阅读说明：本技术 一种锂电池隔板 (Lithium battery separator ) 是由 邱长泉 胡君 陈永乐 单华靖 虞少波 程跃 于 2021-07-20 设计创作，主要内容包括：本发明公开一种锂电池隔板,包括改性多孔基膜和设置在所述改性多孔基膜至少一表面的功能层；所述改性多孔基膜包含基膜主体和锂导离子化合物颗粒层,所述基膜主体的至少一表面为经过电晕预处理改性过的,所述锂导离子化合物颗粒层设置在基膜主体的经过电晕预处理改性过的至少一表面；所述功能层含有有机物且设置在锂导离子化合物颗粒层。本发明尚公开通过sol-gel-水热法制备含锂导离子化合物,将含锂导离子化合物的小粒径颗粒嵌于基膜主体的改性表面,从而解决现有隔膜离子电导率差、浸润性较差的缺点,同时涂覆的功能层使得锂电池隔板具有良好的粘接性和耐热性。(The invention discloses a lithium battery separator, which comprises a modified porous base membrane and a functional layer arranged on at least one surface of the modified porous base membrane; the modified porous base membrane comprises a base membrane main body and a lithium ion conducting compound particle layer, wherein at least one surface of the base membrane main body is modified through corona pretreatment, and the lithium ion conducting compound particle layer is arranged on at least one surface of the base membrane main body, which is modified through corona pretreatment; the functional layer contains an organic substance and is provided on the lithium ion conductive compound particle layer. The invention further discloses a method for preparing the lithium-containing ion conducting compound by a sol-gel-hydrothermal method, and small-particle-size particles of the lithium-containing ion conducting compound are embedded in the modified surface of the base film main body, so that the defects of poor ionic conductivity and poor wettability of the existing diaphragm are overcome, and meanwhile, the lithium battery separator has good adhesion and heat resistance due to the coated functional layer.)

1. A lithium battery separator characterized by:

the functional layer is arranged on at least one surface of the modified porous base membrane; the modified porous base membrane comprises a base membrane main body and a lithium ion conducting compound particle layer, wherein at least one surface of the base membrane main body is modified through corona pretreatment, and the lithium ion conducting compound particle layer is arranged on at least one surface of the base membrane main body, which is modified through corona pretreatment; the functional layer contains organic matters and is arranged on the lithium ion conducting compound particle layer;

the preparation method of the lithium battery separator comprises the following steps:

s1, performing corona pretreatment on the porous base membrane main body to modify the surface of the porous base membrane main body, passing through a saturated aqueous solution water tank containing a lithium ion conducting compound, drying the porous base membrane main body after passing through water, and embedding lithium ion conducting compound particles on the modified surface of the base membrane main body to form a lithium ion conducting compound particle layer, thereby obtaining a modified porous base membrane;

s2, mechanically stirring, mixing and dissolving the organic matter and the organic solvent in proportion to obtain slurry;

and S3, coating the slurry on at least one side surface of the modified porous base membrane, and enabling a functional layer to be formed on the lithium ion conducting compound particle layer of the modified porous base membrane.

2. The lithium battery separator as claimed in claim 1, wherein: the lithium battery separator has TD thermal shrinkage of 0.1-0.7%, MD thermal shrinkage of 0.1-0.5%, interfacial adhesion of 15-25N/m, TD wetting distance of 3.0-5.5 cm, MD wetting distance of 3.5-6.0 cm, and ionic conductivity of 2.0 × 10^-3～4.0×10^-3s/cm。

3. The lithium battery separator as claimed in claim 2, wherein: the speed of the saturated aqueous solution water tank containing the lithium ion conducting compound is 3-8 m/min, and the power of the corona pretreatment is 1.5-3.5 kW.

4. The lithium battery separator as claimed in claim 1, wherein: the lithium ion-conducting compound comprises LiAlSi₂O₆、Li₂FeSiO₄Or LiFePO₄。

5. The lithium battery separator as claimed in claim 1, wherein: the functional layer further contains inorganic substances; in the functional layer, the weight parts of the organic matter are 5 to 80 parts, and the weight parts of the inorganic matter are 3 to 40 parts.

6. The lithium battery separator as claimed in claim 5, wherein: the obtained slurry further comprises the steps of mechanically stirring and uniformly mixing the inorganic substance and the organic solvent according to a proportion, and mechanically stirring and mixing the completely dissolved organic substance solution and the uniformly mixed inorganic substance solution to obtain the slurry; in the slurry, the weight parts of organic matters are 5-80 parts, the weight parts of organic solvents are 50-100 parts, and the weight parts of inorganic matters are 3-40 parts.

7. The separator for an electrochemical device according to claim 1, wherein: in the slurry, the weight part of the organic matter is 5-80 parts, and the weight part of the organic solvent is 50-100 parts.

8. The lithium battery separator as claimed in claim 1, wherein: the organic solvent comprises a combination of one or more of N-methyl pyrrolidone (NMP), Dimethylacetamide (DMAC), acetone, N-Dimethylformamide (DMF), Dimethylsulfoxide (DMSO).

9. The lithium battery separator as claimed in claim 1, wherein: the organic matter is polyvinylidene fluoride, and the molecular weight of the organic matter is 10-100 ten thousand; in the slurry, the solid content of polyvinylidene fluoride is 5-20 wt%.

