CN214099815U - Lithium battery diaphragm with high infiltration characteristic - Google Patents

Lithium battery diaphragm with high infiltration characteristic Download PDF

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CN214099815U
CN214099815U CN202022455508.4U CN202022455508U CN214099815U CN 214099815 U CN214099815 U CN 214099815U CN 202022455508 U CN202022455508 U CN 202022455508U CN 214099815 U CN214099815 U CN 214099815U
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porous
separator
diaphragm
lithium battery
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白麟
白耀宗
高飞飞
高坡
王连广
孙婧
李子阳
刘杲珺
陈淳
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Sinoma Lithium Film Co Ltd
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Sinoma Lithium Film Co Ltd
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Abstract

The patent of the utility model provides a lithium battery diaphragm of high infiltration characteristic, include: a polyolefin substrate having a porous structure; and including non-conductive particles and adhesiveA porous active layer of a binder polymer mixture, the porous active coating layer being coated onto at least one side of the polyolefin porous substrate, wherein a wetting contact angle of water droplets on the porous active layer is 80 ° or less, and a surface free energy of the porous active coating layer is 1mJ/m2The separator has a peel strength of 10N/m or more, has a shrinkage of 20% or less in both a Machine Direction (MD) and a Transverse Direction (TD) after being left in an environment of 130 ℃ for one hour, and has a ratio of the shrinkage in the Machine Direction (MD) to the shrinkage in the Transverse Direction (TD) of more than 1. The utility model discloses simple process is reasonable, and the diaphragm that makes has stronger infiltration characteristic, higher security performance and excellent electrochemistry stability.

Description

Lithium battery diaphragm with high infiltration characteristic
Technical Field
The utility model belongs to the technical field of the lithium cell diaphragm, concretely relates to height is soaked, high heat-resisting and high chemical stability diaphragm for lithium cell.
Background
With the development of new energy technology, lithium ion batteries are applied to digital products, electric vehicles and energy storage devices due to their high energy density, long service life and high safety. The lithium battery mainly comprises four parts, namely a positive electrode, electrolyte, a diaphragm and a negative electrode, wherein the quality of the performance of the diaphragm influences the important performances of the lithium battery, such as capacity, internal resistance, circulation and the like. At present, most of commercial diaphragms are polyolefin diaphragms, and the wetting effect of water and electrolyte is poor due to the fact that the materials are mainly nonpolar, so that the liquid absorption and liquid retention performance of the diaphragms are seriously influenced, and further the conduction of lithium ions in batteries is influenced. Therefore, it is very important to improve the wettability of the separator with respect to the electrolyte.
At present, most of main methods for improving the surface wettability of the diaphragm are plasma treatment and grafting of functional groups with hydrophilic properties, but the methods have high processing difficulty and expensive equipment and have certain influence on the microstructure of the diaphragm, so that the method is difficult to be applied industrially in batches.
SUMMERY OF THE UTILITY MODEL
In view of above-mentioned technical defect, the utility model provides a lithium battery diaphragm of high infiltration characteristic, the diaphragm of preparing have high infiltration, high heat-resisting and characteristics such as high chemical stability to promote market competition.
In order to solve the technical problem, the utility model provides a lithium battery diaphragm of characteristic is soaked to height mainly includes: (a) a polyolefin porous substrate having a porous structure (b) a porous active coating layer comprising a mixture of non-conductive particles and a binder polymer, the porous active coating layer being applied to at least one side of the polyolefin porous substrate, wherein a wetting contact angle of water droplets on the porous active layer is 80 ° or less, and a surface free energy of the porous active coating layer is 1mJ/m2The separator has a peel strength of 10N/m or more, has a shrinkage of 20% or less in both a Machine Direction (MD) and a Transverse Direction (TD) after being left in an environment of 130 ℃ for one hour, and has a ratio of the shrinkage in the Machine Direction (MD) to the shrinkage in the Transverse Direction (TD) of more than 1.
In the lithium battery separator with high infiltration characteristics of the present invention, the polyolefin porous substrate is a Polyethylene (PE) or polypropylene (PP) single layer, or a mixed layer of Polyethylene (PE) and polypropylene (PP), or a multilayer of Polyethylene (PE) and polypropylene (PP), and from the viewpoint of film forming properties, polyethylene and a copolymer are preferred, and polyethylene can be obtained by one-step polymerization or multistep polymerization.
