CN110649212A - Wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper and preparation method thereof - Google Patents
Wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper and preparation method thereof Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 127
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 126
- 239000000835 fiber Substances 0.000 title claims abstract description 117
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 title claims abstract description 107
- 239000002131 composite material Substances 0.000 title claims abstract description 58
- 229920001131 Pulp (paper) Polymers 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 238000000576 coating method Methods 0.000 claims abstract description 56
- 239000011248 coating agent Substances 0.000 claims abstract description 54
- 229920001721 polyimide Polymers 0.000 claims abstract description 52
- 239000009719 polyimide resin Substances 0.000 claims abstract description 51
- 239000002121 nanofiber Substances 0.000 claims abstract description 49
- 238000000034 method Methods 0.000 claims abstract description 45
- 238000001035 drying Methods 0.000 claims abstract description 39
- 238000007731 hot pressing Methods 0.000 claims abstract description 22
- 238000010009 beating Methods 0.000 claims abstract description 7
- 239000011148 porous material Substances 0.000 claims description 34
- 238000004537 pulping Methods 0.000 claims description 24
- 238000002156 mixing Methods 0.000 claims description 18
- 239000011122 softwood Substances 0.000 claims description 18
- 239000011121 hardwood Substances 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 13
- 238000002791 soaking Methods 0.000 claims description 13
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 8
- 239000002028 Biomass Substances 0.000 claims description 6
- RLSSMJSEOOYNOY-UHFFFAOYSA-N m-cresol Chemical compound CC1=CC=CC(O)=C1 RLSSMJSEOOYNOY-UHFFFAOYSA-N 0.000 claims description 6
- 238000009736 wetting Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 5
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 239000002002 slurry Substances 0.000 claims description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 3
- 229920002749 Bacterial cellulose Polymers 0.000 claims description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 2
- 239000005016 bacterial cellulose Substances 0.000 claims description 2
- 238000009388 chemical precipitation Methods 0.000 claims description 2
- 238000003618 dip coating Methods 0.000 claims description 2
- 238000007756 gravure coating Methods 0.000 claims description 2
- 238000010297 mechanical methods and process Methods 0.000 claims description 2
- 238000000593 microemulsion method Methods 0.000 claims description 2
- 239000003495 polar organic solvent Substances 0.000 claims description 2
- 238000004528 spin coating Methods 0.000 claims description 2
- 238000005507 spraying Methods 0.000 claims description 2
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 10
- 239000002994 raw material Substances 0.000 abstract description 6
- 238000009776 industrial production Methods 0.000 abstract 1
- 239000000123 paper Substances 0.000 description 162
- 229920002678 cellulose Polymers 0.000 description 21
- 239000001913 cellulose Substances 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 14
- 239000003792 electrolyte Substances 0.000 description 11
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 239000011268 mixed slurry Substances 0.000 description 8
- 239000004698 Polyethylene Substances 0.000 description 6
- -1 polyethylene Polymers 0.000 description 6
- 239000004743 Polypropylene Substances 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 5
- 230000001070 adhesive effect Effects 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000004745 nonwoven fabric Substances 0.000 description 5
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 230000035699 permeability Effects 0.000 description 4
- 229920001046 Nanocellulose Polymers 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 3
- 239000011247 coating layer Substances 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000011031 large-scale manufacturing process Methods 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 229920000573 polyethylene Polymers 0.000 description 3
- 229920001155 polypropylene Polymers 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229920003043 Cellulose fiber Polymers 0.000 description 2
- 229920002522 Wood fibre Polymers 0.000 description 2
- 230000006399 behavior Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000002655 kraft paper Substances 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000002103 nanocoating Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 239000002025 wood fiber Substances 0.000 description 2
- 239000004952 Polyamide Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000003490 calendering Methods 0.000 description 1
- 206010061592 cardiac fibrillation Diseases 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
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- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 230000002600 fibrillogenic effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
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- 238000005470 impregnation Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- GDOPTJXRTPNYNR-UHFFFAOYSA-N methyl-cyclopentane Natural products CC1CCCC1 GDOPTJXRTPNYNR-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000011800 void material Substances 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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- 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
- H01M50/411—Organic 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
- H01M50/431—Inorganic 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
- H01M50/44—Fibrous material
-
- 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
Abstract
The invention relates to wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper and a preparation method thereof. The preparation method comprises the steps of taking wood pulp fibers as raw materials, preparing fiber base paper through a paper preparation process by adopting a high-beating-degree viscous beating mode, preparing mixed coating from nano fibers and nano barium sulfate composite materials, uniformly coating the mixed coating on two sides of the base paper, treating the coated base paper in a hot-pressing drying mode, impregnating polyimide resin solution, and drying to obtain the lithium battery diaphragm paper. The preparation process is mature, the method is simple, and the raw materials are environment-friendly; the composite material of the nano-fiber and the nano-barium sulfate is used as a coating, and the larger aperture of the diaphragm base paper is filled, so that the composite material has good wettability and high-temperature stability; the polyimide resin is used as the outer layer of the diaphragm, so that the long-time high-temperature thermal stability of the lithium battery diaphragm is improved. The lithium battery diaphragm paper prepared by the invention is novel and environment-friendly in material and convenient for industrial production.