10. The lithium battery separator as claimed in claim 5, wherein: the inorganic substance includes aluminum trioxide, boehmite, silica, titanium dioxide, barium sulfate, calcium carbonate, or calcium oxide.

Technical Field

The invention relates to the technical field related to lithium ion batteries, in particular to a lithium battery separator.

Background

As a new type of secondary battery, and a renewable energy source, the lithium ion battery has advantages of high working voltage, light weight, and high energy density, and is widely used in the fields of electric tools, digital cameras, mobile phones, notebook computers, and the like, and shows a strong development trend.

The diaphragm is used as one of key components of the lithium ion battery, is used for isolating the positive electrode and the negative electrode of the battery, prevents the positive electrode and the negative electrode from being in direct contact with each other to cause short circuit, and simultaneously requires good lithium ion permeability, and closes an ion channel when the temperature of the battery is too high during operation so as to ensure the safety of the battery. Therefore, the separator plays an important role in the safety of the lithium ion battery.

The lithium ion conductor has the characteristics of high conductivity, low activation energy, most negative electrode potential and the like. More highly studied Li with layered structure₃N, Lisicon (Li) of skeletal structure₁₄ZnGeO₄) And with LiTi₂P₃O₁₂Solid solutions of the radicals, and the like. However, the inorganic lithium ion conductor has no practical value due to different conductivity, low decomposition voltage, metal lithium corrosion resistance and the like. Later discovered polymers (e.g., polyoxyethylene) and alkali metal salts (e.g., LiCF)₃SO₃) Although the conductivity of the organic lithium ion conductor such as the complex is lower than that of the inorganic lithium ion conductor, the organic lithium ion conductor is easy to process into a film, makes up the defect of insufficient conductivity, has good viscoelasticity, and is widely used as a diaphragm material of a high-energy lithium battery to manufacture a high-specific-energy and high-capacity battery and a high-temperature fuel battery.

At present, diaphragms widely applied to lithium batteries are mainly polyolefin melt-drawn diaphragms, and the shutdown effect of the materials is beneficial to improving the safety when the batteries generate heat. However, the traditional commercial PE/PP diaphragm has poor wettability to electrolyte, poor liquid retention, low ionic conductivity and serious thermal shrinkage. These problems affect the processing, cycling and rate performance of the battery and safety at high temperatures. The ceramic slurry coating of the polymer diaphragm is used for improving the heat resistance and mechanical property of the diaphragm, and the safety of the diaphragm is improved, so that the application and research of the diaphragm are wide. However, there is no mention of improving the permeability to lithium ions by modifying the base film, and therefore, there is a need in the art for a lithium battery separator having improved battery safety and better ionic conductivity.

Disclosure of Invention

In view of the above, the present invention is intended to provide a lithium battery separator, which solves the disadvantages of poor ionic conductivity and poor wettability of the existing separator, and at the same time, enables the separator to have good adhesion and heat resistance.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the invention provides a lithium battery separator, which comprises a modified porous base membrane and a functional layer arranged on at least one surface of the modified porous base membrane; the modified porous base membrane comprises a base membrane main body and a lithium ion conducting compound particle layer, wherein at least one surface of the base membrane main body is modified through corona pretreatment, and the lithium ion conducting compound particle layer is arranged on at least one surface of the base membrane main body, which is modified through corona pretreatment; the functional layer contains an organic substance and is provided on the lithium ion conductive compound particle layer.

Preferably, the lithium battery separator has a TD thermal shrinkage of 0.1 to 0.7% and an MD thermal shrinkage of 0.1 to 0.5%.

Preferably, the interface bonding of the lithium battery separator is 15-25N/m.

Preferably, the TD wetting distance of the lithium battery separator is 3.0-5.5 cm, and the MD wetting distance is 3.5-6.0 cm.

Preferably, the lithium battery separator has an ionic conductivity of 2.0 × 10^-3～4.0×10^-3s/cm。

Preferably, the functional layer further contains an inorganic substance.

Preferably, in the functional layer, the weight part of the organic matter is 5 to 80 parts, and the weight part of the inorganic matter is 3 to 40 parts.

Preferably, the lithium ion-conducting compound comprises LiAlSi₂O₆、Li₂FeSiO₄Or LiFePO₄。

Preferably, the particle size of the lithium ion-conducting compound particles is 5 to 20 nm.

Preferably, the particle size of the lithium ion-conducting compound particles is 10 to 20 nm.

Preferably, the organic matter is polyvinylidene fluoride, and the molecular weight is 10-100 ten thousand.

Preferably, the inorganic substance comprises aluminum trioxide, boehmite, silica, titanium dioxide, barium sulfate, calcium carbonate, or calcium oxide.

The invention also provides a method for preparing the modified porous base membrane by a sol-gel-hydrothermal method, which comprises the following steps: the method comprises the steps of modifying the surface of an unmodified porous base membrane body through corona pretreatment, then drying through a saturated aqueous solution water tank containing a lithium ion conducting compound after water is passed through the saturated aqueous solution water tank, so that lithium ion conducting compound particles are embedded in the modified surface of the base membrane body to form a lithium ion conducting compound particle layer, and thus obtaining the modified base membrane.