In the lithium battery separator with high wetting property of the invention, the molecular weight of the polyethylene is 50-400 ten thousand, preferably 60-300 ten thousand, particularly preferably 80-300 ten thousand, and the particle size of the polyethylene is less than or equal to 100 μm.
The production process of the polyolefin diaphragm can adopt dry-method unidirectional stretching, bidirectional synchronous or asynchronous stretching and wet-method bidirectional synchronous or asynchronous stretching, and preferably adopts a wet-method bidirectional synchronous stretching method for preparation.
The thickness of the polyolefin separator is 1-30 μm, preferably 5-20 μm, and the porosity of the separator is 10-70%, preferably 20-60%.
In the high wettability separator of the present invention, the non-conductive particles are not particularly limited as long as the electrochemical properties are stable. For the above reasons, the inorganic particles having a dielectric constant of 5 or more and having lithium ion transferability are satisfied. Examples thereof include silicon dioxide (SiO)2) Alumina (Al)2O3) Boehmite (ALOOH), magnesia (MgO), zirconia (ZrO)2) Titanium oxide (TiO)2) Oxide particles such as calcium oxide (CaO), nitride particles such as aluminum nitride (AlN) and Boron Nitride (BN), and barium sulfate (BaSO)4) And poorly soluble ion crystal particles such as calcium fluoride (CaF2) and barium fluoride (BaF 2). The nonconductive particles may be selected from one of the above, or two or more of them may be selected in any ratio. Among these particles, oxide particles are preferable in view of stability in the electrolytic solution and potential. The non-conductive particles need to have a high thermal decomposition temperature (decomposition temperature higher than 500 ℃) and low water absorption, and are preferably alumina, boehmite, magnesia, and silica, and particularly preferably alumina, boehmite, and silica.
In the separator with high wettability of the present invention, the shape of the non-conductive particles is not particularly limited, and examples thereof include a plate shape, a flake shape, a needle shape, a columnar shape, a spherical shape, a block shape, a polyhedral shape, a block shape, and the like, and a plurality of inorganic fillers having the above-mentioned shapes may be used in combination. From the viewpoint of improving the permeability, a plate shape, a block shape, a polyhedral shape, and a columnar shape including a plurality of faces are preferable.
In the high infiltration characteristic separator of the present invention, when the dimension of the non-conductive particles in 3 directions is set to be the length L, the thickness t, and the width b, the length L is 0.01 to 25 μm, the ratio (b/t) of the width b to the thickness t is 2.0 to 120, and the ratio (L/b) of the length L to the width b is 1 to 50.
In the high wettability separator of the present invention, the dimensions of the non-conductive particles in 3 directions can be determined by the following method. Observing by using a scanning electron microscope at the magnification of 5000-.
In the separator with high wetting property of the present invention, the width-to-thickness ratio (b/t) of the non-conductive particles is 2.0 to 120, preferably 3 to 80, and more preferably 5 to 50. b/t is in the range, the orientation among the particles is uniform, and the safety performance of the diaphragm can be effectively improved. Meanwhile, the length of the non-conductive particles is 0.01-25 μm, preferably 0.2-20 μm, more preferably 0.5-15 μm, and the length of the non-conductive particles in the range can effectively improve the permeability of lithium ions among the non-conductive particles, thereby ensuring that the lithium battery has excellent cycle performance. Generally, the aspect ratio (L/b) of the non-conductive particles is preferably 1.0 to 50, more preferably 1.0 to 20, and particularly preferably 1.0 to 10. the aspect ratio of the non-conductive particles in this range can effectively increase the surface energy, thereby improving the wetting property of the electrolyte.
The utility model discloses an among the high infiltration characteristic diaphragm, the average volume particle diameter of non-conductive particle at 0.01 ~ 20 mu m, preferred at 0.05 ~ 10 mu m, more preferred be 0.1 ~ 5 mu m, the particle diameter of non-conductive particle is in above-mentioned scope, can obtain stable thick liquids dispersed state to have higher resistant shear property in the coating process, the particle is piled up evenly in the coating process, has improved the permeability of lithium ion.
