/soft roll combination.
And S2, preparing a lithium ion battery diaphragm.
And (3) cutting the non-woven fabric prepared in the step (S1) to obtain a sample with the size of A4, and coating the surface of the non-woven fabric sample with alumina ceramic slurry by adopting a mesh roll. Wherein, the alumina ceramic slurry comprises 35 percent of alumina, 10 percent of PVDF and the balance of water according to mass percent. And (5) drying the non-woven fabric sample after coating to finally obtain the lithium ion battery diaphragm.
Examples 2 to 6
A lithium ion battery separator was provided, and the raw material fiber proportions were carried out as shown in table 1, in the same manner as in the preparation procedure of example 1.
Comparative examples 1 to 6
A lithium ion battery separator was provided, and the raw material fiber proportions were carried out as shown in table 1, in the same manner as in the preparation procedure of example 1.
TABLE 1
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Experimental example
(1) The properties of the nonwoven fabric layers obtained in step S1 of examples 1 to comparative example 6 were examined.
Wherein the "areal density" of the nonwoven fabric is measured according to the GB/T451.2-2002 method. The "density" of the nonwoven fabric was obtained by dividing the "areal density" of the nonwoven fabric by the "thickness" of the nonwoven fabric, and the "thickness" of the nonwoven fabric was measured according to the GB/T451.3-2002 method. The "pore size" of the nonwoven fabric was measured according to the method of GB/T32361-2015. The "tensile strength" of the nonwoven fabric was measured according to the GB/T12914-2008 method. The "heat shrinkage" of the nonwoven fabric was measured according to the GB/T12027-2004 method. The "folding endurance" of the nonwoven fabric was measured according to the GB/T457-2008 method.
(2) The performance of the lithium ion battery separator manufactured in step S2 of example 1 to comparative example 6 was examined.
The pinhole number is tested according to the method; during measurement, samples to be measured are flatly paved on the upper surface of the lamp box, and the number of visible pinholes in each square meter of non-woven fabric is used as a test result through human eyes to observe conditions.
Coating thickness, testing according to the method; the thickness of the non-woven fabric is subtracted from the thickness of the pure non-woven fabric after coating.
Coating adhesion, tested according to the method; the surface density of the non-woven fabric after coating is subtracted from the surface density of the pure non-woven fabric.
The coating liquid penetrated to the back surface and tested according to the method. During measurement, the condition is observed through human eyes, the percentage of the area of the coating liquid on the back surface of the non-woven fabric in each square meter is taken as a detection result, and the evaluation standard is that: o: no coating liquid penetrated to the back surface, acceptable level; x: coating liquid penetration to the back surface and unacceptable levels occur.
The test results are shown in tables 2-1 and 2-2.
TABLE 2-1
TABLE 2-2
As can be seen from tables 2-1 and 2-2, the nonwoven fabrics of examples 1-6 of the present application had a longitudinal tensile strength of 152.1N/15mm to 174.3N/15mm; the transverse tensile strength of the non-woven fabric is 59.2N/15-81.1N/15 mm, so that the mechanical strength of the lithium ion battery diaphragm is effectively improved, and the non-woven fabric has good heat shrinkage performance, especially the high-temperature (200 ℃) heat shrinkage performance is improved.
When example 7 and comparative example 2 were compared, example 8 and comparative example 4 showed that when the nonwoven fabric strength was too low (the longitudinal tensile strength was less than 5.6N/15mm and the transverse strength was less than 3.5N/mm), the folding endurance of the nonwoven fabric film was significantly lowered, the folding endurance and bending ability of the nonwoven fabric were lowered, and the suitability for the winding process was also deteriorated.
The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims (10)
1. A lithium ion battery separator support layer, comprising: a non-woven fabric layer;
the non-woven fabric layer comprises first fibers, second fibers and third fibers; the first fibers are organic fibers, and the second fibers are inorganic fibers; the third fibers are organic bonding fibers;
the longitudinal tensile strength of the non-woven fabric layer is 5.6N/15 mm-65N/15 mm; the transverse tensile strength of the non-woven fabric layer is 3.5N/15 mm-55N/15 mm; the average pore diameter of the non-woven fabric layer is not more than 5 mu m, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 10; the nonwoven fabric layer comprises fourth fibers; the fourth fibers are organic fibers, the diameters of the fourth fibers are smaller than those of the first fibers, and the diameters of the fourth fibers are nanometer-scale; in the non-woven fabric layer, the third fiber accounts for 15-40% by mass, and the rest is the first fiber, the second fiber and the fourth fiber;
the second fiber accounts for less than or equal to 35 percent in the first fiber, the second fiber and the fourth fiber; the fourth fiber has a duty ratio of 0-25% and is not equal to 0.
2. The lithium ion battery separator support layer of claim 1, wherein,
the diameter of the first fiber is in the range of 1-6 mu m;
the diameter of the second fiber is not more than 6 μm, and the diameter of the third fiber is not more than 10 μm.
3. The lithium ion battery separator support layer of claim 1, wherein,
the fourth fibers have a diameter greater than 100nm and less than 1 μm.
4. The lithium ion battery separator support layer of claim 1, wherein,
the melting point or softening point of the third fiber is 100-220 ℃; the melting point or softening point of the first fiber and the fourth fiber is higher than the melting point or softening point of the third fiber by not less than 20 ℃.
5. The lithium ion battery separator support layer of claim 1, wherein,
the fiber lengths of the first fiber, the second fiber, the third fiber and the fourth fiber are all in the range of 1 mm-6 mm.
6. The lithium ion battery separator support layer of claim 5, wherein,
the density of the non-woven fabric layer is 0.50g/m 3 ~0.9 g/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the non-woven fabric layer is 5-35 mu m.
7. The lithium ion battery separator support layer according to any one of claim 1 to 6, wherein,
the first fiber includes: at least one of polyethylene terephthalate fibers, polybutylene terephthalate fibers, polyethylene fibers, polypropylene fibers, polyvinyl chloride fibers, ES fibers, polyamide fibers, polyimide fibers, polytetrafluoroethylene fibers, polyvinyl alcohol fibers, polyvinylidene fluoride fibers, polyphenylene sulfide fibers, polyetheretherketone fibers, polyacrylonitrile fibers, polycarbonate fibers, or aramid fibers.
8. The lithium ion battery separator support layer according to any one of claim 1 to 6, wherein,
the second fiber includes: aluminum silicate fiber, mullite fiber, forsterite fiber, alumina fiber, quartz fiber, zirconia fiber, and SiO 2 CaO-MgO fiber and Al 2 O 3 CaO-based fibers, al 2 O 3 -SiO 2 -ZrO 2 At least one of a series fiber, boride fiber, carbide fiber, nitride fiber, magnesium aluminum silicon ternary glass fiber, magnesium aluminum silicon series glass fiber or silicon aluminum calcium magnesium series glass fiber.
9. The lithium ion battery separator support layer according to any one of claim 1 to 6, wherein,
the third fiber includes: at least one of polyethylene terephthalate undrawn fiber, polybutylene terephthalate undrawn fiber, polyolefin fiber, or sheath-core structure composite fiber.
10. A lithium ion battery separator, characterized by comprising the lithium ion battery separator support layer of any one of claims 1-9.
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| CN110429227A (en) * | 2019-07-03 | 2019-11-08 | 莱州联友金浩新型材料有限公司 | A kind of preparation method of fibrous type lithium ion battery separator |
| CN111816824A (en) * | 2020-06-11 | 2020-10-23 | 深圳市星源材质科技股份有限公司 | Non-woven fabric used as lithium ion battery diaphragm base film, diaphragm and lithium ion battery |
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