The invention also provides a method for preparing the lithium battery separator, which comprises the following steps:

s1, performing corona pretreatment on the porous base membrane main body to modify the surface of the porous base membrane main body, passing through a saturated aqueous solution water tank containing a lithium ion conducting compound, drying the porous base membrane main body after passing through water, and embedding lithium ion conducting compound particles on the modified surface of the base membrane main body to form a lithium ion conducting compound particle layer, thereby obtaining a modified porous base membrane;

s2, mechanically stirring, mixing and dissolving the organic matter and the organic solvent in proportion to obtain slurry;

and S3, coating the slurry on at least one side surface of the modified porous base membrane, and enabling a functional layer to be formed on the lithium ion-conducting compound particle layer of the modified porous base membrane.

Preferably, the step of obtaining the slurry further comprises mechanically stirring and mixing the inorganic substance and the organic solvent uniformly in proportion, and then mechanically stirring and mixing the completely dissolved organic substance solution and the uniformly mixed inorganic substance solution to obtain the slurry.

Preferably, the speed of the saturated aqueous solution water tank containing the lithium ion conducting compound is 3-8 m/min.

Preferably, the speed of the saturated aqueous solution water tank containing the lithium ion conducting compound is 5 m/min.

Preferably, the power of the corona pretreatment is 1.5-3.5 kW.

Preferably, the power of the corona pre-treatment is 2.5 kW.

Preferably, the organic solvent comprises a combination of one or more of N-methylpyrrolidone (NMP), Dimethylacetamide (DMAC), acetone, N-Dimethylformamide (DMF), Dimethylsulfoxide (DMSO).

Preferably, in the slurry, the weight part of the organic matter is 5 to 80 parts, and the weight part of the organic solvent is 50 to 100 parts.

Preferably, in the slurry, the weight parts of the organic matter are 5 to 80 parts, the weight parts of the inorganic matter are 3 to 40 parts, and the weight parts of the organic solvent are 50 to 100 parts.

Preferably, the organic matter is polyvinylidene fluoride, and the molecular weight of the organic matter is 10-100 ten thousand; in the slurry containing the organic matters and the inorganic matters, the solid content of the polyvinylidene fluoride is 5-20 wt%.

The invention has the following beneficial effects:

1) the invention provides a lithium battery separator and a preparation method thereof.A sol-gel-hydrothermal method is adopted to embed small-particle-size particles of a lithium ion conducting compound on a modified surface of a base film main body, so that the ionic conductivity of a separator is greatly improved, the internal resistance of an electrochemical device using the separator is greatly reduced, the cycle performance of the electrochemical device is greatly improved, and the separator shows excellent electrochemical performance;

2) the invention provides a lithium battery separator and a preparation method thereof, the wettability of a diaphragm is also obviously improved through the configuration of a modified base film, and the diaphragm shows excellent physical and chemical properties;

3) the invention provides a lithium battery separator and a preparation method thereof, wherein slurry containing organic matters is coated on one side or two sides of a modified base film, so that the heat shrinkage rate of a diaphragm is reduced, the adhesion is enhanced, the defect of poor wettability of the diaphragm is overcome, and the diaphragm shows excellent thermal properties and physical and chemical properties;

4) the invention provides a lithium battery separator and a preparation method thereof.A lithium ion conducting compound particle layer is formed by embedding lithium ion conducting compound particles on the modified surface of a base film main body through a saturated aqueous solution water tank containing a lithium ion conducting compound after the surface of the base film main body is subjected to corona pretreatment, so that unpredictable synergistic improvement effects are generated on the high ionic conductivity, high wettability and the like of a separator.

Drawings

FIG. 1 is a method of making a lithium battery separator structure according to the present invention;

FIG. 2 is a schematic diagram of a lithium battery separator according to some embodiments of the invention;

fig. 3 is a schematic structural diagram of a lithium battery separator according to another embodiment of the present invention.

Description of component reference numerals

1 … base film body

11 … modified surface

2 … lithium-ion-conducting Compound particle layer

3 … modified base film

4 … functional layer

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The embodiment of the invention provides a lithium battery separator, which comprises a modified porous base membrane 3 and a functional layer 4 arranged on at least one surface of the modified porous base membrane 3; the modified porous base membrane 3 comprises a base membrane main body 1 and a lithium ion conducting compound particle layer 2, wherein at least one surface 11 of the base membrane main body 1 is modified through corona pretreatment, and the lithium ion conducting compound particle layer 2 is arranged on at least one surface 11 of the base membrane main body 1 modified through corona pretreatment; the functional layer 4 contains an organic material and is provided on the lithium ion conductive compound particle layer 2.

Specifically, the TD thermal shrinkage of the lithium battery separator is 0.1-0.7%, and the MD thermal shrinkage is 0.1-0.5%.

Specifically, the interface bonding of the lithium battery separator is 15-25N/m.

Specifically, the TD wetting distance of the lithium battery separator is 3.0-5.5 cm, and the MD wetting distance is 3.5-6.0 cm.

Specifically, the lithium battery separator has an ionic conductivity of 2.0 × 10^-3～4.0×10^-3s/cm。

Specifically, the base film body is a PE base film, which may be various base films suitable for preparing a lithium ion battery separator in the art, for example, a linear low density polyethylene base film in general.

Specifically, the thickness of the base film main body is 10-15 μm.

Specifically, the lithium ion-conducting compound includes LiAlSi₂O₆、Li₂FeSiO₄Or LiFePO₄。

Specifically, the particle size of the lithium ion-conducting compound particles is 5-20 nm.

Specifically, the particle size of the lithium ion-conducting compound particles is 10-20 nm.