In the high infiltration characteristic diaphragm of the present invention, the specific surface area of the non-conductive particles is 100m2A ratio of less than/g, preferably 50m2Less than g, more preferably 30m2The specific surface area of the non-conductive particles is within the above range, and the surface energy of the particles can be increased, the wettability of the electrolyte in the separator can be improved, and the cycle performance of the battery can be improved. In addition, the coagulation among slurry particles can be improvedAggregation and fluidity of the slurry.
The utility model discloses an among the high infiltration characteristic diaphragm, can also contain the particle that has lithium ion transfer ability among the inorganic particle to improve the electric conductive property of lithium ion, the particle that has lithium ion transfer is selected from any one inorganic particle or the mixture of two kinds of at least inorganic particles below: lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium nitride, lithium carbonate, lithium chloride, lithium sulfide, lithium hexafluorophosphate.
The utility model discloses an among the high infiltration characteristic diaphragm, binder polymer be one or more in butadiene styrene rubber, acrylic resin, polyvinyl alcohol, polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polytetrafluoroethylene, in these matters, preferred polyvinylidene fluoride and acrylic resin, binder polymer mainly play the effect of maintaining the mechanical strength of porous membrane, keep the toughness of porous membrane to it drops from porous membrane to restrain non-conductive particle at lithium cell winding in-process.
In the separator with high wettability of the present invention, the binder polymer contains a carboxyl group and a crosslinkable group, wherein the carboxyl group can promote the adsorption of the binder to the nonconductive particles, thereby further improving the dispersibility of the nonconductive particles, and the crosslinkable group can inhibit the swelling and dissolution of the porous film in the electrolyte, so that a tough and flexible porous film can be realized.
In the separator with high infiltration property of the present invention, the binder polymer should have stable electrochemical performance, and mainly shows no other redox current peak except the electrode de/intercalation redox peak in the voltage of 1-5V.
In the high infiltration characteristic diaphragm of the present invention, the solvent used for the slurry includes water or any solvent in the organic solvent. Examples of the organic solvent include: aliphatic hydrocarbons such as cyclopropane and cyclohexane; ketones such as ethyl methyl ketone and cyclohexanone; aromatic hydrocarbons such as benzene and toluene; esters such as nitrile ethyl acetate and butyl acetate, e.g., acetonitrile and propionitrile; alcohols such as methanol, ethanol, isopropanol, and ethylene glycol; ethers such as tetrahydrofuran and ethylene glycol diethyl ether; amides such as N-methylpyrrolidone and N, N-dimethylformamide. These solvents may be used alone or in combination. Among them, water is preferably used as a slurry to prepare a solvent.
The utility model discloses an among the high infiltration characteristic diaphragm, thick liquids can contain the viscosity control agent, through containing the viscosity control agent, can control the viscosity of thick liquids at the scope of expectation to the dispersion effect and the coating effect of thick liquids have been improved.
As the viscosity modifier, polysaccharides are preferable. Examples thereof include natural polymer compounds and cellulose semi-synthetic polymer compounds. The viscosity modifier may be used alone, or 2 or more of them may be used in combination in any ratio. From the viewpoint of improving the dispersibility of the nonconductive particles, a cellulose semisynthetic compound is preferably used.
The etherification degree of the cellulose semi-synthetic polymer compound is preferably 0.5 or more, more preferably 0.7 or more, preferably 1.2 or less, and more preferably 1.0 or less. The etherification degree is a degree of substitution in which hydroxyl groups (3) per anhydroglucose unit in cellulose are substituted with a substituent such as a carboxymethyl group. The etherification degree is in the range of 0 to 3, and the etherification degree in the above range is considered in consideration of dispersibility of the non-conductive particles in water.
The average degree of polymerization of the cellulose semi-synthetic polymer compound is preferably 500 or more, more preferably 1000 or more, preferably 2500 or less, more preferably 2000 or less, and particularly preferably 1500 or less. The average polymerization degree of the viscosity modifier affects the fluidity of the slurry and thus the stability of the slurry and the coating effect, and the stability of the slurry and the uniformity of a coating layer in coating are improved by controlling the average polymerization degree of the viscosity modifier within the above range.