Description
Technical Field
The invention relates to wood pulp fiber/nano barium sulfate composite lithium battery diaphragm paper and a preparation method thereof, in particular to wood pulp fiber/nano barium sulfate composite lithium battery diaphragm paper which is excellent in wettability, high in thermal stability, high in film strength, simple in process, environment-friendly and pollution-free and a preparation method thereof, belonging to the technical field of papermaking and batteries.
Background
With the rapid development of science and technology, the application of batteries is increasingly wide. Lithium batteries, because of their high energy density, stable cycling characteristics, low discharge rates and high operating voltages, have been successfully used in portable electronic devices such as mobile phones, computers and cameras, and are expected to be used in electric vehicles and energy storage systems. The lithium battery is composed of a positive electrode, a negative electrode, an electrolyte, a separator and the like. The diaphragm is the most important part with the technical content in the lithium battery component, and the chemical performance of the diaphragm has very important influence on the cycle performance, rate capability and safety performance of the battery. The diaphragm is isolated between the positive electrode and the negative electrode so as to prevent the internal short circuit of the battery caused by the physical contact of the two electrodes, and meanwhile, an ion transmission channel is provided, so that the free transfer of lithium ions during the charge and discharge of the battery is realized, and the current is formed. The battery separator must have good uniformity and insulating properties, good mechanical strength, excellent electrolyte wettability and thermal stability.
Commercial separators currently used in lithium batteries are polyethylene separators, polypropylene separators, and composite separators thereof. Such separators have good chemical stability and mechanical strength and are widely used. However, such membranes have two inherent limitations: one is low porosity. The low porosity due to its semi-crystalline structure and melt-blown technology hinders the absorption of the liquid electrolyte by the separator, makes the separator have poor electrolyte wettability, results in low rate capability of the battery, and creates high ionic conduction resistance in the interfacial layers of the separator and the electrodes, compromising the safety of the lithium ion battery. Secondly, the thermal stability is poor. The melting point of polyethylene is about 130 c and the melting point of polypropylene is about 160 c, which causes such a separator to exhibit severe dimensional shrinkage at high temperature, and in the case where some dangerous behaviors occur, such as overcharge and high thermal shock, closed-cell behavior occurs in the PE layer as the temperature of the battery approaches the melting point of PE, ion transport paths are blocked, and thus electrochemical reaction is terminated, but if the temperature is continuously increased above the melting point of PP, the separator shrinks, and direct contact between electrodes is shorted, which may eventually lead to explosion of the battery.
In recent years, researchers have made many efforts to develop new materials for battery separators with high thermal stability and high electrolyte wettability. The current novel battery diaphragm materials mainly comprise the following materials:
(1) a nonwoven fabric-based separator. The nonwoven fabric is formed by orienting or randomly arranging organic fibers to form a porous film. The separator has better electrolyte wettability than the commercialized polyethylene and polypropylene separators. The non-woven fabric film presents a three-dimensional pore structure, and the structure can effectively improve the performances of electrolyte liquid absorption rate, electrolyte liquid retention rate, air permeability and the like. However, the lithium battery diaphragm has the problems of low film forming strength, large aperture size, uneven aperture range distribution and the like. The prepared lithium battery has the problems of low capacitance, low cyclic discharge rate and the like.
(2) An inorganic composite separator. The inorganic composite diaphragm is a porous composite film formed by coating a coating formed by an adhesive and inorganic nanoparticles on a diaphragm substrate, has excellent electrolyte wettability, can absorb and retain a large amount of electrolyte, has certain help for prolonging the service life of a battery, and still has excellent thermal dimensional stability, good cycle rate performance and safety performance under the condition of high temperature. However, the lithium battery diaphragm has the problems that the adhesive is not resistant to high temperature, the inorganic coating layer falls off at high temperature and the like, the preparation process is complex, the cost is high, and the large-scale production is not facilitated at the present stage.
(3) Polyimide material lithium battery diaphragm. The polyimide resin is a novel special insulating material, and the lithium battery diaphragm prepared from the polyimide resin has the characteristics of high strength, high modulus, high temperature resistance, radiation resistance, corrosion resistance and the like. At present, two methods are mainly used for preparing the lithium battery diaphragm by taking polyimide resin as a material, one method is to interweave polyamide fibers with an adhesive to form a porous membrane and then coat other materials to fill pores. The other is formed by directly coating polyimide resin, and the diaphragm has high strength, small pore size, narrow distribution range and poor wettability.