Specifically, the functional layer further contains an inorganic substance.

Specifically, in the functional layer, the weight parts of the organic matter are 5 to 80 parts, and the weight parts of the inorganic matter are 3 to 40 parts.

Specifically, the organic matter is polyvinylidene fluoride, and the molecular weight of the organic matter is 10-100 ten thousand.

Specifically, the inorganic substance includes aluminum trioxide, boehmite, silica, titanium dioxide, barium sulfate, calcium carbonate, or calcium oxide.

Specifically, the thickness of the modified base film is 5-25 μm, and the thickness of the functional layer is 1-4 μm.

The specific embodiment of the invention also provides slurry for preparing the functional layer of the lithium battery separator, which comprises the following components in parts by weight: 5-80 parts of organic matters; and 50-100 parts of an organic solvent.

Specifically, the organic matter is polyvinylidene fluoride, the molecular weight of the organic matter is 10-100 ten thousand, and the solid content of the organic matter is 5-20 wt%.

Specifically, the organic solvent is selected from one or more of NMP, DMAC, acetone, DMF and DMSO.

Specifically, the slurry comprises the following components in parts by weight: 3 to 40 portions of inorganic matter.

Specifically, the inorganic substance includes aluminum trioxide, boehmite, silica, titanium dioxide, barium sulfate, calcium carbonate, or calcium oxide.

The specific implementation mode of the invention also provides a method for preparing the lithium fast ion nano conductor by a sol-gel-hydrothermal method and combining the lithium fast ion nano conductor with the porous base membrane main body, and the specific implementation method comprises the following steps: and (2) performing corona pretreatment on an unmodified porous base membrane main body to modify the surface of the porous base membrane main body, soaking the porous base membrane main body in a solution containing nano lithium conductive ions, and after the base membrane main body is completely soaked by the solution, performing drying treatment by using an oven to obtain a modified base membrane 3 in which a small-particle-size lithium conductive ion compound is embedded in the modified surface of the base membrane main body.

The embodiment of the present invention also provides a method for preparing the above lithium battery separator, which comprises the steps of:

s1, obtaining a modified porous base membrane:

after the surface 11 of the porous base membrane main body 1 is modified by corona pretreatment, drying the porous base membrane main body by a drying oven through a saturated aqueous solution water tank containing a lithium ion conducting compound after water is passed through, so that lithium ion conducting compound particles are embedded in the modified surface 11 of the base membrane main body 1 to form a lithium ion conducting compound particle layer 2, thereby obtaining a modified porous base membrane 3;

s2, obtaining slurry:

mechanically stirring, mixing and dissolving an organic matter and an organic solvent in proportion to obtain slurry;

s3, forming a functional layer:

the above slurry is coated on at least one side surface of the modified porous base film 3 so that the functional layer 4 is formed on the lithium ion-conducting compound particle layer 2 of the modified porous base film 3.

Specifically, the speed (namely the speed of completely soaking and then leaving) of the saturated aqueous solution water tank containing the lithium ion conducting compound is 3-8 m/min.

Specifically, the speed of the saturated aqueous solution water tank containing the lithium ion conducting compound is 5 m/min.

Generally speaking, the speed of the saturated aqueous solution water tank containing the lithium ion conducting compound is too fast, the time of the saturated aqueous solution water tank containing the lithium ion conducting compound is not enough, and the lithium ion conducting compound has less embedded particles; on the contrary, the passing speed is too slow, the embedded layer of the lithium ion conducting compound particles is thicker, and the ionic conductivity of the coating film is slightly influenced.

Specifically, the power of corona pretreatment is 1.5-3.5 kW.

Specifically, the power of the corona pre-treatment was 2.5 kW.

Generally, too high or too low a power leads to undesirable increases in wettability and ionic conductivity of the final lithium battery separator product. Different corona powers have influence on subsequent coating effects, the corona power is too low (less than 1.5kW), the surface modification of the base film main body is not obvious, and lithium ion conducting compound particles cannot be embedded on the surface of the base film main body to form a lithium ion conducting compound particle layer; and the too high corona power (more than 3.5kW) can damage the base film, so that the subsequent coating is leaked, the performance of the coating film is influenced, and even the test data of the base film main body without corona is not good.

Specifically, the step of obtaining the slurry further comprises the step of mechanically stirring and uniformly mixing the inorganic substance and the organic solvent in proportion, and then mechanically stirring and mixing the completely dissolved organic substance solution and the uniformly mixed inorganic substance solution to obtain the slurry.

Specifically, the slurry is applied to one surface of the modified porous base film.

Specifically, the slurry is coated on both side surfaces of the modified porous base film.

Specifically, the coating is obtained by coating, rinsing and drying the slurry. The step of rinsing is a method of coating the base film by coating the base film and then passing the base film through a water tank, extracting the solvent in the slurry by water in the water tank, and then curing the slurry on the base film to form the coating.

Specifically, the drying temperature is 50-60 ℃.

The specific embodiment of the invention also provides the lithium ion battery diaphragm prepared by the method.

In addition, the specific embodiment of the invention also provides a lithium ion battery, which comprises a positive electrode, a negative electrode, an electrolyte and a diaphragm, wherein the diaphragm is the lithium battery separator.