In the high infiltration characteristic diaphragm of the utility model, the slurry can contain other optional components besides the components. Examples thereof include a dispersant, a wetting agent, and an electrolyte dispersion inhibitor. The above-mentioned components are not particularly limited as long as they do not adversely affect the lithium battery, and the above-mentioned arbitrary components may be 1 kind, or 2 or more kinds.
The dispersing agent is mainly an anionic compound, a cationic compound, a nonionic compound and a polymer compound.
The wetting agent is mainly alkyl surfactant, silicon surfactant, fluorine surfactant and the like. The surface tension of the slurry on the porous membrane can be reduced and the wetting or spreading effect of the slurry can be improved by adding the surfactant, and the amount of the wetting agent is preferably less than 5% of the weight of the prepared slurry.
In the slurry of the present invention, the pH of the slurry is preferably 6 to 12, the viscosity of the slurry is preferably 5 to 1000mpa · s in consideration of the flow property of the fluid during the coating process, the volume average particle diameter of the slurry is preferably 0.1 to 5 μm, and the viscosity is measured by a Brookfield viscometer of 25 ℃ at a rotation speed of 40rpm and the particle diameter is measured by a Bettersize distribution instrument.
In the separator with high wettability of the present invention, the coating method of the slurry is not limited, and the coating method, the dipping method, or the like may be selected for coating. Examples of the coating method include a doctor blade method, a reverse roll method, a direct roll method, a gravure roll method, an extrusion method, a spray coating method, a spot coating method, and the like. The coating is preferably performed by the gravure roll method in view of the uniformity of the thickness of the porous film.
In the high wettability separator of the present invention, the drying method of the porous membrane is not limited, and drying methods such as hot air, low humidity air, vacuum drying, spray drying, and freeze drying can be selected and utilized.
In the high infiltration characteristic membrane of the present invention, the wetting contact angle of the membrane to water drops is below 80 °. Under the conditions that the temperature is 25 ℃ and the relative humidity is less than 60%, the model TBU100 is used as a contact angle measuring instrument (manufactured by Dataphysics of Germany), water drops are slowly dropped on the surface of the film, after 60 seconds of dropping, the wetting contact angle of the water drops is measured, the contact angle is measured at three points of the film, and the average value of the three points can be used as the contact angle.
In the diaphragm with high infiltration characteristic of the utility model, the surface free energy of the diaphragm and the water drop is 1mJ/m2The above. The free energy of the diaphragm surface is calculated by mainly using Young's equation and Owens equation, and the selected liquid satisfies the following conditions of (1) delta of two liquidsL PL DThe values cannot be close, and the larger the difference between the two values, the better; (2) the two liquids must have different polarities, i.e. one liquid must be selected from the polar liquid and the non-polar liquid (3) the test liquid cannot dissolve, swell, deform, etc. the surface of the solid; in combination with the above conditions, the liquid 1 is preferably water, formamide, glycerin, or the like, and the liquid 2 is preferably benzene, diiodomethane, n-hexadecane, α -bromonaphthalene, or the like.
Advantageous effects
The utility model discloses an among the high infiltration characteristic diaphragm, the peel strength of diaphragm is more than 10N/m, consequently porous coating have good adhesive property to the problem that the diaphragm peeled off in porous coating in battery assembly and use has been guaranteed.
The utility model discloses a high infiltration characteristic diaphragm in, the diaphragm place after 130 ℃ of environment one hour, its shrinkage factor in vertical (MD) and horizontal (TD) is all below 20%, and the ratio of the shrinkage factor in vertical (MD) and horizontal (TD) is greater than 1.
The thermal shrinkage measurement method of the diaphragm comprises the following steps:
coating a diaphragm, taking a block diaphragm of 15cm by 15cm, drawing two mutually perpendicular line segments (generally 10cm by 10cm) according to the longitudinal direction and the transverse direction marked by the following figure, and measuring the longitudinal length and the transverse length of a sample by using a straight steel ruler (or a projector) respectively; the samples were placed flat in two sheets of a4 paper and subsequently placed in an oven at 130 ℃ for 1 h; after heating, taking out the samples, after the temperature is returned to room temperature, measuring the lengths of the longitudinal mark and the transverse mark again, respectively calculating the shrinkage rate according to the following formula, and finally taking the average value of the samples as the shrinkage rate.