Chinese patent document CN108172738A (application number: 201711368653.5) discloses a preparation method of cellulose-based lithium battery diaphragm base paper, which comprises the steps of dispersing polysulfonamide fibers into water to prepare the cellulose-based lithium battery diaphragm base paper; lignocellulosic pulp can be made in either of two ways. The first method comprises the following steps: pulping the cellulose pulp until the pulping degree is 40-92 SR to obtain the lignocellulose pulp. And the second method comprises the following steps: and (3) performing latency disintegration on the cellulose pulp to obtain lignocellulose pulp. Wherein, the cellulose pulp is of various types, such as one or more of bleached softwood kraft pulp, bleached hardwood kraft pulp and wood fiber mechanical pulp. Preparing mixed slurry, wherein the mass ratio of the polysulfonamide fibers to the lignocellulose in the mixed slurry is 1: (1-4), such as 1:2, 1:3, 1:4 or 1: 1; wherein adding nanocellulose to the mixed slurry comprises: in the first mode, 4-12 g of nano-cellulose is added into every 100g of mixed slurry, and the nano-cellulose is added into the mixed slurry; after the nano-cellulose is added into the mixed slurry, the total concentration of the total fiber in the mixed slurry is 2-10%. In the second mode, the nano-cellulose is coated on the wet paper of the cellulose-based lithium battery diaphragm according to the proportion of 4-12 g of nano-cellulose per 100g of mixed slurry. As for the nano-cellulose pulp in which the length of the nano-cellulose fiber is 150 nm-6 μm and the width of the nano-cellulose fiber is 2nm-100nm, for example, before the second mixed pulp is made into a wet cellulose-based lithium battery separator paper sheet, the second mixed pulp needs to be diluted with water to the mass concentration of 1% -4% so as to fully disperse the fibers, and the equipment used for making the paper sheet is a sheet maker or a paper machine. Sequentially carrying out double-sided squeezing, drying and press polishing on the cellulose-based lithium battery diaphragm wet paper to obtain cellulose-based lithium battery diaphragm base paper; when double-sided pressing is carried out, the pressure used for pressing each side is 3MPa to 10MPa, and the pressing time of each side is 2min to 10 min; the temperature used for drying is 80-105 ℃, the time used for drying is 5-20 min, and the temperature used for calendaringThe temperature is 100-120 ℃, and the pressure used for calendaring is 2-5 MPa. And carrying out post-treatment on the cellulose-based lithium battery diaphragm wet paper to obtain cellulose-based lithium battery diaphragm base paper. The thickness of the cellulose-based lithium battery diaphragm base paper is 20-60 mu m, and the quantitative content is 20g/m2-50g/m2. The average void size inspection result in the physical property test of the cellulose-based lithium battery separator prepared by the method is 302 nm-473 nm.
Chinese patent document CN103545475A (application No. 201310518815.4) discloses a barium sulfate diaphragm for lithium ion batteries and a preparation method thereof, wherein the preparation method mainly comprises that the particle size of a barium sulfate medium coated on the surface layer of the battery diaphragm is 20 nm-300 nm. Mixing and stirring nano barium sulfate particles, a binder, a solvent and a dressing together, then coating the slurry on the front surface and the back surface of the lithium ion battery diaphragm to form a coating, and drying the coating to prepare the barium sulfate diaphragm; the lithium ion battery base diaphragm is a microporous diaphragm or a non-woven fabric diaphragm; the microporous diaphragm or the non-woven fabric diaphragm is made of one or more of PP, PE, polyvinyl alcohol, polyimide resin or polyethylene glycol terephthalate, the drying temperature is divided into four sections which are respectively 40-60 ℃, 60-80 ℃, 80-60 ℃ and 60-40 ℃, and the speed of the coating passing through the drying section is 5-59 meters per minute.
The battery emits heat during charge and discharge, and a large amount of heat is emitted particularly when short-circuiting or overcharging occurs. Therefore, when the temperature rises, the diaphragm should maintain the original integrity and a certain mechanical strength, continue to play a role in isolating the positive electrode and the negative electrode, and prevent the occurrence of short circuit, so the smaller the thermal shrinkage rate of the diaphragm is, the better the thermal stability is.
The air permeability of the lithium ion battery diaphragm is an important index of the diaphragm, and the better the air permeability is, the better the smoothness of lithium ions penetrating the diaphragm is, and the lower the resistance of the diaphragm is. It is determined comprehensively by the factors of the pore size and distribution of the membrane, the porosity, the shape of the pores, the tortuosity of the pores and the like. The aperture is generally required to be within the range of 10-100 nm, and when the aperture is less than 10nm, the lithium ion passing capacity is too small; the aperture is larger than 100nm, and the battery is easy to be short-circuited during the production of dendrite inside the battery.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the lithium battery diaphragm paper made of the wood pulp fiber/nano barium sulfate composite material and the preparation method thereof.
The lithium battery diaphragm paper made of the wood pulp fiber/nano barium sulfate composite material and the preparation method thereof have the advantages of moderate aperture, excellent wettability, good air permeability, high film strength, high thermal stability, environmental protection and no pollution.
The technical scheme of the invention is as follows:
a preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) the virgin wood pulp fiber pulp is subjected to disintegration and pulping to prepare high-pulping-degree fiber pulp, and the prepared fiber pulp is prepared into 25g/m quantitative pulp by adopting a paper preparation process2～35g/m2The fiber-based paper of (1);
the wood fiber is pulped to generate a large amount of fine fibers, fiber gaps are filled, tightness is improved, and the aperture between the fibers is reduced, so that the aperture range is 1-30 mu m.