The electrolyte is well known to those skilled in the art and generally consists of an electrolyte lithium salt and an organic solvent. The lithium salt of the electrolyte is a dissociable lithium salt, and may be selected from lithium hexafluorophosphate (LiPF), for example₆) Lithium perchlorate (LiClO)₄) Lithium tetrafluoroborate (LiBF)₄) And the like, the organic solvent may be at least one selected from Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC), Vinylene Carbonate (VC), and the like.

The positive electrode is prepared by mixing a positive electrode material for the lithium ion battery, a conductive agent and a binder into slurry and coating the slurry on an aluminum foil. The positive electrode material used includes any material that can be used in lithium ionCathode material of cell, e.g. lithium cobalt oxide (LiCoO)₂) Lithium nickel oxide (LiNiO)₂) Lithium manganese oxide (LiMn)₂O₄) Lithium iron phosphate (LiFePO)₄) And the like.

The negative electrode is prepared by mixing a negative electrode material for the lithium ion battery, a conductive agent and a binder into slurry and coating the slurry on a copper foil. The negative electrode material used includes any negative electrode material usable for lithium ion batteries, for example, at least one of graphite, soft carbon, hard carbon, and the like.

The main improvement of the lithium ion battery provided by the invention is that a new lithium battery separator is adopted as a lithium ion battery diaphragm, and the arrangement mode (connection mode) of the anode, the cathode, the battery diaphragm and the electrolyte can be the same as the prior art, so that the technical personnel in the field can know that the description is omitted.

The preparation method of the lithium ion battery provided by the invention comprises the steps of sequentially laminating or winding the positive electrode, the diaphragm and the negative electrode into a pole core, then injecting electrolyte into the pole core and sealing the pole core, wherein the diaphragm is the lithium battery separator.

The materials or compositions of the anode, the cathode and the electrolyte are as described above, and are not described herein again.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples, the physicochemical parameters of the starting materials were as follows:

LiAlSi₂O₆by Al (ClO)₄)₃,Si(OC₂H₅)₄,C₂H₅Strongly dispersing OH, LiOH and the like into glue, carrying out hydrothermal reaction at 120 ℃ to form gel, drying, grinding, tabletting and carrying out solid phase reaction at high temperature to obtain nano inorganic powder; (

Li₂FeSiO₄Through CH₃COOLi·2H₂O、C₆H₅FeO₇·5H₂O、(C₂H₅O)₄Si、C₆H₈O₇·H₂Dissolving O at 80 deg.C, stirring, refluxing to obtain gel, dryingGrinding and tabletting, and carrying out solid phase reaction at high temperature to obtain powder.

Polyvinylidene fluoride (PVDF), the appearance is semitransparent or white powder or granule;

alumina, white powder in appearance;

dimethylacetamide (DMAC), a colorless transparent liquid, low toxicity, combustibility and capability of being mixed with organic solvents such as water, alcohol, ether, ester, benzene, chloroform and aromatic compounds at will.

The above starting materials are either commercially available publicly or prepared by prior art methods.

In the following examples and comparative examples, the performance parameters were determined as follows:

(1) thermal shrinkage test of separator: taking a diaphragm with a complete membrane surface and no abnormal appearance, cutting the diaphragm into squares of 100 x 100mm, marking the periphery, putting the diaphragm into an oven, baking the diaphragm for 2 hours at the temperature of 120 ℃, taking out the diaphragm, and measuring the length change of the marks in the MD/TD direction of the baked diaphragm.

(2) And (3) testing the interface bonding of the diaphragm: a diaphragm with a complete film surface and no abnormal appearance is taken, a sample with the width of 25mm and the length of 100mm is punched, two punched diaphragm samples are taken and stacked together, hot pressing is carried out on a hot press under the conditions of the pressure of 1MPa, the temperature of 100 ℃ and the speed of 100mm/min, and the tensile force (unit is N) of the two diaphragms bonded together is tested by a tensile machine, wherein the bonding force is 0.025 (unit is N/m).

(3) Testing the wetting property of the membrane: taking a diaphragm with a complete film surface and no abnormal appearance, cutting the diaphragm into a square with the size of 100 x 100mm, flatly fixing the periphery of the diaphragm, suspending the center of the diaphragm, taking 2 mu l of electrolyte liquid drop in the center of the diaphragm, recording the extending distance A of the liquid drop on the diaphragm along the MD/TD direction, recording the extending distance B of the liquid drop on the diaphragm along the MD/TD direction after 5min, and recording the wetting distance (B-A)/2).

(4) Testing the ionic conductivity of the diaphragm: cutting 4 pieces of diameterThe round diaphragm sample is placed in electrolyte and sealed and soaked for 1 h. Sequentially putting 4 diaphragm samples into a testing dieThe measurements were carried out using an electrochemical workstation, and the resistances R1, R2, R3, R4 were read. Calculating the surface resistance: and (3) drawing by taking the layer number as an abscissa and taking the resistance values corresponding to different layer numbers as an ordinate, and solving the slope A of the curve, wherein the surface resistance value R of the sample is A.S, wherein S is the area of the effective electrode to be tested, the thickness d of the diaphragm is measured, and the ionic conductivity of the diaphragm is d/R.

(5) Testing the internal resistance of the lithium ion battery: the method for measuring the internal resistance of the battery in the alternating current voltage drop is characterized in that the battery is actually equivalent to an active resistor, so that a fixed frequency and a fixed current (currently, a 1KHZ frequency and a small current of 50mA are generally used) are applied to the battery, then the voltage of the battery is sampled, and the internal resistance of the battery is calculated through an operational amplifier circuit after a series of processing such as rectification, filtering and the like.