MD direction heat shrinkage (%) (length in MD direction before heating-length in MD direction after heating)/length in MD direction before heating × (100)
TD direction heat shrinkage (%) (length in TD direction before heating-length in TD direction after heating)/length in MD direction before heating × (100)
Drawings
FIG. 1 is a graph showing the effect of wetting the contact angle with ultrapure water in accordance with comparative example 1 of the present invention;
FIG. 2 is a diagram showing the effect of wetting the balance contact angle of ultrapure water by using the high wettability membrane of the present invention in the embodiment 1;
FIG. 3 is a graph showing a distribution of particle diameters of a powdery raw material
FIG. 4 is the schematic diagram of the lithium battery diaphragm with high infiltration characteristic of the present invention
Detailed Description
The above-mentioned contents of the present invention are further described in detail by the following embodiments, but it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments, and all the technologies realized based on the above-mentioned contents of the present invention belong to the scope of the present invention.
Example 1 is specifically described.
Adding 10g of polyacrylic acid into 100g of deionized water, stirring and mixing for 10min, adding 100g of alumina particles into the solution, wherein the L/b of the alumina particles is 1.0, the b/t is 2.0, the L is 0.01 mu m, the particle size distribution is shown in a figure 3, the measured average particle size is 0.8 mu m, stirring for 30min, adding 30g of viscosity regulator, continuously stirring and grinding for 30min, adding 40g of acrylate emulsion adhesive and 5g of wetting agent fatty alcohol polyoxyethylene ether after the solution is uniformly mixed, then mixing with water to enable the concentration of solid components to reach 40% of the total mass of the slurry, stirring and mixing for 30min, thereby obtaining the aqueous mixed slurry. Coating the aqueous mixed slurry on one side of a 9 mu mPE base film to form an aqueous coating, and baking the aqueous mixed slurry for 5min in a 60 ℃ baking oven to obtain a product, wherein the thickness of the aqueous coating is 3 mu m, and the surface density is 4.58g/m2
Example 2.
Adding 10g of polyacrylic acid into 100g of deionized water, stirring and mixing for 10min, adding 100g of boehmite powder into the solution, wherein the boehmite particles have an L/b of 2.0, a b/t of 50, an L of 1.0 μm and a volume average particle size of 1.0 μm, stirring for 30min, adding 30g of viscosity regulator, and then stirringStirring and grinding are continuously carried out for 30min, after the solution is uniformly mixed, 40g of acrylic ester emulsion and 5g of polyoxyethylene alkyl ether sulfate are added, then water is mixed to enable the concentration of solid components to reach 40% of the total mass of the slurry, and stirring and mixing are carried out for 30min, so that the water-based mixed slurry is obtained. Coating the aqueous mixed slurry on one side of a 9 mu mPE base film to form an aqueous coating, and baking the aqueous mixed slurry for 5min in a 60 ℃ baking oven to obtain a product, wherein the thickness of the aqueous coating is 3 mu m, and the surface density is 4.52g/m2
Example 3.
Adding 10g of polyethylene glycol into 100g of deionized water, stirring and mixing for 10min, adding 100g of silicon dioxide particles into the solution, wherein the L/b of the silicon dioxide particles is 50.0, the b/t is 120, the L is 25 mu m, the volume average particle size is 2.0 mu m, stirring for 30min, adding 30g of viscosity regulator, continuously stirring and grinding for 30min, adding 40g of acrylate emulsion and 5g of polyoxyethylene alkyl ether sulfate as a wetting agent after the solution is uniformly mixed, then mixing with water to enable the concentration of solid components to reach 40% of the total mass of the slurry, and stirring and mixing for 30min to obtain the aqueous mixed slurry. Coating the aqueous mixed slurry on one side of a 9 mu mPE base film to form an aqueous coating, and baking the aqueous mixed slurry for 5min in a 60 ℃ baking oven to obtain a product, wherein the thickness of the aqueous coating is 3 mu m, and the surface density is 4.55g/m2
In the above examples, the aqueous mixed slurry had a pH of 6 to 12, a viscosity of 5 to 1000 mPa.s, and a volume-average particle diameter of 0.1 to 5 μm; wherein the above viscosity is measured with a Brookfield viscometer at 25 ℃ and a rotation speed of 40rpm, and the particle size is measured with a Bettersize distribution instrument.
Comparative example 1.