(2) Uniformly mixing the nano-fiber and the nano-barium sulfate composite material according to a certain proportion to prepare a mixed coating, uniformly coating the mixed coating on two sides of the fiber base paper in the step (1), and performing hot-pressing drying to prepare a semi-finished lithium battery diaphragm paper;
the mixed coating prepared from the nanofiber and nano barium sulfate composite material has good pore filling property, thermal stability and wettability, and can reduce the pore diameter of the fiber-based paper to be less than 100 nm; by using a hot-pressing drying mode, the coating can be filled into the fiber-based paper under a certain pressure, so that the inner and outer apertures of the lithium battery diaphragm paper are uniform.
(3) And (3) dissolving the polyimide resin with a solvent to prepare a polyimide resin solution with the mass percentage concentration of 5-10%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 10-30 s, and drying to obtain the finished lithium battery separator paper.
Semi-manufactured goods lithium cell diaphragm paper soaks in polyimide resin solution, can make lithium cell diaphragm paper keep higher heat stability under the long-time high temperature condition, can increase the combination between fibre base paper and the coating layer simultaneously, improves lithium cell diaphragm paper's physical strength, prevents that nanometer barium sulfate combined material from droing in the fibre paper base in electrolyte.
According to the invention, the wood pulp fiber pulp obtained by the step (1) is bleached softwood fiber, bleached hardwood fiber and mixed fiber pulp obtained by mixing the two fibers in proportion, wherein the bleached softwood fiber, the bleached hardwood fiber and the mixed fiber pulp are prepared by a chemical method, a semi-chemical method or a chemical-mechanical method.
According to the invention, the beating mode in the step (1) is preferably a sticky beating mode, and the sticky beating mode has the function of mainly brooming fibers.
According to the invention, the beating degree of the wood pulp fiber pulp in the step (1) is preferably 70-90 DEG SR;
preferably, according to the present invention, the paper making process is a low basis weight high-tightness tissue paper making process.
Compared with lithium battery base films prepared by other methods, the lithium battery diaphragm fiber base paper prepared by the low-basis-weight high-tightness tissue paper preparation process is simple in method, mature in process and convenient for large-scale production.
According to the present invention, preferably, the nanofibers in step (2) are biomass nanofibers.
Further preferably, the biomass nanofibers comprise mechanically produced nanofibers and/or chemically produced nanofibers.
More preferably, the biomass nanofibers are softwood nanofibers, hardwood nanofibers and/or bacterial cellulose.
According to the invention, preferably, in the step (2), the nano-fiber is nano-sized, the diameter is 20-50 nm, and the length-diameter ratio is 30-100: 1.
according to the invention, in the step (2), the nano barium sulfate composite material has a particle diameter size of nano level and a diameter of 20 nm-60 nm.
According to the invention, the nano barium sulfate composite material in the step (2) is prepared by any one or more than two methods of a grinding and grinding method, a chemical precipitation method, a micro-emulsion method, a super-heavy method or a micro-reactor method.
According to the invention, the mass percent of the nano-fiber in the mixed coating in the step (2) is preferably 30-70%, and the mass percent of the nano barium sulfate composite material is preferably 30-70%.
According to the invention, the coating weight of the mixed coating in the step (2) is 15g/m2～20g/m2The coating method is any one of gravure coating, slot coating, dip coating, spray coating, and spin coating.
According to the invention, the hot-pressing drying in the step (2) is preferably a hot-pressing drying mode of a hot press.
More preferably, the hot pressing temperature is 100 ℃ to 130 ℃ and the hot pressing pressure is 3MPa to 5 MPa.
According to the invention, the polyimide resin in the step (3) is preferably a soluble polyimide resin, and the solvent used is one or a mixture of two of strong polar organic solvents DMA, DMF, NMP, dioxane, m-cresol and chloroform.
The invention discloses a wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper, which has the following physical and chemical indexes: the quantitative ratio is 40-60 g/m2The pore diameter is 30 nm-100nm, the porosity is 40% -80%, the puncture strength is 300-600 gf, the contact angle of wetting liquid is 20-60 degrees, and the thermal shrinkage is less than 3% at the temperature of 200-300 ℃.
Preferably: the thermal shrinkage rate of the lithium battery diaphragm paper is less than 1.2% at 200 ℃ and less than 3% at 300 ℃.
Advantageous effects
1. The aperture of the lithium battery diaphragm paper prepared by the invention is in the range of 30 nm-100nm, and the size is moderate; the wetting angle is 20-60 degrees, and the liquid absorption property is good; the heat shrinkage rate is less than 3 percent after 60 minutes at the temperature of 200-300 ℃, and the high-temperature-resistant material has good long-time high-temperature resistance. The problems of improper pore diameter, poor wettability, no high temperature resistance and the like in the current lithium battery diaphragm are solved. The paper is rich in raw material resources, environment-friendly and safe, the paper preparation process is adopted in the manufacturing method, the method is simple, the cost is low, and the industrialization is facilitated.