(6) And (3) testing the cycle performance of the lithium ion battery: charging the lithium ion battery at 0.5C rate and discharging at 0.5C rate at room temperature, sequentially performing 500 cycles, and calculating the capacity retention rate by using a formula; capacity retention rate (capacity of battery after 500 cycles/room temperature capacity of battery before cycles) × 100%.

Example 1

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is brought into contactThe composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the diaphragm of the batch is marked as A.

Example 2

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), LiAlSi coated with composite slurry on both sides of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆On the particle layer 2, a three-layer coating is obtainedThe lithium ion battery separator (as shown in fig. 3) has a thickness of 16 μm and the single-side functional layer 4 has a thickness of 2 μm, and the batch of separators is marked as B.

Example 3

1. 0.7kg of polyvinylidene fluoride is added into 6.3kg of DMAC solution and mechanically stirred until the polyvinylidene fluoride is completely dissolved, so that transparent colloidal PVDF solution is obtained.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method is that a transparent colloidal PVDF solution is pumped to a gravure roll by a pump, then the gravure roll rotates, the material is carried to the gravure roll, and then the material is mixed with LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the transparent colloidal PVDF solution is coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), LiAlSi coated with transparent colloidal PVDF solution on both sides of the base film body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a three-layer coated lithium ion battery diaphragm (shown in figure 3) on the granular layer 2, wherein the thickness of the lithium ion battery diaphragm is 16 mu m, the thickness of the single-side functional layer 4 is 2 mu m, and the batch of diaphragms are marked as C.

Comparative examples 1 to 1

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film asThe base film body 1, the surface 11 of which was modified by a corona pretreatment with a power of 0.5kW, was passed through a film containing LiAlSi at a speed of 5m/min₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as D1.

Comparative examples 1 to 2

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 1.5kW, and then passing the base film at the speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. Adopts a gravure roller coating mode(the specific method for coating by adopting a gravure roller mode comprises the steps of pumping the composite slurry onto a gravure roller through a pump, then rotating the gravure roller, carrying the material onto the gravure roller, and then mixing the material with LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as D2.

Comparative examples 1 to 3

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 3.5kW, and then passing the base film at the speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆On the particle layer 2, coatingThe cloth speed is 30m/min, the cloth is dried by a three-stage oven after being washed by water, the temperature of each stage of oven is respectively 50 ℃, 60 ℃ and 55 ℃, and the functional layer 4 is formed on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as D3.

Comparative examples 1 to 4

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with power of 4kW, and then passing the base film at a speed of 5m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as D4.

Comparative example 2-1

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 1m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as E1.

Comparative examples 2 to 2

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, and modifying the surface 11 of the base film through corona pretreatment with the power of 2.5kWThen passing through a reactor containing LiAlSi at a speed of 3m/min₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as E2.

Comparative examples 2 to 3

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 8m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The coating method adopts a gravure roll coating method (the specific method for coating by adopting a gravure roll method is that the composite slurry is passed throughPumping the material to a gravure roller by a pump, then rotating the gravure roller, carrying the material to the gravure roller, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆Coating on the particle layer 2 at a speed of 30m/min, drying by using a three-stage oven after rinsing, wherein the temperatures of the three-stage oven are respectively 50 ℃, 60 ℃ and 55 ℃, and forming the functional layer 4 on the LiAlSi of the modified base film 3 after drying₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as E3.

Comparative examples 2 to 4

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12um PE film as a base film main body 1, modifying the surface 11 of the base film by corona pretreatment with the power of 2.5kW, and then passing the base film at the speed of 11m/min through a film containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded in the modified surface 11 of the base film body 1 to form LiAlSi₂O₆A particle layer 2 and a modified base film 3 were obtained.

3. The gravure roll coating method (the specific method for coating by adopting the gravure roll method comprises the steps of pumping the composite slurry onto a gravure roll by a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi of the modified base film 3₂O₆The particle layer 2 is contacted, and the composite slurry can be coated on the LiAlSi of the modified basement membrane 3₂O₆Particle layer 2), the composite paste is coated on LiAlSi of one side of the base film main body 1₂O₆On the granular layer 2, the coating speed is 30m/min, and after the water is passed through, the water is dried by adopting three-stage drying ovensThe temperatures are 50 ℃, 60 ℃ and 55 ℃, respectively, and after drying, the functional layer 4 is formed on the LiAlSi of the modified base film 3₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm (shown in figure 2) on the particle layer 2, wherein the thickness of the lithium ion battery diaphragm is 14 microns, the thickness of the functional layer 4 is 2 microns, and the batch of diaphragms are marked as E4.

Comparative example 3-1

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. A gravure roll coating mode is adopted (the specific method for coating by adopting the gravure roll mode is that composite slurry is pumped onto a gravure roll through a pump, then the gravure roll rotates, the material is carried onto the gravure roll and then contacts with a 12-micron PE base film, so that the composite slurry can be coated onto the PE base film), the composite slurry is coated onto one surface of the PE base film, the coating speed is 30m/min, after water is passed through, a three-stage oven is adopted for drying, the temperature of each stage of oven is respectively 50 ℃, 60 ℃ and 55 ℃, a functional layer is formed on the PE base film after drying, and then the double-layer coated lithium ion battery diaphragm can be obtained, the thickness of the lithium ion battery diaphragm is 14 mu m, the thickness of the functional layer is 2 mu m, and the batch of diaphragms are marked as F1.