Adding 10g of triethanolamine into 100g of deionized water, stirring and mixing for 10min, adding 100g of boehmite powder into the solution, wherein the L/b of alumina particles is 100, the b/t is 150, the L is 20 mu m, the volume average particle size is 25.0 mu m, stirring for 30min, adding 30g of viscosity regulator, continuously stirring and grinding for 30min, adding 40g of acrylate emulsion adhesive and 5g of wetting agent alkyl trimethyl ammonium salt after the solution is uniformly mixed, then mixing with water to ensure that the concentration of solid components reaches 40% of the total mass of the slurry, stirring, mixing and mixingFor 30min, thereby obtaining an aqueous mixed slurry. Coating the aqueous mixed slurry on one side of a 9 mu mPE base film to form an aqueous coating, and baking the aqueous mixed slurry for 5min in a 60 ℃ baking oven to obtain a product, wherein the thickness of the aqueous coating is 3 mu m, and the surface density is 4.52g/m2
Comparative example 2.
Adding 12g of polymethacrylic acid amine into 100g of deionized water, stirring and mixing for 10min, adding 100g of boehmite powder into the solution, wherein the L/b of boehmite particles is 1.2, the b/t is 1, the L is 1.0 mu m, the volume average particle size is 2.50nm, stirring for 30min, adding 30g of viscosity regulator, continuously stirring and grinding for 30min, adding 40g of acrylate emulsion adhesive and 5g of wetting agent alkyl amine oxide after the solution is uniformly mixed, then mixing with water to enable the concentration of solid components to reach 40% of the total mass of the slurry, stirring and mixing for 30min, and thus obtaining the aqueous mixed slurry. And coating the aqueous mixed slurry on one side of a 9-mu mPE base film to form an aqueous coating, and baking the aqueous mixed slurry for 2min in a 60-DEG C oven to obtain a product, wherein the thickness of the aqueous coating is 2 mu m, and the surface density is 4.54g/m 2.
The physical properties of the separator were measured according to the specific examples 1 to 3 and the comparative examples 1 to 2, and the results are shown in the following table two:
Figure DEST_PATH_GDA0003168227470000071
as shown in fig. 1, fig. 2 and the above table, in the specific implementation 1-3, since the interface free energy is higher, the wetting equilibrium contact angle is small, the liquid absorption and retention performance and the ionic conductivity of the separator are obviously improved, and both are higher than those of the comparative example, which indicates that the improvement of the interface surface free energy can significantly improve the wetting effect of the electrolyte on the separator.
It should be noted that, the solution of the present invention is to add non-conductive particles into the slurry of the adhesive polymer and mix them to obtain the aqueous mixed slurry, wherein the non-conductive particles can be silicon dioxide SiO2Aluminum oxide Al2O3Boehmite, magnesium oxide MgO, zirconium oxide ZrO2Titanium oxide TiO2CaO, calcium oxide; aluminum nitride AlN, boron nitride BN, barium sulfateBaSO4Calcium fluoride CaF2Barium fluoride BaF2One or more particles of (a). When the shaft diameter of the non-conductive particles is set as length L, thickness t and width b, the length L is 0.01-25 mu m, the ratio b/t of the width to the thickness t is 2.0-120, and the ratio L/b of the length L to the width b is 1-50; the dielectric constant of the non-conductive particles is more than 5, and the thermal decomposition temperature is more than 500 ℃, so that the high infiltration characteristic of the similar diaphragm can be ensured.
Still further, the non-conductive particles may further include particles having lithium ion transferring ability. The particles with lithium ion transfer capacity are 1 or more than 2 of lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium nitride, lithium carbonate, lithium chloride, lithium sulfide and lithium hexafluorophosphate. Thereby improving the conductivity of lithium ions.
The liquid absorption rate measuring method comprises the following steps:
the sample film is dried and weighed (M)0G), soaking the membrane in the electrolyte for 24h, taking out the membrane after the membrane fully absorbs the electrolyte, slightly absorbing the electrolyte on the surface of the membrane by using filter paper, and weighing (M)1And g) calculating the liquid absorption rate (u%) by using the following formula:
u%=(M1-M0)/M0×100%
method for measuring ionic conductivity:
electrochemical workstation, supply voltage: 220V +/-10 percent and the frequency of 50 +/-2 Hz; testing parameters: setting the initial level to be 0V, the high frequency to be 105Hz, the low frequency to be 1Hz, the amplitude to be 0.005V and the standing time to be 2 seconds; the connecting method of the test mold comprises the following steps: connecting four electrodes; a resistance testing mold; electrolyte solution: lithium hexafluorophosphate. And 5 samples matched with the resistance testing mold are cut out from the samples.