2. The invention selects the wood pulp fiber as the raw material, the wood pulp fiber resource is rich, the cost is low, the dispersion is easy in water, and the finished paper is uniform; the wood pulp fibers are subjected to high devillicate fibrillation after pulping treatment, and the fibers can be combined through hydrogen bonds to form a base paper structure with higher strength; the wood pulp fiber has high thermal stability and good wettability.
3. Selecting a nano-fiber and nano-barium sulfate composite material as a mixed coating. The nano-fiber is prepared from plant fiber, has all the characteristics of the plant fiber, and can be combined with fiber-based paper through hydrogen bonds as a coating; the nano barium sulfate composite material has good high-temperature stability but poor hydrophilicity, and the two nano materials are mixed, so that the coating has good surface binding property, and the wettability and the thermal stability of the lithium battery diaphragm are obviously improved; the mixed coating prepared from the nanofiber and nano barium sulfate composite material is coated on two sides of the fiber-based paper, and the coating can be filled in the fiber-based paper under pressure in a hot-pressing drying mode to reduce the pores among the fiber-based paper, so that the inner and outer pore diameters of the battery diaphragm are uniform, and the pore diameter range of the battery diaphragm is reached.
4. Polyimide resin is selected to impregnate the semi-finished lithium battery diaphragm paper, so that the long-time thermal stability of the paper can be improved, and the lithium battery can continue to work at high temperature; the polyimide resin plays a role of an adhesive, the physical strength of the lithium battery diaphragm paper is improved, and the mixed coating layer is prevented from falling off due to long-time soaking in electrolyte.
Detailed description of the invention
The technical solution of the present invention is further described with reference to the following examples, but the scope of the present invention is not limited thereto.
The bleached softwood pulp fibers or bleached hardwood pulp fibers described in the examples are all common commercial products.
The nanofibers described in the examples were softwood nanofibers prepared by the TEMPO Cellulose oxidation process described in the Determination of nanocellulose fibrous length by laser sensitivity measurement (Tanaka et al, Cellulose 6.2014).
The nano barium sulfate composite material described in the examples was prepared by a complex precipitation method described in "various methods for preparing nano barium sulfate and characterization research" (Liu Zhi et al, applied basic science and science bulletin "9 months 2001).
The paper production process described in the examples was carried out according to the paper production process described in "development of high-strength tissue paper" (Tuchangzhi et al, paper and paper manufacture 9 months 2005).
Example 1
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) uniformly mixing the crushed primary softwood pulp fibers accounting for 50% of the mass percentage with hardwood pulp accounting for 50% of the mass percentage, and performing high-viscosity pulping treatment to prepare mixed wood pulp fiber pulp with the pulping degree of 80 DEG SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Uniformly mixing 50% by mass of nano-fiber (the diameter is 30 +/-5 nm, the length-diameter ratio is 50 +/-5: 1) and 50% by mass of nano-barium sulfate composite material (the diameter is 30 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percent concentration of 8%, soaking the semi-finished lithium battery diaphragm paper obtained in the step (2) in the polyimide resin solution for 20s, and drying. And obtaining finished lithium battery diaphragm paper.
The physical index data of the lithium battery separator paper prepared in this example are shown in table 1:
TABLE 1
Example 2
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) carrying out high-viscosity pulping treatment on the disintegrated native softwood pulp fibers to prepare mixed wood pulp fiber pulp with the beating degree of 80-degree SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Uniformly mixing 50% by mass of nano-fiber (the diameter is 30 +/-5 nm, the length-diameter ratio is 50 +/-5: 1) and 50% by mass of nano-barium sulfate composite material (the diameter is 30 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percentage concentration of 8%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 20s, and drying to obtain the finished lithium battery separator paper.
The physical index data of the lithium battery separator paper prepared in this example are shown in table 2:
TABLE 2
Example 3
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) subjecting the disintegrated virgin hardwood pulp fibers to a high pressurePerforming sticky pulping treatment to obtain fiber pulp with the pulping degree of 80 DEG SR; the prepared fiber pulp is prepared into a paper with the basis weight of 30g/m by adopting a paper preparation process of high-tightness tissue paper2The fiber-based paper of (1).