Comparative examples 3 to 2

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking a 12-micron PE base film, carrying out corona pretreatment with the power of 2.5kW to modify the surface of the PE base film, adopting a gravure roll coating mode (the specific method for coating by adopting a gravure roll mode is that composite slurry is pumped onto a gravure roll by a pump, then the gravure roll rotates, the material is carried onto the gravure roll, and then the material is contacted with the PE base film, so that the composite slurry can be coated on the modified surface of the base film, the composite slurry is coated on the modified surface of the PE base film, the coating speed is 30m/min, drying is carried out by adopting a three-stage oven after water passing, the temperatures of all stages of ovens are respectively 50 ℃, 60 ℃ and 55 ℃, and after drying, a functional layer is formed on the PE base film, so that the double-layer coated lithium ion battery diaphragm can be obtained, the thickness of the lithium ion battery diaphragm is 14 mu m, the thickness of the functional layer is 2 mu m, and the batch of diaphragms are marked as F2.

Comparative examples 3 to 3

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. Taking 12um PE basal membrane and passing through the membrane at the speed of 5m/min and containing LiAlSi₂O₆After being washed by water, the saturated aqueous solution water tank is dried by an oven to ensure that the LiAlSi is dried₂O₆Particles embedded on the surface of the PE base film to form LiAlSi₂O₆A particulate layer.

3. The dried modified film is coated by adopting a gravure roll coating mode (the specific method for coating by adopting a gravure roll mode comprises the steps of pumping the composite slurry onto a gravure roll through a pump, then rotating the gravure roll, carrying the material onto the gravure roll, and then mixing the material with the LiAlSi₂O₆Contacting the PE base film of the particle layer to coat the composite slurry on LiAlSi of the PE base film₂O₆Particle layer), coating the composite slurry on LiAlSi on one side of the PE-based film₂O₆Coating on the particle layer at a speed of 30m/min, drying with water in a three-stage oven at 50 deg.C, 60 deg.C and 55 deg.C, and drying to form the functional layer on LiAlSi of the PE-based film₂O₆And (3) obtaining a double-layer coated lithium ion battery diaphragm on the particle layer, wherein the thickness of the lithium ion battery diaphragm is 14 micrometers, the thickness of the functional layer is 2 micrometers, and the diaphragm is marked as F3.

Comparative example 4

1. And (2) taking 0.7kg of polyvinylidene fluoride to 6.3kg of DMAC solution, mechanically stirring until the polyvinylidene fluoride is completely dissolved to obtain a transparent colloidal solution a, taking 0.3kg of alumina powder to 2.7kg of DMAC solution, mechanically stirring until the alumina powder is completely dispersed to obtain a solution b, fully stirring a and b, and uniformly stirring to obtain the composite slurry.

2. The method comprises the steps of adopting a gravure roll coating mode (the specific method for coating by adopting a gravure roll mode comprises the steps of pumping composite slurry onto a gravure roll through a pump, rotating the gravure roll, carrying a material onto the gravure roll, then contacting the material with a 12-micron PE base film to coat the composite slurry onto the PE base film), coating the composite slurry onto the two surfaces of the PE base film at a coating speed of 30m/min, drying by adopting three-stage drying ovens at temperatures of 50 ℃, 60 ℃ and 55 ℃ respectively, forming a functional layer on the PE base film after drying, and obtaining the double-layer coated lithium ion battery diaphragm, wherein the thickness of the lithium ion battery diaphragm is 16 microns, the thickness of the single-side functional layer is 2 microns, and marking the batch of diaphragms as G1.

Comparative example 5

1. 0.7kg of polyvinylidene fluoride is added into 6.3kg of DMAC solution and mechanically stirred until the polyvinylidene fluoride is completely dissolved, so that transparent colloidal PVDF solution is obtained.

2. A gravure roll coating mode is adopted (the specific method for coating by adopting a gravure roll mode is that a colloidal PVDF solution is pumped onto a gravure roll by a pump, then the gravure roll rotates, the material is carried onto the gravure roll and then contacts with a 12-micron PE base film, so that the colloidal PVDF solution can be coated onto the PE base film), colloidal PVDF slurry is coated onto the two surfaces of the PE base film, the coating speed is 30m/min, three-stage drying ovens are adopted for drying, the temperatures of the drying ovens at all stages are respectively 50 ℃, 60 ℃ and 55 ℃, a functional layer is formed on the PE base film after drying, and a double-layer coated lithium ion battery diaphragm can be obtained, wherein the thickness of the lithium ion battery diaphragm is 16 mu m, the thickness of a single-side functional layer is 2 mu m, and the batch of diaphragms are marked as H.

The battery is manufactured by adopting a conventional battery preparation method (comprising the steps of sequentially laminating or winding a positive electrode, a diaphragm and a negative electrode into a pole core, injecting electrolyte into the pole core, sealing, standing, forming, detecting and the like) known by a person skilled in the art, and the batteries with A, B, C, D1-D4, E1-E4, F1-F3 and G, H batch diaphragms are tracked and marked.

The separators of examples 1 to 3, comparative examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-3, 4 and 5 were tested according to the above-mentioned performance parameter measurement method, and the results are reported in Table 1.