The test steps are as follows: putting the sample into an electrolyte with the temperature of 23 +/-2 ℃, keeping sealing and soaking for 2 hours; injecting electrolyte into a resistance testing mold, connecting the resistance testing mold with a chemical workstation, and setting testing parameters; sequentially putting 1 layer of diaphragm, testing the impedance spectrum, putting another layer of diaphragm, testing the impedance spectrum until 4 layers of diaphragm are put, measuring four impedance spectrograms, and respectively reading resistance values R1, R2, R3 and R4 of 1-4 layers of diaphragm; and (3) taking the layer number as an abscissa and the resistance value of the diaphragm as an ordinate to make a curve, calculating the slope and the linear fitting degree of the curve, and when the linear fitting degree is more than 0.99, calculating the ionic conductivity of the diaphragm according to the formula sigma-d/1000 ks, wherein: σ -ionic conductivity of the sample (Siemens/meter S/cm) d-sample thickness (. mu.m); k-the slope of the curve; s-test area of the diaphragm (cm 2).
Referring to fig. 4, a lithium battery separator with high wettability is finally prepared, which includes:
a polyolefin porous substrate 1 having a porous structure;
a porous active coating 2 comprising non-conductive particles and a binder polymer;
the porous active coating layer is coated on at least one side of the polyolefin porous substrate; the wetting contact angle of water drops on the porous active coating is below 80 DEG, and the surface free energy of the porous active coating is 1mJ/m2The separator has a peel strength of 10N/m or more, and after the separator is left in an environment at 130 ℃ for one hour, the shrinkage rates in both the machine direction MD and the transverse direction TD are 20% or less, and the ratio of the shrinkage rates in the machine direction MD to the transverse direction TD is greater than 1.

Claims (3)

1. A lithium battery separator with high wetting property is characterized by comprising:
-a polyolefin porous substrate having a porous structure;
-a porous reactive coating comprising non-conductive particles and a binder polymer;
the porous active coating layer is coated on at least one side of the polyolefin porous substrate;
the wetting contact angle of water drops on the porous active coating is below 80 DEG, and the surface free energy of the porous active coating is 1mJ/m2The separator has a peel strength of 10N/m or more, and after the separator is left in an environment at 130 ℃ for one hour, the shrinkage rates in both the machine direction MD and the transverse direction TD are 20% or less, and the ratio of the shrinkage rates in the machine direction MD to the transverse direction TD is greater than 1.
2. The lithium battery separator with high wettability as claimed in claim 1, wherein said polyolefin porous substrate is a single layer of polyethylene PE or polypropylene PP, or a multilayer of polyethylene PE and polypropylene PP.
3. The separator for a lithium battery having high wettability according to claim 1, wherein said non-conductive particles:
when the axial diameter is set as length L, thickness t and width b, the length L is 0.01-25 μm, the ratio b/t of width b and thickness t is 2.0-120, and the ratio L/b of length L and width b is 1-50;
the average volume particle size is 0.01-20 μm;
the specific surface area is 100m2The ratio of the carbon atoms to the carbon atoms is less than g.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112216929A (en) * 2020-10-29 2021-01-12 中材锂膜有限公司 Lithium battery diaphragm with high infiltration characteristic and preparation method thereof
CN114094274A (en) * 2021-10-27 2022-02-25 中材锂膜有限公司 Battery isolation membrane, preparation method thereof and secondary battery

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112216929A (en) * 2020-10-29 2021-01-12 中材锂膜有限公司 Lithium battery diaphragm with high infiltration characteristic and preparation method thereof
CN114094274A (en) * 2021-10-27 2022-02-25 中材锂膜有限公司 Battery isolation membrane, preparation method thereof and secondary battery
CN114094274B (en) * 2021-10-27 2024-03-01 中材锂膜有限公司 Battery separation film, preparation method thereof and secondary battery

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