(2) Uniformly mixing 50% by mass of nano-fiber (the diameter is 30 +/-5 nm, the length-diameter ratio is 50 +/-5: 1) and 50% by mass of nano-barium sulfate composite material (the diameter is 30 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percentage concentration of 8%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 20s, and drying to obtain the finished lithium battery separator paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 3:
TABLE 3
Example 4
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) uniformly mixing the crushed primary softwood pulp fibers accounting for 50% of the mass percentage with hardwood pulp accounting for 50% of the mass percentage, and performing high-viscosity pulping treatment to prepare mixed wood pulp fiber pulp with the pulping degree of 80 DEG SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Mixing 30% of nano-fiber (diameter of 30 +/-5 nm and length-diameter ratio of 50 +/-5: 1) by mass percent and 70% of nano-barium sulfate composite material (diameter of 30 +/-5 nm) by mass percentUniformly mixing, and coating the mixture on both sides of the fiber base paper in the step (1) at the coating weight of 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percentage concentration of 8%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 20s, and drying to obtain the finished lithium battery separator paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 4:
TABLE 4
Example 5
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) uniformly mixing the crushed primary softwood pulp fibers accounting for 50% of the mass percentage with hardwood pulp accounting for 50% of the mass percentage, and performing high-viscosity pulping treatment to prepare mixed wood pulp fiber pulp with the pulping degree of 80 DEG SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Uniformly mixing 70% by mass of nano-fiber (the diameter is 30 +/-5 nm, the length-diameter ratio is 50 +/-5: 1) and 30% by mass of nano-barium sulfate composite material (the diameter is 30 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percentage concentration of 8%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 20s, and drying to obtain the finished lithium battery separator paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 5:
TABLE 5
Example 6
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) uniformly mixing the crushed primary softwood pulp fibers accounting for 50% of the mass percentage with hardwood pulp accounting for 50% of the mass percentage, and performing high-viscosity pulping treatment to prepare mixed wood pulp fiber pulp with the pulping degree of 80 DEG SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Uniformly mixing 50% by mass of nano-fiber (the diameter is 25 +/-5 nm, the length-diameter ratio is 95 +/-5: 1) and 50% by mass of nano-barium sulfate composite material (the diameter is 30 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percent concentration of 8%, soaking the semi-finished lithium battery diaphragm paper obtained in the step (2) in the polyimide resin solution for 20s, and drying. And obtaining finished lithium battery diaphragm paper.
The physical index data of the lithium battery separator paper prepared in this example are shown in table 6:
TABLE 6
Example 7
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) uniformly mixing the crushed primary softwood pulp fibers accounting for 50% of the mass percentage with hardwood pulp accounting for 50% of the mass percentage, and performing high-viscosity pulping treatment to prepare mixed wood pulp fiber pulp with the pulping degree of 80 DEG SR; paper making process using high-tightness tissue paper to prepare paper with basis weight of 30g/m2The fiber-based paper of (1).
(2) Uniformly mixing 50% by mass of nano-fiber (the diameter is 30 +/-5 nm, the length-diameter ratio is 50 +/-5: 1) and 50% by mass of nano-barium sulfate composite material (the diameter is 60 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 18g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 120 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin with a dioxane solvent to prepare a polyimide resin solution with the mass percent concentration of 8%, soaking the semi-finished lithium battery diaphragm paper obtained in the step (2) in the polyimide resin solution for 20s, and drying. And obtaining finished lithium battery diaphragm paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 7:
TABLE 7
Example 8
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) carrying out high-viscosity pulping treatment on the disintegrated native softwood pulp fibers to prepare mixed wood pulp fiber pulp with the pulping degree of 70-degree SR; prepared by adopting a paper preparation process to obtain the paper with the quantitative content of 25g/m2The fiber-based paper of (1).
(2) Uniformly mixing 30% by mass of nano-fibers (the diameter is 25 +/-5 nm, the length-diameter ratio is 35 +/-5: 1) and 70% by mass of nano-barium sulfate composite material (the diameter is 25 +/-5 nm), coating the mixture on two sides of the fiber base paper in the step (1), wherein the coating weight is 15g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 100 ℃ and the pressure is 3MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) Dissolving polyimide resin in a m-cresol solvent), preparing a polyimide resin solution with the mass percentage concentration of 5%, soaking the semi-finished lithium battery diaphragm paper obtained in the step (2) in the polyimide resin solution for 10s, and drying to obtain the finished lithium battery diaphragm paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 8:
TABLE 8
Example 9
A preparation method of wood pulp fiber/nano barium sulfate composite material lithium battery diaphragm paper comprises the following steps:
(1) carrying out high-viscosity pulping treatment on the disintegrated native softwood pulp fibers to prepare mixed wood pulp fiber pulp with the pulping degree of 90 DEG SR; prepared by adopting a paper preparation process to have the quantitative content of 35g/m2The fiber-based paper of (1).
(2) 70 percent of nano-fiber (diameter is 45 plus or minus 5nm, length-diameter ratio is 90 plus or minus 5: 1) and 30 percent of nano barium sulfate composite material (diameter is 45 plus or minus 5: 1) by mass percentage55 +/-5 nm), coating the mixture on both sides of the fiber base paper in the step (1) with the coating weight of 20g/m2And hot-pressing and drying by a hot press under the conditions that the temperature is 130 ℃ and the pressure is 5MPa to obtain the semi-finished lithium battery diaphragm paper.
(3) And (3) dissolving the polyimide resin by using a DMA (direct memory access) solvent to prepare a polyimide resin solution with the mass percentage concentration of 10%, soaking the semi-finished lithium battery diaphragm paper obtained in the step (2) in the polyimide resin solution for 10s, and drying to obtain the finished lithium battery diaphragm paper.
The physical indexes of the lithium battery separator paper prepared in this example are shown in table 9:
TABLE 9
Comparative example 1
Compared with the example 1, the difference is that the coating in the step (2) only contains the nano cellulose and does not contain the nano barium sulfate composite material, and the rest is the same.