From A, B, C, D1-D4, E1-E4, F1-F3, G, H batteries of diaphragm batch, 5 batteries (marked respectively as A.1-A.5, B.1-B.5, C.1-C.5, D1.1-D1.5, D2.1-D2.5, D3.1-D3.5, D4.1-D4.5, E1.1-E1.5, E2.1-E2.5, E3.1-E3.5, E4.1-E4.5, F1.1-F1.5, F2.1-F2.5, F3.1-F3.5, G.1-G.5, H.1-H.5) were selected for each batch, and internal resistance and cycle performance tests were performed, and the results were recorded as in Table 2.

TABLE 1 testing of separator properties

TABLE 2 Battery Performance test corresponding to separator

With reference to tables 1 and 2, it can be seen from the comparison among examples 1, 2 and 3 and comparative examples 3-1 and 4 and 5 that the thermal shrinkage rate is greatly reduced after the functional layer is coated, the excellent thermal stability and adhesion performance are exhibited, the position of the composite membrane and the pole piece is more stable, and the safety performance of the corresponding battery is greatly improved.

By combining the tables 1 and 2, as can be seen from the sequential comparison of the examples 1, 2 and 3 with the comparative examples 3-1, 4 and 5, the wettability of the modified base film provided by the invention is obviously improved, the ionic conductivity is greatly improved, the internal resistance of the corresponding battery is greatly reduced, and the cycle performance is obviously improved.

Furthermore, as can be seen from examples 1 and comparative examples 1-1 to 1-4 and 3-1 to 3-3, the base film body after corona pretreatment but not passing through the saturated aqueous solution water tank containing the lithium ion conducting compound resulted in the increase of the TD wetting distance, MD wetting distance, and ionic conductivity of the separator by 0.13x10, respectively, by 0.7cm and 0.7 x10 cm^-3S/cm (compare comparative examples 3-1 and 3-2); the base film body is not subjected to corona pretreatment, but passes through a saturated aqueous solution water tank containing a lithium ion conducting compound, so that the TD wetting distance, the MD wetting distance and the ionic conductivity of the diaphragm are increased by 0.1cm, 0.2cm and 0.22x10 respectively^-3S/cm (compare comparative examples 3-1 and 3-3); the base film main body is subjected to corona pretreatment and passes through a saturated aqueous solution water tank containing a lithium ion conducting compound, so that the TD infiltration distance of the diaphragm is increased by 1.9cm, the MD infiltration distance is increased by 2.2cm, and the ionic conductivity is increased by 2.73x10^-3S/cm (comparative example 1 and comparative example 3-1). Therefore, the base film main body is subjected to corona pretreatment and passes through a saturated aqueous solution water tank containing a lithium ion conducting compound, so that the TD wetting distance of the diaphragm is increased by 0.9cm (namely 0.7cm +0.2cm), the MD wetting distance is increased by 0.9cm (namely 0.7cm +0.2cm), and the ionic conductivity is increased by 0.69x10^-3S/cm (i.e. 0.18x 10)^-3S/cm+0.51x10^-3S/cm). However, as compared with example 1, it is found that the TD wetting distance increased by 0.9cm is far shorter than the actual increase by 1.9cm, the MD wetting distance increased by 0.9cm is far shorter than the actual increase by 2.2cm, and the ionic conductivity increased by 0.69x10^-3S/cm far less than the actually increased 2.73x10^-3S/cm. This shows that the present invention produces a synergistic effect on the high ionic conductivity and high wettability of the separator by combining the corona pretreatment of the base film main body with the water bath of a saturated aqueous solution containing a lithium ion conducting compound.

The impregnation distance and the ionic conductivity of the diaphragm can be increased to different degrees by carrying out corona pretreatment on the base film main body at different powers and passing through a saturated aqueous solution water tank containing a lithium ion conducting compound, the optimal power of the corona is 1.5-3.5 kW, and the wettability and the ionic conductivity are increased less than expected by excessively high and low powers (comparative example 1 and comparative examples 1-4). The base film main body is subjected to corona pretreatment and passes through a saturated aqueous solution water tank containing a lithium ion conducting compound at different speeds, so that the infiltration distance and the ionic conductivity of the diaphragm are increased to different degrees, and the optimal speed of the diaphragm passing through the water tank is 3-8 m/min (comparative example 1 and comparative examples 2-1-2-4).

Different corona powers have influence on subsequent coating effect, the corona power is too low (less than 1.5kW), the surface modification of the base film is not obvious, and LiAlSi cannot be well enabled₂O₆Particles embedded on the surface of the PE base film to form LiAlSi₂O₆And the particle layer and the corona power is too high (more than 3.5kW), so that the base film is damaged, the subsequent coating is leaked, the performance of the coating film is influenced, and the test data is even not compared with that of comparative examples 1-4 and 3-1. Meanwhile, the speed of the water tank also influences the performance of the final film, the speed is too high, the time of the water tank passing through the saturated aqueous solution containing the lithium ion-conducting compound is not enough, and the LiAlSi₂O₆Less grain embedding, too slow speed, LiAlSi₂O₆The embedded layer of the particles is thicker and has a little influence on the ion conductivity of the coating film.

Therefore, the diaphragm of the invention has excellent physical and chemical properties, thermal properties and electrochemical properties, and has extremely high industrial utilization value.

The above matters related to the common general knowledge are not described in detail and can be understood by those skilled in the art.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.