The physical indexes of the lithium battery separator paper prepared by the comparative example are shown in table 10:
watch 10
Analysis of results
In comparative example 1, the average pore size of the lithium battery separator paper was significantly increased beyond the range of the average pore size of the lithium battery separator paper by using only nanofibers without using the nano barium sulfate composite material; but the wettability is improved, the puncture strength is improved, but the thermal shrinkage rate is improved, and the indexes of the invention are exceeded at the temperature of 200 ℃ and 300 ℃. The effect of the nanofibers on increasing porosity, improving wettability and puncture strength is proved. However, the pore diameter is too large, and the thermal stability is low.
Comparative example 2
Compared with the example 1, the difference is that the coating in the step (2) only contains the nano barium sulfate composite material and does not contain the nano fiber, and the rest is the same.
The physical index data of the lithium battery separator paper prepared by the comparative example are shown in Table 11:
TABLE 11
Analysis of results
In comparative example 2, only the nano barium sulfate composite material is used without using the nano fiber, the porosity and the average pore diameter are obviously reduced, the thermal stability is improved, but the wetting property is poor, the contact angle reaches 82 degrees and exceeds the range standard, the nano barium sulfate composite material is proved to have the effects of reducing the porosity and the pore diameter and improving the thermal stability, but the nano barium sulfate composite material has the defect of hydrophobicity and can reduce the wettability and the puncture strength.
Comparative example 3
Compared with the example 1, the difference is that the drying mode after the mixed coating is coated in the step (3) is normal pressure drying at 120 ℃, and the rest is the same.
The physical index data of the lithium battery separator paper prepared by the comparative example are shown in Table 12:
TABLE 12
Analysis of results
In comparative example 3, normal pressure drying at 120 ℃ is adopted, so that the porosity is high, the average pore diameter is large, the wettability is improved, the puncture strength is reduced, and the thermal stability is reduced.
Comparative example 4
Except that the polyimide resin solution was not impregnated, lithium battery separator paper was prepared, as compared with example 1, and the other steps were the same.
The physical index data of the lithium battery separator paper prepared by the comparative example are shown in Table 13:
watch 13
Analysis of results
In comparative example 4, the penetration strength was significantly reduced without impregnation with polyimide resin, and the thermal stability was significantly reduced at a high temperature of 300 ℃, demonstrating that polyimide resin plays a role of an adhesive in separator paper and a role of improving high-temperature stability.
Conclusion
Embodiment 1 is that lithium battery diaphragm paper prepared by the comparatively optimized scheme of the invention, its each performance is comparatively balanced, the comprehensive properties are better, wherein porosity and average pore diameter are the most moderate, each index such as wetting property, puncture strength, thermal shrinkage factor can be compatible each other, make three most important indexes of pore diameter, wettability, thermal stability of this lithium battery diaphragm paper reach the optimum.
Example 2 the same as example 1 except for using softwood pulp fibers as a raw material. The softwood pulp fibers have larger diameters, and the pores among the fibers are larger after the paper is formed, so that the prepared lithium battery diaphragm has larger porosity and average pore diameter, but has good wetting property, high puncture strength and reduced heat shrinkage.
Example 3 hardwood pulp fibers were used as the starting material and the other items were the same as in example 1. The hardwood pulp fibers have small diameter, and the pores among the fibers are narrow after paper forming, so that the prepared lithium battery diaphragm has low porosity and average pore diameter, good thermal stability, but low wettability and puncture strength.
Example 4 is a mixture of 30% by mass of nanofibers and 70% by mass of a nano barium sulfate composite in a nano coating, and the other items are the same as those in example 1. The prepared lithium battery diaphragm paper has the advantages of reduced wettability, reduced puncture strength, improved thermal stability and lower porosity and average pore diameter.
Example 5 is a mixture of 70% by mass of nanofibers and 30% by mass of a nano barium sulfate composite in a nano coating, and the other items are the same as those in example 1. The prepared lithium battery diaphragm paper has the advantages of improved wettability, improved puncture strength, increased porosity and average pore diameter, and reduced thermal stability.
The data difference between example 4 and example 5 proves that the nano-fiber is mainly used for improving the wettability and the puncture strength of the lithium battery diaphragm paper, and the nano barium sulfate composite material is mainly used for improving the porosity, the average pore diameter and the thermal stability of the lithium battery diaphragm.
Example 6 nanofibers with a diameter of 25 + -5 nm and an aspect ratio of 95 + -5 nm were selected, all things remaining the same as in example 1. The porosity is reduced, the average pore diameter is reduced, the puncture strength is increased, and other indexes are not obviously changed, so that the diameters and the major diameters of the nano fibers have influences on the porosity, the average pore diameter and the puncture strength of the lithium battery diaphragm paper.
Example 7 is a nano barium sulfate composite material with a diameter of 60 +/-5 nm, and the rest is the same as example 1. The porosity is improved, the average pore diameter is improved, and other indexes are not obviously changed, so that the nano barium sulfate diameter has influence on the porosity and the average pore diameter of the lithium battery diaphragm paper.
Examples 8 and 9 are two lithium battery separator papers prepared by using the end value data of the present invention as a scheme, and each index of the two lithium battery separator papers meets the index requirements of the present invention technology, but each index is higher or lower, and both indexes cannot achieve a reasonable consideration.
The results of comparative examples 1, 2, 3, 4 and example 1 are analyzed after the table of comparative examples and are not repeated.
Comprehensive analysis shows that the technical scheme of the invention is that the lithium battery diaphragm paper prepared by taking the plant fiber as the base paper, taking the nano fiber and nano barium sulfate composite material as the coating to coat on two sides of the base paper and then soaking in the polyimide resin solution has moderate porosity, reasonable pore size, excellent wettability and thermal stability, mature process, simple operation and low cost, and is suitable for large-scale production. The raw materials are mainly natural materials, so that the environment-friendly energy-saving environment-friendly.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and any other changes, modifications, combinations, substitutions and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents and are included in the scope of the present invention.
Claims (10)
1. The preparation method of the lithium battery separator paper is characterized by comprising the following steps:
(1) the virgin wood pulp fiber pulp is subjected to disintegration and pulping to prepare high-pulping-degree fiber pulp, and the prepared fiber pulp is prepared into 25g/m quantitative pulp by adopting a paper preparation process2～35g/m2The fiber-based paper of (1);
(2) uniformly mixing the nano-fiber and the nano-barium sulfate composite material according to a certain proportion to prepare a mixed coating, uniformly coating the mixed coating on two sides of the fiber base paper in the step (1), and performing hot-pressing drying to prepare a semi-finished lithium battery diaphragm paper;
(3) and (3) dissolving the polyimide resin with a solvent to prepare a polyimide resin solution with the mass percentage concentration of 5-10%, soaking the semi-finished lithium battery separator paper obtained in the step (2) in the polyimide resin solution for 10-30 s, and drying to obtain the finished lithium battery separator paper.
2. The method for preparing lithium battery separator paper according to claim 1, wherein the wood pulp fiber slurry in the step (1) is bleached softwood fiber, bleached hardwood fiber, or a mixed fiber slurry of two fibers mixed in proportion, which are prepared by a chemical method, a semi-chemical method, or a chemical-mechanical method;
preferably, the pulping mode in the step (1) is a sticky pulping mode;
further preferably, the beating degree of the wood pulp fiber slurry in the step (1) is 70-90 DEG SR;
more preferably, the paper making process in the step (1) is a low basis weight high-tightness tissue paper making process.
3. The method for preparing lithium battery separator paper according to claim 1, wherein the nanofibers in step (2) are biomass nanofibers;
preferably, the biomass nanofibers comprise mechanically made nanofibers and/or chemically made nanofibers;
more preferably, the biomass nanofibers are softwood nanofibers, hardwood nanofibers and/or bacterial cellulose.
4. The preparation method of the lithium battery separator paper as claimed in claim 1, wherein in the step (2), the nano-fiber has a nano-scale size, a diameter of 20 to 50nm, an aspect ratio of 30 to 100: 1.
5. the method for preparing lithium battery separator paper as claimed in claim 1, wherein in the step (2), the nano barium sulfate composite material has a particle diameter size of nano level and a diameter of 20nm to 60 nm;
preferably, the nano barium sulfate composite material is prepared by any one or more than two methods of a grinding and grinding method, a chemical precipitation method, a micro-emulsion method, a super-heavy method or a micro-reactor method.
6. The method for preparing lithium battery separator paper as claimed in claim 1, wherein the mass percentage of the nano-fibers of the mixed coating in the step (2) is 30-70%, and the mass percentage of the nano-barium sulfate composite material is 30-70%.
7. The lithium battery of claim 1The preparation method of the pond diaphragm paper is characterized in that the coating weight of the mixed coating in the step (2) is 15g/m2～20g/m2The coating method is any one of gravure coating, slot coating, dip coating, spray coating, and spin coating.
8. The method for preparing lithium battery separator paper according to claim 1, wherein the hot-pressing drying in the step (2) is a hot-pressing drying mode of a hot press;
preferably, the hot pressing temperature is 100-130 ℃, and the hot pressing pressure is 3-5 MPa.
9. The method for preparing lithium battery separator paper according to claim 1, wherein the polyimide resin in step (3) is a soluble polyimide resin, and the solvent used is one or a mixture of two of strongly polar organic solvents DMA, DMF, NMP, dioxane, m-cresol, and chloroform.
10. The lithium battery separator paper prepared according to any one of claims 1 to 9, wherein the physical and chemical properties of the lithium battery separator paper are as follows: the quantitative ratio is 40-60 g/m2The pore diameter is 30 nm-100nm, the porosity is 40% -80%, the puncture strength is 300-600 gf, the contact angle of wetting liquid is 20-60 degrees, and the thermal shrinkage is less than 3% at the temperature of 200-300 ℃;
preferably, the heat shrinkage rate is less than 1.2% at 200 ℃ and less than 3% at 300 ℃.
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Application publication date: 20200103 |